8201492: Properly implement non-contiguous generations for Reference discovery
Summary: Collectors like G1 implementing non-contiguous generations previously used an inexact but conservative area for discovery. Concurrent and STW reference processing could discover the same reference multiple times, potentially missing referents during evacuation. So these collectors had to take extra measures while concurrent marking/reference discovery has been running. This change makes discovery exact for G1 (and any collector using non-contiguous generations) so that concurrent discovery and STW discovery discover on strictly disjoint memory areas. This means that the mentioned situation can not occur any more, and extra work is not required any more too.
Reviewed-by: kbarrett, sjohanss
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#ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
#define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
#include "gc/g1/evacuationInfo.hpp"
#include "gc/g1/g1BarrierSet.hpp"
#include "gc/g1/g1BiasedArray.hpp"
#include "gc/g1/g1CardTable.hpp"
#include "gc/g1/g1CollectionSet.hpp"
#include "gc/g1/g1CollectorState.hpp"
#include "gc/g1/g1ConcurrentMark.hpp"
#include "gc/g1/g1EdenRegions.hpp"
#include "gc/g1/g1EvacFailure.hpp"
#include "gc/g1/g1EvacStats.hpp"
#include "gc/g1/g1HeapTransition.hpp"
#include "gc/g1/g1HeapVerifier.hpp"
#include "gc/g1/g1HRPrinter.hpp"
#include "gc/g1/g1InCSetState.hpp"
#include "gc/g1/g1MonitoringSupport.hpp"
#include "gc/g1/g1SurvivorRegions.hpp"
#include "gc/g1/g1YCTypes.hpp"
#include "gc/g1/heapRegionManager.hpp"
#include "gc/g1/heapRegionSet.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/plab.hpp"
#include "gc/shared/preservedMarks.hpp"
#include "gc/shared/softRefPolicy.hpp"
#include "memory/memRegion.hpp"
#include "services/memoryManager.hpp"
#include "utilities/stack.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.
// Forward declarations
class HeapRegion;
class HRRSCleanupTask;
class GenerationSpec;
class G1ParScanThreadState;
class G1ParScanThreadStateSet;
class G1ParScanThreadState;
class MemoryPool;
class ObjectClosure;
class SpaceClosure;
class CompactibleSpaceClosure;
class Space;
class G1CollectionSet;
class G1CollectorPolicy;
class G1Policy;
class G1HotCardCache;
class G1RemSet;
class G1YoungRemSetSamplingThread;
class HeapRegionRemSetIterator;
class G1ConcurrentMark;
class G1ConcurrentMarkThread;
class G1ConcurrentRefine;
class GenerationCounters;
class STWGCTimer;
class G1NewTracer;
class EvacuationFailedInfo;
class nmethod;
class Ticks;
class WorkGang;
class G1Allocator;
class G1ArchiveAllocator;
class G1FullGCScope;
class G1HeapVerifier;
class G1HeapSizingPolicy;
class G1HeapSummary;
class G1EvacSummary;
typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
// 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
// reference processing during STW evacuation pauses.
class G1STWIsAliveClosure : public BoolObjectClosure {
G1CollectedHeap* _g1h;
public:
G1STWIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
bool do_object_b(oop p);
};
class G1STWSubjectToDiscoveryClosure : public BoolObjectClosure {
G1CollectedHeap* _g1h;
public:
G1STWSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
bool do_object_b(oop p);
};
class G1RegionMappingChangedListener : public G1MappingChangedListener {
private:
void reset_from_card_cache(uint start_idx, size_t num_regions);
public:
virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
};
class G1CollectedHeap : public CollectedHeap {
friend class G1FreeCollectionSetTask;
friend class VM_CollectForMetadataAllocation;
friend class VM_G1CollectForAllocation;
friend class VM_G1CollectFull;
friend class VMStructs;
friend class MutatorAllocRegion;
friend class G1FullCollector;
friend class G1GCAllocRegion;
friend class G1HeapVerifier;
// Closures used in implementation.
friend class G1ParScanThreadState;
friend class G1ParScanThreadStateSet;
friend class G1ParTask;
friend class G1PLABAllocator;
friend class G1PrepareCompactClosure;
// Other related classes.
friend class HeapRegionClaimer;
// Testing classes.
friend class G1CheckCSetFastTableClosure;
private:
G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
WorkGang* _workers;
G1CollectorPolicy* _collector_policy;
G1CardTable* _card_table;
SoftRefPolicy _soft_ref_policy;
GCMemoryManager _memory_manager;
GCMemoryManager _full_gc_memory_manager;
MemoryPool* _eden_pool;
MemoryPool* _survivor_pool;
MemoryPool* _old_pool;
static size_t _humongous_object_threshold_in_words;
// It keeps track of the old regions.
HeapRegionSet _old_set;
// It keeps track of the humongous regions.
HeapRegionSet _humongous_set;
virtual void initialize_serviceability();
void eagerly_reclaim_humongous_regions();
// Start a new incremental collection set for the next pause.
void start_new_collection_set();
// The number of regions we could create by expansion.
uint _expansion_regions;
// The block offset table for the G1 heap.
G1BlockOffsetTable* _bot;
// 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);
// Callback for region mapping changed events.
G1RegionMappingChangedListener _listener;
// The sequence of all heap regions in the heap.
HeapRegionManager _hrm;
// Manages all allocations with regions except humongous object allocations.
G1Allocator* _allocator;
// Manages all heap verification.
G1HeapVerifier* _verifier;
// Outside of GC pauses, the number of bytes used in all regions other
// than the current allocation region(s).
size_t _summary_bytes_used;
void increase_used(size_t bytes);
void decrease_used(size_t bytes);
void set_used(size_t bytes);
// Class that handles archive allocation ranges.
G1ArchiveAllocator* _archive_allocator;
// GC allocation statistics policy for survivors.
G1EvacStats _survivor_evac_stats;
// GC allocation statistics policy for tenured objects.
G1EvacStats _old_evac_stats;
// 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;
// Helper for monitoring and management support.
G1MonitoringSupport* _g1mm;
// Records whether the region at the given index is (still) a
// candidate for eager reclaim. Only valid for humongous start
// regions; other regions have unspecified values. Humongous start
// regions are initialized at start of collection pause, with
// candidates removed from the set as they are found reachable from
// roots or the young generation.
class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
protected:
bool default_value() const { return false; }
public:
void clear() { G1BiasedMappedArray<bool>::clear(); }
void set_candidate(uint region, bool value) {
set_by_index(region, value);
}
bool is_candidate(uint region) {
return get_by_index(region);
}
};
HumongousReclaimCandidates _humongous_reclaim_candidates;
// Stores whether during humongous object registration we found candidate regions.
// If not, we can skip a few steps.
bool _has_humongous_reclaim_candidates;
G1HRPrinter _hr_printer;
// 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 == _g1_humongous_allocation
// (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
// (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
// (e) cause == _wb_conc_mark
bool should_do_concurrent_full_gc(GCCause::Cause cause);
// indicates whether we are in young or mixed GC mode
G1CollectorState _collector_state;
// Keeps track of how many "old marking cycles" (i.e., Full GCs or
// concurrent cycles) we have started.
volatile uint _old_marking_cycles_started;
// Keeps track of how many "old marking cycles" (i.e., Full GCs or
// concurrent cycles) we have completed.
volatile uint _old_marking_cycles_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;
// If the HR printer is active, dump the state of the regions in the
// heap after a compaction.
void print_hrm_post_compaction();
// Create a memory mapper for auxiliary data structures of the given size and
// translation factor.
static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
size_t size,
size_t translation_factor);
void trace_heap(GCWhen::Type when, const GCTracer* tracer);
// These are macros so that, if the assert fires, we get the correct
// line number, file, etc.
#define heap_locking_asserts_params(_extra_message_) \
"%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_params("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_params("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_params("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_params("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_params("should not be holding the Heap_lock and " \
"should not be at a safepoint")); \
} while (0)
#define assert_at_safepoint_on_vm_thread() \
do { \
assert_at_safepoint(); \
assert(Thread::current_or_null() != NULL, "no current thread"); \
assert(Thread::current()->is_VM_thread(), "current thread is not VM thread"); \
} while (0)
// The young region list.
G1EdenRegions _eden;
G1SurvivorRegions _survivor;
STWGCTimer* _gc_timer_stw;
G1NewTracer* _gc_tracer_stw;
// The current policy object for the collector.
G1Policy* _g1_policy;
G1HeapSizingPolicy* _heap_sizing_policy;
G1CollectionSet _collection_set;
// 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. If the region is to be used as an old region or for a
// humongous object, set is_old to true. If not, to false.
HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
// 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(uint first,
uint 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 min_size,
size_t requested_size,
size_t* actual_size);
virtual HeapWord* mem_allocate(size_t word_size,
bool* gc_overhead_limit_was_exceeded);
// 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 min_word_size,
size_t desired_word_size,
size_t* actual_word_size);
// 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);
// Takes the Heap_lock and attempts a humongous allocation. It can
// potentially schedule a GC pause.
HeapWord* attempt_allocation_humongous(size_t word_size);
// 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);
// 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.
bool has_more_regions(InCSetState dest);
HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
void retire_gc_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes, InCSetState dest);
// - if explicit_gc is true, the GC is for a System.gc() etc,
// otherwise it's for a failed allocation.
// - if clear_all_soft_refs is true, all soft references should be
// cleared during the GC.
// - it returns false if it is unable to do the collection due to the
// GC locker being active, true otherwise.
bool do_full_collection(bool explicit_gc,
bool clear_all_soft_refs);
// Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
virtual void do_full_collection(bool clear_all_soft_refs);
// Resize the heap if necessary after a full collection.
void resize_if_necessary_after_full_collection();
// 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);
// Internal helpers used during full GC to split it up to
// increase readability.
void abort_concurrent_cycle();
void verify_before_full_collection(bool explicit_gc);
void prepare_heap_for_full_collection();
void prepare_heap_for_mutators();
void abort_refinement();
void verify_after_full_collection();
void print_heap_after_full_collection(G1HeapTransition* heap_transition);
// Helper method for satisfy_failed_allocation()
HeapWord* satisfy_failed_allocation_helper(size_t word_size,
bool do_gc,
bool clear_all_soft_refs,
bool expect_null_mutator_alloc_region,
bool* gc_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(G1ParScanThreadStateSet* per_thread_states);
// Enqueue any remaining discovered references
// after processing.
void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
// Merges the information gathered on a per-thread basis for all worker threads
// during GC into global variables.
void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
public:
G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
WorkGang* workers() const { return _workers; }
G1Allocator* allocator() {
return _allocator;
}
G1HeapVerifier* verifier() {
return _verifier;
}
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, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
// Returns the PLAB statistics for a given destination.
inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
// Determines PLAB size for a given destination.
inline size_t desired_plab_sz(InCSetState dest);
// Do anything common to GC's.
void gc_prologue(bool full);
void gc_epilogue(bool full);
// Does the given region fulfill remembered set based eager reclaim candidate requirements?
bool is_potential_eager_reclaim_candidate(HeapRegion* r) const;
// Modify the reclaim candidate set and test for presence.
// These are only valid for starts_humongous regions.
inline void set_humongous_reclaim_candidate(uint region, bool value);
inline bool is_humongous_reclaim_candidate(uint region);
// Remove from the reclaim candidate set. Also remove from the
// collection set so that later encounters avoid the slow path.
inline void set_humongous_is_live(oop obj);
// Register the given region to be part of the collection set.
inline void register_humongous_region_with_cset(uint index);
// Register regions with humongous objects (actually on the start region) in
// the in_cset_fast_test table.
void register_humongous_regions_with_cset();
// 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_young_region_with_cset(HeapRegion* r) {
_in_cset_fast_test.set_in_young(r->hrm_index());
}
void register_old_region_with_cset(HeapRegion* r) {
_in_cset_fast_test.set_in_old(r->hrm_index());
}
void clear_in_cset(const HeapRegion* hr) {
_in_cset_fast_test.clear(hr);
}
void clear_cset_fast_test() {
_in_cset_fast_test.clear();
}
bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
// This is called at the start of either a concurrent cycle or a Full
// GC to update the number of old marking cycles started.
void increment_old_marking_cycles_started();
// This is called at the end of either a concurrent cycle or a Full
// GC to update the number of old marking cycles 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 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_old_marking_cycles_completed(bool concurrent);
uint old_marking_cycles_completed() {
return _old_marking_cycles_completed;
}
G1HRPrinter* hr_printer() { return &_hr_printer; }
// Allocates a new heap region instance.
HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
// Allocate the highest free region in the reserved heap. This will commit
// regions as necessary.
HeapRegion* alloc_highest_free_region();
// 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 skip_remset is true, the region's RSet will not be freed
// up. If skip_hot_card_cache is true, the region's hot card cache will not
// be freed up. The assumption is that this will be done later.
// The locked parameter indicates if the caller has already taken
// care of proper synchronization. This may allow some optimizations.
void free_region(HeapRegion* hr,
FreeRegionList* free_list,
bool skip_remset,
bool skip_hot_card_cache = false,
bool locked = false);
// It dirties the cards that cover the block 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);
// 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 method assumes that only a single thread is ever calling
// this for a particular region at once.
void free_humongous_region(HeapRegion* hr,
FreeRegionList* free_list);
// Facility for allocating in 'archive' regions in high heap memory and
// recording the allocated ranges. These should all be called from the
// VM thread at safepoints, without the heap lock held. They can be used
// to create and archive a set of heap regions which can be mapped at the
// same fixed addresses in a subsequent JVM invocation.
void begin_archive_alloc_range(bool open = false);
// Check if the requested size would be too large for an archive allocation.
bool is_archive_alloc_too_large(size_t word_size);
// Allocate memory of the requested size from the archive region. This will
// return NULL if the size is too large or if no memory is available. It
// does not trigger a garbage collection.
HeapWord* archive_mem_allocate(size_t word_size);
// Optionally aligns the end address and returns the allocated ranges in
// an array of MemRegions in order of ascending addresses.
void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
size_t end_alignment_in_bytes = 0);
// Facility for allocating a fixed range within the heap and marking
// the containing regions as 'archive'. For use at JVM init time, when the
// caller may mmap archived heap data at the specified range(s).
// Verify that the MemRegions specified in the argument array are within the
// reserved heap.
bool check_archive_addresses(MemRegion* range, size_t count);
// Commit the appropriate G1 regions containing the specified MemRegions
// and mark them as 'archive' regions. The regions in the array must be
// non-overlapping and in order of ascending address.
bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
// Insert any required filler objects in the G1 regions around the specified
// ranges to make the regions parseable. This must be called after
// alloc_archive_regions, and after class loading has occurred.
void fill_archive_regions(MemRegion* range, size_t count);
// For each of the specified MemRegions, uncommit the containing G1 regions
// which had been allocated by alloc_archive_regions. This should be called
// rather than fill_archive_regions at JVM init time if the archive file
// mapping failed, with the same non-overlapping and sorted MemRegion array.
void dealloc_archive_regions(MemRegion* range, size_t count);
private:
// Shrink the garbage-first heap by at most the given size (in bytes!).
// (Rounds down to a HeapRegion boundary.)
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);
void print_taskqueue_stats() 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,
uint gc_count_before,
bool* succeeded,
GCCause::Cause gc_cause);
void wait_for_root_region_scanning();
// 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(G1ParScanThreadStateSet* per_thread_states);
void pre_evacuate_collection_set();
void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
// Print the header for the per-thread termination statistics.
static void print_termination_stats_hdr();
// Print actual per-thread termination statistics.
void print_termination_stats(uint worker_id,
double elapsed_ms,
double strong_roots_ms,
double term_ms,
size_t term_attempts,
size_t alloc_buffer_waste,
size_t undo_waste) const;
// Update object copying statistics.
void record_obj_copy_mem_stats();
// The hot card cache for remembered set insertion optimization.
G1HotCardCache* _hot_card_cache;
// The g1 remembered set of the heap.
G1RemSet* _g1_rem_set;
// A set of cards that cover the objects for which the Rsets should be updated
// concurrently after the collection.
DirtyCardQueueSet _dirty_card_queue_set;
// After a collection pause, convert the regions in the collection set into free
// regions.
void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
// Abandon the current collection set without recording policy
// statistics or updating free lists.
void abandon_collection_set(G1CollectionSet* collection_set);
// The concurrent marker (and the thread it runs in.)
G1ConcurrentMark* _cm;
G1ConcurrentMarkThread* _cm_thread;
// The concurrent refiner.
G1ConcurrentRefine* _cr;
// The parallel task queues
RefToScanQueueSet *_task_queues;
// True iff a evacuation has failed in the current collection.
bool _evacuation_failed;
EvacuationFailedInfo* _evacuation_failed_info_array;
// Failed evacuations cause some logical from-space objects to have
// forwarding pointers to themselves. Reset them.
void remove_self_forwarding_pointers();
// Restore the objects in the regions in the collection set after an
// evacuation failure.
void restore_after_evac_failure();
PreservedMarksSet _preserved_marks_set;
// Preserve the mark of "obj", if necessary, in preparation for its mark
// word being overwritten with a self-forwarding-pointer.
void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
#ifndef PRODUCT
// Support for forcing evacuation failures. Analogous to
// PromotionFailureALot for the other collectors.
