7113006: G1: excessive ergo output when an evac failure happens
Summary: Introduce a flag that is set when a heap expansion attempt during a GC fails so that we do not consantly attempt to expand the heap when it's going to fail anyway. This not only prevents the excessive ergo output (which is generated when a region allocation fails) but also avoids excessive and ultimately unsuccessful expansion attempts.
Reviewed-by: jmasa, johnc
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* under the terms of the GNU General Public License version 2 only, as
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*
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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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#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/g1AllocRegion.hpp"
#include "gc_implementation/g1/g1HRPrinter.hpp"
#include "gc_implementation/g1/g1RemSet.hpp"
#include "gc_implementation/g1/g1MonitoringSupport.hpp"
#include "gc_implementation/g1/heapRegionSeq.hpp"
#include "gc_implementation/g1/heapRegionSets.hpp"
#include "gc_implementation/shared/hSpaceCounters.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 HRRSCleanupTask;
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 GenerationCounters;
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 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; }
// Currently we do not keep track of the used byte sum for the
// young list and the survivors and it'd be quite a lot of work to
// do so. When we'll eventually replace the young list with
// instances of HeapRegionLinkedList we'll get that for free. So,
// we'll report the more accurate information then.
size_t eden_used_bytes() {
assert(length() >= survivor_length(), "invariant");
return (length() - survivor_length()) * HeapRegion::GrainBytes;
}
size_t survivor_used_bytes() {
return survivor_length() * HeapRegion::GrainBytes;
}
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 MutatorAllocRegion : public G1AllocRegion {
protected:
virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
public:
MutatorAllocRegion()
: G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
};
// The G1 STW is alive closure.
// An instance is embedded into the G1CH and used as the
// (optional) _is_alive_non_header closure in the STW
// reference processor. It is also extensively used during
// refence processing during STW evacuation pauses.
class G1STWIsAliveClosure: public BoolObjectClosure {
G1CollectedHeap* _g1;
public:
G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
void do_object(oop p) { assert(false, "Do not call."); }
bool do_object_b(oop p);
};
class SurvivorGCAllocRegion : public G1AllocRegion {
protected:
virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
public:
SurvivorGCAllocRegion()
: G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
};
class OldGCAllocRegion : public G1AllocRegion {
protected:
virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
public:
OldGCAllocRegion()
: G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
};
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;
friend class MutatorAllocRegion;
friend class SurvivorGCAllocRegion;
friend class OldGCAllocRegion;
// 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 RegionResetter;
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 master free list. It will satisfy all new region allocations.
MasterFreeRegionList _free_list;
// The secondary free list which contains regions that have been
// freed up during the cleanup process. This will be appended to the
// master free list when appropriate.
SecondaryFreeRegionList _secondary_free_list;
// It keeps track of the old regions.
MasterOldRegionSet _old_set;
// It keeps track of the humongous regions.
MasterHumongousRegionSet _humongous_set;
// The number of regions we could create by expansion.
size_t _expansion_regions;
// The block offset table for the G1 heap.
G1BlockOffsetSharedArray* _bot_shared;
// Tears down the region sets / lists so that they are empty and the
// regions on the heap do not belong to a region set / list. The
// only exception is the humongous set which we leave unaltered. If
// free_list_only is true, it will only tear down the master free
// list. It is called before a Full GC (free_list_only == false) or
// before heap shrinking (free_list_only == true).
void tear_down_region_sets(bool free_list_only);
// Rebuilds the region sets / lists so that they are repopulated to
// reflect the contents of the heap. The only exception is the
// humongous set which was not torn down in the first place. If
// free_list_only is true, it will only rebuild the master free
// list. It is called after a Full GC (free_list_only == false) or
// after heap shrinking (free_list_only == true).
void rebuild_region_sets(bool free_list_only);
// The sequence of all heap regions in the heap.
HeapRegionSeq _hrs;
// Alloc region used to satisfy mutator allocation requests.
