/* * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP #include "gc_implementation/g1/concurrentMark.hpp" #include "gc_implementation/g1/g1AllocRegion.hpp" #include "gc_implementation/g1/g1HRPrinter.hpp" #include "gc_implementation/g1/g1RemSet.hpp" #include "gc_implementation/g1/g1MonitoringSupport.hpp" #include "gc_implementation/g1/heapRegionSeq.hpp" #include "gc_implementation/g1/heapRegionSets.hpp" #include "gc_implementation/shared/hSpaceCounters.hpp" #include "gc_implementation/shared/parGCAllocBuffer.hpp" #include "memory/barrierSet.hpp" #include "memory/memRegion.hpp" #include "memory/sharedHeap.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. class HeapRegion; class HRRSCleanupTask; class GenerationSpec; class OopsInHeapRegionClosure; class G1KlassScanClosure; class G1ScanHeapEvacClosure; class ObjectClosure; class SpaceClosure; class CompactibleSpaceClosure; class Space; class G1CollectorPolicy; class GenRemSet; class G1RemSet; class HeapRegionRemSetIterator; class ConcurrentMark; class ConcurrentMarkThread; class ConcurrentG1Refine; class GenerationCounters; typedef OverflowTaskQueue RefToScanQueue; typedef GenericTaskQueueSet RefToScanQueueSet; typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) enum GCAllocPurpose { GCAllocForTenured, GCAllocForSurvived, GCAllocPurposeCount }; class YoungList : public CHeapObj { private: G1CollectedHeap* _g1h; HeapRegion* _head; HeapRegion* _survivor_head; HeapRegion* _survivor_tail; HeapRegion* _curr; uint _length; uint _survivor_length; size_t _last_sampled_rs_lengths; size_t _sampled_rs_lengths; void empty_list(HeapRegion* list); public: YoungList(G1CollectedHeap* g1h); void push_region(HeapRegion* hr); void add_survivor_region(HeapRegion* hr); void empty_list(); bool is_empty() { return _length == 0; } uint length() { return _length; } uint survivor_length() { return _survivor_length; } // Currently we do not keep track of the used byte sum for the // young list and the survivors and it'd be quite a lot of work to // do so. When we'll eventually replace the young list with // instances of HeapRegionLinkedList we'll get that for free. So, // we'll report the more accurate information then. size_t eden_used_bytes() { assert(length() >= survivor_length(), "invariant"); return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes; } size_t survivor_used_bytes() { return (size_t) survivor_length() * HeapRegion::GrainBytes; } void rs_length_sampling_init(); bool rs_length_sampling_more(); void rs_length_sampling_next(); void reset_sampled_info() { _last_sampled_rs_lengths = 0; } size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } // for development purposes void reset_auxilary_lists(); void clear() { _head = NULL; _length = 0; } void clear_survivors() { _survivor_head = NULL; _survivor_tail = NULL; _survivor_length = 0; } HeapRegion* first_region() { return _head; } HeapRegion* first_survivor_region() { return _survivor_head; } HeapRegion* last_survivor_region() { return _survivor_tail; } // debugging bool check_list_well_formed(); bool check_list_empty(bool check_sample = true); void print(); }; class MutatorAllocRegion : public G1AllocRegion { protected: virtual HeapRegion* allocate_new_region(size_t word_size, bool force); virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); public: MutatorAllocRegion() : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { } }; // The G1 STW is alive closure. // An instance is embedded into the G1CH and used as the // (optional) _is_alive_non_header closure in the STW // reference processor. It is also extensively used during // refence processing during STW evacuation pauses. class G1STWIsAliveClosure: public BoolObjectClosure { G1CollectedHeap* _g1; public: G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} bool do_object_b(oop p); }; class SurvivorGCAllocRegion : public G1AllocRegion { protected: virtual HeapRegion* allocate_new_region(size_t word_size, bool force); virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); public: SurvivorGCAllocRegion() : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { } }; class OldGCAllocRegion : public G1AllocRegion { protected: virtual HeapRegion* allocate_new_region(size_t word_size, bool force); virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); public: OldGCAllocRegion() : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { } }; class RefineCardTableEntryClosure; class G1CollectedHeap : public SharedHeap { friend class VM_G1CollectForAllocation; friend class VM_G1CollectFull; friend class VM_G1IncCollectionPause; friend class VMStructs; friend class MutatorAllocRegion; friend class SurvivorGCAllocRegion; friend class OldGCAllocRegion; // Closures used in implementation. template friend class G1ParCopyClosure; friend class G1IsAliveClosure; friend class G1EvacuateFollowersClosure; friend class G1ParScanThreadState; friend class G1ParScanClosureSuper; friend class G1ParEvacuateFollowersClosure; friend class G1ParTask; friend class G1FreeGarbageRegionClosure; friend class RefineCardTableEntryClosure; friend class G1PrepareCompactClosure; friend class RegionSorter; friend class RegionResetter; friend class CountRCClosure; friend class EvacPopObjClosure; friend class G1ParCleanupCTTask; // Other related classes. friend class G1MarkSweep; private: // The one and only G1CollectedHeap, so static functions can find it. static G1CollectedHeap* _g1h; static size_t _humongous_object_threshold_in_words; // Storage for the G1 heap. VirtualSpace _g1_storage; MemRegion _g1_reserved; // The part of _g1_storage that is currently committed. MemRegion _g1_committed; // The master free list. It will satisfy all new region allocations. MasterFreeRegionList _free_list; // The secondary free list which contains regions that have been // freed up during the cleanup process. This will be appended to the // master free list when appropriate. SecondaryFreeRegionList _secondary_free_list; // It keeps track of the old regions. MasterOldRegionSet _old_set; // It keeps track of the humongous regions. MasterHumongousRegionSet _humongous_set; // The number of regions we could create by expansion. uint _expansion_regions; // The block offset table for the G1 heap. G1BlockOffsetSharedArray* _bot_shared; // Tears down the region sets / lists so that they are empty and the // regions on the heap do not belong to a region set / list. The // only exception is the humongous set which we leave unaltered. If // free_list_only is true, it will only tear down the master free // list. It is called before a Full GC (free_list_only == false) or // before heap shrinking (free_list_only == true). void tear_down_region_sets(bool free_list_only); // Rebuilds the region sets / lists so that they are repopulated to // reflect the contents of the heap. The only exception is the // humongous set which was not torn down in the first place. If // free_list_only is true, it will only rebuild the master free // list. It is called after a Full GC (free_list_only == false) or // after heap shrinking (free_list_only == true). void rebuild_region_sets(bool free_list_only); // The sequence of all heap regions in the heap. HeapRegionSeq _hrs; // Alloc region used to satisfy mutator allocation requests. MutatorAllocRegion _mutator_alloc_region; // Alloc region used to satisfy allocation requests by the GC for // survivor objects. SurvivorGCAllocRegion _survivor_gc_alloc_region; // PLAB sizing policy for survivors. PLABStats _survivor_plab_stats; // Alloc region used to satisfy allocation requests by the GC for // old objects. OldGCAllocRegion _old_gc_alloc_region; // PLAB sizing policy for tenured objects. PLABStats _old_plab_stats; PLABStats* stats_for_purpose(GCAllocPurpose