diff -r e45861098f5a -r fec48bf5a827 hotspot/src/share/vm/gc/cms/concurrentMarkSweepGeneration.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/hotspot/src/share/vm/gc/cms/concurrentMarkSweepGeneration.hpp Wed May 13 15:16:06 2015 +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