--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1822 @@
+/*
+ * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// 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 (modulo the PermGeneration), 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 CMSAdaptiveSizePolicy;
+class CMSConcMarkingTask;
+class CMSGCAdaptivePolicyCounters;
+class ConcurrentMarkSweepGeneration;
+class ConcurrentMarkSweepPolicy;
+class ConcurrentMarkSweepThread;
+class CompactibleFreeListSpace;
+class FreeChunk;
+class PromotionInfo;
+class ScanMarkedObjectsAgainCarefullyClosure;
+
+// 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;
+
+ // 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 expasion 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),
+ _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;
+ HeapWord** _array; // storage for array
+
+ public:
+ ChunkArray() : _index(0), _capacity(0), _array(NULL) {}
+ ChunkArray(HeapWord** a, size_t c):
+ _index(0), _capacity(c), _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(), "_index out of bounds");
+ return _index;
+ } // exclusive
+
+ HeapWord* nth(size_t n) {
+ assert(n < end(), "Out of bounds access");
+ return _array[n];
+ }
+
+ void reset() {
+ _index = 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;
+ }
+ }
+};
+
+//
+// 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_duration_per_mb;
+ 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;
+
+ unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
+
+ protected:
+
+ // Return a duty cycle that avoids wild oscillations, by limiting the amount
+ // of change between old_duty_cycle and new_duty_cycle (the latter is treated
+ // as a recommended value).
+ static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
+ unsigned int new_duty_cycle);
+ unsigned int icms_update_duty_cycle_impl();
+
+ 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; }
+ double cms_duration_per_mb() const { return _cms_duration_per_mb; }
+ 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.
+
+ // Returns the cms incremental mode duty cycle, as a percentage (0-100).
+ unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
+
+ // Update the duty cycle and return the new value.
+ unsigned int icms_update_duty_cycle();
+
+ // 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 {
+ MemRegion _span;
+ const CMSBitMap* _bit_map;
+
+ friend class CMSCollector;
+ protected:
+ void set_span(MemRegion span) { _span = span; }
+ public:
+ CMSIsAliveClosure(CMSBitMap* bit_map):
+ _bit_map(bit_map) { }
+
+ CMSIsAliveClosure(MemRegion span,
+ CMSBitMap* bit_map):
+ _span(span),
+ _bit_map(bit_map) { }
+ void do_object(oop obj) {
+ assert(false, "not to be invoked");
+ }
+ 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 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;
+
+ 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 accomodating overflow list above.
+ // This code will likely be revisited under RFE#4922830.
+ GrowableArray<oop>* _preserved_oop_stack;
+ GrowableArray<markOop>* _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;
+ unsigned int _collection_count_start;
+ // Should we unload classes this concurrent cycle?
+ // Set in response to a concurrent full gc request.
+ bool _unload_classes;
+ bool _unloaded_classes_last_cycle;
+ // Did we (allow) unload classes in the previous concurrent cycle?
+ bool cms_unloaded_classes_last_cycle() const {
+ return _unloaded_classes_last_cycle || CMSClassUnloadingEnabled;
+ }
+
+ // 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; }
+
+ // Check whether the gc time limit has been
+ // exceeded and set the size policy flag
+ // appropriately.
+ void check_gc_time_limit();
+ // XXX Move these to CMSStats ??? FIX ME !!!
+ elapsedTimer _sweep_timer;
+ AdaptivePaddedAverage _sweep_estimate;
+
+ protected:
+ ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
+ ConcurrentMarkSweepGeneration* _permGen; // perm gen
+ MemRegion _span; // span covering above two
+ CardTableRS* _ct; // card table
+
+ // CMS marking support structures
+ CMSBitMap _markBitMap;
+ CMSBitMap _modUnionTable;
+ CMSMarkStack _markStack;
+ CMSMarkStack _revisitStack; // used to keep track of klassKlass objects
+ // to revisit
+ CMSBitMap _perm_gen_verify_bit_map; // Mark bit map for perm gen verification support.