MutatorAllocRegion _mutator_alloc_region;
// Alloc region used to satisfy allocation requests by the GC for
// survivor objects.
SurvivorGCAllocRegion _survivor_gc_alloc_region;
// Alloc region used to satisfy allocation requests by the GC for
// old objects.
OldGCAllocRegion _old_gc_alloc_region;
// The last old region we allocated to during the last GC.
// Typically, it is not full so we should re-use it during the next GC.
HeapRegion* _retained_old_gc_alloc_region;
// It specifies whether we should attempt to expand the heap after a
// region allocation failure. If heap expansion fails we set this to
// false so that we don't re-attempt the heap expansion (it's likely
// that subsequent expansion attempts will also fail if one fails).
// Currently, it is only consulted during GC and it's reset at the
// start of each GC.
bool _expand_heap_after_alloc_failure;
// It resets the mutator alloc region before new allocations can take place.
void init_mutator_alloc_region();
// It releases the mutator alloc region.
void release_mutator_alloc_region();
// It initializes the GC alloc regions at the start of a GC.
void init_gc_alloc_regions();
// It releases the GC alloc regions at the end of a GC.
void release_gc_alloc_regions();
// It does any cleanup that needs to be done on the GC alloc regions
// before a Full GC.
void abandon_gc_alloc_regions();
// Helper for monitoring and management support.
G1MonitoringSupport* _g1mm;
// Determines PLAB size for a particular allocation purpose.
static size_t desired_plab_sz(GCAllocPurpose purpose);
// 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;
G1HRPrinter _hr_printer;
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;
// This is a non-product method that is helpful for testing. It is
// called at the end of a GC and artificially expands the heap by
// allocating a number of dead regions. This way we can induce very
// frequent marking cycles and stress the cleanup / concurrent
// cleanup code more (as all the regions that will be allocated by
// this method will be found dead by the marking cycle).
void allocate_dummy_regions() PRODUCT_RETURN;
// 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 locked: %s, at safepoint: %s, is VM thread: %s", \
(_extra_message_), \
BOOL_TO_STR(Heap_lock->owned_by_self()), \
BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
BOOL_TO_STR(Thread::current()->is_VM_thread()))
#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(_should_be_vm_thread_) \
do { \
assert(Heap_lock->owned_by_self() || \
(SafepointSynchronize::is_at_safepoint() && \
((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
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(_should_be_vm_thread_) \
do { \
assert(SafepointSynchronize::is_at_safepoint() && \
((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
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:
// The young region list.
YoungList* _young_list;
// The current policy object for the collector.
G1CollectorPolicy* _g1_policy;
// This is the second level of trying to allocate a new region. If
// new_region() didn't find a region on the free_list, this call will
// check whether there's anything available on the
// secondary_free_list and/or wait for more regions to appear on
// that list, if _free_regions_coming is set.
HeapRegion* new_region_try_secondary_free_list();
// Try to allocate a single non-humongous HeapRegion sufficient for
// an allocation of the given word_size. If do_expand is true,
// attempt to expand the heap if necessary to satisfy the allocation
// request.
HeapRegion* new_region(size_t word_size, bool do_expand);
// Attempt to satisfy a humongous allocation request of the given
// size by finding a contiguous set of free regions of num_regions
// length and remove them from the master free list. Return the
// index of the first region or G1_NULL_HRS_INDEX if the search
// was unsuccessful.
size_t humongous_obj_allocate_find_first(size_t num_regions,
size_t word_size);
// Initialize a contiguous set of free regions of length num_regions
// and starting at index first so that they appear as a single
// humongous region.
HeapWord* humongous_obj_allocate_initialize_regions(size_t first,
size_t num_regions,
size_t word_size);
// Attempt to allocate a humongous object of the given size. Return
// NULL if unsuccessful.
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().
//
// * 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* gc_overhead_limit_was_exceeded);
// The following three methods take a gc_count_before_ret
// parameter which is used to return the GC count if the method
// returns NULL. Given that we are required to read the GC count
// while holding the Heap_lock, and these paths will take the
// Heap_lock at some point, it's easier to get them to read the GC
// count while holding the Heap_lock before they return NULL instead
// of the caller (namely: mem_allocate()) having to also take the
// Heap_lock just to read the GC count.
// First-level mutator allocation attempt: try to allocate out of
// the mutator alloc region without taking the Heap_lock. This
// should only be used for non-humongous allocations.
inline HeapWord* attempt_allocation(size_t word_size,
unsigned int* gc_count_before_ret);
// Second-level mutator allocation attempt: take the Heap_lock and
// retry the allocation attempt, potentially scheduling a GC
// pause. This should only be used for non-humongous allocations.
HeapWord* attempt_allocation_slow(size_t word_size,
unsigned int* gc_count_before_ret);
// Takes the Heap_lock and attempts a humongous allocation. It can
// potentially schedule a GC pause.
HeapWord* attempt_allocation_humongous(size_t word_size,
unsigned int* gc_count_before_ret);
// Allocation attempt that should be called during safepoints (e.g.,
// at the end of a successful GC). expect_null_mutator_alloc_region
// specifies whether the mutator alloc region is expected to be NULL
// or not.
HeapWord* attempt_allocation_at_safepoint(size_t word_size,
bool expect_null_mutator_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);
// Allocation attempt during GC for a survivor object / PLAB.
inline HeapWord* survivor_attempt_allocation(size_t word_size);
// Allocation attempt during GC for an old object / PLAB.
inline HeapWord* old_attempt_allocation(size_t word_size);
// These methods are the "callbacks" from the G1AllocRegion class.
// For mutator alloc regions.
HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
void retire_mutator_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes);
// For GC alloc regions.
HeapRegion* new_gc_alloc_region(size_t word_size, size_t count,
GCAllocPurpose ap);
void retire_gc_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes, GCAllocPurpose ap);
// - 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);
// Process any reference objects discovered during
// an incremental evacuation pause.
void process_discovered_references();
// Enqueue any remaining discovered references
// after processing.
void enqueue_discovered_references();
public:
G1MonitoringSupport* g1mm() {
assert(_g1mm != NULL, "should have been initialized");
return _g1mm;
}
// Expand the garbage-first heap by at least the given size (in bytes!).
// Returns true if the heap was expanded by the requested amount;
// false otherwise.
// (Rounds up to a HeapRegion boundary.)
bool 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");
size_t index = r->hrs_index();
assert(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;
}
G1HRPrinter* hr_printer() { return &_hr_printer; }
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);
// Frees a non-humongous region by initializing its contents and
// adding it to the free list that's passed as a parameter (this is
// usually a local list which will be appended to the master free
// list later). The used bytes of freed regions are accumulated in
// pre_used. If par is true, the region's RSet will not be freed
// up. The assumption is that this will be done later.
void free_region(HeapRegion* hr,
size_t* pre_used,
FreeRegionList* free_list,
bool par);
// Frees a humongous region by collapsing it into individual regions
// and calling free_region() for each of them. The freed regions
// will be added to the free list that's passed as a parameter (this
// is usually a local list which will be appended to the master free
// list later). The used bytes of freed regions are accumulated in
// pre_used. If par is true, the region's RSet will not be freed
// up. The assumption is that this will be done later.
void free_humongous_region(HeapRegion* hr,
size_t* pre_used,
FreeRegionList* free_list,
HumongousRegionSet* humongous_proxy_set,
bool par);
// Notifies all the necessary spaces that the committed space has
// been updated (either expanded or shrunk). It should be called
// after _g1_storage is updated.
void update_committed_space(HeapWord* old_end, HeapWord* new_end);
// The concurrent marker (and the thread it runs in.)
ConcurrentMark* _cm;
ConcurrentMarkThread* _cmThread;
bool _mark_in_progress;
// The concurrent refiner.
