/* * Copyright (c) 2001, 2026, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_GC_G1_G1COLLECTEDHEAP_HPP #define SHARE_GC_G1_G1COLLECTEDHEAP_HPP #include "gc/g1/g1BarrierSet.hpp" #include "gc/g1/g1BiasedArray.hpp" #include "gc/g1/g1CardSet.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/g1EvacStats.hpp" #include "gc/g1/g1HeapRegionAttr.hpp" #include "gc/g1/g1HeapRegionManager.hpp" #include "gc/g1/g1HeapRegionSet.hpp" #include "gc/g1/g1HeapTransition.hpp" #include "gc/g1/g1HeapVerifier.hpp" #include "gc/g1/g1MonitoringSupport.hpp" #include "gc/g1/g1MonotonicArenaFreeMemoryTask.hpp" #include "gc/g1/g1MonotonicArenaFreePool.hpp" #include "gc/g1/g1NUMA.hpp" #include "gc/g1/g1SurvivorRegions.hpp" #include "gc/g1/g1YoungGCAllocationFailureInjector.hpp" #include "gc/shared/barrierSet.hpp" #include "gc/shared/collectedHeap.hpp" #include "gc/shared/gcHeapSummary.hpp" #include "gc/shared/plab.hpp" #include "gc/shared/taskqueue.hpp" #include "memory/allocation.hpp" #include "memory/iterator.hpp" #include "memory/memRegion.hpp" #include "runtime/atomic.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/threadSMR.hpp" #include "utilities/bitMap.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 G1Allocator; class G1BatchedTask; class G1CardTableEntryClosure; class G1ConcurrentMark; class G1ConcurrentMarkThread; class G1ConcurrentRefine; class G1GCCounters; class G1GCPhaseTimes; class G1HeapSizingPolicy; class G1NewTracer; class G1RemSet; class G1ReviseYoungLengthTask; class G1ServiceTask; class G1ServiceThread; class GCMemoryManager; class G1HeapRegion; class MemoryPool; class nmethod; class PartialArrayStateManager; class ReferenceProcessor; class STWGCTimer; class WorkerThreads; typedef OverflowTaskQueue G1ScannerTasksQueue; typedef GenericTaskQueueSet G1ScannerTasksQueueSet; typedef int RegionIdx_t; // needs to hold [ 0..max_num_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) override; }; class G1STWSubjectToDiscoveryClosure : public BoolObjectClosure { G1CollectedHeap* _g1h; public: G1STWSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) {} bool do_object_b(oop p) override; }; class G1RegionMappingChangedListener : public G1MappingChangedListener { private: void reset_from_card_cache(uint start_idx, size_t num_regions); public: void on_commit(uint start_idx, size_t num_regions, bool zero_filled) override; }; // Helper to claim contiguous sets of JavaThread for processing by multiple threads. class G1JavaThreadsListClaimer : public StackObj { ThreadsListHandle _list; uint _claim_step; Atomic _cur_claim; // Attempts to claim _claim_step JavaThreads, returning an array of claimed // JavaThread* with count elements. Returns null (and a zero count) if there // are no more threads to claim. JavaThread* const* claim(uint& count); public: G1JavaThreadsListClaimer(uint claim_step) : _list(), _claim_step(claim_step), _cur_claim(0) { assert(claim_step > 0, "must be"); } // Executes the given closure on the elements of the JavaThread list, chunking the // JavaThread set in claim_step chunks for each caller to reduce parallelization // overhead. void apply(ThreadClosure* cl); // Total number of JavaThreads that can be claimed. uint length() const { return _list.length(); } }; class G1CollectedHeap : public CollectedHeap { friend class VM_G1CollectForAllocation; friend class VM_G1CollectFull; friend class VM_G1TryInitiateConcMark; friend class VMStructs; friend class MutatorAllocRegion; friend class G1FullCollector; friend class G1GCAllocRegion; friend class G1HeapVerifier; friend class G1YoungGCVerifierMark; // Closures used in implementation. friend class G1EvacuateRegionsTask; friend class G1PLABAllocator; // Other related classes. friend class G1HeapPrinterMark; friend class G1HeapRegionClaimer; // Testing classes. friend class G1CheckRegionAttrTableClosure; private: // GC Overhead Limit functionality related members. // // The goal is to return null for allocations prematurely (before really going // OOME) in case both GC CPU usage (>= GCTimeLimit) and not much available free // memory (<= GCHeapFreeLimit) so that applications can exit gracefully or try // to keep running by easing off memory. uintx _gc_overhead_counter; // The number of consecutive garbage collections we were over the limits. void update_gc_overhead_counter(); bool gc_overhead_limit_exceeded(); G1ServiceThread* _service_thread; G1ServiceTask* _periodic_gc_task; G1MonotonicArenaFreeMemoryTask* _free_arena_memory_task; G1ReviseYoungLengthTask* _revise_young_length_task; WorkerThreads* _workers; // The current epoch for refinement, i.e. the number of times the card tables // have been swapped by a garbage collection. // Used for detecting whether concurrent refinement has