+
+ 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_ovflw;
+ size_t _par_kac_ovflw;
+ NOT_PRODUCT(size_t _num_par_pushes;)
+
+ // ("Weak") Reference processing support
+ ReferenceProcessor* _ref_processor;
+ CMSIsAliveClosure _is_alive_closure;
+ // keep this textually after _markBitMap; c'tor dependency
+
+ ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
+ ModUnionClosure _modUnionClosure;
+ 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
+ enum CollectorState {
+ Resizing = 0,
+ Resetting = 1,
+ Idling = 2,
+ InitialMarking = 3,
+ Marking = 4,
+ Precleaning = 5,
+ AbortablePreclean = 6,
+ FinalMarking = 7,
+ Sweeping = 8
+ };
+ static CollectorState _collectorState;
+
+ // State related to prologue/epilogue invocation for my generations
+ bool _between_prologue_and_epilogue;
+
+ // Signalling/State related to coordination between fore- and backgroud 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;
+ uint _sweepCount;
+ // number of full gc's since the last concurrent gc.
+ uint _full_gcs_since_conc_gc;
+
+ // if occupancy exceeds this, start a new gc cycle
+ double _initiatingOccupancy;
+ // occupancy used for bootstrapping stats
+ double _bootstrap_occupancy;
+
+ // timer
+ elapsedTimer _timer;
+
+ // Timing, allocation and promotion statistics, used for scheduling.
+ CMSStats _stats;
+
+ // Allocation limits installed in the young gen, used only in
+ // CMSIncrementalMode. When an allocation in the young gen would cross one of
+ // these limits, the cms generation is notified and the cms thread is started
+ // or stopped, respectively.
+ HeapWord* _icms_start_limit;
+ HeapWord* _icms_stop_limit;
+
+ enum CMS_op_type {
+ CMS_op_checkpointRootsInitial,
+ CMS_op_checkpointRootsFinal
+ };
+
+ void do_CMS_operation(CMS_op_type op);
+ 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
+ Generation* _young_gen; // the younger gen
+ HeapWord** _top_addr; // ... Top of Eden
+ HeapWord** _end_addr; // ... End of Eden
+ 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;
+
+ // 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);
+ 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
+
+ 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; }
+
+ // CMS work methods
+ void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
+
+ // a return value of false indicates failure due to stack overflow
+ bool markFromRootsWork(bool asynch); // concurrent marking work
+
+ public: // FIX ME!!! only for testing
+ bool do_marking_st(bool asynch); // single-threaded marking
+ bool do_marking_mt(bool asynch); // 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 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);
+ // Resets (i.e. clears) the per-thread plab sample vectors
+ void reset_survivor_plab_arrays();
+
+ // final (second) checkpoint work
+ void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
+ bool init_mark_was_synchronous);
+ // 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(bool asynch, bool clear_all_soft_refs);
+
+ // concurrent sweeping work
+ void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
+
+ // (concurrent) resetting of support data structures
+ void reset(bool asynch);
+
+ // Clear _expansion_cause fields of constituent generations
+ void clear_expansion_cause();
+
+ // An auxilliary method used to record the ends of
+ // used regions of each generation to limit the extent of sweep
+ void save_sweep_limits();
+
+ // Resize the generations included in the collector.
+ void compute_new_size();
+
+ // A work method used by foreground collection to determine
+ // what type of collection (compacting or not, continuing or fresh)
+ // it should do.
+ void decide_foreground_collection_type(bool clear_all_soft_refs,
+ bool* should_compact, bool* should_start_over);
+
+ // A work method used by the foreground collector to do
+ // a mark-sweep-compact.
+ void do_compaction_work(bool clear_all_soft_refs);
+
+ // A work method used by the foreground collector to do
+ // a mark-sweep, after taking over from a possibly on-going
+ // concurrent mark-sweep collection.
+ void do_mark_sweep_work(bool clear_all_soft_refs,
+ CollectorState first_state, bool should_start_over);
+
+ // If the backgrould 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();
+
+ // Incremental mode triggering: recompute the icms duty cycle and set the
+ // allocation limits in the young gen.