ConcurrentG1Refine* _cg1r;
// 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.
oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj,
bool should_mark_root);
void handle_evacuation_failure_common(oop obj, markOop m);
// ("Weak") Reference processing support.
//
// G1 has 2 instances of the referece processor class. One
// (_ref_processor_cm) handles reference object discovery
// and subsequent processing during concurrent marking cycles.
//
// The other (_ref_processor_stw) handles reference object
// discovery and processing during full GCs and incremental
// evacuation pauses.
//
// During an incremental pause, reference discovery will be
// temporarily disabled for _ref_processor_cm and will be
// enabled for _ref_processor_stw. At the end of the evacuation
// pause references discovered by _ref_processor_stw will be
// processed and discovery will be disabled. The previous
// setting for reference object discovery for _ref_processor_cm
// will be re-instated.
//
// At the start of marking:
// * Discovery by the CM ref processor is verified to be inactive
// and it's discovered lists are empty.
// * Discovery by the CM ref processor is then enabled.
//
// At the end of marking:
// * Any references on the CM ref processor's discovered
// lists are processed (possibly MT).
//
// At the start of full GC we:
// * Disable discovery by the CM ref processor and
// empty CM ref processor's discovered lists
// (without processing any entries).
// * Verify that the STW ref processor is inactive and it's
// discovered lists are empty.
// * Temporarily set STW ref processor discovery as single threaded.
// * Temporarily clear the STW ref processor's _is_alive_non_header
// field.
// * Finally enable discovery by the STW ref processor.
//
// The STW ref processor is used to record any discovered
// references during the full GC.
//
// At the end of a full GC we:
// * Enqueue any reference objects discovered by the STW ref processor
// that have non-live referents. This has the side-effect of
// making the STW ref processor inactive by disabling discovery.
// * Verify that the CM ref processor is still inactive
// and no references have been placed on it's discovered
// lists (also checked as a precondition during initial marking).
// The (stw) reference processor...
ReferenceProcessor* _ref_processor_stw;
// During reference object discovery, the _is_alive_non_header
// closure (if non-null) is applied to the referent object to
// determine whether the referent is live. If so then the
// reference object does not need to be 'discovered' and can
// be treated as a regular oop. This has the benefit of reducing
// the number of 'discovered' reference objects that need to
// be processed.
//
// Instance of the is_alive closure for embedding into the
// STW reference processor as the _is_alive_non_header field.
// Supplying a value for the _is_alive_non_header field is
// optional but doing so prevents unnecessary additions to
// the discovered lists during reference discovery.
G1STWIsAliveClosure _is_alive_closure_stw;
// The (concurrent marking) reference processor...
ReferenceProcessor* _ref_processor_cm;
// Instance of the concurrent mark is_alive closure for embedding
// into the Concurrent Marking reference processor as the
// _is_alive_non_header field. Supplying a value for the
// _is_alive_non_header field is optional but doing so prevents
// unnecessary additions to the discovered lists during reference
// discovery.
G1CMIsAliveClosure _is_alive_closure_cm;
// Cache used by G1CollectedHeap::start_cset_region_for_worker().
HeapRegion** _worker_cset_start_region;
// Time stamp to validate the regions recorded in the cache
// used by G1CollectedHeap::start_cset_region_for_worker().
// The heap region entry for a given worker is valid iff
// the associated time stamp value matches the current value
// of G1CollectedHeap::_gc_time_stamp.
unsigned int* _worker_cset_start_region_time_stamp;
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;
volatile bool _free_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();
// Initialize weak reference processing.
virtual void ref_processing_init();
void set_par_threads(uint t) {
SharedHeap::set_par_threads(t);
// Done in SharedHeap but oddly there are
// two _process_strong_tasks's in a G1CollectedHeap
// so do it here too.
_process_strong_tasks->set_n_threads(t);
}
// Set _n_par_threads according to a policy TBD.
void set_par_threads();
void set_n_termination(int 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();
// Clear the cached CSet starting regions and time stamps.
// Their validity is dependent on the GC timestamp.
clear_cset_start_regions();
}
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 accessors
// The STW reference processor....
ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
// The Concurent Marking reference processor...
ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
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;
// 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() { return _hrs.length(); }
// The max number of regions in the heap.
size_t max_regions() { return _hrs.max_length(); }
// The number of regions that are completely free.
size_t free_regions() { return _free_list.length(); }
// The number of regions that are not completely free.
size_t used_regions() { return n_regions() - free_regions(); }
// The number of regions available for "regular" expansion.
size_t expansion_regions() { return _expansion_regions; }
// Factory method for HeapRegion instances. It will return NULL if
// the allocation fails.
HeapRegion* new_heap_region(size_t hrs_index, HeapWord* bottom);
void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
void verify_dirty_young_regions() PRODUCT_RETURN;
// verify_region_sets() performs verification over the region
// lists. It will be compiled in the product code to be used when
// necessary (i.e., during heap verification).
void verify_region_sets();
// verify_region_sets_optional() is planted in the code for
// list verification in non-product builds (and it can be enabled in
// product builds by definning HEAP_REGION_SET_FORCE_VERIFY to be 1).
#if HEAP_REGION_SET_FORCE_VERIFY
void verify_region_sets_optional() {
verify_region_sets();
}
#else // HEAP_REGION_SET_FORCE_VERIFY
void verify_region_sets_optional() { }
#endif // HEAP_REGION_SET_FORCE_VERIFY
#ifdef ASSERT
bool is_on_master_free_list(HeapRegion* hr) {
return hr->containing_set() == &_free_list;
}
bool is_in_humongous_set(HeapRegion* hr) {
return hr->containing_set() == &_humongous_set;
}
#endif // ASSERT
// Wrapper for the region list operations that can be called from
// methods outside this class.
void secondary_free_list_add_as_tail(FreeRegionList* list) {
_secondary_free_list.add_as_tail(list);
}
void append_secondary_free_list() {
_free_list.add_as_head(&_secondary_free_list);
}
void append_secondary_free_list_if_not_empty_with_lock() {
// If the secondary free list looks empty there's no reason to
// take the lock and then try to append it.
if (!_secondary_free_list.is_empty()) {
MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
append_secondary_free_list();
}
}
void old_set_remove(HeapRegion* hr) {
_old_set.remove(hr);
}
void set_free_regions_coming();
void reset_free_regions_coming();
bool free_regions_coming() { return _free_regions_coming; }
void wait_while_free_regions_coming();
// 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; }
// It will free a region if it has allocated objects in it that are
// all dead. It calls either free_region() or
// free_humongous_region() depending on the type of the region that
// is passed to it.
void free_region_if_empty(HeapRegion* hr,
size_t* pre_used,
FreeRegionList* free_list,
OldRegionSet* old_proxy_set,
HumongousRegionSet* humongous_proxy_set,
HRRSCleanupTask* hrrs_cleanup_task,
bool par);
// It appends the free list to the master free list and updates the
// master humongous list according to the contents of the proxy
// list. It also adjusts the total used bytes according to pre_used
// (if par is true, it will do so by taking the ParGCRareEvent_lock).
void update_sets_after_freeing_regions(size_t pre_used,
FreeRegionList* free_list,
OldRegionSet* old_proxy_set,
HumongousRegionSet* humongous_proxy_set,
bool par);
// Returns "TRUE" iff "p" points into the committed areas 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
// reserved for the heap
MemRegion g1_reserved() {
return _g1_reserved;
}
// Returns a MemRegion that corresponds to the space that has been
// committed in the heap
MemRegion g1_committed() {
return _g1_committed;
}
virtual bool is_in_closed_subset(const void* p) const;
// 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) const;
// 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) const;
// Return the region with the given index. It assumes the index is valid.