been interrupted by a // garbage collection. size_t _refinement_epoch; // The following members are for tracking safepoint durations between garbage // collections. jlong _last_synchronized_start; jlong _last_refinement_epoch_start; jlong _yield_duration_in_refinement_epoch; // Time spent in safepoints since beginning of last refinement epoch. size_t _last_safepoint_refinement_epoch; // Refinement epoch before last safepoint. Ticks _collection_pause_end; static size_t _humongous_object_threshold_in_words; // These sets keep track of old and humongous regions respectively. G1HeapRegionSet _old_set; G1HeapRegionSet _humongous_set; // Young gen memory statistics before GC. G1MonotonicArenaMemoryStats _young_gen_card_set_stats; // Collection set candidates memory statistics after GC. G1MonotonicArenaMemoryStats _collection_set_candidates_card_set_stats; // The block offset table for the G1 heap. G1BlockOffsetTable* _bot; public: void rebuild_free_region_list(); // Start a new incremental collection set for the next pause. void start_new_collection_set(); void prepare_region_for_full_compaction(G1HeapRegion* hr); private: // 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 free list. void rebuild_region_sets(bool free_list_only); // Callback for region mapping changed events. G1RegionMappingChangedListener _listener; // Handle G1 NUMA support. G1NUMA* _numa; // The sequence of all heap regions in the heap. G1HeapRegionManager _hrm; // Manages all allocations with regions except humongous object allocations. G1Allocator* _allocator; G1YoungGCAllocationFailureInjector _allocation_failure_injector; // 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). volatile size_t _summary_bytes_used; void increase_used(size_t bytes); void decrease_used(size_t bytes); void set_used(size_t bytes); // Number of bytes used in all regions during GC. Typically changed when // retiring a GC alloc region. size_t _bytes_used_during_gc; public: size_t bytes_used_during_gc() const { return _bytes_used_during_gc; } private: // GC allocation statistics policy for survivors. G1EvacStats _survivor_evac_stats; // GC allocation statistics policy for tenured objects. G1EvacStats _old_evac_stats; // Helper for monitoring and management support. G1MonitoringSupport* _monitoring_support; uint _num_humongous_objects; // Current amount of (all) humongous objects found in the heap. uint _num_humongous_reclaim_candidates; // Number of humongous object eager reclaim candidates. public: uint num_humongous_objects() const { return _num_humongous_objects; } uint num_humongous_reclaim_candidates() const { return _num_humongous_reclaim_candidates; } bool has_humongous_reclaim_candidates() const { return _num_humongous_reclaim_candidates > 0; } void set_humongous_stats(uint num_humongous_total, uint num_humongous_candidates); bool should_sample_collection_set_candidates() const; void set_collection_set_candidates_stats(G1MonotonicArenaMemoryStats& stats); void set_young_gen_card_set_stats(const G1MonotonicArenaMemoryStats& stats); void update_perf_counter_cpu_time(); private: // Return true if an explicit GC should start a concurrent cycle instead // of doing a STW full GC. A concurrent cycle should be started if: // (a) cause == _g1_humongous_allocation, // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent, // (c) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent, // (d) cause == _wb_breakpoint, // (e) cause == _g1_periodic_collection and +G1PeriodicGCInvokesConcurrent. bool should_do_concurrent_full_gc(GCCause::Cause cause); // Wait until a full mark (either currently in progress or one that completed // after the current request) has finished. Returns whether that full mark started // after this request. If so, we typically do not need another one. bool wait_full_mark_finished(GCCause::Cause cause, uint old_marking_started_before, uint old_marking_started_after, uint old_marking_completed_after); // Attempt to start a concurrent cycle with the indicated cause, for potentially // allocating allocation_word_size words. // precondition: should_do_concurrent_full_gc(cause) bool try_collect_concurrently(size_t allocation_word_size, GCCause::Cause cause, uint gc_counter, uint old_marking_started_before); // 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; // 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) override; // 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() != nullptr, "no current thread"); \ assert(Thread::current()->is_VM_thread(), "current thread is not VM thread"); \ } while (0) #ifdef ASSERT #define assert_used_and_recalculate_used_equal(g1h) \ do { \ size_t cur_used_bytes = g1h->used(); \ size_t recal_used_bytes = g1h->recalculate_used(); \ assert(cur_used_bytes == recal_used_bytes, "Used(%zu) is not" \ " same as recalculated used(%zu).", \ cur_used_bytes, recal_used_bytes); \ } while (0) #else #define assert_used_and_recalculate_used_equal(g1h) do {} while(0) #endif // The young region list. G1EdenRegions _eden; G1SurvivorRegions _survivor; STWGCTimer* _gc_timer_stw; G1NewTracer* _gc_tracer_stw; // The current policy object for the collector. G1Policy* _policy; G1HeapSizingPolicy* _heap_sizing_policy; G1CollectionSet _collection_set; // Try to allocate a single non-humongous G1HeapRegion 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. 