// Records whether G1EvacuationFailureALot should be in effect
// for the current GC
bool _evacuation_failure_alot_for_current_gc;
// Used to record the GC number for interval checking when
// determining whether G1EvaucationFailureALot is in effect
// for the current GC.
size_t _evacuation_failure_alot_gc_number;
// Count of the number of evacuations between failures.
volatile size_t _evacuation_failure_alot_count;
// Set whether G1EvacuationFailureALot should be in effect
// for the current GC (based upon the type of GC and which
// command line flags are set);
inline bool evacuation_failure_alot_for_gc_type(bool for_young_gc,
bool during_initial_mark,
bool mark_or_rebuild_in_progress);
inline void set_evacuation_failure_alot_for_current_gc();
// Return true if it's time to cause an evacuation failure.
inline bool evacuation_should_fail();
// Reset the G1EvacuationFailureALot counters. Should be called at
// the end of an evacuation pause in which an evacuation failure occurred.
inline void reset_evacuation_should_fail();
#endif // !PRODUCT
// ("Weak") Reference processing support.
//
// G1 has 2 instances of the reference 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;
G1STWSubjectToDiscoveryClosure _is_subject_to_discovery_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;
G1CMSubjectToDiscoveryClosure _is_subject_to_discovery_cm;
public:
RefToScanQueue *task_queue(uint i) const;
uint num_task_queues() const;
// A set of cards where updates happened during the GC
DirtyCardQueueSet& dirty_card_queue_set() { return _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);
private:
jint initialize_concurrent_refinement();
jint initialize_young_gen_sampling_thread();
public:
// Initialize the G1CollectedHeap to have the initial and
// maximum sizes and remembered and barrier sets
// specified by the policy object.
jint initialize();
virtual void stop();
virtual void safepoint_synchronize_begin();
virtual void safepoint_synchronize_end();
// Return the (conservative) maximum heap alignment for any G1 heap
static size_t conservative_max_heap_alignment();
// Does operations required after initialization has been done.
void post_initialize();
// Initialize weak reference processing.
void ref_processing_init();
virtual Name kind() const {
return CollectedHeap::G1;
}
virtual const char* name() const {
return "G1";
}
const G1CollectorState* collector_state() const { return &_collector_state; }
G1CollectorState* collector_state() { return &_collector_state; }
// The current policy object for the collector.
G1Policy* g1_policy() const { return _g1_policy; }
const G1CollectionSet* collection_set() const { return &_collection_set; }
G1CollectionSet* collection_set() { return &_collection_set; }
virtual CollectorPolicy* collector_policy() const;
virtual SoftRefPolicy* soft_ref_policy();
virtual GrowableArray<GCMemoryManager*> memory_managers();
virtual GrowableArray<MemoryPool*> memory_pools();
// The rem set and barrier set.
G1RemSet* g1_rem_set() const { return _g1_rem_set; }
// Try to minimize the remembered set.
void scrub_rem_set();
// Apply the given closure on all cards in the Hot Card Cache, emptying it.
void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
// Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
// The shared block offset table array.
G1BlockOffsetTable* bot() const { return _bot; }
// Reference Processing accessors
// The STW reference processor....
ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
// The Concurrent Marking reference processor...
ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
size_t unused_committed_regions_in_bytes() const;
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.
virtual bool is_maximal_no_gc() const {
return _hrm.available() == 0;
}
// Returns whether there are any regions left in the heap for allocation.
bool has_regions_left_for_allocation() const {
return !is_maximal_no_gc() || num_free_regions() != 0;
}
// The current number of regions in the heap.
uint num_regions() const { return _hrm.length(); }
// The max number of regions in the heap.
uint max_regions() const { return _hrm.max_length(); }
// The number of regions that are completely free.
uint num_free_regions() const { return _hrm.num_free_regions(); }
MemoryUsage get_auxiliary_data_memory_usage() const {
return _hrm.get_auxiliary_data_memory_usage();
}
// The number of regions that are not completely free.