+ void icms_update_allocation_limits();
+
+ 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,
+ ConcurrentMarkSweepGeneration* permGen,
+ 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; }
+ double initiatingOccupancy() const { return _initiatingOccupancy; }
+
+ 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();)
+
+ // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
+ bool shouldConcurrentCollect();
+
+ void collect(bool full,
+ bool clear_all_soft_refs,
+ size_t size,
+ bool tlab);
+ void collect_in_background(bool clear_all_soft_refs);
+ void collect_in_foreground(bool clear_all_soft_refs);
+
+ // In support of ExplicitGCInvokesConcurrent
+ static void request_full_gc(unsigned int full_gc_count);
+ // Should we unload classes in a particular concurrent cycle?
+ bool cms_should_unload_classes() const {
+ assert(!_unload_classes || ExplicitGCInvokesConcurrentAndUnloadsClasses,
+ "Inconsistency; see CR 6541037");
+ return _unload_classes || CMSClassUnloadingEnabled;
+ }
+
+ 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);
+
+ HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
+ size_t word_size);
+
+ void getFreelistLocks() const;
+ void releaseFreelistLocks() const;
+ bool haveFreelistLocks() const;
+
+ // 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);
+
+ CMSBitMap* markBitMap() { return &_markBitMap; }
+ void directAllocated(HeapWord* start, size_t size);
+
+ // main CMS steps and related support
+ void checkpointRootsInitial(bool asynch);
+ bool markFromRoots(bool asynch); // a return value of false indicates failure
+ // due to stack overflow
+ void preclean();
+ void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
+ bool init_mark_was_synchronous);
+ void sweep(bool asynch);
+
+ // Check that the currently executing thread is the expected
+ // one (foreground collector or background collector).
+ void check_correct_thread_executing() PRODUCT_RETURN;
+ // XXXPERM void print_statistics() 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; }
+ uint sweepCount() const { return _sweepCount; }
+ void incrementSweepCount() { _sweepCount++; }
+
+ // Timers/stats for gc scheduling and incremental mode pacing.
+ CMSStats& stats() { return _stats; }
+
+ // Convenience methods that check whether CMSIncrementalMode is enabled and
+ // forward to the corresponding methods in ConcurrentMarkSweepThread.
+ static void start_icms();
+ static void stop_icms(); // Called at the end of the cms cycle.
+ static void disable_icms(); // Called before a foreground collection.
+ static void enable_icms(); // Called after a foreground collection.
+ void icms_wait(); // Called at yield points.
+
+ // Adaptive size policy
+ CMSAdaptiveSizePolicy* size_policy();
+ CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
+
+ // debugging
+ void verify(bool);
+ bool verify_after_remark();
+ 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; }
+
+ // Get the bit map with a perm gen "deadness" information.
+ CMSBitMap* perm_gen_verify_bit_map() { return &_perm_gen_verify_bit_map; }
+
+ // Initialization errors
+ bool completed_initialization() { return _completed_initialization; }
+};
+
+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(
+ int _numObjectsPromoted;
+ int _numWordsPromoted;
+ int _numObjectsAllocated;
+ int _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;
+ }
+
+ private:
+ // For parallel young-gen GC support.
+ CMSParGCThreadState** _par_gc_thread_states;
+
+ // Reason generation was expanded
+ CMSExpansionCause::Cause _expansion_cause;
+
+ // accessors
+ void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
+ CMSExpansionCause::Cause expansion_cause() { return _expansion_cause; }
+
+ // In support of MinChunkSize being larger than min object size
+ const double _dilatation_factor;
+
+ enum CollectionTypes {
+ Concurrent_collection_type = 0,
+ MS_foreground_collection_type = 1,
+ MSC_foreground_collection_type = 2,
+ Unknown_collection_type = 3
+ };
+
+ CollectionTypes _debug_collection_type;
+
+ protected:
+ // Grow generation by specified size (returns false if unable to grow)
+ bool grow_by(size_t bytes);
+ // Grow generation to reserved size.
+ bool grow_to_reserved();
+ // Shrink generation by specified size (returns false if unable to shrink)
+ virtual void shrink_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;
+
+ 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; }
+
+ // Adaptive size policy
+ CMSAdaptiveSizePolicy* size_policy();
+
+ 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 false;
+ }
+
+ // Override
+ virtual void ref_processor_init();
+
+ void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
+
+ // Space enquiries
+ size_t capacity() const;
+ size_t used() const;
+ size_t free() const;
+ double occupancy() { return ((double)used())/((double)capacity()); }
+ size_t contiguous_available() const;
+ size_t unsafe_max_alloc_nogc() const;
+
+ // over-rides
+ MemRegion used_region() const;
+ 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. This is better than using th policy's should_collect_gen0_first()
+ // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
+ virtual bool full_collects_younger_generations() const {
+ return UseCMSCompactAtFullCollection && !CollectGen0First;
+ }
+
+ void space_iterate(SpaceClosure* blk, bool usedOnly = false);
+
+ // Support for compaction
+ CompactibleSpace* first_compaction_space() const;
+ // Adjust quantites 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, oop* ref);
+ HeapWord* par_allocate(size_t size, bool tlab) {
+ return allocate(size, tlab);
+ }
+
+ // Incremental mode triggering.
+ HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
+ size_t word_size);
+
+ // 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);
+ // This one should not be called for CMS.
+ virtual void par_promote_alloc_undo(int thread_num,
+ HeapWord* obj, 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,
+ bool younger_handles_promotion_failure) const;
+
+ bool should_collect(bool full, size_t size, bool tlab);
+ // XXXPERM
+ bool shouldConcurrentCollect(double initiatingOccupancy); // XXXPERM
+ 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 expand(size_t bytes, size_t expand_bytes,
+ CMSExpansionCause::Cause cause);
+ 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();
+ void object_iterate_since_last_GC(ObjectClosure* cl);
+ void younger_refs_iterate(OopsInGenClosure* cl);
+
+ // Iteration support specific to CMS generations
+ void save_sweep_limit();
+
+ // More iteration support
+ virtual void oop_iterate(MemRegion mr, OopClosure* cl);
+ virtual void oop_iterate(OopClosure* 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. Delagates to
+ // the space.
+ FreeChunk* find_chunk_at_end();
+
+ // Overriding of unused functionality (sharing not yet supported with CMS)
+ void pre_adjust_pointers();
+ void post_compact();
+
+ // Debugging
+ void prepare_for_verify();
+ void verify(bool allow_dirty);
+ 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);
+ }
+
+ // Printing
+ const char* name() const;
+ virtual const char* short_name() const { return "CMS"; }
+ void print() const;
+ void printOccupancy(const char* s);
+ bool must_be_youngest() const { return false; }
+ bool must_be_oldest() const { return true; }
+
+ void compute_new_size();
+
+ CollectionTypes debug_collection_type() { return _debug_collection_type; }
+ void rotate_debug_collection_type();
+};
+
+class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
+
+ // Return the size policy from the heap's collector
+ // policy casted to CMSAdaptiveSizePolicy*.
+ CMSAdaptiveSizePolicy* cms_size_policy() const;
+
+ // Resize the generation based on the adaptive size
+ // policy.
+ void resize(size_t cur_promo, size_t desired_promo);
+
+ // Return the GC counters from the collector policy
+ CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
+
+ virtual void shrink_by(size_t bytes);
+
+ public:
+ virtual void compute_new_size();
+ ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
+ int level, CardTableRS* ct,
+ bool use_adaptive_freelists,
+ FreeBlockDictionary::DictionaryChoice
+ dictionaryChoice) :
+ ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
+ use_adaptive_freelists, dictionaryChoice) {}
+
+ virtual const char* short_name() const { return "ASCMS"; }
+ virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
+
+ virtual void update_counters();
+ virtual void update_counters(size_t used);
+};
+
+//
+// Closures of various sorts used by CMS to accomplish its work
+//
+
+// This closure is used to check that a certain set of oops is empty.
+class FalseClosure: public OopClosure {
+ public:
+ void do_oop(oop* p) {
+ guarantee(false, "Should be an empty set");
+ }
+};
+
+// 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;
+ CMSMarkStack* _revisitStack;
+ bool _yield;
+ int _skipBits;
+ HeapWord* _finger;
+ HeapWord* _threshold;
+ DEBUG_ONLY(bool _verifying;)
+
+ public:
+ MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
+ CMSBitMap* bitMap,
+ CMSMarkStack* markStack,
+ CMSMarkStack* revisitStack,
+ bool should_yield, bool verifying = false);
+ void 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.
+// That willbe done for Dolphin.
+class Par_MarkFromRootsClosure: public BitMapClosure {
+ CMSCollector* _collector;
+ MemRegion _whole_span;
+ MemRegion _span;
+ CMSBitMap* _bit_map;
+ CMSBitMap* _mut;
+ OopTaskQueue* _work_queue;
+ CMSMarkStack* _overflow_stack;
+ CMSMarkStack* _revisit_stack;
+ bool _yield;
+ 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,
+ CMSMarkStack* revisit_stack,
+ bool should_yield);
+ void 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 OopClosure {
+ CMSCollector* _collector;
+ MemRegion _span;
+ CMSBitMap* _verification_bm;
+ CMSBitMap* _cms_bm;
+ CMSMarkStack* _mark_stack;
+ public:
+ PushAndMarkVerifyClosure(CMSCollector* cms_collector,
+ MemRegion span,
+ CMSBitMap* verification_bm,
+ CMSBitMap* cms_bm,
+ CMSMarkStack* mark_stack);
+ void do_oop(oop* 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);
+ void 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:
+ void do_bit(size_t offset) {
+ guarantee(false, "Should not have a 1 bit");
+ }
+};
+
+// 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,
+ CMSMarkStack* revisit_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,
+ CMSMarkStack* revisit_stack,
+ 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) { }
+
+ void do_object(oop obj) {
+ guarantee(false, "Call do_object_b(oop, MemRegion) instead");
+ }
+ 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,
+ CMSMarkStack* revisit_stack,
+ MarkRefsIntoAndScanClosure* cl):
+ _space(space),
+ _num_dirty_cards(0),
+ _scan_cl(collector, span, collector->ref_processor(), bit_map,
+ mark_stack, revisit_stack, cl) { }
+
+ MarkFromDirtyCardsClosure(CMSCollector* collector,
+ MemRegion span,
+ CompactibleFreeListSpace* space,
+ CMSBitMap* bit_map,
+ OopTaskQueue* work_queue,
+ CMSMarkStack* revisit_stack,
+ Par_MarkRefsIntoAndScanClosure* cl):
+ _space(space),
+ _num_dirty_cards(0),
+ _scan_cl(collector, span, collector->ref_processor(), bit_map,
+ work_queue, revisit_stack, 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,
+ CMSMarkStack* revisitStack,
+ 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;
+ 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 doPostIsFreeOrGarbageChunk(FreeChunk *fc,
+ size_t chunkSize);
+ // Process a free chunk during sweeping.
+ void doAlreadyFreeChunk(FreeChunk *fc);
+ // Process a garbage chunk during sweeping.
+ size_t doGarbageChunk(FreeChunk *fc);
+ // Process a live chunk during sweeping.
+ size_t doLiveChunk(FreeChunk* fc);
+
+ // Accessors.
+ HeapWord* freeFinger() const { return _freeFinger; }
+ void set_freeFinger(HeapWord* v) { _freeFinger = v; }
+ size_t freeRangeSize() const { return _freeRangeSize; }
+ void set_freeRangeSize(size_t v) { _freeRangeSize = 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 flushCurFreeChunk(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 record_free_block_coalesced(FreeChunk* fc) const PRODUCT_RETURN;
+
+ public:
+ SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
+ CMSBitMap* bitMap, bool should_yield);
+ ~SweepClosure();
+
+ size_t do_blk_careful(HeapWord* addr);
+};
+
+// 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.
+class CMSDrainMarkingStackClosure: public VoidClosure {
+ CMSCollector* _collector;
+ MemRegion _span;
+ CMSMarkStack* _mark_stack;
+ CMSBitMap* _bit_map;
+ CMSKeepAliveClosure* _keep_alive;
+ public:
+ CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
+ CMSBitMap* bit_map, CMSMarkStack* mark_stack,
+ CMSKeepAliveClosure* keep_alive):
+ _collector(collector),
+ _span(span),
+ _bit_map(bit_map),
+ _mark_stack(mark_stack),
+ _keep_alive(keep_alive) { }
+
+ 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
+// prelceaning 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);
+};