'type' takes the type of region to be allocated. (Use constants // Old, Eden, Humongous, Survivor defined in G1HeapRegionType.) G1HeapRegion* new_region(size_t word_size, G1HeapRegionType type, bool do_expand, uint node_index = G1NUMA::AnyNodeIndex); // 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(G1HeapRegion* first_hr, 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, (only) mem_allocate() will attempt to do an evacuation // pause and retry the allocation. Allocate_new_tlab() will return null, // deferring to the following mem_allocate(). // // * 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 in a special path. HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) override; HeapWord* mem_allocate(size_t word_size) override; // 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, bool allow_gc); // Second-level mutator allocation attempt: take the Heap_lock and // retry the allocation attempt, potentially scheduling a GC // pause if allow_gc is set. This should only be used for non-humongous // allocations. HeapWord* attempt_allocation_slow(uint node_index, size_t word_size, bool allow_gc); // 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. G1HeapRegion* new_mutator_alloc_region(size_t word_size, uint node_index); void retire_mutator_alloc_region(G1HeapRegion* alloc_region, size_t allocated_bytes); // For GC alloc regions. bool has_more_regions(G1HeapRegionAttr dest); G1HeapRegion* new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index); void retire_gc_alloc_region(G1HeapRegion* alloc_region, size_t allocated_bytes, G1HeapRegionAttr dest); void resize_heap(size_t resize_bytes, bool should_expand); // - if clear_all_soft_refs is true, all soft references should be // cleared during the GC. // - if do_maximal_compaction is true, full gc will do a maximally // compacting collection, leaving no dead wood. // - if allocation_word_size is set, then this allocation size will // be accounted for in case shrinking of the heap happens. // - it returns false if it is unable to do the collection due to the // GC locker being active, true otherwise. void do_full_collection(size_t allocation_word_size, bool clear_all_soft_refs, bool do_maximal_compaction); // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. void do_full_collection(bool clear_all_soft_refs) override; // Helper to do a full collection that clears soft references. void upgrade_to_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); // Internal helpers used during full GC to split it up to // increase readability. bool abort_concurrent_cycle(); void verify_before_full_collection(); void prepare_heap_for_full_collection(); void prepare_for_mutator_after_full_collection(size_t allocation_word_size); void abort_refinement(); void verify_after_full_collection(); void print_heap_after_full_collection(); // Helper method for satisfy_failed_allocation() HeapWord* satisfy_failed_allocation_helper(size_t word_size, bool do_gc, bool maximal_compaction, bool expect_null_mutator_alloc_region); // 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); void verify_numa_regions(const char* desc); public: // If during a concurrent start pause we may install a pending list head which is not // otherwise reachable, ensure that it is marked in the bitmap for concurrent marking // to discover. void make_pending_list_reachable(); G1ServiceThread* service_thread() const { return _service_thread; } WorkerThreads* workers() const { return _workers; } // Run the given batch task using the workers. void run_batch_task(G1BatchedTask* cl); // Return "optimal" number of chunks per region we want to use for claiming areas // within a region to claim during card table scanning. // The returned value is a trade-off between granularity of work distribution and // memory usage and maintenance costs of that table. // Testing showed that 64 for 1M/2M region, 128 for 4M/8M regions, 256 for 16/32M regions, // and so on seems to be such a good trade-off. static uint get_chunks_per_region_for_scan(); // Return "optimal" number of chunks per region we want to use for claiming areas // within a region to claim during card table merging. // This is much smaller than for scanning as the merge work is much smaller. // Currently 1 for 1M regions, 2 for 2/4M regions, 4 for 8/16M regions and so on. static uint get_chunks_per_region_for_merge(); G1Allocator* allocator() { return _allocator; } G1YoungGCAllocationFailureInjector* allocation_failure_injector() { return &_allocation_failure_injector; } G1HeapVerifier* verifier() { return _verifier; } G1MonitoringSupport* monitoring_support() { assert(_monitoring_support != nullptr, "should have been initialized"); return _monitoring_support; } void pin_object(JavaThread* thread, oop obj) override; void unpin_object(JavaThread* thread, oop obj) override; void resize_heap_after_young_collection(size_t allocation_word_size); void resize_heap_after_full_collection(size_t allocation_word_size); // Check if there is memory to uncommit and if so schedule a task to do it. void uncommit_regions_if_necessary(); // Immediately uncommit uncommittable regions. uint uncommit_regions(uint region_limit); bool has_uncommittable_regions(); G1NUMA* numa() const { return _numa; } // 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 G1HeapRegion boundary.) bool expand(size_t expand_bytes, WorkerThreads* pretouch_workers); bool expand_single_region(uint node_index); // Returns the PLAB statistics for a given destination. inline G1EvacStats* alloc_buffer_stats(G1HeapRegionAttr dest); // Determines PLAB size for a given destination. inline size_t desired_plab_sz(G1HeapRegionAttr dest); // Clamp the given PLAB word size to allowed values. Prevents humongous PLAB sizes // for two reasons: // * PLABs are allocated using a similar paths as oops, but should // never be in a humongous region // * Allowing humongous PLABs needlessly churns the region free lists inline size_t clamp_plab_size(size_t value) const; // Do anything common to GC's. void gc_prologue(bool full); void gc_epilogue(bool full); // Can concurrent mark process this object immediately, i.e. mark as live without the need // of pushing it on the mark stack (to process references)? // Used to keep objects that are potentially eagerly reclaimed out of the mark stack. // Its klass may still need to be handled. inline bool can_be_marked_through_immediately(oop obj) const; // Does the given region fulfill remembered set based eager reclaim candidate requirements? bool is_potential_eager_reclaim_candidate(G1HeapRegion* r) const; 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_candidate_region_with_region_attr(uint index); void set_humongous_metadata(G1HeapRegion* first_hr, uint num_regions, size_t word_size, bool update_remsets); // The following methods update the region attribute table, i.e. a compact // representation of per-region information that is regularly accessed // during GC. inline void register_young_region_with_region_attr(G1HeapRegion* r); inline void register_new_survivor_region_with_region_attr(G1HeapRegion* r); inline void register_old_collection_set_region_with_region_attr(G1HeapRegion* r); inline void register_optional_region_with_region_attr(G1HeapRegion* r); // Updates region state without overwriting the type in the region attribute table. inline void update_region_attr(G1HeapRegion* r); void clear_region_attr(const G1HeapRegion* hr) { _region_attr.clear(hr); } void clear_region_attr() { _region_attr.clear(); } // Verify that the G1RegionAttr remset tracking corresponds to actual remset tracking // for all regions. void verify_region_attr_is_remset_tracked() PRODUCT_RETURN; void clear_bitmap_for_region(G1HeapRegion* hr); 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 G1OldGCCount_lock in case a Java thread is waiting for a full // GC to happen (e.g., it called System.gc() with // +ExplicitGCInvokesConcurrent). // whole_heap_examined should indicate that during that old marking // cycle the whole heap has been examined for live objects (as opposed // to only parts, or aborted before completion). void increment_old_marking_cycles_completed(bool concurrent, bool whole_heap_examined); uint old_marking_cycles_started() const { return _old_marking_cycles_started; } uint old_marking_cycles_completed() const { return _old_marking_cycles_completed; } // Allocates a new heap region instance. G1HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); // Frees a region by resetting its metadata and adding it to the free list // passed as a parameter (this is usually a local list which will be appended // to the master free list later or null if free list management is handled // in another way). // Callers must ensure they are the only one calling free on the given region // at the same time. void free_region(G1HeapRegion* hr, G1FreeRegionList* free_list); // Add