uint num_used_regions() const { return num_regions() - num_free_regions(); }
#ifdef ASSERT
bool is_on_master_free_list(HeapRegion* hr) {
return _hrm.is_free(hr);
}
#endif // ASSERT
inline void old_set_add(HeapRegion* hr);
inline void old_set_remove(HeapRegion* hr);
size_t non_young_capacity_bytes() {
return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
}
// Determine whether the given region is one that we are using as an
// old GC alloc region.
bool is_old_gc_alloc_region(HeapRegion* hr);
// 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);
// True iff an evacuation has failed in the most-recent collection.
bool evacuation_failed() { return _evacuation_failed; }
void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
void prepend_to_freelist(FreeRegionList* list);
void decrement_summary_bytes(size_t bytes);
virtual bool is_in(const void* p) const;
#ifdef ASSERT
// Returns whether p is in one of the available areas of the heap. Slow but
// extensive version.
bool is_in_exact(const void* p) const;
#endif
// Return "TRUE" iff the given object address is within the collection
// set. Assumes that the reference points into the heap.
inline bool is_in_cset(const HeapRegion *hr);
inline bool is_in_cset(oop obj);
inline bool is_in_cset(HeapWord* addr);
inline bool is_in_cset_or_humongous(const oop obj);
private:
// This array is used for a quick test on whether a reference points into
// the collection set or not. Each of the array's elements denotes whether the
// corresponding region is in the collection set or not.
G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
public:
inline InCSetState in_cset_state(const oop obj);
// Return "TRUE" iff the given object address is in the reserved
// region of g1.
bool is_in_g1_reserved(const void* p) const {
return _hrm.reserved().contains(p);
}
// Returns a MemRegion that corresponds to the space that has been
// reserved for the heap
MemRegion g1_reserved() const {
return _hrm.reserved();
}
virtual bool is_in_closed_subset(const void* p) const;
G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
G1CardTable* card_table() const {
return _card_table;
}
// Iteration functions.
// Iterate over all objects, calling "cl.do_object" on each.
virtual void object_iterate(ObjectClosure* cl);
virtual void safe_object_iterate(ObjectClosure* cl) {
object_iterate(cl);
}
// Iterate over heap regions, in address order, terminating the
// iteration early if the "do_heap_region" method returns "true".
void heap_region_iterate(HeapRegionClosure* blk) const;
// Return the region with the given index. It assumes the index is valid.
inline HeapRegion* region_at(uint index) const;
// Return the next region (by index) that is part of the same
// humongous object that hr is part of.
inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
// Calculate the region index of the given address. Given address must be
// within the heap.
inline uint addr_to_region(HeapWord* addr) const;
inline HeapWord* bottom_addr_for_region(uint index) const;
// Two functions to iterate over the heap regions in parallel. Threads
// compete using the HeapRegionClaimer to claim the regions before
// applying the closure on them.
// The _from_worker_offset version uses the HeapRegionClaimer and
// the worker id to calculate a start offset to prevent all workers to
// start from the point.
void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
HeapRegionClaimer* hrclaimer,
uint worker_id) const;
void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
HeapRegionClaimer* hrclaimer) const;
// Iterate over the regions (if any) in the current collection set.
void collection_set_iterate(HeapRegionClosure* blk);
// Iterate over the regions (if any) in the current collection set. Starts the
// iteration over the entire collection set so that the start regions of a given
// worker id over the set active_workers are evenly spread across the set of
// collection set regions.
void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
// Returns the HeapRegion that contains addr. addr must not be NULL.
template <class T>
inline HeapRegion* heap_region_containing(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;
// Section on thread-local allocation buffers (TLABs)
// See CollectedHeap for semantics.
bool supports_tlab_allocation() const;
size_t tlab_capacity(Thread* ignored) const;
size_t tlab_used(Thread* ignored) const;
size_t max_tlab_size() const;
size_t unsafe_max_tlab_alloc(Thread* ignored) const;
inline bool is_in_young(const oop obj);
// Returns "true" iff the given word_size is "very large".
static bool is_humongous(size_t word_size) {
// Note this has to be strictly greater-than as the TLABs
// are capped at the humongous threshold 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;
}
// Returns the humongous threshold for a specific region size
static size_t humongous_threshold_for(size_t region_size) {
return (region_size / 2);
}
// Returns the number of regions the humongous object of the given word size
// requires.
static size_t humongous_obj_size_in_regions(size_t word_size);
// Print the maximum heap capacity.
virtual size_t max_capacity() const;
virtual jlong millis_since_last_gc();
// 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
const G1SurvivorRegions* survivor() const { return &_survivor; }
uint survivor_regions_count() const {
return _survivor.length();
}
uint eden_regions_count() const {
return _eden.length();
}
uint young_regions_count() const {
return _eden.length() + _survivor.length();
}
uint old_regions_count() const { return _old_set.length(); }
uint humongous_regions_count() const { return _humongous_set.length(); }
#ifdef ASSERT
bool check_young_list_empty();
#endif
// *** 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 do_concurrent_mark();
bool is_marked_next(oop obj) const;
// 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, b) it
// is not marked, and c) it is not in an archive region.
bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
return
hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
!hr->is_archive();
}
// This function returns true when an object has been
// around since the previous marking and hasn't yet
// been marked during this marking, and is not in an archive region.
bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
return
!hr->obj_allocated_since_next_marking(obj) &&
!is_marked_next(obj) &&
!hr->is_archive();
}
// 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 NULL it isn't dead.
inline bool is_obj_dead(const oop obj) const;
inline bool is_obj_ill(const oop obj) const;
inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
inline bool is_obj_dead_full(const oop obj) const;
G1ConcurrentMark* concurrent_mark() const { return _cm; }
// Refinement
G1ConcurrentRefine* concurrent_refine() const { return _cr; }
// Optimized nmethod scanning support routines
// Is an oop scavengeable
virtual bool is_scavengable(oop obj);
// Register the given nmethod with the G1 heap.
virtual void register_nmethod(nmethod* nm);
// Unregister the given nmethod from the G1 heap.
virtual void unregister_nmethod(nmethod* nm);
// Free up superfluous code root memory.
void purge_code_root_memory();
// Rebuild the strong code root lists for each region
// after a full GC.
void rebuild_strong_code_roots();
// Partial cleaning used when class unloading is disabled.
// Let the caller choose what structures to clean out:
// - StringTable
// - SymbolTable
// - StringDeduplication structures
void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
// Complete cleaning used when class unloading is enabled.
// Cleans out all structures handled by partial_cleaning and also the CodeCache.
void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
// Redirty logged cards in the refinement queue.
void redirty_logged_cards();
// Verification
// 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 == UseFullMarking -> use "next" marking bitmap but no TAMS
//
// 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 == UseFullMarking, which is to verify the marking during a
// full GC.
void verify(VerifyOption vo);
// WhiteBox testing support.
virtual bool supports_concurrent_phase_control() const;
virtual const char* const* concurrent_phases() const;
virtual bool request_concurrent_phase(const char* phase);
// The methods below are here for convenience and dispatch the
// appropriate method depending on value of the given VerifyOption
// parameter. The values for that parameter, and their meanings,
// are the same as those above.
bool is_obj_dead_cond(const oop obj,
const HeapRegion* hr,
const VerifyOption vo) const;
bool is_obj_dead_cond(const oop obj,
const VerifyOption vo) const;
G1HeapSummary create_g1_heap_summary();
G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
// Printing
private:
void print_heap_regions() const;
void print_regions_on(outputStream* st) const;
public:
virtual void print_on(outputStream* st) const;
virtual void print_extended_on(outputStream* st) const;
virtual void print_on_error(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;
public:
size_t pending_card_num();
private:
size_t _max_heap_capacity;
};
class G1ParEvacuateFollowersClosure : public VoidClosure {
private:
double _start_term;
double _term_time;
size_t _term_attempts;
void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
protected:
G1CollectedHeap* _g1h;
G1ParScanThreadState* _par_scan_state;
RefToScanQueueSet* _queues;
ParallelTaskTerminator* _terminator;
G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
RefToScanQueueSet* queues() { return _queues; }
ParallelTaskTerminator* terminator() { return _terminator; }
public:
G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
G1ParScanThreadState* par_scan_state,
RefToScanQueueSet* queues,
ParallelTaskTerminator* terminator)
: _g1h(g1h), _par_scan_state(par_scan_state),
_queues(queues), _terminator(terminator),
_start_term(0.0), _term_time(0.0), _term_attempts(0) {}
void do_void();
double term_time() const { return _term_time; }
size_t term_attempts() const { return _term_attempts; }
private:
inline bool offer_termination();
};
#endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP