/* * Copyright 2001-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, * CA 95054 USA or visit www.sun.com if you need additional information or * have any questions. * */ // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. // It uses the "Garbage First" heap organization and algorithm, which // may combine concurrent marking with parallel, incremental compaction of // heap subsets that will yield large amounts of garbage. class HeapRegion; class HeapRegionSeq; class PermanentGenerationSpec; class GenerationSpec; class OopsInHeapRegionClosure; class G1ScanHeapEvacClosure; class ObjectClosure; class SpaceClosure; class CompactibleSpaceClosure; class Space; class G1CollectorPolicy; class GenRemSet; class G1RemSet; class HeapRegionRemSetIterator; class ConcurrentMark; class ConcurrentMarkThread; class ConcurrentG1Refine; class ConcurrentZFThread; // If want to accumulate detailed statistics on work queues // turn this on. #define G1_DETAILED_STATS 0 #if G1_DETAILED_STATS # define IF_G1_DETAILED_STATS(code) code #else # define IF_G1_DETAILED_STATS(code) #endif typedef GenericTaskQueue RefToScanQueue; typedef GenericTaskQueueSet RefToScanQueueSet; typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) enum G1GCThreadGroups { G1CRGroup = 0, G1ZFGroup = 1, G1CMGroup = 2, G1CLGroup = 3 }; enum GCAllocPurpose { GCAllocForTenured, GCAllocForSurvived, GCAllocPurposeCount }; class YoungList : public CHeapObj { private: G1CollectedHeap* _g1h; HeapRegion* _head; HeapRegion* _scan_only_head; HeapRegion* _scan_only_tail; size_t _length; size_t _scan_only_length; size_t _last_sampled_rs_lengths; size_t _sampled_rs_lengths; HeapRegion* _curr; HeapRegion* _curr_scan_only; HeapRegion* _survivor_head; HeapRegion* _survivor_tail; size_t _survivor_length; void empty_list(HeapRegion* list); public: YoungList(G1CollectedHeap* g1h); void push_region(HeapRegion* hr); void add_survivor_region(HeapRegion* hr); HeapRegion* pop_region(); void empty_list(); bool is_empty() { return _length == 0; } size_t length() { return _length; } size_t scan_only_length() { return _scan_only_length; } size_t survivor_length() { return _survivor_length; } void rs_length_sampling_init(); bool rs_length_sampling_more(); void rs_length_sampling_next(); void reset_sampled_info() { _last_sampled_rs_lengths = 0; } size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } // for development purposes void reset_auxilary_lists(); HeapRegion* first_region() { return _head; } HeapRegion* first_scan_only_region() { return _scan_only_head; } HeapRegion* first_survivor_region() { return _survivor_head; } HeapRegion* last_survivor_region() { return _survivor_tail; } HeapRegion* par_get_next_scan_only_region() { MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); HeapRegion* ret = _curr_scan_only; if (ret != NULL) _curr_scan_only = ret->get_next_young_region(); return ret; } // debugging bool check_list_well_formed(); bool check_list_empty(bool ignore_scan_only_list, bool check_sample = true); void print(); }; class RefineCardTableEntryClosure; class G1CollectedHeap : public SharedHeap { friend class VM_G1CollectForAllocation; friend class VM_GenCollectForPermanentAllocation; friend class VM_G1CollectFull; friend class VM_G1IncCollectionPause; friend class VMStructs; // Closures used in implementation. friend class G1ParCopyHelper; friend class G1IsAliveClosure; friend class G1EvacuateFollowersClosure; friend class G1ParScanThreadState; friend class G1ParScanClosureSuper; friend class G1ParEvacuateFollowersClosure; friend class G1ParTask; friend class G1FreeGarbageRegionClosure; friend class RefineCardTableEntryClosure; friend class G1PrepareCompactClosure; friend class RegionSorter; friend class CountRCClosure; friend class EvacPopObjClosure; friend class G1ParCleanupCTTask; // Other related classes. friend class G1MarkSweep; private: enum SomePrivateConstants { VeryLargeInBytes = HeapRegion::GrainBytes/2, VeryLargeInWords = VeryLargeInBytes/HeapWordSize, MinHeapDeltaBytes = 10 * HeapRegion::GrainBytes, // FIXME NumAPIs = HeapRegion::MaxAge }; // The one and only G1CollectedHeap, so static functions can find it. static G1CollectedHeap* _g1h; // Storage for the G1 heap (excludes the permanent generation). VirtualSpace _g1_storage; MemRegion _g1_reserved; // The part of _g1_storage that is currently committed. MemRegion _g1_committed; // The maximum part of _g1_storage that has ever been committed. MemRegion _g1_max_committed; // The number of regions that are completely free. size_t _free_regions; // The number of regions we could create by expansion. size_t _expansion_regions; // Return the number of free regions in the heap (by direct counting.) size_t count_free_regions(); // Return the number of free regions on the free and unclean lists. size_t count_free_regions_list(); // The block offset table for the G1 heap. G1BlockOffsetSharedArray* _bot_shared; // Move all of the regions off the free lists, then rebuild those free // lists, before and after full GC. void tear_down_region_lists(); void rebuild_region_lists(); // This sets all non-empty regions to need zero-fill (which they will if // they are empty after full collection.) void set_used_regions_to_need_zero_fill(); // The sequence of all heap regions in the heap. HeapRegionSeq* _hrs; // The region from which normal-sized objects are currently being // allocated. May be NULL. HeapRegion* _cur_alloc_region; // Postcondition: cur_alloc_region == NULL. void abandon_cur_alloc_region(); void abandon_gc_alloc_regions(); // The to-space memory regions into which objects are being copied during // a GC. HeapRegion* _gc_alloc_regions[GCAllocPurposeCount]; size_t _gc_alloc_region_counts[GCAllocPurposeCount]; // These are the regions, one per GCAllocPurpose, that are half-full // at the end of a collection and that we want to reuse during the // next collection. HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount]; // This specifies whether we will keep the last half-full region at // the end of a collection so that it can be reused during the next // collection (this is specified per GCAllocPurpose) bool _retain_gc_alloc_region[GCAllocPurposeCount]; // A list of the regions that have been set to be alloc regions in the // current collection. HeapRegion* _gc_alloc_region_list; // When called by par thread, require par_alloc_during_gc_lock() to be held. void push_gc_alloc_region(HeapRegion* hr); // This should only be called single-threaded. Undeclares all GC alloc // regions. void forget_alloc_region_list(); // Should be used to set an alloc region, because there's other // associated bookkeeping. void set_gc_alloc_region(int purpose, HeapRegion* r); // Check well-formedness of alloc region list. bool check_gc_alloc_regions(); // Outside of GC pauses, the number of bytes used in all regions other // than the current allocation region. size_t _summary_bytes_used; // This is used for a quick test on whether a reference points into // the collection set or not. Basically, we have an array, with one // byte per region, and that byte denotes whether the corresponding // region is in the collection set or not. The entry corresponding // the bottom of the heap, i.e., region 0, is pointed to by // _in_cset_fast_test_base. The _in_cset_fast_test field has been // biased so that it actually points to address 0 of the address // space, to make the test as fast as possible (we can simply shift // the address to address into it, instead of having to subtract the // bottom of the heap from the address before shifting it; basically // it works in the same way the card table works). bool* _in_cset_fast_test; // The allocated array used for the fast test on whether a reference // points into the collection set or not. This field is also used to // free the array. bool* _in_cset_fast_test_base; // The length of the _in_cset_fast_test_base array. size_t _in_cset_fast_test_length; volatile unsigned _gc_time_stamp; size_t* _surviving_young_words; void setup_surviving_young_words(); void update_surviving_young_words(size_t* surv_young_words); void cleanup_surviving_young_words(); protected: // Returns "true" iff none of the gc alloc regions have any allocations // since the last call to "save_marks". bool all_alloc_regions_no_allocs_since_save_marks(); // Perform finalization stuff on all allocation regions. void retire_all_alloc_regions(); // The number of regions allocated to hold humongous objects. int _num_humongous_regions; YoungList* _young_list; // The current policy object for the collector. G1CollectorPolicy* _g1_policy; // Parallel allocation lock to protect the current allocation region. Mutex _par_alloc_during_gc_lock; Mutex* par_alloc_during_gc_lock() { return &_par_alloc_during_gc_lock; } // If possible/desirable, allocate a new HeapRegion for normal object // allocation sufficient for an allocation of the given "word_size". // If "do_expand" is true, will attempt to expand the heap if necessary // to to satisfy the request. If "zero_filled" is true, requires a // zero-filled region. // (Returning NULL will trigger a GC.) virtual HeapRegion* newAllocRegion_work(size_t word_size, bool do_expand, bool zero_filled); virtual HeapRegion* newAllocRegion(size_t word_size, bool zero_filled = true) { return newAllocRegion_work(word_size, false, zero_filled); } virtual HeapRegion* newAllocRegionWithExpansion(int purpose, size_t word_size, bool zero_filled = true); // Attempt to allocate an object of the given (very large) "word_size". // Returns "NULL" on failure. virtual HeapWord* humongousObjAllocate(size_t word_size); // If possible, allocate a block of the given word_size, else return "NULL". // Returning NULL will trigger GC or heap expansion. // These two methods have rather awkward pre- and // post-conditions. If they are called outside a safepoint, then // they assume that the caller is holding the heap lock. Upon return // they release the heap lock, if they are returning a non-NULL // value. attempt_allocation_slow() also dirties the cards of a // newly-allocated young region after it releases the heap // lock. This change in interface was the neatest way to achieve // this card dirtying without affecting mem_allocate(), which is a // more frequently called method. We tried two or three different // approaches, but they were even more hacky. HeapWord* attempt_allocation(size_t word_size, bool permit_collection_pause = true); HeapWord* attempt_allocation_slow(size_t word_size, bool permit_collection_pause = true); // 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* allocate_during_gc(GCAllocPurpose purpose, size_t word_size); HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size); HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, HeapRegion* alloc_region, bool par, size_t word_size); // Ensure that no further allocations can happen in "r", bearing in mind // that parallel threads might be attempting allocations. void par_allocate_remaining_space(HeapRegion* r); // Retires an allocation region when it is full or at the end of a // GC pause. void retire_alloc_region(HeapRegion* alloc_region, bool par); // Helper function for two callbacks below. // "full", if true, indicates that the GC is for a System.gc() request, // and should collect the entire heap. If "clear_all_soft_refs" is true, // all soft references are cleared during the GC. If "full" is false, // "word_size" describes the allocation that the GC should // attempt (at least) to satisfy. void do_collection(bool full, bool clear_all_soft_refs, size_t word_size); // Callback from VM_G1CollectFull operation. // Perform a full collection. void do_full_collection(bool clear_all_soft_refs); // Resize the heap if necessary after a full collection. If this is // after a collect-for allocation, "word_size" is the allocation size, // and will be considered part of the used portion of the heap. void resize_if_necessary_after_full_collection(size_t word_size); // Callback from VM_G1CollectForAllocation operation. // This function does everything necessary/possible to satisfy a // failed allocation request (including collection, expansion, etc.) HeapWord* satisfy_failed_allocation(size_t word_size); // 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". virtual HeapWord* expand_and_allocate(size_t word_size); public: // Expand the garbage-first heap by at least the given size (in bytes!). // (Rounds up to a HeapRegion boundary.) virtual void expand(size_t expand_bytes); // Do anything common to GC's. virtual void gc_prologue(bool full); virtual void gc_epilogue(bool full); // We register a region with the fast "in collection set" test. We // simply set to true the array slot corresponding to this region. void register_region_with_in_cset_fast_test(HeapRegion* r) { assert(_in_cset_fast_test_base != NULL, "sanity"); assert(r->in_collection_set(), "invariant"); int index = r->hrs_index(); assert(0 <= (size_t) index && (size_t) index < _in_cset_fast_test_length, "invariant"); assert(!_in_cset_fast_test_base[index], "invariant"); _in_cset_fast_test_base[index] = true; } // This is a fast test on whether a reference points into the // collection set or not. It does not assume that the reference // points into the heap; if it doesn't, it will return false. bool in_cset_fast_test(oop obj) { assert(_in_cset_fast_test != NULL, "sanity"); if (_g1_committed.contains((HeapWord*) obj)) { // no need to subtract the bottom of the heap from obj, // _in_cset_fast_test is biased size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes; bool ret = _in_cset_fast_test[index]; // let's make sure the result is consistent with what the slower // test returns assert( ret || !obj_in_cs(obj), "sanity"); assert(!ret || obj_in_cs(obj), "sanity"); return ret; } else { return false; } } 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); // Do an incremental collection: identify a collection set, and evacuate // its live objects elsewhere. virtual void do_collection_pause(); // The guts of the incremental collection pause, executed by the vm // thread. virtual void do_collection_pause_at_safepoint(); // Actually do the work of evacuating the collection set. virtual void evacuate_collection_set(); // If this is an appropriate right time, do a collection pause. // The "word_size" argument, if non-zero, indicates the size of an // allocation request that is prompting this query. void do_collection_pause_if_appropriate(size_t word_size); // The g1 remembered set of the heap. G1RemSet* _g1_rem_set; // And it's mod ref barrier set, used to track updates for the above. ModRefBarrierSet* _mr_bs; // A set of cards that cover the objects for which the Rsets should be updated // concurrently after the collection. DirtyCardQueueSet _dirty_card_queue_set; // The Heap Region Rem Set Iterator. HeapRegionRemSetIterator** _rem_set_iterator; // The closure used to refine a single card. RefineCardTableEntryClosure* _refine_cte_cl; // A function to check the consistency of dirty card logs. void check_ct_logs_at_safepoint(); // After a collection pause, make the regions in the CS into free // regions. void free_collection_set(HeapRegion* cs_head); // Applies "scan_non_heap_roots" to roots outside the heap, // "scan_rs" to roots inside the heap (having done "set_region" to // indicate the region in which the root resides), and does "scan_perm" // (setting the generation to the perm generation.) If "scan_rs" is // NULL, then