the given region to the retained regions collection set candidates. void retain_region(G1HeapRegion* hr); // 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(G1HeapRegion* hr, G1FreeRegionList* free_list); // Execute func(G1HeapRegion* r, bool is_last) on every region covered by the // given range. template void iterate_regions_in_range(MemRegion range, const Func& func); // Commit the required number of G1 region(s) according to the size requested // and mark them as 'old' region(s). // This API is only used for allocating heap space for the archived heap objects // in the CDS archive. HeapWord* alloc_archive_region(size_t word_size); // Populate the G1BlockOffsetTable for archived regions with the given // memory range. void populate_archive_regions_bot(MemRegion range); // For the specified range, uncommit the containing G1 regions // which had been allocated by alloc_archive_regions. This should be called // at JVM init time if the archive heap's contents cannot be used (e.g., if // CRC check fails). void dealloc_archive_regions(MemRegion range); private: // Shrink the garbage-first heap by at most the given size (in bytes!). // (Rounds down to a G1HeapRegion boundary.) void shrink(size_t shrink_bytes); void shrink_helper(size_t expand_bytes); // 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); // Perform an incremental collection at a safepoint, possibly followed by a // by-policy upgrade to a full collection. // The collection should expect to be followed by an allocation of allocation_word_size. // precondition: at safepoint on VM thread // precondition: !is_stw_gc_active() void do_collection_pause_at_safepoint(size_t allocation_word_size); void verify_before_young_collection(G1HeapVerifier::G1VerifyType type); void verify_after_young_collection(G1HeapVerifier::G1VerifyType type); public: // Start a concurrent cycle. void start_concurrent_cycle(bool concurrent_operation_is_full_mark); void prepare_for_mutator_after_young_collection(); void retire_tlabs(); // Update all region's pin counts from the per-thread caches and resets them. // Must be called before any decision based on pin counts. void flush_region_pin_cache(); void record_obj_copy_mem_stats(); private: // The g1 remembered set of the heap. G1RemSet* _rem_set; // Global card set configuration G1CardSetConfiguration _card_set_config; G1MonotonicArenaFreePool _card_set_freelist_pool; // Group cardsets G1CSetCandidateGroup _young_regions_cset_group; public: G1CardSetConfiguration* card_set_config() { return &_card_set_config; } G1CSetCandidateGroup* young_regions_cset_group() { return &_young_regions_cset_group; } // After a collection pause, reset eden and the collection set. void clear_eden(); void clear_collection_set(); // Abandon the current collection set without recording policy // statistics or updating free lists. void abandon_collection_set(); // The concurrent marker (and the thread it runs in.) G1ConcurrentMark* _cm; // The concurrent refiner. G1ConcurrentRefine* _cr; // Reusable parallel task queues and partial array manager. G1ScannerTasksQueueSet* _task_queues; PartialArrayStateManager* _partial_array_state_manager; // ("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. Discovery is enabled/disabled // at the start/end of a concurrent marking cycle. // // The other (_ref_processor_stw) handles reference object discovery and // processing during incremental evacuation pauses and full GC pauses. // // ## Incremental evacuation pauses // // STW ref processor discovery is enabled/disabled at the start/end of an // incremental evacuation pause. No particular handling of the CM ref // processor is needed, apart from treating the discovered references as // roots; CM discovery does not need to be temporarily disabled as all // marking threads are paused during incremental evacuation pauses. // // ## Full GC pauses // // We abort any ongoing concurrent marking cycle, disable CM discovery, and // temporarily substitute a new closure for the STW ref processor's // _is_alive_non_header field (old value is restored after the full GC). Then // STW ref processor discovery is enabled, and marking & compaction // commences. // 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: G1ScannerTasksQueueSet* task_queues() const; G1ScannerTasksQueue* task_queue(uint i) const; PartialArrayStateManager* partial_array_state_manager() const; // Create a G1CollectedHeap. // Must call the initialize method afterwards. // May not return if something goes wrong. G1CollectedHeap(); private: jint initialize_concurrent_refinement(); jint initialize_service_thread(); void print_tracing_info() const override; void stop() override; public: // Initialize the G1CollectedHeap to have the initial and // maximum sizes and remembered and barrier sets // specified by the policy object. jint initialize() override; void safepoint_synchronize_begin() override; void safepoint_synchronize_end() override; jlong last_refinement_epoch_start() const { return _last_refinement_epoch_start; } void set_last_refinement_epoch_start(jlong epoch_start, jlong last_yield_duration); jlong yield_duration_in_refinement_epoch(); // Does operations required after initialization has been done. void post_initialize() override; // Initialize weak reference processing. void ref_processing_init(); Name kind() const override { return CollectedHeap::G1; } const char* name() const override { return "G1"; } const G1CollectorState* collector_state() const { return &_collector_state; } G1CollectorState* collector_state() { return &_collector_state; } // The current policy object for the collector. G1Policy* policy() const { return _policy; } // The remembered set. G1RemSet* rem_set() const { return _rem_set; } const G1MonotonicArenaFreePool* card_set_freelist_pool() const { return &_card_set_freelist_pool; } G1MonotonicArenaFreePool* card_set_freelist_pool() { return &_card_set_freelist_pool; } inline G1GCPhaseTimes* phase_times() const; const G1CollectionSet* collection_set() const { return &_collection_set; } G1CollectionSet* collection_set() { return &_collection_set; } inline bool is_collection_set_candidate(const G1HeapRegion* r) const; void initialize_serviceability() override; MemoryUsage memory_usage() override; GrowableArray memory_managers() override; GrowableArray memory_pools() override; void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap) override; static void start_codecache_marking_cycle_if_inactive(bool concurrent_mark_start); static void finish_codecache_marking_cycle(); // 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; } STWGCTimer* gc_timer_stw() const { return _gc_timer_stw; } // The Concurrent Marking reference processor... ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } size_t unused_committed_regions_in_bytes() const; size_t capacity() const override; size_t used() const override; // 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. // Returns true if an incremental GC should be upgrade to a full gc. This // is done when there are no free regions and the heap can't be expanded. bool should_upgrade_to_full_gc() const { return num_available_regions() == 0; } // The number of inactive regions. uint num_inactive_regions() const { return _hrm.num_inactive_regions(); } // The current number of regions in the heap. uint num_committed_regions() const { return _hrm.num_committed_regions(); } // The max number of regions reserved for the heap. uint max_num_regions() const { return _hrm.max_num_regions(); } // The number of regions that are completely free. uint num_free_regions() const { return _hrm.num_free_regions(); } // The number of regions that are not completely free. uint num_used_regions() const { return _hrm.num_used_regions(); } // The number of regions that can be allocated into. uint num_available_regions() const { return num_free_regions() + num_inactive_regions(); } MemoryUsage get_auxiliary_data_memory_usage() const { return _hrm.get_auxiliary_data_memory_usage(); } #ifdef ASSERT bool is_on_master_free_list(G1HeapRegion* hr) { return _hrm.is_free(hr); } #endif // ASSERT inline void old_set_add(G1HeapRegion* hr); inline void old_set_remove(G1HeapRegion* hr); // Returns how much memory there is assigned to non-young heap that can not be // allocated into any more without garbage collection after a hypothetical // allocation of allocation_word_size. size_t non_young_occupancy_after_allocation(size_t allocation_word_size) const; // Determine whether the given region is one that we are using as an // old GC alloc region. bool is_old_gc_alloc_region(G1HeapRegion* hr); void collect(GCCause::Cause cause) override; // Try to perform a collection of the heap with the given cause to allocate allocation_word_size // words. // Returns whether this collection actually executed. bool try_collect(size_t allocation_word_size, GCCause::Cause cause, const G1GCCounters& counters_before); void start_concurrent_gc_for_metadata_allocation(GCCause::Cause gc_cause); bool last_gc_was_periodic() { return _gc_lastcause == GCCause::_g1_periodic_collection; } void remove_from_old_gen_sets(const uint old_regions_removed, const uint humongous_regions_removed); void prepend_to_freelist(G1FreeRegionList* list); void decrement_summary_bytes(size_t bytes); bool is_in(const void* p) const override; // 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 G1HeapRegion* hr) const; inline bool is_in_cset(oop obj) const; inline