purpose) { PLABStats* stats = NULL; switch (purpose) { case GCAllocForSurvived: stats = &_survivor_plab_stats; break; case GCAllocForTenured: stats = &_old_plab_stats; break; default: assert(false, "unrecognized GCAllocPurpose"); } return stats; } // The last old region we allocated to during the last GC. // Typically, it is not full so we should re-use it during the next GC. HeapRegion* _retained_old_gc_alloc_region; // It specifies whether we should attempt to expand the heap after a // region allocation failure. If heap expansion fails we set this to // false so that we don't re-attempt the heap expansion (it's likely // that subsequent expansion attempts will also fail if one fails). // Currently, it is only consulted during GC and it's reset at the // start of each GC. bool _expand_heap_after_alloc_failure; // It resets the mutator alloc region before new allocations can take place. void init_mutator_alloc_region(); // It releases the mutator alloc region. void release_mutator_alloc_region(); // It initializes the GC alloc regions at the start of a GC. void init_gc_alloc_regions(); // It releases the GC alloc regions at the end of a GC. void release_gc_alloc_regions(uint no_of_gc_workers); // It does any cleanup that needs to be done on the GC alloc regions // before a Full GC. void abandon_gc_alloc_regions(); // Helper for monitoring and management support. G1MonitoringSupport* _g1mm; // Determines PLAB size for a particular allocation purpose. size_t desired_plab_sz(GCAllocPurpose purpose); // Outside of GC pauses, the number of bytes used in all regions other // than the current allocation region. size_t _summary_bytes_used; // This is used for a quick test on whether a reference points into // the collection set or not. Basically, we have an array, with one // byte per region, and that byte denotes whether the corresponding // region is in the collection set or not. The entry corresponding // the bottom of the heap, i.e., region 0, is pointed to by // _in_cset_fast_test_base. The _in_cset_fast_test field has been // biased so that it actually points to address 0 of the address // space, to make the test as fast as possible (we can simply shift // the address to address into it, instead of having to subtract the // bottom of the heap from the address before shifting it; basically // it works in the same way the card table works). bool* _in_cset_fast_test; // The allocated array used for the fast test on whether a reference // points into the collection set or not. This field is also used to // free the array. bool* _in_cset_fast_test_base; // The length of the _in_cset_fast_test_base array. uint _in_cset_fast_test_length; volatile unsigned _gc_time_stamp; size_t* _surviving_young_words; G1HRPrinter _hr_printer; void setup_surviving_young_words(); void update_surviving_young_words(size_t* surv_young_words); void cleanup_surviving_young_words(); // It decides whether an explicit GC should start a concurrent cycle // instead of doing a STW GC. Currently, a concurrent cycle is // explicitly started if: // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. // (c) cause == _g1_humongous_allocation bool should_do_concurrent_full_gc(GCCause::Cause cause); // Keeps track of how many "old marking cycles" (i.e., Full GCs or // concurrent cycles) we have started. volatile unsigned int _old_marking_cycles_started; // Keeps track of how many "old marking cycles" (i.e., Full GCs or // concurrent cycles) we have completed. volatile unsigned int _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; // Clear RSets after a compaction. It also resets the GC time stamps. void clear_rsets_post_compaction(); // If the HR printer is active, dump the state of the regions in the // heap after a compaction. void print_hrs_post_compaction(); double verify(bool guard, const char* msg); void verify_before_gc(); void verify_after_gc(); void log_gc_header(); void log_gc_footer(double pause_time_sec); // These are macros so that, if the assert fires, we get the correct // line number, file, etc. #define heap_locking_asserts_err_msg(_extra_message_) \ err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ (_extra_message_), \ BOOL_TO_STR(Heap_lock->owned_by_self()), \ BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ BOOL_TO_STR(Thread::current()->is_VM_thread())) #define assert_heap_locked() \ do { \ assert(Heap_lock->owned_by_self(), \ heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ } while (0) #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ do { \ assert(Heap_lock->owned_by_self() || \ (SafepointSynchronize::is_at_safepoint() && \ ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ "should be at a safepoint")); \ } while (0) #define assert_heap_locked_and_not_at_safepoint() \ do { \ assert(Heap_lock->owned_by_self() && \ !SafepointSynchronize::is_at_safepoint(), \ heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ "should not be at a safepoint")); \ } while (0) #define assert_heap_not_locked() \ do { \ assert(!Heap_lock->owned_by_self(), \ heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ } while (0) #define assert_heap_not_locked_and_not_at_safepoint() \ do { \ assert(!Heap_lock->owned_by_self() && \ !SafepointSynchronize::is_at_safepoint(), \ heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ "should not be at a safepoint")); \ } while (0) #define assert_at_safepoint(_should_be_vm_thread_) \ do { \ assert(SafepointSynchronize::is_at_safepoint() && \ ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ heap_locking_asserts_err_msg("should be at a safepoint")); \ } while (0) #define assert_not_at_safepoint() \ do { \ assert(!SafepointSynchronize::is_at_safepoint(), \ heap_locking_asserts_err_msg("should not be at a safepoint")); \ } while (0) protected: // The young region list. YoungList* _young_list; // The current policy object for the collector. G1CollectorPolicy* _g1_policy; // This is the second level of trying to allocate a new region. If // new_region() didn't find a region on the free_list, this call will // check whether there's anything available on the // secondary_free_list and/or wait for more regions to appear on // that list, if _free_regions_coming is set. HeapRegion* new_region_try_secondary_free_list(); // Try to allocate a single non-humongous HeapRegion sufficient for // an allocation of the given word_size. If do_expand is true, // attempt to expand the heap if necessary to satisfy the allocation // request. HeapRegion* new_region(size_t word_size, bool do_expand); // Attempt to satisfy a humongous allocation request of the given // size by finding a contiguous set of free regions of num_regions // length and remove them from the master free list. Return the // index of the first region or G1_NULL_HRS_INDEX if the search // was unsuccessful. uint humongous_obj_allocate_find_first(uint num_regions, size_t word_size); // Initialize a contiguous set of free regions of length num_regions // and starting at index first so that they appear as a single // humongous region. HeapWord* humongous_obj_allocate_initialize_regions(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 word_size); virtual HeapWord* mem_allocate(size_t word_size, bool* gc_overhead_limit_was_exceeded); // The following three methods take a gc_count_before_ret // parameter which is used to return the GC count if the method // returns NULL. Given that we are required to read the GC count // while holding the Heap_lock, and these paths will take the // Heap_lock at some point, it's easier to get them to read the GC // count while holding the Heap_lock before they return NULL instead // of the caller (namely: mem_allocate()) having to also take the // Heap_lock just to read the GC count. // First-level mutator allocation attempt: try to allocate out of // the mutator alloc region without taking the Heap_lock. This // should only be used for non-humongous allocations. inline HeapWord* attempt_allocation(size_t word_size, unsigned int* gc_count_before_ret, int* gclocker_retry_count_ret); // Second-level mutator allocation attempt: take the Heap_lock and // retry the allocation attempt, potentially scheduling a GC // pause. This should only be used for non-humongous allocations. HeapWord* attempt_allocation_slow(size_t word_size, unsigned int* gc_count_before_ret, int* gclocker_retry_count_ret); // Takes the Heap_lock and attempts a humongous allocation. It can // potentially schedule a GC pause. HeapWord* attempt_allocation_humongous(size_t word_size, unsigned int* gc_count_before_ret, int* gclocker_retry_count_ret); // Allocation attempt that should be called during safepoints (e.g., // at the end of a successful GC). expect_null_mutator_alloc_region // specifies whether the mutator alloc region is expected to be NULL // or not. HeapWord* attempt_allocation_at_safepoint(size_t word_size, bool expect_null_mutator_alloc_region); // It dirties the cards that cover the block so that so that the post // write barrier never queues anything when updating objects on this // block. It is assumed (and in fact we assert) that the block // belongs to a young region. inline void dirty_young_block(HeapWord* start, size_t word_size); // Allocate blocks during garbage collection. Will ensure an // allocation region, either by picking one or expanding the // heap, and then allocate a block of the given size. The block // may not be a humongous - it must fit into a single heap region. HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size); HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, HeapRegion* alloc_region, bool par, size_t word_size); // Ensure that no further allocations can happen in "r", bearing in mind // that parallel threads might be attempting allocations. void par_allocate_remaining_space(HeapRegion* r); // Allocation attempt during GC for a survivor object / PLAB. inline HeapWord* survivor_attempt_allocation(size_t word_size); // Allocation attempt during GC for an old object / PLAB. inline HeapWord* old_attempt_allocation(size_t word_size); // These methods are the "callbacks" from the G1AllocRegion class. // For mutator alloc regions. HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); void retire_mutator_alloc_region(HeapRegion* alloc_region, size_t allocated_bytes); // For GC alloc regions. HeapRegion* new_gc_alloc_region(size_t word_size, uint count, GCAllocPurpose ap); void retire_gc_alloc_region(HeapRegion* alloc_region, size_t allocated_bytes, GCAllocPurpose ap); // - if explicit_gc is true, the GC is for a System.gc() or a heap // inspection request and should collect the entire heap // - if clear_all_soft_refs is true, all soft references should be // cleared during the GC // - if explicit_gc is false, word_size describes the allocation that // the GC should attempt (at least) to satisfy // - it returns false if it is unable to do the collection due to the // GC locker being active, true otherwise bool do_collection(bool explicit_gc, bool clear_all_soft_refs, size_t word_size); // Callback from VM_G1CollectFull operation. // Perform a full collection. virtual void do_full_collection(bool clear_all_soft_refs); // Resize the heap if necessary after a full collection. If this is // after a collect-for allocation, "word_size" is the allocation size, // and will be considered part of the used portion of the heap. void resize_if_necessary_after_full_collection(size_t word_size); // Callback from VM_G1CollectForAllocation operation. // This function does everything necessary/possible to satisfy a // failed allocation request (including collection, expansion, etc.) HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded); // Attempting to expand the heap sufficiently // to support an allocation of the given "word_size". If // successful, perform the allocation and return the address of the // allocated block, or else "NULL". HeapWord* expand_and_allocate(size_t word_size); // Process any reference objects discovered during // an incremental evacuation pause. void process_discovered_references(uint no_of_gc_workers); // Enqueue any remaining discovered references // after processing. void enqueue_discovered_references(uint no_of_gc_workers); public: G1MonitoringSupport* g1mm() { assert(_g1mm != NULL, "should have been initialized"); return _g1mm; } // Expand the garbage-first heap by at least the given size (in bytes!). // Returns true if the heap was expanded by the requested amount; // false otherwise. // (Rounds up to a HeapRegion boundary.) bool expand(size_t expand_bytes); // Do anything common to GC's. virtual void gc_prologue(bool full); virtual void gc_epilogue(bool full); // We register a region with the fast "in collection set" test. We // simply set to true the array slot corresponding to this region. void register_region_with_in_cset_fast_test(HeapRegion* r) { assert(_in_cset_fast_test_base != NULL, "sanity"); assert(r->in_collection_set(), "invariant"); uint index = r->hrs_index(); assert(index < _in_cset_fast_test_length, "invariant"); assert(!_in_cset_fast_test_base[index], "invariant"); _in_cset_fast_test_base[index] = true; } // This is a fast test on whether a reference points into the // collection set or not. It does not assume that the reference // points into the heap; if it doesn't, it will return false. bool in_cset_fast_test(oop obj) { assert(_in_cset_fast_test != NULL, "sanity"); if (_g1_committed.contains((HeapWord*) obj)) { // no need to subtract the bottom of the heap from obj, // _in_cset_fast_test is biased uintx index = (uintx) obj >> HeapRegion::LogOfHRGrainBytes; bool ret = _in_cset_fast_test[index]; // let's make sure the result is consistent with what the slower // test returns assert( ret || !obj_in_cs(obj), "sanity"); assert(!ret || obj_in_cs(obj), "sanity"); return ret; } else { return false; } } void clear_cset_fast_test() { assert(_in_cset_fast_test_base != NULL, "sanity"); memset(_in_cset_fast_test_base, false, (size_t) _in_cset_fast_test_length * sizeof(bool)); } // 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); unsigned int old_marking_cycles_completed() { return _old_marking_cycles_completed; } G1HRPrinter* hr_printer() { return &_hr_printer; } protected: // Shrink the garbage-first heap by at most the given size (in bytes!). // (Rounds down to a HeapRegion boundary.) virtual void shrink(size_t expand_bytes); void shrink_helper(size_t expand_bytes); #if TASKQUEUE_STATS static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; void reset_taskqueue_stats(); #endif // TASKQUEUE_STATS // Schedule the VM operation that will do an evacuation pause to // satisfy an allocation request of word_size. *succeeded will // return whether the VM operation was successful (it did do an // evacuation pause) or not (another thread beat us to it or the GC // locker was active). Given that we should not be holding the // Heap_lock when we enter this method, we will pass the // gc_count_before (i.e., total_collections()) as a parameter since // it has to be read while holding the Heap_lock. Currently, both // methods that call do_collection_pause() release the Heap_lock // before the call, so it's easy to read gc_count_before just before. HeapWord* do_collection_pause(size_t word_size, unsigned int gc_count_before, bool* succeeded); // The guts of the incremental collection pause, executed by the vm // thread. It returns false if it