8023145: G1: G1CollectedHeap::mark_strong_code_roots() needs to handle ParallelGCThreads=0
Reviewed-by: stefank, mgerdin
/*
* Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* questions.
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*/
#include "precompiled.hpp"
#include "code/codeCache.hpp"
#include "code/icBuffer.hpp"
#include "gc_implementation/g1/bufferingOopClosure.hpp"
#include "gc_implementation/g1/concurrentG1Refine.hpp"
#include "gc_implementation/g1/concurrentG1RefineThread.hpp"
#include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
#include "gc_implementation/g1/g1AllocRegion.inline.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/g1ErgoVerbose.hpp"
#include "gc_implementation/g1/g1EvacFailure.hpp"
#include "gc_implementation/g1/g1GCPhaseTimes.hpp"
#include "gc_implementation/g1/g1Log.hpp"
#include "gc_implementation/g1/g1MarkSweep.hpp"
#include "gc_implementation/g1/g1OopClosures.inline.hpp"
#include "gc_implementation/g1/g1RemSet.inline.hpp"
#include "gc_implementation/g1/g1YCTypes.hpp"
#include "gc_implementation/g1/heapRegion.inline.hpp"
#include "gc_implementation/g1/heapRegionRemSet.hpp"
#include "gc_implementation/g1/heapRegionSeq.inline.hpp"
#include "gc_implementation/g1/vm_operations_g1.hpp"
#include "gc_implementation/shared/gcHeapSummary.hpp"
#include "gc_implementation/shared/gcTimer.hpp"
#include "gc_implementation/shared/gcTrace.hpp"
#include "gc_implementation/shared/gcTraceTime.hpp"
#include "gc_implementation/shared/isGCActiveMark.hpp"
#include "memory/gcLocker.inline.hpp"
#include "memory/genOopClosures.inline.hpp"
#include "memory/generationSpec.hpp"
#include "memory/referenceProcessor.hpp"
#include "oops/oop.inline.hpp"
#include "oops/oop.pcgc.inline.hpp"
#include "runtime/vmThread.hpp"
size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
// turn it on so that the contents of the young list (scan-only /
// to-be-collected) are printed at "strategic" points before / during
// / after the collection --- this is useful for debugging
#define YOUNG_LIST_VERBOSE 0
// CURRENT STATUS
// This file is under construction. Search for "FIXME".
// INVARIANTS/NOTES
//
// All allocation activity covered by the G1CollectedHeap interface is
// serialized by acquiring the HeapLock. This happens in mem_allocate
// and allocate_new_tlab, which are the "entry" points to the
// allocation code from the rest of the JVM. (Note that this does not
// apply to TLAB allocation, which is not part of this interface: it
// is done by clients of this interface.)
// Notes on implementation of parallelism in different tasks.
//
// G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
// The number of GC workers is passed to heap_region_par_iterate_chunked().
// It does use run_task() which sets _n_workers in the task.
// G1ParTask executes g1_process_strong_roots() ->
// SharedHeap::process_strong_roots() which calls eventually to
// CardTableModRefBS::par_non_clean_card_iterate_work() which uses
// SequentialSubTasksDone. SharedHeap::process_strong_roots() also
// directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
//
// Local to this file.
class RefineCardTableEntryClosure: public CardTableEntryClosure {
SuspendibleThreadSet* _sts;
G1RemSet* _g1rs;
ConcurrentG1Refine* _cg1r;
bool _concurrent;
public:
RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
G1RemSet* g1rs,
ConcurrentG1Refine* cg1r) :
_sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
{}
bool do_card_ptr(jbyte* card_ptr, int worker_i) {
bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
// This path is executed by the concurrent refine or mutator threads,
// concurrently, and so we do not care if card_ptr contains references
// that point into the collection set.
assert(!oops_into_cset, "should be");
if (_concurrent && _sts->should_yield()) {
// Caller will actually yield.
return false;
}
// Otherwise, we finished successfully; return true.
return true;
}
void set_concurrent(bool b) { _concurrent = b; }
};
class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
int _calls;
G1CollectedHeap* _g1h;
CardTableModRefBS* _ctbs;
int _histo[256];
public:
ClearLoggedCardTableEntryClosure() :
_calls(0)
{
_g1h = G1CollectedHeap::heap();
_ctbs = (CardTableModRefBS*)_g1h->barrier_set();
for (int i = 0; i < 256; i++) _histo[i] = 0;
}
bool do_card_ptr(jbyte* card_ptr, int worker_i) {
if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
_calls++;
unsigned char* ujb = (unsigned char*)card_ptr;
int ind = (int)(*ujb);
_histo[ind]++;
*card_ptr = -1;
}
return true;
}
int calls() { return _calls; }
void print_histo() {
gclog_or_tty->print_cr("Card table value histogram:");
for (int i = 0; i < 256; i++) {
if (_histo[i] != 0) {
gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
}
}
}
};
class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
int _calls;
G1CollectedHeap* _g1h;
CardTableModRefBS* _ctbs;
public:
RedirtyLoggedCardTableEntryClosure() :
_calls(0)
{
_g1h = G1CollectedHeap::heap();
_ctbs = (CardTableModRefBS*)_g1h->barrier_set();
}
bool do_card_ptr(jbyte* card_ptr, int worker_i) {
if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
_calls++;
*card_ptr = 0;
}
return true;
}
int calls() { return _calls; }
};
class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
public:
bool do_card_ptr(jbyte* card_ptr, int worker_i) {
*card_ptr = CardTableModRefBS::dirty_card_val();
return true;
}
};
YoungList::YoungList(G1CollectedHeap* g1h) :
_g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
_survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
guarantee(check_list_empty(false), "just making sure...");
}
void YoungList::push_region(HeapRegion *hr) {
assert(!hr->is_young(), "should not already be young");
assert(hr->get_next_young_region() == NULL, "cause it should!");
hr->set_next_young_region(_head);
_head = hr;
_g1h->g1_policy()->set_region_eden(hr, (int) _length);
++_length;
}
void YoungList::add_survivor_region(HeapRegion* hr) {
assert(hr->is_survivor(), "should be flagged as survivor region");
assert(hr->get_next_young_region() == NULL, "cause it should!");
hr->set_next_young_region(_survivor_head);
if (_survivor_head == NULL) {
_survivor_tail = hr;
}
_survivor_head = hr;
++_survivor_length;
}
void YoungList::empty_list(HeapRegion* list) {
while (list != NULL) {
HeapRegion* next = list->get_next_young_region();
list->set_next_young_region(NULL);
list->uninstall_surv_rate_group();
list->set_not_young();
list = next;
}
}
void YoungList::empty_list() {
assert(check_list_well_formed(), "young list should be well formed");
empty_list(_head);
_head = NULL;
_length = 0;
empty_list(_survivor_head);
_survivor_head = NULL;
_survivor_tail = NULL;
_survivor_length = 0;
_last_sampled_rs_lengths = 0;
assert(check_list_empty(false), "just making sure...");
}
bool YoungList::check_list_well_formed() {
bool ret = true;
uint length = 0;
HeapRegion* curr = _head;
HeapRegion* last = NULL;
while (curr != NULL) {
if (!curr->is_young()) {
gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
"incorrectly tagged (y: %d, surv: %d)",
curr->bottom(), curr->end(),
curr->is_young(), curr->is_survivor());
ret = false;
}
++length;
last = curr;
curr = curr->get_next_young_region();
}
ret = ret && (length == _length);
if (!ret) {
gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
gclog_or_tty->print_cr("### list has %u entries, _length is %u",
length, _length);
}
return ret;
}
bool YoungList::check_list_empty(bool check_sample) {
bool ret = true;
if (_length != 0) {
gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
_length);
ret = false;
}
if (check_sample && _last_sampled_rs_lengths != 0) {
gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
ret = false;
}
if (_head != NULL) {
gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
ret = false;
}
if (!ret) {
gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
}
return ret;
}
void
YoungList::rs_length_sampling_init() {
_sampled_rs_lengths = 0;
_curr = _head;
}
bool
YoungList::rs_length_sampling_more() {
return _curr != NULL;
}
void
YoungList::rs_length_sampling_next() {
assert( _curr != NULL, "invariant" );
size_t rs_length = _curr->rem_set()->occupied();
_sampled_rs_lengths += rs_length;
// The current region may not yet have been added to the
// incremental collection set (it gets added when it is
// retired as the current allocation region).
if (_curr->in_collection_set()) {
// Update the collection set policy information for this region
_g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
}
_curr = _curr->get_next_young_region();
if (_curr == NULL) {
_last_sampled_rs_lengths = _sampled_rs_lengths;
// gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
}
}
void
YoungList::reset_auxilary_lists() {
guarantee( is_empty(), "young list should be empty" );
assert(check_list_well_formed(), "young list should be well formed");
// Add survivor regions to SurvRateGroup.
_g1h->g1_policy()->note_start_adding_survivor_regions();
_g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
int young_index_in_cset = 0;
for (HeapRegion* curr = _survivor_head;
curr != NULL;
curr = curr->get_next_young_region()) {
_g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
// The region is a non-empty survivor so let's add it to
// the incremental collection set for the next evacuation
// pause.
_g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
young_index_in_cset += 1;
}
assert((uint) young_index_in_cset == _survivor_length, "post-condition");
_g1h->g1_policy()->note_stop_adding_survivor_regions();
_head = _survivor_head;
_length = _survivor_length;
if (_survivor_head != NULL) {
assert(_survivor_tail != NULL, "cause it shouldn't be");
assert(_survivor_length > 0, "invariant");
_survivor_tail->set_next_young_region(NULL);
}
// Don't clear the survivor list handles until the start of
// the next evacuation pause - we need it in order to re-tag
// the survivor regions from this evacuation pause as 'young'
// at the start of the next.
_g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
assert(check_list_well_formed(), "young list should be well formed");
}
void YoungList::print() {
HeapRegion* lists[] = {_head, _survivor_head};
const char* names[] = {"YOUNG", "SURVIVOR"};
for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
HeapRegion *curr = lists[list];
if (curr == NULL)
gclog_or_tty->print_cr(" empty");
while (curr != NULL) {
gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
HR_FORMAT_PARAMS(curr),
curr->prev_top_at_mark_start(),
curr->next_top_at_mark_start(),
curr->age_in_surv_rate_group_cond());
curr = curr->get_next_young_region();
}
}
gclog_or_tty->print_cr("");
}
void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
{
// Claim the right to put the region on the dirty cards region list
// by installing a self pointer.
HeapRegion* next = hr->get_next_dirty_cards_region();
if (next == NULL) {
HeapRegion* res = (HeapRegion*)
Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
NULL);
if (res == NULL) {
HeapRegion* head;
do {
// Put the region to the dirty cards region list.
head = _dirty_cards_region_list;
next = (HeapRegion*)
Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
if (next == head) {
assert(hr->get_next_dirty_cards_region() == hr,
"hr->get_next_dirty_cards_region() != hr");
if (next == NULL) {
// The last region in the list points to itself.
hr->set_next_dirty_cards_region(hr);
} else {
hr->set_next_dirty_cards_region(next);
}
}
} while (next != head);
}
}
}
HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
{
HeapRegion* head;
HeapRegion* hr;
do {
head = _dirty_cards_region_list;
if (head == NULL) {
return NULL;
}
HeapRegion* new_head = head->get_next_dirty_cards_region();
if (head == new_head) {
// The last region.
new_head = NULL;
}
hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
head);
} while (hr != head);
assert(hr != NULL, "invariant");
hr->set_next_dirty_cards_region(NULL);
return hr;
}
void G1CollectedHeap::stop_conc_gc_threads() {
_cg1r->stop();
_cmThread->stop();
}
#ifdef ASSERT
// A region is added to the collection set as it is retired
// so an address p can point to a region which will be in the
// collection set but has not yet been retired. This method
// therefore is only accurate during a GC pause after all
// regions have been retired. It is used for debugging
// to check if an nmethod has references to objects that can
// be move during a partial collection. Though it can be
// inaccurate, it is sufficient for G1 because the conservative
// implementation of is_scavengable() for G1 will indicate that
// all nmethods must be scanned during a partial collection.
bool G1CollectedHeap::is_in_partial_collection(const void* p) {
HeapRegion* hr = heap_region_containing(p);
return hr != NULL && hr->in_collection_set();
}
#endif
// Returns true if the reference points to an object that
// can move in an incremental collection.
bool G1CollectedHeap::is_scavengable(const void* p) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
G1CollectorPolicy* g1p = g1h->g1_policy();
HeapRegion* hr = heap_region_containing(p);
if (hr == NULL) {
// null
assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
return false;
} else {
return !hr->isHumongous();
}
}
void G1CollectedHeap::check_ct_logs_at_safepoint() {
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
// Count the dirty cards at the start.
CountNonCleanMemRegionClosure count1(this);
ct_bs->mod_card_iterate(&count1);
int orig_count = count1.n();
// First clear the logged cards.
ClearLoggedCardTableEntryClosure clear;
dcqs.set_closure(&clear);
dcqs.apply_closure_to_all_completed_buffers();
dcqs.iterate_closure_all_threads(false);
clear.print_histo();
// Now ensure that there's no dirty cards.
CountNonCleanMemRegionClosure count2(this);
ct_bs->mod_card_iterate(&count2);
if (count2.n() != 0) {
gclog_or_tty->print_cr("Card table has %d entries; %d originally",
count2.n(), orig_count);
}
guarantee(count2.n() == 0, "Card table should be clean.");
RedirtyLoggedCardTableEntryClosure redirty;
JavaThread::dirty_card_queue_set().set_closure(&redirty);
dcqs.apply_closure_to_all_completed_buffers();
dcqs.iterate_closure_all_threads(false);
gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
clear.calls(), orig_count);
guarantee(redirty.calls() == clear.calls(),
"Or else mechanism is broken.");
CountNonCleanMemRegionClosure count3(this);
ct_bs->mod_card_iterate(&count3);
if (count3.n() != orig_count) {
gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
orig_count, count3.n());
guarantee(count3.n() >= orig_count, "Should have restored them all.");
}
JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
}
// Private class members.
G1CollectedHeap* G1CollectedHeap::_g1h;
// Private methods.
HeapRegion*
G1CollectedHeap::new_region_try_secondary_free_list() {
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
while (!_secondary_free_list.is_empty() || free_regions_coming()) {
if (!_secondary_free_list.is_empty()) {
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
"secondary_free_list has %u entries",
_secondary_free_list.length());
}
// It looks as if there are free regions available on the
// secondary_free_list. Let's move them to the free_list and try
// again to allocate from it.
append_secondary_free_list();
assert(!_free_list.is_empty(), "if the secondary_free_list was not "
"empty we should have moved at least one entry to the free_list");
HeapRegion* res = _free_list.remove_head();
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
"allocated "HR_FORMAT" from secondary_free_list",
HR_FORMAT_PARAMS(res));
}
return res;
}
// Wait here until we get notified either when (a) there are no
// more free regions coming or (b) some regions have been moved on
// the secondary_free_list.
SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
}
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
"could not allocate from secondary_free_list");
}
return NULL;
}
HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
"the only time we use this to allocate a humongous region is "
"when we are allocating a single humongous region");
HeapRegion* res;
if (G1StressConcRegionFreeing) {
if (!_secondary_free_list.is_empty()) {
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
"forced to look at the secondary_free_list");
}
res = new_region_try_secondary_free_list();
if (res != NULL) {
return res;
}
}
}
res = _free_list.remove_head_or_null();
if (res == NULL) {
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
"res == NULL, trying the secondary_free_list");
}
res = new_region_try_secondary_free_list();
}
if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
// Currently, only attempts to allocate GC alloc regions set
// do_expand to true. So, we should only reach here during a
// safepoint. If this assumption changes we might have to
// reconsider the use of _expand_heap_after_alloc_failure.
assert(SafepointSynchronize::is_at_safepoint(), "invariant");
ergo_verbose1(ErgoHeapSizing,
"attempt heap expansion",
ergo_format_reason("region allocation request failed")
ergo_format_byte("allocation request"),
word_size * HeapWordSize);
if (expand(word_size * HeapWordSize)) {
// Given that expand() succeeded in expanding the heap, and we
// always expand the heap by an amount aligned to the heap
// region size, the free list should in theory not be empty. So
// it would probably be OK to use remove_head(). But the extra
// check for NULL is unlikely to be a performance issue here (we
// just expanded the heap!) so let's just be conservative and
// use remove_head_or_null().
res = _free_list.remove_head_or_null();
} else {
_expand_heap_after_alloc_failure = false;
}
}
return res;
}
uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
size_t word_size) {
assert(isHumongous(word_size), "word_size should be humongous");
assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
uint first = G1_NULL_HRS_INDEX;
if (num_regions == 1) {
// Only one region to allocate, no need to go through the slower
// path. The caller will attempt the expansion if this fails, so
// let's not try to expand here too.
HeapRegion* hr = new_region(word_size, false /* do_expand */);
if (hr != NULL) {
first = hr->hrs_index();
} else {
first = G1_NULL_HRS_INDEX;
}
} else {
// We can't allocate humongous regions while cleanupComplete() is
// running, since some of the regions we find to be empty might not
// yet be added to the free list and it is not straightforward to
// know which list they are on so that we can remove them. Note
// that we only need to do this if we need to allocate more than
// one region to satisfy the current humongous allocation
// request. If we are only allocating one region we use the common
// region allocation code (see above).
wait_while_free_regions_coming();
append_secondary_free_list_if_not_empty_with_lock();
if (free_regions() >= num_regions) {
first = _hrs.find_contiguous(num_regions);
if (first != G1_NULL_HRS_INDEX) {
for (uint i = first; i < first + num_regions; ++i) {
HeapRegion* hr = region_at(i);
assert(hr->is_empty(), "sanity");
assert(is_on_master_free_list(hr), "sanity");
hr->set_pending_removal(true);
}
_free_list.remove_all_pending(num_regions);
}
}
}
return first;
}
HeapWord*
G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
uint num_regions,
size_t word_size) {
assert(first != G1_NULL_HRS_INDEX, "pre-condition");
assert(isHumongous(word_size), "word_size should be humongous");
assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
// Index of last region in the series + 1.
uint last = first + num_regions;
// We need to initialize the region(s) we just discovered. This is
// a bit tricky given that it can happen concurrently with
// refinement threads refining cards on these regions and
// potentially wanting to refine the BOT as they are scanning
// those cards (this can happen shortly after a cleanup; see CR
// 6991377). So we have to set up the region(s) carefully and in
// a specific order.
// The word size sum of all the regions we will allocate.
size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
assert(word_size <= word_size_sum, "sanity");
// This will be the "starts humongous" region.
HeapRegion* first_hr = region_at(first);
// The header of the new object will be placed at the bottom of
// the first region.
HeapWord* new_obj = first_hr->bottom();
// This will be the new end of the first region in the series that
// should also match the end of the last region in the series.
HeapWord* new_end = new_obj + word_size_sum;
// This will be the new top of the first region that will reflect
// this allocation.
HeapWord* new_top = new_obj + word_size;
// First, we need to zero the header of the space that we will be
// allocating. When we update top further down, some refinement
// threads might try to scan the region. By zeroing the header we
// ensure that any thread that will try to scan the region will
// come across the zero klass word and bail out.
//
// NOTE: It would not have been correct to have used
// CollectedHeap::fill_with_object() and make the space look like
// an int array. The thread that is doing the allocation will
// later update the object header to a potentially different array
// type and, for a very short period of time, the klass and length
// fields will be inconsistent. This could cause a refinement
// thread to calculate the object size incorrectly.
Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
// We will set up the first region as "starts humongous". This
// will also update the BOT covering all the regions to reflect
// that there is a single object that starts at the bottom of the
// first region.
first_hr->set_startsHumongous(new_top, new_end);
// Then, if there are any, we will set up the "continues
// humongous" regions.
HeapRegion* hr = NULL;
for (uint i = first + 1; i < last; ++i) {
hr = region_at(i);
hr->set_continuesHumongous(first_hr);
}
// If we have "continues humongous" regions (hr != NULL), then the
// end of the last one should match new_end.
assert(hr == NULL || hr->end() == new_end, "sanity");
// Up to this point no concurrent thread would have been able to
// do any scanning on any region in this series. All the top
// fields still point to bottom, so the intersection between
// [bottom,top] and [card_start,card_end] will be empty. Before we
// update the top fields, we'll do a storestore to make sure that
// no thread sees the update to top before the zeroing of the
// object header and the BOT initialization.
OrderAccess::storestore();
// Now that the BOT and the object header have been initialized,
// we can update top of the "starts humongous" region.
assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
"new_top should be in this region");
first_hr->set_top(new_top);
if (_hr_printer.is_active()) {
HeapWord* bottom = first_hr->bottom();
HeapWord* end = first_hr->orig_end();
if ((first + 1) == last) {
// the series has a single humongous region
_hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
} else {
// the series has more than one humongous regions
_hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
}
}
// Now, we will update the top fields of the "continues humongous"
// regions. The reason we need to do this is that, otherwise,
// these regions would look empty and this will confuse parts of
// G1. For example, the code that looks for a consecutive number
// of empty regions will consider them empty and try to
// re-allocate them. We can extend is_empty() to also include
// !continuesHumongous(), but it is easier to just update the top
// fields here. The way we set top for all regions (i.e., top ==
// end for all regions but the last one, top == new_top for the
// last one) is actually used when we will free up the humongous
// region in free_humongous_region().
hr = NULL;
for (uint i = first + 1; i < last; ++i) {
hr = region_at(i);
if ((i + 1) == last) {
// last continues humongous region
assert(hr->bottom() < new_top && new_top <= hr->end(),
"new_top should fall on this region");
hr->set_top(new_top);
_hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
} else {
// not last one
assert(new_top > hr->end(), "new_top should be above this region");
hr->set_top(hr->end());
_hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
}
}
// If we have continues humongous regions (hr != NULL), then the
// end of the last one should match new_end and its top should
// match new_top.
assert(hr == NULL ||
(hr->end() == new_end && hr->top() == new_top), "sanity");
assert(first_hr->used() == word_size * HeapWordSize, "invariant");
_summary_bytes_used += first_hr->used();
_humongous_set.add(first_hr);
return new_obj;
}
// If could fit into free regions w/o expansion, try.
// Otherwise, if can expand, do so.
// Otherwise, if using ex regions might help, try with ex given back.
HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
verify_region_sets_optional();
size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
uint x_num = expansion_regions();
uint fs = _hrs.free_suffix();
uint first = humongous_obj_allocate_find_first(num_regions, word_size);
if (first == G1_NULL_HRS_INDEX) {
// The only thing we can do now is attempt expansion.
if (fs + x_num >= num_regions) {
// If the number of regions we're trying to allocate for this
// object is at most the number of regions in the free suffix,
// then the call to humongous_obj_allocate_find_first() above
// should have succeeded and we wouldn't be here.
//
// We should only be trying to expand when the free suffix is
// not sufficient for the object _and_ we have some expansion
// room available.
assert(num_regions > fs, "earlier allocation should have succeeded");
ergo_verbose1(ErgoHeapSizing,
"attempt heap expansion",
ergo_format_reason("humongous allocation request failed")
ergo_format_byte("allocation request"),
word_size * HeapWordSize);
if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
// Even though the heap was expanded, it might not have
// reached the desired size. So, we cannot assume that the
// allocation will succeed.
first = humongous_obj_allocate_find_first(num_regions, word_size);
}
}
}
HeapWord* result = NULL;
if (first != G1_NULL_HRS_INDEX) {
result =
humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
assert(result != NULL, "it should always return a valid result");
// A successful humongous object allocation changes the used space
// information of the old generation so we need to recalculate the
// sizes and update the jstat counters here.
g1mm()->update_sizes();
}
verify_region_sets_optional();
return result;
}
HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
assert_heap_not_locked_and_not_at_safepoint();
assert(!isHumongous(word_size), "we do not allow humongous TLABs");
unsigned int dummy_gc_count_before;
int dummy_gclocker_retry_count = 0;
return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
}
HeapWord*
G1CollectedHeap::mem_allocate(size_t word_size,
bool* gc_overhead_limit_was_exceeded) {
assert_heap_not_locked_and_not_at_safepoint();
// Loop until the allocation is satisfied, or unsatisfied after GC.
for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
unsigned int gc_count_before;
HeapWord* result = NULL;
if (!isHumongous(word_size)) {
result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
} else {
result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
}
if (result != NULL) {
return result;
}
// Create the garbage collection operation...
VM_G1CollectForAllocation op(gc_count_before, word_size);
// ...and get the VM thread to execute it.
VMThread::execute(&op);
if (op.prologue_succeeded() && op.pause_succeeded()) {
// If the operation was successful we'll return the result even
// if it is NULL. If the allocation attempt failed immediately
// after a Full GC, it's unlikely we'll be able to allocate now.
HeapWord* result = op.result();
if (result != NULL && !isHumongous(word_size)) {
// Allocations that take place on VM operations do not do any
// card dirtying and we have to do it here. We only have to do
// this for non-humongous allocations, though.
dirty_young_block(result, word_size);
}
return result;
} else {
if (gclocker_retry_count > GCLockerRetryAllocationCount) {
return NULL;
}
assert(op.result() == NULL,
"the result should be NULL if the VM op did not succeed");
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
}
}
ShouldNotReachHere();
return NULL;
}
HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
unsigned int *gc_count_before_ret,
int* gclocker_retry_count_ret) {
// Make sure you read the note in attempt_allocation_humongous().
assert_heap_not_locked_and_not_at_safepoint();
assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
"be called for humongous allocation requests");
// We should only get here after the first-level allocation attempt
// (attempt_allocation()) failed to allocate.
// We will loop until a) we manage to successfully perform the
// allocation or b) we successfully schedule a collection which
// fails to perform the allocation. b) is the only case when we'll
// return NULL.
HeapWord* result = NULL;
for (int try_count = 1; /* we'll return */; try_count += 1) {
bool should_try_gc;
unsigned int gc_count_before;
{
MutexLockerEx x(Heap_lock);
result = _mutator_alloc_region.attempt_allocation_locked(word_size,
false /* bot_updates */);
if (result != NULL) {
return result;
}
// If we reach here, attempt_allocation_locked() above failed to
// allocate a new region. So the mutator alloc region should be NULL.
assert(_mutator_alloc_region.get() == NULL, "only way to get here");
if (GC_locker::is_active_and_needs_gc()) {
if (g1_policy()->can_expand_young_list()) {
// No need for an ergo verbose message here,
// can_expand_young_list() does this when it returns true.
result = _mutator_alloc_region.attempt_allocation_force(word_size,
false /* bot_updates */);
if (result != NULL) {
return result;
}
}
should_try_gc = false;
} else {
// The GCLocker may not be active but the GCLocker initiated
// GC may not yet have been performed (GCLocker::needs_gc()
// returns true). In this case we do not try this GC and
// wait until the GCLocker initiated GC is performed, and
// then retry the allocation.
if (GC_locker::needs_gc()) {
should_try_gc = false;
} else {
// Read the GC count while still holding the Heap_lock.
gc_count_before = total_collections();
should_try_gc = true;
}
}
}
if (should_try_gc) {
bool succeeded;
result = do_collection_pause(word_size, gc_count_before, &succeeded);
if (result != NULL) {
assert(succeeded, "only way to get back a non-NULL result");
return result;
}
if (succeeded) {
// If we get here we successfully scheduled a collection which
// failed to allocate. No point in trying to allocate
// further. We'll just return NULL.
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
} else {
if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
// The GCLocker is either active or the GCLocker initiated
// GC has not yet been performed. Stall until it is and
// then retry the allocation.
GC_locker::stall_until_clear();
(*gclocker_retry_count_ret) += 1;
}
// We can reach here if we were unsuccessful in scheduling a
// collection (because another thread beat us to it) or if we were
// stalled due to the GC locker. In either can we should retry the
// allocation attempt in case another thread successfully
// performed a collection and reclaimed enough space. We do the
// first attempt (without holding the Heap_lock) here and the
// follow-on attempt will be at the start of the next loop
// iteration (after taking the Heap_lock).
result = _mutator_alloc_region.attempt_allocation(word_size,
false /* bot_updates */);
if (result != NULL) {
return result;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("G1CollectedHeap::attempt_allocation_slow() "
"retries %d times", try_count);
}
}
ShouldNotReachHere();
return NULL;
}
HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
unsigned int * gc_count_before_ret,
int* gclocker_retry_count_ret) {
// The structure of this method has a lot of similarities to
// attempt_allocation_slow(). The reason these two were not merged
// into a single one is that such a method would require several "if
// allocation is not humongous do this, otherwise do that"
// conditional paths which would obscure its flow. In fact, an early
// version of this code did use a unified method which was harder to
// follow and, as a result, it had subtle bugs that were hard to
// track down. So keeping these two methods separate allows each to
// be more readable. It will be good to keep these two in sync as
// much as possible.
assert_heap_not_locked_and_not_at_safepoint();
assert(isHumongous(word_size), "attempt_allocation_humongous() "
"should only be called for humongous allocations");
// Humongous objects can exhaust the heap quickly, so we should check if we
// need to start a marking cycle at each humongous object allocation. We do
// the check before we do the actual allocation. The reason for doing it
// before the allocation is that we avoid having to keep track of the newly
// allocated memory while we do a GC.
if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
word_size)) {
collect(GCCause::_g1_humongous_allocation);
}
// We will loop until a) we manage to successfully perform the
// allocation or b) we successfully schedule a collection which
// fails to perform the allocation. b) is the only case when we'll
// return NULL.
HeapWord* result = NULL;
for (int try_count = 1; /* we'll return */; try_count += 1) {
bool should_try_gc;
unsigned int gc_count_before;
{
MutexLockerEx x(Heap_lock);
// Given that humongous objects are not allocated in young
// regions, we'll first try to do the allocation without doing a
// collection hoping that there's enough space in the heap.
result = humongous_obj_allocate(word_size);
if (result != NULL) {
return result;
}
if (GC_locker::is_active_and_needs_gc()) {
should_try_gc = false;
} else {
// The GCLocker may not be active but the GCLocker initiated
// GC may not yet have been performed (GCLocker::needs_gc()
// returns true). In this case we do not try this GC and
// wait until the GCLocker initiated GC is performed, and
// then retry the allocation.
if (GC_locker::needs_gc()) {
should_try_gc = false;
} else {
// Read the GC count while still holding the Heap_lock.
gc_count_before = total_collections();
should_try_gc = true;
}
}
}
if (should_try_gc) {
// If we failed to allocate the humongous object, we should try to
// do a collection pause (if we're allowed) in case it reclaims
// enough space for the allocation to succeed after the pause.
bool succeeded;
result = do_collection_pause(word_size, gc_count_before, &succeeded);
if (result != NULL) {
assert(succeeded, "only way to get back a non-NULL result");
return result;
}
if (succeeded) {
// If we get here we successfully scheduled a collection which
// failed to allocate. No point in trying to allocate
// further. We'll just return NULL.
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
} else {
if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
MutexLockerEx x(Heap_lock);
*gc_count_before_ret = total_collections();
return NULL;
}
// The GCLocker is either active or the GCLocker initiated
// GC has not yet been performed. Stall until it is and
// then retry the allocation.
GC_locker::stall_until_clear();
(*gclocker_retry_count_ret) += 1;
}
// We can reach here if we were unsuccessful in scheduling a
// collection (because another thread beat us to it) or if we were
// stalled due to the GC locker. In either can we should retry the
// allocation attempt in case another thread successfully
// performed a collection and reclaimed enough space. Give a
// warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("G1CollectedHeap::attempt_allocation_humongous() "
"retries %d times", try_count);
}
}
ShouldNotReachHere();
return NULL;
}
HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
bool expect_null_mutator_alloc_region) {
assert_at_safepoint(true /* should_be_vm_thread */);
assert(_mutator_alloc_region.get() == NULL ||
!expect_null_mutator_alloc_region,
"the current alloc region was unexpectedly found to be non-NULL");
if (!isHumongous(word_size)) {
return _mutator_alloc_region.attempt_allocation_locked(word_size,
false /* bot_updates */);
} else {
HeapWord* result = humongous_obj_allocate(word_size);
if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
g1_policy()->set_initiate_conc_mark_if_possible();
}
return result;
}
ShouldNotReachHere();
}
class PostMCRemSetClearClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
ModRefBarrierSet* _mr_bs;
public:
PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
_g1h(g1h), _mr_bs(mr_bs) {}
bool doHeapRegion(HeapRegion* r) {
HeapRegionRemSet* hrrs = r->rem_set();
if (r->continuesHumongous()) {
// We'll assert that the strong code root list and RSet is empty
assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
assert(hrrs->occupied() == 0, "RSet should be empty");
return false;
}
_g1h->reset_gc_time_stamps(r);
hrrs->clear();
// You might think here that we could clear just the cards
// corresponding to the used region. But no: if we leave a dirty card
// in a region we might allocate into, then it would prevent that card
// from being enqueued, and cause it to be missed.
// Re: the performance cost: we shouldn't be doing full GC anyway!
_mr_bs->clear(MemRegion(r->bottom(), r->end()));
return false;
}
};
void G1CollectedHeap::clear_rsets_post_compaction() {
PostMCRemSetClearClosure rs_clear(this, mr_bs());
heap_region_iterate(&rs_clear);
}
class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
UpdateRSOopClosure _cl;
int _worker_i;
public:
RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
_cl(g1->g1_rem_set(), worker_i),
_worker_i(worker_i),
_g1h(g1)
{ }
bool doHeapRegion(HeapRegion* r) {
if (!r->continuesHumongous()) {
_cl.set_from(r);
r->oop_iterate(&_cl);
}
return false;
}
};
class ParRebuildRSTask: public AbstractGangTask {
G1CollectedHeap* _g1;
public:
ParRebuildRSTask(G1CollectedHeap* g1)
: AbstractGangTask("ParRebuildRSTask"),
_g1(g1)
{ }
void work(uint worker_id) {
RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
_g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
_g1->workers()->active_workers(),
HeapRegion::RebuildRSClaimValue);
}
};
class PostCompactionPrinterClosure: public HeapRegionClosure {
private:
G1HRPrinter* _hr_printer;
public:
bool doHeapRegion(HeapRegion* hr) {
assert(!hr->is_young(), "not expecting to find young regions");
// We only generate output for non-empty regions.
if (!hr->is_empty()) {
if (!hr->isHumongous()) {
_hr_printer->post_compaction(hr, G1HRPrinter::Old);
} else if (hr->startsHumongous()) {
if (hr->region_num() == 1) {
// single humongous region
_hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
} else {
_hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
}
} else {
assert(hr->continuesHumongous(), "only way to get here");
_hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
}
}
return false;
}
PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
: _hr_printer(hr_printer) { }
};
void G1CollectedHeap::print_hrs_post_compaction() {
PostCompactionPrinterClosure cl(hr_printer());
heap_region_iterate(&cl);
}
bool G1CollectedHeap::do_collection(bool explicit_gc,
bool clear_all_soft_refs,
size_t word_size) {
assert_at_safepoint(true /* should_be_vm_thread */);
if (GC_locker::check_active_before_gc()) {
return false;
}
STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
gc_timer->register_gc_start(os::elapsed_counter());
SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
SvcGCMarker sgcm(SvcGCMarker::FULL);
ResourceMark rm;
print_heap_before_gc();
trace_heap_before_gc(gc_tracer);
size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
HRSPhaseSetter x(HRSPhaseFullGC);
verify_region_sets_optional();
const bool do_clear_all_soft_refs = clear_all_soft_refs ||
collector_policy()->should_clear_all_soft_refs();
ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
{
IsGCActiveMark x;
// Timing
assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
{
GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
TraceCollectorStats tcs(g1mm()->full_collection_counters());
TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
double start = os::elapsedTime();
g1_policy()->record_full_collection_start();
// Note: When we have a more flexible GC logging framework that
// allows us to add optional attributes to a GC log record we
// could consider timing and reporting how long we wait in the
// following two methods.
wait_while_free_regions_coming();
// If we start the compaction before the CM threads finish
// scanning the root regions we might trip them over as we'll
// be moving objects / updating references. So let's wait until
// they are done. By telling them to abort, they should complete
// early.
_cm->root_regions()->abort();
_cm->root_regions()->wait_until_scan_finished();
append_secondary_free_list_if_not_empty_with_lock();
gc_prologue(true);
increment_total_collections(true /* full gc */);
increment_old_marking_cycles_started();
assert(used() == recalculate_used(), "Should be equal");
verify_before_gc();
pre_full_gc_dump(gc_timer);
COMPILER2_PRESENT(DerivedPointerTable::clear());
// Disable discovery and empty the discovered lists
// for the CM ref processor.
ref_processor_cm()->disable_discovery();
ref_processor_cm()->abandon_partial_discovery();
ref_processor_cm()->verify_no_references_recorded();
// Abandon current iterations of concurrent marking and concurrent
// refinement, if any are in progress. We have to do this before
// wait_until_scan_finished() below.
concurrent_mark()->abort();
// Make sure we'll choose a new allocation region afterwards.
release_mutator_alloc_region();
abandon_gc_alloc_regions();
g1_rem_set()->cleanupHRRS();
// We should call this after we retire any currently active alloc
// regions so that all the ALLOC / RETIRE events are generated
// before the start GC event.
_hr_printer.start_gc(true /* full */, (size_t) total_collections());
// We may have added regions to the current incremental collection
// set between the last GC or pause and now. We need to clear the
// incremental collection set and then start rebuilding it afresh
// after this full GC.
abandon_collection_set(g1_policy()->inc_cset_head());
g1_policy()->clear_incremental_cset();
g1_policy()->stop_incremental_cset_building();
tear_down_region_sets(false /* free_list_only */);
g1_policy()->set_gcs_are_young(true);
// See the comments in g1CollectedHeap.hpp and
// G1CollectedHeap::ref_processing_init() about
// how reference processing currently works in G1.
// Temporarily make discovery by the STW ref processor single threaded (non-MT).
ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
// Temporarily clear the STW ref processor's _is_alive_non_header field.
ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
// Do collection work
{
HandleMark hm; // Discard invalid handles created during gc
G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
}
assert(free_regions() == 0, "we should not have added any free regions");
rebuild_region_sets(false /* free_list_only */);
// Enqueue any discovered reference objects that have
// not been removed from the discovered lists.
ref_processor_stw()->enqueue_discovered_references();
COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
MemoryService::track_memory_usage();
assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
ref_processor_stw()->verify_no_references_recorded();
// Delete metaspaces for unloaded class loaders and clean up loader_data graph
ClassLoaderDataGraph::purge();
MetaspaceAux::verify_metrics();
// Note: since we've just done a full GC, concurrent
// marking is no longer active. Therefore we need not
// re-enable reference discovery for the CM ref processor.
// That will be done at the start of the next marking cycle.
assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
ref_processor_cm()->verify_no_references_recorded();
reset_gc_time_stamp();
// Since everything potentially moved, we will clear all remembered
// sets, and clear all cards. Later we will rebuild remembered
// sets. We will also reset the GC time stamps of the regions.
clear_rsets_post_compaction();
check_gc_time_stamps();
// Resize the heap if necessary.
resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
if (_hr_printer.is_active()) {
// We should do this after we potentially resize the heap so
// that all the COMMIT / UNCOMMIT events are generated before
// the end GC event.
print_hrs_post_compaction();
_hr_printer.end_gc(true /* full */, (size_t) total_collections());
}
G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
if (hot_card_cache->use_cache()) {
hot_card_cache->reset_card_counts();
hot_card_cache->reset_hot_cache();
}
// Rebuild remembered sets of all regions.
if (G1CollectedHeap::use_parallel_gc_threads()) {
uint n_workers =
AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
workers()->active_workers(),
Threads::number_of_non_daemon_threads());
assert(UseDynamicNumberOfGCThreads ||
n_workers == workers()->total_workers(),
"If not dynamic should be using all the workers");
workers()->set_active_workers(n_workers);
// Set parallel threads in the heap (_n_par_threads) only
// before a parallel phase and always reset it to 0 after
// the phase so that the number of parallel threads does
// no get carried forward to a serial phase where there
// may be code that is "possibly_parallel".
set_par_threads(n_workers);
ParRebuildRSTask rebuild_rs_task(this);
assert(check_heap_region_claim_values(
HeapRegion::InitialClaimValue), "sanity check");
assert(UseDynamicNumberOfGCThreads ||
workers()->active_workers() == workers()->total_workers(),
"Unless dynamic should use total workers");
// Use the most recent number of active workers
assert(workers()->active_workers() > 0,
"Active workers not properly set");
set_par_threads(workers()->active_workers());
workers()->run_task(&rebuild_rs_task);
set_par_threads(0);
assert(check_heap_region_claim_values(
HeapRegion::RebuildRSClaimValue), "sanity check");
reset_heap_region_claim_values();
} else {
RebuildRSOutOfRegionClosure rebuild_rs(this);
heap_region_iterate(&rebuild_rs);
}
// Rebuild the strong code root lists for each region
rebuild_strong_code_roots();
if (true) { // FIXME
MetaspaceGC::compute_new_size();
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
// Discard all rset updates
JavaThread::dirty_card_queue_set().abandon_logs();
assert(!G1DeferredRSUpdate
|| (G1DeferredRSUpdate &&
(dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
_young_list->reset_sampled_info();
// At this point there should be no regions in the
// entire heap tagged as young.
assert(check_young_list_empty(true /* check_heap */),
"young list should be empty at this point");
// Update the number of full collections that have been completed.
increment_old_marking_cycles_completed(false /* concurrent */);
_hrs.verify_optional();
verify_region_sets_optional();
verify_after_gc();
// Start a new incremental collection set for the next pause
assert(g1_policy()->collection_set() == NULL, "must be");
g1_policy()->start_incremental_cset_building();
// Clear the _cset_fast_test bitmap in anticipation of adding
// regions to the incremental collection set for the next
// evacuation pause.
clear_cset_fast_test();
init_mutator_alloc_region();
double end = os::elapsedTime();
g1_policy()->record_full_collection_end();
if (G1Log::fine()) {
g1_policy()->print_heap_transition();
}
// We must call G1MonitoringSupport::update_sizes() in the same scoping level
// as an active TraceMemoryManagerStats object (i.e. before the destructor for the
// TraceMemoryManagerStats is called) so that the G1 memory pools are updated
// before any GC notifications are raised.
g1mm()->update_sizes();
gc_epilogue(true);
}
if (G1Log::finer()) {
g1_policy()->print_detailed_heap_transition(true /* full */);
}
print_heap_after_gc();
trace_heap_after_gc(gc_tracer);
post_full_gc_dump(gc_timer);
gc_timer->register_gc_end(os::elapsed_counter());
gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
}
return true;
}
void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
// do_collection() will return whether it succeeded in performing
// the GC. Currently, there is no facility on the
// do_full_collection() API to notify the caller than the collection
// did not succeed (e.g., because it was locked out by the GC
// locker). So, right now, we'll ignore the return value.
bool dummy = do_collection(true, /* explicit_gc */
clear_all_soft_refs,
0 /* word_size */);
}
// This code is mostly copied from TenuredGeneration.
void
G1CollectedHeap::
resize_if_necessary_after_full_collection(size_t word_size) {
assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
// Include the current allocation, if any, and bytes that will be
// pre-allocated to support collections, as "used".
const size_t used_after_gc = used();
const size_t capacity_after_gc = capacity();
const size_t free_after_gc = capacity_after_gc - used_after_gc;
// This is enforced in arguments.cpp.
assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
"otherwise the code below doesn't make sense");
// We don't have floating point command-line arguments
const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
const double maximum_used_percentage = 1.0 - minimum_free_percentage;
const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
const double minimum_used_percentage = 1.0 - maximum_free_percentage;
const size_t min_heap_size = collector_policy()->min_heap_byte_size();
const size_t max_heap_size = collector_policy()->max_heap_byte_size();
// We have to be careful here as these two calculations can overflow
// 32-bit size_t's.
double used_after_gc_d = (double) used_after_gc;
double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
// Let's make sure that they are both under the max heap size, which
// by default will make them fit into a size_t.
double desired_capacity_upper_bound = (double) max_heap_size;
minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
desired_capacity_upper_bound);
maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
desired_capacity_upper_bound);
// We can now safely turn them into size_t's.
size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
// This assert only makes sense here, before we adjust them
// with respect to the min and max heap size.
assert(minimum_desired_capacity <= maximum_desired_capacity,
err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
"maximum_desired_capacity = "SIZE_FORMAT,
minimum_desired_capacity, maximum_desired_capacity));
// Should not be greater than the heap max size. No need to adjust
// it with respect to the heap min size as it's a lower bound (i.e.,
// we'll try to make the capacity larger than it, not smaller).
minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
// Should not be less than the heap min size. No need to adjust it
// with respect to the heap max size as it's an upper bound (i.e.,
// we'll try to make the capacity smaller than it, not greater).
maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
if (capacity_after_gc < minimum_desired_capacity) {
// Don't expand unless it's significant
size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
ergo_verbose4(ErgoHeapSizing,
"attempt heap expansion",
ergo_format_reason("capacity lower than "
"min desired capacity after Full GC")
ergo_format_byte("capacity")
ergo_format_byte("occupancy")
ergo_format_byte_perc("min desired capacity"),
capacity_after_gc, used_after_gc,
minimum_desired_capacity, (double) MinHeapFreeRatio);
expand(expand_bytes);
// No expansion, now see if we want to shrink
} else if (capacity_after_gc > maximum_desired_capacity) {
// Capacity too large, compute shrinking size
size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
ergo_verbose4(ErgoHeapSizing,
"attempt heap shrinking",
ergo_format_reason("capacity higher than "
"max desired capacity after Full GC")
ergo_format_byte("capacity")
ergo_format_byte("occupancy")
ergo_format_byte_perc("max desired capacity"),
capacity_after_gc, used_after_gc,
maximum_desired_capacity, (double) MaxHeapFreeRatio);
shrink(shrink_bytes);
}
}
HeapWord*
G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
bool* succeeded) {
assert_at_safepoint(true /* should_be_vm_thread */);
*succeeded = true;
// Let's attempt the allocation first.
HeapWord* result =
attempt_allocation_at_safepoint(word_size,
false /* expect_null_mutator_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
}
// In a G1 heap, we're supposed to keep allocation from failing by
// incremental pauses. Therefore, at least for now, we'll favor
// expansion over collection. (This might change in the future if we can
// do something smarter than full collection to satisfy a failed alloc.)
result = expand_and_allocate(word_size);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
}
// Expansion didn't work, we'll try to do a Full GC.
bool gc_succeeded = do_collection(false, /* explicit_gc */
false, /* clear_all_soft_refs */
word_size);
if (!gc_succeeded) {
*succeeded = false;
return NULL;
}
// Retry the allocation
result = attempt_allocation_at_safepoint(word_size,
true /* expect_null_mutator_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
}
// Then, try a Full GC that will collect all soft references.
gc_succeeded = do_collection(false, /* explicit_gc */
true, /* clear_all_soft_refs */
word_size);
if (!gc_succeeded) {
*succeeded = false;
return NULL;
}
// Retry the allocation once more
result = attempt_allocation_at_safepoint(word_size,
true /* expect_null_mutator_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
}
assert(!collector_policy()->should_clear_all_soft_refs(),
"Flag should have been handled and cleared prior to this point");
// What else? We might try synchronous finalization later. If the total
// space available is large enough for the allocation, then a more
// complete compaction phase than we've tried so far might be
// appropriate.
assert(*succeeded, "sanity");
return NULL;
}
// Attempting to expand the heap sufficiently
// to support an allocation of the given "word_size". If
// successful, perform the allocation and return the address of the
// allocated block, or else "NULL".
HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
assert_at_safepoint(true /* should_be_vm_thread */);
verify_region_sets_optional();
size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
ergo_verbose1(ErgoHeapSizing,
"attempt heap expansion",
ergo_format_reason("allocation request failed")
ergo_format_byte("allocation request"),
word_size * HeapWordSize);
if (expand(expand_bytes)) {
_hrs.verify_optional();
verify_region_sets_optional();
return attempt_allocation_at_safepoint(word_size,
false /* expect_null_mutator_alloc_region */);
}
return NULL;
}
void G1CollectedHeap::update_committed_space(HeapWord* old_end,
HeapWord* new_end) {
assert(old_end != new_end, "don't call this otherwise");
assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
// Update the committed mem region.
_g1_committed.set_end(new_end);
// Tell the card table about the update.
Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
// Tell the BOT about the update.
_bot_shared->resize(_g1_committed.word_size());
// Tell the hot card cache about the update
_cg1r->hot_card_cache()->resize_card_counts(capacity());
}
bool G1CollectedHeap::expand(size_t expand_bytes) {
size_t old_mem_size = _g1_storage.committed_size();
size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
aligned_expand_bytes = align_size_up(aligned_expand_bytes,
HeapRegion::GrainBytes);
ergo_verbose2(ErgoHeapSizing,
"expand the heap",
ergo_format_byte("requested expansion amount")
ergo_format_byte("attempted expansion amount"),
expand_bytes, aligned_expand_bytes);
// First commit the memory.
HeapWord* old_end = (HeapWord*) _g1_storage.high();
bool successful = _g1_storage.expand_by(aligned_expand_bytes);
if (successful) {
// Then propagate this update to the necessary data structures.
HeapWord* new_end = (HeapWord*) _g1_storage.high();
update_committed_space(old_end, new_end);
FreeRegionList expansion_list("Local Expansion List");
MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
assert(mr.start() == old_end, "post-condition");
// mr might be a smaller region than what was requested if
// expand_by() was unable to allocate the HeapRegion instances
assert(mr.end() <= new_end, "post-condition");
size_t actual_expand_bytes = mr.byte_size();
assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
"post-condition");
if (actual_expand_bytes < aligned_expand_bytes) {
// We could not expand _hrs to the desired size. In this case we
// need to shrink the committed space accordingly.
assert(mr.end() < new_end, "invariant");
size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
// First uncommit the memory.
_g1_storage.shrink_by(diff_bytes);
// Then propagate this update to the necessary data structures.
update_committed_space(new_end, mr.end());
}
_free_list.add_as_tail(&expansion_list);
if (_hr_printer.is_active()) {
HeapWord* curr = mr.start();
while (curr < mr.end()) {
HeapWord* curr_end = curr + HeapRegion::GrainWords;
_hr_printer.commit(curr, curr_end);
curr = curr_end;
}
assert(curr == mr.end(), "post-condition");
}
g1_policy()->record_new_heap_size(n_regions());
} else {
ergo_verbose0(ErgoHeapSizing,
"did not expand the heap",
ergo_format_reason("heap expansion operation failed"));
// The expansion of the virtual storage space was unsuccessful.
// Let's see if it was because we ran out of swap.
if (G1ExitOnExpansionFailure &&
_g1_storage.uncommitted_size() >= aligned_expand_bytes) {
// We had head room...
vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
}
}
return successful;
}
void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
size_t old_mem_size = _g1_storage.committed_size();
size_t aligned_shrink_bytes =
ReservedSpace::page_align_size_down(shrink_bytes);
aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
HeapRegion::GrainBytes);
uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
HeapWord* old_end = (HeapWord*) _g1_storage.high();
size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
ergo_verbose3(ErgoHeapSizing,
"shrink the heap",
ergo_format_byte("requested shrinking amount")
ergo_format_byte("aligned shrinking amount")
ergo_format_byte("attempted shrinking amount"),
shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
if (num_regions_removed > 0) {
_g1_storage.shrink_by(shrunk_bytes);
HeapWord* new_end = (HeapWord*) _g1_storage.high();
if (_hr_printer.is_active()) {
HeapWord* curr = old_end;
while (curr > new_end) {
HeapWord* curr_end = curr;
curr -= HeapRegion::GrainWords;
_hr_printer.uncommit(curr, curr_end);
}
}
_expansion_regions += num_regions_removed;
update_committed_space(old_end, new_end);
HeapRegionRemSet::shrink_heap(n_regions());
g1_policy()->record_new_heap_size(n_regions());
} else {
ergo_verbose0(ErgoHeapSizing,
"did not shrink the heap",
ergo_format_reason("heap shrinking operation failed"));
}
}
void G1CollectedHeap::shrink(size_t shrink_bytes) {
verify_region_sets_optional();
// We should only reach here at the end of a Full GC which means we
// should not not be holding to any GC alloc regions. The method
// below will make sure of that and do any remaining clean up.
abandon_gc_alloc_regions();
// Instead of tearing down / rebuilding the free lists here, we
// could instead use the remove_all_pending() method on free_list to
// remove only the ones that we need to remove.
tear_down_region_sets(true /* free_list_only */);
shrink_helper(shrink_bytes);
rebuild_region_sets(true /* free_list_only */);
_hrs.verify_optional();
verify_region_sets_optional();
}
// Public methods.
#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
#endif // _MSC_VER
G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
SharedHeap(policy_),
_g1_policy(policy_),
_dirty_card_queue_set(false),
_into_cset_dirty_card_queue_set(false),
_is_alive_closure_cm(this),
_is_alive_closure_stw(this),
_ref_processor_cm(NULL),
_ref_processor_stw(NULL),
_process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
_bot_shared(NULL),
_evac_failure_scan_stack(NULL),
_mark_in_progress(false),
_cg1r(NULL), _summary_bytes_used(0),
_g1mm(NULL),
_refine_cte_cl(NULL),
_full_collection(false),
_free_list("Master Free List"),
_secondary_free_list("Secondary Free List"),
_old_set("Old Set"),
_humongous_set("Master Humongous Set"),
_free_regions_coming(false),
_young_list(new YoungList(this)),
_gc_time_stamp(0),
_retained_old_gc_alloc_region(NULL),
_survivor_plab_stats(YoungPLABSize, PLABWeight),
_old_plab_stats(OldPLABSize, PLABWeight),
_expand_heap_after_alloc_failure(true),
_surviving_young_words(NULL),
_old_marking_cycles_started(0),
_old_marking_cycles_completed(0),
_concurrent_cycle_started(false),
_in_cset_fast_test(NULL),
_in_cset_fast_test_base(NULL),
_dirty_cards_region_list(NULL),
_worker_cset_start_region(NULL),
_worker_cset_start_region_time_stamp(NULL),
_gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
_gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
_gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
_gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
_g1h = this;
if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
vm_exit_during_initialization("Failed necessary allocation.");
}
_humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
int n_queues = MAX2((int)ParallelGCThreads, 1);
_task_queues = new RefToScanQueueSet(n_queues);
int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
assert(n_rem_sets > 0, "Invariant.");
_worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
_worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
_evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
for (int i = 0; i < n_queues; i++) {
RefToScanQueue* q = new RefToScanQueue();
q->initialize();
_task_queues->register_queue(i, q);
::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
}
clear_cset_start_regions();
// Initialize the G1EvacuationFailureALot counters and flags.
NOT_PRODUCT(reset_evacuation_should_fail();)
guarantee(_task_queues != NULL, "task_queues allocation failure.");
}
jint G1CollectedHeap::initialize() {
CollectedHeap::pre_initialize();
os::enable_vtime();
G1Log::init();
// Necessary to satisfy locking discipline assertions.
MutexLocker x(Heap_lock);
// We have to initialize the printer before committing the heap, as
// it will be used then.
_hr_printer.set_active(G1PrintHeapRegions);
// While there are no constraints in the GC code that HeapWordSize
// be any particular value, there are multiple other areas in the
// system which believe this to be true (e.g. oop->object_size in some
// cases incorrectly returns the size in wordSize units rather than
// HeapWordSize).
guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
size_t init_byte_size = collector_policy()->initial_heap_byte_size();
size_t max_byte_size = collector_policy()->max_heap_byte_size();
// Ensure that the sizes are properly aligned.
Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
_cg1r = new ConcurrentG1Refine(this);
// Reserve the maximum.
// When compressed oops are enabled, the preferred heap base
// is calculated by subtracting the requested size from the
// 32Gb boundary and using the result as the base address for
// heap reservation. If the requested size is not aligned to
// HeapRegion::GrainBytes (i.e. the alignment that is passed
// into the ReservedHeapSpace constructor) then the actual
// base of the reserved heap may end up differing from the
// address that was requested (i.e. the preferred heap base).
// If this happens then we could end up using a non-optimal
// compressed oops mode.
// Since max_byte_size is aligned to the size of a heap region (checked
// above).
Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
HeapRegion::GrainBytes);
// It is important to do this in a way such that concurrent readers can't
// temporarily think something is in the heap. (I've actually seen this
// happen in asserts: DLD.)
_reserved.set_word_size(0);
_reserved.set_start((HeapWord*)heap_rs.base());
_reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
_expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
// Create the gen rem set (and barrier set) for the entire reserved region.
_rem_set = collector_policy()->create_rem_set(_reserved, 2);
set_barrier_set(rem_set()->bs());
if (barrier_set()->is_a(BarrierSet::ModRef)) {
_mr_bs = (ModRefBarrierSet*)_barrier_set;
} else {
vm_exit_during_initialization("G1 requires a mod ref bs.");
return JNI_ENOMEM;
}
// Also create a G1 rem set.
if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
_g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
} else {
vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
return JNI_ENOMEM;
}
// Carve out the G1 part of the heap.
ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
_g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
g1_rs.size()/HeapWordSize);
_g1_storage.initialize(g1_rs, 0);
_g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
_hrs.initialize((HeapWord*) _g1_reserved.start(),
(HeapWord*) _g1_reserved.end(),
_expansion_regions);
// Do later initialization work for concurrent refinement.
_cg1r->init();
// 6843694 - ensure that the maximum region index can fit
// in the remembered set structures.
const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
"too many cards per region");
HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
_bot_shared = new G1BlockOffsetSharedArray(_reserved,
heap_word_size(init_byte_size));
_g1h = this;
_in_cset_fast_test_length = max_regions();
_in_cset_fast_test_base =
NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
// We're biasing _in_cset_fast_test to avoid subtracting the
// beginning of the heap every time we want to index; basically
// it's the same with what we do with the card table.
_in_cset_fast_test = _in_cset_fast_test_base -
((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
// Clear the _cset_fast_test bitmap in anticipation of adding
// regions to the incremental collection set for the first
// evacuation pause.
clear_cset_fast_test();
// Create the ConcurrentMark data structure and thread.
// (Must do this late, so that "max_regions" is defined.)
_cm = new ConcurrentMark(this, heap_rs);
if (_cm == NULL || !_cm->completed_initialization()) {
vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
return JNI_ENOMEM;
}
_cmThread = _cm->cmThread();
// Initialize the from_card cache structure of HeapRegionRemSet.
HeapRegionRemSet::init_heap(max_regions());
// Now expand into the initial heap size.
if (!expand(init_byte_size)) {
vm_shutdown_during_initialization("Failed to allocate initial heap.");
return JNI_ENOMEM;
}
// Perform any initialization actions delegated to the policy.
g1_policy()->init();
_refine_cte_cl =
new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
g1_rem_set(),
concurrent_g1_refine());
JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
SATB_Q_FL_lock,
G1SATBProcessCompletedThreshold,
Shared_SATB_Q_lock);
JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
DirtyCardQ_FL_lock,
concurrent_g1_refine()->yellow_zone(),
concurrent_g1_refine()->red_zone(),
Shared_DirtyCardQ_lock);
if (G1DeferredRSUpdate) {
dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
DirtyCardQ_FL_lock,
-1, // never trigger processing
-1, // no limit on length
Shared_DirtyCardQ_lock,
&JavaThread::dirty_card_queue_set());
}
// Initialize the card queue set used to hold cards containing
// references into the collection set.
_into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
DirtyCardQ_FL_lock,
-1, // never trigger processing
-1, // no limit on length
Shared_DirtyCardQ_lock,
&JavaThread::dirty_card_queue_set());
// In case we're keeping closure specialization stats, initialize those
// counts and that mechanism.
SpecializationStats::clear();
// Here we allocate the dummy full region that is required by the
// G1AllocRegion class. If we don't pass an address in the reserved
// space here, lots of asserts fire.
HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
_g1_reserved.start());
// We'll re-use the same region whether the alloc region will
// require BOT updates or not and, if it doesn't, then a non-young
// region will complain that it cannot support allocations without
// BOT updates. So we'll tag the dummy region as young to avoid that.
dummy_region->set_young();
// Make sure it's full.
dummy_region->set_top(dummy_region->end());
G1AllocRegion::setup(this, dummy_region);
init_mutator_alloc_region();
// Do create of the monitoring and management support so that
// values in the heap have been properly initialized.
_g1mm = new G1MonitoringSupport(this);
return JNI_OK;
}
void G1CollectedHeap::ref_processing_init() {
// Reference processing in G1 currently works as follows:
//
// * There are two reference processor instances. One is
// used to record and process discovered references
// during concurrent marking; the other is used to
// record and process references during STW pauses
// (both full and incremental).
// * Both ref processors need to 'span' the entire heap as
// the regions in the collection set may be dotted around.
//
// * For the concurrent marking ref processor:
// * Reference discovery is enabled at initial marking.
// * Reference discovery is disabled and the discovered
// references processed etc during remarking.
// * Reference discovery is MT (see below).
// * Reference discovery requires a barrier (see below).
// * Reference processing may or may not be MT
// (depending on the value of ParallelRefProcEnabled
// and ParallelGCThreads).
// * A full GC disables reference discovery by the CM
// ref processor and abandons any entries on it's
// discovered lists.
//
// * For the STW processor:
// * Non MT discovery is enabled at the start of a full GC.
// * Processing and enqueueing during a full GC is non-MT.
// * During a full GC, references are processed after marking.
//
// * Discovery (may or may not be MT) is enabled at the start
// of an incremental evacuation pause.
// * References are processed near the end of a STW evacuation pause.
// * For both types of GC:
// * Discovery is atomic - i.e. not concurrent.
// * Reference discovery will not need a barrier.
SharedHeap::ref_processing_init();
MemRegion mr = reserved_region();
// Concurrent Mark ref processor
_ref_processor_cm =
new ReferenceProcessor(mr, // span
ParallelRefProcEnabled && (ParallelGCThreads > 1),
// mt processing
(int) ParallelGCThreads,
// degree of mt processing
(ParallelGCThreads > 1) || (ConcGCThreads > 1),
// mt discovery
(int) MAX2(ParallelGCThreads, ConcGCThreads),
// degree of mt discovery
false,
// Reference discovery is not atomic
&_is_alive_closure_cm,
// is alive closure
// (for efficiency/performance)
true);
// Setting next fields of discovered
// lists requires a barrier.
// STW ref processor
_ref_processor_stw =
new ReferenceProcessor(mr, // span
ParallelRefProcEnabled && (ParallelGCThreads > 1),
// mt processing
MAX2((int)ParallelGCThreads, 1),
// degree of mt processing
(ParallelGCThreads > 1),
// mt discovery
MAX2((int)ParallelGCThreads, 1),
// degree of mt discovery
true,
// Reference discovery is atomic
&_is_alive_closure_stw,
// is alive closure
// (for efficiency/performance)
false);
// Setting next fields of discovered
// lists requires a barrier.
}
size_t G1CollectedHeap::capacity() const {
return _g1_committed.byte_size();
}
void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
assert(!hr->continuesHumongous(), "pre-condition");
hr->reset_gc_time_stamp();
if (hr->startsHumongous()) {
uint first_index = hr->hrs_index() + 1;
uint last_index = hr->last_hc_index();
for (uint i = first_index; i < last_index; i += 1) {
HeapRegion* chr = region_at(i);
assert(chr->continuesHumongous(), "sanity");
chr->reset_gc_time_stamp();
}
}
}
#ifndef PRODUCT
class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
private:
unsigned _gc_time_stamp;
bool _failures;
public:
CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
_gc_time_stamp(gc_time_stamp), _failures(false) { }
virtual bool doHeapRegion(HeapRegion* hr) {
unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
if (_gc_time_stamp != region_gc_time_stamp) {
gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
"expected %d", HR_FORMAT_PARAMS(hr),
region_gc_time_stamp, _gc_time_stamp);
_failures = true;
}
return false;
}
bool failures() { return _failures; }
};
void G1CollectedHeap::check_gc_time_stamps() {
CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
heap_region_iterate(&cl);
guarantee(!cl.failures(), "all GC time stamps should have been reset");
}
#endif // PRODUCT
void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
DirtyCardQueue* into_cset_dcq,
bool concurrent,
int worker_i) {
// Clean cards in the hot card cache
G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
int n_completed_buffers = 0;
while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
n_completed_buffers++;
}
g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
dcqs.clear_n_completed_buffers();
assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
}
// Computes the sum of the storage used by the various regions.
size_t G1CollectedHeap::used() const {
assert(Heap_lock->owner() != NULL,
"Should be owned on this thread's behalf.");
size_t result = _summary_bytes_used;
// Read only once in case it is set to NULL concurrently
HeapRegion* hr = _mutator_alloc_region.get();
if (hr != NULL)
result += hr->used();
return result;
}
size_t G1CollectedHeap::used_unlocked() const {
size_t result = _summary_bytes_used;
return result;
}
class SumUsedClosure: public HeapRegionClosure {
size_t _used;
public:
SumUsedClosure() : _used(0) {}
bool doHeapRegion(HeapRegion* r) {
if (!r->continuesHumongous()) {
_used += r->used();
}
return false;
}
size_t result() { return _used; }
};
size_t G1CollectedHeap::recalculate_used() const {
SumUsedClosure blk;
heap_region_iterate(&blk);
return blk.result();
}
size_t G1CollectedHeap::unsafe_max_alloc() {
if (free_regions() > 0) return HeapRegion::GrainBytes;
// otherwise, is there space in the current allocation region?
// We need to store the current allocation region in a local variable
// here. The problem is that this method doesn't take any locks and
// there may be other threads which overwrite the current allocation
// region field. attempt_allocation(), for example, sets it to NULL
// and this can happen *after* the NULL check here but before the call
// to free(), resulting in a SIGSEGV. Note that this doesn't appear
// to be a problem in the optimized build, since the two loads of the
// current allocation region field are optimized away.
HeapRegion* hr = _mutator_alloc_region.get();
if (hr == NULL) {
return 0;
}
return hr->free();
}
bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
switch (cause) {
case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
case GCCause::_g1_humongous_allocation: return true;
default: return false;
}
}
#ifndef PRODUCT
void G1CollectedHeap::allocate_dummy_regions() {
// Let's fill up most of the region
size_t word_size = HeapRegion::GrainWords - 1024;
// And as a result the region we'll allocate will be humongous.
guarantee(isHumongous(word_size), "sanity");
for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
// Let's use the existing mechanism for the allocation
HeapWord* dummy_obj = humongous_obj_allocate(word_size);
if (dummy_obj != NULL) {
MemRegion mr(dummy_obj, word_size);
CollectedHeap::fill_with_object(mr);
} else {
// If we can't allocate once, we probably cannot allocate
// again. Let's get out of the loop.
break;
}
}
}
#endif // !PRODUCT
void G1CollectedHeap::increment_old_marking_cycles_started() {
assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
_old_marking_cycles_started == _old_marking_cycles_completed + 1,
err_msg("Wrong marking cycle count (started: %d, completed: %d)",
_old_marking_cycles_started, _old_marking_cycles_completed));
_old_marking_cycles_started++;
}
void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
// We assume that if concurrent == true, then the caller is a
// concurrent thread that was joined the Suspendible Thread
// Set. If there's ever a cheap way to check this, we should add an
// assert here.
// Given that this method is called at the end of a Full GC or of a
// concurrent cycle, and those can be nested (i.e., a Full GC can
// interrupt a concurrent cycle), the number of full collections
// completed should be either one (in the case where there was no
// nesting) or two (when a Full GC interrupted a concurrent cycle)
// behind the number of full collections started.
// This is the case for the inner caller, i.e. a Full GC.
assert(concurrent ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 2),
err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
"is inconsistent with _old_marking_cycles_completed = %u",
_old_marking_cycles_started, _old_marking_cycles_completed));
// This is the case for the outer caller, i.e. the concurrent cycle.
assert(!concurrent ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 1),
err_msg("for outer caller (concurrent cycle): "
"_old_marking_cycles_started = %u "
"is inconsistent with _old_marking_cycles_completed = %u",
_old_marking_cycles_started, _old_marking_cycles_completed));
_old_marking_cycles_completed += 1;
// We need to clear the "in_progress" flag in the CM thread before
// we wake up any waiters (especially when ExplicitInvokesConcurrent
// is set) so that if a waiter requests another System.gc() it doesn't
// incorrectly see that a marking cycle is still in progress.
if (concurrent) {
_cmThread->clear_in_progress();
}
// This notify_all() will ensure that a thread that called
// System.gc() with (with ExplicitGCInvokesConcurrent set or not)
// and it's waiting for a full GC to finish will be woken up. It is
// waiting in VM_G1IncCollectionPause::doit_epilogue().
FullGCCount_lock->notify_all();
}
void G1CollectedHeap::register_concurrent_cycle_start(jlong start_time) {
_concurrent_cycle_started = true;
_gc_timer_cm->register_gc_start(start_time);
_gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
trace_heap_before_gc(_gc_tracer_cm);
}
void G1CollectedHeap::register_concurrent_cycle_end() {
if (_concurrent_cycle_started) {
_gc_timer_cm->register_gc_end(os::elapsed_counter());
if (_cm->has_aborted()) {
_gc_tracer_cm->report_concurrent_mode_failure();
}
_gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
_concurrent_cycle_started = false;
}
}
void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
if (_concurrent_cycle_started) {
trace_heap_after_gc(_gc_tracer_cm);
}
}
G1YCType G1CollectedHeap::yc_type() {
bool is_young = g1_policy()->gcs_are_young();
bool is_initial_mark = g1_policy()->during_initial_mark_pause();
bool is_during_mark = mark_in_progress();
if (is_initial_mark) {
return InitialMark;
} else if (is_during_mark) {
return DuringMark;
} else if (is_young) {
return Normal;
} else {
return Mixed;
}
}
void G1CollectedHeap::collect(GCCause::Cause cause) {
assert_heap_not_locked();
unsigned int gc_count_before;
unsigned int old_marking_count_before;
bool retry_gc;
do {
retry_gc = false;
{
MutexLocker ml(Heap_lock);
// Read the GC count while holding the Heap_lock
gc_count_before = total_collections();
old_marking_count_before = _old_marking_cycles_started;
}
if (should_do_concurrent_full_gc(cause)) {
// Schedule an initial-mark evacuation pause that will start a
// concurrent cycle. We're setting word_size to 0 which means that
// we are not requesting a post-GC allocation.
VM_G1IncCollectionPause op(gc_count_before,
0, /* word_size */
true, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
cause);
VMThread::execute(&op);
if (!op.pause_succeeded()) {
if (old_marking_count_before == _old_marking_cycles_started) {
retry_gc = op.should_retry_gc();
} else {
// A Full GC happened while we were trying to schedule the
// initial-mark GC. No point in starting a new cycle given
// that the whole heap was collected anyway.
}
if (retry_gc) {
if (GC_locker::is_active_and_needs_gc()) {
GC_locker::stall_until_clear();
}
}
}
} else {
if (cause == GCCause::_gc_locker
DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
// Schedule a standard evacuation pause. We're setting word_size
// to 0 which means that we are not requesting a post-GC allocation.
VM_G1IncCollectionPause op(gc_count_before,
0, /* word_size */
false, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
cause);
VMThread::execute(&op);
} else {
// Schedule a Full GC.
VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
VMThread::execute(&op);
}
}
} while (retry_gc);
}
bool G1CollectedHeap::is_in(const void* p) const {
if (_g1_committed.contains(p)) {
// Given that we know that p is in the committed space,
// heap_region_containing_raw() should successfully
// return the containing region.
HeapRegion* hr = heap_region_containing_raw(p);
return hr->is_in(p);
} else {
return false;
}
}
// Iteration functions.
// Iterates an OopClosure over all ref-containing fields of objects
// within a HeapRegion.
class IterateOopClosureRegionClosure: public HeapRegionClosure {
MemRegion _mr;
ExtendedOopClosure* _cl;
public:
IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
: _mr(mr), _cl(cl) {}
bool doHeapRegion(HeapRegion* r) {
if (!r->continuesHumongous()) {
r->oop_iterate(_cl);
}
return false;
}
};
void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
IterateOopClosureRegionClosure blk(_g1_committed, cl);
heap_region_iterate(&blk);
}
void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
IterateOopClosureRegionClosure blk(mr, cl);
heap_region_iterate(&blk);
}
// Iterates an ObjectClosure over all objects within a HeapRegion.
class IterateObjectClosureRegionClosure: public HeapRegionClosure {
ObjectClosure* _cl;
public:
IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
bool doHeapRegion(HeapRegion* r) {
if (! r->continuesHumongous()) {
r->object_iterate(_cl);
}
return false;
}
};
void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
IterateObjectClosureRegionClosure blk(cl);
heap_region_iterate(&blk);
}
// Calls a SpaceClosure on a HeapRegion.
class SpaceClosureRegionClosure: public HeapRegionClosure {
SpaceClosure* _cl;
public:
SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
bool doHeapRegion(HeapRegion* r) {
_cl->do_space(r);
return false;
}
};
void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
SpaceClosureRegionClosure blk(cl);
heap_region_iterate(&blk);
}
void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
_hrs.iterate(cl);
}
void
G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
uint worker_id,
uint no_of_par_workers,
jint claim_value) {
const uint regions = n_regions();
const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
no_of_par_workers :
1);
assert(UseDynamicNumberOfGCThreads ||
no_of_par_workers == workers()->total_workers(),
"Non dynamic should use fixed number of workers");
// try to spread out the starting points of the workers
const HeapRegion* start_hr =
start_region_for_worker(worker_id, no_of_par_workers);
const uint start_index = start_hr->hrs_index();
// each worker will actually look at all regions
for (uint count = 0; count < regions; ++count) {
const uint index = (start_index + count) % regions;
assert(0 <= index && index < regions, "sanity");
HeapRegion* r = region_at(index);
// we'll ignore "continues humongous" regions (we'll process them
// when we come across their corresponding "start humongous"
// region) and regions already claimed
if (r->claim_value() == claim_value || r->continuesHumongous()) {
continue;
}
// OK, try to claim it
if (r->claimHeapRegion(claim_value)) {
// success!
assert(!r->continuesHumongous(), "sanity");
if (r->startsHumongous()) {
// If the region is "starts humongous" we'll iterate over its
// "continues humongous" first; in fact we'll do them
// first. The order is important. In on case, calling the
// closure on the "starts humongous" region might de-allocate
// and clear all its "continues humongous" regions and, as a
// result, we might end up processing them twice. So, we'll do
// them first (notice: most closures will ignore them anyway) and
// then we'll do the "starts humongous" region.
for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
HeapRegion* chr = region_at(ch_index);
// if the region has already been claimed or it's not
// "continues humongous" we're done
if (chr->claim_value() == claim_value ||
!chr->continuesHumongous()) {
break;
}
// No one should have claimed it directly. We can given
// that we claimed its "starts humongous" region.
assert(chr->claim_value() != claim_value, "sanity");
assert(chr->humongous_start_region() == r, "sanity");
if (chr->claimHeapRegion(claim_value)) {
// we should always be able to claim it; no one else should
// be trying to claim this region
bool res2 = cl->doHeapRegion(chr);
assert(!res2, "Should not abort");
// Right now, this holds (i.e., no closure that actually
// does something with "continues humongous" regions
// clears them). We might have to weaken it in the future,
// but let's leave these two asserts here for extra safety.
assert(chr->continuesHumongous(), "should still be the case");
assert(chr->humongous_start_region() == r, "sanity");
} else {
guarantee(false, "we should not reach here");
}
}
}
assert(!r->continuesHumongous(), "sanity");
bool res = cl->doHeapRegion(r);
assert(!res, "Should not abort");
}
}
}
class ResetClaimValuesClosure: public HeapRegionClosure {
public:
bool doHeapRegion(HeapRegion* r) {
r->set_claim_value(HeapRegion::InitialClaimValue);
return false;
}
};
void G1CollectedHeap::reset_heap_region_claim_values() {
ResetClaimValuesClosure blk;
heap_region_iterate(&blk);
}
void G1CollectedHeap::reset_cset_heap_region_claim_values() {
ResetClaimValuesClosure blk;
collection_set_iterate(&blk);
}
#ifdef ASSERT
// This checks whether all regions in the heap have the correct claim
// value. I also piggy-backed on this a check to ensure that the
// humongous_start_region() information on "continues humongous"
// regions is correct.
class CheckClaimValuesClosure : public HeapRegionClosure {
private:
jint _claim_value;
uint _failures;
HeapRegion* _sh_region;
public:
CheckClaimValuesClosure(jint claim_value) :
_claim_value(claim_value), _failures(0), _sh_region(NULL) { }
bool doHeapRegion(HeapRegion* r) {
if (r->claim_value() != _claim_value) {
gclog_or_tty->print_cr("Region " HR_FORMAT ", "
"claim value = %d, should be %d",
HR_FORMAT_PARAMS(r),
r->claim_value(), _claim_value);
++_failures;
}
if (!r->isHumongous()) {
_sh_region = NULL;
} else if (r->startsHumongous()) {
_sh_region = r;
} else if (r->continuesHumongous()) {
if (r->humongous_start_region() != _sh_region) {
gclog_or_tty->print_cr("Region " HR_FORMAT ", "
"HS = "PTR_FORMAT", should be "PTR_FORMAT,
HR_FORMAT_PARAMS(r),
r->humongous_start_region(),
_sh_region);
++_failures;
}
}
return false;
}
uint failures() { return _failures; }
};
bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
CheckClaimValuesClosure cl(claim_value);
heap_region_iterate(&cl);
return cl.failures() == 0;
}
class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
private:
jint _claim_value;
uint _failures;
public:
CheckClaimValuesInCSetHRClosure(jint claim_value) :
_claim_value(claim_value), _failures(0) { }
uint failures() { return _failures; }
bool doHeapRegion(HeapRegion* hr) {
assert(hr->in_collection_set(), "how?");
assert(!hr->isHumongous(), "H-region in CSet");
if (hr->claim_value() != _claim_value) {
gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
"claim value = %d, should be %d",
HR_FORMAT_PARAMS(hr),
hr->claim_value(), _claim_value);
_failures += 1;
}
return false;
}
};
bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
CheckClaimValuesInCSetHRClosure cl(claim_value);
collection_set_iterate(&cl);
return cl.failures() == 0;
}
#endif // ASSERT
// Clear the cached CSet starting regions and (more importantly)
// the time stamps. Called when we reset the GC time stamp.
void G1CollectedHeap::clear_cset_start_regions() {
assert(_worker_cset_start_region != NULL, "sanity");
assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
int n_queues = MAX2((int)ParallelGCThreads, 1);
for (int i = 0; i < n_queues; i++) {
_worker_cset_start_region[i] = NULL;
_worker_cset_start_region_time_stamp[i] = 0;
}
}
// Given the id of a worker, obtain or calculate a suitable
// starting region for iterating over the current collection set.
HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
assert(get_gc_time_stamp() > 0, "should have been updated by now");
HeapRegion* result = NULL;
unsigned gc_time_stamp = get_gc_time_stamp();
if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
// Cached starting region for current worker was set
// during the current pause - so it's valid.
// Note: the cached starting heap region may be NULL
// (when the collection set is empty).
result = _worker_cset_start_region[worker_i];
assert(result == NULL || result->in_collection_set(), "sanity");
return result;
}
// The cached entry was not valid so let's calculate
// a suitable starting heap region for this worker.
// We want the parallel threads to start their collection
// set iteration at different collection set regions to
// avoid contention.
// If we have:
// n collection set regions
// p threads
// Then thread t will start at region floor ((t * n) / p)
result = g1_policy()->collection_set();
if (G1CollectedHeap::use_parallel_gc_threads()) {
uint cs_size = g1_policy()->cset_region_length();
uint active_workers = workers()->active_workers();
assert(UseDynamicNumberOfGCThreads ||
active_workers == workers()->total_workers(),
"Unless dynamic should use total workers");
uint end_ind = (cs_size * worker_i) / active_workers;
uint start_ind = 0;
if (worker_i > 0 &&
_worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
// Previous workers starting region is valid
// so let's iterate from there
start_ind = (cs_size * (worker_i - 1)) / active_workers;
result = _worker_cset_start_region[worker_i - 1];
}
for (uint i = start_ind; i < end_ind; i++) {
result = result->next_in_collection_set();
}
}
// Note: the calculated starting heap region may be NULL
// (when the collection set is empty).
assert(result == NULL || result->in_collection_set(), "sanity");
assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
"should be updated only once per pause");
_worker_cset_start_region[worker_i] = result;
OrderAccess::storestore();
_worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
return result;
}
HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
uint no_of_par_workers) {
uint worker_num =
G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
assert(UseDynamicNumberOfGCThreads ||
no_of_par_workers == workers()->total_workers(),
"Non dynamic should use fixed number of workers");
const uint start_index = n_regions() * worker_i / worker_num;
return region_at(start_index);
}
void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
HeapRegion* r = g1_policy()->collection_set();
while (r != NULL) {
HeapRegion* next = r->next_in_collection_set();
if (cl->doHeapRegion(r)) {
cl->incomplete();
return;
}
r = next;
}
}
void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
HeapRegionClosure *cl) {
if (r == NULL) {
// The CSet is empty so there's nothing to do.
return;
}
assert(r->in_collection_set(),
"Start region must be a member of the collection set.");
HeapRegion* cur = r;
while (cur != NULL) {
HeapRegion* next = cur->next_in_collection_set();
if (cl->doHeapRegion(cur) && false) {
cl->incomplete();
return;
}
cur = next;
}
cur = g1_policy()->collection_set();
while (cur != r) {
HeapRegion* next = cur->next_in_collection_set();
if (cl->doHeapRegion(cur) && false) {
cl->incomplete();
return;
}
cur = next;
}
}
CompactibleSpace* G1CollectedHeap::first_compactible_space() {
return n_regions() > 0 ? region_at(0) : NULL;
}
Space* G1CollectedHeap::space_containing(const void* addr) const {
Space* res = heap_region_containing(addr);
return res;
}
HeapWord* G1CollectedHeap::block_start(const void* addr) const {
Space* sp = space_containing(addr);
if (sp != NULL) {
return sp->block_start(addr);
}
return NULL;
}
size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
Space* sp = space_containing(addr);
assert(sp != NULL, "block_size of address outside of heap");
return sp->block_size(addr);
}
bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
Space* sp = space_containing(addr);
return sp->block_is_obj(addr);
}
bool G1CollectedHeap::supports_tlab_allocation() const {
return true;
}
size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
return HeapRegion::GrainBytes;
}
size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
// Return the remaining space in the cur alloc region, but not less than
// the min TLAB size.
// Also, this value can be at most the humongous object threshold,
// since we can't allow tlabs to grow big enough to accommodate
// humongous objects.
HeapRegion* hr = _mutator_alloc_region.get();
size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
if (hr == NULL) {
return max_tlab_size;
} else {
return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
}
}
size_t G1CollectedHeap::max_capacity() const {
return _g1_reserved.byte_size();
}
jlong G1CollectedHeap::millis_since_last_gc() {
// assert(false, "NYI");
return 0;
}
void G1CollectedHeap::prepare_for_verify() {
if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
ensure_parsability(false);
}
g1_rem_set()->prepare_for_verify();
}
bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
VerifyOption vo) {
switch (vo) {
case VerifyOption_G1UsePrevMarking:
return hr->obj_allocated_since_prev_marking(obj);
case VerifyOption_G1UseNextMarking:
return hr->obj_allocated_since_next_marking(obj);
case VerifyOption_G1UseMarkWord:
return false;
default:
ShouldNotReachHere();
}
return false; // keep some compilers happy
}
HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
switch (vo) {
case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
case VerifyOption_G1UseMarkWord: return NULL;
default: ShouldNotReachHere();
}
return NULL; // keep some compilers happy
}
bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
switch (vo) {
case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
default: ShouldNotReachHere();
}
return false; // keep some compilers happy
}
const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
switch (vo) {
case VerifyOption_G1UsePrevMarking: return "PTAMS";
case VerifyOption_G1UseNextMarking: return "NTAMS";
case VerifyOption_G1UseMarkWord: return "NONE";
default: ShouldNotReachHere();
}
return NULL; // keep some compilers happy
}
// TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
// pass it as the perm_blk to SharedHeap::process_strong_roots.
// When process_strong_roots stop calling perm_blk->younger_refs_iterate
// we can change this closure to extend the simpler OopClosure.
class VerifyRootsClosure: public OopsInGenClosure {
private:
G1CollectedHeap* _g1h;
VerifyOption _vo;
bool _failures;
public:
// _vo == UsePrevMarking -> use "prev" marking information,
// _vo == UseNextMarking -> use "next" marking information,
// _vo == UseMarkWord -> use mark word from object header.
VerifyRootsClosure(VerifyOption vo) :
_g1h(G1CollectedHeap::heap()),
_vo(vo),
_failures(false) { }
bool failures() { return _failures; }
template <class T> void do_oop_nv(T* p) {
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
if (_g1h->is_obj_dead_cond(obj, _vo)) {
gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
"points to dead obj "PTR_FORMAT, p, (void*) obj);
if (_vo == VerifyOption_G1UseMarkWord) {
gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
}
obj->print_on(gclog_or_tty);
_failures = true;
}
}
}
void do_oop(oop* p) { do_oop_nv(p); }
void do_oop(narrowOop* p) { do_oop_nv(p); }
};
class G1VerifyCodeRootOopClosure: public OopsInGenClosure {
G1CollectedHeap* _g1h;
OopClosure* _root_cl;
nmethod* _nm;
VerifyOption _vo;
bool _failures;
template <class T> void do_oop_work(T* p) {
// First verify that this root is live
_root_cl->do_oop(p);
if (!G1VerifyHeapRegionCodeRoots) {
// We're not verifying the code roots attached to heap region.
return;
}
// Don't check the code roots during marking verification in a full GC
if (_vo == VerifyOption_G1UseMarkWord) {
return;
}
// Now verify that the current nmethod (which contains p) is
// in the code root list of the heap region containing the
// object referenced by p.
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
// Now fetch the region containing the object
HeapRegion* hr = _g1h->heap_region_containing(obj);
HeapRegionRemSet* hrrs = hr->rem_set();
// Verify that the strong code root list for this region
// contains the nmethod
if (!hrrs->strong_code_roots_list_contains(_nm)) {
gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
"from nmethod "PTR_FORMAT" not in strong "
"code roots for region ["PTR_FORMAT","PTR_FORMAT")",
p, _nm, hr->bottom(), hr->end());
_failures = true;
}
}
}
public:
G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
_g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
void do_oop(oop* p) { do_oop_work(p); }
void do_oop(narrowOop* p) { do_oop_work(p); }
void set_nmethod(nmethod* nm) { _nm = nm; }
bool failures() { return _failures; }
};
class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
G1VerifyCodeRootOopClosure* _oop_cl;
public:
G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
_oop_cl(oop_cl) {}
void do_code_blob(CodeBlob* cb) {
nmethod* nm = cb->as_nmethod_or_null();
if (nm != NULL) {
_oop_cl->set_nmethod(nm);
nm->oops_do(_oop_cl);
}
}
};
class YoungRefCounterClosure : public OopClosure {
G1CollectedHeap* _g1h;
int _count;
public:
YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
void do_oop(narrowOop* p) { ShouldNotReachHere(); }
int count() { return _count; }
void reset_count() { _count = 0; };
};
class VerifyKlassClosure: public KlassClosure {
YoungRefCounterClosure _young_ref_counter_closure;
OopClosure *_oop_closure;
public:
VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
void do_klass(Klass* k) {
k->oops_do(_oop_closure);
_young_ref_counter_closure.reset_count();
k->oops_do(&_young_ref_counter_closure);
if (_young_ref_counter_closure.count() > 0) {
guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
}
}
};
class VerifyLivenessOopClosure: public OopClosure {
G1CollectedHeap* _g1h;
VerifyOption _vo;
public:
VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
_g1h(g1h), _vo(vo)
{ }
void do_oop(narrowOop *p) { do_oop_work(p); }
void do_oop( oop *p) { do_oop_work(p); }
template <class T> void do_oop_work(T *p) {
oop obj = oopDesc::load_decode_heap_oop(p);
guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
"Dead object referenced by a not dead object");
}
};
class VerifyObjsInRegionClosure: public ObjectClosure {
private:
G1CollectedHeap* _g1h;
size_t _live_bytes;
HeapRegion *_hr;
VerifyOption _vo;
public:
// _vo == UsePrevMarking -> use "prev" marking information,
// _vo == UseNextMarking -> use "next" marking information,
// _vo == UseMarkWord -> use mark word from object header.
VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
: _live_bytes(0), _hr(hr), _vo(vo) {
_g1h = G1CollectedHeap::heap();
}
void do_object(oop o) {
VerifyLivenessOopClosure isLive(_g1h, _vo);
assert(o != NULL, "Huh?");
if (!_g1h->is_obj_dead_cond(o, _vo)) {
// If the object is alive according to the mark word,
// then verify that the marking information agrees.
// Note we can't verify the contra-positive of the
// above: if the object is dead (according to the mark
// word), it may not be marked, or may have been marked
// but has since became dead, or may have been allocated
// since the last marking.
if (_vo == VerifyOption_G1UseMarkWord) {
guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
}
o->oop_iterate_no_header(&isLive);
if (!_hr->obj_allocated_since_prev_marking(o)) {
size_t obj_size = o->size(); // Make sure we don't overflow
_live_bytes += (obj_size * HeapWordSize);
}
}
}
size_t live_bytes() { return _live_bytes; }
};
class PrintObjsInRegionClosure : public ObjectClosure {
HeapRegion *_hr;
G1CollectedHeap *_g1;
public:
PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
_g1 = G1CollectedHeap::heap();
};
void do_object(oop o) {
if (o != NULL) {
HeapWord *start = (HeapWord *) o;
size_t word_sz = o->size();
gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
" isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
(void*) o, word_sz,
_g1->isMarkedPrev(o),
_g1->isMarkedNext(o),
_hr->obj_allocated_since_prev_marking(o));
HeapWord *end = start + word_sz;
HeapWord *cur;
int *val;
for (cur = start; cur < end; cur++) {
val = (int *) cur;
gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
}
}
}
};
class VerifyRegionClosure: public HeapRegionClosure {
private:
bool _par;
VerifyOption _vo;
bool _failures;
public:
// _vo == UsePrevMarking -> use "prev" marking information,
// _vo == UseNextMarking -> use "next" marking information,
// _vo == UseMarkWord -> use mark word from object header.
VerifyRegionClosure(bool par, VerifyOption vo)
: _par(par),
_vo(vo),
_failures(false) {}
bool failures() {
return _failures;
}
bool doHeapRegion(HeapRegion* r) {
if (!r->continuesHumongous()) {
bool failures = false;
r->verify(_vo, &failures);
if (failures) {
_failures = true;
} else {
VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
r->object_iterate(¬_dead_yet_cl);
if (_vo != VerifyOption_G1UseNextMarking) {
if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
"max_live_bytes "SIZE_FORMAT" "
"< calculated "SIZE_FORMAT,
r->bottom(), r->end(),
r->max_live_bytes(),
not_dead_yet_cl.live_bytes());
_failures = true;
}
} else {
// When vo == UseNextMarking we cannot currently do a sanity
// check on the live bytes as the calculation has not been
// finalized yet.
}
}
}
return false; // stop the region iteration if we hit a failure
}
};
// This is the task used for parallel verification of the heap regions
class G1ParVerifyTask: public AbstractGangTask {
private:
G1CollectedHeap* _g1h;
VerifyOption _vo;
bool _failures;
public:
// _vo == UsePrevMarking -> use "prev" marking information,
// _vo == UseNextMarking -> use "next" marking information,
// _vo == UseMarkWord -> use mark word from object header.
G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
AbstractGangTask("Parallel verify task"),
_g1h(g1h),
_vo(vo),
_failures(false) { }
bool failures() {
return _failures;
}
void work(uint worker_id) {
HandleMark hm;
VerifyRegionClosure blk(true, _vo);
_g1h->heap_region_par_iterate_chunked(&blk, worker_id,
_g1h->workers()->active_workers(),
HeapRegion::ParVerifyClaimValue);
if (blk.failures()) {
_failures = true;
}
}
};
void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
if (SafepointSynchronize::is_at_safepoint()) {
assert(Thread::current()->is_VM_thread(),
"Expected to be executed serially by the VM thread at this point");
if (!silent) { gclog_or_tty->print("Roots "); }
VerifyRootsClosure rootsCl(vo);
G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
VerifyKlassClosure klassCl(this, &rootsCl);
// We apply the relevant closures to all the oops in the
// system dictionary, the string table and the code cache.
const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
// Need cleared claim bits for the strong roots processing
ClassLoaderDataGraph::clear_claimed_marks();
process_strong_roots(true, // activate StrongRootsScope
false, // we set "is scavenging" to false,
// so we don't reset the dirty cards.
ScanningOption(so), // roots scanning options
&rootsCl,
&blobsCl,
&klassCl
);
bool failures = rootsCl.failures() || codeRootsCl.failures();
if (vo != VerifyOption_G1UseMarkWord) {
// If we're verifying during a full GC then the region sets
// will have been torn down at the start of the GC. Therefore
// verifying the region sets will fail. So we only verify
// the region sets when not in a full GC.
if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
verify_region_sets();
}
if (!silent) { gclog_or_tty->print("HeapRegions "); }
if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
"sanity check");
G1ParVerifyTask task(this, vo);
assert(UseDynamicNumberOfGCThreads ||
workers()->active_workers() == workers()->total_workers(),
"If not dynamic should be using all the workers");
int n_workers = workers()->active_workers();
set_par_threads(n_workers);
workers()->run_task(&task);
set_par_threads(0);
if (task.failures()) {
failures = true;
}
// Checks that the expected amount of parallel work was done.
// The implication is that n_workers is > 0.
assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
"sanity check");
reset_heap_region_claim_values();
assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
"sanity check");
} else {
VerifyRegionClosure blk(false, vo);
heap_region_iterate(&blk);
if (blk.failures()) {
failures = true;
}
}
if (!silent) gclog_or_tty->print("RemSet ");
rem_set()->verify();
if (failures) {
gclog_or_tty->print_cr("Heap:");
// It helps to have the per-region information in the output to
// help us track down what went wrong. This is why we call
// print_extended_on() instead of print_on().
print_extended_on(gclog_or_tty);
gclog_or_tty->print_cr("");
#ifndef PRODUCT
if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
concurrent_mark()->print_reachable("at-verification-failure",
vo, false /* all */);
}
#endif
gclog_or_tty->flush();
}
guarantee(!failures, "there should not have been any failures");
} else {
if (!silent)
gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) ");
}
}
void G1CollectedHeap::verify(bool silent) {
verify(silent, VerifyOption_G1UsePrevMarking);
}
double G1CollectedHeap::verify(bool guard, const char* msg) {
double verify_time_ms = 0.0;
if (guard && total_collections() >= VerifyGCStartAt) {
double verify_start = os::elapsedTime();
HandleMark hm; // Discard invalid handles created during verification
prepare_for_verify();
Universe::verify(VerifyOption_G1UsePrevMarking, msg);
verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
}
return verify_time_ms;
}
void G1CollectedHeap::verify_before_gc() {
double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
}
void G1CollectedHeap::verify_after_gc() {
double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
}
class PrintRegionClosure: public HeapRegionClosure {
outputStream* _st;
public:
PrintRegionClosure(outputStream* st) : _st(st) {}
bool doHeapRegion(HeapRegion* r) {
r->print_on(_st);
return false;
}
};
void G1CollectedHeap::print_on(outputStream* st) const {
st->print(" %-20s", "garbage-first heap");
st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
capacity()/K, used_unlocked()/K);
st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
_g1_storage.low_boundary(),
_g1_storage.high(),
_g1_storage.high_boundary());
st->cr();
st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
uint young_regions = _young_list->length();
st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
(size_t) young_regions * HeapRegion::GrainBytes / K);
uint survivor_regions = g1_policy()->recorded_survivor_regions();
st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
(size_t) survivor_regions * HeapRegion::GrainBytes / K);
st->cr();
MetaspaceAux::print_on(st);
}
void G1CollectedHeap::print_extended_on(outputStream* st) const {
print_on(st);
// Print the per-region information.
st->cr();
st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
"HS=humongous(starts), HC=humongous(continues), "
"CS=collection set, F=free, TS=gc time stamp, "
"PTAMS=previous top-at-mark-start, "
"NTAMS=next top-at-mark-start)");
PrintRegionClosure blk(st);
heap_region_iterate(&blk);
}
void G1CollectedHeap::print_on_error(outputStream* st) const {
this->CollectedHeap::print_on_error(st);
if (_cm != NULL) {
st->cr();
_cm->print_on_error(st);
}
}
void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
if (G1CollectedHeap::use_parallel_gc_threads()) {
workers()->print_worker_threads_on(st);
}
_cmThread->print_on(st);
st->cr();
_cm->print_worker_threads_on(st);
_cg1r->print_worker_threads_on(st);
}
void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
if (G1CollectedHeap::use_parallel_gc_threads()) {
workers()->threads_do(tc);
}
tc->do_thread(_cmThread);
_cg1r->threads_do(tc);
}
void G1CollectedHeap::print_tracing_info() const {
// We'll overload this to mean "trace GC pause statistics."
if (TraceGen0Time || TraceGen1Time) {
// The "G1CollectorPolicy" is keeping track of these stats, so delegate
// to that.
g1_policy()->print_tracing_info();
}
if (G1SummarizeRSetStats) {
g1_rem_set()->print_summary_info();
}
if (G1SummarizeConcMark) {
concurrent_mark()->print_summary_info();
}
g1_policy()->print_yg_surv_rate_info();
SpecializationStats::print();
}
#ifndef PRODUCT
// Helpful for debugging RSet issues.
class PrintRSetsClosure : public HeapRegionClosure {
private:
const char* _msg;
size_t _occupied_sum;
public:
bool doHeapRegion(HeapRegion* r) {
HeapRegionRemSet* hrrs = r->rem_set();
size_t occupied = hrrs->occupied();
_occupied_sum += occupied;
gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
HR_FORMAT_PARAMS(r));
if (occupied == 0) {
gclog_or_tty->print_cr(" RSet is empty");
} else {
hrrs->print();
}
gclog_or_tty->print_cr("----------");
return false;
}
PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
gclog_or_tty->cr();
gclog_or_tty->print_cr("========================================");
gclog_or_tty->print_cr(msg);
gclog_or_tty->cr();
}
~PrintRSetsClosure() {
gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
gclog_or_tty->print_cr("========================================");
gclog_or_tty->cr();
}
};
void G1CollectedHeap::print_cset_rsets() {
PrintRSetsClosure cl("Printing CSet RSets");
collection_set_iterate(&cl);
}
void G1CollectedHeap::print_all_rsets() {
PrintRSetsClosure cl("Printing All RSets");;
heap_region_iterate(&cl);
}
#endif // PRODUCT
G1CollectedHeap* G1CollectedHeap::heap() {
assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
"not a garbage-first heap");
return _g1h;
}
void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
// always_do_update_barrier = false;
assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
// Fill TLAB's and such
ensure_parsability(true);
}
void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
if (G1SummarizeRSetStats &&
(G1SummarizeRSetStatsPeriod > 0) &&
// we are at the end of the GC. Total collections has already been increased.
((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
g1_rem_set()->print_periodic_summary_info();
}
// FIXME: what is this about?
// I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
// is set.
COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
"derived pointer present"));
// always_do_update_barrier = true;
// We have just completed a GC. Update the soft reference
// policy with the new heap occupancy
Universe::update_heap_info_at_gc();
}
HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
unsigned int gc_count_before,
bool* succeeded) {
assert_heap_not_locked_and_not_at_safepoint();
g1_policy()->record_stop_world_start();
VM_G1IncCollectionPause op(gc_count_before,
word_size,
false, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
GCCause::_g1_inc_collection_pause);
VMThread::execute(&op);
HeapWord* result = op.result();
bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
assert(result == NULL || ret_succeeded,
"the result should be NULL if the VM did not succeed");
*succeeded = ret_succeeded;
assert_heap_not_locked();
return result;
}
void
G1CollectedHeap::doConcurrentMark() {
MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
if (!_cmThread->in_progress()) {
_cmThread->set_started();
CGC_lock->notify();
}
}
size_t G1CollectedHeap::pending_card_num() {
size_t extra_cards = 0;
JavaThread *curr = Threads::first();
while (curr != NULL) {
DirtyCardQueue& dcq = curr->dirty_card_queue();
extra_cards += dcq.size();
curr = curr->next();
}
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
size_t buffer_size = dcqs.buffer_size();
size_t buffer_num = dcqs.completed_buffers_num();
// PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
// in bytes - not the number of 'entries'. We need to convert
// into a number of cards.
return (buffer_size * buffer_num + extra_cards) / oopSize;
}
size_t G1CollectedHeap::cards_scanned() {
return g1_rem_set()->cardsScanned();
}
void
G1CollectedHeap::setup_surviving_young_words() {
assert(_surviving_young_words == NULL, "pre-condition");
uint array_length = g1_policy()->young_cset_region_length();
_surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
if (_surviving_young_words == NULL) {
vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
"Not enough space for young surv words summary.");
}
memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
#ifdef ASSERT
for (uint i = 0; i < array_length; ++i) {
assert( _surviving_young_words[i] == 0, "memset above" );
}
#endif // !ASSERT
}
void
G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
uint array_length = g1_policy()->young_cset_region_length();
for (uint i = 0; i < array_length; ++i) {
_surviving_young_words[i] += surv_young_words[i];
}
}
void
G1CollectedHeap::cleanup_surviving_young_words() {
guarantee( _surviving_young_words != NULL, "pre-condition" );
FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
_surviving_young_words = NULL;
}
#ifdef ASSERT
class VerifyCSetClosure: public HeapRegionClosure {
public:
bool doHeapRegion(HeapRegion* hr) {
// Here we check that the CSet region's RSet is ready for parallel
// iteration. The fields that we'll verify are only manipulated
// when the region is part of a CSet and is collected. Afterwards,
// we reset these fields when we clear the region's RSet (when the
// region is freed) so they are ready when the region is
// re-allocated. The only exception to this is if there's an
// evacuation failure and instead of freeing the region we leave
// it in the heap. In that case, we reset these fields during
// evacuation failure handling.
guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
// Here's a good place to add any other checks we'd like to
// perform on CSet regions.
return false;
}
};
#endif // ASSERT
#if TASKQUEUE_STATS
void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
st->print_raw_cr("GC Task Stats");
st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
}
void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
print_taskqueue_stats_hdr(st);
TaskQueueStats totals;
const int n = workers() != NULL ? workers()->total_workers() : 1;
for (int i = 0; i < n; ++i) {
st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
totals += task_queue(i)->stats;
}
st->print_raw("tot "); totals.print(st); st->cr();
DEBUG_ONLY(totals.verify());
}
void G1CollectedHeap::reset_taskqueue_stats() {
const int n = workers() != NULL ? workers()->total_workers() : 1;
for (int i = 0; i < n; ++i) {
task_queue(i)->stats.reset();
}
}
#endif // TASKQUEUE_STATS
void G1CollectedHeap::log_gc_header() {
if (!G1Log::fine()) {
return;
}
gclog_or_tty->date_stamp(PrintGCDateStamps);
gclog_or_tty->stamp(PrintGCTimeStamps);
GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
.append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
.append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
gclog_or_tty->print("[%s", (const char*)gc_cause_str);
}
void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
if (!G1Log::fine()) {
return;
}
if (G1Log::finer()) {
if (evacuation_failed()) {
gclog_or_tty->print(" (to-space exhausted)");
}
gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
g1_policy()->phase_times()->note_gc_end();
g1_policy()->phase_times()->print(pause_time_sec);
g1_policy()->print_detailed_heap_transition();
} else {
if (evacuation_failed()) {
gclog_or_tty->print("--");
}
g1_policy()->print_heap_transition();
gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
}
gclog_or_tty->flush();
}
bool
G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
assert_at_safepoint(true /* should_be_vm_thread */);
guarantee(!is_gc_active(), "collection is not reentrant");
if (GC_locker::check_active_before_gc()) {
return false;
}
_gc_timer_stw->register_gc_start(os::elapsed_counter());
_gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
SvcGCMarker sgcm(SvcGCMarker::MINOR);
ResourceMark rm;
print_heap_before_gc();
trace_heap_before_gc(_gc_tracer_stw);
HRSPhaseSetter x(HRSPhaseEvacuation);
verify_region_sets_optional();
verify_dirty_young_regions();
// This call will decide whether this pause is an initial-mark
// pause. If it is, during_initial_mark_pause() will return true
// for the duration of this pause.
g1_policy()->decide_on_conc_mark_initiation();
// We do not allow initial-mark to be piggy-backed on a mixed GC.
assert(!g1_policy()->during_initial_mark_pause() ||
g1_policy()->gcs_are_young(), "sanity");
// We also do not allow mixed GCs during marking.
assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
// Record whether this pause is an initial mark. When the current
// thread has completed its logging output and it's safe to signal
// the CM thread, the flag's value in the policy has been reset.
bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
// Inner scope for scope based logging, timers, and stats collection
{
EvacuationInfo evacuation_info;
if (g1_policy()->during_initial_mark_pause()) {
// We are about to start a marking cycle, so we increment the
// full collection counter.
increment_old_marking_cycles_started();
register_concurrent_cycle_start(_gc_timer_stw->gc_start());
}
_gc_tracer_stw->report_yc_type(yc_type());
TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
workers()->active_workers() : 1);
double pause_start_sec = os::elapsedTime();
g1_policy()->phase_times()->note_gc_start(active_workers);
log_gc_header();
TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
// If the secondary_free_list is not empty, append it to the
// free_list. No need to wait for the cleanup operation to finish;
// the region allocation code will check the secondary_free_list
// and wait if necessary. If the G1StressConcRegionFreeing flag is
// set, skip this step so that the region allocation code has to
// get entries from the secondary_free_list.
if (!G1StressConcRegionFreeing) {
append_secondary_free_list_if_not_empty_with_lock();
}
assert(check_young_list_well_formed(), "young list should be well formed");
assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
"sanity check");
// Don't dynamically change the number of GC threads this early. A value of
// 0 is used to indicate serial work. When parallel work is done,
// it will be set.
{ // Call to jvmpi::post_class_unload_events must occur outside of active GC
IsGCActiveMark x;
gc_prologue(false);
increment_total_collections(false /* full gc */);
increment_gc_time_stamp();
verify_before_gc();
COMPILER2_PRESENT(DerivedPointerTable::clear());
// Please see comment in g1CollectedHeap.hpp and
// G1CollectedHeap::ref_processing_init() to see how
// reference processing currently works in G1.
// Enable discovery in the STW reference processor
ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
true /*verify_no_refs*/);
{
// We want to temporarily turn off discovery by the
// CM ref processor, if necessary, and turn it back on
// on again later if we do. Using a scoped
// NoRefDiscovery object will do this.
NoRefDiscovery no_cm_discovery(ref_processor_cm());
// Forget the current alloc region (we might even choose it to be part
// of the collection set!).
release_mutator_alloc_region();
// We should call this after we retire the mutator alloc
// region(s) so that all the ALLOC / RETIRE events are generated
// before the start GC event.
_hr_printer.start_gc(false /* full */, (size_t) total_collections());
// This timing is only used by the ergonomics to handle our pause target.
// It is unclear why this should not include the full pause. We will
// investigate this in CR 7178365.
//
// Preserving the old comment here if that helps the investigation:
//
// The elapsed time induced by the start time below deliberately elides
// the possible verification above.
double sample_start_time_sec = os::elapsedTime();
#if YOUNG_LIST_VERBOSE
gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
_young_list->print();
g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
#endif // YOUNG_LIST_VERBOSE
g1_policy()->record_collection_pause_start(sample_start_time_sec);
double scan_wait_start = os::elapsedTime();
// We have to wait until the CM threads finish scanning the
// root regions as it's the only way to ensure that all the
// objects on them have been correctly scanned before we start
// moving them during the GC.
bool waited = _cm->root_regions()->wait_until_scan_finished();
double wait_time_ms = 0.0;
if (waited) {
double scan_wait_end = os::elapsedTime();
wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
}
g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
#if YOUNG_LIST_VERBOSE
gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
_young_list->print();
#endif // YOUNG_LIST_VERBOSE
if (g1_policy()->during_initial_mark_pause()) {
concurrent_mark()->checkpointRootsInitialPre();
}
#if YOUNG_LIST_VERBOSE
gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
_young_list->print();
g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
#endif // YOUNG_LIST_VERBOSE
g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
_cm->note_start_of_gc();
// We should not verify the per-thread SATB buffers given that
// we have not filtered them yet (we'll do so during the
// GC). We also call this after finalize_cset() to
// ensure that the CSet has been finalized.
_cm->verify_no_cset_oops(true /* verify_stacks */,
true /* verify_enqueued_buffers */,
false /* verify_thread_buffers */,
true /* verify_fingers */);
if (_hr_printer.is_active()) {
HeapRegion* hr = g1_policy()->collection_set();
while (hr != NULL) {
G1HRPrinter::RegionType type;
if (!hr->is_young()) {
type = G1HRPrinter::Old;
} else if (hr->is_survivor()) {
type = G1HRPrinter::Survivor;
} else {
type = G1HRPrinter::Eden;
}
_hr_printer.cset(hr);
hr = hr->next_in_collection_set();
}
}
#ifdef ASSERT
VerifyCSetClosure cl;
collection_set_iterate(&cl);
#endif // ASSERT
setup_surviving_young_words();
// Initialize the GC alloc regions.
init_gc_alloc_regions(evacuation_info);
// Actually do the work...
evacuate_collection_set(evacuation_info);
// We do this to mainly verify the per-thread SATB buffers
// (which have been filtered by now) since we didn't verify
// them earlier. No point in re-checking the stacks / enqueued
// buffers given that the CSet has not changed since last time
// we checked.
_cm->verify_no_cset_oops(false /* verify_stacks */,
false /* verify_enqueued_buffers */,
true /* verify_thread_buffers */,
true /* verify_fingers */);
free_collection_set(g1_policy()->collection_set(), evacuation_info);
g1_policy()->clear_collection_set();
cleanup_surviving_young_words();
// Start a new incremental collection set for the next pause.
g1_policy()->start_incremental_cset_building();
// Clear the _cset_fast_test bitmap in anticipation of adding
// regions to the incremental collection set for the next
// evacuation pause.
clear_cset_fast_test();
_young_list->reset_sampled_info();
// Don't check the whole heap at this point as the
// GC alloc regions from this pause have been tagged
// as survivors and moved on to the survivor list.
// Survivor regions will fail the !is_young() check.
assert(check_young_list_empty(false /* check_heap */),
"young list should be empty");
#if YOUNG_LIST_VERBOSE
gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
_young_list->print();
#endif // YOUNG_LIST_VERBOSE
g1_policy()->record_survivor_regions(_young_list->survivor_length(),
_young_list->first_survivor_region(),
_young_list->last_survivor_region());
_young_list->reset_auxilary_lists();
if (evacuation_failed()) {
_summary_bytes_used = recalculate_used();
uint n_queues = MAX2((int)ParallelGCThreads, 1);
for (uint i = 0; i < n_queues; i++) {
if (_evacuation_failed_info_array[i].has_failed()) {
_gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
}
}
} else {
// The "used" of the the collection set have already been subtracted
// when they were freed. Add in the bytes evacuated.
_summary_bytes_used += g1_policy()->bytes_copied_during_gc();
}
if (g1_policy()->during_initial_mark_pause()) {
// We have to do this before we notify the CM threads that
// they can start working to make sure that all the
// appropriate initialization is done on the CM object.
concurrent_mark()->checkpointRootsInitialPost();
set_marking_started();
// Note that we don't actually trigger the CM thread at
// this point. We do that later when we're sure that
// the current thread has completed its logging output.
}
allocate_dummy_regions();
#if YOUNG_LIST_VERBOSE
gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
_young_list->print();
g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
#endif // YOUNG_LIST_VERBOSE
init_mutator_alloc_region();
{
size_t expand_bytes = g1_policy()->expansion_amount();
if (expand_bytes > 0) {
size_t bytes_before = capacity();
// No need for an ergo verbose message here,
// expansion_amount() does this when it returns a value > 0.
if (!expand(expand_bytes)) {
// We failed to expand the heap so let's verify that
// committed/uncommitted amount match the backing store
assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
}
}
}
// We redo the verification but now wrt to the new CSet which
// has just got initialized after the previous CSet was freed.
_cm->verify_no_cset_oops(true /* verify_stacks */,
true /* verify_enqueued_buffers */,
true /* verify_thread_buffers */,
true /* verify_fingers */);
_cm->note_end_of_gc();
// This timing is only used by the ergonomics to handle our pause target.
// It is unclear why this should not include the full pause. We will
// investigate this in CR 7178365.
double sample_end_time_sec = os::elapsedTime();
double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
MemoryService::track_memory_usage();
// In prepare_for_verify() below we'll need to scan the deferred
// update buffers to bring the RSets up-to-date if
// G1HRRSFlushLogBuffersOnVerify has been set. While scanning
// the update buffers we'll probably need to scan cards on the
// regions we just allocated to (i.e., the GC alloc
// regions). However, during the last GC we called
// set_saved_mark() on all the GC alloc regions, so card
// scanning might skip the [saved_mark_word()...top()] area of
// those regions (i.e., the area we allocated objects into
// during the last GC). But it shouldn't. Given that
// saved_mark_word() is conditional on whether the GC time stamp
// on the region is current or not, by incrementing the GC time
// stamp here we invalidate all the GC time stamps on all the
// regions and saved_mark_word() will simply return top() for
// all the regions. This is a nicer way of ensuring this rather
// than iterating over the regions and fixing them. In fact, the
// GC time stamp increment here also ensures that
// saved_mark_word() will return top() between pauses, i.e.,
// during concurrent refinement. So we don't need the
// is_gc_active() check to decided which top to use when
// scanning cards (see CR 7039627).
increment_gc_time_stamp();
verify_after_gc();
assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
ref_processor_stw()->verify_no_references_recorded();
// CM reference discovery will be re-enabled if necessary.