this step is skipped. The "worker_i" // param is for use with parallel roots processing, and should be // the "i" of the calling parallel worker thread's work(i) function. // In the sequential case this param will be ignored. void g1_process_strong_roots(bool collecting_perm_gen, SharedHeap::ScanningOption so, OopClosure* scan_non_heap_roots, OopsInHeapRegionClosure* scan_rs, OopsInHeapRegionClosure* scan_so, OopsInGenClosure* scan_perm, int worker_i); void scan_scan_only_set(OopsInHeapRegionClosure* oc, int worker_i); void scan_scan_only_region(HeapRegion* hr, OopsInHeapRegionClosure* oc, int worker_i); // Apply "blk" to all the weak roots of the system. These include // JNI weak roots, the code cache, system dictionary, symbol table, // string table, and referents of reachable weak refs. void g1_process_weak_roots(OopClosure* root_closure, OopClosure* non_root_closure); // Invoke "save_marks" on all heap regions. void save_marks(); // Free a heap region. void free_region(HeapRegion* hr); // A component of "free_region", exposed for 'batching'. // All the params after "hr" are out params: the used bytes of the freed // region(s), the number of H regions cleared, the number of regions // freed, and pointers to the head and tail of a list of freed contig // regions, linked throught the "next_on_unclean_list" field. void free_region_work(HeapRegion* hr, size_t& pre_used, size_t& cleared_h, size_t& freed_regions, UncleanRegionList* list, bool par = false); // The concurrent marker (and the thread it runs in.) ConcurrentMark* _cm; ConcurrentMarkThread* _cmThread; bool _mark_in_progress; // The concurrent refiner. ConcurrentG1Refine* _cg1r; // The concurrent zero-fill thread. ConcurrentZFThread* _czft; // The parallel task queues RefToScanQueueSet *_task_queues; // True iff a evacuation has failed in the current collection. bool _evacuation_failed; // Set the attribute indicating whether evacuation has failed in the // current collection. void set_evacuation_failed(bool b) { _evacuation_failed = b; } // Failed evacuations cause some logical from-space objects to have // forwarding pointers to themselves. Reset them. void remove_self_forwarding_pointers(); // When one is non-null, so is the other. Together, they each pair is // an object with a preserved mark, and its mark value. GrowableArray* _objs_with_preserved_marks; GrowableArray* _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. void handle_evacuation_failure(oop obj); oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj); void handle_evacuation_failure_common(oop obj, markOop m); // Ensure that the relevant gc_alloc regions are set. void get_gc_alloc_regions(); // We're done with GC alloc regions. We are going to tear down the // gc alloc list and remove the gc alloc tag from all the regions on // that list. However, we will also retain the last (i.e., the one // that is half-full) GC alloc region, per GCAllocPurpose, for // possible reuse during the next collection, provided // _retain_gc_alloc_region[] indicates that it should be the // case. Said regions are kept in the _retained_gc_alloc_regions[] // array. If the parameter totally is set, we will not retain any // regions, irrespective of what _retain_gc_alloc_region[] // indicates. void release_gc_alloc_regions(bool totally); #ifndef PRODUCT // Useful for debugging. void print_gc_alloc_regions(); #endif // !PRODUCT // ("Weak") Reference processing support ReferenceProcessor* _ref_processor; enum G1H_process_strong_roots_tasks { G1H_PS_mark_stack_oops_do, G1H_PS_refProcessor_oops_do, // Leave this one last. G1H_PS_NumElements }; SubTasksDone* _process_strong_tasks; // List of regions which require zero filling. UncleanRegionList _unclean_region_list; bool _unclean_regions_coming; public: void set_refine_cte_cl_concurrency(bool concurrent); RefToScanQueue *task_queue(int i); // A set of cards where updates happened during the GC DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } // Create a G1CollectedHeap with the specified policy. // Must call the initialize method afterwards. // May not return if something goes wrong. G1CollectedHeap(G1CollectorPolicy* policy); // Initialize the G1CollectedHeap to have the initial and // maximum sizes, permanent generation, and remembered and barrier sets // specified by the policy object. jint initialize(); void ref_processing_init(); void set_par_threads(int t) { SharedHeap::set_par_threads(t); _process_strong_tasks->set_par_threads(t); } virtual CollectedHeap::Name kind() const { return CollectedHeap::G1CollectedHeap; } // The current policy object for the collector. G1CollectorPolicy* g1_policy() const { return _g1_policy; } // Adaptive size policy. No such thing for g1. virtual AdaptiveSizePolicy* size_policy() { return NULL; } // The rem set and barrier set. G1RemSet* g1_rem_set() const { return _g1_rem_set; } ModRefBarrierSet* mr_bs() const { return _mr_bs; } // The rem set iterator. HeapRegionRemSetIterator* rem_set_iterator(int i) { return _rem_set_iterator[i]; } HeapRegionRemSetIterator* rem_set_iterator() { return _rem_set_iterator[0]; } unsigned get_gc_time_stamp() { return _gc_time_stamp; } void reset_gc_time_stamp() { _gc_time_stamp = 0; OrderAccess::fence(); } void increment_gc_time_stamp() { ++_gc_time_stamp; OrderAccess::fence(); } void iterate_dirty_card_closure(bool concurrent, int worker_i); // The shared block offset table array. G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } // Reference Processing accessor ReferenceProcessor* ref_processor() { return _ref_processor; } // Reserved (g1 only; super method includes perm), capacity and the used // portion in bytes. size_t g1_reserved_obj_bytes() { return _g1_reserved.byte_size(); } virtual size_t capacity() const; virtual size_t used() const; size_t recalculate_used() const; #ifndef PRODUCT size_t recalculate_used_regions() const; #endif // PRODUCT // These virtual functions do the actual allocation. virtual HeapWord* mem_allocate(size_t word_size, bool is_noref, bool is_tlab, bool* gc_overhead_limit_was_exceeded); // Some heaps may offer a contiguous region for shared non-blocking // allocation, via inlined code (by exporting the address of the top and // end fields defining the extent of the contiguous allocation region.) // But G1CollectedHeap doesn't yet support this. // Return an estimate of the maximum allocation that could be performed // without triggering any collection or expansion activity. In a // generational collector, for example, this is probably the largest // allocation that could be supported (without expansion) in the youngest // generation. It is "unsafe" because no locks are taken; the result // should be treated as an approximation, not a guarantee, for use in // heuristic resizing decisions. virtual size_t unsafe_max_alloc(); virtual bool is_maximal_no_gc() const { return _g1_storage.uncommitted_size() == 0; } // The total number of regions in the heap. size_t n_regions(); // The number of regions that are completely free. size_t max_regions(); // The number of regions that are completely free. size_t free_regions(); // The number of regions that are not completely free. size_t used_regions() { return n_regions() - free_regions(); } // True iff the ZF thread should run. bool should_zf(); // The number of regions available for "regular" expansion. size_t expansion_regions() { return _expansion_regions; } #ifndef PRODUCT bool regions_accounted_for(); bool print_region_accounting_info(); void print_region_counts(); #endif HeapRegion* alloc_region_from_unclean_list(bool zero_filled); HeapRegion* alloc_region_from_unclean_list_locked(bool zero_filled); void put_region_on_unclean_list(HeapRegion* r); void put_region_on_unclean_list_locked(HeapRegion* r); void prepend_region_list_on_unclean_list(UncleanRegionList* list); void prepend_region_list_on_unclean_list_locked(UncleanRegionList* list); void set_unclean_regions_coming(bool b); void set_unclean_regions_coming_locked(bool b); // Wait for cleanup to be complete. void wait_for_cleanup_complete(); // Like above, but assumes that the calling thread owns the Heap_lock. void wait_for_cleanup_complete_locked(); // Return the head of the unclean list. HeapRegion* peek_unclean_region_list_locked(); // Remove and return the head of the unclean list. HeapRegion* pop_unclean_region_list_locked(); // List of regions which are zero filled and ready for allocation. HeapRegion* _free_region_list; // Number of elements on the free list. size_t _free_region_list_size; // If the head of the unclean list is ZeroFilled, move it to the free // list. bool move_cleaned_region_to_free_list_locked(); bool move_cleaned_region_to_free_list(); void put_free_region_on_list_locked(HeapRegion* r); void put_free_region_on_list(HeapRegion* r); // Remove and return the head element of the free list. HeapRegion* pop_free_region_list_locked(); // If "zero_filled" is true, we first try the free list, then we try the // unclean list, zero-filling the result. If "zero_filled" is false, we // first try the unclean list, then the zero-filled list. HeapRegion* alloc_free_region_from_lists(bool zero_filled); // Verify the integrity of the region lists. void remove_allocated_regions_from_lists(); bool verify_region_lists(); bool verify_region_lists_locked(); size_t unclean_region_list_length(); size_t free_region_list_length(); // Perform a collection of the heap; intended for use in implementing // "System.gc". This probably implies as full a collection as the // "CollectedHeap" supports. virtual void collect(GCCause::Cause cause); // The same as above but assume that the caller holds the Heap_lock. void collect_locked(GCCause::Cause cause); // This interface assumes that it's being called by the // vm thread. It collects the heap assuming that the // heap lock is already held and that we are executing in // the context of the vm thread. virtual void collect_as_vm_thread(GCCause::Cause cause); // True iff a evacuation has failed in the most-recent collection. bool evacuation_failed() { return _evacuation_failed; } // Free a region if it is totally full of garbage. Returns the number of // bytes freed (0 ==> didn't free it). size_t free_region_if_totally_empty(HeapRegion *hr); void free_region_if_totally_empty_work(HeapRegion *hr, size_t& pre_used, size_t& cleared_h_regions, size_t& freed_regions, UncleanRegionList* list, bool par = false); // If we've done free region work that yields the given changes, update // the relevant global variables. void finish_free_region_work(size_t pre_used, size_t cleared_h_regions, size_t freed_regions, UncleanRegionList* list); // Returns "TRUE" iff "p" points into the allocated area of the heap. virtual bool is_in(const void* p) const; // Return "TRUE" iff the given object address is within the collection // set. inline bool obj_in_cs(oop obj); // Return "TRUE" iff the given object address is in the reserved // region of g1 (excluding the permanent generation). bool is_in_g1_reserved(const void* p) const { return _g1_reserved.contains(p); } // Returns a MemRegion that corresponds to the space that has been // committed in the heap MemRegion g1_committed() { return _g1_committed; } NOT_PRODUCT( bool is_in_closed_subset(const void* p) const; ) // Dirty card table entries covering a list of young regions. void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list); // This resets the card table to all zeros. It is used after // a collection pause which used the card table to claim cards. void cleanUpCardTable(); // Iteration functions. // Iterate over all the ref-containing fields of all objects, calling // "cl.do_oop" on each. virtual void oop_iterate(OopClosure* cl) { oop_iterate(cl, true); } void oop_iterate(OopClosure* cl, bool do_perm); // Same as above, restricted to a memory region. virtual void oop_iterate(MemRegion mr, OopClosure* cl) { oop_iterate(mr, cl, true); } void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm); // Iterate over all objects, calling "cl.do_object" on each. virtual void object_iterate(ObjectClosure* cl) { object_iterate(cl, true); } virtual void safe_object_iterate(ObjectClosure* cl) { object_iterate(cl, true); } void object_iterate(ObjectClosure* cl, bool do_perm); // Iterate over all objects allocated since the last collection, calling // "cl.do_object" on each. The heap must have been initialized properly // to support this function, or else this call will fail. virtual void object_iterate_since_last_GC(ObjectClosure* cl); // Iterate over all spaces in use in the heap, in ascending address order. virtual void space_iterate(SpaceClosure* cl); // Iterate over heap regions, in address order, terminating the // iteration early if the "doHeapRegion" method returns "true". void heap_region_iterate(HeapRegionClosure* blk); // Iterate over heap regions starting with r (or the first region if "r" // is NULL), in address order, terminating early if the "doHeapRegion" // method returns "true". void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk); // As above but starting from the region at index idx. void heap_region_iterate_from(int idx, HeapRegionClosure* blk); HeapRegion* region_at(size_t idx); // Divide the heap region sequence into "chunks" of some size (the number // of regions divided by the number of parallel threads times some // overpartition factor, currently 4). Assumes that this will be called // in parallel by ParallelGCThreads worker threads with discinct worker // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel // calls will use the same "claim_value", and that that claim value is // different from the claim_value of any heap region before the start of // the iteration. Applies "blk->doHeapRegion" to each of the regions, by // attempting to claim the first region in each chunk, and, if // successful, applying the closure to each region in the chunk (and // setting the claim value of the second and subsequent regions of the // chunk.) For now requires that "doHeapRegion" always returns "false", // i.e., that a closure never attempt to abort a traversal. void heap_region_par_iterate_chunked(HeapRegionClosure* blk, int worker, jint claim_value); // It resets all the region claim values to the default. void reset_heap_region_claim_values(); #ifdef ASSERT bool check_heap_region_claim_values(jint claim_value); #endif // ASSERT // Iterate over the regions (if any) in the current collection set. void collection_set_iterate(HeapRegionClosure* blk); // As above but starting from region r void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); // Returns the first (lowest address) compactible space in the heap. virtual CompactibleSpace* first_compactible_space(); // A CollectedHeap will contain some number of spaces. This finds the // space containing a given address, or else returns NULL. virtual Space* space_containing(const void* addr) const; // A G1CollectedHeap will contain some number of heap regions. This // finds the region containing a given address, or else returns NULL. HeapRegion* heap_region_containing(const void* addr) const; // Like the above, but requires "addr" to be in the heap (to avoid a // null-check), and unlike the above, may return an continuing humongous // region. HeapRegion* heap_region_containing_raw(const void* addr) const; // A CollectedHeap is divided into a dense sequence of "blocks"; that is, // each address in the (reserved) heap is a member of exactly // one