is unable to do the collection due // to the GC locker being active, true otherwise bool do_collection_pause_at_safepoint(double target_pause_time_ms); // Actually do the work of evacuating the collection set. void evacuate_collection_set(); // The g1 remembered set of the heap. G1RemSet* _g1_rem_set; // And it's mod ref barrier set, used to track updates for the above. ModRefBarrierSet* _mr_bs; // A set of cards that cover the objects for which the Rsets should be updated // concurrently after the collection. DirtyCardQueueSet _dirty_card_queue_set; // The closure used to refine a single card. RefineCardTableEntryClosure* _refine_cte_cl; // A function to check the consistency of dirty card logs. void check_ct_logs_at_safepoint(); // A DirtyCardQueueSet that is used to hold cards that contain // references into the current collection set. This is used to // update the remembered sets of the regions in the collection // set in the event of an evacuation failure. DirtyCardQueueSet _into_cset_dirty_card_queue_set; // After a collection pause, make the regions in the CS into free // regions. void free_collection_set(HeapRegion* cs_head); // Abandon the current collection set without recording policy // statistics or updating free lists. void abandon_collection_set(HeapRegion* cs_head); // Applies "scan_non_heap_roots" to roots outside the heap, // "scan_rs" to roots inside the heap (having done "set_region" to // indicate the region in which the root resides), // and does "scan_metadata" If "scan_rs" is // NULL, then this step is skipped. The "worker_i" // param is for use with parallel roots processing, and should be // the "i" of the calling parallel worker thread's work(i) function. // In the sequential case this param will be ignored. void g1_process_strong_roots(bool is_scavenging, ScanningOption so, OopClosure* scan_non_heap_roots, OopsInHeapRegionClosure* scan_rs, G1KlassScanClosure* scan_klasses, uint worker_i); // Apply "blk" to all the weak roots of the system. These include // JNI weak roots, the code cache, system dictionary, symbol table, // string table, and referents of reachable weak refs. void g1_process_weak_roots(OopClosure* root_closure); // Frees a non-humongous region by initializing its contents and // adding it to the free list that's passed as a parameter (this is // usually a local list which will be appended to the master free // list later). The used bytes of freed regions are accumulated in // pre_used. If par is true, the region's RSet will not be freed // up. The assumption is that this will be done later. void free_region(HeapRegion* hr, size_t* pre_used, FreeRegionList* free_list, bool par); // Frees a humongous region by collapsing it into individual regions // and calling free_region() for each of them. The freed regions // will be added to the free list that's passed as a parameter (this // is usually a local list which will be appended to the master free // list later). The used bytes of freed regions are accumulated in // pre_used. If par is true, the region's RSet will not be freed // up. The assumption is that this will be done later. void free_humongous_region(HeapRegion* hr, size_t* pre_used, FreeRegionList* free_list, HumongousRegionSet* humongous_proxy_set, bool par); // Notifies all the necessary spaces that the committed space has // been updated (either expanded or shrunk). It should be called // after _g1_storage is updated. void update_committed_space(HeapWord* old_end, HeapWord* new_end); // The concurrent marker (and the thread it runs in.) ConcurrentMark* _cm; ConcurrentMarkThread* _cmThread; bool _mark_in_progress; // The concurrent refiner. ConcurrentG1Refine* _cg1r; // The parallel task queues RefToScanQueueSet *_task_queues; // True iff a evacuation has failed in the current collection. bool _evacuation_failed; // Set the attribute indicating whether evacuation has failed in the // current collection. void set_evacuation_failed(bool b) { _evacuation_failed = b; } // Failed evacuations cause some logical from-space objects to have // forwarding pointers to themselves. Reset them. void remove_self_forwarding_pointers(); // Together, these store an object with a preserved mark, and its mark value. Stack _objs_with_preserved_marks; Stack _preserved_marks_of_objs; // Preserve the mark of "obj", if necessary, in preparation for its mark // word being overwritten with a self-forwarding-pointer. void preserve_mark_if_necessary(oop obj, markOop m); // The stack of evac-failure objects left to be scanned. GrowableArray* _evac_failure_scan_stack; // The closure to apply to evac-failure objects. OopsInHeapRegionClosure* _evac_failure_closure; // Set the field above. void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { _evac_failure_closure = evac_failure_closure; } // Push "obj" on the scan stack. void push_on_evac_failure_scan_stack(oop obj); // Process scan stack entries until the stack is empty. void drain_evac_failure_scan_stack(); // True iff an invocation of "drain_scan_stack" is in progress; to // prevent unnecessary recursion. bool _drain_in_progress; // Do any necessary initialization for evacuation-failure handling. // "cl" is the closure that will be used to process evac-failure // objects. void init_for_evac_failure(OopsInHeapRegionClosure* cl); // Do any necessary cleanup for evacuation-failure handling data // structures. void finalize_for_evac_failure(); // An attempt to evacuate "obj" has failed; take necessary steps. oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj); void handle_evacuation_failure_common(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 gcs_are_young, bool during_initial_mark, bool during_marking); 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 ocurred. inline void reset_evacuation_should_fail(); #endif // !PRODUCT // ("Weak") Reference processing support. // // G1 has 2 instances of the referece processor class. One // (_ref_processor_cm) handles reference object discovery // and subsequent processing during concurrent marking cycles. // // The other (_ref_processor_stw) handles reference object // discovery and processing during full GCs and incremental // evacuation pauses. // // During an incremental pause, reference discovery will be // temporarily disabled for _ref_processor_cm and will be // enabled for _ref_processor_stw. At the end of the evacuation // pause references discovered by _ref_processor_stw will be // processed and discovery will be disabled. The previous // setting for reference object discovery for _ref_processor_cm // will be re-instated. // // At the start of marking: // * Discovery by the CM ref processor is verified to be inactive // and it's discovered lists are empty. // * Discovery by the CM ref processor is then enabled. // // At the end of marking: // * Any references on the CM ref processor's discovered // lists are processed (possibly MT). // // At the start of full GC we: // * Disable discovery by the CM ref processor and // empty CM ref processor's discovered lists // (without processing any entries). // * Verify that the STW ref processor is inactive and it's // discovered lists are empty. // * Temporarily set STW ref processor discovery as single threaded. // * Temporarily clear the STW ref processor's _is_alive_non_header // field. // * Finally enable discovery by the STW ref processor. // // The STW ref processor is used to record any discovered // references during the full GC. // // At the end of a full GC we: // * Enqueue any reference objects discovered by the STW ref processor // that have non-live referents. This has the side-effect of // making the STW ref processor inactive by disabling discovery. // * Verify that the CM ref processor is still inactive // and no references have been placed on it's discovered // lists (also checked as a precondition during initial marking). // The (stw) reference processor... ReferenceProcessor* _ref_processor_stw; // During reference object discovery, the _is_alive_non_header // closure (if non-null) is applied to the referent object to // determine whether the referent is live. If so then the // reference object does not need to be 'discovered' and can // be treated as a regular oop. This has the benefit of reducing // the number of 'discovered' reference objects that need to // be processed. // // Instance of the is_alive closure for embedding into the // STW reference processor as the _is_alive_non_header field. // Supplying a value for the _is_alive_non_header field is // optional but doing so prevents unnecessary additions to // the discovered lists during reference discovery. G1STWIsAliveClosure _is_alive_closure_stw; // The (concurrent marking) reference processor... ReferenceProcessor* _ref_processor_cm; // Instance of the concurrent mark is_alive closure for embedding // into the Concurrent Marking reference processor as the // _is_alive_non_header field. Supplying a value for the // _is_alive_non_header field is optional but doing so prevents // unnecessary additions to the discovered lists during reference // discovery. G1CMIsAliveClosure _is_alive_closure_cm; // Cache used by G1CollectedHeap::start_cset_region_for_worker(). HeapRegion** _worker_cset_start_region; // Time stamp to validate the regions recorded in the cache // used by G1CollectedHeap::start_cset_region_for_worker(). // The heap region entry for a given worker is valid iff // the associated time stamp value matches the current value // of G1CollectedHeap::_gc_time_stamp. unsigned int* _worker_cset_start_region_time_stamp; enum G1H_process_strong_roots_tasks { G1H_PS_filter_satb_buffers, G1H_PS_refProcessor_oops_do, // Leave this one last. G1H_PS_NumElements }; SubTasksDone* _process_strong_tasks; volatile bool _free_regions_coming; public: SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } void set_refine_cte_cl_concurrency(bool concurrent); RefToScanQueue *task_queue(int i) const; // A set of cards where updates happened during the GC DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } // A DirtyCardQueueSet that is used to hold cards that contain // references into the current collection set. This is used to // update the remembered sets of the regions in the collection // set in the event of an evacuation failure. DirtyCardQueueSet& into_cset_dirty_card_queue_set() { return _into_cset_dirty_card_queue_set; } // Create a G1CollectedHeap with the specified policy. // Must call the initialize method afterwards. // May not return if something goes wrong. G1CollectedHeap(G1CollectorPolicy* policy); // Initialize the G1CollectedHeap to have the initial and // maximum sizes and remembered and barrier sets // specified by the policy object. jint initialize(); // Initialize weak reference processing. virtual void ref_processing_init(); void set_par_threads(uint t) { SharedHeap::set_par_threads(t); // Done in SharedHeap but oddly there are // two _process_strong_tasks's in a G1CollectedHeap // so do it here too. _process_strong_tasks->set_n_threads(t); } // Set _n_par_threads according to a policy TBD. void set_par_threads(); void set_n_termination(int t) { _process_strong_tasks->set_n_threads(t); } virtual CollectedHeap::Name kind() const { return CollectedHeap::G1CollectedHeap; } // The current policy object for the collector. G1CollectorPolicy* g1_policy() const { return _g1_policy; } virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } // Adaptive size policy. No such thing for g1. virtual AdaptiveSizePolicy* size_policy() { return NULL; } // The rem set and barrier set. G1RemSet* g1_rem_set() const { return _g1_rem_set; } ModRefBarrierSet* mr_bs() const { return _mr_bs; } unsigned get_gc_time_stamp() { return _gc_time_stamp; } void reset_gc_time_stamp() { _gc_time_stamp = 0; OrderAccess::fence(); // Clear the cached CSet starting regions and time stamps. // Their validity is dependent on the GC timestamp. clear_cset_start_regions(); } void check_gc_time_stamps() PRODUCT_RETURN; void increment_gc_time_stamp() { ++_gc_time_stamp; OrderAccess::fence(); } // Reset the given region's GC timestamp. If it's starts humongous, // also reset the GC timestamp of its corresponding // continues humongous regions too. void reset_gc_time_stamps(HeapRegion* hr); void iterate_dirty_card_closure(CardTableEntryClosure* cl, DirtyCardQueue* into_cset_dcq, bool concurrent, int worker_i); // The shared block offset table array. G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } // Reference Processing accessors // The STW reference processor.... ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } // The Concurent Marking reference processor... ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } virtual size_t capacity() const; virtual size_t used() const; // This should be called when we're not holding the heap lock. The // result might be a bit inaccurate. size_t used_unlocked() const; size_t recalculate_used() const; // These virtual functions do the actual allocation. // Some heaps may offer a contiguous region for shared non-blocking // allocation, via inlined code (by exporting the address of the top and // end fields defining the extent of the contiguous allocation region.) // But G1CollectedHeap doesn't yet support this. // Return an estimate of the maximum allocation that could be performed // without triggering any collection or expansion activity. In a // generational collector, for example, this is probably the largest // allocation that could be supported (without expansion) in the youngest // generation. It is "unsafe" because no locks are taken; the result // should be treated as an approximation, not a guarantee, for use in // heuristic resizing decisions. virtual size_t unsafe_max_alloc(); virtual bool is_maximal_no_gc() const { return _g1_storage.uncommitted_size() == 0; } // The total number of regions in the heap. uint n_regions() { return _hrs.length(); } // The max number of regions in the heap. uint max_regions() { return _hrs.max_length(); } // The number of regions that are completely free. uint free_regions() { return _free_list.length(); } // The number of regions that are not completely free. uint used_regions() { return n_regions() - free_regions(); } // The number of regions available for "regular" expansion. uint expansion_regions() { return _expansion_regions; } // Factory method for HeapRegion instances. It will return NULL if // the allocation fails. HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom); void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; void verify_dirty_young_regions() PRODUCT_RETURN; // verify_region_sets() performs verification over the region // lists. It will be compiled in the product code to be used when // necessary (i.e., during heap verification). void verify_region_sets(); // verify_region_sets_optional() is planted in the code for // list verification in non-product builds (and it can be enabled in // product builds by definning HEAP_REGION_SET_FORCE_VERIFY to be 1). #if HEAP_REGION_SET_FORCE_VERIFY void verify_region_sets_optional() { verify_region_sets(); } #else // HEAP_REGION_SET_FORCE_VERIFY void verify_region_sets_optional() { } #endif // HEAP_REGION_SET_FORCE_VERIFY #ifdef ASSERT bool is_on_master_free_list(HeapRegion* hr) { return hr->containing_set() == &_free_list; } bool is_in_humongous_set(HeapRegion* hr) { return hr->containing_set() == &_humongous_set; } #endif // ASSERT // Wrapper for the region list operations that can be called from // methods outside this class. void secondary_free_list_add_as_tail(FreeRegionList* list) { _secondary_free_list.add_as_tail(list); } void append_secondary_free_list() { _free_list.add_as_head(&_secondary_free_list); } void append_secondary_free_list_if_not_empty_with_lock() { // If the secondary free list looks empty there's no reason to // take the lock and then try to append it. if (!