}
// We should do this after we potentially expand the heap so
// that all the COMMIT events are generated before the end GC
// event, and after we retire the GC alloc regions so that all
// RETIRE events are generated before the end GC event.
_hr_printer.end_gc(false /* full */, (size_t) total_collections());
if (mark_in_progress()) {
concurrent_mark()->update_g1_committed();
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
gc_epilogue(false);
}
// Print the remainder of the GC log output.
log_gc_footer(os::elapsedTime() - pause_start_sec);
// It is not yet to safe to tell the concurrent mark to
// start as we have some optional output below. We don't want the
// output from the concurrent mark thread interfering with this
// logging output either.
_hrs.verify_optional();
verify_region_sets_optional();
TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
print_heap_after_gc();
trace_heap_after_gc(_gc_tracer_stw);
// We must call G1MonitoringSupport::update_sizes() in the same scoping level
// as an active TraceMemoryManagerStats object (i.e. before the destructor for the
// TraceMemoryManagerStats is called) so that the G1 memory pools are updated
// before any GC notifications are raised.
g1mm()->update_sizes();
_gc_tracer_stw->report_evacuation_info(&evacuation_info);
_gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
_gc_timer_stw->register_gc_end(os::elapsed_counter());
_gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
}
// It should now be safe to tell the concurrent mark thread to start
// without its logging output interfering with the logging output
// that came from the pause.
if (should_start_conc_mark) {
// CAUTION: after the doConcurrentMark() call below,
// the concurrent marking thread(s) could be running
// concurrently with us. Make sure that anything after
// this point does not assume that we are the only GC thread
// running. Note: of course, the actual marking work will
// not start until the safepoint itself is released in
// ConcurrentGCThread::safepoint_desynchronize().
doConcurrentMark();
}
return true;
}
size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
{
size_t gclab_word_size;
switch (purpose) {
case GCAllocForSurvived:
gclab_word_size = _survivor_plab_stats.desired_plab_sz();
break;
case GCAllocForTenured:
gclab_word_size = _old_plab_stats.desired_plab_sz();
break;
default:
assert(false, "unknown GCAllocPurpose");
gclab_word_size = _old_plab_stats.desired_plab_sz();
break;
}
// Prevent humongous PLAB sizes for two reasons:
// * PLABs are allocated using a similar paths as oops, but should
// never be in a humongous region
// * Allowing humongous PLABs needlessly churns the region free lists
return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
}
void G1CollectedHeap::init_mutator_alloc_region() {
assert(_mutator_alloc_region.get() == NULL, "pre-condition");
_mutator_alloc_region.init();
}
void G1CollectedHeap::release_mutator_alloc_region() {
_mutator_alloc_region.release();
assert(_mutator_alloc_region.get() == NULL, "post-condition");
}
void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
assert_at_safepoint(true /* should_be_vm_thread */);
_survivor_gc_alloc_region.init();
_old_gc_alloc_region.init();
HeapRegion* retained_region = _retained_old_gc_alloc_region;
_retained_old_gc_alloc_region = NULL;
// We will discard the current GC alloc region if:
// a) it's in the collection set (it can happen!),
// b) it's already full (no point in using it),
// c) it's empty (this means that it was emptied during
// a cleanup and it should be on the free list now), or
// d) it's humongous (this means that it was emptied
// during a cleanup and was added to the free list, but
// has been subsequently used to allocate a humongous
// object that may be less than the region size).
if (retained_region != NULL &&
!retained_region->in_collection_set() &&
!(retained_region->top() == retained_region->end()) &&
!retained_region->is_empty() &&
!retained_region->isHumongous()) {
retained_region->set_saved_mark();
// The retained region was added to the old region set when it was
// retired. We have to remove it now, since we don't allow regions
// we allocate to in the region sets. We'll re-add it later, when
// it's retired again.
_old_set.remove(retained_region);
bool during_im = g1_policy()->during_initial_mark_pause();
retained_region->note_start_of_copying(during_im);
_old_gc_alloc_region.set(retained_region);
_hr_printer.reuse(retained_region);
evacuation_info.set_alloc_regions_used_before(retained_region->used());
}
}
void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
_old_gc_alloc_region.count());
_survivor_gc_alloc_region.release();
// If we have an old GC alloc region to release, we'll save it in
// _retained_old_gc_alloc_region. If we don't
// _retained_old_gc_alloc_region will become NULL. This is what we
// want either way so no reason to check explicitly for either
// condition.
_retained_old_gc_alloc_region = _old_gc_alloc_region.release();
if (ResizePLAB) {
_survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
_old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
}
}
void G1CollectedHeap::abandon_gc_alloc_regions() {
assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
_retained_old_gc_alloc_region = NULL;
}
void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
_drain_in_progress = false;
set_evac_failure_closure(cl);
_evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
}
void G1CollectedHeap::finalize_for_evac_failure() {
assert(_evac_failure_scan_stack != NULL &&
_evac_failure_scan_stack->length() == 0,
"Postcondition");
assert(!_drain_in_progress, "Postcondition");
delete _evac_failure_scan_stack;
_evac_failure_scan_stack = NULL;
}
void G1CollectedHeap::remove_self_forwarding_pointers() {
assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
if (G1CollectedHeap::use_parallel_gc_threads()) {
set_par_threads();
workers()->run_task(&rsfp_task);
set_par_threads(0);
} else {
rsfp_task.work(0);
}
assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
// Reset the claim values in the regions in the collection set.
reset_cset_heap_region_claim_values();
assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
// Now restore saved marks, if any.
assert(_objs_with_preserved_marks.size() ==
_preserved_marks_of_objs.size(), "Both or none.");
while (!_objs_with_preserved_marks.is_empty()) {
oop obj = _objs_with_preserved_marks.pop();
markOop m = _preserved_marks_of_objs.pop();
obj->set_mark(m);
}
_objs_with_preserved_marks.clear(true);
_preserved_marks_of_objs.clear(true);
}
void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
_evac_failure_scan_stack->push(obj);
}
void G1CollectedHeap::drain_evac_failure_scan_stack() {
assert(_evac_failure_scan_stack != NULL, "precondition");
while (_evac_failure_scan_stack->length() > 0) {
oop obj = _evac_failure_scan_stack->pop();
_evac_failure_closure->set_region(heap_region_containing(obj));
obj->oop_iterate_backwards(_evac_failure_closure);
}
}
oop
G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
oop old) {
assert(obj_in_cs(old),
err_msg("obj: "PTR_FORMAT" should still be in the CSet",
(HeapWord*) old));
markOop m = old->mark();
oop forward_ptr = old->forward_to_atomic(old);
if (forward_ptr == NULL) {
// Forward-to-self succeeded.
assert(_par_scan_state != NULL, "par scan state");
OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
uint queue_num = _par_scan_state->queue_num();
_evacuation_failed = true;
_evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
if (_evac_failure_closure != cl) {
MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
assert(!_drain_in_progress,
"Should only be true while someone holds the lock.");
// Set the global evac-failure closure to the current thread's.
assert(_evac_failure_closure == NULL, "Or locking has failed.");
set_evac_failure_closure(cl);
// Now do the common part.
handle_evacuation_failure_common(old, m);
// Reset to NULL.
set_evac_failure_closure(NULL);
} else {
// The lock is already held, and this is recursive.
assert(_drain_in_progress, "This should only be the recursive case.");
handle_evacuation_failure_common(old, m);
}
return old;
} else {
// Forward-to-self failed. Either someone else managed to allocate
// space for this object (old != forward_ptr) or they beat us in
// self-forwarding it (old == forward_ptr).
assert(old == forward_ptr || !obj_in_cs(forward_ptr),
err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
"should not be in the CSet",
(HeapWord*) old, (HeapWord*) forward_ptr));
return forward_ptr;
}
}
void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
preserve_mark_if_necessary(old, m);
HeapRegion* r = heap_region_containing(old);
if (!r->evacuation_failed()) {
r->set_evacuation_failed(true);
_hr_printer.evac_failure(r);
}
push_on_evac_failure_scan_stack(old);
if (!_drain_in_progress) {
// prevent recursion in copy_to_survivor_space()
_drain_in_progress = true;
drain_evac_failure_scan_stack();
_drain_in_progress = false;
}
}
void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
assert(evacuation_failed(), "Oversaving!");
// We want to call the "for_promotion_failure" version only in the
// case of a promotion failure.
if (m->must_be_preserved_for_promotion_failure(obj)) {
_objs_with_preserved_marks.push(obj);
_preserved_marks_of_objs.push(m);
}
}
HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
size_t word_size) {
if (purpose == GCAllocForSurvived) {
HeapWord* result = survivor_attempt_allocation(word_size);
if (result != NULL) {
return result;
} else {
// Let's try to allocate in the old gen in case we can fit the
// object there.
return old_attempt_allocation(word_size);
}
} else {
assert(purpose == GCAllocForTenured, "sanity");
HeapWord* result = old_attempt_allocation(word_size);
if (result != NULL) {
return result;
} else {
// Let's try to allocate in the survivors in case we can fit the
// object there.
return survivor_attempt_allocation(word_size);
}
}
ShouldNotReachHere();
// Trying to keep some compilers happy.
return NULL;
}
G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
ParGCAllocBuffer(gclab_word_size), _retired(false) { }
G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
: _g1h(g1h),
_refs(g1h->task_queue(queue_num)),
_dcq(&g1h->dirty_card_queue_set()),
_ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
_g1_rem(g1h->g1_rem_set()),
_hash_seed(17), _queue_num(queue_num),
_term_attempts(0),
_surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
_tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
_age_table(false),
_strong_roots_time(0), _term_time(0),
_alloc_buffer_waste(0), _undo_waste(0) {
// we allocate G1YoungSurvRateNumRegions plus one entries, since
// we "sacrifice" entry 0 to keep track of surviving bytes for
// non-young regions (where the age is -1)
// We also add a few elements at the beginning and at the end in
// an attempt to eliminate cache contention
uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
uint array_length = PADDING_ELEM_NUM +
real_length +
PADDING_ELEM_NUM;
_surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
if (_surviving_young_words_base == NULL)
vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
"Not enough space for young surv histo.");
_surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
_alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
_alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
_start = os::elapsedTime();
}
void
G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
{
st->print_raw_cr("GC Termination Stats");
st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
" ------waste (KiB)------");
st->print_raw_cr("thr ms ms % ms % attempts"
" total alloc undo");
st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
" ------- ------- -------");
}
void
G1ParScanThreadState::print_termination_stats(int i,
outputStream* const st) const
{
const double elapsed_ms = elapsed_time() * 1000.0;
const double s_roots_ms = strong_roots_time() * 1000.0;
const double term_ms = term_time() * 1000.0;
st->print_cr("%3d %9.2f %9.2f %6.2f "
"%9.2f %6.2f " SIZE_FORMAT_W(8) " "
SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
(alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
alloc_buffer_waste() * HeapWordSize / K,
undo_waste() * HeapWordSize / K);
}
#ifdef ASSERT
bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
assert(ref != NULL, "invariant");
assert(UseCompressedOops, "sanity");
assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
oop p = oopDesc::load_decode_heap_oop(ref);
assert(_g1h->is_in_g1_reserved(p),
err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
return true;
}
bool G1ParScanThreadState::verify_ref(oop* ref) const {
assert(ref != NULL, "invariant");
if (has_partial_array_mask(ref)) {
// Must be in the collection set--it's already been copied.
oop p = clear_partial_array_mask(ref);
assert(_g1h->obj_in_cs(p),
err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
} else {
oop p = oopDesc::load_decode_heap_oop(ref);
assert(_g1h->is_in_g1_reserved(p),
err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
}
return true;
}
bool G1ParScanThreadState::verify_task(StarTask ref) const {
if (ref.is_narrow()) {
return verify_ref((narrowOop*) ref);
} else {
return verify_ref((oop*) ref);
}
}
#endif // ASSERT
void G1ParScanThreadState::trim_queue() {
assert(_evac_cl != NULL, "not set");
assert(_evac_failure_cl != NULL, "not set");
assert(_partial_scan_cl != NULL, "not set");
StarTask ref;
do {
// Drain the overflow stack first, so other threads can steal.
while (refs()->pop_overflow(ref)) {
deal_with_reference(ref);
}
while (refs()->pop_local(ref)) {
deal_with_reference(ref);
}
} while (!refs()->is_empty());
}
G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
G1ParScanThreadState* par_scan_state) :
_g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
_par_scan_state(par_scan_state),
_worker_id(par_scan_state->queue_num()),
_during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
_mark_in_progress(_g1->mark_in_progress()) { }
template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
#ifdef ASSERT
HeapRegion* hr = _g1->heap_region_containing(obj);
assert(hr != NULL, "sanity");
assert(!hr->in_collection_set(), "should not mark objects in the CSet");
#endif // ASSERT
// We know that the object is not moving so it's safe to read its size.
_cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
}
template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
::mark_forwarded_object(oop from_obj, oop to_obj) {
#ifdef ASSERT
assert(from_obj->is_forwarded(), "from obj should be forwarded");
assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
assert(from_obj != to_obj, "should not be self-forwarded");
HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
assert(from_hr != NULL, "sanity");
assert(from_hr->in_collection_set(), "from obj should be in the CSet");
HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
assert(to_hr != NULL, "sanity");
assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
#endif // ASSERT
// The object might be in the process of being copied by another
// worker so we cannot trust that its to-space image is
// well-formed. So we have to read its size from its from-space
// image which we know should not be changing.
_cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
}
template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
::copy_to_survivor_space(oop old) {
size_t word_sz = old->size();
HeapRegion* from_region = _g1->heap_region_containing_raw(old);
// +1 to make the -1 indexes valid...
int young_index = from_region->young_index_in_cset()+1;
assert( (from_region->is_young() && young_index > 0) ||
(!from_region->is_young() && young_index == 0), "invariant" );
G1CollectorPolicy* g1p = _g1->g1_policy();
markOop m = old->mark();
int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
: m->age();
GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
word_sz);
HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
#ifndef PRODUCT
// Should this evacuation fail?
if (_g1->evacuation_should_fail()) {
if (obj_ptr != NULL) {
_par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
obj_ptr = NULL;
}
}
#endif // !PRODUCT
if (obj_ptr == NULL) {
// This will either forward-to-self, or detect that someone else has
// installed a forwarding pointer.
return _g1->handle_evacuation_failure_par(_par_scan_state, old);
}
oop obj = oop(obj_ptr);
// We're going to allocate linearly, so might as well prefetch ahead.
Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
oop forward_ptr = old->forward_to_atomic(obj);
if (forward_ptr == NULL) {
Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
if (g1p->track_object_age(alloc_purpose)) {
// We could simply do obj->incr_age(). However, this causes a
// performance issue. obj->incr_age() will first check whether
// the object has a displaced mark by checking its mark word;
// getting the mark word from the new location of the object
// stalls. So, given that we already have the mark word and we
// are about to install it anyway, it's better to increase the
// age on the mark word, when the object does not have a
// displaced mark word. We're not expecting many objects to have
// a displaced marked word, so that case is not optimized
// further (it could be...) and we simply call obj->incr_age().
if (m->has_displaced_mark_helper()) {
// in this case, we have to install the mark word first,
// otherwise obj looks to be forwarded (the old mark word,
// which contains the forward pointer, was copied)
obj->set_mark(m);
obj->incr_age();
} else {
m = m->incr_age();
obj->set_mark(m);
}
_par_scan_state->age_table()->add(obj, word_sz);
} else {
obj->set_mark(m);
}
size_t* surv_young_words = _par_scan_state->surviving_young_words();
surv_young_words[young_index] += word_sz;
if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
// We keep track of the next start index in the length field of
// the to-space object. The actual length can be found in the
// length field of the from-space object.
arrayOop(obj)->set_length(0);
oop* old_p = set_partial_array_mask(old);
_par_scan_state->push_on_queue(old_p);
} else {
// No point in using the slower heap_region_containing() method,
// given that we know obj is in the heap.
_scanner.set_region(_g1->heap_region_containing_raw(obj));
obj->oop_iterate_backwards(&_scanner);
}
} else {
_par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
obj = forward_ptr;
}
return obj;
}
template <class T>
void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
_scanned_klass->record_modified_oops();
}
}
template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
template <class T>
void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
::do_oop_work(T* p) {
oop obj = oopDesc::load_decode_heap_oop(p);
assert(barrier != G1BarrierRS || obj != NULL,
"Precondition: G1BarrierRS implies obj is non-NULL");
assert(_worker_id == _par_scan_state->queue_num(), "sanity");
// here the null check is implicit in the cset_fast_test() test
if (_g1->in_cset_fast_test(obj)) {
oop forwardee;
if (obj->is_forwarded()) {
forwardee = obj->forwardee();
} else {
forwardee = copy_to_survivor_space(obj);
}
assert(forwardee != NULL, "forwardee should not be NULL");
oopDesc::encode_store_heap_oop(p, forwardee);
if (do_mark_object && forwardee != obj) {
// If the object is self-forwarded we don't need to explicitly
// mark it, the evacuation failure protocol will do so.
mark_forwarded_object(obj, forwardee);
}
// When scanning the RS, we only care about objs in CS.
if (barrier == G1BarrierRS) {
_par_scan_state->update_rs(_from, p, _worker_id);
} else if (barrier == G1BarrierKlass) {
do_klass_barrier(p, forwardee);
}
} else {
// The object is not in collection set. If we're a root scanning
// closure during an initial mark pause (i.e. do_mark_object will
// be true) then attempt to mark the object.
if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
mark_object(obj);
}
}
if (barrier == G1BarrierEvac && obj != NULL) {
_par_scan_state->update_rs(_from, p, _worker_id);
}
if (do_gen_barrier && obj != NULL) {
par_do_barrier(p);
}
}
template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
assert(has_partial_array_mask(p), "invariant");
oop from_obj = clear_partial_array_mask(p);
assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
assert(from_obj->is_objArray(), "must be obj array");
objArrayOop from_obj_array = objArrayOop(from_obj);
// The from-space object contains the real length.
int length = from_obj_array->length();
assert(from_obj->is_forwarded(), "must be forwarded");
oop to_obj = from_obj->forwardee();
assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
objArrayOop to_obj_array = objArrayOop(to_obj);
// We keep track of the next start index in the length field of the
// to-space object.
int next_index = to_obj_array->length();
assert(0 <= next_index && next_index < length,
err_msg("invariant, next index: %d, length: %d", next_index, length));
int start = next_index;
int end = length;
int remainder = end - start;
// We'll try not to push a range that's smaller than ParGCArrayScanChunk.
if (remainder > 2 * ParGCArrayScanChunk) {
end = start + ParGCArrayScanChunk;
to_obj_array->set_length(end);
// Push the remainder before we process the range in case another
// worker has run out of things to do and can steal it.
oop* from_obj_p = set_partial_array_mask(from_obj);
_par_scan_state->push_on_queue(from_obj_p);
} else {
assert(length == end, "sanity");
// We'll process the final range for this object. Restore the length
// so that the heap remains parsable in case of evacuation failure.
to_obj_array->set_length(end);
}
_scanner.set_region(_g1->heap_region_containing_raw(to_obj));
// Process indexes [start,end). It will also process the header
// along with the first chunk (i.e., the chunk with start == 0).
// Note that at this point the length field of to_obj_array is not
// correct given that we are using it to keep track of the next
// start index. oop_iterate_range() (thankfully!) ignores the length
// field and only relies on the start / end parameters. It does
// however return the size of the object which will be incorrect. So
// we have to ignore it even if we wanted to use it.
to_obj_array->oop_iterate_range(&_scanner, start, end);
}
class G1ParEvacuateFollowersClosure : public VoidClosure {
protected:
G1CollectedHeap* _g1h;
G1ParScanThreadState* _par_scan_state;
RefToScanQueueSet* _queues;
ParallelTaskTerminator* _terminator;
G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
RefToScanQueueSet* queues() { return _queues; }
ParallelTaskTerminator* terminator() { return _terminator; }
public:
G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
G1ParScanThreadState* par_scan_state,
RefToScanQueueSet* queues,
ParallelTaskTerminator* terminator)
: _g1h(g1h), _par_scan_state(par_scan_state),
_queues(queues), _terminator(terminator) {}
void do_void();
private:
inline bool offer_termination();
};
bool G1ParEvacuateFollowersClosure::offer_termination() {
G1ParScanThreadState* const pss = par_scan_state();
pss->start_term_time();
const bool res = terminator()->offer_termination();
pss->end_term_time();
return res;
}
void G1ParEvacuateFollowersClosure::do_void() {
StarTask stolen_task;
G1ParScanThreadState* const pss = par_scan_state();
pss->trim_queue();
do {
while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
assert(pss->verify_task(stolen_task), "sanity");
if (stolen_task.is_narrow()) {
pss->deal_with_reference((narrowOop*) stolen_task);
} else {
pss->deal_with_reference((oop*) stolen_task);
}
// We've just processed a reference and we might have made
// available new entries on the queues. So we have to make sure
// we drain the queues as necessary.
pss->trim_queue();
}
} while (!offer_termination());
pss->retire_alloc_buffers();
}
class G1KlassScanClosure : public KlassClosure {
G1ParCopyHelper* _closure;
bool _process_only_dirty;
int _count;
public:
G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
: _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
void do_klass(Klass* klass) {
// If the klass has not been dirtied we know that there's
// no references into the young gen and we can skip it.
if (!_process_only_dirty || klass->has_modified_oops()) {
// Clean the klass since we're going to scavenge all the metadata.
klass->clear_modified_oops();
// Tell the closure that this klass is the Klass to scavenge
// and is the one to dirty if oops are left pointing into the young gen.
_closure->set_scanned_klass(klass);
klass->oops_do(_closure);
_closure->set_scanned_klass(NULL);
}
_count++;
}
};
class G1ParTask : public AbstractGangTask {
protected:
G1CollectedHeap* _g1h;
RefToScanQueueSet *_queues;
ParallelTaskTerminator _terminator;
uint _n_workers;
Mutex _stats_lock;
Mutex* stats_lock() { return &_stats_lock; }
size_t getNCards() {
return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
/ G1BlockOffsetSharedArray::N_bytes;
}
public:
G1ParTask(G1CollectedHeap* g1h,
RefToScanQueueSet *task_queues)
: AbstractGangTask("G1 collection"),
_g1h(g1h),
_queues(task_queues),
_terminator(0, _queues),
_stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
{}
RefToScanQueueSet* queues() { return _queues; }
RefToScanQueue *work_queue(int i) {
return queues()->queue(i);
}
ParallelTaskTerminator* terminator() { return &_terminator; }
virtual void set_for_termination(int active_workers) {
// This task calls set_n_termination() in par_non_clean_card_iterate_work()
// in the young space (_par_seq_tasks) in the G1 heap
// for SequentialSubTasksDone.
// This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
// both of which need setting by set_n_termination().
_g1h->SharedHeap::set_n_termination(active_workers);
_g1h->set_n_termination(active_workers);
terminator()->reset_for_reuse(active_workers);
_n_workers = active_workers;
}
void work(uint worker_id) {
if (worker_id >= _n_workers) return; // no work needed this round
double start_time_ms = os::elapsedTime() * 1000.0;
_g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
{
ResourceMark rm;
HandleMark hm;
ReferenceProcessor* rp = _g1h->ref_processor_stw();
G1ParScanThreadState pss(_g1h, worker_id);
G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
pss.set_evac_closure(&scan_evac_cl);
pss.set_evac_failure_closure(&evac_failure_cl);
pss.set_partial_scan_closure(&partial_scan_cl);
G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
bool only_young = _g1h->g1_policy()->gcs_are_young();
G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
OopClosure* scan_root_cl = &only_scan_root_cl;
G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
if (_g1h->g1_policy()->during_initial_mark_pause()) {
// We also need to mark copied objects.
scan_root_cl = &scan_mark_root_cl;
scan_klasses_cl = &scan_mark_klasses_cl_s;
}
G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
// Don't scan the scavengable methods in the code cache as part
// of strong root scanning. The code roots that point into a
// region in the collection set are scanned when we scan the
// region's RSet.
int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
pss.start_strong_roots();
_g1h->g1_process_strong_roots(/* is scavenging */ true,
SharedHeap::ScanningOption(so),
scan_root_cl,
&push_heap_rs_cl,
scan_klasses_cl,
worker_id);
pss.end_strong_roots();
{
double start = os::elapsedTime();
G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
evac.do_void();
double elapsed_ms = (os::elapsedTime()-start)*1000.0;
double term_ms = pss.term_time()*1000.0;
_g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
_g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
}
_g1h->g1_policy()->record_thread_age_table(pss.age_table());
_g1h->update_surviving_young_words(pss.surviving_young_words()+1);
if (ParallelGCVerbose) {
MutexLocker x(stats_lock());
pss.print_termination_stats(worker_id);
}
assert(pss.refs()->is_empty(), "should be empty");
// Close the inner scope so that the ResourceMark and HandleMark
// destructors are executed here and are included as part of the
// "GC Worker Time".
}
double end_time_ms = os::elapsedTime() * 1000.0;
_g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
}
};
// *** Common G1 Evacuation Stuff
// This method is run in a GC worker.
void
G1CollectedHeap::
g1_process_strong_roots(bool is_scavenging,
ScanningOption so,
OopClosure* scan_non_heap_roots,
OopsInHeapRegionClosure* scan_rs,
G1KlassScanClosure* scan_klasses,
int worker_i) {
// First scan the strong roots
double ext_roots_start = os::elapsedTime();
double closure_app_time_sec = 0.0;
BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow");
// Walk the code cache/strong code roots w/o buffering, because StarTask
// cannot handle unaligned oop locations.
CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
process_strong_roots(false, // no scoping; this is parallel code
is_scavenging, so,
&buf_scan_non_heap_roots,
&eager_scan_code_roots,
scan_klasses
);
// Now the CM ref_processor roots.
if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
// We need to treat the discovered reference lists of the
// concurrent mark ref processor as roots and keep entries
// (which are added by the marking threads) on them live
// until they can be processed at the end of marking.
ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
}
// Finish up any enqueued closure apps (attributed as object copy time).
buf_scan_non_heap_roots.done();
double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
double ext_root_time_ms =
((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
// During conc marking we have to filter the per-thread SATB buffers
// to make sure we remove any oops into the CSet (which will show up
// as implicitly live).
double satb_filtering_ms = 0.0;
if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
if (mark_in_progress()) {
double satb_filter_start = os::elapsedTime();
JavaThread::satb_mark_queue_set().filter_thread_buffers();
satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
}
}
g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
// If this is an initial mark pause, and we're not scanning
// the entire code cache, we need to mark the oops in the
// strong code root lists for the regions that are not in
// the collection set.
// Note all threads participate in this set of root tasks.
double mark_strong_code_roots_ms = 0.0;
if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) {
double mark_strong_roots_start = os::elapsedTime();
mark_strong_code_roots(worker_i);
mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
}
g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
// Now scan the complement of the collection set.
if (scan_rs != NULL) {
g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
}
_process_strong_tasks->all_tasks_completed();
}
void
G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) {
CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
SharedHeap::process_weak_roots(root_closure, &roots_in_blobs);
}
// Weak Reference Processing support
// An always "is_alive" closure that is used to preserve referents.
// If the object is non-null then it's alive. Used in the preservation
// of referent objects that are pointed to by reference objects
// discovered by the CM ref processor.
class G1AlwaysAliveClosure: public BoolObjectClosure {
G1CollectedHeap* _g1;
public:
G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
bool do_object_b(oop p) {
if (p != NULL) {
return true;
}
return false;
}
};
bool G1STWIsAliveClosure::do_object_b(oop p) {
// An object is reachable if it is outside the collection set,
// or is inside and copied.
return !_g1->obj_in_cs(p) || p->is_forwarded();
}
// Non Copying Keep Alive closure
class G1KeepAliveClosure: public OopClosure {
G1CollectedHeap* _g1;
public:
G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
void do_oop( oop* p) {
oop obj = *p;
if (_g1->obj_in_cs(obj)) {
assert( obj->is_forwarded(), "invariant" );
*p = obj->forwardee();
}
}
};
// Copying Keep Alive closure - can be called from both
// serial and parallel code as long as different worker
// threads utilize different G1ParScanThreadState instances
// and different queues.
class G1CopyingKeepAliveClosure: public OopClosure {
G1CollectedHeap* _g1h;
OopClosure* _copy_non_heap_obj_cl;
OopsInHeapRegionClosure* _copy_metadata_obj_cl;
G1ParScanThreadState* _par_scan_state;
public:
G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
OopClosure* non_heap_obj_cl,
OopsInHeapRegionClosure* metadata_obj_cl,
G1ParScanThreadState* pss):
_g1h(g1h),
_copy_non_heap_obj_cl(non_heap_obj_cl),
_copy_metadata_obj_cl(metadata_obj_cl),
_par_scan_state(pss)
{}
virtual void do_oop(narrowOop* p) { do_oop_work(p); }
virtual void do_oop( oop* p) { do_oop_work(p); }
template <class T> void do_oop_work(T* p) {
oop obj = oopDesc::load_decode_heap_oop(p);
if (_g1h->obj_in_cs(obj)) {
// If the referent object has been forwarded (either copied
// to a new location or to itself in the event of an
// evacuation failure) then we need to update the reference
// field and, if both reference and referent are in the G1
// heap, update the RSet for the referent.
//
// If the referent has not been forwarded then we have to keep
// it alive by policy. Therefore we have copy the referent.
//
// If the reference field is in the G1 heap then we can push
// on the PSS queue. When the queue is drained (after each
// phase of reference processing) the object and it's followers
// will be copied, the reference field set to point to the
// new location, and the RSet updated. Otherwise we need to
// use the the non-heap or metadata closures directly to copy
// the referent object and update the pointer, while avoiding
// updating the RSet.
if (_g1h->is_in_g1_reserved(p)) {
_par_scan_state->push_on_queue(p);
} else {
assert(!ClassLoaderDataGraph::contains((address)p),
err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
PTR_FORMAT, p));
_copy_non_heap_obj_cl->do_oop(p);
}
}
}
};
// Serial drain queue closure. Called as the 'complete_gc'
// closure for each discovered list in some of the
// reference processing phases.
class G1STWDrainQueueClosure: public VoidClosure {
protected:
G1CollectedHeap* _g1h;
G1ParScanThreadState* _par_scan_state;
G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
public:
G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
_g1h(g1h),
_par_scan_state(pss)
{ }
void do_void() {
G1ParScanThreadState* const pss = par_scan_state();
pss->trim_queue();
}
};
// Parallel Reference Processing closures
// Implementation of AbstractRefProcTaskExecutor for parallel reference
// processing during G1 evacuation pauses.
class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
private:
G1CollectedHeap* _g1h;
RefToScanQueueSet* _queues;
FlexibleWorkGang* _workers;
int _active_workers;
public:
G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
FlexibleWorkGang* workers,
RefToScanQueueSet *task_queues,
int n_workers) :
_g1h(g1h),
_queues(task_queues),
_workers(workers),
_active_workers(n_workers)
{
assert(n_workers > 0, "shouldn't call this otherwise");
}
// Executes the given task using concurrent marking worker threads.
virtual void execute(ProcessTask& task);
virtual void execute(EnqueueTask& task);
};
// Gang task for possibly parallel reference processing
class G1STWRefProcTaskProxy: public AbstractGangTask {
typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
ProcessTask& _proc_task;
G1CollectedHeap* _g1h;
RefToScanQueueSet *_task_queues;
ParallelTaskTerminator* _terminator;
public:
G1STWRefProcTaskProxy(ProcessTask& proc_task,
G1CollectedHeap* g1h,
RefToScanQueueSet *task_queues,
ParallelTaskTerminator* terminator) :
AbstractGangTask("Process reference objects in parallel"),
_proc_task(proc_task),
_g1h(g1h),
_task_queues(task_queues),
_terminator(terminator)
{}
virtual void work(uint worker_id) {
// The reference processing task executed by a single worker.
ResourceMark rm;
HandleMark hm;
G1STWIsAliveClosure is_alive(_g1h);
G1ParScanThreadState pss(_g1h, worker_id);
G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
pss.set_evac_closure(&scan_evac_cl);
pss.set_evac_failure_closure(&evac_failure_cl);
pss.set_partial_scan_closure(&partial_scan_cl);
G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
if (_g1h->g1_policy()->during_initial_mark_pause()) {
// We also need to mark copied objects.
copy_non_heap_cl = ©_mark_non_heap_cl;
copy_metadata_cl = ©_mark_metadata_cl;
}
// Keep alive closure.
G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
// Complete GC closure
G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
// Call the reference processing task's work routine.
_proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
// Note we cannot assert that the refs array is empty here as not all
// of the processing tasks (specifically phase2 - pp2_work) execute
// the complete_gc closure (which ordinarily would drain the queue) so
// the queue may not be empty.
}
};
// Driver routine for parallel reference processing.
// Creates an instance of the ref processing gang
// task and has the worker threads execute it.
void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
assert(_workers != NULL, "Need parallel worker threads.");
ParallelTaskTerminator terminator(_active_workers, _queues);
G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
_g1h->set_par_threads(_active_workers);
_workers->run_task(&proc_task_proxy);
_g1h->set_par_threads(0);
}
// Gang task for parallel reference enqueueing.
class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
EnqueueTask& _enq_task;
public:
G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
AbstractGangTask("Enqueue reference objects in parallel"),
_enq_task(enq_task)
{ }
virtual void work(uint worker_id) {
_enq_task.work(worker_id);
}
};
// Driver routine for parallel reference enqueueing.
// Creates an instance of the ref enqueueing gang
// task and has the worker threads execute it.
void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
assert(_workers != NULL, "Need parallel worker threads.");
G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
_g1h->set_par_threads(_active_workers);
_workers->run_task(&enq_task_proxy);
_g1h->set_par_threads(0);
}
// End of weak reference support closures
// Abstract task used to preserve (i.e. copy) any referent objects
// that are in the collection set and are pointed to by reference
// objects discovered by the CM ref processor.
class G1ParPreserveCMReferentsTask: public AbstractGangTask {
protected:
G1CollectedHeap* _g1h;
RefToScanQueueSet *_queues;
ParallelTaskTerminator _terminator;
uint _n_workers;
public:
G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
AbstractGangTask("ParPreserveCMReferents"),
_g1h(g1h),
_queues(task_queues),
_terminator(workers, _queues),
_n_workers(workers)
{ }
void work(uint worker_id) {
ResourceMark rm;
HandleMark hm;
G1ParScanThreadState pss(_g1h, worker_id);
G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
pss.set_evac_closure(&scan_evac_cl);
pss.set_evac_failure_closure(&evac_failure_cl);
pss.set_partial_scan_closure(&partial_scan_cl);
assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
if (_g1h->g1_policy()->during_initial_mark_pause()) {
// We also need to mark copied objects.
copy_non_heap_cl = ©_mark_non_heap_cl;
copy_metadata_cl = ©_mark_metadata_cl;
}
// Is alive closure
G1AlwaysAliveClosure always_alive(_g1h);
// Copying keep alive closure. Applied to referent objects that need
// to be copied.
G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
ReferenceProcessor* rp = _g1h->ref_processor_cm();
uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
uint stride = MIN2(MAX2(_n_workers, 1U), limit);
// limit is set using max_num_q() - which was set using ParallelGCThreads.
// So this must be true - but assert just in case someone decides to
// change the worker ids.
assert(0 <= worker_id && worker_id < limit, "sanity");
assert(!rp->discovery_is_atomic(), "check this code");
// Select discovered lists [i, i+stride, i+2*stride,...,limit)
for (uint idx = worker_id; idx < limit; idx += stride) {
DiscoveredList& ref_list = rp->discovered_refs()[idx];
DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
while (iter.has_next()) {
// Since discovery is not atomic for the CM ref processor, we
// can see some null referent objects.
iter.load_ptrs(DEBUG_ONLY(true));
oop ref = iter.obj();
// This will filter nulls.
if (iter.is_referent_alive()) {
iter.make_referent_alive();
}
iter.move_to_next();
}
}
// Drain the queue - which may cause stealing
G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
drain_queue.do_void();
// Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
assert(pss.refs()->is_empty(), "should be");
}
};
// Weak Reference processing during an evacuation pause (part 1).
void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
double ref_proc_start = os::elapsedTime();
ReferenceProcessor* rp = _ref_processor_stw;
assert(rp->discovery_enabled(), "should have been enabled");
// Any reference objects, in the collection set, that were 'discovered'
// by the CM ref processor should have already been copied (either by
// applying the external root copy closure to the discovered lists, or
// by following an RSet entry).
//
// But some of the referents, that are in the collection set, that these
// reference objects point to may not have been copied: the STW ref
// processor would have seen that the reference object had already
// been 'discovered' and would have skipped discovering the reference,
// but would not have treated the reference object as a regular oop.
// As a result the copy closure would not have been applied to the
// referent object.
//
// We need to explicitly copy these referent objects - the references
// will be processed at the end of remarking.
//
// We also need to do this copying before we process the reference
// objects discovered by the STW ref processor in case one of these
// referents points to another object which is also referenced by an
// object discovered by the STW ref processor.
assert(!G1CollectedHeap::use_parallel_gc_threads() ||
no_of_gc_workers == workers()->active_workers(),
"Need to reset active GC workers");
set_par_threads(no_of_gc_workers);
G1ParPreserveCMReferentsTask keep_cm_referents(this,
no_of_gc_workers,
_task_queues);
if (G1CollectedHeap::use_parallel_gc_threads()) {
workers()->run_task(&keep_cm_referents);
} else {
keep_cm_referents.work(0);
}
set_par_threads(0);
// Closure to test whether a referent is alive.
G1STWIsAliveClosure is_alive(this);
// Even when parallel reference processing is enabled, the processing
// of JNI refs is serial and performed serially by the current thread
// rather than by a worker. The following PSS will be used for processing
// JNI refs.
// Use only a single queue for this PSS.
G1ParScanThreadState pss(this, 0);
// We do not embed a reference processor in the copying/scanning
// closures while we're actually processing the discovered
// reference objects.
G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
pss.set_evac_closure(&scan_evac_cl);
pss.set_evac_failure_closure(&evac_failure_cl);
pss.set_partial_scan_closure(&partial_scan_cl);
assert(pss.refs()->is_empty(), "pre-condition");
G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
if (_g1h->g1_policy()->during_initial_mark_pause()) {
// We also need to mark copied objects.
copy_non_heap_cl = ©_mark_non_heap_cl;
copy_metadata_cl = ©_mark_metadata_cl;
}
// Keep alive closure.
G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
// Serial Complete GC closure
G1STWDrainQueueClosure drain_queue(this, &pss);
// Setup the soft refs policy...
rp->setup_policy(false);
ReferenceProcessorStats stats;
if (!rp->processing_is_mt()) {
// Serial reference processing...
stats = rp->process_discovered_references(&is_alive,
&keep_alive,
&drain_queue,
NULL,
_gc_timer_stw);
} else {
// Parallel reference processing
assert(rp->num_q() == no_of_gc_workers, "sanity");
assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
stats = rp->process_discovered_references(&is_alive,
&keep_alive,
&drain_queue,
&par_task_executor,
_gc_timer_stw);
}
_gc_tracer_stw->report_gc_reference_stats(stats);
// We have completed copying any necessary live referent objects
// (that were not copied during the actual pause) so we can
// retire any active alloc buffers
pss.retire_alloc_buffers();
assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
double ref_proc_time = os::elapsedTime() - ref_proc_start;
g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
}
// Weak Reference processing during an evacuation pause (part 2).
void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
double ref_enq_start = os::elapsedTime();
ReferenceProcessor* rp = _ref_processor_stw;
assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
// Now enqueue any remaining on the discovered lists on to
// the pending list.
if (!rp->processing_is_mt()) {
// Serial reference processing...
rp->enqueue_discovered_references();
} else {
// Parallel reference enqueueing
assert(no_of_gc_workers == workers()->active_workers(),
"Need to reset active workers");
assert(rp->num_q() == no_of_gc_workers, "sanity");
assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
rp->enqueue_discovered_references(&par_task_executor);
}
rp->verify_no_references_recorded();
assert(!rp->discovery_enabled(), "should have been disabled");
// FIXME
// CM's reference processing also cleans up the string and symbol tables.
// Should we do that here also? We could, but it is a serial operation
// and could significantly increase the pause time.
double ref_enq_time = os::elapsedTime() - ref_enq_start;
g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
}
void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
_expand_heap_after_alloc_failure = true;
_evacuation_failed = false;
// Should G1EvacuationFailureALot be in effect for this GC?
NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
g1_rem_set()->prepare_for_oops_into_collection_set_do();
// Disable the hot card cache.
G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
hot_card_cache->reset_hot_cache_claimed_index();
hot_card_cache->set_use_cache(false);
uint n_workers;
if (G1CollectedHeap::use_parallel_gc_threads()) {
n_workers =
AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
workers()->active_workers(),
Threads::number_of_non_daemon_threads());
assert(UseDynamicNumberOfGCThreads ||
n_workers == workers()->total_workers(),
"If not dynamic should be using all the workers");
workers()->set_active_workers(n_workers);
set_par_threads(n_workers);
} else {
assert(n_par_threads() == 0,
"Should be the original non-parallel value");
n_workers = 1;
}
G1ParTask g1_par_task(this, _task_queues);
init_for_evac_failure(NULL);
rem_set()->prepare_for_younger_refs_iterate(true);
assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
double start_par_time_sec = os::elapsedTime();
double end_par_time_sec;
{
StrongRootsScope srs(this);
if (G1CollectedHeap::use_parallel_gc_threads()) {
// The individual threads will set their evac-failure closures.
if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
// These tasks use ShareHeap::_process_strong_tasks
assert(UseDynamicNumberOfGCThreads ||
workers()->active_workers() == workers()->total_workers(),
"If not dynamic should be using all the workers");
workers()->run_task(&g1_par_task);
} else {
g1_par_task.set_for_termination(n_workers);
g1_par_task.work(0);
}
end_par_time_sec = os::elapsedTime();
// Closing the inner scope will execute the destructor
// for the StrongRootsScope object. We record the current
// elapsed time before closing the scope so that time
// taken for the SRS destructor is NOT included in the
// reported parallel time.
}
double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
g1_policy()->phase_times()->record_par_time(par_time_ms);
double code_root_fixup_time_ms =
(os::elapsedTime() - end_par_time_sec) * 1000.0;
g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
set_par_threads(0);
// Process any discovered reference objects - we have
// to do this _before_ we retire the GC alloc regions
// as we may have to copy some 'reachable' referent
// objects (and their reachable sub-graphs) that were
// not copied during the pause.
process_discovered_references(n_workers);
// Weak root processing.
{
G1STWIsAliveClosure is_alive(this);
G1KeepAliveClosure keep_alive(this);
JNIHandles::weak_oops_do(&is_alive, &keep_alive);
}
release_gc_alloc_regions(n_workers, evacuation_info);
g1_rem_set()->cleanup_after_oops_into_collection_set_do();
// Reset and re-enable the hot card cache.
// Note the counts for the cards in the regions in the
// collection set are reset when the collection set is freed.
hot_card_cache->reset_hot_cache();
hot_card_cache->set_use_cache(true);
// Migrate the strong code roots attached to each region in
// the collection set. Ideally we would like to do this
// after we have finished the scanning/evacuation of the
// strong code roots for a particular heap region.
migrate_strong_code_roots();
if (g1_policy()->during_initial_mark_pause()) {
// Reset the claim values set during marking the strong code roots
reset_heap_region_claim_values();
}
finalize_for_evac_failure();
if (evacuation_failed()) {
remove_self_forwarding_pointers();
// Reset the G1EvacuationFailureALot counters and flags
// Note: the values are reset only when an actual
// evacuation failure occurs.
NOT_PRODUCT(reset_evacuation_should_fail();)
}
// Enqueue any remaining references remaining on the STW
// reference processor's discovered lists. We need to do
// this after the card table is cleaned (and verified) as
// the act of enqueueing entries on to the pending list
// will log these updates (and dirty their associated
// cards). We need these updates logged to update any
// RSets.
enqueue_discovered_references(n_workers);
if (G1DeferredRSUpdate) {
RedirtyLoggedCardTableEntryFastClosure redirty;
dirty_card_queue_set().set_closure(&redirty);
dirty_card_queue_set().apply_closure_to_all_completed_buffers();
DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
dcq.merge_bufferlists(&dirty_card_queue_set());
assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
}
COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
}
void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
size_t* pre_used,
FreeRegionList* free_list,
OldRegionSet* old_proxy_set,
HumongousRegionSet* humongous_proxy_set,
HRRSCleanupTask* hrrs_cleanup_task,
bool par) {
if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
if (hr->isHumongous()) {
assert(hr->startsHumongous(), "we should only see starts humongous");
free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
} else {
_old_set.remove_with_proxy(hr, old_proxy_set);
free_region(hr, pre_used, free_list, par);
}
} else {
hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
}
}
void G1CollectedHeap::free_region(HeapRegion* hr,
size_t* pre_used,
FreeRegionList* free_list,
bool par) {
assert(!hr->isHumongous(), "this is only for non-humongous regions");
assert(!hr->is_empty(), "the region should not be empty");
assert(free_list != NULL, "pre-condition");
// Clear the card counts for this region.
// Note: we only need to do this if the region is not young
// (since we don't refine cards in young regions).
if (!hr->is_young()) {
_cg1r->hot_card_cache()->reset_card_counts(hr);
}
*pre_used += hr->used();
hr->hr_clear(par, true /* clear_space */);
free_list->add_as_head(hr);
}
void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
size_t* pre_used,
FreeRegionList* free_list,
HumongousRegionSet* humongous_proxy_set,
bool par) {
assert(hr->startsHumongous(), "this is only for starts humongous regions");
assert(free_list != NULL, "pre-condition");
assert(humongous_proxy_set != NULL, "pre-condition");
size_t hr_used = hr->used();
size_t hr_capacity = hr->capacity();
size_t hr_pre_used = 0;
_humongous_set.remove_with_proxy(hr, humongous_proxy_set);
// We need to read this before we make the region non-humongous,
// otherwise the information will be gone.
uint last_index = hr->last_hc_index();
hr->set_notHumongous();
free_region(hr, &hr_pre_used, free_list, par);
uint i = hr->hrs_index() + 1;
while (i < last_index) {
HeapRegion* curr_hr = region_at(i);
assert(curr_hr->continuesHumongous(), "invariant");
curr_hr->set_notHumongous();
free_region(curr_hr, &hr_pre_used, free_list, par);
i += 1;
}
assert(hr_pre_used == hr_used,
err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
"should be the same", hr_pre_used, hr_used));
*pre_used += hr_pre_used;
}
void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
FreeRegionList* free_list,
OldRegionSet* old_proxy_set,
HumongousRegionSet* humongous_proxy_set,
bool par) {
if (pre_used > 0) {
Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
assert(_summary_bytes_used >= pre_used,
err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
"should be >= pre_used: "SIZE_FORMAT,
_summary_bytes_used, pre_used));
_summary_bytes_used -= pre_used;
}
if (free_list != NULL && !free_list->is_empty()) {
MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
_free_list.add_as_head(free_list);
}
if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
_old_set.update_from_proxy(old_proxy_set);
}
if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
_humongous_set.update_from_proxy(humongous_proxy_set);
}
}
class G1ParCleanupCTTask : public AbstractGangTask {
CardTableModRefBS* _ct_bs;
G1CollectedHeap* _g1h;
HeapRegion* volatile _su_head;
public:
G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
G1CollectedHeap* g1h) :
AbstractGangTask("G1 Par Cleanup CT Task"),
_ct_bs(ct_bs), _g1h(g1h) { }
void work(uint worker_id) {
HeapRegion* r;
while (r = _g1h->pop_dirty_cards_region()) {
clear_cards(r);
}
}
void clear_cards(HeapRegion* r) {
// Cards of the survivors should have already been dirtied.
if (!r->is_survivor()) {
_ct_bs->clear(MemRegion(r->bottom(), r->end()));
}
}
};
#ifndef PRODUCT
class G1VerifyCardTableCleanup: public HeapRegionClosure {
G1CollectedHeap* _g1h;
CardTableModRefBS* _ct_bs;
public:
G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
: _g1h(g1h), _ct_bs(ct_bs) { }
virtual bool doHeapRegion(HeapRegion* r) {
if (r->is_survivor()) {
_g1h->verify_dirty_region(r);
} else {
_g1h->verify_not_dirty_region(r);
}
return false;
}
};
void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
// All of the region should be clean.
CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
MemRegion mr(hr->bottom(), hr->end());
ct_bs->verify_not_dirty_region(mr);
}
void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
// We cannot guarantee that [bottom(),end()] is dirty. Threads
// dirty allocated blocks as they allocate them. The thread that
// retires each region and replaces it with a new one will do a
// maximal allocation to fill in [pre_dummy_top(),end()] but will
// not dirty that area (one less thing to have to do while holding
// a lock). So we can only verify that [bottom(),pre_dummy_top()]
// is dirty.
CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
MemRegion mr(hr->bottom(), hr->pre_dummy_top());
ct_bs->verify_dirty_region(mr);
}
void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
verify_dirty_region(hr);
}
}
void G1CollectedHeap::verify_dirty_young_regions() {
verify_dirty_young_list(_young_list->first_region());
}
#endif
void G1CollectedHeap::cleanUpCardTable() {
CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
double start = os::elapsedTime();
{
// Iterate over the dirty cards region list.
G1ParCleanupCTTask cleanup_task(ct_bs, this);
if (G1CollectedHeap::use_parallel_gc_threads()) {
set_par_threads();
workers()->run_task(&cleanup_task);
set_par_threads(0);
} else {
while (_dirty_cards_region_list) {
HeapRegion* r = _dirty_cards_region_list;
cleanup_task.clear_cards(r);
_dirty_cards_region_list = r->get_next_dirty_cards_region();
if (_dirty_cards_region_list == r) {
// The last region.
_dirty_cards_region_list = NULL;
}
r->set_next_dirty_cards_region(NULL);
}
}
#ifndef PRODUCT
if (G1VerifyCTCleanup || VerifyAfterGC) {
G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
heap_region_iterate(&cleanup_verifier);
}
#endif
}
double elapsed = os::elapsedTime() - start;
g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
}
void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
size_t pre_used = 0;
FreeRegionList local_free_list("Local List for CSet Freeing");
double young_time_ms = 0.0;
double non_young_time_ms = 0.0;
// Since the collection set is a superset of the the young list,
// all we need to do to clear the young list is clear its
// head and length, and unlink any young regions in the code below
_young_list->clear();
G1CollectorPolicy* policy = g1_policy();
double start_sec = os::elapsedTime();
bool non_young = true;
HeapRegion* cur = cs_head;
int age_bound = -1;
size_t rs_lengths = 0;
while (cur != NULL) {
assert(!is_on_master_free_list(cur), "sanity");
if (non_young) {
if (cur->is_young()) {
double end_sec = os::elapsedTime();
double elapsed_ms = (end_sec - start_sec) * 1000.0;
non_young_time_ms += elapsed_ms;
start_sec = os::elapsedTime();
non_young = false;
}
} else {
if (!cur->is_young()) {
double end_sec = os::elapsedTime();
double elapsed_ms = (end_sec - start_sec) * 1000.0;
young_time_ms += elapsed_ms;
start_sec = os::elapsedTime();
non_young = true;
}
}
rs_lengths += cur->rem_set()->occupied();
HeapRegion* next = cur->next_in_collection_set();
assert(cur->in_collection_set(), "bad CS");
cur->set_next_in_collection_set(NULL);
cur->set_in_collection_set(false);
if (cur->is_young()) {
int index = cur->young_index_in_cset();
assert(index != -1, "invariant");
assert((uint) index < policy->young_cset_region_length(), "invariant");
size_t words_survived = _surviving_young_words[index];
cur->record_surv_words_in_group(words_survived);
// At this point the we have 'popped' cur from the collection set
// (linked via next_in_collection_set()) but it is still in the
// young list (linked via next_young_region()). Clear the
// _next_young_region field.
cur->set_next_young_region(NULL);
} else {
int index = cur->young_index_in_cset();
assert(index == -1, "invariant");
}
assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
(!cur->is_young() && cur->young_index_in_cset() == -1),
"invariant" );
if (!cur->evacuation_failed()) {
MemRegion used_mr = cur->used_region();
// And the region is empty.
assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
free_region(cur, &pre_used, &local_free_list, false /* par */);
} else {
cur->uninstall_surv_rate_group();
if (cur->is_young()) {
cur->set_young_index_in_cset(-1);
}
cur->set_not_young();
cur->set_evacuation_failed(false);
// The region is now considered to be old.
_old_set.add(cur);
evacuation_info.increment_collectionset_used_after(cur->used());
}
cur = next;
}
evacuation_info.set_regions_freed(local_free_list.length());
policy->record_max_rs_lengths(rs_lengths);
policy->cset_regions_freed();
double end_sec = os::elapsedTime();
double elapsed_ms = (end_sec - start_sec) * 1000.0;
if (non_young) {
non_young_time_ms += elapsed_ms;
} else {
young_time_ms += elapsed_ms;
}
update_sets_after_freeing_regions(pre_used, &local_free_list,
NULL /* old_proxy_set */,
NULL /* humongous_proxy_set */,
false /* par */);
policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
}
// This routine is similar to the above but does not record
// any policy statistics or update free lists; we are abandoning
// the current incremental collection set in preparation of a
// full collection. After the full GC we will start to build up
// the incremental collection set again.
// This is only called when we're doing a full collection
// and is immediately followed by the tearing down of the young list.
void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
HeapRegion* cur = cs_head;
while (cur != NULL) {
HeapRegion* next = cur->next_in_collection_set();
assert(cur->in_collection_set(), "bad CS");
cur->set_next_in_collection_set(NULL);
cur->set_in_collection_set(false);
cur->set_young_index_in_cset(-1);
cur = next;
}
}
void G1CollectedHeap::set_free_regions_coming() {
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
"setting free regions coming");
}
assert(!free_regions_coming(), "pre-condition");
_free_regions_coming = true;
}
void G1CollectedHeap::reset_free_regions_coming() {
assert(free_regions_coming(), "pre-condition");
{
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
_free_regions_coming = false;
SecondaryFreeList_lock->notify_all();
}
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
"reset free regions coming");
}
}
void G1CollectedHeap::wait_while_free_regions_coming() {
// Most of the time we won't have to wait, so let's do a quick test
// first before we take the lock.
if (!free_regions_coming()) {
return;
}
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
"waiting for free regions");
}
{
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
while (free_regions_coming()) {
SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
}
}
if (G1ConcRegionFreeingVerbose) {
gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
"done waiting for free regions");
}
}
void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
assert(heap_lock_held_for_gc(),
"the heap lock should already be held by or for this thread");
_young_list->push_region(hr);
}
class NoYoungRegionsClosure: public HeapRegionClosure {
private:
bool _success;
public:
NoYoungRegionsClosure() : _success(true) { }
bool doHeapRegion(HeapRegion* r) {
if (r->is_young()) {
gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
r->bottom(), r->end());
_success = false;
}
return false;
}
bool success() { return _success; }
};
bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
bool ret = _young_list->check_list_empty(check_sample);
if (check_heap) {
NoYoungRegionsClosure closure;
heap_region_iterate(&closure);
ret = ret && closure.success();
}
return ret;
}
class TearDownRegionSetsClosure : public HeapRegionClosure {
private:
OldRegionSet *_old_set;
public:
TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
bool doHeapRegion(HeapRegion* r) {
if (r->is_empty()) {
// We ignore empty regions, we'll empty the free list afterwards
} else if (r->is_young()) {
// We ignore young regions, we'll empty the young list afterwards
} else if (r->isHumongous()) {
// We ignore humongous regions, we're not tearing down the
// humongous region set
} else {
// The rest should be old
_old_set->remove(r);
}
return false;
}
~TearDownRegionSetsClosure() {
assert(_old_set->is_empty(), "post-condition");
}
};
void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
assert_at_safepoint(true /* should_be_vm_thread */);
if (!free_list_only) {
TearDownRegionSetsClosure cl(&_old_set);
heap_region_iterate(&cl);
// Need to do this after the heap iteration to be able to
// recognize the young regions and ignore them during the iteration.
_young_list->empty_list();
}
_free_list.remove_all();
}
class RebuildRegionSetsClosure : public HeapRegionClosure {
private:
bool _free_list_only;
OldRegionSet* _old_set;
FreeRegionList* _free_list;
size_t _total_used;
public:
RebuildRegionSetsClosure(bool free_list_only,
OldRegionSet* old_set, FreeRegionList* free_list) :
_free_list_only(free_list_only),
_old_set(old_set), _free_list(free_list), _total_used(0) {
assert(_free_list->is_empty(), "pre-condition");
if (!free_list_only) {
assert(_old_set->is_empty(), "pre-condition");
}
}
bool doHeapRegion(HeapRegion* r) {
if (r->continuesHumongous()) {
return false;
}
if (r->is_empty()) {
// Add free regions to the free list
_free_list->add_as_tail(r);
} else if (!_free_list_only) {
assert(!r->is_young(), "we should not come across young regions");
if (r->isHumongous()) {
// We ignore humongous regions, we left the humongous set unchanged
} else {
// The rest should be old, add them to the old set
_old_set->add(r);
}
_total_used += r->used();
}
return false;
}
size_t total_used() {
return _total_used;
}
};
void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
assert_at_safepoint(true /* should_be_vm_thread */);
RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
heap_region_iterate(&cl);
if (!free_list_only) {
_summary_bytes_used = cl.total_used();
}
assert(_summary_bytes_used == recalculate_used(),
err_msg("inconsistent _summary_bytes_used, "
"value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
_summary_bytes_used, recalculate_used()));
}
void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
_refine_cte_cl->set_concurrent(concurrent);
}
bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
HeapRegion* hr = heap_region_containing(p);
if (hr == NULL) {
return false;
} else {
return hr->is_in(p);
}
}
// Methods for the mutator alloc region
HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
bool force) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
assert(!force || g1_policy()->can_expand_young_list(),
"if force is true we should be able to expand the young list");
bool young_list_full = g1_policy()->is_young_list_full();
if (force || !young_list_full) {
HeapRegion* new_alloc_region = new_region(word_size,
false /* do_expand */);
if (new_alloc_region != NULL) {
set_region_short_lived_locked(new_alloc_region);
_hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
return new_alloc_region;
}
}
return NULL;
}
void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
assert(alloc_region->is_young(), "all mutator alloc regions should be young");
g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
_summary_bytes_used += allocated_bytes;
_hr_printer.retire(alloc_region);
// We update the eden sizes here, when the region is retired,
// instead of when it's allocated, since this is the point that its
// used space has been recored in _summary_bytes_used.
g1mm()->update_eden_size();
}
HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
bool force) {
return _g1h->new_mutator_alloc_region(word_size, force);
}
void G1CollectedHeap::set_par_threads() {
// Don't change the number of workers. Use the value previously set
// in the workgroup.
assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
uint n_workers = workers()->active_workers();
assert(UseDynamicNumberOfGCThreads ||
n_workers == workers()->total_workers(),
"Otherwise should be using the total number of workers");
if (n_workers == 0) {
assert(false, "Should have been set in prior evacuation pause.");
n_workers = ParallelGCThreads;
workers()->set_active_workers(n_workers);
}
set_par_threads(n_workers);
}
void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
size_t allocated_bytes) {
_g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
}
// Methods for the GC alloc regions
HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
uint count,
GCAllocPurpose ap) {
assert(FreeList_lock->owned_by_self(), "pre-condition");
if (count < g1_policy()->max_regions(ap)) {
HeapRegion* new_alloc_region = new_region(word_size,
true /* do_expand */);
if (new_alloc_region != NULL) {
// We really only need to do this for old regions given that we
// should never scan survivors. But it doesn't hurt to do it
// for survivors too.
new_alloc_region->set_saved_mark();
if (ap == GCAllocForSurvived) {
new_alloc_region->set_survivor();
_hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
} else {
_hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
}
bool during_im = g1_policy()->during_initial_mark_pause();
new_alloc_region->note_start_of_copying(during_im);
return new_alloc_region;
} else {
g1_policy()->note_alloc_region_limit_reached(ap);
}
}
return NULL;
}
void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes,
GCAllocPurpose ap) {
bool during_im = g1_policy()->during_initial_mark_pause();
alloc_region->note_end_of_copying(during_im);
g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
if (ap == GCAllocForSurvived) {
young_list()->add_survivor_region(alloc_region);
} else {
_old_set.add(alloc_region);
}
_hr_printer.retire(alloc_region);
}
HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
bool force) {
assert(!force, "not supported for GC alloc regions");
return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
}
void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
size_t allocated_bytes) {
_g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
GCAllocForSurvived);
}
HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
bool force) {
assert(!force, "not supported for GC alloc regions");
return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
}
void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
size_t allocated_bytes) {
_g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
GCAllocForTenured);
}
// Heap region set verification
class VerifyRegionListsClosure : public HeapRegionClosure {
private:
FreeRegionList* _free_list;
OldRegionSet* _old_set;
HumongousRegionSet* _humongous_set;
uint _region_count;
public:
VerifyRegionListsClosure(OldRegionSet* old_set,
HumongousRegionSet* humongous_set,
FreeRegionList* free_list) :
_old_set(old_set), _humongous_set(humongous_set),
_free_list(free_list), _region_count(0) { }
uint region_count() { return _region_count; }
bool doHeapRegion(HeapRegion* hr) {
_region_count += 1;
if (hr->continuesHumongous()) {
return false;
}
if (hr->is_young()) {
// TODO
} else if (hr->startsHumongous()) {
_humongous_set->verify_next_region(hr);
} else if (hr->is_empty()) {
_free_list->verify_next_region(hr);
} else {
_old_set->verify_next_region(hr);
}
return false;
}
};
HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
HeapWord* bottom) {
HeapWord* end = bottom + HeapRegion::GrainWords;
MemRegion mr(bottom, end);
assert(_g1_reserved.contains(mr), "invariant");
// This might return NULL if the allocation fails
return new HeapRegion(hrs_index, _bot_shared, mr);
}
void G1CollectedHeap::verify_region_sets() {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
// First, check the explicit lists.
_free_list.verify();
{
// Given that a concurrent operation might be adding regions to
// the secondary free list we have to take the lock before
// verifying it.
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
_secondary_free_list.verify();
}
_old_set.verify();
_humongous_set.verify();
// If a concurrent region freeing operation is in progress it will
// be difficult to correctly attributed any free regions we come
// across to the correct free list given that they might belong to
// one of several (free_list, secondary_free_list, any local lists,
// etc.). So, if that's the case we will skip the rest of the
// verification operation. Alternatively, waiting for the concurrent
// operation to complete will have a non-trivial effect on the GC's
// operation (no concurrent operation will last longer than the
// interval between two calls to verification) and it might hide
// any issues that we would like to catch during testing.
if (free_regions_coming()) {
return;
}
// Make sure we append the secondary_free_list on the free_list so
// that all free regions we will come across can be safely
// attributed to the free_list.
append_secondary_free_list_if_not_empty_with_lock();
// Finally, make sure that the region accounting in the lists is
// consistent with what we see in the heap.
_old_set.verify_start();
_humongous_set.verify_start();
_free_list.verify_start();
VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
heap_region_iterate(&cl);
_old_set.verify_end();
_humongous_set.verify_end();
_free_list.verify_end();
}
// Optimized nmethod scanning
class RegisterNMethodOopClosure: public OopClosure {
G1CollectedHeap* _g1h;
nmethod* _nm;
template <class T> void do_oop_work(T* p) {
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
HeapRegion* hr = _g1h->heap_region_containing(obj);
assert(!hr->isHumongous(), "code root in humongous region?");
// HeapRegion::add_strong_code_root() avoids adding duplicate
// entries but having duplicates is OK since we "mark" nmethods
// as visited when we scan the strong code root lists during the GC.
hr->add_strong_code_root(_nm);
assert(hr->rem_set()->strong_code_roots_list_contains(_nm), "add failed?");
}
}
public:
RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
_g1h(g1h), _nm(nm) {}
void do_oop(oop* p) { do_oop_work(p); }
void do_oop(narrowOop* p) { do_oop_work(p); }
};
class UnregisterNMethodOopClosure: public OopClosure {
G1CollectedHeap* _g1h;
nmethod* _nm;
template <class T> void do_oop_work(T* p) {
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
HeapRegion* hr = _g1h->heap_region_containing(obj);
assert(!hr->isHumongous(), "code root in humongous region?");
hr->remove_strong_code_root(_nm);
assert(!hr->rem_set()->strong_code_roots_list_contains(_nm), "remove failed?");
}
}
public:
UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
_g1h(g1h), _nm(nm) {}
void do_oop(oop* p) { do_oop_work(p); }
void do_oop(narrowOop* p) { do_oop_work(p); }
};
void G1CollectedHeap::register_nmethod(nmethod* nm) {
CollectedHeap::register_nmethod(nm);
guarantee(nm != NULL, "sanity");
RegisterNMethodOopClosure reg_cl(this, nm);
nm->oops_do(®_cl);
}
void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
CollectedHeap::unregister_nmethod(nm);
guarantee(nm != NULL, "sanity");
UnregisterNMethodOopClosure reg_cl(this, nm);
nm->oops_do(®_cl, true);
}
class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
public:
bool doHeapRegion(HeapRegion *hr) {
assert(!hr->isHumongous(), "humongous region in collection set?");
hr->migrate_strong_code_roots();
return false;
}
};
void G1CollectedHeap::migrate_strong_code_roots() {
MigrateCodeRootsHeapRegionClosure cl;
double migrate_start = os::elapsedTime();
collection_set_iterate(&cl);
double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
}
// Mark all the code roots that point into regions *not* in the
// collection set.
//
// Note we do not want to use a "marking" CodeBlobToOopClosure while
// walking the the code roots lists of regions not in the collection
// set. Suppose we have an nmethod (M) that points to objects in two
// separate regions - one in the collection set (R1) and one not (R2).
// Using a "marking" CodeBlobToOopClosure here would result in "marking"
// nmethod M when walking the code roots for R1. When we come to scan
// the code roots for R2, we would see that M is already marked and it
// would be skipped and the objects in R2 that are referenced from M
// would not be evacuated.
class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
class MarkStrongCodeRootOopClosure: public OopClosure {
ConcurrentMark* _cm;
HeapRegion* _hr;
uint _worker_id;
template <class T> void do_oop_work(T* p) {
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
// Only mark objects in the region (which is assumed
// to be not in the collection set).
if (_hr->is_in(obj)) {
_cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
}
}
}
public:
MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
_cm(cm), _hr(hr), _worker_id(worker_id) {
assert(!_hr->in_collection_set(), "sanity");
}
void do_oop(narrowOop* p) { do_oop_work(p); }
void do_oop(oop* p) { do_oop_work(p); }
};
MarkStrongCodeRootOopClosure _oop_cl;
public:
MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
_oop_cl(cm, hr, worker_id) {}
void do_code_blob(CodeBlob* cb) {
nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
if (nm != NULL) {
nm->oops_do(&_oop_cl);
}
}
};
class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
uint _worker_id;
public:
MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
_g1h(g1h), _worker_id(worker_id) {}
bool doHeapRegion(HeapRegion *hr) {
HeapRegionRemSet* hrrs = hr->rem_set();
if (hr->isHumongous()) {
// Code roots should never be attached to a humongous region
assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
return false;
}
if (hr->in_collection_set()) {
// Don't mark code roots into regions in the collection set here.
// They will be marked when we scan them.
return false;
}
MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
hr->strong_code_roots_do(&cb_cl);
return false;
}
};
void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
MarkStrongCodeRootsHRClosure cl(this, worker_id);
if (G1CollectedHeap::use_parallel_gc_threads()) {
heap_region_par_iterate_chunked(&cl,
worker_id,
workers()->active_workers(),
HeapRegion::ParMarkRootClaimValue);
} else {
heap_region_iterate(&cl);
}
}
class RebuildStrongCodeRootClosure: public CodeBlobClosure {
G1CollectedHeap* _g1h;
public:
RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
_g1h(g1h) {}
void do_code_blob(CodeBlob* cb) {
nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
if (nm == NULL) {
return;
}
if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
_g1h->register_nmethod(nm);
}
}
};
void G1CollectedHeap::rebuild_strong_code_roots() {
RebuildStrongCodeRootClosure blob_cl(this);
CodeCache::blobs_do(&blob_cl);
}