block. The defining characteristic of a block is that it is // possible to find its size, and thus to progress forward to the next // block. (Blocks may be of different sizes.) Thus, blocks may // represent Java objects, or they might be free blocks in a // free-list-based heap (or subheap), as long as the two kinds are // distinguishable and the size of each is determinable. // Returns the address of the start of the "block" that contains the // address "addr". We say "blocks" instead of "object" since some heaps // may not pack objects densely; a chunk may either be an object or a // non-object. virtual HeapWord* block_start(const void* addr) const; // Requires "addr" to be the start of a chunk, and returns its size. // "addr + size" is required to be the start of a new chunk, or the end // of the active area of the heap. virtual size_t block_size(const HeapWord* addr) const; // Requires "addr" to be the start of a block, and returns "TRUE" iff // the block is an object. virtual bool block_is_obj(const HeapWord* addr) const; // Does this heap support heap inspection? (+PrintClassHistogram) virtual bool supports_heap_inspection() const { return true; } // Section on thread-local allocation buffers (TLABs) // See CollectedHeap for semantics. virtual bool supports_tlab_allocation() const; virtual size_t tlab_capacity(Thread* thr) const; virtual size_t unsafe_max_tlab_alloc(Thread* thr) const; virtual HeapWord* allocate_new_tlab(size_t size); // 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. virtual bool can_elide_tlab_store_barriers() const { // Since G1's TLAB's may, on occasion, come from non-young regions // as well. (Is there a flag controlling that? XXX) return false; } // Can a compiler elide a store barrier when it writes // a permanent oop into the heap? Applies when the compiler // is storing x to the heap, where x->is_perm() is true. virtual bool can_elide_permanent_oop_store_barriers() const { // At least until perm gen collection is also G1-ified, at // which point this should return false. return true; } virtual bool allocs_are_zero_filled(); // The boundary between a "large" and "small" array of primitives, in // words. virtual size_t large_typearray_limit(); // Returns "true" iff the given word_size is "very large". static bool isHumongous(size_t word_size) { return word_size >= VeryLargeInWords; } // Update mod union table with the set of dirty cards. void updateModUnion(); // Set the mod union bits corresponding to the given memRegion. Note // that this is always a safe operation, since it doesn't clear any // bits. void markModUnionRange(MemRegion mr); // Records the fact that a marking phase is no longer in progress. void set_marking_complete() { _mark_in_progress = false; } void set_marking_started() { _mark_in_progress = true; } bool mark_in_progress() { return _mark_in_progress; } // Print the maximum heap capacity. virtual size_t max_capacity() const; virtual jlong millis_since_last_gc(); // Perform any cleanup actions necessary before allowing a verification. virtual void prepare_for_verify(); // Perform verification. // use_prev_marking == true -> use "prev" marking information, // use_prev_marking == false -> use "next" marking information // NOTE: Only the "prev" marking information is guaranteed to be // consistent most of the time, so most calls to this should use // use_prev_marking == true. Currently, there is only one case where // this is called with use_prev_marking == false, which is to verify // the "next" marking information at the end of remark. void verify(bool allow_dirty, bool silent, bool use_prev_marking); // Override; it uses the "prev" marking information virtual void verify(bool allow_dirty, bool silent); // Default behavior by calling print(tty); virtual void print() const; // This calls print_on(st, PrintHeapAtGCExtended). virtual void print_on(outputStream* st) const; // If extended is true, it will print out information for all // regions in the heap by calling print_on_extended(st). virtual void print_on(outputStream* st, bool extended) const; virtual void print_on_extended(outputStream* st) const; virtual void print_gc_threads_on(outputStream* st) const; virtual void gc_threads_do(ThreadClosure* tc) const; // Override void print_tracing_info() const; // If "addr" is a pointer into the (reserved?) heap, returns a positive // number indicating the "arena" within the heap in which "addr" falls. // Or else returns 0. virtual int addr_to_arena_id(void* addr) const; // Convenience function to be used in situations where the heap type can be // asserted to be this type. static G1CollectedHeap* heap(); void empty_young_list(); bool should_set_young_locked(); void set_region_short_lived_locked(HeapRegion* hr); // add appropriate methods for any other surv rate groups void young_list_rs_length_sampling_init() { _young_list->rs_length_sampling_init(); } bool young_list_rs_length_sampling_more() { return _young_list->rs_length_sampling_more(); } void young_list_rs_length_sampling_next() { _young_list->rs_length_sampling_next(); } size_t young_list_sampled_rs_lengths() { return _young_list->sampled_rs_lengths(); } size_t young_list_length() { return _young_list->length(); } size_t young_list_scan_only_length() { return _young_list->scan_only_length(); } HeapRegion* pop_region_from_young_list() { return _young_list->pop_region(); } HeapRegion* young_list_first_region() { return _young_list->first_region(); } // debugging bool check_young_list_well_formed() { return _young_list->check_list_well_formed(); } bool check_young_list_empty(bool ignore_scan_only_list, bool check_sample = true); // *** Stuff related to concurrent marking. It's not clear to me that so // many of these need to be public. // The functions below are helper functions that a subclass of // "CollectedHeap" can use in the implementation of its virtual // functions. // This performs a concurrent marking of the live objects in a // bitmap off to the side. void doConcurrentMark(); // This is called from the marksweep collector which then does // a concurrent mark and verifies that the results agree with // the stop the world marking. void checkConcurrentMark(); void do_sync_mark(); bool isMarkedPrev(oop obj) const; bool isMarkedNext(oop obj) const; // use_prev_marking == true -> use "prev" marking information, // use_prev_marking == false -> use "next" marking information bool is_obj_dead_cond(const oop obj, const HeapRegion* hr, const bool use_prev_marking) const { if (use_prev_marking) { return is_obj_dead(obj, hr); } else { return is_obj_ill(obj, hr); } } // Determine if an object is dead, given the object and also // the region to which the object belongs. An object is dead // iff a) it was not allocated since the last mark and b) it // is not marked. bool is_obj_dead(const oop obj, const HeapRegion* hr) const { return !hr->obj_allocated_since_prev_marking(obj) && !isMarkedPrev(obj); } // This is used when copying an object to survivor space. // If the object is marked live, then we mark the copy live. // If the object is allocated since the start of this mark // cycle, then we mark the copy live. // If the object has been around since the previous mark // phase, and hasn't been marked yet during this phase, // then we don't mark it, we just wait for the // current marking cycle to get to it. // This function returns true when an object has been // around since the previous marking and hasn't yet // been marked during this marking. bool is_obj_ill(const oop obj, const HeapRegion* hr) const { return !hr->obj_allocated_since_next_marking(obj) && !isMarkedNext(obj); } // Determine if an object is dead, given only the object itself. // This will find the region to which the object belongs and // then call the region version of the same function. // Added if it is in permanent gen it isn't dead. // Added if it is NULL it isn't dead. // use_prev_marking == true -> use "prev" marking information, // use_prev_marking == false -> use "next" marking information bool is_obj_dead_cond(const oop obj, const bool use_prev_marking) { if (use_prev_marking) { return is_obj_dead(obj); } else { return is_obj_ill(obj); } } bool is_obj_dead(const oop obj) { const HeapRegion* hr = heap_region_containing(obj); if (hr == NULL) { if (Universe::heap()->is_in_permanent(obj)) return false; else if (obj == NULL) return false; else return true; } else return is_obj_dead(obj, hr); } bool is_obj_ill(const oop obj) { const HeapRegion* hr = heap_region_containing(obj); if (hr == NULL) { if (Universe::heap()->is_in_permanent(obj)) return false; else if (obj == NULL) return false; else return true; } else return is_obj_ill(obj, hr); } // The following is just to alert the verification code // that a full collection has occurred and that the // remembered sets are no longer up to date. bool _full_collection; void set_full_collection() { _full_collection = true;} void clear_full_collection() {_full_collection = false;} bool full_collection() {return _full_collection;} ConcurrentMark* concurrent_mark() const { return _cm; } ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } // The dirty cards region list is used to record a subset of regions // whose cards need clearing. The list if populated during the // remembered set scanning and drained during the card table // cleanup. Although the methods are reentrant, population/draining // phases must not overlap. For synchronization purposes the last // element on the list points to itself. HeapRegion* _dirty_cards_region_list; void push_dirty_cards_region(HeapRegion* hr); HeapRegion* pop_dirty_cards_region(); public: void stop_conc_gc_threads(); // double predict_region_elapsed_time_ms(HeapRegion* hr, bool young); void check_if_region_is_too_expensive(double predicted_time_ms); size_t pending_card_num(); size_t max_pending_card_num(); size_t cards_scanned(); // protected: size_t _max_heap_capacity; // debug_only(static void check_for_valid_allocation_state();) public: // Temporary: call to mark things unimplemented for the G1 heap (e.g., // MemoryService). In productization, we can make this assert false // to catch such places (as well as searching for calls to this...) static void g1_unimplemented(); }; // Local Variables: *** // c-indentation-style: gnu *** // End: ***