_secondary_free_list.is_empty()) { MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); append_secondary_free_list(); } } void old_set_remove(HeapRegion* hr) { _old_set.remove(hr); } size_t non_young_capacity_bytes() { return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); } void set_free_regions_coming(); void reset_free_regions_coming(); bool free_regions_coming() { return _free_regions_coming; } void wait_while_free_regions_coming(); // 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) { return hr == _retained_old_gc_alloc_region; } // Perform a collection of the heap; intended for use in implementing // "System.gc". This probably implies as full a collection as the // "CollectedHeap" supports. virtual void collect(GCCause::Cause cause); // The same as above but assume that the caller holds the Heap_lock. void collect_locked(GCCause::Cause cause); // True iff a evacuation has failed in the most-recent collection. bool evacuation_failed() { return _evacuation_failed; } // It will free a region if it has allocated objects in it that are // all dead. It calls either free_region() or // free_humongous_region() depending on the type of the region that // is passed to it. void free_region_if_empty(HeapRegion* hr, size_t* pre_used, FreeRegionList* free_list, OldRegionSet* old_proxy_set, HumongousRegionSet* humongous_proxy_set, HRRSCleanupTask* hrrs_cleanup_task, bool par); // It appends the free list to the master free list and updates the // master humongous list according to the contents of the proxy // list. It also adjusts the total used bytes according to pre_used // (if par is true, it will do so by taking the ParGCRareEvent_lock). void update_sets_after_freeing_regions(size_t pre_used, FreeRegionList* free_list, OldRegionSet* old_proxy_set, HumongousRegionSet* humongous_proxy_set, bool par); // Returns "TRUE" iff "p" points into the committed areas of the heap. virtual bool is_in(const void* p) const; // Return "TRUE" iff the given object address is within the collection // set. inline bool obj_in_cs(oop obj); // Return "TRUE" iff the given object address is in the reserved // region of g1. bool is_in_g1_reserved(const void* p) const { return _g1_reserved.contains(p); } // Returns a MemRegion that corresponds to the space that has been // reserved for the heap MemRegion g1_reserved() { return _g1_reserved; } // Returns a MemRegion that corresponds to the space that has been // committed in the heap MemRegion g1_committed() { return _g1_committed; } virtual bool is_in_closed_subset(const void* p) const; // This resets the card table to all zeros. It is used after // a collection pause which used the card table to claim cards. void cleanUpCardTable(); // Iteration functions. // Iterate over all the ref-containing fields of all objects, calling // "cl.do_oop" on each. virtual void oop_iterate(ExtendedOopClosure* cl); // Same as above, restricted to a memory region. void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); // 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 all objects allocated since the last collection, calling // "cl.do_object" on each. The heap must have been initialized properly // to support this function, or else this call will fail. virtual void object_iterate_since_last_GC(ObjectClosure* cl); // Iterate over all spaces in use in the heap, in ascending address order. virtual void space_iterate(SpaceClosure* cl); // Iterate over heap regions, in address order, terminating the // iteration early if the "doHeapRegion" method returns "true". void heap_region_iterate(HeapRegionClosure* blk) const; // Return the region with the given index. It assumes the index is valid. HeapRegion* region_at(uint index) const { return _hrs.at(index); } // Divide the heap region sequence into "chunks" of some size (the number // of regions divided by the number of parallel threads times some // overpartition factor, currently 4). Assumes that this will be called // in parallel by ParallelGCThreads worker threads with discinct worker // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel // calls will use the same "claim_value", and that that claim value is // different from the claim_value of any heap region before the start of // the iteration. Applies "blk->doHeapRegion" to each of the regions, by // attempting to claim the first region in each chunk, and, if // successful, applying the closure to each region in the chunk (and // setting the claim value of the second and subsequent regions of the // chunk.) For now requires that "doHeapRegion" always returns "false", // i.e., that a closure never attempt to abort a traversal. void heap_region_par_iterate_chunked(HeapRegionClosure* blk, uint worker, uint no_of_par_workers, jint claim_value); // It resets all the region claim values to the default. void reset_heap_region_claim_values(); // Resets the claim values of regions in the current // collection set to the default. void reset_cset_heap_region_claim_values(); #ifdef ASSERT bool check_heap_region_claim_values(jint claim_value); // Same as the routine above but only checks regions in the // current collection set. bool check_cset_heap_region_claim_values(jint claim_value); #endif // ASSERT // Clear the cached cset start regions and (more importantly) // the time stamps. Called when we reset the GC time stamp. void clear_cset_start_regions(); // Given the id of a worker, obtain or calculate a suitable // starting region for iterating over the current collection set. HeapRegion* start_cset_region_for_worker(int worker_i); // This is a convenience method that is used by the // HeapRegionIterator classes to calculate the starting region for // each worker so that they do not all start from the same region. HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers); // Iterate over the regions (if any) in the current collection set. void collection_set_iterate(HeapRegionClosure* blk); // As above but starting from region r void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); // Returns the first (lowest address) compactible space in the heap. virtual CompactibleSpace* first_compactible_space(); // A CollectedHeap will contain some number of spaces. This finds the // space containing a given address, or else returns NULL. virtual Space* space_containing(const void* addr) const; // A G1CollectedHeap will contain some number of heap regions. This // finds the region containing a given address, or else returns NULL. template inline HeapRegion* heap_region_containing(const T addr) const; // Like the above, but requires "addr" to be in the heap (to avoid a // null-check), and unlike the above, may return an continuing humongous // region. template inline HeapRegion* heap_region_containing_raw(const T addr) const; // A CollectedHeap is divided into a dense sequence of "blocks"; that is, // each address in the (reserved) heap is a member of exactly // one block. The defining characteristic of a block is that it is // possible to find its size, and thus to progress forward to the next // block. (Blocks may be of different sizes.) Thus, blocks may // represent Java objects, or they might be free blocks in a // free-list-based heap (or subheap), as long as the two kinds are // distinguishable and the size of each is determinable. // Returns the address of the start of the "block" that contains the // address "addr". We say "blocks" instead of "object" since some heaps // may not pack objects densely; a chunk may either be an object or a // non-object. virtual HeapWord* block_start(const void* addr) const; // Requires "addr" to be the start of a chunk, and returns its size. // "addr + size" is required to be the start of a new chunk, or the end // of the active area of the heap. virtual size_t block_size(const HeapWord* addr) const; // Requires "addr" to be the start of a block, and returns "TRUE" iff // the block is an object. virtual bool block_is_obj(const HeapWord* addr) const; // Does this heap support heap inspection? (+PrintClassHistogram) virtual bool supports_heap_inspection() const { return true; } // Section on thread-local allocation buffers (TLABs) // See CollectedHeap for semantics. virtual bool supports_tlab_allocation() const; virtual size_t tlab_capacity(Thread* thr) const; virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; // Can a compiler initialize a new object without store barriers? // This permission only extends from the creation of a new object // via a TLAB up to the first subsequent safepoint. If such permission // is granted for this heap type, the compiler promises to call // defer_store_barrier() below on any slow path allocation of // a new object for which such initializing store barriers will // have been elided. G1, like CMS, allows this, but should be // ready to provide a compensating write barrier as necessary // if that storage came out of a non-young region. The efficiency // of this implementation depends crucially on being able to // answer very efficiently in constant time whether a piece of // storage in the heap comes from a young region or not. // See ReduceInitialCardMarks. virtual bool can_elide_tlab_store_barriers() const { return true; } virtual bool card_mark_must_follow_store() const { return true; } bool is_in_young(const oop obj) { HeapRegion* hr = heap_region_containing(obj); return hr != NULL && hr->is_young(); } #ifdef ASSERT virtual bool is_in_partial_collection(const void* p); #endif virtual bool is_scavengable(const void* addr); // We don't need barriers for initializing stores to objects // in the young gen: for the SATB pre-barrier, there is no // pre-value that needs to be remembered; for the remembered-set // update logging post-barrier, we don't maintain remembered set // information for young gen objects. virtual bool can_elide_initializing_store_barrier(oop new_obj) { return is_in_young(new_obj); } // Returns "true" iff the given word_size is "very large". static bool isHumongous(size_t word_size) { // Note this has to be strictly greater-than as the TLABs // are capped at the humongous thresold and we want to // ensure that we don't try to allocate a TLAB as // humongous and that we don't allocate a humongous // object in a TLAB. return word_size > _humongous_object_threshold_in_words; } // Update mod union table with the set of dirty cards. void updateModUnion(); // Set the mod union bits corresponding to the given memRegion. Note // that this is always a safe operation, since it doesn't clear any // bits. void markModUnionRange(MemRegion mr); // Records the fact that a marking phase is no longer in progress. void set_marking_complete() { _mark_in_progress = false; } void set_marking_started() { _mark_in_progress = true; } bool mark_in_progress() { return _mark_in_progress; } // Print the maximum heap capacity. virtual size_t max_capacity() const; virtual jlong millis_since_last_gc(); // Perform any cleanup actions necessary before allowing a verification. virtual void prepare_for_verify(); // Perform verification. // vo == UsePrevMarking -> use "prev" marking information, // vo == UseNextMarking -> use "next" marking information // vo == UseMarkWord -> use the mark word in the object header // // NOTE: Only the "prev" marking information is guaranteed to be // consistent most of the time, so most calls to this should use // vo == UsePrevMarking. // Currently, there is only one case where this is called with // vo == UseNextMarking, which is to verify the "next" marking // information at the end of remark. // Currently there is only one place where this is called with // vo == UseMarkWord, which is to verify the marking during a // full GC. void verify(bool silent, VerifyOption vo); // Override; it uses the "prev" marking information virtual void verify(bool silent); 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; // Convenience function to be used in situations where the heap type can be // asserted to be this type. static G1CollectedHeap* heap(); void set_region_short_lived_locked(HeapRegion* hr); // add appropriate methods for any other surv rate groups YoungList* young_list() { return _young_list; } // debugging bool check_young_list_well_formed() { return _young_list->check_list_well_formed(); } bool check_young_list_empty(bool check_heap, bool check_sample = true); // *** Stuff related to concurrent marking. It's not clear to me that so // many of these need to be public. // The functions below are helper functions that a subclass of // "CollectedHeap" can use in the implementation of its virtual // functions. // This performs a concurrent marking of the live objects in a // bitmap off to the side. void doConcurrentMark(); bool isMarkedPrev(oop obj) const; bool isMarkedNext(oop obj) const; // Determine if an object is dead, given the object and also // the region to which the object belongs. An object is dead // iff a) it was not allocated since the last mark and b) it // is not marked. bool is_obj_dead(const oop obj, const HeapRegion* hr) const { return !hr->obj_allocated_since_prev_marking(obj) && !isMarkedPrev(obj); } // This function returns true when an object has been // around since the previous marking and hasn't yet // been marked during this marking. bool is_obj_ill(const oop obj, const HeapRegion* hr) const { return !hr->obj_allocated_since_next_marking(obj) && !isMarkedNext(obj); } // Determine if an object is dead, given only the object itself. // This will find the region to which the object belongs and // then call the region version of the same function. // Added if it is NULL it isn't dead. bool is_obj_dead(const oop obj) const { const HeapRegion* hr = heap_region_containing(obj); if (hr == NULL) { if (obj == NULL) return false; else return true; } else return is_obj_dead(obj, hr); } bool is_obj_ill(const oop obj) const { const HeapRegion* hr = heap_region_containing(obj); if (hr == NULL) { if (obj == NULL) return false; else return true; } else return is_obj_ill(obj, hr); } // The methods below are here for convenience and dispatch the // appropriate method depending on value of the given VerifyOption // parameter. The options for that parameter are: // // vo == UsePrevMarking -> use "prev" marking information, // vo == UseNextMarking -> use "next" marking information, // vo == UseMarkWord -> use mark word from object header bool is_obj_dead_cond(const oop obj, const HeapRegion* hr, const VerifyOption vo) const { switch (vo) { case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); default: ShouldNotReachHere(); } return false; // keep some compilers happy } bool is_obj_dead_cond(const oop obj, const VerifyOption vo) const { switch (vo) { case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); default: ShouldNotReachHere(); } return false; // keep some compilers happy } bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); bool is_marked(oop obj, VerifyOption vo); const char* top_at_mark_start_str(VerifyOption vo); // The following is just to alert the verification code // that a full collection has occurred and that the // remembered sets are no longer up to date. bool _full_collection; void set_full_collection() { _full_collection = true;} void clear_full_collection() {_full_collection = false;} bool full_collection() {return _full_collection;} ConcurrentMark* concurrent_mark() const { return _cm; } ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } // The dirty cards region list is used to record a subset of regions // whose cards need clearing. The list if populated during the // remembered set scanning and drained during the card table // cleanup. Although the methods are reentrant, population/draining // phases must not overlap. For synchronization purposes the last // element on the list points to itself. HeapRegion* _dirty_cards_region_list; void push_dirty_cards_region(HeapRegion* hr); HeapRegion* pop_dirty_cards_region(); public: void stop_conc_gc_threads(); size_t pending_card_num(); size_t cards_scanned(); protected: size_t _max_heap_capacity; }; class G1ParGCAllocBuffer: public ParGCAllocBuffer { private: bool _retired; public: G1ParGCAllocBuffer(size_t gclab_word_size); void set_buf(HeapWord* buf) { ParGCAllocBuffer::set_buf(buf); _retired = false; } void retire(bool end_of_gc, bool retain) { if (_retired) return; ParGCAllocBuffer::retire(end_of_gc, retain); _retired = true; } }; class G1ParScanThreadState : public StackObj { protected: G1CollectedHeap* _g1h; RefToScanQueue* _refs; DirtyCardQueue _dcq; CardTableModRefBS* _ct_bs; G1RemSet* _g1_rem; G1ParGCAllocBuffer _surviving_alloc_buffer; G1ParGCAllocBuffer _tenured_alloc_buffer; G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount]; ageTable _age_table; size_t _alloc_buffer_waste; size_t _undo_waste; OopsInHeapRegionClosure* _evac_failure_cl; G1ParScanHeapEvacClosure* _evac_cl; G1ParScanPartialArrayClosure* _partial_scan_cl; int _hash_seed; uint _queue_num; size_t _term_attempts; double _start; double _start_strong_roots; double _strong_roots_time; double _start_term; double _term_time; // Map from young-age-index (0 == not young, 1 is youngest) to // surviving words. base is what we get back from the malloc call size_t* _surviving_young_words_base; // this points into the array, as we use the first few entries for padding size_t* _surviving_young_words; #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t)) void add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; } void add_to_undo_waste(size_t waste) { _undo_waste += waste; } DirtyCardQueue& dirty_card_queue() { return _dcq; } CardTableModRefBS* ctbs() { return _ct_bs; } template void immediate_rs_update(HeapRegion* from, T* p, int tid) { if (!from->is_survivor()) { _g1_rem->par_write_ref(from, p, tid); } } template void deferred_rs_update(HeapRegion* from, T* p, int tid) { // If the new value of the field points to the same region or // is the to-space, we don't need to include it in the Rset updates. if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) { size_t card_index = ctbs()->index_for(p); // If the card hasn't been added to the buffer, do it. if (ctbs()->mark_card_deferred(card_index)) { dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index)); } } } public: G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num); ~G1ParScanThreadState() { FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC); } RefToScanQueue* refs() { return _refs; } ageTable* age_table() { return &_age_table; } G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) { return _alloc_buffers[purpose]; } size_t alloc_buffer_waste() const { return _alloc_buffer_waste; } size_t undo_waste() const { return _undo_waste; } #ifdef ASSERT bool verify_ref(narrowOop* ref) const; bool verify_ref(oop* ref) const; bool verify_task(StarTask ref) const; #endif // ASSERT template void push_on_queue(T* ref) { assert(verify_ref(ref), "sanity"); refs()->push(ref); } template void update_rs(HeapRegion* from, T* p, int tid) { if (G1DeferredRSUpdate) { deferred_rs_update(from, p, tid); } else { immediate_rs_update(from, p, tid); } } HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) { HeapWord* obj = NULL; size_t gclab_word_size = _g1h->desired_plab_sz(purpose); if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) { G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose); add_to_alloc_buffer_waste(alloc_buf->words_remaining()); alloc_buf->retire(false /* end_of_gc */, false /* retain */); HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size); if (buf == NULL) return NULL; // Let caller handle allocation failure. // Otherwise. alloc_buf->set_word_size(gclab_word_size); alloc_buf->set_buf(buf); obj = alloc_buf->allocate(word_sz); assert(obj != NULL, "buffer was definitely big enough..."); } else { obj = _g1h->par_allocate_during_gc(purpose, word_sz); } return obj; } HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) { HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz); if (obj != NULL) return obj; return allocate_slow(purpose, word_sz); } void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) { if (alloc_buffer(purpose)->contains(obj)) { assert(alloc_buffer(purpose)->contains(obj + word_sz - 1), "should contain whole object"); alloc_buffer(purpose)->undo_allocation(obj, word_sz); } else { CollectedHeap::fill_with_object(obj, word_sz); add_to_undo_waste(word_sz); } } void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) { _evac_failure_cl = evac_failure_cl; } OopsInHeapRegionClosure* evac_failure_closure() { return _evac_failure_cl; } void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) { _evac_cl = evac_cl; } void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) { _partial_scan_cl = partial_scan_cl; } int* hash_seed() { return &_hash_seed; } uint queue_num() { return _queue_num; } size_t term_attempts() const { return _term_attempts; } void note_term_attempt() { _term_attempts++; } void start_strong_roots() { _start_strong_roots = os::elapsedTime(); } void end_strong_roots() { _strong_roots_time += (os::elapsedTime() - _start_strong_roots); } double strong_roots_time() const { return _strong_roots_time; } void start_term_time() { note_term_attempt(); _start_term = os::elapsedTime(); } void end_term_time() { _term_time += (os::elapsedTime() - _start_term); } double term_time() const { return _term_time; } double elapsed_time() const { return os::elapsedTime() - _start; } static void print_termination_stats_hdr(outputStream* const st = gclog_or_tty); void print_termination_stats(int i, outputStream* const st = gclog_or_tty) const; size_t* surviving_young_words() { // We add on to hide entry 0 which accumulates surviving words for // age -1 regions (i.e. non-young ones) return _surviving_young_words; } void retire_alloc_buffers() { for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { size_t waste = _alloc_buffers[ap]->words_remaining(); add_to_alloc_buffer_waste(waste); _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap), true /* end_of_gc */, false /* retain */); } } template void deal_with_reference(T* ref_to_scan) { if (has_partial_array_mask(ref_to_scan)) { _partial_scan_cl->do_oop_nv(ref_to_scan); } else { // Note: we can use "raw" versions of "region_containing" because // "obj_to_scan" is definitely in the heap, and is not in a // humongous region. HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan); _evac_cl->set_region(r); _evac_cl->do_oop_nv(ref_to_scan); } } void deal_with_reference(StarTask ref) { assert(verify_task(ref), "sanity"); if (ref.is_narrow()) { deal_with_reference((narrowOop*)ref); } else { deal_with_reference((oop*)ref); } } public: void trim_queue(); }; #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP