7085906: Replace the permgen allocated sentinelRef with a self-looped end
Summary: Remove the sentinelRef and let the last Reference in a discovered chain point back to itself.
Reviewed-by: ysr, jmasa
/*
* Copyright (c) 2001, 2011, 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.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/g1MarkSweep.hpp"
#include "gc_implementation/g1/g1OopClosures.inline.hpp"
#include "gc_implementation/g1/g1RemSet.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/isGCActiveMark.hpp"
#include "memory/gcLocker.inline.hpp"
#include "memory/genOopClosures.inline.hpp"
#include "memory/generationSpec.hpp"
#include "oops/oop.inline.hpp"
#include "oops/oop.pcgc.inline.hpp"
#include "runtime/aprofiler.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.)
// 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->concurrentRefineOneCard(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;
hr->set_young();
double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((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;
size_t 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 %d entries, _length is %d",
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 %d",
_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 */);
for (HeapRegion* curr = _survivor_head;
curr != NULL;
curr = curr->get_next_young_region()) {
_g1h->g1_policy()->set_region_survivors(curr);
// 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);
}
_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(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
"age: %4d, y: %d, surv: %d",
curr->bottom(), curr->end(),
curr->top(),
curr->prev_top_at_mark_start(),
curr->next_top_at_mark_start(),
curr->top_at_conc_mark_count(),
curr->age_in_surv_rate_group_cond(),
curr->is_young(),
curr->is_survivor());
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 collecction.
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) {
// perm gen (or null)
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 "SIZE_FORMAT" 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 notifed 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 <= (size_t) 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) {
if (expand(word_size * HeapWordSize)) {
// Even though the heap was expanded, it might not have reached
// the desired size. So, we cannot assume that the allocation
// will succeed.
res = _free_list.remove_head_or_null();
}
}
return res;
}
size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
size_t word_size) {
assert(isHumongous(word_size), "word_size should be humongous");
assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
size_t 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 expasion 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 (size_t 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(size_t first,
size_t 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.
size_t 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 = 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 seriers.
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 (size_t 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 (size_t 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 num_regions =
round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
size_t x_size = expansion_regions();
size_t fs = _hrs.free_suffix();
size_t 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_size >= 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");
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");
}
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;
return attempt_allocation(word_size, &dummy_gc_count_before);
}
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 satisified, or unsatisfied after GC.
for (int try_count = 1; /* 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);
} else {
result = attempt_allocation_humongous(word_size, &gc_count_before);
}
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 {
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) {
// 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()) {
result = _mutator_alloc_region.attempt_allocation_force(word_size,
false /* bot_updates */);
if (result != NULL) {
return result;
}
}
should_try_gc = false;
} else {
// Read the GC count while still holding the Heap_lock.
gc_count_before = SharedHeap::heap()->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 = SharedHeap::heap()->total_collections();
return NULL;
}
} else {
GC_locker::stall_until_clear();
}
// We can reach here if we were unsuccessul 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) {
// 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");
// 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 {
// Read the GC count while still holding the Heap_lock.
gc_count_before = SharedHeap::heap()->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 = SharedHeap::heap()->total_collections();
return NULL;
}
} else {
GC_locker::stall_until_clear();
}
// We can reach here if we were unsuccessul 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 {
return humongous_obj_allocate(word_size);
}
ShouldNotReachHere();
}
class PostMCRemSetClearClosure: public HeapRegionClosure {
ModRefBarrierSet* _mr_bs;
public:
PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
bool doHeapRegion(HeapRegion* r) {
r->reset_gc_time_stamp();
if (r->continuesHumongous())
return false;
HeapRegionRemSet* hrrs = r->rem_set();
if (hrrs != NULL) 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;
}
};
class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
ModRefBarrierSet* _mr_bs;
public:
PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
bool doHeapRegion(HeapRegion* r) {
if (r->continuesHumongous()) return false;
if (r->used_region().word_size() != 0) {
_mr_bs->invalidate(r->used_region(), true /*whole heap*/);
}
return false;
}
};
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(int i) {
RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
_g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
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->capacity() == (size_t) HeapRegion::GrainBytes) {
// 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) { }
};
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;
}
SvcGCMarker sgcm(SvcGCMarker::FULL);
ResourceMark rm;
if (PrintHeapAtGC) {
Universe::print_heap_before_gc();
}
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
bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
assert(!system_gc || explicit_gc, "invariant");
gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
PrintGC, true, gclog_or_tty);
TraceCollectorStats tcs(g1mm()->full_collection_counters());
TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
double start = os::elapsedTime();
g1_policy()->record_full_collection_start();
wait_while_free_regions_coming();
append_secondary_free_list_if_not_empty_with_lock();
gc_prologue(true);
increment_total_collections(true /* full gc */);
size_t g1h_prev_used = used();
assert(used() == recalculate_used(), "Should be equal");
if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyBeforeGC:");
prepare_for_verify();
Universe::verify(/* allow dirty */ true,
/* silent */ false,
/* option */ VerifyOption_G1UsePrevMarking);
}
pre_full_gc_dump();
COMPILER2_PRESENT(DerivedPointerTable::clear());
// We want to discover references, but not process them yet.
// This mode is disabled in
// instanceRefKlass::process_discovered_references if the
// generation does some collection work, or
// instanceRefKlass::enqueue_discovered_references if the
// generation returns without doing any work.
ref_processor()->disable_discovery();
ref_processor()->abandon_partial_discovery();
ref_processor()->verify_no_references_recorded();
// Abandon current iterations of concurrent marking and concurrent
// refinement, if any are in progress.
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();
tear_down_region_lists();
// 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();
empty_young_list();
g1_policy()->set_full_young_gcs(true);
// See the comment in G1CollectedHeap::ref_processing_init() about
// how reference processing currently works in G1.
// Temporarily make reference _discovery_ single threaded (non-MT).
ReferenceProcessorMTDiscoveryMutator rp_disc_ser(ref_processor(), false);
// Temporarily make refs discovery atomic
ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true);
// Temporarily clear _is_alive_non_header
ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL);
ref_processor()->enable_discovery();
ref_processor()->setup_policy(do_clear_all_soft_refs);
// Do collection work
{
HandleMark hm; // Discard invalid handles created during gc
G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs);
}
assert(free_regions() == 0, "we should not have added any free regions");
rebuild_region_lists();
_summary_bytes_used = recalculate_used();
ref_processor()->enqueue_discovered_references();
COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
MemoryService::track_memory_usage();
if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyAfterGC:");
prepare_for_verify();
Universe::verify(/* allow dirty */ false,
/* silent */ false,
/* option */ VerifyOption_G1UsePrevMarking);
}
NOT_PRODUCT(ref_processor()->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 remebered
// sets. We will also reset the GC time stamps of the regions.
PostMCRemSetClearClosure rs_clear(mr_bs());
heap_region_iterate(&rs_clear);
// 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.
PostCompactionPrinterClosure cl(hr_printer());
heap_region_iterate(&cl);
_hr_printer.end_gc(true /* full */, (size_t) total_collections());
}
if (_cg1r->use_cache()) {
_cg1r->clear_and_record_card_counts();
_cg1r->clear_hot_cache();
}
// Rebuild remembered sets of all regions.
if (G1CollectedHeap::use_parallel_gc_threads()) {
ParRebuildRSTask rebuild_rs_task(this);
assert(check_heap_region_claim_values(
HeapRegion::InitialClaimValue), "sanity check");
set_par_threads(workers()->total_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);
}
if (PrintGC) {
print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
}
if (true) { // FIXME
// Ask the permanent generation to adjust size for full collections
perm()->compute_new_size();
}
// 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();
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
gc_epilogue(true);
// 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_full_collections_completed(false /* concurrent */);
_hrs.verify_optional();
verify_region_sets_optional();
if (PrintHeapAtGC) {
Universe::print_heap_after_gc();
}
g1mm()->update_counters();
post_full_gc_dump();
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 (PrintGC && Verbose) {
const double free_percentage =
(double) free_after_gc / (double) capacity_after_gc;
gclog_or_tty->print_cr("Computing new size after full GC ");
gclog_or_tty->print_cr(" "
" minimum_free_percentage: %6.2f",
minimum_free_percentage);
gclog_or_tty->print_cr(" "
" maximum_free_percentage: %6.2f",
maximum_free_percentage);
gclog_or_tty->print_cr(" "
" capacity: %6.1fK"
" minimum_desired_capacity: %6.1fK"
" maximum_desired_capacity: %6.1fK",
(double) capacity_after_gc / (double) K,
(double) minimum_desired_capacity / (double) K,
(double) maximum_desired_capacity / (double) K);
gclog_or_tty->print_cr(" "
" free_after_gc: %6.1fK"
" used_after_gc: %6.1fK",
(double) free_after_gc / (double) K,
(double) used_after_gc / (double) K);
gclog_or_tty->print_cr(" "
" free_percentage: %6.2f",
free_percentage);
}
if (capacity_after_gc < minimum_desired_capacity) {
// Don't expand unless it's significant
size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
if (expand(expand_bytes)) {
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" expanding:"
" max_heap_size: %6.1fK"
" minimum_desired_capacity: %6.1fK"
" expand_bytes: %6.1fK",
(double) max_heap_size / (double) K,
(double) minimum_desired_capacity / (double) K,
(double) expand_bytes / (double) K);
}
}
// 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;
shrink(shrink_bytes);
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" shrinking:"
" min_heap_size: %6.1fK"
" maximum_desired_capacity: %6.1fK"
" shrink_bytes: %6.1fK",
(double) min_heap_size / (double) K,
(double) maximum_desired_capacity / (double) K,
(double) shrink_bytes / (double) K);
}
}
}
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);
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());
}
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);
if (Verbose && PrintGC) {
gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK",
old_mem_size/K, aligned_expand_bytes/K);
}
// 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");
}
} else {
// 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, "G1 heap expansion");
}
}
if (Verbose && PrintGC) {
size_t new_mem_size = _g1_storage.committed_size();
gclog_or_tty->print_cr("...%s, expanded to %ldK",
(successful ? "Successful" : "Failed"),
new_mem_size/K);
}
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);
size_t num_regions_deleted = 0;
MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
HeapWord* old_end = (HeapWord*) _g1_storage.high();
assert(mr.end() == old_end, "post-condition");
if (mr.byte_size() > 0) {
if (_hr_printer.is_active()) {
HeapWord* curr = mr.end();
while (curr > mr.start()) {
HeapWord* curr_end = curr;
curr -= HeapRegion::GrainWords;
_hr_printer.uncommit(curr, curr_end);
}
assert(curr == mr.start(), "post-condition");
}
_g1_storage.shrink_by(mr.byte_size());
HeapWord* new_end = (HeapWord*) _g1_storage.high();
assert(mr.start() == new_end, "post-condition");
_expansion_regions += num_regions_deleted;
update_committed_space(old_end, new_end);
HeapRegionRemSet::shrink_heap(n_regions());
if (Verbose && PrintGC) {
size_t new_mem_size = _g1_storage.committed_size();
gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
old_mem_size/K, aligned_shrink_bytes/K,
new_mem_size/K);
}
}
}
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_lists(); // We will rebuild them in a moment.
shrink_helper(shrink_bytes);
rebuild_region_lists();
_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(this),
_ref_processor(NULL),
_process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
_bot_shared(NULL),
_objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
_evac_failure_scan_stack(NULL) ,
_mark_in_progress(false),
_cg1r(NULL), _summary_bytes_used(0),
_refine_cte_cl(NULL),
_full_collection(false),
_free_list("Master Free List"),
_secondary_free_list("Secondary Free List"),
_humongous_set("Master Humongous Set"),
_free_regions_coming(false),
_young_list(new YoungList(this)),
_gc_time_stamp(0),
_retained_old_gc_alloc_region(NULL),
_surviving_young_words(NULL),
_full_collections_completed(0),
_in_cset_fast_test(NULL),
_in_cset_fast_test_base(NULL),
_dirty_cards_region_list(NULL) {
_g1h = this; // To catch bugs.
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.");
HeapRegionRemSetIterator** iter_arr =
NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
for (int i = 0; i < n_queues; i++) {
iter_arr[i] = new HeapRegionRemSetIterator();
}
_rem_set_iterator = iter_arr;
for (int i = 0; i < n_queues; i++) {
RefToScanQueue* q = new RefToScanQueue();
q->initialize();
_task_queues->register_queue(i, q);
}
guarantee(_task_queues != NULL, "task_queues allocation failure.");
}
jint G1CollectedHeap::initialize() {
CollectedHeap::pre_initialize();
os::enable_vtime();
// 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();
// Reserve the maximum.
PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
// Includes the perm-gen.
// 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), we also need to align the perm gen size as it might not be.
const size_t total_reserved = max_byte_size +
align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
UseLargePages, addr);
if (UseCompressedOops) {
if (addr != NULL && !heap_rs.is_reserved()) {
// Failed to reserve at specified address - the requested memory
// region is taken already, for example, by 'java' launcher.
// Try again to reserver heap higher.
addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
UseLargePages, addr);
if (addr != NULL && !heap_rs0.is_reserved()) {
// Failed to reserve at specified address again - give up.
addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
assert(addr == NULL, "");
ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
UseLargePages, addr);
heap_rs = heap_rs1;
} else {
heap_rs = heap_rs0;
}
}
}
if (!heap_rs.is_reserved()) {
vm_exit_during_initialization("Could not reserve enough space for object heap");
return JNI_ENOMEM;
}
// It is important to do this in a way such that concurrent readers can't
// temporarily think somethings 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 = 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);
ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
_perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
_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);
// 6843694 - ensure that the maximum region index can fit
// in the remembered set structures.
const size_t max_region_idx = ((size_t)1 << (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((size_t) 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, _in_cset_fast_test_length);
// 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 -
((size_t) _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(heap_rs, (int) max_regions());
_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_exit_during_initialization("Failed to allocate initial heap.");
return JNI_ENOMEM;
}
// Perform any initialization actions delegated to the policy.
g1_policy()->init();
g1_policy()->note_start_of_mark_thread();
_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();
// Do later initialization work for concurrent refinement.
_cg1r->init();
// 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, &_g1_storage);
return JNI_OK;
}
void G1CollectedHeap::ref_processing_init() {
// Reference processing in G1 currently works as follows:
//
// * There is only one reference processor instance that
// 'spans' the entire heap. It is created by the code
// below.
// * Reference discovery is not enabled during an incremental
// pause (see 6484982).
// * Discoverered refs are not enqueued nor are they processed
// during an incremental pause (see 6484982).
// * 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 is currently not MT (see 6608385).
// * A full GC enables (non-MT) reference discovery and
// processes any discovered references.
SharedHeap::ref_processing_init();
MemRegion mr = reserved_region();
_ref_processor =
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, // is alive closure for efficiency
true); // Setting next fields of discovered
// lists requires a barrier.
}
size_t G1CollectedHeap::capacity() const {
return _g1_committed.byte_size();
}
void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
DirtyCardQueue* into_cset_dcq,
bool concurrent,
int worker_i) {
// Clean cards in the hot card cache
concurrent_g1_refine()->clean_up_cache(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()->record_update_rs_processed_buffers(worker_i,
(double) 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) {
return
((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
(cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
}
#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_full_collections_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.
// We have already incremented _total_full_collections at the start
// of the GC, so total_full_collections() represents how many full
// collections have been started.
unsigned int full_collections_started = total_full_collections();
// 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 ||
(full_collections_started == _full_collections_completed + 1) ||
(full_collections_started == _full_collections_completed + 2),
err_msg("for inner caller (Full GC): full_collections_started = %u "
"is inconsistent with _full_collections_completed = %u",
full_collections_started, _full_collections_completed));
// This is the case for the outer caller, i.e. the concurrent cycle.
assert(!concurrent ||
(full_collections_started == _full_collections_completed + 1),
err_msg("for outer caller (concurrent cycle): "
"full_collections_started = %u "
"is inconsistent with _full_collections_completed = %u",
full_collections_started, _full_collections_completed));
_full_collections_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 cyle 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::collect_as_vm_thread(GCCause::Cause cause) {
assert_at_safepoint(true /* should_be_vm_thread */);
GCCauseSetter gcs(this, cause);
switch (cause) {
case GCCause::_heap_inspection:
case GCCause::_heap_dump: {
HandleMark hm;
do_full_collection(false); // don't clear all soft refs
break;
}
default: // XXX FIX ME
ShouldNotReachHere(); // Unexpected use of this function
}
}
void G1CollectedHeap::collect(GCCause::Cause cause) {
// The caller doesn't have the Heap_lock
assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
unsigned int gc_count_before;
unsigned int full_gc_count_before;
{
MutexLocker ml(Heap_lock);
// Read the GC count while holding the Heap_lock
gc_count_before = SharedHeap::heap()->total_collections();
full_gc_count_before = SharedHeap::heap()->total_full_collections();
}
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);
} 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, full_gc_count_before, cause);
VMThread::execute(&op);
}
}
}
bool G1CollectedHeap::is_in(const void* p) const {
HeapRegion* hr = _hrs.addr_to_region((HeapWord*) p);
if (hr != NULL) {
return hr->is_in(p);
} else {
return _perm_gen->as_gen()->is_in(p);
}
}
// Iteration functions.
// Iterates an OopClosure over all ref-containing fields of objects
// within a HeapRegion.
class IterateOopClosureRegionClosure: public HeapRegionClosure {
MemRegion _mr;
OopClosure* _cl;
public:
IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
: _mr(mr), _cl(cl) {}
bool doHeapRegion(HeapRegion* r) {
if (! r->continuesHumongous()) {
r->oop_iterate(_cl);
}
return false;
}
};
void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
IterateOopClosureRegionClosure blk(_g1_committed, cl);
heap_region_iterate(&blk);
if (do_perm) {
perm_gen()->oop_iterate(cl);
}
}
void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
IterateOopClosureRegionClosure blk(mr, cl);
heap_region_iterate(&blk);
if (do_perm) {
perm_gen()->oop_iterate(cl);
}
}
// 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, bool do_perm) {
IterateObjectClosureRegionClosure blk(cl);
heap_region_iterate(&blk);
if (do_perm) {
perm_gen()->object_iterate(cl);
}
}
void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
// FIXME: is this right?
guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
}
// 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_iterate_from(HeapRegion* r,
HeapRegionClosure* cl) const {
_hrs.iterate_from(r, cl);
}
void
G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
int worker,
jint claim_value) {
const size_t regions = n_regions();
const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1);
// try to spread out the starting points of the workers
const size_t start_index = regions / worker_num * (size_t) worker;
// each worker will actually look at all regions
for (size_t count = 0; count < regions; ++count) {
const size_t 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 (size_t 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;
}
// Noone 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; noone 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);
}
#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;
size_t _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 ["PTR_FORMAT","PTR_FORMAT"), "
"claim value = %d, should be %d",
r->bottom(), r->end(), 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 ["PTR_FORMAT","PTR_FORMAT"), "
"HS = "PTR_FORMAT", should be "PTR_FORMAT,
r->bottom(), r->end(),
r->humongous_start_region(),
_sh_region);
++_failures;
}
}
return false;
}
size_t 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;
}
#endif // ASSERT
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);
if (res == NULL)
res = perm_gen()->space_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 accomodate
// 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();
}
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(&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 _allow_dirty;
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 allow_dirty, bool par, VerifyOption vo)
: _allow_dirty(allow_dirty),
_par(par),
_vo(vo),
_failures(false) {}
bool failures() {
return _failures;
}
bool doHeapRegion(HeapRegion* r) {
guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
"Should be unclaimed at verify points.");
if (!r->continuesHumongous()) {
bool failures = false;
r->verify(_allow_dirty, _vo, &failures);
if (failures) {
_failures = true;
} else {
VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
r->object_iterate(¬_dead_yet_cl);
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;
}
}
}
return false; // stop the region iteration if we hit a failure
}
};
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); }
};
// This is the task used for parallel heap verification.
class G1ParVerifyTask: public AbstractGangTask {
private:
G1CollectedHeap* _g1h;
bool _allow_dirty;
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, bool allow_dirty, VerifyOption vo) :
AbstractGangTask("Parallel verify task"),
_g1h(g1h),
_allow_dirty(allow_dirty),
_vo(vo),
_failures(false) { }
bool failures() {
return _failures;
}
void work(int worker_i) {
HandleMark hm;
VerifyRegionClosure blk(_allow_dirty, true, _vo);
_g1h->heap_region_par_iterate_chunked(&blk, worker_i,
HeapRegion::ParVerifyClaimValue);
if (blk.failures()) {
_failures = true;
}
}
};
void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
verify(allow_dirty, silent, VerifyOption_G1UsePrevMarking);
}
void G1CollectedHeap::verify(bool allow_dirty,
bool silent,
VerifyOption vo) {
if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
VerifyRootsClosure rootsCl(vo);
CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
// We apply the relevant closures to all the oops in the
// system dictionary, the string table and the code cache.
const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
process_strong_roots(true, // activate StrongRootsScope
true, // we set "collecting perm gen" to true,
// so we don't reset the dirty cards in the perm gen.
SharedHeap::ScanningOption(so), // roots scanning options
&rootsCl,
&blobsCl,
&rootsCl);
// If we're verifying after the marking phase of a Full GC then we can't
// treat the perm gen as roots into the G1 heap. Some of the objects in
// the perm gen may be dead and hence not marked. If one of these dead
// objects is considered to be a root then we may end up with a false
// "Root location <x> points to dead ob <y>" failure.
if (vo != VerifyOption_G1UseMarkWord) {
// Since we used "collecting_perm_gen" == true above, we will not have
// checked the refs from perm into the G1-collected heap. We check those
// references explicitly below. Whether the relevant cards are dirty
// is checked further below in the rem set verification.
if (!silent) { gclog_or_tty->print("Permgen roots "); }
perm_gen()->oop_iterate(&rootsCl);
}
bool failures = rootsCl.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, allow_dirty, vo);
int n_workers = workers()->total_workers();
set_par_threads(n_workers);
workers()->run_task(&task);
set_par_threads(0);
if (task.failures()) {
failures = true;
}
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(allow_dirty, 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:");
print_on(gclog_or_tty, true /* extended */);
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, heapRegions, remset) ");
}
}
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() const { print_on(tty); }
void G1CollectedHeap::print_on(outputStream* st) const {
print_on(st, PrintHeapAtGCExtended);
}
void G1CollectedHeap::print_on(outputStream* st, bool extended) 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);
size_t young_regions = _young_list->length();
st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
young_regions, young_regions * HeapRegion::GrainBytes / K);
size_t survivor_regions = g1_policy()->recorded_survivor_regions();
st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
st->cr();
perm()->as_gen()->print_on(st);
if (extended) {
st->cr();
print_on_extended(st);
}
}
void G1CollectedHeap::print_on_extended(outputStream* st) const {
PrintRegionClosure blk(st);
heap_region_iterate(&blk);
}
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);
st->cr();
}
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");
// Call allocation profiler
AllocationProfiler::iterate_since_last_gc();
// Fill TLAB's and such
ensure_parsability(true);
}
void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
// 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;
}
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();
}
}
// <NEW PREDICTION>
double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
bool young) {
return _g1_policy->predict_region_elapsed_time_ms(hr, young);
}
void G1CollectedHeap::check_if_region_is_too_expensive(double
predicted_time_ms) {
_g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
}
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();
return buffer_size * buffer_num + extra_cards;
}
size_t G1CollectedHeap::max_pending_card_num() {
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
size_t buffer_size = dcqs.buffer_size();
size_t buffer_num = dcqs.completed_buffers_num();
int thread_num = Threads::number_of_threads();
return (buffer_num + thread_num) * buffer_size;
}
size_t G1CollectedHeap::cards_scanned() {
return g1_rem_set()->cardsScanned();
}
void
G1CollectedHeap::setup_surviving_young_words() {
guarantee( _surviving_young_words == NULL, "pre-condition" );
size_t array_length = g1_policy()->young_cset_length();
_surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
if (_surviving_young_words == NULL) {
vm_exit_out_of_memory(sizeof(size_t) * array_length,
"Not enough space for young surv words summary.");
}
memset(_surviving_young_words, 0, array_length * sizeof(size_t));
#ifdef ASSERT
for (size_t 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);
size_t array_length = g1_policy()->young_cset_length();
for (size_t 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);
_surviving_young_words = NULL;
}
// </NEW PREDICTION>
#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
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;
}
SvcGCMarker sgcm(SvcGCMarker::MINOR);
ResourceMark rm;
if (PrintHeapAtGC) {
Universe::print_heap_before_gc();
}
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();
char verbose_str[128];
sprintf(verbose_str, "GC pause ");
if (g1_policy()->full_young_gcs()) {
strcat(verbose_str, "(young)");
} else {
strcat(verbose_str, "(partial)");
}
if (g1_policy()->during_initial_mark_pause()) {
strcat(verbose_str, " (initial-mark)");
// We are about to start a marking cycle, so we increment the
// full collection counter.
increment_total_full_collections();
}
// if PrintGCDetails is on, we'll print long statistics information
// in the collector policy code, so let's not print this as the output
// is messy if we do.
gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
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");
{ // 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();
if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyBeforeGC:");
prepare_for_verify();
Universe::verify(/* allow dirty */ false,
/* silent */ false,
/* option */ VerifyOption_G1UsePrevMarking);
}
COMPILER2_PRESENT(DerivedPointerTable::clear());
// Please see comment in G1CollectedHeap::ref_processing_init()
// to see how reference processing currently works in G1.
//
// We want to turn off ref discovery, if necessary, and turn it back on
// on again later if we do. XXX Dubious: why is discovery disabled?
bool was_enabled = ref_processor()->discovery_enabled();
if (was_enabled) ref_processor()->disable_discovery();
// 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());
// The elapsed time induced by the start time below deliberately elides
// the possible verification above.
double start_time_sec = os::elapsedTime();
size_t start_used_bytes = used();
#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(start_time_sec,
start_used_bytes);
#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();
}
perm_gen()->save_marks();
// We must do this before any possible evacuation that should propagate
// marks.
if (mark_in_progress()) {
double start_time_sec = os::elapsedTime();
_cm->drainAllSATBBuffers();
double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
g1_policy()->record_satb_drain_time(finish_mark_ms);
}
// Record the number of elements currently on the mark stack, so we
// only iterate over these. (Since evacuation may add to the mark
// stack, doing more exposes race conditions.) If no mark is in
// progress, this will be zero.
_cm->set_oops_do_bound();
if (mark_in_progress()) {
concurrent_mark()->newCSet();
}
#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()->choose_collection_set(target_pause_time_ms);
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();
}
}
// We have chosen the complete collection set. If marking is
// active then, we clear the region fields of any of the
// concurrent marking tasks whose region fields point into
// the collection set as these values will become stale. This
// will cause the owning marking threads to claim a new region
// when marking restarts.
if (mark_in_progress()) {
concurrent_mark()->reset_active_task_region_fields_in_cset();
}
#ifdef ASSERT
VerifyCSetClosure cl;
collection_set_iterate(&cl);
#endif // ASSERT
setup_surviving_young_words();
// Initialize the GC alloc regions.
init_gc_alloc_regions();
// Actually do the work...
evacuate_collection_set();
free_collection_set(g1_policy()->collection_set());
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();
} 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()) {
concurrent_mark()->checkpointRootsInitialPost();
set_marking_started();
// 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();
}
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();
double end_time_sec = os::elapsedTime();
double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
g1_policy()->record_pause_time_ms(pause_time_ms);
g1_policy()->record_collection_pause_end();
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();
if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyAfterGC:");
prepare_for_verify();
Universe::verify(/* allow dirty */ true,
/* silent */ false,
/* option */ VerifyOption_G1UsePrevMarking);
}
if (was_enabled) ref_processor()->enable_discovery();
{
size_t expand_bytes = g1_policy()->expansion_amount();
if (expand_bytes > 0) {
size_t bytes_before = capacity();
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 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());
// We have to do this after we decide whether to expand the heap or not.
g1_policy()->print_heap_transition();
if (mark_in_progress()) {
concurrent_mark()->update_g1_committed();
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
gc_epilogue(false);
}
if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
print_tracing_info();
vm_exit(-1);
}
}
_hrs.verify_optional();
verify_region_sets_optional();
TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
if (PrintHeapAtGC) {
Universe::print_heap_after_gc();
}
g1mm()->update_counters();
if (G1SummarizeRSetStats &&
(G1SummarizeRSetStatsPeriod > 0) &&
(total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
g1_rem_set()->print_summary_info();
}
return true;
}
size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
{
size_t gclab_word_size;
switch (purpose) {
case GCAllocForSurvived:
gclab_word_size = YoungPLABSize;
break;
case GCAllocForTenured:
gclab_word_size = OldPLABSize;
break;
default:
assert(false, "unknown GCAllocPurpose");
gclab_word_size = OldPLABSize;
break;
}
return 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() {
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 subseqently 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();
_old_gc_alloc_region.set(retained_region);
_hr_printer.reuse(retained_region);
}
}
void G1CollectedHeap::release_gc_alloc_regions() {
_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();
}
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) 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;
}
// *** Sequential G1 Evacuation
class G1IsAliveClosure: public BoolObjectClosure {
G1CollectedHeap* _g1;
public:
G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
void do_object(oop p) { assert(false, "Do not call."); }
bool do_object_b(oop p) {
// It is reachable if it is outside the collection set, or is inside
// and forwarded.
#ifdef G1_DEBUG
gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d",
(void*) p, _g1->obj_in_cs(p), p->is_forwarded(),
!_g1->obj_in_cs(p) || p->is_forwarded());
#endif // G1_DEBUG
return !_g1->obj_in_cs(p) || p->is_forwarded();
}
};
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;
#ifdef G1_DEBUG
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT,
p, (void*) obj, (void*) *p);
}
#endif // G1_DEBUG
if (_g1->obj_in_cs(obj)) {
assert( obj->is_forwarded(), "invariant" );
*p = obj->forwardee();
#ifdef G1_DEBUG
gclog_or_tty->print_cr(" in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT,
(void*) obj, (void*) *p);
#endif // G1_DEBUG
}
}
};
class UpdateRSetDeferred : public OopsInHeapRegionClosure {
private:
G1CollectedHeap* _g1;
DirtyCardQueue *_dcq;
CardTableModRefBS* _ct_bs;
public:
UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
_g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
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) {
assert(_from->is_in_reserved(p), "paranoia");
if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
!_from->is_survivor()) {
size_t card_index = _ct_bs->index_for(p);
if (_ct_bs->mark_card_deferred(card_index)) {
_dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
}
}
}
};
class RemoveSelfPointerClosure: public ObjectClosure {
private:
G1CollectedHeap* _g1;
ConcurrentMark* _cm;
HeapRegion* _hr;
size_t _prev_marked_bytes;
size_t _next_marked_bytes;
OopsInHeapRegionClosure *_cl;
public:
RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
OopsInHeapRegionClosure* cl) :
_g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0),
_next_marked_bytes(0), _cl(cl) {}
size_t prev_marked_bytes() { return _prev_marked_bytes; }
size_t next_marked_bytes() { return _next_marked_bytes; }
// <original comment>
// The original idea here was to coalesce evacuated and dead objects.
// However that caused complications with the block offset table (BOT).
// In particular if there were two TLABs, one of them partially refined.
// |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
// The BOT entries of the unrefined part of TLAB_2 point to the start
// of TLAB_2. If the last object of the TLAB_1 and the first object
// of TLAB_2 are coalesced, then the cards of the unrefined part
// would point into middle of the filler object.
// The current approach is to not coalesce and leave the BOT contents intact.
// </original comment>
//
// We now reset the BOT when we start the object iteration over the
// region and refine its entries for every object we come across. So
// the above comment is not really relevant and we should be able
// to coalesce dead objects if we want to.
void do_object(oop obj) {
HeapWord* obj_addr = (HeapWord*) obj;
assert(_hr->is_in(obj_addr), "sanity");
size_t obj_size = obj->size();
_hr->update_bot_for_object(obj_addr, obj_size);
if (obj->is_forwarded() && obj->forwardee() == obj) {
// The object failed to move.
assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
_cm->markPrev(obj);
assert(_cm->isPrevMarked(obj), "Should be marked!");
_prev_marked_bytes += (obj_size * HeapWordSize);
if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
_cm->markAndGrayObjectIfNecessary(obj);
}
obj->set_mark(markOopDesc::prototype());
// While we were processing RSet buffers during the
// collection, we actually didn't scan any cards on the
// collection set, since we didn't want to update remebered
// sets with entries that point into the collection set, given
// that live objects fromthe collection set are about to move
// and such entries will be stale very soon. This change also
// dealt with a reliability issue which involved scanning a
// card in the collection set and coming across an array that
// was being chunked and looking malformed. The problem is
// that, if evacuation fails, we might have remembered set
// entries missing given that we skipped cards on the
// collection set. So, we'll recreate such entries now.
obj->oop_iterate(_cl);
assert(_cm->isPrevMarked(obj), "Should be marked!");
} else {
// The object has been either evacuated or is dead. Fill it with a
// dummy object.
MemRegion mr((HeapWord*)obj, obj_size);
CollectedHeap::fill_with_object(mr);
_cm->clearRangeBothMaps(mr);
}
}
};
void G1CollectedHeap::remove_self_forwarding_pointers() {
UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
UpdateRSetDeferred deferred_update(_g1h, &dcq);
OopsInHeapRegionClosure *cl;
if (G1DeferredRSUpdate) {
cl = &deferred_update;
} else {
cl = &immediate_update;
}
HeapRegion* cur = g1_policy()->collection_set();
while (cur != NULL) {
assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
assert(!cur->isHumongous(), "sanity");
if (cur->evacuation_failed()) {
assert(cur->in_collection_set(), "bad CS");
RemoveSelfPointerClosure rspc(_g1h, cur, cl);
// In the common case we make sure that this is done when the
// region is freed so that it is "ready-to-go" when it's
// re-allocated. However, when evacuation failure happens, a
// region will remain in the heap and might ultimately be added
// to a CSet in the future. So we have to be careful here and
// make sure the region's RSet is ready for parallel iteration
// whenever this might be required in the future.
cur->rem_set()->reset_for_par_iteration();
cur->reset_bot();
cl->set_region(cur);
cur->object_iterate(&rspc);
// A number of manipulations to make the TAMS be the current top,
// and the marked bytes be the ones observed in the iteration.
if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
// The comments below are the postconditions achieved by the
// calls. Note especially the last such condition, which says that
// the count of marked bytes has been properly restored.
cur->note_start_of_marking(false);
// _next_top_at_mark_start == top, _next_marked_bytes == 0
cur->add_to_marked_bytes(rspc.prev_marked_bytes());
// _next_marked_bytes == prev_marked_bytes.
cur->note_end_of_marking();
// _prev_top_at_mark_start == top(),
// _prev_marked_bytes == prev_marked_bytes
}
// If there is no mark in progress, we modified the _next variables
// above needlessly, but harmlessly.
if (_g1h->mark_in_progress()) {
cur->note_start_of_marking(false);
// _next_top_at_mark_start == top, _next_marked_bytes == 0
// _next_marked_bytes == next_marked_bytes.
}
// Now make sure the region has the right index in the sorted array.
g1_policy()->note_change_in_marked_bytes(cur);
}
cur = cur->next_in_collection_set();
}
assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
// Now restore saved marks, if any.
if (_objs_with_preserved_marks != NULL) {
assert(_preserved_marks_of_objs != NULL, "Both or none.");
guarantee(_objs_with_preserved_marks->length() ==
_preserved_marks_of_objs->length(), "Both or none.");
for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
oop obj = _objs_with_preserved_marks->at(i);
markOop m = _preserved_marks_of_objs->at(i);
obj->set_mark(m);
}
// Delete the preserved marks growable arrays (allocated on the C heap).
delete _objs_with_preserved_marks;
delete _preserved_marks_of_objs;
_objs_with_preserved_marks = NULL;
_preserved_marks_of_objs = NULL;
}
}
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(OopsInHeapRegionClosure* cl,
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.
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) {
set_evacuation_failed(true);
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)) {
if (_objs_with_preserved_marks == NULL) {
assert(_preserved_marks_of_objs == NULL, "Both or none.");
_objs_with_preserved_marks =
new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
_preserved_marks_of_objs =
new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
}
_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;
}
#ifndef PRODUCT
bool GCLabBitMapClosure::do_bit(size_t offset) {
HeapWord* addr = _bitmap->offsetToHeapWord(offset);
guarantee(_cm->isMarked(oop(addr)), "it should be!");
return true;
}
#endif // PRODUCT
G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
ParGCAllocBuffer(gclab_word_size),
_should_mark_objects(false),
_bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
_retired(false)
{
//_should_mark_objects is set to true when G1ParCopyHelper needs to
// mark the forwarded location of an evacuated object.
// We set _should_mark_objects to true if marking is active, i.e. when we
// need to propagate a mark, or during an initial mark pause, i.e. when we
// need to mark objects immediately reachable by the roots.
if (G1CollectedHeap::heap()->mark_in_progress() ||
G1CollectedHeap::heap()->g1_policy()->during_initial_mark_pause()) {
_should_mark_objects = true;
}
}
G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int 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
size_t real_length = 1 + _g1h->g1_policy()->young_cset_length();
size_t array_length = PADDING_ELEM_NUM +
real_length +
PADDING_ELEM_NUM;
_surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
if (_surviving_young_words_base == NULL)
vm_exit_out_of_memory(array_length * sizeof(size_t),
"Not enough space for young surv histo.");
_surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
memset(_surviving_young_words, 0, 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() {
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),
_during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
_mark_in_progress(_g1->mark_in_progress()) { }
template <class T> void G1ParCopyHelper::mark_object(T* p) {
// This is called from do_oop_work for objects that are not
// in the collection set. Objects in the collection set
// are marked after they have been evacuated.
T heap_oop = oopDesc::load_heap_oop(p);
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop(heap_oop);
HeapWord* addr = (HeapWord*)obj;
if (_g1->is_in_g1_reserved(addr)) {
_cm->grayRoot(oop(addr));
}
}
}
oop G1ParCopyHelper::copy_to_survivor_space(oop old, bool should_mark_copy) {
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);
oop obj = oop(obj_ptr);
if (obj_ptr == NULL) {
// This will either forward-to-self, or detect that someone else has
// installed a forwarding pointer.
OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
return _g1->handle_evacuation_failure_par(cl, old);
}
// 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);
}
// Mark the evacuated object or propagate "next" mark bit
if (should_mark_copy) {
if (!use_local_bitmaps ||
!_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
// if we couldn't mark it on the local bitmap (this happens when
// the object was not allocated in the GCLab), we have to bite
// the bullet and do the standard parallel mark
_cm->markAndGrayObjectIfNecessary(obj);
}
if (_g1->isMarkedNext(old)) {
// Unmark the object's old location so that marking
// doesn't think the old object is alive.
_cm->nextMarkBitMap()->parClear((HeapWord*)old);
}
}
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) {
arrayOop(old)->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 <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 nonNull");
// Marking:
// If the object is in the collection set, then the thread
// that copies the object should mark, or propagate the
// mark to, the evacuated object.
// If the object is not in the collection set then we
// should call the mark_object() method depending on the
// value of the template parameter do_mark_object (which will
// be true for root scanning closures during an initial mark
// pause).
// The mark_object() method first checks whether the object
// is marked and, if not, attempts to mark the object.
// here the null check is implicit in the cset_fast_test() test
if (_g1->in_cset_fast_test(obj)) {
if (obj->is_forwarded()) {
oopDesc::encode_store_heap_oop(p, obj->forwardee());
// If we are a root scanning closure during an initial
// mark pause (i.e. do_mark_object will be true) then
// we also need to handle marking of roots in the
// event of an evacuation failure. In the event of an
// evacuation failure, the object is forwarded to itself
// and not copied so let's mark it here.
if (do_mark_object && obj->forwardee() == obj) {
mark_object(p);
}
} else {
// We need to mark the copied object if we're a root scanning
// closure during an initial mark pause (i.e. do_mark_object
// will be true), or the object is already marked and we need
// to propagate the mark to the evacuated copy.
bool should_mark_copy = do_mark_object ||
_during_initial_mark ||
(_mark_in_progress && !_g1->is_obj_ill(obj));
oop copy_oop = copy_to_survivor_space(obj, should_mark_copy);
oopDesc::encode_store_heap_oop(p, copy_oop);
}
// When scanning the RS, we only care about objs in CS.
if (barrier == G1BarrierRS) {
_par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
}
} 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) {
mark_object(p);
}
}
if (barrier == G1BarrierEvac && obj != NULL) {
_par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
}
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 old = clear_partial_array_mask(p);
assert(old->is_objArray(), "must be obj array");
assert(old->is_forwarded(), "must be forwarded");
assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
objArrayOop obj = objArrayOop(old->forwardee());
assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
// Process ParGCArrayScanChunk elements now
// and push the remainder back onto queue
int start = arrayOop(old)->length();
int end = obj->length();
int remainder = end - start;
assert(start <= end, "just checking");
if (remainder > 2 * ParGCArrayScanChunk) {
// Test above combines last partial chunk with a full chunk
end = start + ParGCArrayScanChunk;
arrayOop(old)->set_length(end);
// Push remainder.
oop* old_p = set_partial_array_mask(old);
assert(arrayOop(old)->length() < obj->length(), "Empty push?");
_par_scan_state->push_on_queue(old_p);
} else {
// Restore length so that the heap remains parsable in
// case of evacuation failure.
arrayOop(old)->set_length(end);
}
_scanner.set_region(_g1->heap_region_containing_raw(obj));
// process our set of indices (include header in first chunk)
obj->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 G1ParTask : public AbstractGangTask {
protected:
G1CollectedHeap* _g1h;
RefToScanQueueSet *_queues;
ParallelTaskTerminator _terminator;
int _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, int workers, RefToScanQueueSet *task_queues)
: AbstractGangTask("G1 collection"),
_g1h(g1h),
_queues(task_queues),
_terminator(workers, _queues),
_stats_lock(Mutex::leaf, "parallel G1 stats lock", true),
_n_workers(workers)
{}
RefToScanQueueSet* queues() { return _queues; }
RefToScanQueue *work_queue(int i) {
return queues()->queue(i);
}
void work(int i) {
if (i >= _n_workers) return; // no work needed this round
double start_time_ms = os::elapsedTime() * 1000.0;
_g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
ResourceMark rm;
HandleMark hm;
G1ParScanThreadState pss(_g1h, i);
G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss);
G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss);
G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss);
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);
G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss);
G1ParScanHeapRSClosure only_scan_heap_rs_cl(_g1h, &pss);
G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss);
G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss);
G1ParScanAndMarkHeapRSClosure scan_mark_heap_rs_cl(_g1h, &pss);
OopsInHeapRegionClosure *scan_root_cl;
OopsInHeapRegionClosure *scan_perm_cl;
if (_g1h->g1_policy()->during_initial_mark_pause()) {
scan_root_cl = &scan_mark_root_cl;
scan_perm_cl = &scan_mark_perm_cl;
} else {
scan_root_cl = &only_scan_root_cl;
scan_perm_cl = &only_scan_perm_cl;
}
pss.start_strong_roots();
_g1h->g1_process_strong_roots(/* not collecting perm */ false,
SharedHeap::SO_AllClasses,
scan_root_cl,
&push_heap_rs_cl,
scan_perm_cl,
i);
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()->record_obj_copy_time(i, elapsed_ms-term_ms);
_g1h->g1_policy()->record_termination(i, 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);
// Clean up any par-expanded rem sets.
HeapRegionRemSet::par_cleanup();
if (ParallelGCVerbose) {
MutexLocker x(stats_lock());
pss.print_termination_stats(i);
}
assert(pss.refs()->is_empty(), "should be empty");
double end_time_ms = os::elapsedTime() * 1000.0;
_g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
}
};
// *** Common G1 Evacuation Stuff
// This method is run in a GC worker.
void
G1CollectedHeap::
g1_process_strong_roots(bool collecting_perm_gen,
SharedHeap::ScanningOption so,
OopClosure* scan_non_heap_roots,
OopsInHeapRegionClosure* scan_rs,
OopsInGenClosure* scan_perm,
int worker_i) {
// First scan the strong roots, including the perm gen.
double ext_roots_start = os::elapsedTime();
double closure_app_time_sec = 0.0;
BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
BufferingOopsInGenClosure buf_scan_perm(scan_perm);
buf_scan_perm.set_generation(perm_gen());
// Walk the code cache w/o buffering, because StarTask cannot handle
// unaligned oop locations.
CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
process_strong_roots(false, // no scoping; this is parallel code
collecting_perm_gen, so,
&buf_scan_non_heap_roots,
&eager_scan_code_roots,
&buf_scan_perm);
// Now the ref_processor roots.
if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
// We need to treat the discovered reference lists 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()->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();
buf_scan_perm.done();
double ext_roots_end = os::elapsedTime();
g1_policy()->reset_obj_copy_time(worker_i);
double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
buf_scan_non_heap_roots.closure_app_seconds();
g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
double ext_root_time_ms =
((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
// Scan strong roots in mark stack.
if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
concurrent_mark()->oops_do(scan_non_heap_roots);
}
double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
// Now scan the complement of the collection set.
if (scan_rs != NULL) {
g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
}
_process_strong_tasks->all_tasks_completed();
}
void
G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
OopClosure* non_root_closure) {
CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
}
void G1CollectedHeap::evacuate_collection_set() {
set_evacuation_failed(false);
g1_rem_set()->prepare_for_oops_into_collection_set_do();
concurrent_g1_refine()->set_use_cache(false);
concurrent_g1_refine()->clear_hot_cache_claimed_index();
int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1);
set_par_threads(n_workers);
G1ParTask g1_par_task(this, n_workers, _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 = os::elapsedTime();
if (G1CollectedHeap::use_parallel_gc_threads()) {
// The individual threads will set their evac-failure closures.
StrongRootsScope srs(this);
if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
workers()->run_task(&g1_par_task);
} else {
StrongRootsScope srs(this);
g1_par_task.work(0);
}
double par_time = (os::elapsedTime() - start_par) * 1000.0;
g1_policy()->record_par_time(par_time);
set_par_threads(0);
// Weak root processing.
// Note: when JSR 292 is enabled and code blobs can contain
// non-perm oops then we will need to process the code blobs
// here too.
{
G1IsAliveClosure is_alive(this);
G1KeepAliveClosure keep_alive(this);
JNIHandles::weak_oops_do(&is_alive, &keep_alive);
}
release_gc_alloc_regions();
g1_rem_set()->cleanup_after_oops_into_collection_set_do();
concurrent_g1_refine()->clear_hot_cache();
concurrent_g1_refine()->set_use_cache(true);
finalize_for_evac_failure();
// Must do this before removing self-forwarding pointers, which clears
// the per-region evac-failure flags.
concurrent_mark()->complete_marking_in_collection_set();
if (evacuation_failed()) {
remove_self_forwarding_pointers();
if (PrintGCDetails) {
gclog_or_tty->print(" (to-space overflow)");
} else if (PrintGC) {
gclog_or_tty->print("--");
}
}
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,
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 {
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");
*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);
hr->set_notHumongous();
free_region(hr, &hr_pre_used, free_list, par);
size_t i = hr->hrs_index() + 1;
size_t num = 1;
while (i < n_regions()) {
HeapRegion* curr_hr = region_at(i);
if (!curr_hr->continuesHumongous()) {
break;
}
curr_hr->set_notHumongous();
free_region(curr_hr, &hr_pre_used, free_list, par);
num += 1;
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,
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 (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(int i) {
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());
verify_dirty_young_list(_young_list->first_survivor_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 (ParallelGCThreads > 0) {
set_par_threads(workers()->total_workers());
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);
}
}
double elapsed = os::elapsedTime() - start;
g1_policy()->record_clear_ct_time( elapsed * 1000.0);
#ifndef PRODUCT
if (G1VerifyCTCleanup || VerifyAfterGC) {
G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
heap_region_iterate(&cleanup_verifier);
}
#endif
}
void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
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 {
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();
guarantee( index != -1, "invariant" );
guarantee( (size_t)index < policy->young_cset_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();
guarantee( 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()) {
// And the region is empty.
assert(!cur->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);
}
cur = next;
}
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 /* humongous_proxy_set */,
false /* par */);
policy->record_young_free_cset_time_ms(young_time_ms);
policy->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);
g1_policy()->set_region_short_lived(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;
}
void G1CollectedHeap::empty_young_list() {
assert(heap_lock_held_for_gc(),
"the heap lock should already be held by or for this thread");
_young_list->empty_list();
}
// Done at the start of full GC.
void G1CollectedHeap::tear_down_region_lists() {
_free_list.remove_all();
}
class RegionResetter: public HeapRegionClosure {
G1CollectedHeap* _g1h;
FreeRegionList _local_free_list;
public:
RegionResetter() : _g1h(G1CollectedHeap::heap()),
_local_free_list("Local Free List for RegionResetter") { }
bool doHeapRegion(HeapRegion* r) {
if (r->continuesHumongous()) return false;
if (r->top() > r->bottom()) {
if (r->top() < r->end()) {
Copy::fill_to_words(r->top(),
pointer_delta(r->end(), r->top()));
}
} else {
assert(r->is_empty(), "tautology");
_local_free_list.add_as_tail(r);
}
return false;
}
void update_free_lists() {
_g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL,
false /* par */);
}
};
// Done at the end of full GC.
void G1CollectedHeap::rebuild_region_lists() {
// This needs to go at the end of the full GC.
RegionResetter rs;
heap_region_iterate(&rs);
rs.update_free_lists();
}
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 is_in_permanent(p);
} 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) {
g1_policy()->update_region_num(true /* next_is_young */);
set_region_short_lived_locked(new_alloc_region);
_hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
g1mm()->update_eden_counters();
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);
}
HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
bool force) {
return _g1h->new_mutator_alloc_region(word_size, force);
}
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,
size_t 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);
}
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) {
alloc_region->note_end_of_copying();
g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
if (ap == GCAllocForSurvived) {
young_list()->add_survivor_region(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:
HumongousRegionSet* _humongous_set;
FreeRegionList* _free_list;
size_t _region_count;
public:
VerifyRegionListsClosure(HumongousRegionSet* humongous_set,
FreeRegionList* free_list) :
_humongous_set(humongous_set), _free_list(free_list),
_region_count(0) { }
size_t 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);
}
return false;
}
};
HeapRegion* G1CollectedHeap::new_heap_region(size_t 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, true /* is_zeroed */);
}
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();
}
_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.
_humongous_set.verify_start();
_free_list.verify_start();
VerifyRegionListsClosure cl(&_humongous_set, &_free_list);
heap_region_iterate(&cl);
_humongous_set.verify_end();
_free_list.verify_end();
}