--- old/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp 2015-05-13 13:54:25.013066356 +0200 +++ /dev/null 2015-03-18 17:10:38.111854831 +0100 @@ -1,1816 +0,0 @@ -/* - * Copyright (c) 2001, 2015, 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_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP -#define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP - -#include "gc_implementation/concurrentMarkSweep/cmsOopClosures.hpp" -#include "gc_implementation/shared/gcHeapSummary.hpp" -#include "gc_implementation/shared/gSpaceCounters.hpp" -#include "gc_implementation/shared/gcStats.hpp" -#include "gc_implementation/shared/gcWhen.hpp" -#include "gc_implementation/shared/generationCounters.hpp" -#include "memory/cardGeneration.hpp" -#include "memory/freeBlockDictionary.hpp" -#include "memory/iterator.hpp" -#include "memory/space.hpp" -#include "memory/virtualspace.hpp" -#include "runtime/mutexLocker.hpp" -#include "services/memoryService.hpp" -#include "utilities/bitMap.hpp" -#include "utilities/stack.hpp" -#include "utilities/taskqueue.hpp" -#include "utilities/yieldingWorkgroup.hpp" - -// ConcurrentMarkSweepGeneration is in support of a concurrent -// mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker -// style. We assume, for now, that this generation is always the -// seniormost generation and for simplicity -// in the first implementation, that this generation is a single compactible -// space. Neither of these restrictions appears essential, and will be -// relaxed in the future when more time is available to implement the -// greater generality (and there's a need for it). -// -// Concurrent mode failures are currently handled by -// means of a sliding mark-compact. - -class AdaptiveSizePolicy; -class CMSCollector; -class CMSConcMarkingTask; -class CMSGCAdaptivePolicyCounters; -class CMSTracer; -class ConcurrentGCTimer; -class ConcurrentMarkSweepGeneration; -class ConcurrentMarkSweepPolicy; -class ConcurrentMarkSweepThread; -class CompactibleFreeListSpace; -class FreeChunk; -class ParNewGeneration; -class PromotionInfo; -class ScanMarkedObjectsAgainCarefullyClosure; -class TenuredGeneration; -class SerialOldTracer; - -// A generic CMS bit map. It's the basis for both the CMS marking bit map -// as well as for the mod union table (in each case only a subset of the -// methods are used). This is essentially a wrapper around the BitMap class, -// with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, -// we have _shifter == 0. and for the mod union table we have -// shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) -// XXX 64-bit issues in BitMap? -class CMSBitMap VALUE_OBJ_CLASS_SPEC { - friend class VMStructs; - - HeapWord* _bmStartWord; // base address of range covered by map - size_t _bmWordSize; // map size (in #HeapWords covered) - const int _shifter; // shifts to convert HeapWord to bit position - VirtualSpace _virtual_space; // underlying the bit map - BitMap _bm; // the bit map itself - public: - Mutex* const _lock; // mutex protecting _bm; - - public: - // constructor - CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); - - // allocates the actual storage for the map - bool allocate(MemRegion mr); - // field getter - Mutex* lock() const { return _lock; } - // locking verifier convenience function - void assert_locked() const PRODUCT_RETURN; - - // inquiries - HeapWord* startWord() const { return _bmStartWord; } - size_t sizeInWords() const { return _bmWordSize; } - size_t sizeInBits() const { return _bm.size(); } - // the following is one past the last word in space - HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } - - // reading marks - bool isMarked(HeapWord* addr) const; - bool par_isMarked(HeapWord* addr) const; // do not lock checks - bool isUnmarked(HeapWord* addr) const; - bool isAllClear() const; - - // writing marks - void mark(HeapWord* addr); - // For marking by parallel GC threads; - // returns true if we did, false if another thread did - bool par_mark(HeapWord* addr); - - void mark_range(MemRegion mr); - void par_mark_range(MemRegion mr); - void mark_large_range(MemRegion mr); - void par_mark_large_range(MemRegion mr); - void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. - void clear_range(MemRegion mr); - void par_clear_range(MemRegion mr); - void clear_large_range(MemRegion mr); - void par_clear_large_range(MemRegion mr); - void clear_all(); - void clear_all_incrementally(); // Not yet implemented!! - - NOT_PRODUCT( - // checks the memory region for validity - void region_invariant(MemRegion mr); - ) - - // iteration - void iterate(BitMapClosure* cl) { - _bm.iterate(cl); - } - void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); - void dirty_range_iterate_clear(MemRegionClosure* cl); - void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); - - // auxiliary support for iteration - HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; - HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, - HeapWord* end_addr) const; - HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; - HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, - HeapWord* end_addr) const; - MemRegion getAndClearMarkedRegion(HeapWord* addr); - MemRegion getAndClearMarkedRegion(HeapWord* start_addr, - HeapWord* end_addr); - - // conversion utilities - HeapWord* offsetToHeapWord(size_t offset) const; - size_t heapWordToOffset(HeapWord* addr) const; - size_t heapWordDiffToOffsetDiff(size_t diff) const; - - void print_on_error(outputStream* st, const char* prefix) const; - - // debugging - // is this address range covered by the bit-map? - NOT_PRODUCT( - bool covers(MemRegion mr) const; - bool covers(HeapWord* start, size_t size = 0) const; - ) - void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; -}; - -// Represents a marking stack used by the CMS collector. -// Ideally this should be GrowableArray<> just like MSC's marking stack(s). -class CMSMarkStack: public CHeapObj { - friend class CMSCollector; // To get at expansion stats further below. - - VirtualSpace _virtual_space; // Space for the stack - oop* _base; // Bottom of stack - size_t _index; // One more than last occupied index - size_t _capacity; // Max #elements - Mutex _par_lock; // An advisory lock used in case of parallel access - NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run - - protected: - size_t _hit_limit; // We hit max stack size limit - size_t _failed_double; // We failed expansion before hitting limit - - public: - CMSMarkStack(): - _par_lock(Mutex::event, "CMSMarkStack._par_lock", true, - Monitor::_safepoint_check_never), - _hit_limit(0), - _failed_double(0) {} - - bool allocate(size_t size); - - size_t capacity() const { return _capacity; } - - oop pop() { - if (!isEmpty()) { - return _base[--_index] ; - } - return NULL; - } - - bool push(oop ptr) { - if (isFull()) { - return false; - } else { - _base[_index++] = ptr; - NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); - return true; - } - } - - bool isEmpty() const { return _index == 0; } - bool isFull() const { - assert(_index <= _capacity, "buffer overflow"); - return _index == _capacity; - } - - size_t length() { return _index; } - - // "Parallel versions" of some of the above - oop par_pop() { - // lock and pop - MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); - return pop(); - } - - bool par_push(oop ptr) { - // lock and push - MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); - return push(ptr); - } - - // Forcibly reset the stack, losing all of its contents. - void reset() { - _index = 0; - } - - // Expand the stack, typically in response to an overflow condition. - void expand(); - - // Compute the least valued stack element. - oop least_value(HeapWord* low) { - oop least = (oop)low; - for (size_t i = 0; i < _index; i++) { - least = MIN2(least, _base[i]); - } - return least; - } - - // Exposed here to allow stack expansion in || case. - Mutex* par_lock() { return &_par_lock; } -}; - -class CardTableRS; -class CMSParGCThreadState; - -class ModUnionClosure: public MemRegionClosure { - protected: - CMSBitMap* _t; - public: - ModUnionClosure(CMSBitMap* t): _t(t) { } - void do_MemRegion(MemRegion mr); -}; - -class ModUnionClosurePar: public ModUnionClosure { - public: - ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } - void do_MemRegion(MemRegion mr); -}; - -// Survivor Chunk Array in support of parallelization of -// Survivor Space rescan. -class ChunkArray: public CHeapObj { - size_t _index; - size_t _capacity; - size_t _overflows; - HeapWord** _array; // storage for array - - public: - ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} - ChunkArray(HeapWord** a, size_t c): - _index(0), _capacity(c), _overflows(0), _array(a) {} - - HeapWord** array() { return _array; } - void set_array(HeapWord** a) { _array = a; } - - size_t capacity() { return _capacity; } - void set_capacity(size_t c) { _capacity = c; } - - size_t end() { - assert(_index <= capacity(), - err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", - _index, _capacity)); - return _index; - } // exclusive - - HeapWord* nth(size_t n) { - assert(n < end(), "Out of bounds access"); - return _array[n]; - } - - void reset() { - _index = 0; - if (_overflows > 0 && PrintCMSStatistics > 1) { - warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", - _capacity, _overflows); - } - _overflows = 0; - } - - void record_sample(HeapWord* p, size_t sz) { - // For now we do not do anything with the size - if (_index < _capacity) { - _array[_index++] = p; - } else { - ++_overflows; - assert(_index == _capacity, - err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT - "): out of bounds at overflow#" SIZE_FORMAT, - _index, _capacity, _overflows)); - } - } -}; - -// -// Timing, allocation and promotion statistics for gc scheduling and incremental -// mode pacing. Most statistics are exponential averages. -// -class CMSStats VALUE_OBJ_CLASS_SPEC { - private: - ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. - - // The following are exponential averages with factor alpha: - // avg = (100 - alpha) * avg + alpha * cur_sample - // - // The durations measure: end_time[n] - start_time[n] - // The periods measure: start_time[n] - start_time[n-1] - // - // The cms period and duration include only concurrent collections; time spent - // in foreground cms collections due to System.gc() or because of a failure to - // keep up are not included. - // - // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the - // real value, but is used only after the first period. A value of 100 is - // used for the first sample so it gets the entire weight. - unsigned int _saved_alpha; // 0-100 - unsigned int _gc0_alpha; - unsigned int _cms_alpha; - - double _gc0_duration; - double _gc0_period; - size_t _gc0_promoted; // bytes promoted per gc0 - double _cms_duration; - double _cms_duration_pre_sweep; // time from initiation to start of sweep - double _cms_period; - size_t _cms_allocated; // bytes of direct allocation per gc0 period - - // Timers. - elapsedTimer _cms_timer; - TimeStamp _gc0_begin_time; - TimeStamp _cms_begin_time; - TimeStamp _cms_end_time; - - // Snapshots of the amount used in the CMS generation. - size_t _cms_used_at_gc0_begin; - size_t _cms_used_at_gc0_end; - size_t _cms_used_at_cms_begin; - - // Used to prevent the duty cycle from being reduced in the middle of a cms - // cycle. - bool _allow_duty_cycle_reduction; - - enum { - _GC0_VALID = 0x1, - _CMS_VALID = 0x2, - _ALL_VALID = _GC0_VALID | _CMS_VALID - }; - - unsigned int _valid_bits; - - protected: - // In support of adjusting of cms trigger ratios based on history - // of concurrent mode failure. - double cms_free_adjustment_factor(size_t free) const; - void adjust_cms_free_adjustment_factor(bool fail, size_t free); - - public: - CMSStats(ConcurrentMarkSweepGeneration* cms_gen, - unsigned int alpha = CMSExpAvgFactor); - - // Whether or not the statistics contain valid data; higher level statistics - // cannot be called until this returns true (they require at least one young - // gen and one cms cycle to have completed). - bool valid() const; - - // Record statistics. - void record_gc0_begin(); - void record_gc0_end(size_t cms_gen_bytes_used); - void record_cms_begin(); - void record_cms_end(); - - // Allow management of the cms timer, which must be stopped/started around - // yield points. - elapsedTimer& cms_timer() { return _cms_timer; } - void start_cms_timer() { _cms_timer.start(); } - void stop_cms_timer() { _cms_timer.stop(); } - - // Basic statistics; units are seconds or bytes. - double gc0_period() const { return _gc0_period; } - double gc0_duration() const { return _gc0_duration; } - size_t gc0_promoted() const { return _gc0_promoted; } - double cms_period() const { return _cms_period; } - double cms_duration() const { return _cms_duration; } - size_t cms_allocated() const { return _cms_allocated; } - - size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} - - // Seconds since the last background cms cycle began or ended. - double cms_time_since_begin() const; - double cms_time_since_end() const; - - // Higher level statistics--caller must check that valid() returns true before - // calling. - - // Returns bytes promoted per second of wall clock time. - double promotion_rate() const; - - // Returns bytes directly allocated per second of wall clock time. - double cms_allocation_rate() const; - - // Rate at which space in the cms generation is being consumed (sum of the - // above two). - double cms_consumption_rate() const; - - // Returns an estimate of the number of seconds until the cms generation will - // fill up, assuming no collection work is done. - double time_until_cms_gen_full() const; - - // Returns an estimate of the number of seconds remaining until - // the cms generation collection should start. - double time_until_cms_start() const; - - // End of higher level statistics. - - // Debugging. - void print_on(outputStream* st) const PRODUCT_RETURN; - void print() const { print_on(gclog_or_tty); } -}; - -// A closure related to weak references processing which -// we embed in the CMSCollector, since we need to pass -// it to the reference processor for secondary filtering -// of references based on reachability of referent; -// see role of _is_alive_non_header closure in the -// ReferenceProcessor class. -// For objects in the CMS generation, this closure checks -// if the object is "live" (reachable). Used in weak -// reference processing. -class CMSIsAliveClosure: public BoolObjectClosure { - const MemRegion _span; - const CMSBitMap* _bit_map; - - friend class CMSCollector; - public: - CMSIsAliveClosure(MemRegion span, - CMSBitMap* bit_map): - _span(span), - _bit_map(bit_map) { - assert(!span.is_empty(), "Empty span could spell trouble"); - } - - bool do_object_b(oop obj); -}; - - -// Implements AbstractRefProcTaskExecutor for CMS. -class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { -public: - - CMSRefProcTaskExecutor(CMSCollector& collector) - : _collector(collector) - { } - - // Executes a task using worker threads. - virtual void execute(ProcessTask& task); - virtual void execute(EnqueueTask& task); -private: - CMSCollector& _collector; -}; - - -class CMSCollector: public CHeapObj { - friend class VMStructs; - friend class ConcurrentMarkSweepThread; - friend class ConcurrentMarkSweepGeneration; - friend class CompactibleFreeListSpace; - friend class CMSParMarkTask; - friend class CMSParInitialMarkTask; - friend class CMSParRemarkTask; - friend class CMSConcMarkingTask; - friend class CMSRefProcTaskProxy; - friend class CMSRefProcTaskExecutor; - friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden - friend class SurvivorSpacePrecleanClosure; // --- ditto ------- - friend class PushOrMarkClosure; // to access _restart_addr - friend class Par_PushOrMarkClosure; // to access _restart_addr - friend class MarkFromRootsClosure; // -- ditto -- - // ... and for clearing cards - friend class Par_MarkFromRootsClosure; // to access _restart_addr - // ... and for clearing cards - friend class Par_ConcMarkingClosure; // to access _restart_addr etc. - friend class MarkFromRootsVerifyClosure; // to access _restart_addr - friend class PushAndMarkVerifyClosure; // -- ditto -- - friend class MarkRefsIntoAndScanClosure; // to access _overflow_list - friend class PushAndMarkClosure; // -- ditto -- - friend class Par_PushAndMarkClosure; // -- ditto -- - friend class CMSKeepAliveClosure; // -- ditto -- - friend class CMSDrainMarkingStackClosure; // -- ditto -- - friend class CMSInnerParMarkAndPushClosure; // -- ditto -- - NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list - friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait - friend class VM_CMS_Operation; - friend class VM_CMS_Initial_Mark; - friend class VM_CMS_Final_Remark; - friend class TraceCMSMemoryManagerStats; - - private: - jlong _time_of_last_gc; - void update_time_of_last_gc(jlong now) { - _time_of_last_gc = now; - } - - OopTaskQueueSet* _task_queues; - - // Overflow list of grey objects, threaded through mark-word - // Manipulated with CAS in the parallel/multi-threaded case. - oop _overflow_list; - // The following array-pair keeps track of mark words - // displaced for accommodating overflow list above. - // This code will likely be revisited under RFE#4922830. - Stack _preserved_oop_stack; - Stack _preserved_mark_stack; - - int* _hash_seed; - - // In support of multi-threaded concurrent phases - YieldingFlexibleWorkGang* _conc_workers; - - // Performance Counters - CollectorCounters* _gc_counters; - - // Initialization Errors - bool _completed_initialization; - - // In support of ExplicitGCInvokesConcurrent - static bool _full_gc_requested; - static GCCause::Cause _full_gc_cause; - unsigned int _collection_count_start; - - // Should we unload classes this concurrent cycle? - bool _should_unload_classes; - unsigned int _concurrent_cycles_since_last_unload; - unsigned int concurrent_cycles_since_last_unload() const { - return _concurrent_cycles_since_last_unload; - } - // Did we (allow) unload classes in the previous concurrent cycle? - bool unloaded_classes_last_cycle() const { - return concurrent_cycles_since_last_unload() == 0; - } - // Root scanning options for perm gen - int _roots_scanning_options; - int roots_scanning_options() const { return _roots_scanning_options; } - void add_root_scanning_option(int o) { _roots_scanning_options |= o; } - void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } - - // Verification support - CMSBitMap _verification_mark_bm; - void verify_after_remark_work_1(); - void verify_after_remark_work_2(); - - // True if any verification flag is on. - bool _verifying; - bool verifying() const { return _verifying; } - void set_verifying(bool v) { _verifying = v; } - - // Collector policy - ConcurrentMarkSweepPolicy* _collector_policy; - ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } - - void set_did_compact(bool v); - - // XXX Move these to CMSStats ??? FIX ME !!! - elapsedTimer _inter_sweep_timer; // Time between sweeps - elapsedTimer _intra_sweep_timer; // Time _in_ sweeps - // Padded decaying average estimates of the above - AdaptivePaddedAverage _inter_sweep_estimate; - AdaptivePaddedAverage _intra_sweep_estimate; - - CMSTracer* _gc_tracer_cm; - ConcurrentGCTimer* _gc_timer_cm; - - bool _cms_start_registered; - - GCHeapSummary _last_heap_summary; - MetaspaceSummary _last_metaspace_summary; - - void register_gc_start(GCCause::Cause cause); - void register_gc_end(); - void save_heap_summary(); - void report_heap_summary(GCWhen::Type when); - - protected: - ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) - MemRegion _span; // Span covering above two - CardTableRS* _ct; // Card table - - // CMS marking support structures - CMSBitMap _markBitMap; - CMSBitMap _modUnionTable; - CMSMarkStack _markStack; - - HeapWord* _restart_addr; // In support of marking stack overflow - void lower_restart_addr(HeapWord* low); - - // Counters in support of marking stack / work queue overflow handling: - // a non-zero value indicates certain types of overflow events during - // the current CMS cycle and could lead to stack resizing efforts at - // an opportune future time. - size_t _ser_pmc_preclean_ovflw; - size_t _ser_pmc_remark_ovflw; - size_t _par_pmc_remark_ovflw; - size_t _ser_kac_preclean_ovflw; - size_t _ser_kac_ovflw; - size_t _par_kac_ovflw; - NOT_PRODUCT(ssize_t _num_par_pushes;) - - // ("Weak") Reference processing support. - ReferenceProcessor* _ref_processor; - CMSIsAliveClosure _is_alive_closure; - // Keep this textually after _markBitMap and _span; c'tor dependency. - - ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work - ModUnionClosurePar _modUnionClosurePar; - - // CMS abstract state machine - // initial_state: Idling - // next_state(Idling) = {Marking} - // next_state(Marking) = {Precleaning, Sweeping} - // next_state(Precleaning) = {AbortablePreclean, FinalMarking} - // next_state(AbortablePreclean) = {FinalMarking} - // next_state(FinalMarking) = {Sweeping} - // next_state(Sweeping) = {Resizing} - // next_state(Resizing) = {Resetting} - // next_state(Resetting) = {Idling} - // The numeric values below are chosen so that: - // . _collectorState <= Idling == post-sweep && pre-mark - // . _collectorState in (Idling, Sweeping) == {initial,final}marking || - // precleaning || abortablePrecleanb - public: - enum CollectorState { - Resizing = 0, - Resetting = 1, - Idling = 2, - InitialMarking = 3, - Marking = 4, - Precleaning = 5, - AbortablePreclean = 6, - FinalMarking = 7, - Sweeping = 8 - }; - protected: - static CollectorState _collectorState; - - // State related to prologue/epilogue invocation for my generations - bool _between_prologue_and_epilogue; - - // Signaling/State related to coordination between fore- and background GC - // Note: When the baton has been passed from background GC to foreground GC, - // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. - static bool _foregroundGCIsActive; // true iff foreground collector is active or - // wants to go active - static bool _foregroundGCShouldWait; // true iff background GC is active and has not - // yet passed the baton to the foreground GC - - // Support for CMSScheduleRemark (abortable preclean) - bool _abort_preclean; - bool _start_sampling; - - int _numYields; - size_t _numDirtyCards; - size_t _sweep_count; - - // Occupancy used for bootstrapping stats - double _bootstrap_occupancy; - - // Timer - elapsedTimer _timer; - - // Timing, allocation and promotion statistics, used for scheduling. - CMSStats _stats; - - enum CMS_op_type { - CMS_op_checkpointRootsInitial, - CMS_op_checkpointRootsFinal - }; - - void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); - bool stop_world_and_do(CMS_op_type op); - - OopTaskQueueSet* task_queues() { return _task_queues; } - int* hash_seed(int i) { return &_hash_seed[i]; } - YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } - - // Support for parallelizing Eden rescan in CMS remark phase - void sample_eden(); // ... sample Eden space top - - private: - // Support for parallelizing young gen rescan in CMS remark phase - ParNewGeneration* _young_gen; // the younger gen - - HeapWord** _top_addr; // ... Top of Eden - HeapWord** _end_addr; // ... End of Eden - Mutex* _eden_chunk_lock; - HeapWord** _eden_chunk_array; // ... Eden partitioning array - size_t _eden_chunk_index; // ... top (exclusive) of array - size_t _eden_chunk_capacity; // ... max entries in array - - // Support for parallelizing survivor space rescan - HeapWord** _survivor_chunk_array; - size_t _survivor_chunk_index; - size_t _survivor_chunk_capacity; - size_t* _cursor; - ChunkArray* _survivor_plab_array; - - // A bounded minimum size of PLABs, should not return too small values since - // this will affect the size of the data structures used for parallel young gen rescan - size_t plab_sample_minimum_size(); - - // Support for marking stack overflow handling - bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); - bool par_take_from_overflow_list(size_t num, - OopTaskQueue* to_work_q, - int no_of_gc_threads); - void push_on_overflow_list(oop p); - void par_push_on_overflow_list(oop p); - // The following is, obviously, not, in general, "MT-stable" - bool overflow_list_is_empty() const; - - void preserve_mark_if_necessary(oop p); - void par_preserve_mark_if_necessary(oop p); - void preserve_mark_work(oop p, markOop m); - void restore_preserved_marks_if_any(); - NOT_PRODUCT(bool no_preserved_marks() const;) - // In support of testing overflow code - NOT_PRODUCT(int _overflow_counter;) - NOT_PRODUCT(bool simulate_overflow();) // Sequential - NOT_PRODUCT(bool par_simulate_overflow();) // MT version - - // CMS work methods - void checkpointRootsInitialWork(); // Initial checkpoint work - - // A return value of false indicates failure due to stack overflow - bool markFromRootsWork(); // Concurrent marking work - - public: // FIX ME!!! only for testing - bool do_marking_st(); // Single-threaded marking - bool do_marking_mt(); // Multi-threaded marking - - private: - - // Concurrent precleaning work - size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, - ScanMarkedObjectsAgainCarefullyClosure* cl); - size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, - ScanMarkedObjectsAgainCarefullyClosure* cl); - // Does precleaning work, returning a quantity indicative of - // the amount of "useful work" done. - size_t preclean_work(bool clean_refs, bool clean_survivors); - void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); - void abortable_preclean(); // Preclean while looking for possible abort - void initialize_sequential_subtasks_for_young_gen_rescan(int i); - // Helper function for above; merge-sorts the per-thread plab samples - void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); - // Resets (i.e. clears) the per-thread plab sample vectors - void reset_survivor_plab_arrays(); - - // Final (second) checkpoint work - void checkpointRootsFinalWork(); - // Work routine for parallel version of remark - void do_remark_parallel(); - // Work routine for non-parallel version of remark - void do_remark_non_parallel(); - // Reference processing work routine (during second checkpoint) - void refProcessingWork(); - - // Concurrent sweeping work - void sweepWork(ConcurrentMarkSweepGeneration* gen); - - // (Concurrent) resetting of support data structures - void reset(bool concurrent); - - // Clear _expansion_cause fields of constituent generations - void clear_expansion_cause(); - - // An auxiliary method used to record the ends of - // used regions of each generation to limit the extent of sweep - void save_sweep_limits(); - - // A work method used by the foreground collector to do - // a mark-sweep-compact. - void do_compaction_work(bool clear_all_soft_refs); - - // Work methods for reporting concurrent mode interruption or failure - bool is_external_interruption(); - void report_concurrent_mode_interruption(); - - // If the background GC is active, acquire control from the background - // GC and do the collection. - void acquire_control_and_collect(bool full, bool clear_all_soft_refs); - - // For synchronizing passing of control from background to foreground - // GC. waitForForegroundGC() is called by the background - // collector. It if had to wait for a foreground collection, - // it returns true and the background collection should assume - // that the collection was finished by the foreground - // collector. - bool waitForForegroundGC(); - - size_t block_size_using_printezis_bits(HeapWord* addr) const; - size_t block_size_if_printezis_bits(HeapWord* addr) const; - HeapWord* next_card_start_after_block(HeapWord* addr) const; - - void setup_cms_unloading_and_verification_state(); - public: - CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, - CardTableRS* ct, - ConcurrentMarkSweepPolicy* cp); - ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } - - ReferenceProcessor* ref_processor() { return _ref_processor; } - void ref_processor_init(); - - Mutex* bitMapLock() const { return _markBitMap.lock(); } - static CollectorState abstract_state() { return _collectorState; } - - bool should_abort_preclean() const; // Whether preclean should be aborted. - size_t get_eden_used() const; - size_t get_eden_capacity() const; - - ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } - - // Locking checks - NOT_PRODUCT(static bool have_cms_token();) - - bool shouldConcurrentCollect(); - - void collect(bool full, - bool clear_all_soft_refs, - size_t size, - bool tlab); - void collect_in_background(GCCause::Cause cause); - - // In support of ExplicitGCInvokesConcurrent - static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); - // Should we unload classes in a particular concurrent cycle? - bool should_unload_classes() const { - return _should_unload_classes; - } - void update_should_unload_classes(); - - void direct_allocated(HeapWord* start, size_t size); - - // Object is dead if not marked and current phase is sweeping. - bool is_dead_obj(oop obj) const; - - // After a promotion (of "start"), do any necessary marking. - // If "par", then it's being done by a parallel GC thread. - // The last two args indicate if we need precise marking - // and if so the size of the object so it can be dirtied - // in its entirety. - void promoted(bool par, HeapWord* start, - bool is_obj_array, size_t obj_size); - - void getFreelistLocks() const; - void releaseFreelistLocks() const; - bool haveFreelistLocks() const; - - // Adjust size of underlying generation - void compute_new_size(); - - // GC prologue and epilogue - void gc_prologue(bool full); - void gc_epilogue(bool full); - - jlong time_of_last_gc(jlong now) { - if (_collectorState <= Idling) { - // gc not in progress - return _time_of_last_gc; - } else { - // collection in progress - return now; - } - } - - // Support for parallel remark of survivor space - void* get_data_recorder(int thr_num); - void sample_eden_chunk(); - - CMSBitMap* markBitMap() { return &_markBitMap; } - void directAllocated(HeapWord* start, size_t size); - - // Main CMS steps and related support - void checkpointRootsInitial(); - bool markFromRoots(); // a return value of false indicates failure - // due to stack overflow - void preclean(); - void checkpointRootsFinal(); - void sweep(); - - // Check that the currently executing thread is the expected - // one (foreground collector or background collector). - static void check_correct_thread_executing() PRODUCT_RETURN; - - bool is_cms_reachable(HeapWord* addr); - - // Performance Counter Support - CollectorCounters* counters() { return _gc_counters; } - - // Timer stuff - void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } - void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } - void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } - double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } - - int yields() { return _numYields; } - void resetYields() { _numYields = 0; } - void incrementYields() { _numYields++; } - void resetNumDirtyCards() { _numDirtyCards = 0; } - void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } - size_t numDirtyCards() { return _numDirtyCards; } - - static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } - static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } - static bool foregroundGCIsActive() { return _foregroundGCIsActive; } - static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } - size_t sweep_count() const { return _sweep_count; } - void increment_sweep_count() { _sweep_count++; } - - // Timers/stats for gc scheduling and incremental mode pacing. - CMSStats& stats() { return _stats; } - - // Adaptive size policy - AdaptiveSizePolicy* size_policy(); - - static void print_on_error(outputStream* st); - - // Debugging - void verify(); - bool verify_after_remark(bool silent = VerifySilently); - void verify_ok_to_terminate() const PRODUCT_RETURN; - void verify_work_stacks_empty() const PRODUCT_RETURN; - void verify_overflow_empty() const PRODUCT_RETURN; - - // Convenience methods in support of debugging - static const size_t skip_header_HeapWords() PRODUCT_RETURN0; - HeapWord* block_start(const void* p) const PRODUCT_RETURN0; - - // Accessors - CMSMarkStack* verification_mark_stack() { return &_markStack; } - CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } - - // Initialization errors - bool completed_initialization() { return _completed_initialization; } - - void print_eden_and_survivor_chunk_arrays(); -}; - -class CMSExpansionCause : public AllStatic { - public: - enum Cause { - _no_expansion, - _satisfy_free_ratio, - _satisfy_promotion, - _satisfy_allocation, - _allocate_par_lab, - _allocate_par_spooling_space, - _adaptive_size_policy - }; - // Return a string describing the cause of the expansion. - static const char* to_string(CMSExpansionCause::Cause cause); -}; - -class ConcurrentMarkSweepGeneration: public CardGeneration { - friend class VMStructs; - friend class ConcurrentMarkSweepThread; - friend class ConcurrentMarkSweep; - friend class CMSCollector; - protected: - static CMSCollector* _collector; // the collector that collects us - CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) - - // Performance Counters - GenerationCounters* _gen_counters; - GSpaceCounters* _space_counters; - - // Words directly allocated, used by CMSStats. - size_t _direct_allocated_words; - - // Non-product stat counters - NOT_PRODUCT( - size_t _numObjectsPromoted; - size_t _numWordsPromoted; - size_t _numObjectsAllocated; - size_t _numWordsAllocated; - ) - - // Used for sizing decisions - bool _incremental_collection_failed; - bool incremental_collection_failed() { - return _incremental_collection_failed; - } - void set_incremental_collection_failed() { - _incremental_collection_failed = true; - } - void clear_incremental_collection_failed() { - _incremental_collection_failed = false; - } - - // accessors - void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} - CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } - - // Accessing spaces - CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } - - private: - // For parallel young-gen GC support. - CMSParGCThreadState** _par_gc_thread_states; - - // Reason generation was expanded - CMSExpansionCause::Cause _expansion_cause; - - // In support of MinChunkSize being larger than min object size - const double _dilatation_factor; - - // True if a compacting collection was done. - bool _did_compact; - bool did_compact() { return _did_compact; } - - // Fraction of current occupancy at which to start a CMS collection which - // will collect this generation (at least). - double _initiating_occupancy; - - protected: - // Shrink generation by specified size (returns false if unable to shrink) - void shrink_free_list_by(size_t bytes); - - // Update statistics for GC - virtual void update_gc_stats(int level, bool full); - - // Maximum available space in the generation (including uncommitted) - // space. - size_t max_available() const; - - // getter and initializer for _initiating_occupancy field. - double initiating_occupancy() const { return _initiating_occupancy; } - void init_initiating_occupancy(intx io, uintx tr); - - void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); - - void assert_correct_size_change_locking(); - - public: - ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, - int level, CardTableRS* ct, - bool use_adaptive_freelists, - FreeBlockDictionary::DictionaryChoice); - - // Accessors - CMSCollector* collector() const { return _collector; } - static void set_collector(CMSCollector* collector) { - assert(_collector == NULL, "already set"); - _collector = collector; - } - CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } - - Mutex* freelistLock() const; - - virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } - - void set_did_compact(bool v) { _did_compact = v; } - - bool refs_discovery_is_atomic() const { return false; } - bool refs_discovery_is_mt() const { - // Note: CMS does MT-discovery during the parallel-remark - // phases. Use ReferenceProcessorMTMutator to make refs - // discovery MT-safe during such phases or other parallel - // discovery phases in the future. This may all go away - // if/when we decide that refs discovery is sufficiently - // rare that the cost of the CAS's involved is in the - // noise. That's a measurement that should be done, and - // the code simplified if that turns out to be the case. - return ConcGCThreads > 1; - } - - // Override - virtual void ref_processor_init(); - - void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } - - // Space enquiries - double occupancy() const { return ((double)used())/((double)capacity()); } - size_t contiguous_available() const; - size_t unsafe_max_alloc_nogc() const; - - // over-rides - MemRegion used_region_at_save_marks() const; - - // Does a "full" (forced) collection invoked on this generation collect - // all younger generations as well? Note that the second conjunct is a - // hack to allow the collection of the younger gen first if the flag is - // set. - virtual bool full_collects_younger_generations() const { - return !ScavengeBeforeFullGC; - } - - // Adjust quantities in the generation affected by - // the compaction. - void reset_after_compaction(); - - // Allocation support - HeapWord* allocate(size_t size, bool tlab); - HeapWord* have_lock_and_allocate(size_t size, bool tlab); - oop promote(oop obj, size_t obj_size); - HeapWord* par_allocate(size_t size, bool tlab) { - return allocate(size, tlab); - } - - - // Used by CMSStats to track direct allocation. The value is sampled and - // reset after each young gen collection. - size_t direct_allocated_words() const { return _direct_allocated_words; } - void reset_direct_allocated_words() { _direct_allocated_words = 0; } - - // Overrides for parallel promotion. - virtual oop par_promote(int thread_num, - oop obj, markOop m, size_t word_sz); - virtual void par_promote_alloc_done(int thread_num); - virtual void par_oop_since_save_marks_iterate_done(int thread_num); - - virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; - - // Inform this (non-young) generation that a promotion failure was - // encountered during a collection of a younger generation that - // promotes into this generation. - virtual void promotion_failure_occurred(); - - bool should_collect(bool full, size_t size, bool tlab); - virtual bool should_concurrent_collect() const; - virtual bool is_too_full() const; - void collect(bool full, - bool clear_all_soft_refs, - size_t size, - bool tlab); - - HeapWord* expand_and_allocate(size_t word_size, - bool tlab, - bool parallel = false); - - // GC prologue and epilogue - void gc_prologue(bool full); - void gc_prologue_work(bool full, bool registerClosure, - ModUnionClosure* modUnionClosure); - void gc_epilogue(bool full); - void gc_epilogue_work(bool full); - - // Time since last GC of this generation - jlong time_of_last_gc(jlong now) { - return collector()->time_of_last_gc(now); - } - void update_time_of_last_gc(jlong now) { - collector()-> update_time_of_last_gc(now); - } - - // Allocation failure - void shrink(size_t bytes); - HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); - bool expand_and_ensure_spooling_space(PromotionInfo* promo); - - // Iteration support and related enquiries - void save_marks(); - bool no_allocs_since_save_marks(); - - // Iteration support specific to CMS generations - void save_sweep_limit(); - - // More iteration support - virtual void oop_iterate(ExtendedOopClosure* cl); - virtual void safe_object_iterate(ObjectClosure* cl); - virtual void object_iterate(ObjectClosure* cl); - - // Need to declare the full complement of closures, whether we'll - // override them or not, or get message from the compiler: - // oop_since_save_marks_iterate_nv hides virtual function... - #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ - void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); - ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) - - // Smart allocation XXX -- move to CFLSpace? - void setNearLargestChunk(); - bool isNearLargestChunk(HeapWord* addr); - - // Get the chunk at the end of the space. Delegates to - // the space. - FreeChunk* find_chunk_at_end(); - - void post_compact(); - - // Debugging - void prepare_for_verify(); - void verify(); - void print_statistics() PRODUCT_RETURN; - - // Performance Counters support - virtual void update_counters(); - virtual void update_counters(size_t used); - void initialize_performance_counters(); - CollectorCounters* counters() { return collector()->counters(); } - - // Support for parallel remark of survivor space - void* get_data_recorder(int thr_num) { - //Delegate to collector - return collector()->get_data_recorder(thr_num); - } - void sample_eden_chunk() { - //Delegate to collector - return collector()->sample_eden_chunk(); - } - - // Printing - const char* name() const; - virtual const char* short_name() const { return "CMS"; } - void print() const; - void printOccupancy(const char* s); - - // Resize the generation after a compacting GC. The - // generation can be treated as a contiguous space - // after the compaction. - virtual void compute_new_size(); - // Resize the generation after a non-compacting - // collection. - void compute_new_size_free_list(); -}; - -// -// Closures of various sorts used by CMS to accomplish its work -// - -// This closure is used to do concurrent marking from the roots -// following the first checkpoint. -class MarkFromRootsClosure: public BitMapClosure { - CMSCollector* _collector; - MemRegion _span; - CMSBitMap* _bitMap; - CMSBitMap* _mut; - CMSMarkStack* _markStack; - bool _yield; - int _skipBits; - HeapWord* _finger; - HeapWord* _threshold; - DEBUG_ONLY(bool _verifying;) - - public: - MarkFromRootsClosure(CMSCollector* collector, MemRegion span, - CMSBitMap* bitMap, - CMSMarkStack* markStack, - bool should_yield, bool verifying = false); - bool do_bit(size_t offset); - void reset(HeapWord* addr); - inline void do_yield_check(); - - private: - void scanOopsInOop(HeapWord* ptr); - void do_yield_work(); -}; - -// This closure is used to do concurrent multi-threaded -// marking from the roots following the first checkpoint. -// XXX This should really be a subclass of The serial version -// above, but i have not had the time to refactor things cleanly. -class Par_MarkFromRootsClosure: public BitMapClosure { - CMSCollector* _collector; - MemRegion _whole_span; - MemRegion _span; - CMSBitMap* _bit_map; - CMSBitMap* _mut; - OopTaskQueue* _work_queue; - CMSMarkStack* _overflow_stack; - int _skip_bits; - HeapWord* _finger; - HeapWord* _threshold; - CMSConcMarkingTask* _task; - public: - Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, - MemRegion span, - CMSBitMap* bit_map, - OopTaskQueue* work_queue, - CMSMarkStack* overflow_stack); - bool do_bit(size_t offset); - inline void do_yield_check(); - - private: - void scan_oops_in_oop(HeapWord* ptr); - void do_yield_work(); - bool get_work_from_overflow_stack(); -}; - -// The following closures are used to do certain kinds of verification of -// CMS marking. -class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { - CMSCollector* _collector; - MemRegion _span; - CMSBitMap* _verification_bm; - CMSBitMap* _cms_bm; - CMSMarkStack* _mark_stack; - protected: - void do_oop(oop p); - template inline void do_oop_work(T *p) { - oop obj = oopDesc::load_decode_heap_oop(p); - do_oop(obj); - } - public: - PushAndMarkVerifyClosure(CMSCollector* cms_collector, - MemRegion span, - CMSBitMap* verification_bm, - CMSBitMap* cms_bm, - CMSMarkStack* mark_stack); - void do_oop(oop* p); - void do_oop(narrowOop* p); - - // Deal with a stack overflow condition - void handle_stack_overflow(HeapWord* lost); -}; - -class MarkFromRootsVerifyClosure: public BitMapClosure { - CMSCollector* _collector; - MemRegion _span; - CMSBitMap* _verification_bm; - CMSBitMap* _cms_bm; - CMSMarkStack* _mark_stack; - HeapWord* _finger; - PushAndMarkVerifyClosure _pam_verify_closure; - public: - MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, - CMSBitMap* verification_bm, - CMSBitMap* cms_bm, - CMSMarkStack* mark_stack); - bool do_bit(size_t offset); - void reset(HeapWord* addr); -}; - - -// This closure is used to check that a certain set of bits is -// "empty" (i.e. the bit vector doesn't have any 1-bits). -class FalseBitMapClosure: public BitMapClosure { - public: - bool do_bit(size_t offset) { - guarantee(false, "Should not have a 1 bit"); - return true; - } -}; - -// A version of ObjectClosure with "memory" (see _previous_address below) -class UpwardsObjectClosure: public BoolObjectClosure { - HeapWord* _previous_address; - public: - UpwardsObjectClosure() : _previous_address(NULL) { } - void set_previous(HeapWord* addr) { _previous_address = addr; } - HeapWord* previous() { return _previous_address; } - // A return value of "true" can be used by the caller to decide - // if this object's end should *NOT* be recorded in - // _previous_address above. - virtual bool do_object_bm(oop obj, MemRegion mr) = 0; -}; - -// This closure is used during the second checkpointing phase -// to rescan the marked objects on the dirty cards in the mod -// union table and the card table proper. It's invoked via -// MarkFromDirtyCardsClosure below. It uses either -// [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) -// declared in genOopClosures.hpp to accomplish some of its work. -// In the parallel case the bitMap is shared, so access to -// it needs to be suitably synchronized for updates by embedded -// closures that update it; however, this closure itself only -// reads the bit_map and because it is idempotent, is immune to -// reading stale values. -class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { - #ifdef ASSERT - CMSCollector* _collector; - MemRegion _span; - union { - CMSMarkStack* _mark_stack; - OopTaskQueue* _work_queue; - }; - #endif // ASSERT - bool _parallel; - CMSBitMap* _bit_map; - union { - MarkRefsIntoAndScanClosure* _scan_closure; - Par_MarkRefsIntoAndScanClosure* _par_scan_closure; - }; - - public: - ScanMarkedObjectsAgainClosure(CMSCollector* collector, - MemRegion span, - ReferenceProcessor* rp, - CMSBitMap* bit_map, - CMSMarkStack* mark_stack, - MarkRefsIntoAndScanClosure* cl): - #ifdef ASSERT - _collector(collector), - _span(span), - _mark_stack(mark_stack), - #endif // ASSERT - _parallel(false), - _bit_map(bit_map), - _scan_closure(cl) { } - - ScanMarkedObjectsAgainClosure(CMSCollector* collector, - MemRegion span, - ReferenceProcessor* rp, - CMSBitMap* bit_map, - OopTaskQueue* work_queue, - Par_MarkRefsIntoAndScanClosure* cl): - #ifdef ASSERT - _collector(collector), - _span(span), - _work_queue(work_queue), - #endif // ASSERT - _parallel(true), - _bit_map(bit_map), - _par_scan_closure(cl) { } - - bool do_object_b(oop obj) { - guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); - return false; - } - bool do_object_bm(oop p, MemRegion mr); -}; - -// This closure is used during the second checkpointing phase -// to rescan the marked objects on the dirty cards in the mod -// union table and the card table proper. It invokes -// ScanMarkedObjectsAgainClosure above to accomplish much of its work. -// In the parallel case, the bit map is shared and requires -// synchronized access. -class MarkFromDirtyCardsClosure: public MemRegionClosure { - CompactibleFreeListSpace* _space; - ScanMarkedObjectsAgainClosure _scan_cl; - size_t _num_dirty_cards; - - public: - MarkFromDirtyCardsClosure(CMSCollector* collector, - MemRegion span, - CompactibleFreeListSpace* space, - CMSBitMap* bit_map, - CMSMarkStack* mark_stack, - MarkRefsIntoAndScanClosure* cl): - _space(space), - _num_dirty_cards(0), - _scan_cl(collector, span, collector->ref_processor(), bit_map, - mark_stack, cl) { } - - MarkFromDirtyCardsClosure(CMSCollector* collector, - MemRegion span, - CompactibleFreeListSpace* space, - CMSBitMap* bit_map, - OopTaskQueue* work_queue, - Par_MarkRefsIntoAndScanClosure* cl): - _space(space), - _num_dirty_cards(0), - _scan_cl(collector, span, collector->ref_processor(), bit_map, - work_queue, cl) { } - - void do_MemRegion(MemRegion mr); - void set_space(CompactibleFreeListSpace* space) { _space = space; } - size_t num_dirty_cards() { return _num_dirty_cards; } -}; - -// This closure is used in the non-product build to check -// that there are no MemRegions with a certain property. -class FalseMemRegionClosure: public MemRegionClosure { - void do_MemRegion(MemRegion mr) { - guarantee(!mr.is_empty(), "Shouldn't be empty"); - guarantee(false, "Should never be here"); - } -}; - -// This closure is used during the precleaning phase -// to "carefully" rescan marked objects on dirty cards. -// It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp -// to accomplish some of its work. -class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { - CMSCollector* _collector; - MemRegion _span; - bool _yield; - Mutex* _freelistLock; - CMSBitMap* _bitMap; - CMSMarkStack* _markStack; - MarkRefsIntoAndScanClosure* _scanningClosure; - - public: - ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, - MemRegion span, - CMSBitMap* bitMap, - CMSMarkStack* markStack, - MarkRefsIntoAndScanClosure* cl, - bool should_yield): - _collector(collector), - _span(span), - _yield(should_yield), - _bitMap(bitMap), - _markStack(markStack), - _scanningClosure(cl) { - } - - void do_object(oop p) { - guarantee(false, "call do_object_careful instead"); - } - - size_t do_object_careful(oop p) { - guarantee(false, "Unexpected caller"); - return 0; - } - - size_t do_object_careful_m(oop p, MemRegion mr); - - void setFreelistLock(Mutex* m) { - _freelistLock = m; - _scanningClosure->set_freelistLock(m); - } - - private: - inline bool do_yield_check(); - - void do_yield_work(); -}; - -class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { - CMSCollector* _collector; - MemRegion _span; - bool _yield; - CMSBitMap* _bit_map; - CMSMarkStack* _mark_stack; - PushAndMarkClosure* _scanning_closure; - unsigned int _before_count; - - public: - SurvivorSpacePrecleanClosure(CMSCollector* collector, - MemRegion span, - CMSBitMap* bit_map, - CMSMarkStack* mark_stack, - PushAndMarkClosure* cl, - unsigned int before_count, - bool should_yield): - _collector(collector), - _span(span), - _yield(should_yield), - _bit_map(bit_map), - _mark_stack(mark_stack), - _scanning_closure(cl), - _before_count(before_count) - { } - - void do_object(oop p) { - guarantee(false, "call do_object_careful instead"); - } - - size_t do_object_careful(oop p); - - size_t do_object_careful_m(oop p, MemRegion mr) { - guarantee(false, "Unexpected caller"); - return 0; - } - - private: - inline void do_yield_check(); - void do_yield_work(); -}; - -// This closure is used to accomplish the sweeping work -// after the second checkpoint but before the concurrent reset -// phase. -// -// Terminology -// left hand chunk (LHC) - block of one or more chunks currently being -// coalesced. The LHC is available for coalescing with a new chunk. -// right hand chunk (RHC) - block that is currently being swept that is -// free or garbage that can be coalesced with the LHC. -// _inFreeRange is true if there is currently a LHC -// _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. -// _freeRangeInFreeLists is true if the LHC is in the free lists. -// _freeFinger is the address of the current LHC -class SweepClosure: public BlkClosureCareful { - CMSCollector* _collector; // collector doing the work - ConcurrentMarkSweepGeneration* _g; // Generation being swept - CompactibleFreeListSpace* _sp; // Space being swept - HeapWord* _limit;// the address at or above which the sweep should stop - // because we do not expect newly garbage blocks - // eligible for sweeping past that address. - Mutex* _freelistLock; // Free list lock (in space) - CMSBitMap* _bitMap; // Marking bit map (in - // generation) - bool _inFreeRange; // Indicates if we are in the - // midst of a free run - bool _freeRangeInFreeLists; - // Often, we have just found - // a free chunk and started - // a new free range; we do not - // eagerly remove this chunk from - // the free lists unless there is - // a possibility of coalescing. - // When true, this flag indicates - // that the _freeFinger below - // points to a potentially free chunk - // that may still be in the free lists - bool _lastFreeRangeCoalesced; - // free range contains chunks - // coalesced - bool _yield; - // Whether sweeping should be - // done with yields. For instance - // when done by the foreground - // collector we shouldn't yield. - HeapWord* _freeFinger; // When _inFreeRange is set, the - // pointer to the "left hand - // chunk" - size_t _freeRangeSize; - // When _inFreeRange is set, this - // indicates the accumulated size - // of the "left hand chunk" - NOT_PRODUCT( - size_t _numObjectsFreed; - size_t _numWordsFreed; - size_t _numObjectsLive; - size_t _numWordsLive; - size_t _numObjectsAlreadyFree; - size_t _numWordsAlreadyFree; - FreeChunk* _last_fc; - ) - private: - // Code that is common to a free chunk or garbage when - // encountered during sweeping. - void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); - // Process a free chunk during sweeping. - void do_already_free_chunk(FreeChunk *fc); - // Work method called when processing an already free or a - // freshly garbage chunk to do a lookahead and possibly a - // preemptive flush if crossing over _limit. - void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); - // Process a garbage chunk during sweeping. - size_t do_garbage_chunk(FreeChunk *fc); - // Process a live chunk during sweeping. - size_t do_live_chunk(FreeChunk* fc); - - // Accessors. - HeapWord* freeFinger() const { return _freeFinger; } - void set_freeFinger(HeapWord* v) { _freeFinger = v; } - bool inFreeRange() const { return _inFreeRange; } - void set_inFreeRange(bool v) { _inFreeRange = v; } - bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } - void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } - bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } - void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } - - // Initialize a free range. - void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); - // Return this chunk to the free lists. - void flush_cur_free_chunk(HeapWord* chunk, size_t size); - - // Check if we should yield and do so when necessary. - inline void do_yield_check(HeapWord* addr); - - // Yield - void do_yield_work(HeapWord* addr); - - // Debugging/Printing - void print_free_block_coalesced(FreeChunk* fc) const; - - public: - SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, - CMSBitMap* bitMap, bool should_yield); - ~SweepClosure() PRODUCT_RETURN; - - size_t do_blk_careful(HeapWord* addr); - void print() const { print_on(tty); } - void print_on(outputStream *st) const; -}; - -// Closures related to weak references processing - -// During CMS' weak reference processing, this is a -// work-routine/closure used to complete transitive -// marking of objects as live after a certain point -// in which an initial set has been completely accumulated. -// This closure is currently used both during the final -// remark stop-world phase, as well as during the concurrent -// precleaning of the discovered reference lists. -class CMSDrainMarkingStackClosure: public VoidClosure { - CMSCollector* _collector; - MemRegion _span; - CMSMarkStack* _mark_stack; - CMSBitMap* _bit_map; - CMSKeepAliveClosure* _keep_alive; - bool _concurrent_precleaning; - public: - CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, - CMSBitMap* bit_map, CMSMarkStack* mark_stack, - CMSKeepAliveClosure* keep_alive, - bool cpc): - _collector(collector), - _span(span), - _bit_map(bit_map), - _mark_stack(mark_stack), - _keep_alive(keep_alive), - _concurrent_precleaning(cpc) { - assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), - "Mismatch"); - } - - void do_void(); -}; - -// A parallel version of CMSDrainMarkingStackClosure above. -class CMSParDrainMarkingStackClosure: public VoidClosure { - CMSCollector* _collector; - MemRegion _span; - OopTaskQueue* _work_queue; - CMSBitMap* _bit_map; - CMSInnerParMarkAndPushClosure _mark_and_push; - - public: - CMSParDrainMarkingStackClosure(CMSCollector* collector, - MemRegion span, CMSBitMap* bit_map, - OopTaskQueue* work_queue): - _collector(collector), - _span(span), - _bit_map(bit_map), - _work_queue(work_queue), - _mark_and_push(collector, span, bit_map, work_queue) { } - - public: - void trim_queue(uint max); - void do_void(); -}; - -// Allow yielding or short-circuiting of reference list -// precleaning work. -class CMSPrecleanRefsYieldClosure: public YieldClosure { - CMSCollector* _collector; - void do_yield_work(); - public: - CMSPrecleanRefsYieldClosure(CMSCollector* collector): - _collector(collector) {} - virtual bool should_return(); -}; - - -// Convenience class that locks free list locks for given CMS collector -class FreelistLocker: public StackObj { - private: - CMSCollector* _collector; - public: - FreelistLocker(CMSCollector* collector): - _collector(collector) { - _collector->getFreelistLocks(); - } - - ~FreelistLocker() { - _collector->releaseFreelistLocks(); - } -}; - -// Mark all dead objects in a given space. -class MarkDeadObjectsClosure: public BlkClosure { - const CMSCollector* _collector; - const CompactibleFreeListSpace* _sp; - CMSBitMap* _live_bit_map; - CMSBitMap* _dead_bit_map; -public: - MarkDeadObjectsClosure(const CMSCollector* collector, - const CompactibleFreeListSpace* sp, - CMSBitMap *live_bit_map, - CMSBitMap *dead_bit_map) : - _collector(collector), - _sp(sp), - _live_bit_map(live_bit_map), - _dead_bit_map(dead_bit_map) {} - size_t do_blk(HeapWord* addr); -}; - -class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { - - public: - TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); -}; - - -#endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP --- /dev/null 2015-03-18 17:10:38.111854831 +0100 +++ new/src/share/vm/gc/cms/concurrentMarkSweepGeneration.hpp 2015-05-13 13:54:24.820058347 +0200 @@ -0,0 +1,1816 @@ +/* + * Copyright (c) 2001, 2015, 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_CMS_CONCURRENTMARKSWEEPGENERATION_HPP +#define SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP + +#include "gc/cms/cmsOopClosures.hpp" +#include "gc/cms/gSpaceCounters.hpp" +#include "gc/cms/yieldingWorkgroup.hpp" +#include "gc/shared/cardGeneration.hpp" +#include "gc/shared/gcHeapSummary.hpp" +#include "gc/shared/gcStats.hpp" +#include "gc/shared/gcWhen.hpp" +#include "gc/shared/generationCounters.hpp" +#include "gc/shared/space.hpp" +#include "gc/shared/taskqueue.hpp" +#include "memory/freeBlockDictionary.hpp" +#include "memory/iterator.hpp" +#include "memory/virtualspace.hpp" +#include "runtime/mutexLocker.hpp" +#include "services/memoryService.hpp" +#include "utilities/bitMap.hpp" +#include "utilities/stack.hpp" + +// ConcurrentMarkSweepGeneration is in support of a concurrent +// mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker +// style. We assume, for now, that this generation is always the +// seniormost generation and for simplicity +// in the first implementation, that this generation is a single compactible +// space. Neither of these restrictions appears essential, and will be +// relaxed in the future when more time is available to implement the +// greater generality (and there's a need for it). +// +// Concurrent mode failures are currently handled by +// means of a sliding mark-compact. + +class AdaptiveSizePolicy; +class CMSCollector; +class CMSConcMarkingTask; +class CMSGCAdaptivePolicyCounters; +class CMSTracer; +class ConcurrentGCTimer; +class ConcurrentMarkSweepGeneration; +class ConcurrentMarkSweepPolicy; +class ConcurrentMarkSweepThread; +class CompactibleFreeListSpace; +class FreeChunk; +class ParNewGeneration; +class PromotionInfo; +class ScanMarkedObjectsAgainCarefullyClosure; +class TenuredGeneration; +class SerialOldTracer; + +// A generic CMS bit map. It's the basis for both the CMS marking bit map +// as well as for the mod union table (in each case only a subset of the +// methods are used). This is essentially a wrapper around the BitMap class, +// with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, +// we have _shifter == 0. and for the mod union table we have +// shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) +// XXX 64-bit issues in BitMap? +class CMSBitMap VALUE_OBJ_CLASS_SPEC { + friend class VMStructs; + + HeapWord* _bmStartWord; // base address of range covered by map + size_t _bmWordSize; // map size (in #HeapWords covered) + const int _shifter; // shifts to convert HeapWord to bit position + VirtualSpace _virtual_space; // underlying the bit map + BitMap _bm; // the bit map itself + public: + Mutex* const _lock; // mutex protecting _bm; + + public: + // constructor + CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); + + // allocates the actual storage for the map + bool allocate(MemRegion mr); + // field getter + Mutex* lock() const { return _lock; } + // locking verifier convenience function + void assert_locked() const PRODUCT_RETURN; + + // inquiries + HeapWord* startWord() const { return _bmStartWord; } + size_t sizeInWords() const { return _bmWordSize; } + size_t sizeInBits() const { return _bm.size(); } + // the following is one past the last word in space + HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } + + // reading marks + bool isMarked(HeapWord* addr) const; + bool par_isMarked(HeapWord* addr) const; // do not lock checks + bool isUnmarked(HeapWord* addr) const; + bool isAllClear() const; + + // writing marks + void mark(HeapWord* addr); + // For marking by parallel GC threads; + // returns true if we did, false if another thread did + bool par_mark(HeapWord* addr); + + void mark_range(MemRegion mr); + void par_mark_range(MemRegion mr); + void mark_large_range(MemRegion mr); + void par_mark_large_range(MemRegion mr); + void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. + void clear_range(MemRegion mr); + void par_clear_range(MemRegion mr); + void clear_large_range(MemRegion mr); + void par_clear_large_range(MemRegion mr); + void clear_all(); + void clear_all_incrementally(); // Not yet implemented!! + + NOT_PRODUCT( + // checks the memory region for validity + void region_invariant(MemRegion mr); + ) + + // iteration + void iterate(BitMapClosure* cl) { + _bm.iterate(cl); + } + void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); + void dirty_range_iterate_clear(MemRegionClosure* cl); + void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); + + // auxiliary support for iteration + HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; + HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, + HeapWord* end_addr) const; + HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; + HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, + HeapWord* end_addr) const; + MemRegion getAndClearMarkedRegion(HeapWord* addr); + MemRegion getAndClearMarkedRegion(HeapWord* start_addr, + HeapWord* end_addr); + + // conversion utilities + HeapWord* offsetToHeapWord(size_t offset) const; + size_t heapWordToOffset(HeapWord* addr) const; + size_t heapWordDiffToOffsetDiff(size_t diff) const; + + void print_on_error(outputStream* st, const char* prefix) const; + + // debugging + // is this address range covered by the bit-map? + NOT_PRODUCT( + bool covers(MemRegion mr) const; + bool covers(HeapWord* start, size_t size = 0) const; + ) + void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; +}; + +// Represents a marking stack used by the CMS collector. +// Ideally this should be GrowableArray<> just like MSC's marking stack(s). +class CMSMarkStack: public CHeapObj { + friend class CMSCollector; // To get at expansion stats further below. + + VirtualSpace _virtual_space; // Space for the stack + oop* _base; // Bottom of stack + size_t _index; // One more than last occupied index + size_t _capacity; // Max #elements + Mutex _par_lock; // An advisory lock used in case of parallel access + NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run + + protected: + size_t _hit_limit; // We hit max stack size limit + size_t _failed_double; // We failed expansion before hitting limit + + public: + CMSMarkStack(): + _par_lock(Mutex::event, "CMSMarkStack._par_lock", true, + Monitor::_safepoint_check_never), + _hit_limit(0), + _failed_double(0) {} + + bool allocate(size_t size); + + size_t capacity() const { return _capacity; } + + oop pop() { + if (!isEmpty()) { + return _base[--_index] ; + } + return NULL; + } + + bool push(oop ptr) { + if (isFull()) { + return false; + } else { + _base[_index++] = ptr; + NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); + return true; + } + } + + bool isEmpty() const { return _index == 0; } + bool isFull() const { + assert(_index <= _capacity, "buffer overflow"); + return _index == _capacity; + } + + size_t length() { return _index; } + + // "Parallel versions" of some of the above + oop par_pop() { + // lock and pop + MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); + return pop(); + } + + bool par_push(oop ptr) { + // lock and push + MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); + return push(ptr); + } + + // Forcibly reset the stack, losing all of its contents. + void reset() { + _index = 0; + } + + // Expand the stack, typically in response to an overflow condition. + void expand(); + + // Compute the least valued stack element. + oop least_value(HeapWord* low) { + oop least = (oop)low; + for (size_t i = 0; i < _index; i++) { + least = MIN2(least, _base[i]); + } + return least; + } + + // Exposed here to allow stack expansion in || case. + Mutex* par_lock() { return &_par_lock; } +}; + +class CardTableRS; +class CMSParGCThreadState; + +class ModUnionClosure: public MemRegionClosure { + protected: + CMSBitMap* _t; + public: + ModUnionClosure(CMSBitMap* t): _t(t) { } + void do_MemRegion(MemRegion mr); +}; + +class ModUnionClosurePar: public ModUnionClosure { + public: + ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } + void do_MemRegion(MemRegion mr); +}; + +// Survivor Chunk Array in support of parallelization of +// Survivor Space rescan. +class ChunkArray: public CHeapObj { + size_t _index; + size_t _capacity; + size_t _overflows; + HeapWord** _array; // storage for array + + public: + ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} + ChunkArray(HeapWord** a, size_t c): + _index(0), _capacity(c), _overflows(0), _array(a) {} + + HeapWord** array() { return _array; } + void set_array(HeapWord** a) { _array = a; } + + size_t capacity() { return _capacity; } + void set_capacity(size_t c) { _capacity = c; } + + size_t end() { + assert(_index <= capacity(), + err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", + _index, _capacity)); + return _index; + } // exclusive + + HeapWord* nth(size_t n) { + assert(n < end(), "Out of bounds access"); + return _array[n]; + } + + void reset() { + _index = 0; + if (_overflows > 0 && PrintCMSStatistics > 1) { + warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", + _capacity, _overflows); + } + _overflows = 0; + } + + void record_sample(HeapWord* p, size_t sz) { + // For now we do not do anything with the size + if (_index < _capacity) { + _array[_index++] = p; + } else { + ++_overflows; + assert(_index == _capacity, + err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT + "): out of bounds at overflow#" SIZE_FORMAT, + _index, _capacity, _overflows)); + } + } +}; + +// +// Timing, allocation and promotion statistics for gc scheduling and incremental +// mode pacing. Most statistics are exponential averages. +// +class CMSStats VALUE_OBJ_CLASS_SPEC { + private: + ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. + + // The following are exponential averages with factor alpha: + // avg = (100 - alpha) * avg + alpha * cur_sample + // + // The durations measure: end_time[n] - start_time[n] + // The periods measure: start_time[n] - start_time[n-1] + // + // The cms period and duration include only concurrent collections; time spent + // in foreground cms collections due to System.gc() or because of a failure to + // keep up are not included. + // + // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the + // real value, but is used only after the first period. A value of 100 is + // used for the first sample so it gets the entire weight. + unsigned int _saved_alpha; // 0-100 + unsigned int _gc0_alpha; + unsigned int _cms_alpha; + + double _gc0_duration; + double _gc0_period; + size_t _gc0_promoted; // bytes promoted per gc0 + double _cms_duration; + double _cms_duration_pre_sweep; // time from initiation to start of sweep + double _cms_period; + size_t _cms_allocated; // bytes of direct allocation per gc0 period + + // Timers. + elapsedTimer _cms_timer; + TimeStamp _gc0_begin_time; + TimeStamp _cms_begin_time; + TimeStamp _cms_end_time; + + // Snapshots of the amount used in the CMS generation. + size_t _cms_used_at_gc0_begin; + size_t _cms_used_at_gc0_end; + size_t _cms_used_at_cms_begin; + + // Used to prevent the duty cycle from being reduced in the middle of a cms + // cycle. + bool _allow_duty_cycle_reduction; + + enum { + _GC0_VALID = 0x1, + _CMS_VALID = 0x2, + _ALL_VALID = _GC0_VALID | _CMS_VALID + }; + + unsigned int _valid_bits; + + protected: + // In support of adjusting of cms trigger ratios based on history + // of concurrent mode failure. + double cms_free_adjustment_factor(size_t free) const; + void adjust_cms_free_adjustment_factor(bool fail, size_t free); + + public: + CMSStats(ConcurrentMarkSweepGeneration* cms_gen, + unsigned int alpha = CMSExpAvgFactor); + + // Whether or not the statistics contain valid data; higher level statistics + // cannot be called until this returns true (they require at least one young + // gen and one cms cycle to have completed). + bool valid() const; + + // Record statistics. + void record_gc0_begin(); + void record_gc0_end(size_t cms_gen_bytes_used); + void record_cms_begin(); + void record_cms_end(); + + // Allow management of the cms timer, which must be stopped/started around + // yield points. + elapsedTimer& cms_timer() { return _cms_timer; } + void start_cms_timer() { _cms_timer.start(); } + void stop_cms_timer() { _cms_timer.stop(); } + + // Basic statistics; units are seconds or bytes. + double gc0_period() const { return _gc0_period; } + double gc0_duration() const { return _gc0_duration; } + size_t gc0_promoted() const { return _gc0_promoted; } + double cms_period() const { return _cms_period; } + double cms_duration() const { return _cms_duration; } + size_t cms_allocated() const { return _cms_allocated; } + + size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} + + // Seconds since the last background cms cycle began or ended. + double cms_time_since_begin() const; + double cms_time_since_end() const; + + // Higher level statistics--caller must check that valid() returns true before + // calling. + + // Returns bytes promoted per second of wall clock time. + double promotion_rate() const; + + // Returns bytes directly allocated per second of wall clock time. + double cms_allocation_rate() const; + + // Rate at which space in the cms generation is being consumed (sum of the + // above two). + double cms_consumption_rate() const; + + // Returns an estimate of the number of seconds until the cms generation will + // fill up, assuming no collection work is done. + double time_until_cms_gen_full() const; + + // Returns an estimate of the number of seconds remaining until + // the cms generation collection should start. + double time_until_cms_start() const; + + // End of higher level statistics. + + // Debugging. + void print_on(outputStream* st) const PRODUCT_RETURN; + void print() const { print_on(gclog_or_tty); } +}; + +// A closure related to weak references processing which +// we embed in the CMSCollector, since we need to pass +// it to the reference processor for secondary filtering +// of references based on reachability of referent; +// see role of _is_alive_non_header closure in the +// ReferenceProcessor class. +// For objects in the CMS generation, this closure checks +// if the object is "live" (reachable). Used in weak +// reference processing. +class CMSIsAliveClosure: public BoolObjectClosure { + const MemRegion _span; + const CMSBitMap* _bit_map; + + friend class CMSCollector; + public: + CMSIsAliveClosure(MemRegion span, + CMSBitMap* bit_map): + _span(span), + _bit_map(bit_map) { + assert(!span.is_empty(), "Empty span could spell trouble"); + } + + bool do_object_b(oop obj); +}; + + +// Implements AbstractRefProcTaskExecutor for CMS. +class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { +public: + + CMSRefProcTaskExecutor(CMSCollector& collector) + : _collector(collector) + { } + + // Executes a task using worker threads. + virtual void execute(ProcessTask& task); + virtual void execute(EnqueueTask& task); +private: + CMSCollector& _collector; +}; + + +class CMSCollector: public CHeapObj { + friend class VMStructs; + friend class ConcurrentMarkSweepThread; + friend class ConcurrentMarkSweepGeneration; + friend class CompactibleFreeListSpace; + friend class CMSParMarkTask; + friend class CMSParInitialMarkTask; + friend class CMSParRemarkTask; + friend class CMSConcMarkingTask; + friend class CMSRefProcTaskProxy; + friend class CMSRefProcTaskExecutor; + friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden + friend class SurvivorSpacePrecleanClosure; // --- ditto ------- + friend class PushOrMarkClosure; // to access _restart_addr + friend class Par_PushOrMarkClosure; // to access _restart_addr + friend class MarkFromRootsClosure; // -- ditto -- + // ... and for clearing cards + friend class Par_MarkFromRootsClosure; // to access _restart_addr + // ... and for clearing cards + friend class Par_ConcMarkingClosure; // to access _restart_addr etc. + friend class MarkFromRootsVerifyClosure; // to access _restart_addr + friend class PushAndMarkVerifyClosure; // -- ditto -- + friend class MarkRefsIntoAndScanClosure; // to access _overflow_list + friend class PushAndMarkClosure; // -- ditto -- + friend class Par_PushAndMarkClosure; // -- ditto -- + friend class CMSKeepAliveClosure; // -- ditto -- + friend class CMSDrainMarkingStackClosure; // -- ditto -- + friend class CMSInnerParMarkAndPushClosure; // -- ditto -- + NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list + friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait + friend class VM_CMS_Operation; + friend class VM_CMS_Initial_Mark; + friend class VM_CMS_Final_Remark; + friend class TraceCMSMemoryManagerStats; + + private: + jlong _time_of_last_gc; + void update_time_of_last_gc(jlong now) { + _time_of_last_gc = now; + } + + OopTaskQueueSet* _task_queues; + + // Overflow list of grey objects, threaded through mark-word + // Manipulated with CAS in the parallel/multi-threaded case. + oop _overflow_list; + // The following array-pair keeps track of mark words + // displaced for accommodating overflow list above. + // This code will likely be revisited under RFE#4922830. + Stack _preserved_oop_stack; + Stack _preserved_mark_stack; + + int* _hash_seed; + + // In support of multi-threaded concurrent phases + YieldingFlexibleWorkGang* _conc_workers; + + // Performance Counters + CollectorCounters* _gc_counters; + + // Initialization Errors + bool _completed_initialization; + + // In support of ExplicitGCInvokesConcurrent + static bool _full_gc_requested; + static GCCause::Cause _full_gc_cause; + unsigned int _collection_count_start; + + // Should we unload classes this concurrent cycle? + bool _should_unload_classes; + unsigned int _concurrent_cycles_since_last_unload; + unsigned int concurrent_cycles_since_last_unload() const { + return _concurrent_cycles_since_last_unload; + } + // Did we (allow) unload classes in the previous concurrent cycle? + bool unloaded_classes_last_cycle() const { + return concurrent_cycles_since_last_unload() == 0; + } + // Root scanning options for perm gen + int _roots_scanning_options; + int roots_scanning_options() const { return _roots_scanning_options; } + void add_root_scanning_option(int o) { _roots_scanning_options |= o; } + void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } + + // Verification support + CMSBitMap _verification_mark_bm; + void verify_after_remark_work_1(); + void verify_after_remark_work_2(); + + // True if any verification flag is on. + bool _verifying; + bool verifying() const { return _verifying; } + void set_verifying(bool v) { _verifying = v; } + + // Collector policy + ConcurrentMarkSweepPolicy* _collector_policy; + ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } + + void set_did_compact(bool v); + + // XXX Move these to CMSStats ??? FIX ME !!! + elapsedTimer _inter_sweep_timer; // Time between sweeps + elapsedTimer _intra_sweep_timer; // Time _in_ sweeps + // Padded decaying average estimates of the above + AdaptivePaddedAverage _inter_sweep_estimate; + AdaptivePaddedAverage _intra_sweep_estimate; + + CMSTracer* _gc_tracer_cm; + ConcurrentGCTimer* _gc_timer_cm; + + bool _cms_start_registered; + + GCHeapSummary _last_heap_summary; + MetaspaceSummary _last_metaspace_summary; + + void register_gc_start(GCCause::Cause cause); + void register_gc_end(); + void save_heap_summary(); + void report_heap_summary(GCWhen::Type when); + + protected: + ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) + MemRegion _span; // Span covering above two + CardTableRS* _ct; // Card table + + // CMS marking support structures + CMSBitMap _markBitMap; + CMSBitMap _modUnionTable; + CMSMarkStack _markStack; + + HeapWord* _restart_addr; // In support of marking stack overflow + void lower_restart_addr(HeapWord* low); + + // Counters in support of marking stack / work queue overflow handling: + // a non-zero value indicates certain types of overflow events during + // the current CMS cycle and could lead to stack resizing efforts at + // an opportune future time. + size_t _ser_pmc_preclean_ovflw; + size_t _ser_pmc_remark_ovflw; + size_t _par_pmc_remark_ovflw; + size_t _ser_kac_preclean_ovflw; + size_t _ser_kac_ovflw; + size_t _par_kac_ovflw; + NOT_PRODUCT(ssize_t _num_par_pushes;) + + // ("Weak") Reference processing support. + ReferenceProcessor* _ref_processor; + CMSIsAliveClosure _is_alive_closure; + // Keep this textually after _markBitMap and _span; c'tor dependency. + + ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work + ModUnionClosurePar _modUnionClosurePar; + + // CMS abstract state machine + // initial_state: Idling + // next_state(Idling) = {Marking} + // next_state(Marking) = {Precleaning, Sweeping} + // next_state(Precleaning) = {AbortablePreclean, FinalMarking} + // next_state(AbortablePreclean) = {FinalMarking} + // next_state(FinalMarking) = {Sweeping} + // next_state(Sweeping) = {Resizing} + // next_state(Resizing) = {Resetting} + // next_state(Resetting) = {Idling} + // The numeric values below are chosen so that: + // . _collectorState <= Idling == post-sweep && pre-mark + // . _collectorState in (Idling, Sweeping) == {initial,final}marking || + // precleaning || abortablePrecleanb + public: + enum CollectorState { + Resizing = 0, + Resetting = 1, + Idling = 2, + InitialMarking = 3, + Marking = 4, + Precleaning = 5, + AbortablePreclean = 6, + FinalMarking = 7, + Sweeping = 8 + }; + protected: + static CollectorState _collectorState; + + // State related to prologue/epilogue invocation for my generations + bool _between_prologue_and_epilogue; + + // Signaling/State related to coordination between fore- and background GC + // Note: When the baton has been passed from background GC to foreground GC, + // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. + static bool _foregroundGCIsActive; // true iff foreground collector is active or + // wants to go active + static bool _foregroundGCShouldWait; // true iff background GC is active and has not + // yet passed the baton to the foreground GC + + // Support for CMSScheduleRemark (abortable preclean) + bool _abort_preclean; + bool _start_sampling; + + int _numYields; + size_t _numDirtyCards; + size_t _sweep_count; + + // Occupancy used for bootstrapping stats + double _bootstrap_occupancy; + + // Timer + elapsedTimer _timer; + + // Timing, allocation and promotion statistics, used for scheduling. + CMSStats _stats; + + enum CMS_op_type { + CMS_op_checkpointRootsInitial, + CMS_op_checkpointRootsFinal + }; + + void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); + bool stop_world_and_do(CMS_op_type op); + + OopTaskQueueSet* task_queues() { return _task_queues; } + int* hash_seed(int i) { return &_hash_seed[i]; } + YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } + + // Support for parallelizing Eden rescan in CMS remark phase + void sample_eden(); // ... sample Eden space top + + private: + // Support for parallelizing young gen rescan in CMS remark phase + ParNewGeneration* _young_gen; // the younger gen + + HeapWord** _top_addr; // ... Top of Eden + HeapWord** _end_addr; // ... End of Eden + Mutex* _eden_chunk_lock; + HeapWord** _eden_chunk_array; // ... Eden partitioning array + size_t _eden_chunk_index; // ... top (exclusive) of array + size_t _eden_chunk_capacity; // ... max entries in array + + // Support for parallelizing survivor space rescan + HeapWord** _survivor_chunk_array; + size_t _survivor_chunk_index; + size_t _survivor_chunk_capacity; + size_t* _cursor; + ChunkArray* _survivor_plab_array; + + // A bounded minimum size of PLABs, should not return too small values since + // this will affect the size of the data structures used for parallel young gen rescan + size_t plab_sample_minimum_size(); + + // Support for marking stack overflow handling + bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); + bool par_take_from_overflow_list(size_t num, + OopTaskQueue* to_work_q, + int no_of_gc_threads); + void push_on_overflow_list(oop p); + void par_push_on_overflow_list(oop p); + // The following is, obviously, not, in general, "MT-stable" + bool overflow_list_is_empty() const; + + void preserve_mark_if_necessary(oop p); + void par_preserve_mark_if_necessary(oop p); + void preserve_mark_work(oop p, markOop m); + void restore_preserved_marks_if_any(); + NOT_PRODUCT(bool no_preserved_marks() const;) + // In support of testing overflow code + NOT_PRODUCT(int _overflow_counter;) + NOT_PRODUCT(bool simulate_overflow();) // Sequential + NOT_PRODUCT(bool par_simulate_overflow();) // MT version + + // CMS work methods + void checkpointRootsInitialWork(); // Initial checkpoint work + + // A return value of false indicates failure due to stack overflow + bool markFromRootsWork(); // Concurrent marking work + + public: // FIX ME!!! only for testing + bool do_marking_st(); // Single-threaded marking + bool do_marking_mt(); // Multi-threaded marking + + private: + + // Concurrent precleaning work + size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, + ScanMarkedObjectsAgainCarefullyClosure* cl); + size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, + ScanMarkedObjectsAgainCarefullyClosure* cl); + // Does precleaning work, returning a quantity indicative of + // the amount of "useful work" done. + size_t preclean_work(bool clean_refs, bool clean_survivors); + void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); + void abortable_preclean(); // Preclean while looking for possible abort + void initialize_sequential_subtasks_for_young_gen_rescan(int i); + // Helper function for above; merge-sorts the per-thread plab samples + void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); + // Resets (i.e. clears) the per-thread plab sample vectors + void reset_survivor_plab_arrays(); + + // Final (second) checkpoint work + void checkpointRootsFinalWork(); + // Work routine for parallel version of remark + void do_remark_parallel(); + // Work routine for non-parallel version of remark + void do_remark_non_parallel(); + // Reference processing work routine (during second checkpoint) + void refProcessingWork(); + + // Concurrent sweeping work + void sweepWork(ConcurrentMarkSweepGeneration* gen); + + // (Concurrent) resetting of support data structures + void reset(bool concurrent); + + // Clear _expansion_cause fields of constituent generations + void clear_expansion_cause(); + + // An auxiliary method used to record the ends of + // used regions of each generation to limit the extent of sweep + void save_sweep_limits(); + + // A work method used by the foreground collector to do + // a mark-sweep-compact. + void do_compaction_work(bool clear_all_soft_refs); + + // Work methods for reporting concurrent mode interruption or failure + bool is_external_interruption(); + void report_concurrent_mode_interruption(); + + // If the background GC is active, acquire control from the background + // GC and do the collection. + void acquire_control_and_collect(bool full, bool clear_all_soft_refs); + + // For synchronizing passing of control from background to foreground + // GC. waitForForegroundGC() is called by the background + // collector. It if had to wait for a foreground collection, + // it returns true and the background collection should assume + // that the collection was finished by the foreground + // collector. + bool waitForForegroundGC(); + + size_t block_size_using_printezis_bits(HeapWord* addr) const; + size_t block_size_if_printezis_bits(HeapWord* addr) const; + HeapWord* next_card_start_after_block(HeapWord* addr) const; + + void setup_cms_unloading_and_verification_state(); + public: + CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, + CardTableRS* ct, + ConcurrentMarkSweepPolicy* cp); + ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } + + ReferenceProcessor* ref_processor() { return _ref_processor; } + void ref_processor_init(); + + Mutex* bitMapLock() const { return _markBitMap.lock(); } + static CollectorState abstract_state() { return _collectorState; } + + bool should_abort_preclean() const; // Whether preclean should be aborted. + size_t get_eden_used() const; + size_t get_eden_capacity() const; + + ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } + + // Locking checks + NOT_PRODUCT(static bool have_cms_token();) + + bool shouldConcurrentCollect(); + + void collect(bool full, + bool clear_all_soft_refs, + size_t size, + bool tlab); + void collect_in_background(GCCause::Cause cause); + + // In support of ExplicitGCInvokesConcurrent + static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); + // Should we unload classes in a particular concurrent cycle? + bool should_unload_classes() const { + return _should_unload_classes; + } + void update_should_unload_classes(); + + void direct_allocated(HeapWord* start, size_t size); + + // Object is dead if not marked and current phase is sweeping. + bool is_dead_obj(oop obj) const; + + // After a promotion (of "start"), do any necessary marking. + // If "par", then it's being done by a parallel GC thread. + // The last two args indicate if we need precise marking + // and if so the size of the object so it can be dirtied + // in its entirety. + void promoted(bool par, HeapWord* start, + bool is_obj_array, size_t obj_size); + + void getFreelistLocks() const; + void releaseFreelistLocks() const; + bool haveFreelistLocks() const; + + // Adjust size of underlying generation + void compute_new_size(); + + // GC prologue and epilogue + void gc_prologue(bool full); + void gc_epilogue(bool full); + + jlong time_of_last_gc(jlong now) { + if (_collectorState <= Idling) { + // gc not in progress + return _time_of_last_gc; + } else { + // collection in progress + return now; + } + } + + // Support for parallel remark of survivor space + void* get_data_recorder(int thr_num); + void sample_eden_chunk(); + + CMSBitMap* markBitMap() { return &_markBitMap; } + void directAllocated(HeapWord* start, size_t size); + + // Main CMS steps and related support + void checkpointRootsInitial(); + bool markFromRoots(); // a return value of false indicates failure + // due to stack overflow + void preclean(); + void checkpointRootsFinal(); + void sweep(); + + // Check that the currently executing thread is the expected + // one (foreground collector or background collector). + static void check_correct_thread_executing() PRODUCT_RETURN; + + bool is_cms_reachable(HeapWord* addr); + + // Performance Counter Support + CollectorCounters* counters() { return _gc_counters; } + + // Timer stuff + void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } + void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } + void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } + double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } + + int yields() { return _numYields; } + void resetYields() { _numYields = 0; } + void incrementYields() { _numYields++; } + void resetNumDirtyCards() { _numDirtyCards = 0; } + void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } + size_t numDirtyCards() { return _numDirtyCards; } + + static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } + static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } + static bool foregroundGCIsActive() { return _foregroundGCIsActive; } + static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } + size_t sweep_count() const { return _sweep_count; } + void increment_sweep_count() { _sweep_count++; } + + // Timers/stats for gc scheduling and incremental mode pacing. + CMSStats& stats() { return _stats; } + + // Adaptive size policy + AdaptiveSizePolicy* size_policy(); + + static void print_on_error(outputStream* st); + + // Debugging + void verify(); + bool verify_after_remark(bool silent = VerifySilently); + void verify_ok_to_terminate() const PRODUCT_RETURN; + void verify_work_stacks_empty() const PRODUCT_RETURN; + void verify_overflow_empty() const PRODUCT_RETURN; + + // Convenience methods in support of debugging + static const size_t skip_header_HeapWords() PRODUCT_RETURN0; + HeapWord* block_start(const void* p) const PRODUCT_RETURN0; + + // Accessors + CMSMarkStack* verification_mark_stack() { return &_markStack; } + CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } + + // Initialization errors + bool completed_initialization() { return _completed_initialization; } + + void print_eden_and_survivor_chunk_arrays(); +}; + +class CMSExpansionCause : public AllStatic { + public: + enum Cause { + _no_expansion, + _satisfy_free_ratio, + _satisfy_promotion, + _satisfy_allocation, + _allocate_par_lab, + _allocate_par_spooling_space, + _adaptive_size_policy + }; + // Return a string describing the cause of the expansion. + static const char* to_string(CMSExpansionCause::Cause cause); +}; + +class ConcurrentMarkSweepGeneration: public CardGeneration { + friend class VMStructs; + friend class ConcurrentMarkSweepThread; + friend class ConcurrentMarkSweep; + friend class CMSCollector; + protected: + static CMSCollector* _collector; // the collector that collects us + CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) + + // Performance Counters + GenerationCounters* _gen_counters; + GSpaceCounters* _space_counters; + + // Words directly allocated, used by CMSStats. + size_t _direct_allocated_words; + + // Non-product stat counters + NOT_PRODUCT( + size_t _numObjectsPromoted; + size_t _numWordsPromoted; + size_t _numObjectsAllocated; + size_t _numWordsAllocated; + ) + + // Used for sizing decisions + bool _incremental_collection_failed; + bool incremental_collection_failed() { + return _incremental_collection_failed; + } + void set_incremental_collection_failed() { + _incremental_collection_failed = true; + } + void clear_incremental_collection_failed() { + _incremental_collection_failed = false; + } + + // accessors + void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} + CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } + + // Accessing spaces + CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } + + private: + // For parallel young-gen GC support. + CMSParGCThreadState** _par_gc_thread_states; + + // Reason generation was expanded + CMSExpansionCause::Cause _expansion_cause; + + // In support of MinChunkSize being larger than min object size + const double _dilatation_factor; + + // True if a compacting collection was done. + bool _did_compact; + bool did_compact() { return _did_compact; } + + // Fraction of current occupancy at which to start a CMS collection which + // will collect this generation (at least). + double _initiating_occupancy; + + protected: + // Shrink generation by specified size (returns false if unable to shrink) + void shrink_free_list_by(size_t bytes); + + // Update statistics for GC + virtual void update_gc_stats(int level, bool full); + + // Maximum available space in the generation (including uncommitted) + // space. + size_t max_available() const; + + // getter and initializer for _initiating_occupancy field. + double initiating_occupancy() const { return _initiating_occupancy; } + void init_initiating_occupancy(intx io, uintx tr); + + void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); + + void assert_correct_size_change_locking(); + + public: + ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, + int level, CardTableRS* ct, + bool use_adaptive_freelists, + FreeBlockDictionary::DictionaryChoice); + + // Accessors + CMSCollector* collector() const { return _collector; } + static void set_collector(CMSCollector* collector) { + assert(_collector == NULL, "already set"); + _collector = collector; + } + CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } + + Mutex* freelistLock() const; + + virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } + + void set_did_compact(bool v) { _did_compact = v; } + + bool refs_discovery_is_atomic() const { return false; } + bool refs_discovery_is_mt() const { + // Note: CMS does MT-discovery during the parallel-remark + // phases. Use ReferenceProcessorMTMutator to make refs + // discovery MT-safe during such phases or other parallel + // discovery phases in the future. This may all go away + // if/when we decide that refs discovery is sufficiently + // rare that the cost of the CAS's involved is in the + // noise. That's a measurement that should be done, and + // the code simplified if that turns out to be the case. + return ConcGCThreads > 1; + } + + // Override + virtual void ref_processor_init(); + + void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } + + // Space enquiries + double occupancy() const { return ((double)used())/((double)capacity()); } + size_t contiguous_available() const; + size_t unsafe_max_alloc_nogc() const; + + // over-rides + MemRegion used_region_at_save_marks() const; + + // Does a "full" (forced) collection invoked on this generation collect + // all younger generations as well? Note that the second conjunct is a + // hack to allow the collection of the younger gen first if the flag is + // set. + virtual bool full_collects_younger_generations() const { + return !ScavengeBeforeFullGC; + } + + // Adjust quantities in the generation affected by + // the compaction. + void reset_after_compaction(); + + // Allocation support + HeapWord* allocate(size_t size, bool tlab); + HeapWord* have_lock_and_allocate(size_t size, bool tlab); + oop promote(oop obj, size_t obj_size); + HeapWord* par_allocate(size_t size, bool tlab) { + return allocate(size, tlab); + } + + + // Used by CMSStats to track direct allocation. The value is sampled and + // reset after each young gen collection. + size_t direct_allocated_words() const { return _direct_allocated_words; } + void reset_direct_allocated_words() { _direct_allocated_words = 0; } + + // Overrides for parallel promotion. + virtual oop par_promote(int thread_num, + oop obj, markOop m, size_t word_sz); + virtual void par_promote_alloc_done(int thread_num); + virtual void par_oop_since_save_marks_iterate_done(int thread_num); + + virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; + + // Inform this (non-young) generation that a promotion failure was + // encountered during a collection of a younger generation that + // promotes into this generation. + virtual void promotion_failure_occurred(); + + bool should_collect(bool full, size_t size, bool tlab); + virtual bool should_concurrent_collect() const; + virtual bool is_too_full() const; + void collect(bool full, + bool clear_all_soft_refs, + size_t size, + bool tlab); + + HeapWord* expand_and_allocate(size_t word_size, + bool tlab, + bool parallel = false); + + // GC prologue and epilogue + void gc_prologue(bool full); + void gc_prologue_work(bool full, bool registerClosure, + ModUnionClosure* modUnionClosure); + void gc_epilogue(bool full); + void gc_epilogue_work(bool full); + + // Time since last GC of this generation + jlong time_of_last_gc(jlong now) { + return collector()->time_of_last_gc(now); + } + void update_time_of_last_gc(jlong now) { + collector()-> update_time_of_last_gc(now); + } + + // Allocation failure + void shrink(size_t bytes); + HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); + bool expand_and_ensure_spooling_space(PromotionInfo* promo); + + // Iteration support and related enquiries + void save_marks(); + bool no_allocs_since_save_marks(); + + // Iteration support specific to CMS generations + void save_sweep_limit(); + + // More iteration support + virtual void oop_iterate(ExtendedOopClosure* cl); + virtual void safe_object_iterate(ObjectClosure* cl); + virtual void object_iterate(ObjectClosure* cl); + + // Need to declare the full complement of closures, whether we'll + // override them or not, or get message from the compiler: + // oop_since_save_marks_iterate_nv hides virtual function... + #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ + void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); + ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) + + // Smart allocation XXX -- move to CFLSpace? + void setNearLargestChunk(); + bool isNearLargestChunk(HeapWord* addr); + + // Get the chunk at the end of the space. Delegates to + // the space. + FreeChunk* find_chunk_at_end(); + + void post_compact(); + + // Debugging + void prepare_for_verify(); + void verify(); + void print_statistics() PRODUCT_RETURN; + + // Performance Counters support + virtual void update_counters(); + virtual void update_counters(size_t used); + void initialize_performance_counters(); + CollectorCounters* counters() { return collector()->counters(); } + + // Support for parallel remark of survivor space + void* get_data_recorder(int thr_num) { + //Delegate to collector + return collector()->get_data_recorder(thr_num); + } + void sample_eden_chunk() { + //Delegate to collector + return collector()->sample_eden_chunk(); + } + + // Printing + const char* name() const; + virtual const char* short_name() const { return "CMS"; } + void print() const; + void printOccupancy(const char* s); + + // Resize the generation after a compacting GC. The + // generation can be treated as a contiguous space + // after the compaction. + virtual void compute_new_size(); + // Resize the generation after a non-compacting + // collection. + void compute_new_size_free_list(); +}; + +// +// Closures of various sorts used by CMS to accomplish its work +// + +// This closure is used to do concurrent marking from the roots +// following the first checkpoint. +class MarkFromRootsClosure: public BitMapClosure { + CMSCollector* _collector; + MemRegion _span; + CMSBitMap* _bitMap; + CMSBitMap* _mut; + CMSMarkStack* _markStack; + bool _yield; + int _skipBits; + HeapWord* _finger; + HeapWord* _threshold; + DEBUG_ONLY(bool _verifying;) + + public: + MarkFromRootsClosure(CMSCollector* collector, MemRegion span, + CMSBitMap* bitMap, + CMSMarkStack* markStack, + bool should_yield, bool verifying = false); + bool do_bit(size_t offset); + void reset(HeapWord* addr); + inline void do_yield_check(); + + private: + void scanOopsInOop(HeapWord* ptr); + void do_yield_work(); +}; + +// This closure is used to do concurrent multi-threaded +// marking from the roots following the first checkpoint. +// XXX This should really be a subclass of The serial version +// above, but i have not had the time to refactor things cleanly. +class Par_MarkFromRootsClosure: public BitMapClosure { + CMSCollector* _collector; + MemRegion _whole_span; + MemRegion _span; + CMSBitMap* _bit_map; + CMSBitMap* _mut; + OopTaskQueue* _work_queue; + CMSMarkStack* _overflow_stack; + int _skip_bits; + HeapWord* _finger; + HeapWord* _threshold; + CMSConcMarkingTask* _task; + public: + Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, + MemRegion span, + CMSBitMap* bit_map, + OopTaskQueue* work_queue, + CMSMarkStack* overflow_stack); + bool do_bit(size_t offset); + inline void do_yield_check(); + + private: + void scan_oops_in_oop(HeapWord* ptr); + void do_yield_work(); + bool get_work_from_overflow_stack(); +}; + +// The following closures are used to do certain kinds of verification of +// CMS marking. +class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { + CMSCollector* _collector; + MemRegion _span; + CMSBitMap* _verification_bm; + CMSBitMap* _cms_bm; + CMSMarkStack* _mark_stack; + protected: + void do_oop(oop p); + template inline void do_oop_work(T *p) { + oop obj = oopDesc::load_decode_heap_oop(p); + do_oop(obj); + } + public: + PushAndMarkVerifyClosure(CMSCollector* cms_collector, + MemRegion span, + CMSBitMap* verification_bm, + CMSBitMap* cms_bm, + CMSMarkStack* mark_stack); + void do_oop(oop* p); + void do_oop(narrowOop* p); + + // Deal with a stack overflow condition + void handle_stack_overflow(HeapWord* lost); +}; + +class MarkFromRootsVerifyClosure: public BitMapClosure { + CMSCollector* _collector; + MemRegion _span; + CMSBitMap* _verification_bm; + CMSBitMap* _cms_bm; + CMSMarkStack* _mark_stack; + HeapWord* _finger; + PushAndMarkVerifyClosure _pam_verify_closure; + public: + MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, + CMSBitMap* verification_bm, + CMSBitMap* cms_bm, + CMSMarkStack* mark_stack); + bool do_bit(size_t offset); + void reset(HeapWord* addr); +}; + + +// This closure is used to check that a certain set of bits is +// "empty" (i.e. the bit vector doesn't have any 1-bits). +class FalseBitMapClosure: public BitMapClosure { + public: + bool do_bit(size_t offset) { + guarantee(false, "Should not have a 1 bit"); + return true; + } +}; + +// A version of ObjectClosure with "memory" (see _previous_address below) +class UpwardsObjectClosure: public BoolObjectClosure { + HeapWord* _previous_address; + public: + UpwardsObjectClosure() : _previous_address(NULL) { } + void set_previous(HeapWord* addr) { _previous_address = addr; } + HeapWord* previous() { return _previous_address; } + // A return value of "true" can be used by the caller to decide + // if this object's end should *NOT* be recorded in + // _previous_address above. + virtual bool do_object_bm(oop obj, MemRegion mr) = 0; +}; + +// This closure is used during the second checkpointing phase +// to rescan the marked objects on the dirty cards in the mod +// union table and the card table proper. It's invoked via +// MarkFromDirtyCardsClosure below. It uses either +// [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) +// declared in genOopClosures.hpp to accomplish some of its work. +// In the parallel case the bitMap is shared, so access to +// it needs to be suitably synchronized for updates by embedded +// closures that update it; however, this closure itself only +// reads the bit_map and because it is idempotent, is immune to +// reading stale values. +class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { + #ifdef ASSERT + CMSCollector* _collector; + MemRegion _span; + union { + CMSMarkStack* _mark_stack; + OopTaskQueue* _work_queue; + }; + #endif // ASSERT + bool _parallel; + CMSBitMap* _bit_map; + union { + MarkRefsIntoAndScanClosure* _scan_closure; + Par_MarkRefsIntoAndScanClosure* _par_scan_closure; + }; + + public: + ScanMarkedObjectsAgainClosure(CMSCollector* collector, + MemRegion span, + ReferenceProcessor* rp, + CMSBitMap* bit_map, + CMSMarkStack* mark_stack, + MarkRefsIntoAndScanClosure* cl): + #ifdef ASSERT + _collector(collector), + _span(span), + _mark_stack(mark_stack), + #endif // ASSERT + _parallel(false), + _bit_map(bit_map), + _scan_closure(cl) { } + + ScanMarkedObjectsAgainClosure(CMSCollector* collector, + MemRegion span, + ReferenceProcessor* rp, + CMSBitMap* bit_map, + OopTaskQueue* work_queue, + Par_MarkRefsIntoAndScanClosure* cl): + #ifdef ASSERT + _collector(collector), + _span(span), + _work_queue(work_queue), + #endif // ASSERT + _parallel(true), + _bit_map(bit_map), + _par_scan_closure(cl) { } + + bool do_object_b(oop obj) { + guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); + return false; + } + bool do_object_bm(oop p, MemRegion mr); +}; + +// This closure is used during the second checkpointing phase +// to rescan the marked objects on the dirty cards in the mod +// union table and the card table proper. It invokes +// ScanMarkedObjectsAgainClosure above to accomplish much of its work. +// In the parallel case, the bit map is shared and requires +// synchronized access. +class MarkFromDirtyCardsClosure: public MemRegionClosure { + CompactibleFreeListSpace* _space; + ScanMarkedObjectsAgainClosure _scan_cl; + size_t _num_dirty_cards; + + public: + MarkFromDirtyCardsClosure(CMSCollector* collector, + MemRegion span, + CompactibleFreeListSpace* space, + CMSBitMap* bit_map, + CMSMarkStack* mark_stack, + MarkRefsIntoAndScanClosure* cl): + _space(space), + _num_dirty_cards(0), + _scan_cl(collector, span, collector->ref_processor(), bit_map, + mark_stack, cl) { } + + MarkFromDirtyCardsClosure(CMSCollector* collector, + MemRegion span, + CompactibleFreeListSpace* space, + CMSBitMap* bit_map, + OopTaskQueue* work_queue, + Par_MarkRefsIntoAndScanClosure* cl): + _space(space), + _num_dirty_cards(0), + _scan_cl(collector, span, collector->ref_processor(), bit_map, + work_queue, cl) { } + + void do_MemRegion(MemRegion mr); + void set_space(CompactibleFreeListSpace* space) { _space = space; } + size_t num_dirty_cards() { return _num_dirty_cards; } +}; + +// This closure is used in the non-product build to check +// that there are no MemRegions with a certain property. +class FalseMemRegionClosure: public MemRegionClosure { + void do_MemRegion(MemRegion mr) { + guarantee(!mr.is_empty(), "Shouldn't be empty"); + guarantee(false, "Should never be here"); + } +}; + +// This closure is used during the precleaning phase +// to "carefully" rescan marked objects on dirty cards. +// It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp +// to accomplish some of its work. +class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { + CMSCollector* _collector; + MemRegion _span; + bool _yield; + Mutex* _freelistLock; + CMSBitMap* _bitMap; + CMSMarkStack* _markStack; + MarkRefsIntoAndScanClosure* _scanningClosure; + + public: + ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, + MemRegion span, + CMSBitMap* bitMap, + CMSMarkStack* markStack, + MarkRefsIntoAndScanClosure* cl, + bool should_yield): + _collector(collector), + _span(span), + _yield(should_yield), + _bitMap(bitMap), + _markStack(markStack), + _scanningClosure(cl) { + } + + void do_object(oop p) { + guarantee(false, "call do_object_careful instead"); + } + + size_t do_object_careful(oop p) { + guarantee(false, "Unexpected caller"); + return 0; + } + + size_t do_object_careful_m(oop p, MemRegion mr); + + void setFreelistLock(Mutex* m) { + _freelistLock = m; + _scanningClosure->set_freelistLock(m); + } + + private: + inline bool do_yield_check(); + + void do_yield_work(); +}; + +class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { + CMSCollector* _collector; + MemRegion _span; + bool _yield; + CMSBitMap* _bit_map; + CMSMarkStack* _mark_stack; + PushAndMarkClosure* _scanning_closure; + unsigned int _before_count; + + public: + SurvivorSpacePrecleanClosure(CMSCollector* collector, + MemRegion span, + CMSBitMap* bit_map, + CMSMarkStack* mark_stack, + PushAndMarkClosure* cl, + unsigned int before_count, + bool should_yield): + _collector(collector), + _span(span), + _yield(should_yield), + _bit_map(bit_map), + _mark_stack(mark_stack), + _scanning_closure(cl), + _before_count(before_count) + { } + + void do_object(oop p) { + guarantee(false, "call do_object_careful instead"); + } + + size_t do_object_careful(oop p); + + size_t do_object_careful_m(oop p, MemRegion mr) { + guarantee(false, "Unexpected caller"); + return 0; + } + + private: + inline void do_yield_check(); + void do_yield_work(); +}; + +// This closure is used to accomplish the sweeping work +// after the second checkpoint but before the concurrent reset +// phase. +// +// Terminology +// left hand chunk (LHC) - block of one or more chunks currently being +// coalesced. The LHC is available for coalescing with a new chunk. +// right hand chunk (RHC) - block that is currently being swept that is +// free or garbage that can be coalesced with the LHC. +// _inFreeRange is true if there is currently a LHC +// _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. +// _freeRangeInFreeLists is true if the LHC is in the free lists. +// _freeFinger is the address of the current LHC +class SweepClosure: public BlkClosureCareful { + CMSCollector* _collector; // collector doing the work + ConcurrentMarkSweepGeneration* _g; // Generation being swept + CompactibleFreeListSpace* _sp; // Space being swept + HeapWord* _limit;// the address at or above which the sweep should stop + // because we do not expect newly garbage blocks + // eligible for sweeping past that address. + Mutex* _freelistLock; // Free list lock (in space) + CMSBitMap* _bitMap; // Marking bit map (in + // generation) + bool _inFreeRange; // Indicates if we are in the + // midst of a free run + bool _freeRangeInFreeLists; + // Often, we have just found + // a free chunk and started + // a new free range; we do not + // eagerly remove this chunk from + // the free lists unless there is + // a possibility of coalescing. + // When true, this flag indicates + // that the _freeFinger below + // points to a potentially free chunk + // that may still be in the free lists + bool _lastFreeRangeCoalesced; + // free range contains chunks + // coalesced + bool _yield; + // Whether sweeping should be + // done with yields. For instance + // when done by the foreground + // collector we shouldn't yield. + HeapWord* _freeFinger; // When _inFreeRange is set, the + // pointer to the "left hand + // chunk" + size_t _freeRangeSize; + // When _inFreeRange is set, this + // indicates the accumulated size + // of the "left hand chunk" + NOT_PRODUCT( + size_t _numObjectsFreed; + size_t _numWordsFreed; + size_t _numObjectsLive; + size_t _numWordsLive; + size_t _numObjectsAlreadyFree; + size_t _numWordsAlreadyFree; + FreeChunk* _last_fc; + ) + private: + // Code that is common to a free chunk or garbage when + // encountered during sweeping. + void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); + // Process a free chunk during sweeping. + void do_already_free_chunk(FreeChunk *fc); + // Work method called when processing an already free or a + // freshly garbage chunk to do a lookahead and possibly a + // preemptive flush if crossing over _limit. + void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); + // Process a garbage chunk during sweeping. + size_t do_garbage_chunk(FreeChunk *fc); + // Process a live chunk during sweeping. + size_t do_live_chunk(FreeChunk* fc); + + // Accessors. + HeapWord* freeFinger() const { return _freeFinger; } + void set_freeFinger(HeapWord* v) { _freeFinger = v; } + bool inFreeRange() const { return _inFreeRange; } + void set_inFreeRange(bool v) { _inFreeRange = v; } + bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } + void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } + bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } + void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } + + // Initialize a free range. + void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); + // Return this chunk to the free lists. + void flush_cur_free_chunk(HeapWord* chunk, size_t size); + + // Check if we should yield and do so when necessary. + inline void do_yield_check(HeapWord* addr); + + // Yield + void do_yield_work(HeapWord* addr); + + // Debugging/Printing + void print_free_block_coalesced(FreeChunk* fc) const; + + public: + SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, + CMSBitMap* bitMap, bool should_yield); + ~SweepClosure() PRODUCT_RETURN; + + size_t do_blk_careful(HeapWord* addr); + void print() const { print_on(tty); } + void print_on(outputStream *st) const; +}; + +// Closures related to weak references processing + +// During CMS' weak reference processing, this is a +// work-routine/closure used to complete transitive +// marking of objects as live after a certain point +// in which an initial set has been completely accumulated. +// This closure is currently used both during the final +// remark stop-world phase, as well as during the concurrent +// precleaning of the discovered reference lists. +class CMSDrainMarkingStackClosure: public VoidClosure { + CMSCollector* _collector; + MemRegion _span; + CMSMarkStack* _mark_stack; + CMSBitMap* _bit_map; + CMSKeepAliveClosure* _keep_alive; + bool _concurrent_precleaning; + public: + CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, + CMSBitMap* bit_map, CMSMarkStack* mark_stack, + CMSKeepAliveClosure* keep_alive, + bool cpc): + _collector(collector), + _span(span), + _bit_map(bit_map), + _mark_stack(mark_stack), + _keep_alive(keep_alive), + _concurrent_precleaning(cpc) { + assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), + "Mismatch"); + } + + void do_void(); +}; + +// A parallel version of CMSDrainMarkingStackClosure above. +class CMSParDrainMarkingStackClosure: public VoidClosure { + CMSCollector* _collector; + MemRegion _span; + OopTaskQueue* _work_queue; + CMSBitMap* _bit_map; + CMSInnerParMarkAndPushClosure _mark_and_push; + + public: + CMSParDrainMarkingStackClosure(CMSCollector* collector, + MemRegion span, CMSBitMap* bit_map, + OopTaskQueue* work_queue): + _collector(collector), + _span(span), + _bit_map(bit_map), + _work_queue(work_queue), + _mark_and_push(collector, span, bit_map, work_queue) { } + + public: + void trim_queue(uint max); + void do_void(); +}; + +// Allow yielding or short-circuiting of reference list +// precleaning work. +class CMSPrecleanRefsYieldClosure: public YieldClosure { + CMSCollector* _collector; + void do_yield_work(); + public: + CMSPrecleanRefsYieldClosure(CMSCollector* collector): + _collector(collector) {} + virtual bool should_return(); +}; + + +// Convenience class that locks free list locks for given CMS collector +class FreelistLocker: public StackObj { + private: + CMSCollector* _collector; + public: + FreelistLocker(CMSCollector* collector): + _collector(collector) { + _collector->getFreelistLocks(); + } + + ~FreelistLocker() { + _collector->releaseFreelistLocks(); + } +}; + +// Mark all dead objects in a given space. +class MarkDeadObjectsClosure: public BlkClosure { + const CMSCollector* _collector; + const CompactibleFreeListSpace* _sp; + CMSBitMap* _live_bit_map; + CMSBitMap* _dead_bit_map; +public: + MarkDeadObjectsClosure(const CMSCollector* collector, + const CompactibleFreeListSpace* sp, + CMSBitMap *live_bit_map, + CMSBitMap *dead_bit_map) : + _collector(collector), + _sp(sp), + _live_bit_map(live_bit_map), + _dead_bit_map(dead_bit_map) {} + size_t do_blk(HeapWord* addr); +}; + +class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { + + public: + TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); +}; + + +#endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP