7000559: G1: assertion failure !outer || (full_collections_started == _full_collections_completed + 1)
Summary: The concurrent marking thread can complete its operation and increment the full GC counter during a Full GC. This causes the nesting of increments to the start and end of Full GCs that we are expecting to be wrong. the fix is for the marking thread to join the suspendible thread set before incrementing the counter so that it's blocked until the Full GC (or any other safepoint) is finished. The change also includes some minor code cleanup (I renamed a parameter).
Reviewed-by: brutisso, ysr
/*
* Copyright (c) 2001, 2010, 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.
*
*/
#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
#include "gc_implementation/g1/concurrentMark.hpp"
#include "gc_implementation/g1/g1RemSet.hpp"
#include "gc_implementation/g1/heapRegion.hpp"
#include "gc_implementation/parNew/parGCAllocBuffer.hpp"
#include "memory/barrierSet.hpp"
#include "memory/memRegion.hpp"
#include "memory/sharedHeap.hpp"
// A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
// It uses the "Garbage First" heap organization and algorithm, which
// may combine concurrent marking with parallel, incremental compaction of
// heap subsets that will yield large amounts of garbage.
class HeapRegion;
class HeapRegionSeq;
class PermanentGenerationSpec;
class GenerationSpec;
class OopsInHeapRegionClosure;
class G1ScanHeapEvacClosure;
class ObjectClosure;
class SpaceClosure;
class CompactibleSpaceClosure;
class Space;
class G1CollectorPolicy;
class GenRemSet;
class G1RemSet;
class HeapRegionRemSetIterator;
class ConcurrentMark;
class ConcurrentMarkThread;
class ConcurrentG1Refine;
class ConcurrentZFThread;
typedef OverflowTaskQueue<StarTask> RefToScanQueue;
typedef GenericTaskQueueSet<RefToScanQueue> RefToScanQueueSet;
typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
enum G1GCThreadGroups {
G1CRGroup = 0,
G1ZFGroup = 1,
G1CMGroup = 2,
G1CLGroup = 3
};
enum GCAllocPurpose {
GCAllocForTenured,
GCAllocForSurvived,
GCAllocPurposeCount
};
class YoungList : public CHeapObj {
private:
G1CollectedHeap* _g1h;
HeapRegion* _head;
HeapRegion* _survivor_head;
HeapRegion* _survivor_tail;
HeapRegion* _curr;
size_t _length;
size_t _survivor_length;
size_t _last_sampled_rs_lengths;
size_t _sampled_rs_lengths;
void empty_list(HeapRegion* list);
public:
YoungList(G1CollectedHeap* g1h);
void push_region(HeapRegion* hr);
void add_survivor_region(HeapRegion* hr);
void empty_list();
bool is_empty() { return _length == 0; }
size_t length() { return _length; }
size_t survivor_length() { return _survivor_length; }
void rs_length_sampling_init();
bool rs_length_sampling_more();
void rs_length_sampling_next();
void reset_sampled_info() {
_last_sampled_rs_lengths = 0;
}
size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
// for development purposes
void reset_auxilary_lists();
void clear() { _head = NULL; _length = 0; }
void clear_survivors() {
_survivor_head = NULL;
_survivor_tail = NULL;
_survivor_length = 0;
}
HeapRegion* first_region() { return _head; }
HeapRegion* first_survivor_region() { return _survivor_head; }
HeapRegion* last_survivor_region() { return _survivor_tail; }
// debugging
bool check_list_well_formed();
bool check_list_empty(bool check_sample = true);
void print();
};
class RefineCardTableEntryClosure;
class G1CollectedHeap : public SharedHeap {
friend class VM_G1CollectForAllocation;
friend class VM_GenCollectForPermanentAllocation;
friend class VM_G1CollectFull;
friend class VM_G1IncCollectionPause;
friend class VMStructs;
// Closures used in implementation.
friend class G1ParCopyHelper;
friend class G1IsAliveClosure;
friend class G1EvacuateFollowersClosure;
friend class G1ParScanThreadState;
friend class G1ParScanClosureSuper;
friend class G1ParEvacuateFollowersClosure;
friend class G1ParTask;
friend class G1FreeGarbageRegionClosure;
friend class RefineCardTableEntryClosure;
friend class G1PrepareCompactClosure;
friend class RegionSorter;
friend class CountRCClosure;
friend class EvacPopObjClosure;
friend class G1ParCleanupCTTask;
// Other related classes.
friend class G1MarkSweep;
private:
// The one and only G1CollectedHeap, so static functions can find it.
static G1CollectedHeap* _g1h;
static size_t _humongous_object_threshold_in_words;
// Storage for the G1 heap (excludes the permanent generation).
VirtualSpace _g1_storage;
MemRegion _g1_reserved;
// The part of _g1_storage that is currently committed.
MemRegion _g1_committed;
// The maximum part of _g1_storage that has ever been committed.
MemRegion _g1_max_committed;
// The number of regions that are completely free.
size_t _free_regions;
// The number of regions we could create by expansion.
size_t _expansion_regions;
// Return the number of free regions in the heap (by direct counting.)
size_t count_free_regions();
// Return the number of free regions on the free and unclean lists.
size_t count_free_regions_list();
// The block offset table for the G1 heap.
G1BlockOffsetSharedArray* _bot_shared;
// Move all of the regions off the free lists, then rebuild those free
// lists, before and after full GC.
void tear_down_region_lists();
void rebuild_region_lists();
// This sets all non-empty regions to need zero-fill (which they will if
// they are empty after full collection.)
void set_used_regions_to_need_zero_fill();
// The sequence of all heap regions in the heap.
HeapRegionSeq* _hrs;
// The region from which normal-sized objects are currently being
// allocated. May be NULL.
HeapRegion* _cur_alloc_region;
// Postcondition: cur_alloc_region == NULL.
void abandon_cur_alloc_region();
void abandon_gc_alloc_regions();
// The to-space memory regions into which objects are being copied during
// a GC.
HeapRegion* _gc_alloc_regions[GCAllocPurposeCount];
size_t _gc_alloc_region_counts[GCAllocPurposeCount];
// These are the regions, one per GCAllocPurpose, that are half-full
// at the end of a collection and that we want to reuse during the
// next collection.
HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount];
// This specifies whether we will keep the last half-full region at
// the end of a collection so that it can be reused during the next
// collection (this is specified per GCAllocPurpose)
bool _retain_gc_alloc_region[GCAllocPurposeCount];
// A list of the regions that have been set to be alloc regions in the
// current collection.
HeapRegion* _gc_alloc_region_list;
// Determines PLAB size for a particular allocation purpose.
static size_t desired_plab_sz(GCAllocPurpose purpose);
// When called by par thread, require par_alloc_during_gc_lock() to be held.
void push_gc_alloc_region(HeapRegion* hr);
// This should only be called single-threaded. Undeclares all GC alloc
// regions.
void forget_alloc_region_list();
// Should be used to set an alloc region, because there's other
// associated bookkeeping.
void set_gc_alloc_region(int purpose, HeapRegion* r);
// Check well-formedness of alloc region list.
bool check_gc_alloc_regions();
// Outside of GC pauses, the number of bytes used in all regions other
// than the current allocation region.
size_t _summary_bytes_used;
// This is used for a quick test on whether a reference points into
// the collection set or not. Basically, we have an array, with one
// byte per region, and that byte denotes whether the corresponding
// region is in the collection set or not. The entry corresponding
// the bottom of the heap, i.e., region 0, is pointed to by
// _in_cset_fast_test_base. The _in_cset_fast_test field has been
// biased so that it actually points to address 0 of the address
// space, to make the test as fast as possible (we can simply shift
// the address to address into it, instead of having to subtract the
// bottom of the heap from the address before shifting it; basically
// it works in the same way the card table works).
bool* _in_cset_fast_test;
// The allocated array used for the fast test on whether a reference
// points into the collection set or not. This field is also used to
// free the array.
bool* _in_cset_fast_test_base;
// The length of the _in_cset_fast_test_base array.
size_t _in_cset_fast_test_length;
volatile unsigned _gc_time_stamp;
size_t* _surviving_young_words;
void setup_surviving_young_words();
void update_surviving_young_words(size_t* surv_young_words);
void cleanup_surviving_young_words();
// It decides whether an explicit GC should start a concurrent cycle
// instead of doing a STW GC. Currently, a concurrent cycle is
// explicitly started if:
// (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
// (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
bool should_do_concurrent_full_gc(GCCause::Cause cause);
// Keeps track of how many "full collections" (i.e., Full GCs or
// concurrent cycles) we have completed. The number of them we have
// started is maintained in _total_full_collections in CollectedHeap.
volatile unsigned int _full_collections_completed;
// These are macros so that, if the assert fires, we get the correct
// line number, file, etc.
#define heap_locking_asserts_err_msg(__extra_message) \
err_msg("%s : Heap_lock %slocked, %sat a safepoint", \
(__extra_message), \
(!Heap_lock->owned_by_self()) ? "NOT " : "", \
(!SafepointSynchronize::is_at_safepoint()) ? "NOT " : "")
#define assert_heap_locked() \
do { \
assert(Heap_lock->owned_by_self(), \
heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
} while (0)
#define assert_heap_locked_or_at_safepoint() \
do { \
assert(Heap_lock->owned_by_self() || \
SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
"should be at a safepoint")); \
} while (0)
#define assert_heap_locked_and_not_at_safepoint() \
do { \
assert(Heap_lock->owned_by_self() && \
!SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
"should not be at a safepoint")); \
} while (0)
#define assert_heap_not_locked() \
do { \
assert(!Heap_lock->owned_by_self(), \
heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
} while (0)
#define assert_heap_not_locked_and_not_at_safepoint() \
do { \
assert(!Heap_lock->owned_by_self() && \
!SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
"should not be at a safepoint")); \
} while (0)
#define assert_at_safepoint() \
do { \
assert(SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should be at a safepoint")); \
} while (0)
#define assert_not_at_safepoint() \
do { \
assert(!SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should not be at a safepoint")); \
} while (0)
protected:
// Returns "true" iff none of the gc alloc regions have any allocations
// since the last call to "save_marks".
bool all_alloc_regions_no_allocs_since_save_marks();
// Perform finalization stuff on all allocation regions.
void retire_all_alloc_regions();
// The number of regions allocated to hold humongous objects.
int _num_humongous_regions;
YoungList* _young_list;
// The current policy object for the collector.
G1CollectorPolicy* _g1_policy;
// Parallel allocation lock to protect the current allocation region.
Mutex _par_alloc_during_gc_lock;
Mutex* par_alloc_during_gc_lock() { return &_par_alloc_during_gc_lock; }
// If possible/desirable, allocate a new HeapRegion for normal object
// allocation sufficient for an allocation of the given "word_size".
// If "do_expand" is true, will attempt to expand the heap if necessary
// to to satisfy the request. If "zero_filled" is true, requires a
// zero-filled region.
// (Returning NULL will trigger a GC.)
virtual HeapRegion* newAllocRegion_work(size_t word_size,
bool do_expand,
bool zero_filled);
virtual HeapRegion* newAllocRegion(size_t word_size,
bool zero_filled = true) {
return newAllocRegion_work(word_size, false, zero_filled);
}
virtual HeapRegion* newAllocRegionWithExpansion(int purpose,
size_t word_size,
bool zero_filled = true);
// Attempt to allocate an object of the given (very large) "word_size".
// Returns "NULL" on failure.
virtual HeapWord* humongous_obj_allocate(size_t word_size);
// The following two methods, allocate_new_tlab() and
// mem_allocate(), are the two main entry points from the runtime
// into the G1's allocation routines. They have the following
// assumptions:
//
// * They should both be called outside safepoints.
//
// * They should both be called without holding the Heap_lock.
//
// * All allocation requests for new TLABs should go to
// allocate_new_tlab().
//
// * All non-TLAB allocation requests should go to mem_allocate()
// and mem_allocate() should never be called with is_tlab == true.
//
// * If the GC locker is active we currently stall until we can
// allocate a new young region. This will be changed in the
// near future (see CR 6994056).
//
// * If either call cannot satisfy the allocation request using the
// current allocating region, they will try to get a new one. If
// this fails, they will attempt to do an evacuation pause and
// retry the allocation.
//
// * If all allocation attempts fail, even after trying to schedule
// an evacuation pause, allocate_new_tlab() will return NULL,
// whereas mem_allocate() will attempt a heap expansion and/or
// schedule a Full GC.
//
// * We do not allow humongous-sized TLABs. So, allocate_new_tlab
// should never be called with word_size being humongous. All
// humongous allocation requests should go to mem_allocate() which
// will satisfy them with a special path.
virtual HeapWord* allocate_new_tlab(size_t word_size);
virtual HeapWord* mem_allocate(size_t word_size,
bool is_noref,
bool is_tlab, /* expected to be false */
bool* gc_overhead_limit_was_exceeded);
// The following methods, allocate_from_cur_allocation_region(),
// attempt_allocation(), replace_cur_alloc_region_and_allocate(),
// attempt_allocation_slow(), and attempt_allocation_humongous()
// have very awkward pre- and post-conditions with respect to
// locking:
//
// If they are called outside a safepoint they assume the caller
// holds the Heap_lock when it calls them. However, on exit they
// will release the Heap_lock if they return a non-NULL result, but
// keep holding the Heap_lock if they return a NULL result. The
// reason for this is that we need to dirty the cards that span
// allocated blocks on young regions to avoid having to take the
// slow path of the write barrier (for performance reasons we don't
// update RSets for references whose source is a young region, so we
// don't need to look at dirty cards on young regions). But, doing
// this card dirtying while holding the Heap_lock can be a
// scalability bottleneck, especially given that some allocation
// requests might be of non-trivial size (and the larger the region
// size is, the fewer allocations requests will be considered
// humongous, as the humongous size limit is a fraction of the
// region size). So, when one of these calls succeeds in allocating
// a block it does the card dirtying after it releases the Heap_lock
// which is why it will return without holding it.
//
// The above assymetry is the reason why locking / unlocking is done
// explicitly (i.e., with Heap_lock->lock() and
// Heap_lock->unlocked()) instead of using MutexLocker and
// MutexUnlocker objects. The latter would ensure that the lock is
// unlocked / re-locked at every possible exit out of the basic
// block. However, we only want that action to happen in selected
// places.
//
// Further, if the above methods are called during a safepoint, then
// naturally there's no assumption about the Heap_lock being held or
// there's no attempt to unlock it. The parameter at_safepoint
// indicates whether the call is made during a safepoint or not (as
// an optimization, to avoid reading the global flag with
// SafepointSynchronize::is_at_safepoint()).
//
// The methods share these parameters:
//
// * word_size : the size of the allocation request in words
// * at_safepoint : whether the call is done at a safepoint; this
// also determines whether a GC is permitted
// (at_safepoint == false) or not (at_safepoint == true)
// * do_dirtying : whether the method should dirty the allocated
// block before returning
//
// They all return either the address of the block, if they
// successfully manage to allocate it, or NULL.
// It tries to satisfy an allocation request out of the current
// allocating region, which is passed as a parameter. It assumes
// that the caller has checked that the current allocating region is
// not NULL. Given that the caller has to check the current
// allocating region for at least NULL, it might as well pass it as
// the first parameter so that the method doesn't have to read it
// from the _cur_alloc_region field again.
inline HeapWord* allocate_from_cur_alloc_region(HeapRegion* cur_alloc_region,
size_t word_size);
// It attempts to allocate out of the current alloc region. If that
// fails, it retires the current alloc region (if there is one),
// tries to get a new one and retries the allocation.
inline HeapWord* attempt_allocation(size_t word_size);
// It assumes that the current alloc region has been retired and
// tries to allocate a new one. If it's successful, it performs the
// allocation out of the new current alloc region and updates
// _cur_alloc_region. Normally, it would try to allocate a new
// region if the young gen is not full, unless can_expand is true in
// which case it would always try to allocate a new region.