bool is_in_cset(HeapWord* addr) const; inline bool is_in_cset_or_humongous_candidate(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. G1HeapRegionAttrBiasedMappedArray _region_attr; public: inline G1HeapRegionAttr region_attr(const void* obj) const; inline G1HeapRegionAttr region_attr(uint idx) const; MemRegion reserved() const { return _hrm.reserved(); } bool is_in_reserved(const void* addr) const { return reserved().contains(addr); } G1CardTable* card_table() const { return static_cast(G1BarrierSet::g1_barrier_set()->card_table()); } G1CardTable* refinement_table() const { return G1BarrierSet::g1_barrier_set()->refinement_table(); } G1CardTable::CardValue* card_table_base() const { assert(card_table() != nullptr, "must be"); return card_table()->byte_map_base(); } // Iteration functions. void object_iterate_parallel(ObjectClosure* cl, uint worker_id, G1HeapRegionClaimer* claimer); // Iterate over all objects, calling "cl.do_object" on each. void object_iterate(ObjectClosure* cl) override; ParallelObjectIteratorImpl* parallel_object_iterator(uint thread_num) override; // Keep alive an object that was loaded with AS_NO_KEEPALIVE. void keep_alive(oop obj) override; // Iterate over heap regions, in address order, terminating the // iteration early if the "do_heap_region" method returns "true". void heap_region_iterate(G1HeapRegionClosure* blk) const; void heap_region_iterate(G1HeapRegionIndexClosure* blk) const; // Return the region with the given index. It assumes the index is valid. inline G1HeapRegion* region_at(uint index) const; inline G1HeapRegion* region_at_or_null(uint index) const; // Iterate over the regions that the humongous object starting at the given // region and apply the given method with the signature f(G1HeapRegion*) on them. template void humongous_obj_regions_iterate(G1HeapRegion* start, const Func& f); // Calculate the region index of the given address. Given address must be // within the heap. inline uint addr_to_region(const void* 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 G1HeapRegionClaimer to claim the regions before // applying the closure on them. // The _from_worker_offset version uses the G1HeapRegionClaimer 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(G1HeapRegionClosure* cl, G1HeapRegionClaimer* hrclaimer, uint worker_id) const; void heap_region_par_iterate_from_start(G1HeapRegionClosure* cl, G1HeapRegionClaimer* hrclaimer) const; // Iterate over all regions in the collection set in parallel. void collection_set_par_iterate_all(G1HeapRegionClosure* cl, G1HeapRegionClaimer* hr_claimer, uint worker_id); // Iterate over all regions currently in the current collection set. void collection_set_iterate_all(G1HeapRegionClosure* blk); // Iterate over the regions in the current increment of the collection set. // Starts the iteration 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 // to be iterated. // The variant with the G1HeapRegionClaimer guarantees that the closure will be // applied to a particular region exactly once. void collection_set_iterate_increment_from(G1HeapRegionClosure *blk, uint worker_id) { collection_set_iterate_increment_from(blk, nullptr, worker_id); } void collection_set_iterate_increment_from(G1HeapRegionClosure *blk, G1HeapRegionClaimer* hr_claimer, uint worker_id); // Iterate over the array of region indexes, uint regions[length], applying // the given G1HeapRegionClosure on each region. The worker_id will determine where // to start the iteration to allow for more efficient parallel iteration. void par_iterate_regions_array(G1HeapRegionClosure* cl, G1HeapRegionClaimer* hr_claimer, const uint regions[], size_t length, uint worker_id) const; // Returns the G1HeapRegion that contains addr. addr must not be null. inline G1HeapRegion* heap_region_containing(const void* addr) const; // Returns the G1HeapRegion that contains addr, or null if that is an uncommitted // region. addr must not be null. inline G1HeapRegion* heap_region_containing_or_null(const void* addr) const; // A CollectedHeap is divided into a dense sequence of "blocks"; that is, // each address in the (reserved) heap is a member of exactly // one block. The defining characteristic of a block is that it is // possible to find its size, and thus to progress forward to the next // block. (Blocks may be of different sizes.) Thus, blocks may // represent Java objects, or they might be free blocks in a // free-list-based heap (or subheap), as long as the two kinds are // distinguishable and the size of each is determinable. // Returns the address of the start of the "block" that contains the // address "addr". We say "blocks" instead of "object" since some heaps // may not pack objects densely; a chunk may either be an object or a // non-object. HeapWord* block_start(const void* addr) const; // Requires "addr" to be the start of a block, and returns "TRUE" iff // the block is an object. bool block_is_obj(const HeapWord* addr) const; // Section on thread-local allocation buffers (TLABs) // See CollectedHeap for semantics. size_t tlab_capacity() const override; size_t tlab_used() const override; size_t max_tlab_size() const override; size_t unsafe_max_tlab_alloc() const override; inline bool is_in_young(const oop obj) const; inline bool requires_barriers(stackChunkOop obj) const override; // 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); // Returns how much space in bytes an allocation of word_size will use up in the // heap. static size_t allocation_used_bytes(size_t word_size); // Print the maximum heap capacity. size_t max_capacity() const override; size_t min_capacity() const; Tickspan time_since_last_collection() const { return Ticks::now() - _collection_pause_end; } // Convenience function to be used in situations where the heap type can be // asserted to be this type. static G1CollectedHeap* heap() { return named_heap(CollectedHeap::G1); } // add appropriate methods for any other surv rate groups G1SurvivorRegions* survivor() { return &_survivor; } inline uint eden_target_length() const; uint eden_regions_count() const { return _eden.length(); } uint eden_regions_count(uint node_index) const { return _eden.regions_on_node(node_index); } uint survivor_regions_count() const { return _survivor.length(); } uint survivor_regions_count(uint node_index) const { return _survivor.regions_on_node(node_index); } size_t eden_regions_used_bytes() const { return _eden.used_bytes(); } size_t survivor_regions_used_bytes() const { return _survivor.used_bytes(); } 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 bool is_marked(oop obj) const; // Determine if an object is dead, given the object and also // the region to which the object belongs. inline bool is_obj_dead(const oop obj, const G1HeapRegion* hr) const; // 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. // If obj is null it is not dead. inline bool is_obj_dead(const oop obj) const; inline bool is_obj_dead_full(const oop obj, const G1HeapRegion* hr) const; inline bool is_obj_dead_full(const oop obj) const; // Mark the live object that failed evacuation in the bitmap. void mark_evac_failure_object(oop obj) const; G1ConcurrentMark* concurrent_mark() const { return _cm; } // Refinement G1ConcurrentRefine* concurrent_refine() const { return _cr; } // Optimized nmethod scanning support routines // Register the given nmethod with the G1 heap. void register_nmethod(nmethod* nm) override; // Unregister the given nmethod from the G1 heap. void unregister_nmethod(nmethod* nm) override; // No nmethod verification implemented. void verify_nmethod(nmethod* nm) override {} // Recalculate amount of used memory after GC. Must be called after all allocation // has finished. void update_used_after_gc(bool evacuation_failed); // Rebuild the code root lists for each region // after a full GC. void rebuild_code_roots(); // Performs cleaning of data structures after class unloading. void complete_cleaning(bool class_unloading_occurred); void unload_classes_and_code(const char* description, BoolObjectClosure* cl, GCTimer* timer); void bulk_unregister_nmethods(); // Verification // Perform any cleanup actions necessary before allowing a verification. void prepare_for_verify() override; // Perform verification. void verify(VerifyOption vo) override; // WhiteBox testing support. bool supports_concurrent_gc_breakpoints() const override; WorkerThreads* safepoint_workers() override { return _workers; } // 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 G1HeapRegion* 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: void print_heap_on(outputStream* st) const override; void print_extended_on(outputStream* st) const; void print_gc_on(outputStream* st) const override; void gc_threads_do(ThreadClosure* tc) const override; // Used to print information about locations in the hs_err file. bool print_location(outputStream* st, void* addr) const override; }; // Scoped object that performs common pre- and post-gc heap printing operations. class G1HeapPrinterMark : public StackObj { G1CollectedHeap* _g1h; G1HeapTransition _heap_transition; public: G1HeapPrinterMark(G1CollectedHeap* g1h); ~G1HeapPrinterMark(); }; // Scoped object that performs common pre- and post-gc operations related to // JFR events. class G1JFRTracerMark : public StackObj { protected: STWGCTimer* _timer; GCTracer* _tracer; public: G1JFRTracerMark(STWGCTimer* timer, GCTracer* tracer); ~G1JFRTracerMark(); }; #endif // SHARE_GC_G1_G1COLLECTEDHEAP_HPP