HeapRegion* region_at(size_t index) const { return _hrs.at(index); }
// 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,
uint worker,
uint no_of_par_workers,
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);
// Same as the routine above but only checks regions in the
// current collection set.
bool check_cset_heap_region_claim_values(jint claim_value);
#endif // ASSERT
// Clear the cached cset start regions and (more importantly)
// the time stamps. Called when we reset the GC time stamp.
void clear_cset_start_regions();
// Given the id of a worker, obtain or calculate a suitable
// starting region for iterating over the current collection set.
HeapRegion* start_cset_region_for_worker(int worker_i);
// 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.
template <class T>
inline HeapRegion* heap_region_containing(const T 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.
template <class T>
inline HeapRegion* heap_region_containing_raw(const T 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 {
return true;
}
virtual bool card_mark_must_follow_store() const {
return true;
}
bool is_in_young(const oop obj) {
HeapRegion* hr = heap_region_containing(obj);
return hr != NULL && hr->is_young();
}
#ifdef ASSERT
virtual bool is_in_partial_collection(const void* p);
#endif
virtual bool is_scavengable(const void* addr);
// 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.
virtual bool can_elide_initializing_store_barrier(oop new_obj) {
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;
}
// 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.
// vo == UsePrevMarking -> use "prev" marking information,
// vo == UseNextMarking -> use "next" marking information
// vo == UseMarkWord -> use the mark word in the object header
//
// NOTE: Only the "prev" marking information is guaranteed to be
// consistent most of the time, so most calls to this should use
// vo == UsePrevMarking.
// Currently, there is only one case where this is called with
// vo == UseNextMarking, which is to verify the "next" marking
// information at the end of remark.
// Currently there is only one place where this is called with
// vo == UseMarkWord, which is to verify the marking during a
// full GC.
void verify(bool allow_dirty, bool silent, VerifyOption vo);
// Override; it uses the "prev" marking information
virtual void verify(bool allow_dirty, bool silent);
virtual void print_on(outputStream* st) const;
virtual void print_extended_on(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;
// The following two methods are helpful for debugging RSet issues.
void print_cset_rsets() PRODUCT_RETURN;
void print_all_rsets() PRODUCT_RETURN;
// Convenience function to be used in situations where the heap type can be
// asserted to be this type.
static G1CollectedHeap* heap();
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();
bool isMarkedPrev(oop obj) const;
bool isMarkedNext(oop obj) const;
// vo == UsePrevMarking -> use "prev" marking information,
// vo == UseNextMarking -> use "next" marking information,
// vo == UseMarkWord -> use mark word from object header
bool is_obj_dead_cond(const oop obj,
const HeapRegion* hr,
const VerifyOption vo) const {
switch (vo) {
case VerifyOption_G1UsePrevMarking:
return is_obj_dead(obj, hr);
case VerifyOption_G1UseNextMarking:
return is_obj_ill(obj, hr);
default:
assert(vo == VerifyOption_G1UseMarkWord, "must be");
return !obj->is_gc_marked();
}
}
// 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.
// vo == UsePrevMarking -> use "prev" marking information,
// vo == UseNextMarking -> use "next" marking information,
// vo == UseMarkWord -> use mark word from object header
bool is_obj_dead_cond(const oop obj,
const VerifyOption vo) const {
switch (vo) {
case VerifyOption_G1UsePrevMarking:
return is_obj_dead(obj);
case VerifyOption_G1UseNextMarking:
return is_obj_ill(obj);
default:
assert(vo == VerifyOption_G1UseMarkWord, "must be");
return !obj->is_gc_marked();
}
}
bool is_obj_dead(const oop obj) const {
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 {
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();
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();
protected:
size_t _max_heap_capacity;
};
#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 _should_mark_objects;
GCLabBitMap _bitmap;
public:
G1ParGCAllocBuffer(size_t gclab_word_size);
inline bool mark(HeapWord* addr) {
guarantee(use_local_bitmaps, "invariant");
assert(_should_mark_objects, "invariant");
return _bitmap.mark(addr);
}
inline void set_buf(HeapWord* buf) {
if (use_local_bitmaps && _should_mark_objects) {
_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 && _should_mark_objects) {
_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