HeapWord* replace_cur_alloc_region_and_allocate(size_t word_size,
bool at_safepoint,
bool do_dirtying,
bool can_expand);
// The slow path when we are unable to allocate a new current alloc
// region to satisfy an allocation request (i.e., when
// attempt_allocation() fails). It will try to do an evacuation
// pause, which might stall due to the GC locker, and retry the
// allocation attempt when appropriate.
HeapWord* attempt_allocation_slow(size_t word_size);
// The method that tries to satisfy a humongous allocation
// request. If it cannot satisfy it it will try to do an evacuation
// pause to perhaps reclaim enough space to be able to satisfy the
// allocation request afterwards.
HeapWord* attempt_allocation_humongous(size_t word_size,
bool at_safepoint);
// It does the common work when we are retiring the current alloc region.
inline void retire_cur_alloc_region_common(HeapRegion* cur_alloc_region);
// It retires the current alloc region, which is passed as a
// parameter (since, typically, the caller is already holding on to
// it). It sets _cur_alloc_region to NULL.
void retire_cur_alloc_region(HeapRegion* cur_alloc_region);
// It attempts to do an allocation immediately before or after an
// evacuation pause and can only be called by the VM thread. It has
// slightly different assumptions that the ones before (i.e.,
// assumes that the current alloc region has been retired).
HeapWord* attempt_allocation_at_safepoint(size_t word_size,
bool expect_null_cur_alloc_region);
// It dirties the cards that cover the block so that so that the post
// write barrier never queues anything when updating objects on this
// block. It is assumed (and in fact we assert) that the block
// belongs to a young region.
inline void dirty_young_block(HeapWord* start, size_t word_size);
// Allocate blocks during garbage collection. Will ensure an
// allocation region, either by picking one or expanding the
// heap, and then allocate a block of the given size. The block
// may not be a humongous - it must fit into a single heap region.
HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
HeapRegion* alloc_region,
bool par,
size_t word_size);
// Ensure that no further allocations can happen in "r", bearing in mind
// that parallel threads might be attempting allocations.
void par_allocate_remaining_space(HeapRegion* r);
// Retires an allocation region when it is full or at the end of a
// GC pause.
void retire_alloc_region(HeapRegion* alloc_region, bool par);
// - if explicit_gc is true, the GC is for a System.gc() or a heap
// inspection request and should collect the entire heap
// - if clear_all_soft_refs is true, all soft references should be
// cleared during the GC
// - if explicit_gc is false, word_size describes the allocation that
// the GC should attempt (at least) to satisfy
// - it returns false if it is unable to do the collection due to the
// GC locker being active, true otherwise
bool do_collection(bool explicit_gc,
bool clear_all_soft_refs,
size_t word_size);
// Callback from VM_G1CollectFull operation.
// Perform a full collection.
void do_full_collection(bool clear_all_soft_refs);
// Resize the heap if necessary after a full collection. If this is
// after a collect-for allocation, "word_size" is the allocation size,
// and will be considered part of the used portion of the heap.
void resize_if_necessary_after_full_collection(size_t word_size);
// Callback from VM_G1CollectForAllocation operation.
// This function does everything necessary/possible to satisfy a
// failed allocation request (including collection, expansion, etc.)
HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
// 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* expand_and_allocate(size_t word_size);
public:
// Expand the garbage-first heap by at least the given size (in bytes!).
// (Rounds up to a HeapRegion boundary.)
virtual void expand(size_t expand_bytes);
// Do anything common to GC's.
virtual void gc_prologue(bool full);
virtual void gc_epilogue(bool full);
// We register a region with the fast "in collection set" test. We
// simply set to true the array slot corresponding to this region.
void register_region_with_in_cset_fast_test(HeapRegion* r) {
assert(_in_cset_fast_test_base != NULL, "sanity");
assert(r->in_collection_set(), "invariant");
int index = r->hrs_index();
assert(0 <= index && (size_t) index < _in_cset_fast_test_length, "invariant");
assert(!_in_cset_fast_test_base[index], "invariant");
_in_cset_fast_test_base[index] = true;
}
// This is a fast test on whether a reference points into the
// collection set or not. It does not assume that the reference
// points into the heap; if it doesn't, it will return false.
bool in_cset_fast_test(oop obj) {
assert(_in_cset_fast_test != NULL, "sanity");
if (_g1_committed.contains((HeapWord*) obj)) {
// no need to subtract the bottom of the heap from obj,
// _in_cset_fast_test is biased
size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes;
bool ret = _in_cset_fast_test[index];
// let's make sure the result is consistent with what the slower
// test returns
assert( ret || !obj_in_cs(obj), "sanity");
assert(!ret || obj_in_cs(obj), "sanity");
return ret;
} else {
return false;
}
}
void clear_cset_fast_test() {
assert(_in_cset_fast_test_base != NULL, "sanity");
memset(_in_cset_fast_test_base, false,
_in_cset_fast_test_length * sizeof(bool));
}
// This is called at the end of either a concurrent cycle or a Full
// GC to update the number of full collections completed. Those two
// can happen in a nested fashion, i.e., we start a concurrent
// cycle, a Full GC happens half-way through it which ends first,
// and then the cycle notices that a Full GC happened and ends
// too. The concurrent parameter is a boolean to help us do a bit
// tighter consistency checking in the method. If concurrent is
// false, the caller is the inner caller in the nesting (i.e., the
// Full GC). If concurrent is true, the caller is the outer caller
// in this nesting (i.e., the concurrent cycle). Further nesting is
// not currently supported. The end of the this call also notifies
// the FullGCCount_lock in case a Java thread is waiting for a full
// GC to happen (e.g., it called System.gc() with
// +ExplicitGCInvokesConcurrent).
void increment_full_collections_completed(bool concurrent);
unsigned int full_collections_completed() {
return _full_collections_completed;
}
protected:
// Shrink the garbage-first heap by at most the given size (in bytes!).
// (Rounds down to a HeapRegion boundary.)
virtual void shrink(size_t expand_bytes);
void shrink_helper(size_t expand_bytes);
#if TASKQUEUE_STATS
static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
void reset_taskqueue_stats();
#endif // TASKQUEUE_STATS
// Schedule the VM operation that will do an evacuation pause to
// satisfy an allocation request of word_size. *succeeded will
// return whether the VM operation was successful (it did do an
// evacuation pause) or not (another thread beat us to it or the GC
// locker was active). Given that we should not be holding the
// Heap_lock when we enter this method, we will pass the
// gc_count_before (i.e., total_collections()) as a parameter since
// it has to be read while holding the Heap_lock. Currently, both
// methods that call do_collection_pause() release the Heap_lock
// before the call, so it's easy to read gc_count_before just before.
HeapWord* do_collection_pause(size_t word_size,
unsigned int gc_count_before,
bool* succeeded);
// The guts of the incremental collection pause, executed by the vm
// thread. It returns false if it is unable to do the collection due
// to the GC locker being active, true otherwise
bool do_collection_pause_at_safepoint(double target_pause_time_ms);
// Actually do the work of evacuating the collection set.
void evacuate_collection_set();
// The g1 remembered set of the heap.
G1RemSet* _g1_rem_set;
// And it's mod ref barrier set, used to track updates for the above.
ModRefBarrierSet* _mr_bs;
// A set of cards that cover the objects for which the Rsets should be updated
// concurrently after the collection.
DirtyCardQueueSet _dirty_card_queue_set;
// The Heap Region Rem Set Iterator.
HeapRegionRemSetIterator** _rem_set_iterator;
// The closure used to refine a single card.
RefineCardTableEntryClosure* _refine_cte_cl;
// A function to check the consistency of dirty card logs.
void check_ct_logs_at_safepoint();
// A DirtyCardQueueSet that is used to hold cards that contain
// references into the current collection set. This is used to
// update the remembered sets of the regions in the collection
// set in the event of an evacuation failure.
DirtyCardQueueSet _into_cset_dirty_card_queue_set;
// After a collection pause, make the regions in the CS into free
// regions.
void free_collection_set(HeapRegion* cs_head);
// Abandon the current collection set without recording policy
// statistics or updating free lists.
void abandon_collection_set(HeapRegion* cs_head);
// Applies "scan_non_heap_roots" to roots outside the heap,
// "scan_rs" to roots inside the heap (having done "set_region" to
// indicate the region in which the root resides), and does "scan_perm"
// (setting the generation to the perm generation.) If "scan_rs" is
// NULL, then this step is skipped. The "worker_i"
// param is for use with parallel roots processing, and should be
// the "i" of the calling parallel worker thread's work(i) function.
// In the sequential case this param will be ignored.
void 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);
// Apply "blk" to all the weak roots of the system. These include
// JNI weak roots, the code cache, system dictionary, symbol table,
// string table, and referents of reachable weak refs.
void g1_process_weak_roots(OopClosure* root_closure,
OopClosure* non_root_closure);
// Invoke "save_marks" on all heap regions.
void save_marks();
// Free a heap region.
void free_region(HeapRegion* hr);
// A component of "free_region", exposed for 'batching'.
// All the params after "hr" are out params: the used bytes of the freed
// region(s), the number of H regions cleared, the number of regions
// freed, and pointers to the head and tail of a list of freed contig
// regions, linked throught the "next_on_unclean_list" field.
void free_region_work(HeapRegion* hr,
size_t& pre_used,
size_t& cleared_h,
size_t& freed_regions,
UncleanRegionList* list,
bool par = false);
// The concurrent marker (and the thread it runs in.)
ConcurrentMark* _cm;
ConcurrentMarkThread* _cmThread;
bool _mark_in_progress;
// The concurrent refiner.
ConcurrentG1Refine* _cg1r;
// The concurrent zero-fill thread.
ConcurrentZFThread* _czft;
// The parallel task queues
RefToScanQueueSet *_task_queues;
// True iff a evacuation has failed in the current collection.
bool _evacuation_failed;
// Set the attribute indicating whether evacuation has failed in the
// current collection.
void set_evacuation_failed(bool b) { _evacuation_failed = b; }
// Failed evacuations cause some logical from-space objects to have
// forwarding pointers to themselves. Reset them.
void remove_self_forwarding_pointers();
// When one is non-null, so is the other. Together, they each pair is
// an object with a preserved mark, and its mark value.
GrowableArray<oop>* _objs_with_preserved_marks;
GrowableArray<markOop>* _preserved_marks_of_objs;
// Preserve the mark of "obj", if necessary, in preparation for its mark
// word being overwritten with a self-forwarding-pointer.
void preserve_mark_if_necessary(oop obj, markOop m);
// The stack of evac-failure objects left to be scanned.
GrowableArray<oop>* _evac_failure_scan_stack;
// The closure to apply to evac-failure objects.
OopsInHeapRegionClosure* _evac_failure_closure;
// Set the field above.
void
set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
_evac_failure_closure = evac_failure_closure;
}
// Push "obj" on the scan stack.
void push_on_evac_failure_scan_stack(oop obj);
// Process scan stack entries until the stack is empty.
void drain_evac_failure_scan_stack();
// True iff an invocation of "drain_scan_stack" is in progress; to
// prevent unnecessary recursion.
bool _drain_in_progress;
// Do any necessary initialization for evacuation-failure handling.
// "cl" is the closure that will be used to process evac-failure
// objects.
void init_for_evac_failure(OopsInHeapRegionClosure* cl);
// Do any necessary cleanup for evacuation-failure handling data
// structures.
void finalize_for_evac_failure();
// An attempt to evacuate "obj" has failed; take necessary steps.
void handle_evacuation_failure(oop obj);
oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
void handle_evacuation_failure_common(oop obj, markOop m);
// Ensure that the relevant gc_alloc regions are set.
void get_gc_alloc_regions();
// We're done with GC alloc regions. We are going to tear down the
// gc alloc list and remove the gc alloc tag from all the regions on
// that list. However, we will also retain the last (i.e., the one
// that is half-full) GC alloc region, per GCAllocPurpose, for
// possible reuse during the next collection, provided
// _retain_gc_alloc_region[] indicates that it should be the
// case. Said regions are kept in the _retained_gc_alloc_regions[]
// array. If the parameter totally is set, we will not retain any
// regions, irrespective of what _retain_gc_alloc_region[]
// indicates.
void release_gc_alloc_regions(bool totally);
#ifndef PRODUCT
// Useful for debugging.
void print_gc_alloc_regions();
#endif // !PRODUCT
// ("Weak") Reference processing support
ReferenceProcessor* _ref_processor;
enum G1H_process_strong_roots_tasks {
G1H_PS_mark_stack_oops_do,
G1H_PS_refProcessor_oops_do,
// Leave this one last.
G1H_PS_NumElements
};
SubTasksDone* _process_strong_tasks;
// List of regions which require zero filling.
UncleanRegionList _unclean_region_list;
bool _unclean_regions_coming;
public:
SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
void set_refine_cte_cl_concurrency(bool concurrent);
RefToScanQueue *task_queue(int i) const;
// A set of cards where updates happened during the GC
DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
// A DirtyCardQueueSet that is used to hold cards that contain
// references into the current collection set. This is used to
// update the remembered sets of the regions in the collection
// set in the event of an evacuation failure.
DirtyCardQueueSet& into_cset_dirty_card_queue_set()
{ return _into_cset_dirty_card_queue_set; }
// Create a G1CollectedHeap with the specified policy.
// Must call the initialize method afterwards.
// May not return if something goes wrong.
G1CollectedHeap(G1CollectorPolicy* policy);
// Initialize the G1CollectedHeap to have the initial and
// maximum sizes, permanent generation, and remembered and barrier sets
// specified by the policy object.
jint initialize();
void ref_processing_init();
void set_par_threads(int t) {
SharedHeap::set_par_threads(t);
_process_strong_tasks->set_n_threads(t);
}
virtual CollectedHeap::Name kind() const {
return CollectedHeap::G1CollectedHeap;
}
// The current policy object for the collector.
G1CollectorPolicy* g1_policy() const { return _g1_policy; }
// Adaptive size policy. No such thing for g1.
virtual AdaptiveSizePolicy* size_policy() { return NULL; }
// The rem set and barrier set.
G1RemSet* g1_rem_set() const { return _g1_rem_set; }
ModRefBarrierSet* mr_bs() const { return _mr_bs; }
// The rem set iterator.
HeapRegionRemSetIterator* rem_set_iterator(int i) {
return _rem_set_iterator[i];
}
HeapRegionRemSetIterator* rem_set_iterator() {
return _rem_set_iterator[0];
}
unsigned get_gc_time_stamp() {
return _gc_time_stamp;
}
void reset_gc_time_stamp() {
_gc_time_stamp = 0;
OrderAccess::fence();
}
void increment_gc_time_stamp() {
++_gc_time_stamp;
OrderAccess::fence();
}
void iterate_dirty_card_closure(CardTableEntryClosure* cl,
DirtyCardQueue* into_cset_dcq,
bool concurrent, int worker_i);
// The shared block offset table array.
G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
// Reference Processing accessor
ReferenceProcessor* ref_processor() { return _ref_processor; }
// Reserved (g1 only; super method includes perm), capacity and the used
// portion in bytes.
size_t g1_reserved_obj_bytes() const { return _g1_reserved.byte_size(); }
virtual size_t capacity() const;
virtual size_t used() const;
// This should be called when we're not holding the heap lock. The
// result might be a bit inaccurate.
size_t used_unlocked() const;
size_t recalculate_used() const;
#ifndef PRODUCT
size_t recalculate_used_regions() const;
#endif // PRODUCT
// These virtual functions do the actual allocation.
// Some heaps may offer a contiguous region for shared non-blocking
// allocation, via inlined code (by exporting the address of the top and
// end fields defining the extent of the contiguous allocation region.)
// But G1CollectedHeap doesn't yet support this.
// Return an estimate of the maximum allocation that could be performed
// without triggering any collection or expansion activity. In a
// generational collector, for example, this is probably the largest
// allocation that could be supported (without expansion) in the youngest
// generation. It is "unsafe" because no locks are taken; the result
// should be treated as an approximation, not a guarantee, for use in
// heuristic resizing decisions.
virtual size_t unsafe_max_alloc();
virtual bool is_maximal_no_gc() const {
return _g1_storage.uncommitted_size() == 0;
}
// The total number of regions in the heap.
size_t n_regions();
// The number of regions that are completely free.
size_t max_regions();
// The number of regions that are completely free.
size_t free_regions();
// The number of regions that are not completely free.
size_t used_regions() { return n_regions() - free_regions(); }
// True iff the ZF thread should run.
bool should_zf();
// The number of regions available for "regular" expansion.
size_t expansion_regions() { return _expansion_regions; }
#ifndef PRODUCT
bool regions_accounted_for();
bool print_region_accounting_info();
void print_region_counts();
#endif
HeapRegion* alloc_region_from_unclean_list(bool zero_filled);
HeapRegion* alloc_region_from_unclean_list_locked(bool zero_filled);
void put_region_on_unclean_list(HeapRegion* r);
void put_region_on_unclean_list_locked(HeapRegion* r);
void prepend_region_list_on_unclean_list(UncleanRegionList* list);
void prepend_region_list_on_unclean_list_locked(UncleanRegionList* list);
void set_unclean_regions_coming(bool b);
void set_unclean_regions_coming_locked(bool b);
// Wait for cleanup to be complete.
void wait_for_cleanup_complete();
// Like above, but assumes that the calling thread owns the Heap_lock.
void wait_for_cleanup_complete_locked();
// Return the head of the unclean list.
HeapRegion* peek_unclean_region_list_locked();
// Remove and return the head of the unclean list.
HeapRegion* pop_unclean_region_list_locked();
// List of regions which are zero filled and ready for allocation.
HeapRegion* _free_region_list;
// Number of elements on the free list.
size_t _free_region_list_size;
// If the head of the unclean list is ZeroFilled, move it to the free
// list.
bool move_cleaned_region_to_free_list_locked();
bool move_cleaned_region_to_free_list();
void put_free_region_on_list_locked(HeapRegion* r);
void put_free_region_on_list(HeapRegion* r);
// Remove and return the head element of the free list.
HeapRegion* pop_free_region_list_locked();
// If "zero_filled" is true, we first try the free list, then we try the
// unclean list, zero-filling the result. If "zero_filled" is false, we
// first try the unclean list, then the zero-filled list.
HeapRegion* alloc_free_region_from_lists(bool zero_filled);
// Verify the integrity of the region lists.
void remove_allocated_regions_from_lists();
bool verify_region_lists();
bool verify_region_lists_locked();
size_t unclean_region_list_length();
size_t free_region_list_length();
// Perform a collection of the heap; intended for use in implementing
// "System.gc". This probably implies as full a collection as the
// "CollectedHeap" supports.
virtual void collect(GCCause::Cause cause);
// The same as above but assume that the caller holds the Heap_lock.
void collect_locked(GCCause::Cause cause);
// This interface assumes that it's being called by the
// vm thread. It collects the heap assuming that the
// heap lock is already held and that we are executing in
// the context of the vm thread.
virtual void collect_as_vm_thread(GCCause::Cause cause);
// True iff a evacuation has failed in the most-recent collection.
bool evacuation_failed() { return _evacuation_failed; }
// Free a region if it is totally full of garbage. Returns the number of
// bytes freed (0 ==> didn't free it).
size_t free_region_if_totally_empty(HeapRegion *hr);
void free_region_if_totally_empty_work(HeapRegion *hr,
size_t& pre_used,
size_t& cleared_h_regions,
size_t& freed_regions,
UncleanRegionList* list,
bool par = false);
// If we've done free region work that yields the given changes, update
// the relevant global variables.
void finish_free_region_work(size_t pre_used,
size_t cleared_h_regions,
size_t freed_regions,
UncleanRegionList* list);
// Returns "TRUE" iff "p" points into the allocated area of the heap.
virtual bool is_in(const void* p) const;
// Return "TRUE" iff the given object address is within the collection
// set.
inline bool obj_in_cs(oop obj);
// Return "TRUE" iff the given object address is in the reserved
// region of g1 (excluding the permanent generation).
bool is_in_g1_reserved(const void* p) const {
return _g1_reserved.contains(p);
}
// Returns a MemRegion that corresponds to the space that has been
// committed in the heap
MemRegion g1_committed() {
return _g1_committed;
}
NOT_PRODUCT(bool is_in_closed_subset(const void* p) const;)
// Dirty card table entries covering a list of young regions.
void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list);
// This resets the card table to all zeros. It is used after
// a collection pause which used the card table to claim cards.
void cleanUpCardTable();
// Iteration functions.
// Iterate over all the ref-containing fields of all objects, calling
// "cl.do_oop" on each.
virtual void oop_iterate(OopClosure* cl) {
oop_iterate(cl, true);
}
void oop_iterate(OopClosure* cl, bool do_perm);
// Same as above, restricted to a memory region.
virtual void oop_iterate(MemRegion mr, OopClosure* cl) {
oop_iterate(mr, cl, true);
}
void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm);
// Iterate over all objects, calling "cl.do_object" on each.
virtual void object_iterate(ObjectClosure* cl) {
object_iterate(cl, true);
}
virtual void safe_object_iterate(ObjectClosure* cl) {
object_iterate(cl, true);
}
void object_iterate(ObjectClosure* cl, bool do_perm);
// Iterate over all objects allocated since the last collection, calling
// "cl.do_object" on each. The heap must have been initialized properly
// to support this function, or else this call will fail.
virtual void object_iterate_since_last_GC(ObjectClosure* cl);
// Iterate over all spaces in use in the heap, in ascending address order.
virtual void space_iterate(SpaceClosure* cl);
// Iterate over heap regions, in address order, terminating the
// iteration early if the "doHeapRegion" method returns "true".
void heap_region_iterate(HeapRegionClosure* blk);
// Iterate over heap regions starting with r (or the first region if "r"
// is NULL), in address order, terminating early if the "doHeapRegion"
// method returns "true".
void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
// As above but starting from the region at index idx.
void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
HeapRegion* region_at(size_t idx);
// Divide the heap region sequence into "chunks" of some size (the number
// of regions divided by the number of parallel threads times some
// overpartition factor, currently 4). Assumes that this will be called
// in parallel by ParallelGCThreads worker threads with discinct worker
// ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
// calls will use the same "claim_value", and that that claim value is
// different from the claim_value of any heap region before the start of
// the iteration. Applies "blk->doHeapRegion" to each of the regions, by
// attempting to claim the first region in each chunk, and, if
// successful, applying the closure to each region in the chunk (and
// setting the claim value of the second and subsequent regions of the
// chunk.) For now requires that "doHeapRegion" always returns "false",
// i.e., that a closure never attempt to abort a traversal.
void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
int worker,
jint claim_value);
// It resets all the region claim values to the default.
void reset_heap_region_claim_values();
#ifdef ASSERT
bool check_heap_region_claim_values(jint claim_value);
#endif // ASSERT
// Iterate over the regions (if any) in the current collection set.
void collection_set_iterate(HeapRegionClosure* blk);
// As above but starting from region r
void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
// Returns the first (lowest address) compactible space in the heap.
virtual CompactibleSpace* first_compactible_space();
// A CollectedHeap will contain some number of spaces. This finds the
// space containing a given address, or else returns NULL.
virtual Space* space_containing(const void* addr) const;
// A G1CollectedHeap will contain some number of heap regions. This
// finds the region containing a given address, or else returns NULL.
HeapRegion* heap_region_containing(const void* addr) const;
// Like the above, but requires "addr" to be in the heap (to avoid a
// null-check), and unlike the above, may return an continuing humongous
// region.
HeapRegion* heap_region_containing_raw(const void* addr) const;
// A CollectedHeap is divided into a dense sequence of "blocks"; that is,
// each address in the (reserved) heap is a member of exactly
// one block. The defining characteristic of a block is that it is
// possible to find its size, and thus to progress forward to the next
// block. (Blocks may be of different sizes.) Thus, blocks may
// represent Java objects, or they might be free blocks in a
// free-list-based heap (or subheap), as long as the two kinds are
// distinguishable and the size of each is determinable.
// Returns the address of the start of the "block" that contains the
// address "addr". We say "blocks" instead of "object" since some heaps
// may not pack objects densely; a chunk may either be an object or a
// non-object.
virtual HeapWord* block_start(const void* addr) const;
// Requires "addr" to be the start of a chunk, and returns its size.
// "addr + size" is required to be the start of a new chunk, or the end
// of the active area of the heap.
virtual size_t block_size(const HeapWord* addr) const;
// Requires "addr" to be the start of a block, and returns "TRUE" iff
// the block is an object.
virtual bool block_is_obj(const HeapWord* addr) const;
// Does this heap support heap inspection? (+PrintClassHistogram)
virtual bool supports_heap_inspection() const { return true; }
// Section on thread-local allocation buffers (TLABs)
// See CollectedHeap for semantics.
virtual bool supports_tlab_allocation() const;
virtual size_t tlab_capacity(Thread* thr) const;
virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
// Can a compiler initialize a new object without store barriers?
// This permission only extends from the creation of a new object
// via a TLAB up to the first subsequent safepoint. If such permission
// is granted for this heap type, the compiler promises to call
// defer_store_barrier() below on any slow path allocation of
// a new object for which such initializing store barriers will
// have been elided. G1, like CMS, allows this, but should be
// ready to provide a compensating write barrier as necessary
// if that storage came out of a non-young region. The efficiency
// of this implementation depends crucially on being able to
// answer very efficiently in constant time whether a piece of
// storage in the heap comes from a young region or not.
// See ReduceInitialCardMarks.
virtual bool can_elide_tlab_store_barriers() const {
// 6920090: Temporarily disabled, because of lingering
// instabilities related to RICM with G1. In the
// interim, the option ReduceInitialCardMarksForG1
// below is left solely as a debugging device at least
// until 6920109 fixes the instabilities.
return ReduceInitialCardMarksForG1;
}
virtual bool card_mark_must_follow_store() const {
return true;
}
bool is_in_young(oop obj) {
HeapRegion* hr = heap_region_containing(obj);
return hr != NULL && hr->is_young();
}
// We don't need barriers for initializing stores to objects
// in the young gen: for the SATB pre-barrier, there is no
// pre-value that needs to be remembered; for the remembered-set
// update logging post-barrier, we don't maintain remembered set
// information for young gen objects. Note that non-generational
// G1 does not have any "young" objects, should not elide
// the rs logging barrier and so should always answer false below.
// However, non-generational G1 (-XX:-G1Gen) appears to have
// bit-rotted so was not tested below.
virtual bool can_elide_initializing_store_barrier(oop new_obj) {
// Re 6920090, 6920109 above.
assert(ReduceInitialCardMarksForG1, "Else cannot be here");
assert(G1Gen || !is_in_young(new_obj),
"Non-generational G1 should never return true below");
return is_in_young(new_obj);
}
// Can a compiler elide a store barrier when it writes
// a permanent oop into the heap? Applies when the compiler
// is storing x to the heap, where x->is_perm() is true.
virtual bool can_elide_permanent_oop_store_barriers() const {
// At least until perm gen collection is also G1-ified, at
// which point this should return false.
return true;
}
virtual bool allocs_are_zero_filled();
// The boundary between a "large" and "small" array of primitives, in
// words.
virtual size_t large_typearray_limit();
// Returns "true" iff the given word_size is "very large".
static bool isHumongous(size_t word_size) {
// Note this has to be strictly greater-than as the TLABs
// are capped at the humongous thresold and we want to
// ensure that we don't try to allocate a TLAB as
// humongous and that we don't allocate a humongous
// object in a TLAB.
return word_size > _humongous_object_threshold_in_words;
}
// Update mod union table with the set of dirty cards.
void updateModUnion();
// Set the mod union bits corresponding to the given memRegion. Note
// that this is always a safe operation, since it doesn't clear any
// bits.
void markModUnionRange(MemRegion mr);
// Records the fact that a marking phase is no longer in progress.
void set_marking_complete() {
_mark_in_progress = false;
}
void set_marking_started() {
_mark_in_progress = true;
}
bool mark_in_progress() {
return _mark_in_progress;
}
// Print the maximum heap capacity.
virtual size_t max_capacity() const;
virtual jlong millis_since_last_gc();
// Perform any cleanup actions necessary before allowing a verification.
virtual void prepare_for_verify();
// Perform verification.
// use_prev_marking == true -> use "prev" marking information,
// use_prev_marking == false -> use "next" marking information
// NOTE: Only the "prev" marking information is guaranteed to be
// consistent most of the time, so most calls to this should use
// use_prev_marking == true. Currently, there is only one case where
// this is called with use_prev_marking == false, which is to verify
// the "next" marking information at the end of remark.
void verify(bool allow_dirty, bool silent, bool use_prev_marking);
// Override; it uses the "prev" marking information
virtual void verify(bool allow_dirty, bool silent);
// Default behavior by calling print(tty);
virtual void print() const;
// This calls print_on(st, PrintHeapAtGCExtended).
virtual void print_on(outputStream* st) const;
// If extended is true, it will print out information for all
// regions in the heap by calling print_on_extended(st).
virtual void print_on(outputStream* st, bool extended) const;
virtual void print_on_extended(outputStream* st) const;
virtual void print_gc_threads_on(outputStream* st) const;
virtual void gc_threads_do(ThreadClosure* tc) const;
// Override
void print_tracing_info() const;
// If "addr" is a pointer into the (reserved?) heap, returns a positive
// number indicating the "arena" within the heap in which "addr" falls.
// Or else returns 0.
virtual int addr_to_arena_id(void* addr) const;
// Convenience function to be used in situations where the heap type can be
// asserted to be this type.
static G1CollectedHeap* heap();
void empty_young_list();
void set_region_short_lived_locked(HeapRegion* hr);
// add appropriate methods for any other surv rate groups
YoungList* young_list() { return _young_list; }
// debugging
bool check_young_list_well_formed() {
return _young_list->check_list_well_formed();
}
bool check_young_list_empty(bool check_heap,
bool check_sample = true);
// *** Stuff related to concurrent marking. It's not clear to me that so
// many of these need to be public.
// The functions below are helper functions that a subclass of
// "CollectedHeap" can use in the implementation of its virtual
// functions.
// This performs a concurrent marking of the live objects in a
// bitmap off to the side.
void doConcurrentMark();
// This is called from the marksweep collector which then does
// a concurrent mark and verifies that the results agree with
// the stop the world marking.
void checkConcurrentMark();
void do_sync_mark();
bool isMarkedPrev(oop obj) const;
bool isMarkedNext(oop obj) const;
// use_prev_marking == true -> use "prev" marking information,
// use_prev_marking == false -> use "next" marking information
bool is_obj_dead_cond(const oop obj,
const HeapRegion* hr,
const bool use_prev_marking) const {
if (use_prev_marking) {
return is_obj_dead(obj, hr);
} else {
return is_obj_ill(obj, hr);
}
}
// Determine if an object is dead, given the object and also
// the region to which the object belongs. An object is dead
// iff a) it was not allocated since the last mark and b) it
// is not marked.
bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
return
!hr->obj_allocated_since_prev_marking(obj) &&
!isMarkedPrev(obj);
}
// This is used when copying an object to survivor space.
// If the object is marked live, then we mark the copy live.
// If the object is allocated since the start of this mark
// cycle, then we mark the copy live.
// If the object has been around since the previous mark
// phase, and hasn't been marked yet during this phase,
// then we don't mark it, we just wait for the
// current marking cycle to get to it.
// This function returns true when an object has been
// around since the previous marking and hasn't yet
// been marked during this marking.
bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
return
!hr->obj_allocated_since_next_marking(obj) &&
!isMarkedNext(obj);
}
// Determine if an object is dead, given only the object itself.
// This will find the region to which the object belongs and
// then call the region version of the same function.
// Added if it is in permanent gen it isn't dead.
// Added if it is NULL it isn't dead.
// use_prev_marking == true -> use "prev" marking information,
// use_prev_marking == false -> use "next" marking information
bool is_obj_dead_cond(const oop obj,
const bool use_prev_marking) {
if (use_prev_marking) {
return is_obj_dead(obj);
} else {
return is_obj_ill(obj);
}
}
bool is_obj_dead(const oop obj) {
const HeapRegion* hr = heap_region_containing(obj);
if (hr == NULL) {
if (Universe::heap()->is_in_permanent(obj))
return false;
else if (obj == NULL) return false;
else return true;
}
else return is_obj_dead(obj, hr);
}
bool is_obj_ill(const oop obj) {
const HeapRegion* hr = heap_region_containing(obj);
if (hr == NULL) {
if (Universe::heap()->is_in_permanent(obj))
return false;
else if (obj == NULL) return false;
else return true;
}
else return is_obj_ill(obj, hr);
}
// The following is just to alert the verification code
// that a full collection has occurred and that the
// remembered sets are no longer up to date.
bool _full_collection;
void set_full_collection() { _full_collection = true;}
void clear_full_collection() {_full_collection = false;}
bool full_collection() {return _full_collection;}
ConcurrentMark* concurrent_mark() const { return _cm; }
ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
// The dirty cards region list is used to record a subset of regions
// whose cards need clearing. The list if populated during the
// remembered set scanning and drained during the card table
// cleanup. Although the methods are reentrant, population/draining
// phases must not overlap. For synchronization purposes the last
// element on the list points to itself.
HeapRegion* _dirty_cards_region_list;
void push_dirty_cards_region(HeapRegion* hr);
HeapRegion* pop_dirty_cards_region();
public:
void stop_conc_gc_threads();
// <NEW PREDICTION>
double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
void check_if_region_is_too_expensive(double predicted_time_ms);
size_t pending_card_num();
size_t max_pending_card_num();
size_t cards_scanned();
// </NEW PREDICTION>
protected:
size_t _max_heap_capacity;
public:
// Temporary: call to mark things unimplemented for the G1 heap (e.g.,
// MemoryService). In productization, we can make this assert false
// to catch such places (as well as searching for calls to this...)
static void g1_unimplemented();
};
#define use_local_bitmaps 1
#define verify_local_bitmaps 0
#define oop_buffer_length 256
#ifndef PRODUCT
class GCLabBitMap;
class GCLabBitMapClosure: public BitMapClosure {
private:
ConcurrentMark* _cm;
GCLabBitMap* _bitmap;
public:
GCLabBitMapClosure(ConcurrentMark* cm,
GCLabBitMap* bitmap) {
_cm = cm;
_bitmap = bitmap;
}
virtual bool do_bit(size_t offset);
};
#endif // !PRODUCT
class GCLabBitMap: public BitMap {
private:
ConcurrentMark* _cm;
int _shifter;
size_t _bitmap_word_covers_words;
// beginning of the heap
HeapWord* _heap_start;
// this is the actual start of the GCLab
HeapWord* _real_start_word;
// this is the actual end of the GCLab
HeapWord* _real_end_word;
// this is the first word, possibly located before the actual start
// of the GCLab, that corresponds to the first bit of the bitmap
HeapWord* _start_word;
// size of a GCLab in words
size_t _gclab_word_size;
static int shifter() {
return MinObjAlignment - 1;
}
// how many heap words does a single bitmap word corresponds to?
static size_t bitmap_word_covers_words() {
return BitsPerWord << shifter();
}
size_t gclab_word_size() const {
return _gclab_word_size;
}
// Calculates actual GCLab size in words
size_t gclab_real_word_size() const {
return bitmap_size_in_bits(pointer_delta(_real_end_word, _start_word))
/ BitsPerWord;
}
static size_t bitmap_size_in_bits(size_t gclab_word_size) {
size_t bits_in_bitmap = gclab_word_size >> shifter();
// We are going to ensure that the beginning of a word in this
// bitmap also corresponds to the beginning of a word in the
// global marking bitmap. To handle the case where a GCLab
// starts from the middle of the bitmap, we need to add enough
// space (i.e. up to a bitmap word) to ensure that we have
// enough bits in the bitmap.
return bits_in_bitmap + BitsPerWord - 1;
}
public:
GCLabBitMap(HeapWord* heap_start, size_t gclab_word_size)
: BitMap(bitmap_size_in_bits(gclab_word_size)),
_cm(G1CollectedHeap::heap()->concurrent_mark()),
_shifter(shifter()),
_bitmap_word_covers_words(bitmap_word_covers_words()),
_heap_start(heap_start),
_gclab_word_size(gclab_word_size),
_real_start_word(NULL),
_real_end_word(NULL),
_start_word(NULL)
{
guarantee( size_in_words() >= bitmap_size_in_words(),
"just making sure");
}
inline unsigned heapWordToOffset(HeapWord* addr) {
unsigned offset = (unsigned) pointer_delta(addr, _start_word) >> _shifter;
assert(offset < size(), "offset should be within bounds");
return offset;
}
inline HeapWord* offsetToHeapWord(size_t offset) {
HeapWord* addr = _start_word + (offset << _shifter);
assert(_real_start_word <= addr && addr < _real_end_word, "invariant");
return addr;
}
bool fields_well_formed() {
bool ret1 = (_real_start_word == NULL) &&
(_real_end_word == NULL) &&
(_start_word == NULL);
if (ret1)
return true;
bool ret2 = _real_start_word >= _start_word &&
_start_word < _real_end_word &&
(_real_start_word + _gclab_word_size) == _real_end_word &&
(_start_word + _gclab_word_size + _bitmap_word_covers_words)
> _real_end_word;
return ret2;
}
inline bool mark(HeapWord* addr) {
guarantee(use_local_bitmaps, "invariant");
assert(fields_well_formed(), "invariant");
if (addr >= _real_start_word && addr < _real_end_word) {
assert(!isMarked(addr), "should not have already been marked");
// first mark it on the bitmap
at_put(heapWordToOffset(addr), true);
return true;
} else {
return false;
}
}
inline bool isMarked(HeapWord* addr) {
guarantee(use_local_bitmaps, "invariant");
assert(fields_well_formed(), "invariant");
return at(heapWordToOffset(addr));
}
void set_buffer(HeapWord* start) {
guarantee(use_local_bitmaps, "invariant");
clear();
assert(start != NULL, "invariant");
_real_start_word = start;
_real_end_word = start + _gclab_word_size;
size_t diff =
pointer_delta(start, _heap_start) % _bitmap_word_covers_words;
_start_word = start - diff;
assert(fields_well_formed(), "invariant");
}
#ifndef PRODUCT
void verify() {
// verify that the marks have been propagated
GCLabBitMapClosure cl(_cm, this);
iterate(&cl);
}
#endif // PRODUCT
void retire() {
guarantee(use_local_bitmaps, "invariant");
assert(fields_well_formed(), "invariant");
if (_start_word != NULL) {
CMBitMap* mark_bitmap = _cm->nextMarkBitMap();
// this means that the bitmap was set up for the GCLab
assert(_real_start_word != NULL && _real_end_word != NULL, "invariant");
mark_bitmap->mostly_disjoint_range_union(this,
0, // always start from the start of the bitmap
_start_word,
gclab_real_word_size());
_cm->grayRegionIfNecessary(MemRegion(_real_start_word, _real_end_word));
#ifndef PRODUCT
if (use_local_bitmaps && verify_local_bitmaps)
verify();
#endif // PRODUCT
} else {
assert(_real_start_word == NULL && _real_end_word == NULL, "invariant");
}
}
size_t bitmap_size_in_words() const {
return (bitmap_size_in_bits(gclab_word_size()) + BitsPerWord - 1) / BitsPerWord;
}
};
class G1ParGCAllocBuffer: public ParGCAllocBuffer {
private:
bool _retired;
bool _during_marking;
GCLabBitMap _bitmap;
public:
G1ParGCAllocBuffer(size_t gclab_word_size) :
ParGCAllocBuffer(gclab_word_size),
_during_marking(G1CollectedHeap::heap()->mark_in_progress()),
_bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
_retired(false)
{ }
inline bool mark(HeapWord* addr) {
guarantee(use_local_bitmaps, "invariant");
assert(_during_marking, "invariant");
return _bitmap.mark(addr);
}
inline void set_buf(HeapWord* buf) {
if (use_local_bitmaps && _during_marking)
_bitmap.set_buffer(buf);
ParGCAllocBuffer::set_buf(buf);
_retired = false;
}
inline void retire(bool end_of_gc, bool retain) {
if (_retired)
return;
if (use_local_bitmaps && _during_marking) {
_bitmap.retire();
}
ParGCAllocBuffer::retire(end_of_gc, retain);
_retired = true;
}
};
class G1ParScanThreadState : public StackObj {
protected:
G1CollectedHeap* _g1h;
RefToScanQueue* _refs;
DirtyCardQueue _dcq;
CardTableModRefBS* _ct_bs;
G1RemSet* _g1_rem;
G1ParGCAllocBuffer _surviving_alloc_buffer;
G1ParGCAllocBuffer _tenured_alloc_buffer;
G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
ageTable _age_table;
size_t _alloc_buffer_waste;
size_t _undo_waste;
OopsInHeapRegionClosure* _evac_failure_cl;
G1ParScanHeapEvacClosure* _evac_cl;
G1ParScanPartialArrayClosure* _partial_scan_cl;
int _hash_seed;
int _queue_num;
size_t _term_attempts;
double _start;
double _start_strong_roots;
double _strong_roots_time;
double _start_term;
double _term_time;
// Map from young-age-index (0 == not young, 1 is youngest) to
// surviving words. base is what we get back from the malloc call
size_t* _surviving_young_words_base;
// this points into the array, as we use the first few entries for padding
size_t* _surviving_young_words;
#define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
void add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
void add_to_undo_waste(size_t waste) { _undo_waste += waste; }
DirtyCardQueue& dirty_card_queue() { return _dcq; }
CardTableModRefBS* ctbs() { return _ct_bs; }
template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
if (!from->is_survivor()) {
_g1_rem->par_write_ref(from, p, tid);
}
}
template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
// If the new value of the field points to the same region or
// is the to-space, we don't need to include it in the Rset updates.
if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
size_t card_index = ctbs()->index_for(p);
// If the card hasn't been added to the buffer, do it.
if (ctbs()->mark_card_deferred(card_index)) {
dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
}
}
}
public:
G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num);
~G1ParScanThreadState() {
FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
}
RefToScanQueue* refs() { return _refs; }
ageTable* age_table() { return &_age_table; }
G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
return _alloc_buffers[purpose];
}
size_t alloc_buffer_waste() const { return _alloc_buffer_waste; }
size_t undo_waste() const { return _undo_waste; }
#ifdef ASSERT
bool verify_ref(narrowOop* ref) const;
bool verify_ref(oop* ref) const;
bool verify_task(StarTask ref) const;
#endif // ASSERT
template <class T> void push_on_queue(T* ref) {
assert(verify_ref(ref), "sanity");
refs()->push(ref);
}
template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
if (G1DeferredRSUpdate) {
deferred_rs_update(from, p, tid);
} else {
immediate_rs_update(from, p, tid);
}
}
HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
HeapWord* obj = NULL;
size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
assert(gclab_word_size == alloc_buf->word_sz(),
"dynamic resizing is not supported");
add_to_alloc_buffer_waste(alloc_buf->words_remaining());
alloc_buf->retire(false, false);
HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
if (buf == NULL) return NULL; // Let caller handle allocation failure.
// Otherwise.
alloc_buf->set_buf(buf);
obj = alloc_buf->allocate(word_sz);
assert(obj != NULL, "buffer was definitely big enough...");
} else {
obj = _g1h->par_allocate_during_gc(purpose, word_sz);
}
return obj;
}
HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
if (obj != NULL) return obj;
return allocate_slow(purpose, word_sz);
}
void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
if (alloc_buffer(purpose)->contains(obj)) {
assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
"should contain whole object");
alloc_buffer(purpose)->undo_allocation(obj, word_sz);
} else {
CollectedHeap::fill_with_object(obj, word_sz);
add_to_undo_waste(word_sz);
}
}
void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
_evac_failure_cl = evac_failure_cl;
}
OopsInHeapRegionClosure* evac_failure_closure() {
return _evac_failure_cl;
}
void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
_evac_cl = evac_cl;
}
void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
_partial_scan_cl = partial_scan_cl;
}
int* hash_seed() { return &_hash_seed; }
int queue_num() { return _queue_num; }
size_t term_attempts() const { return _term_attempts; }
void note_term_attempt() { _term_attempts++; }
void start_strong_roots() {
_start_strong_roots = os::elapsedTime();
}
void end_strong_roots() {
_strong_roots_time += (os::elapsedTime() - _start_strong_roots);
}
double strong_roots_time() const { return _strong_roots_time; }
void start_term_time() {
note_term_attempt();
_start_term = os::elapsedTime();
}
void end_term_time() {
_term_time += (os::elapsedTime() - _start_term);
}
double term_time() const { return _term_time; }
double elapsed_time() const {
return os::elapsedTime() - _start;
}
static void
print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
void
print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
size_t* surviving_young_words() {
// We add on to hide entry 0 which accumulates surviving words for
// age -1 regions (i.e. non-young ones)
return _surviving_young_words;
}
void retire_alloc_buffers() {
for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
size_t waste = _alloc_buffers[ap]->words_remaining();
add_to_alloc_buffer_waste(waste);
_alloc_buffers[ap]->retire(true, false);
}
}
template <class T> void deal_with_reference(T* ref_to_scan) {
if (has_partial_array_mask(ref_to_scan)) {
_partial_scan_cl->do_oop_nv(ref_to_scan);
} else {
// Note: we can use "raw" versions of "region_containing" because
// "obj_to_scan" is definitely in the heap, and is not in a
// humongous region.
HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
_evac_cl->set_region(r);
_evac_cl->do_oop_nv(ref_to_scan);
}
}
void deal_with_reference(StarTask ref) {
assert(verify_task(ref), "sanity");
if (ref.is_narrow()) {
deal_with_reference((narrowOop*)ref);
} else {
deal_with_reference((oop*)ref);
}
}
public:
void trim_queue();
};
#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP