1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
27
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gSpaceCounters.hpp"
30 #include "gc_implementation/shared/gcStats.hpp"
31 #include "gc_implementation/shared/gcWhen.hpp"
32 #include "gc_implementation/shared/generationCounters.hpp"
33 #include "memory/freeBlockDictionary.hpp"
34 #include "memory/generation.hpp"
35 #include "memory/iterator.hpp"
36 #include "runtime/mutexLocker.hpp"
37 #include "runtime/virtualspace.hpp"
38 #include "services/memoryService.hpp"
39 #include "utilities/bitMap.inline.hpp"
40 #include "utilities/stack.inline.hpp"
41 #include "utilities/taskqueue.hpp"
42 #include "utilities/yieldingWorkgroup.hpp"
43
44 // ConcurrentMarkSweepGeneration is in support of a concurrent
45 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
46 // style. We assume, for now, that this generation is always the
47 // seniormost generation and for simplicity
48 // in the first implementation, that this generation is a single compactible
49 // space. Neither of these restrictions appears essential, and will be
50 // relaxed in the future when more time is available to implement the
51 // greater generality (and there's a need for it).
52 //
53 // Concurrent mode failures are currently handled by
54 // means of a sliding mark-compact.
55
56 class AdaptiveSizePolicy;
57 class CMSConcMarkingTask;
58 class CMSGCAdaptivePolicyCounters;
59 class CMSTracer;
60 class ConcurrentGCTimer;
61 class ConcurrentMarkSweepGeneration;
62 class ConcurrentMarkSweepPolicy;
63 class ConcurrentMarkSweepThread;
64 class CompactibleFreeListSpace;
65 class FreeChunk;
66 class PromotionInfo;
67 class ScanMarkedObjectsAgainCarefullyClosure;
68 class TenuredGeneration;
69 class SerialOldTracer;
70
71 // A generic CMS bit map. It's the basis for both the CMS marking bit map
72 // as well as for the mod union table (in each case only a subset of the
73 // methods are used). This is essentially a wrapper around the BitMap class,
74 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
75 // we have _shifter == 0. and for the mod union table we have
76 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
77 // XXX 64-bit issues in BitMap?
78 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
79 friend class VMStructs;
80
81 HeapWord* _bmStartWord; // base address of range covered by map
82 size_t _bmWordSize; // map size (in #HeapWords covered)
83 const int _shifter; // shifts to convert HeapWord to bit position
84 VirtualSpace _virtual_space; // underlying the bit map
85 BitMap _bm; // the bit map itself
86 public:
87 Mutex* const _lock; // mutex protecting _bm;
88
89 public:
90 // constructor
91 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
92
93 // allocates the actual storage for the map
94 bool allocate(MemRegion mr);
95 // field getter
96 Mutex* lock() const { return _lock; }
97 // locking verifier convenience function
98 void assert_locked() const PRODUCT_RETURN;
99
100 // inquiries
101 HeapWord* startWord() const { return _bmStartWord; }
102 size_t sizeInWords() const { return _bmWordSize; }
103 size_t sizeInBits() const { return _bm.size(); }
104 // the following is one past the last word in space
105 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
106
107 // reading marks
108 bool isMarked(HeapWord* addr) const;
109 bool par_isMarked(HeapWord* addr) const; // do not lock checks
110 bool isUnmarked(HeapWord* addr) const;
111 bool isAllClear() const;
112
113 // writing marks
114 void mark(HeapWord* addr);
115 // For marking by parallel GC threads;
116 // returns true if we did, false if another thread did
117 bool par_mark(HeapWord* addr);
118
119 void mark_range(MemRegion mr);
120 void par_mark_range(MemRegion mr);
121 void mark_large_range(MemRegion mr);
122 void par_mark_large_range(MemRegion mr);
123 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
124 void clear_range(MemRegion mr);
125 void par_clear_range(MemRegion mr);
126 void clear_large_range(MemRegion mr);
127 void par_clear_large_range(MemRegion mr);
128 void clear_all();
129 void clear_all_incrementally(); // Not yet implemented!!
130
131 NOT_PRODUCT(
132 // checks the memory region for validity
133 void region_invariant(MemRegion mr);
134 )
135
136 // iteration
137 void iterate(BitMapClosure* cl) {
138 _bm.iterate(cl);
139 }
140 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
141 void dirty_range_iterate_clear(MemRegionClosure* cl);
142 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
143
144 // auxiliary support for iteration
145 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
146 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
147 HeapWord* end_addr) const;
148 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
149 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
150 HeapWord* end_addr) const;
151 MemRegion getAndClearMarkedRegion(HeapWord* addr);
152 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
153 HeapWord* end_addr);
154
155 // conversion utilities
156 HeapWord* offsetToHeapWord(size_t offset) const;
157 size_t heapWordToOffset(HeapWord* addr) const;
158 size_t heapWordDiffToOffsetDiff(size_t diff) const;
159
160 void print_on_error(outputStream* st, const char* prefix) const;
161
162 // debugging
163 // is this address range covered by the bit-map?
164 NOT_PRODUCT(
165 bool covers(MemRegion mr) const;
166 bool covers(HeapWord* start, size_t size = 0) const;
167 )
168 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
169 };
170
171 // Represents a marking stack used by the CMS collector.
172 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
173 class CMSMarkStack: public CHeapObj<mtGC> {
174 //
175 friend class CMSCollector; // To get at expansion stats further below.
176 //
177
178 VirtualSpace _virtual_space; // Space for the stack
179 oop* _base; // Bottom of stack
180 size_t _index; // One more than last occupied index
181 size_t _capacity; // Max #elements
182 Mutex _par_lock; // An advisory lock used in case of parallel access
183 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run
184
185 protected:
186 size_t _hit_limit; // We hit max stack size limit
187 size_t _failed_double; // We failed expansion before hitting limit
188
189 public:
190 CMSMarkStack():
191 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
192 _hit_limit(0),
193 _failed_double(0) {}
194
195 bool allocate(size_t size);
196
197 size_t capacity() const { return _capacity; }
198
199 oop pop() {
200 if (!isEmpty()) {
201 return _base[--_index] ;
202 }
203 return NULL;
204 }
205
206 bool push(oop ptr) {
207 if (isFull()) {
208 return false;
209 } else {
210 _base[_index++] = ptr;
211 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
212 return true;
213 }
214 }
215
216 bool isEmpty() const { return _index == 0; }
217 bool isFull() const {
218 assert(_index <= _capacity, "buffer overflow");
219 return _index == _capacity;
220 }
221
222 size_t length() { return _index; }
223
224 // "Parallel versions" of some of the above
225 oop par_pop() {
226 // lock and pop
227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
228 return pop();
229 }
230
231 bool par_push(oop ptr) {
232 // lock and push
233 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
234 return push(ptr);
235 }
236
237 // Forcibly reset the stack, losing all of its contents.
238 void reset() {
239 _index = 0;
240 }
241
242 // Expand the stack, typically in response to an overflow condition.
243 void expand();
244
245 // Compute the least valued stack element.
246 oop least_value(HeapWord* low) {
247 oop least = (oop)low;
248 for (size_t i = 0; i < _index; i++) {
249 least = MIN2(least, _base[i]);
250 }
251 return least;
252 }
253
254 // Exposed here to allow stack expansion in || case.
255 Mutex* par_lock() { return &_par_lock; }
256 };
257
258 class CardTableRS;
259 class CMSParGCThreadState;
260
261 class ModUnionClosure: public MemRegionClosure {
262 protected:
263 CMSBitMap* _t;
264 public:
265 ModUnionClosure(CMSBitMap* t): _t(t) { }
266 void do_MemRegion(MemRegion mr);
267 };
268
269 class ModUnionClosurePar: public ModUnionClosure {
270 public:
271 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
272 void do_MemRegion(MemRegion mr);
273 };
274
275 // Survivor Chunk Array in support of parallelization of
276 // Survivor Space rescan.
277 class ChunkArray: public CHeapObj<mtGC> {
278 size_t _index;
279 size_t _capacity;
280 size_t _overflows;
281 HeapWord** _array; // storage for array
282
283 public:
284 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
285 ChunkArray(HeapWord** a, size_t c):
286 _index(0), _capacity(c), _overflows(0), _array(a) {}
287
288 HeapWord** array() { return _array; }
289 void set_array(HeapWord** a) { _array = a; }
290
291 size_t capacity() { return _capacity; }
292 void set_capacity(size_t c) { _capacity = c; }
293
294 size_t end() {
295 assert(_index <= capacity(),
296 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
297 _index, _capacity));
298 return _index;
299 } // exclusive
300
301 HeapWord* nth(size_t n) {
302 assert(n < end(), "Out of bounds access");
303 return _array[n];
304 }
305
306 void reset() {
307 _index = 0;
308 if (_overflows > 0 && PrintCMSStatistics > 1) {
309 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
310 _capacity, _overflows);
311 }
312 _overflows = 0;
313 }
314
315 void record_sample(HeapWord* p, size_t sz) {
316 // For now we do not do anything with the size
317 if (_index < _capacity) {
318 _array[_index++] = p;
319 } else {
320 ++_overflows;
321 assert(_index == _capacity,
322 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
323 "): out of bounds at overflow#" SIZE_FORMAT,
324 _index, _capacity, _overflows));
325 }
326 }
327 };
328
329 //
330 // Timing, allocation and promotion statistics for gc scheduling and incremental
331 // mode pacing. Most statistics are exponential averages.
332 //
333 class CMSStats VALUE_OBJ_CLASS_SPEC {
334 private:
335 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
336
337 // The following are exponential averages with factor alpha:
338 // avg = (100 - alpha) * avg + alpha * cur_sample
339 //
340 // The durations measure: end_time[n] - start_time[n]
341 // The periods measure: start_time[n] - start_time[n-1]
342 //
343 // The cms period and duration include only concurrent collections; time spent
344 // in foreground cms collections due to System.gc() or because of a failure to
345 // keep up are not included.
346 //
347 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
348 // real value, but is used only after the first period. A value of 100 is
349 // used for the first sample so it gets the entire weight.
350 unsigned int _saved_alpha; // 0-100
351 unsigned int _gc0_alpha;
352 unsigned int _cms_alpha;
353
354 double _gc0_duration;
355 double _gc0_period;
356 size_t _gc0_promoted; // bytes promoted per gc0
357 double _cms_duration;
358 double _cms_duration_pre_sweep; // time from initiation to start of sweep
359 double _cms_duration_per_mb;
360 double _cms_period;
361 size_t _cms_allocated; // bytes of direct allocation per gc0 period
362
363 // Timers.
364 elapsedTimer _cms_timer;
365 TimeStamp _gc0_begin_time;
366 TimeStamp _cms_begin_time;
367 TimeStamp _cms_end_time;
368
369 // Snapshots of the amount used in the CMS generation.
370 size_t _cms_used_at_gc0_begin;
371 size_t _cms_used_at_gc0_end;
372 size_t _cms_used_at_cms_begin;
373
374 // Used to prevent the duty cycle from being reduced in the middle of a cms
375 // cycle.
376 bool _allow_duty_cycle_reduction;
377
378 enum {
379 _GC0_VALID = 0x1,
380 _CMS_VALID = 0x2,
381 _ALL_VALID = _GC0_VALID | _CMS_VALID
382 };
383
384 unsigned int _valid_bits;
385
386 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
387
388 protected:
389
390 // Return a duty cycle that avoids wild oscillations, by limiting the amount
391 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
392 // as a recommended value).
393 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
394 unsigned int new_duty_cycle);
395 unsigned int icms_update_duty_cycle_impl();
396
397 // In support of adjusting of cms trigger ratios based on history
398 // of concurrent mode failure.
399 double cms_free_adjustment_factor(size_t free) const;
400 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
401
402 public:
403 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
404 unsigned int alpha = CMSExpAvgFactor);
405
406 // Whether or not the statistics contain valid data; higher level statistics
407 // cannot be called until this returns true (they require at least one young
408 // gen and one cms cycle to have completed).
409 bool valid() const;
410
411 // Record statistics.
412 void record_gc0_begin();
413 void record_gc0_end(size_t cms_gen_bytes_used);
414 void record_cms_begin();
415 void record_cms_end();
416
417 // Allow management of the cms timer, which must be stopped/started around
418 // yield points.
419 elapsedTimer& cms_timer() { return _cms_timer; }
420 void start_cms_timer() { _cms_timer.start(); }
421 void stop_cms_timer() { _cms_timer.stop(); }
422
423 // Basic statistics; units are seconds or bytes.
424 double gc0_period() const { return _gc0_period; }
425 double gc0_duration() const { return _gc0_duration; }
426 size_t gc0_promoted() const { return _gc0_promoted; }
427 double cms_period() const { return _cms_period; }
428 double cms_duration() const { return _cms_duration; }
429 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
430 size_t cms_allocated() const { return _cms_allocated; }
431
432 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
433
434 // Seconds since the last background cms cycle began or ended.
435 double cms_time_since_begin() const;
436 double cms_time_since_end() const;
437
438 // Higher level statistics--caller must check that valid() returns true before
439 // calling.
440
441 // Returns bytes promoted per second of wall clock time.
442 double promotion_rate() const;
443
444 // Returns bytes directly allocated per second of wall clock time.
445 double cms_allocation_rate() const;
446
447 // Rate at which space in the cms generation is being consumed (sum of the
448 // above two).
449 double cms_consumption_rate() const;
450
451 // Returns an estimate of the number of seconds until the cms generation will
452 // fill up, assuming no collection work is done.
453 double time_until_cms_gen_full() const;
454
455 // Returns an estimate of the number of seconds remaining until
456 // the cms generation collection should start.
457 double time_until_cms_start() const;
458
459 // End of higher level statistics.
460
461 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
462 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
463
464 // Update the duty cycle and return the new value.
465 unsigned int icms_update_duty_cycle();
466
467 // Debugging.
468 void print_on(outputStream* st) const PRODUCT_RETURN;
469 void print() const { print_on(gclog_or_tty); }
470 };
471
472 // A closure related to weak references processing which
473 // we embed in the CMSCollector, since we need to pass
474 // it to the reference processor for secondary filtering
475 // of references based on reachability of referent;
476 // see role of _is_alive_non_header closure in the
477 // ReferenceProcessor class.
478 // For objects in the CMS generation, this closure checks
479 // if the object is "live" (reachable). Used in weak
480 // reference processing.
481 class CMSIsAliveClosure: public BoolObjectClosure {
482 const MemRegion _span;
483 const CMSBitMap* _bit_map;
484
485 friend class CMSCollector;
486 public:
487 CMSIsAliveClosure(MemRegion span,
488 CMSBitMap* bit_map):
489 _span(span),
490 _bit_map(bit_map) {
491 assert(!span.is_empty(), "Empty span could spell trouble");
492 }
493
494 bool do_object_b(oop obj);
495 };
496
497
498 // Implements AbstractRefProcTaskExecutor for CMS.
499 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
500 public:
501
502 CMSRefProcTaskExecutor(CMSCollector& collector)
503 : _collector(collector)
504 { }
505
506 // Executes a task using worker threads.
507 virtual void execute(ProcessTask& task);
508 virtual void execute(EnqueueTask& task);
509 private:
510 CMSCollector& _collector;
511 };
512
513
514 class CMSCollector: public CHeapObj<mtGC> {
515 friend class VMStructs;
516 friend class ConcurrentMarkSweepThread;
517 friend class ConcurrentMarkSweepGeneration;
518 friend class CompactibleFreeListSpace;
519 friend class CMSParMarkTask;
520 friend class CMSParInitialMarkTask;
521 friend class CMSParRemarkTask;
522 friend class CMSConcMarkingTask;
523 friend class CMSRefProcTaskProxy;
524 friend class CMSRefProcTaskExecutor;
525 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
526 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
527 friend class PushOrMarkClosure; // to access _restart_addr
528 friend class Par_PushOrMarkClosure; // to access _restart_addr
529 friend class MarkFromRootsClosure; // -- ditto --
530 // ... and for clearing cards
531 friend class Par_MarkFromRootsClosure; // to access _restart_addr
532 // ... and for clearing cards
533 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
534 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
535 friend class PushAndMarkVerifyClosure; // -- ditto --
536 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
537 friend class PushAndMarkClosure; // -- ditto --
538 friend class Par_PushAndMarkClosure; // -- ditto --
539 friend class CMSKeepAliveClosure; // -- ditto --
540 friend class CMSDrainMarkingStackClosure; // -- ditto --
541 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
542 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
543 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
544 friend class VM_CMS_Operation;
545 friend class VM_CMS_Initial_Mark;
546 friend class VM_CMS_Final_Remark;
547 friend class TraceCMSMemoryManagerStats;
548
549 private:
550 jlong _time_of_last_gc;
551 void update_time_of_last_gc(jlong now) {
552 _time_of_last_gc = now;
553 }
554
555 OopTaskQueueSet* _task_queues;
556
557 // Overflow list of grey objects, threaded through mark-word
558 // Manipulated with CAS in the parallel/multi-threaded case.
559 oop _overflow_list;
560 // The following array-pair keeps track of mark words
561 // displaced for accommodating overflow list above.
562 // This code will likely be revisited under RFE#4922830.
563 Stack<oop, mtGC> _preserved_oop_stack;
564 Stack<markOop, mtGC> _preserved_mark_stack;
565
566 int* _hash_seed;
567
568 // In support of multi-threaded concurrent phases
569 YieldingFlexibleWorkGang* _conc_workers;
570
571 // Performance Counters
572 CollectorCounters* _gc_counters;
573
574 // Initialization Errors
575 bool _completed_initialization;
576
577 // In support of ExplicitGCInvokesConcurrent
578 static bool _full_gc_requested;
579 static GCCause::Cause _full_gc_cause;
580 unsigned int _collection_count_start;
581
582 // Should we unload classes this concurrent cycle?
583 bool _should_unload_classes;
584 unsigned int _concurrent_cycles_since_last_unload;
585 unsigned int concurrent_cycles_since_last_unload() const {
586 return _concurrent_cycles_since_last_unload;
587 }
588 // Did we (allow) unload classes in the previous concurrent cycle?
589 bool unloaded_classes_last_cycle() const {
590 return concurrent_cycles_since_last_unload() == 0;
591 }
592 // Root scanning options for perm gen
593 int _roots_scanning_options;
594 int roots_scanning_options() const { return _roots_scanning_options; }
595 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
596 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
597
598 // Verification support
599 CMSBitMap _verification_mark_bm;
600 void verify_after_remark_work_1();
601 void verify_after_remark_work_2();
602
603 // True if any verification flag is on.
604 bool _verifying;
605 bool verifying() const { return _verifying; }
606 void set_verifying(bool v) { _verifying = v; }
607
608 // Collector policy
609 ConcurrentMarkSweepPolicy* _collector_policy;
610 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
611
612 void set_did_compact(bool v);
613
614 // XXX Move these to CMSStats ??? FIX ME !!!
615 elapsedTimer _inter_sweep_timer; // Time between sweeps
616 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
617 // Padded decaying average estimates of the above
618 AdaptivePaddedAverage _inter_sweep_estimate;
619 AdaptivePaddedAverage _intra_sweep_estimate;
620
621 CMSTracer* _gc_tracer_cm;
622 ConcurrentGCTimer* _gc_timer_cm;
623
624 bool _cms_start_registered;
625
626 GCHeapSummary _last_heap_summary;
627 MetaspaceSummary _last_metaspace_summary;
628
629 void register_foreground_gc_start(GCCause::Cause cause);
630 void register_gc_start(GCCause::Cause cause);
631 void register_gc_end();
632 void save_heap_summary();
633 void report_heap_summary(GCWhen::Type when);
634
635 protected:
636 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
637 MemRegion _span; // Span covering above two
638 CardTableRS* _ct; // Card table
639
640 // CMS marking support structures
641 CMSBitMap _markBitMap;
642 CMSBitMap _modUnionTable;
643 CMSMarkStack _markStack;
644
645 HeapWord* _restart_addr; // In support of marking stack overflow
646 void lower_restart_addr(HeapWord* low);
647
648 // Counters in support of marking stack / work queue overflow handling:
649 // a non-zero value indicates certain types of overflow events during
650 // the current CMS cycle and could lead to stack resizing efforts at
651 // an opportune future time.
652 size_t _ser_pmc_preclean_ovflw;
653 size_t _ser_pmc_remark_ovflw;
654 size_t _par_pmc_remark_ovflw;
655 size_t _ser_kac_preclean_ovflw;
656 size_t _ser_kac_ovflw;
657 size_t _par_kac_ovflw;
658 NOT_PRODUCT(ssize_t _num_par_pushes;)
659
660 // ("Weak") Reference processing support.
661 ReferenceProcessor* _ref_processor;
662 CMSIsAliveClosure _is_alive_closure;
663 // Keep this textually after _markBitMap and _span; c'tor dependency.
664
665 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
666 ModUnionClosure _modUnionClosure;
667 ModUnionClosurePar _modUnionClosurePar;
668
669 // CMS abstract state machine
670 // initial_state: Idling
671 // next_state(Idling) = {Marking}
672 // next_state(Marking) = {Precleaning, Sweeping}
673 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
674 // next_state(AbortablePreclean) = {FinalMarking}
675 // next_state(FinalMarking) = {Sweeping}
676 // next_state(Sweeping) = {Resizing}
677 // next_state(Resizing) = {Resetting}
678 // next_state(Resetting) = {Idling}
679 // The numeric values below are chosen so that:
680 // . _collectorState <= Idling == post-sweep && pre-mark
681 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
682 // precleaning || abortablePrecleanb
683 public:
684 enum CollectorState {
685 Resizing = 0,
686 Resetting = 1,
687 Idling = 2,
688 InitialMarking = 3,
689 Marking = 4,
690 Precleaning = 5,
691 AbortablePreclean = 6,
692 FinalMarking = 7,
693 Sweeping = 8
694 };
695 protected:
696 static CollectorState _collectorState;
697
698 // State related to prologue/epilogue invocation for my generations
699 bool _between_prologue_and_epilogue;
700
701 // Signaling/State related to coordination between fore- and background GC
702 // Note: When the baton has been passed from background GC to foreground GC,
703 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
704 static bool _foregroundGCIsActive; // true iff foreground collector is active or
705 // wants to go active
706 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
707 // yet passed the baton to the foreground GC
708
709 // Support for CMSScheduleRemark (abortable preclean)
710 bool _abort_preclean;
711 bool _start_sampling;
712
713 int _numYields;
714 size_t _numDirtyCards;
715 size_t _sweep_count;
716 // Number of full gc's since the last concurrent gc.
717 uint _full_gcs_since_conc_gc;
718
719 // Occupancy used for bootstrapping stats
720 double _bootstrap_occupancy;
721
722 // Timer
723 elapsedTimer _timer;
724
725 // Timing, allocation and promotion statistics, used for scheduling.
726 CMSStats _stats;
727
728 // Allocation limits installed in the young gen, used only in
729 // CMSIncrementalMode. When an allocation in the young gen would cross one of
730 // these limits, the cms generation is notified and the cms thread is started
731 // or stopped, respectively.
732 HeapWord* _icms_start_limit;
733 HeapWord* _icms_stop_limit;
734
735 enum CMS_op_type {
736 CMS_op_checkpointRootsInitial,
737 CMS_op_checkpointRootsFinal
738 };
739
740 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
741 bool stop_world_and_do(CMS_op_type op);
742
743 OopTaskQueueSet* task_queues() { return _task_queues; }
744 int* hash_seed(int i) { return &_hash_seed[i]; }
745 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
746
747 // Support for parallelizing Eden rescan in CMS remark phase
748 void sample_eden(); // ... sample Eden space top
749
750 private:
751 // Support for parallelizing young gen rescan in CMS remark phase
752 Generation* _young_gen; // the younger gen
753 HeapWord** _top_addr; // ... Top of Eden
754 HeapWord** _end_addr; // ... End of Eden
755 Mutex* _eden_chunk_lock;
756 HeapWord** _eden_chunk_array; // ... Eden partitioning array
757 size_t _eden_chunk_index; // ... top (exclusive) of array
758 size_t _eden_chunk_capacity; // ... max entries in array
759
760 // Support for parallelizing survivor space rescan
761 HeapWord** _survivor_chunk_array;
762 size_t _survivor_chunk_index;
763 size_t _survivor_chunk_capacity;
764 size_t* _cursor;
765 ChunkArray* _survivor_plab_array;
766
767 // Support for marking stack overflow handling
768 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
769 bool par_take_from_overflow_list(size_t num,
770 OopTaskQueue* to_work_q,
771 int no_of_gc_threads);
772 void push_on_overflow_list(oop p);
773 void par_push_on_overflow_list(oop p);
774 // The following is, obviously, not, in general, "MT-stable"
775 bool overflow_list_is_empty() const;
776
777 void preserve_mark_if_necessary(oop p);
778 void par_preserve_mark_if_necessary(oop p);
779 void preserve_mark_work(oop p, markOop m);
780 void restore_preserved_marks_if_any();
781 NOT_PRODUCT(bool no_preserved_marks() const;)
782 // In support of testing overflow code
783 NOT_PRODUCT(int _overflow_counter;)
784 NOT_PRODUCT(bool simulate_overflow();) // Sequential
785 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
786
787 // CMS work methods
788 void checkpointRootsInitialWork(bool asynch); // Initial checkpoint work
789
790 // A return value of false indicates failure due to stack overflow
791 bool markFromRootsWork(bool asynch); // Concurrent marking work
792
793 public: // FIX ME!!! only for testing
794 bool do_marking_st(bool asynch); // Single-threaded marking
795 bool do_marking_mt(bool asynch); // Multi-threaded marking
796
797 private:
798
799 // Concurrent precleaning work
800 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
801 ScanMarkedObjectsAgainCarefullyClosure* cl);
802 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
803 ScanMarkedObjectsAgainCarefullyClosure* cl);
804 // Does precleaning work, returning a quantity indicative of
805 // the amount of "useful work" done.
806 size_t preclean_work(bool clean_refs, bool clean_survivors);
807 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
808 void abortable_preclean(); // Preclean while looking for possible abort
809 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
810 // Helper function for above; merge-sorts the per-thread plab samples
811 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
812 // Resets (i.e. clears) the per-thread plab sample vectors
813 void reset_survivor_plab_arrays();
814
815 // Final (second) checkpoint work
816 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
817 bool init_mark_was_synchronous);
818 // Work routine for parallel version of remark
819 void do_remark_parallel();
820 // Work routine for non-parallel version of remark
821 void do_remark_non_parallel();
822 // Reference processing work routine (during second checkpoint)
823 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
824
825 // Concurrent sweeping work
826 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
827
828 // (Concurrent) resetting of support data structures
829 void reset(bool asynch);
830
831 // Clear _expansion_cause fields of constituent generations
832 void clear_expansion_cause();
833
834 // An auxiliary method used to record the ends of
835 // used regions of each generation to limit the extent of sweep
836 void save_sweep_limits();
837
838 // A work method used by foreground collection to determine
839 // what type of collection (compacting or not, continuing or fresh)
840 // it should do.
841 void decide_foreground_collection_type(bool clear_all_soft_refs,
842 bool* should_compact, bool* should_start_over);
843
844 // A work method used by the foreground collector to do
845 // a mark-sweep-compact.
846 void do_compaction_work(bool clear_all_soft_refs);
847
848 // A work method used by the foreground collector to do
849 // a mark-sweep, after taking over from a possibly on-going
850 // concurrent mark-sweep collection.
851 void do_mark_sweep_work(bool clear_all_soft_refs,
852 CollectorState first_state, bool should_start_over);
853
854 // Work methods for reporting concurrent mode interruption or failure
855 bool is_external_interruption();
856 void report_concurrent_mode_interruption();
857
858 // If the background GC is active, acquire control from the background
859 // GC and do the collection.
860 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
861
862 // For synchronizing passing of control from background to foreground
863 // GC. waitForForegroundGC() is called by the background
864 // collector. It if had to wait for a foreground collection,
865 // it returns true and the background collection should assume
866 // that the collection was finished by the foreground
867 // collector.
868 bool waitForForegroundGC();
869
870 // Incremental mode triggering: recompute the icms duty cycle and set the
871 // allocation limits in the young gen.
872 void icms_update_allocation_limits();
873
874 size_t block_size_using_printezis_bits(HeapWord* addr) const;
875 size_t block_size_if_printezis_bits(HeapWord* addr) const;
876 HeapWord* next_card_start_after_block(HeapWord* addr) const;
877
878 void setup_cms_unloading_and_verification_state();
879 public:
880 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
881 CardTableRS* ct,
882 ConcurrentMarkSweepPolicy* cp);
883 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
884
885 ReferenceProcessor* ref_processor() { return _ref_processor; }
886 void ref_processor_init();
887
888 Mutex* bitMapLock() const { return _markBitMap.lock(); }
889 static CollectorState abstract_state() { return _collectorState; }
890
891 bool should_abort_preclean() const; // Whether preclean should be aborted.
892 size_t get_eden_used() const;
893 size_t get_eden_capacity() const;
894
895 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
896
897 // Locking checks
898 NOT_PRODUCT(static bool have_cms_token();)
899
900 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
901 bool shouldConcurrentCollect();
902
903 void collect(bool full,
904 bool clear_all_soft_refs,
905 size_t size,
906 bool tlab);
907 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
908 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
909
910 // In support of ExplicitGCInvokesConcurrent
911 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
912 // Should we unload classes in a particular concurrent cycle?
913 bool should_unload_classes() const {
914 return _should_unload_classes;
915 }
916 void update_should_unload_classes();
917
918 void direct_allocated(HeapWord* start, size_t size);
919
920 // Object is dead if not marked and current phase is sweeping.
921 bool is_dead_obj(oop obj) const;
922
923 // After a promotion (of "start"), do any necessary marking.
924 // If "par", then it's being done by a parallel GC thread.
925 // The last two args indicate if we need precise marking
926 // and if so the size of the object so it can be dirtied
927 // in its entirety.
928 void promoted(bool par, HeapWord* start,
929 bool is_obj_array, size_t obj_size);
930
931 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
932 size_t word_size);
933
934 void getFreelistLocks() const;
935 void releaseFreelistLocks() const;
936 bool haveFreelistLocks() const;
937
938 // Adjust size of underlying generation
939 void compute_new_size();
940
941 // GC prologue and epilogue
942 void gc_prologue(bool full);
943 void gc_epilogue(bool full);
944
945 jlong time_of_last_gc(jlong now) {
946 if (_collectorState <= Idling) {
947 // gc not in progress
948 return _time_of_last_gc;
949 } else {
950 // collection in progress
951 return now;
952 }
953 }
954
955 // Support for parallel remark of survivor space
956 void* get_data_recorder(int thr_num);
957 void sample_eden_chunk();
958
959 CMSBitMap* markBitMap() { return &_markBitMap; }
960 void directAllocated(HeapWord* start, size_t size);
961
962 // Main CMS steps and related support
963 void checkpointRootsInitial(bool asynch);
964 bool markFromRoots(bool asynch); // a return value of false indicates failure
965 // due to stack overflow
966 void preclean();
967 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
968 bool init_mark_was_synchronous);
969 void sweep(bool asynch);
970
971 // Check that the currently executing thread is the expected
972 // one (foreground collector or background collector).
973 static void check_correct_thread_executing() PRODUCT_RETURN;
974 // XXXPERM void print_statistics() PRODUCT_RETURN;
975
976 bool is_cms_reachable(HeapWord* addr);
977
978 // Performance Counter Support
979 CollectorCounters* counters() { return _gc_counters; }
980
981 // Timer stuff
982 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
983 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
984 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
985 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
986
987 int yields() { return _numYields; }
988 void resetYields() { _numYields = 0; }
989 void incrementYields() { _numYields++; }
990 void resetNumDirtyCards() { _numDirtyCards = 0; }
991 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
992 size_t numDirtyCards() { return _numDirtyCards; }
993
994 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
995 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
996 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
997 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
998 size_t sweep_count() const { return _sweep_count; }
999 void increment_sweep_count() { _sweep_count++; }
1000
1001 // Timers/stats for gc scheduling and incremental mode pacing.
1002 CMSStats& stats() { return _stats; }
1003
1004 // Convenience methods that check whether CMSIncrementalMode is enabled and
1005 // forward to the corresponding methods in ConcurrentMarkSweepThread.
1006 static void start_icms();
1007 static void stop_icms(); // Called at the end of the cms cycle.
1008 static void disable_icms(); // Called before a foreground collection.
1009 static void enable_icms(); // Called after a foreground collection.
1010 void icms_wait(); // Called at yield points.
1011
1012 // Adaptive size policy
1013 AdaptiveSizePolicy* size_policy();
1014
1015 static void print_on_error(outputStream* st);
1016
1017 // Debugging
1018 void verify();
1019 bool verify_after_remark(bool silent = VerifySilently);
1020 void verify_ok_to_terminate() const PRODUCT_RETURN;
1021 void verify_work_stacks_empty() const PRODUCT_RETURN;
1022 void verify_overflow_empty() const PRODUCT_RETURN;
1023
1024 // Convenience methods in support of debugging
1025 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1026 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1027
1028 // Accessors
1029 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1030 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1031
1032 // Initialization errors
1033 bool completed_initialization() { return _completed_initialization; }
1034
1035 void print_eden_and_survivor_chunk_arrays();
1036 };
1037
1038 class CMSExpansionCause : public AllStatic {
1039 public:
1040 enum Cause {
1041 _no_expansion,
1042 _satisfy_free_ratio,
1043 _satisfy_promotion,
1044 _satisfy_allocation,
1045 _allocate_par_lab,
1046 _allocate_par_spooling_space,
1047 _adaptive_size_policy
1048 };
1049 // Return a string describing the cause of the expansion.
1050 static const char* to_string(CMSExpansionCause::Cause cause);
1051 };
1052
1053 class ConcurrentMarkSweepGeneration: public CardGeneration {
1054 friend class VMStructs;
1055 friend class ConcurrentMarkSweepThread;
1056 friend class ConcurrentMarkSweep;
1057 friend class CMSCollector;
1058 protected:
1059 static CMSCollector* _collector; // the collector that collects us
1060 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1061
1062 // Performance Counters
1063 GenerationCounters* _gen_counters;
1064 GSpaceCounters* _space_counters;
1065
1066 // Words directly allocated, used by CMSStats.
1067 size_t _direct_allocated_words;
1068
1069 // Non-product stat counters
1070 NOT_PRODUCT(
1071 size_t _numObjectsPromoted;
1072 size_t _numWordsPromoted;
1073 size_t _numObjectsAllocated;
1074 size_t _numWordsAllocated;
1075 )
1076
1077 // Used for sizing decisions
1078 bool _incremental_collection_failed;
1079 bool incremental_collection_failed() {
1080 return _incremental_collection_failed;
1081 }
1082 void set_incremental_collection_failed() {
1083 _incremental_collection_failed = true;
1084 }
1085 void clear_incremental_collection_failed() {
1086 _incremental_collection_failed = false;
1087 }
1088
1089 // accessors
1090 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1091 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1092
1093 private:
1094 // For parallel young-gen GC support.
1095 CMSParGCThreadState** _par_gc_thread_states;
1096
1097 // Reason generation was expanded
1098 CMSExpansionCause::Cause _expansion_cause;
1099
1100 // In support of MinChunkSize being larger than min object size
1101 const double _dilatation_factor;
1102
1103 enum CollectionTypes {
1104 Concurrent_collection_type = 0,
1105 MS_foreground_collection_type = 1,
1106 MSC_foreground_collection_type = 2,
1107 Unknown_collection_type = 3
1108 };
1109
1110 CollectionTypes _debug_collection_type;
1111
1112 // True if a compacting collection was done.
1113 bool _did_compact;
1114 bool did_compact() { return _did_compact; }
1115
1116 // Fraction of current occupancy at which to start a CMS collection which
1117 // will collect this generation (at least).
1118 double _initiating_occupancy;
1119
1120 protected:
1121 // Shrink generation by specified size (returns false if unable to shrink)
1122 void shrink_free_list_by(size_t bytes);
1123
1124 // Update statistics for GC
1125 virtual void update_gc_stats(Generation* current_generation, bool full);
1126
1127 // Maximum available space in the generation (including uncommitted)
1128 // space.
1129 size_t max_available() const;
1130
1131 // getter and initializer for _initiating_occupancy field.
1132 double initiating_occupancy() const { return _initiating_occupancy; }
1133 void init_initiating_occupancy(intx io, uintx tr);
1134
1135 public:
1136 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1137 CardTableRS* ct,
1138 bool use_adaptive_freelists,
1139 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1140
1141 // Accessors
1142 CMSCollector* collector() const { return _collector; }
1143 static void set_collector(CMSCollector* collector) {
1144 assert(_collector == NULL, "already set");
1145 _collector = collector;
1146 }
1147 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1148
1149 Mutex* freelistLock() const;
1150
1151 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1152
1153 void set_did_compact(bool v) { _did_compact = v; }
1154
1155 bool refs_discovery_is_atomic() const { return false; }
1156 bool refs_discovery_is_mt() const {
1157 // Note: CMS does MT-discovery during the parallel-remark
1158 // phases. Use ReferenceProcessorMTMutator to make refs
1159 // discovery MT-safe during such phases or other parallel
1160 // discovery phases in the future. This may all go away
1161 // if/when we decide that refs discovery is sufficiently
1162 // rare that the cost of the CAS's involved is in the
1163 // noise. That's a measurement that should be done, and
1164 // the code simplified if that turns out to be the case.
1165 return ConcGCThreads > 1;
1166 }
1167
1168 // Override
1169 virtual void ref_processor_init();
1170
1171 // Grow generation by specified size (returns false if unable to grow)
1172 bool grow_by(size_t bytes);
1173 // Grow generation to reserved size.
1174 bool grow_to_reserved();
1175
1176 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1177
1178 // Space enquiries
1179 size_t capacity() const;
1180 size_t used() const;
1181 size_t free() const;
1182 double occupancy() const { return ((double)used())/((double)capacity()); }
1183 size_t contiguous_available() const;
1184 size_t unsafe_max_alloc_nogc() const;
1185
1186 // over-rides
1187 MemRegion used_region() const;
1188 MemRegion used_region_at_save_marks() const;
1189
1190 // Does a "full" (forced) collection invoked on this generation collect
1191 // all younger generations as well? Note that the second conjunct is a
1192 // hack to allow the collection of the younger gen first if the flag is
1193 // set.
1194 virtual bool full_collects_younger_generations() const {
1195 return UseCMSCompactAtFullCollection && !ScavengeBeforeFullGC;
1196 }
1197
1198 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1199
1200 // Support for compaction
1201 CompactibleSpace* first_compaction_space() const;
1202 // Adjust quantities in the generation affected by
1203 // the compaction.
1204 void reset_after_compaction();
1205
1206 // Allocation support
1207 HeapWord* allocate(size_t size, bool tlab);
1208 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1209 oop promote(oop obj, size_t obj_size);
1210 HeapWord* par_allocate(size_t size, bool tlab) {
1211 return allocate(size, tlab);
1212 }
1213
1214 // Incremental mode triggering.
1215 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1216 size_t word_size);
1217
1218 // Used by CMSStats to track direct allocation. The value is sampled and
1219 // reset after each young gen collection.
1220 size_t direct_allocated_words() const { return _direct_allocated_words; }
1221 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1222
1223 // Overrides for parallel promotion.
1224 virtual oop par_promote(int thread_num,
1225 oop obj, markOop m, size_t word_sz);
1226 // This one should not be called for CMS.
1227 virtual void par_promote_alloc_undo(int thread_num,
1228 HeapWord* obj, size_t word_sz);
1229 virtual void par_promote_alloc_done(int thread_num);
1230 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1231
1232 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1233
1234 // Inform this (non-young) generation that a promotion failure was
1235 // encountered during a collection of a younger generation that
1236 // promotes into this generation.
1237 virtual void promotion_failure_occurred();
1238
1239 bool should_collect(bool full, size_t size, bool tlab);
1240 virtual bool should_concurrent_collect() const;
1241 virtual bool is_too_full() const;
1242 void collect(bool full,
1243 bool clear_all_soft_refs,
1244 size_t size,
1245 bool tlab);
1246
1247 HeapWord* expand_and_allocate(size_t word_size,
1248 bool tlab,
1249 bool parallel = false);
1250
1251 // GC prologue and epilogue
1252 void gc_prologue(bool full);
1253 void gc_prologue_work(bool full, bool registerClosure,
1254 ModUnionClosure* modUnionClosure);
1255 void gc_epilogue(bool full);
1256 void gc_epilogue_work(bool full);
1257
1258 // Time since last GC of this generation
1259 jlong time_of_last_gc(jlong now) {
1260 return collector()->time_of_last_gc(now);
1261 }
1262 void update_time_of_last_gc(jlong now) {
1263 collector()-> update_time_of_last_gc(now);
1264 }
1265
1266 // Allocation failure
1267 void expand(size_t bytes, size_t expand_bytes,
1268 CMSExpansionCause::Cause cause);
1269 virtual bool expand(size_t bytes, size_t expand_bytes);
1270 void shrink(size_t bytes);
1271 void shrink_by(size_t bytes);
1272 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1273 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1274
1275 // Iteration support and related enquiries
1276 void save_marks();
1277 bool no_allocs_since_save_marks();
1278 void younger_refs_iterate(OopsInGenClosure* cl);
1279
1280 // Iteration support specific to CMS generations
1281 void save_sweep_limit();
1282
1283 // More iteration support
1284 virtual void oop_iterate(ExtendedOopClosure* cl);
1285 virtual void safe_object_iterate(ObjectClosure* cl);
1286 virtual void object_iterate(ObjectClosure* cl);
1287
1288 // Need to declare the full complement of closures, whether we'll
1289 // override them or not, or get message from the compiler:
1290 // oop_since_save_marks_iterate_nv hides virtual function...
1291 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1292 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1293 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1294
1295 // Smart allocation XXX -- move to CFLSpace?
1296 void setNearLargestChunk();
1297 bool isNearLargestChunk(HeapWord* addr);
1298
1299 // Get the chunk at the end of the space. Delegates to
1300 // the space.
1301 FreeChunk* find_chunk_at_end();
1302
1303 void post_compact();
1304
1305 // Debugging
1306 void prepare_for_verify();
1307 void verify();
1308 void print_statistics() PRODUCT_RETURN;
1309
1310 // Performance Counters support
1311 virtual void update_counters();
1312 virtual void update_counters(size_t used);
1313 void initialize_performance_counters();
1314 CollectorCounters* counters() { return collector()->counters(); }
1315
1316 // Support for parallel remark of survivor space
1317 void* get_data_recorder(int thr_num) {
1318 //Delegate to collector
1319 return collector()->get_data_recorder(thr_num);
1320 }
1321 void sample_eden_chunk() {
1322 //Delegate to collector
1323 return collector()->sample_eden_chunk();
1324 }
1325
1326 // Printing
1327 const char* name() const;
1328 virtual const char* short_name() const { return "CMS"; }
1329 void print() const;
1330 void printOccupancy(const char* s);
1331 bool must_be_youngest() const { return false; }
1332 bool must_be_oldest() const { return true; }
1333
1334 // Resize the generation after a compacting GC. The
1335 // generation can be treated as a contiguous space
1336 // after the compaction.
1337 virtual void compute_new_size();
1338 // Resize the generation after a non-compacting
1339 // collection.
1340 void compute_new_size_free_list();
1341
1342 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1343 void rotate_debug_collection_type();
1344 };
1345
1346 //
1347 // Closures of various sorts used by CMS to accomplish its work
1348 //
1349
1350 // This closure is used to do concurrent marking from the roots
1351 // following the first checkpoint.
1352 class MarkFromRootsClosure: public BitMapClosure {
1353 CMSCollector* _collector;
1354 MemRegion _span;
1355 CMSBitMap* _bitMap;
1356 CMSBitMap* _mut;
1357 CMSMarkStack* _markStack;
1358 bool _yield;
1359 int _skipBits;
1360 HeapWord* _finger;
1361 HeapWord* _threshold;
1362 DEBUG_ONLY(bool _verifying;)
1363
1364 public:
1365 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1366 CMSBitMap* bitMap,
1367 CMSMarkStack* markStack,
1368 bool should_yield, bool verifying = false);
1369 bool do_bit(size_t offset);
1370 void reset(HeapWord* addr);
1371 inline void do_yield_check();
1372
1373 private:
1374 void scanOopsInOop(HeapWord* ptr);
1375 void do_yield_work();
1376 };
1377
1378 // This closure is used to do concurrent multi-threaded
1379 // marking from the roots following the first checkpoint.
1380 // XXX This should really be a subclass of The serial version
1381 // above, but i have not had the time to refactor things cleanly.
1382 class Par_MarkFromRootsClosure: public BitMapClosure {
1383 CMSCollector* _collector;
1384 MemRegion _whole_span;
1385 MemRegion _span;
1386 CMSBitMap* _bit_map;
1387 CMSBitMap* _mut;
1388 OopTaskQueue* _work_queue;
1389 CMSMarkStack* _overflow_stack;
1390 bool _yield;
1391 int _skip_bits;
1392 HeapWord* _finger;
1393 HeapWord* _threshold;
1394 CMSConcMarkingTask* _task;
1395 public:
1396 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1397 MemRegion span,
1398 CMSBitMap* bit_map,
1399 OopTaskQueue* work_queue,
1400 CMSMarkStack* overflow_stack,
1401 bool should_yield);
1402 bool do_bit(size_t offset);
1403 inline void do_yield_check();
1404
1405 private:
1406 void scan_oops_in_oop(HeapWord* ptr);
1407 void do_yield_work();
1408 bool get_work_from_overflow_stack();
1409 };
1410
1411 // The following closures are used to do certain kinds of verification of
1412 // CMS marking.
1413 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1414 CMSCollector* _collector;
1415 MemRegion _span;
1416 CMSBitMap* _verification_bm;
1417 CMSBitMap* _cms_bm;
1418 CMSMarkStack* _mark_stack;
1419 protected:
1420 void do_oop(oop p);
1421 template <class T> inline void do_oop_work(T *p) {
1422 oop obj = oopDesc::load_decode_heap_oop(p);
1423 do_oop(obj);
1424 }
1425 public:
1426 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1427 MemRegion span,
1428 CMSBitMap* verification_bm,
1429 CMSBitMap* cms_bm,
1430 CMSMarkStack* mark_stack);
1431 void do_oop(oop* p);
1432 void do_oop(narrowOop* p);
1433
1434 // Deal with a stack overflow condition
1435 void handle_stack_overflow(HeapWord* lost);
1436 };
1437
1438 class MarkFromRootsVerifyClosure: public BitMapClosure {
1439 CMSCollector* _collector;
1440 MemRegion _span;
1441 CMSBitMap* _verification_bm;
1442 CMSBitMap* _cms_bm;
1443 CMSMarkStack* _mark_stack;
1444 HeapWord* _finger;
1445 PushAndMarkVerifyClosure _pam_verify_closure;
1446 public:
1447 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1448 CMSBitMap* verification_bm,
1449 CMSBitMap* cms_bm,
1450 CMSMarkStack* mark_stack);
1451 bool do_bit(size_t offset);
1452 void reset(HeapWord* addr);
1453 };
1454
1455
1456 // This closure is used to check that a certain set of bits is
1457 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1458 class FalseBitMapClosure: public BitMapClosure {
1459 public:
1460 bool do_bit(size_t offset) {
1461 guarantee(false, "Should not have a 1 bit");
1462 return true;
1463 }
1464 };
1465
1466 // A version of ObjectClosure with "memory" (see _previous_address below)
1467 class UpwardsObjectClosure: public BoolObjectClosure {
1468 HeapWord* _previous_address;
1469 public:
1470 UpwardsObjectClosure() : _previous_address(NULL) { }
1471 void set_previous(HeapWord* addr) { _previous_address = addr; }
1472 HeapWord* previous() { return _previous_address; }
1473 // A return value of "true" can be used by the caller to decide
1474 // if this object's end should *NOT* be recorded in
1475 // _previous_address above.
1476 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1477 };
1478
1479 // This closure is used during the second checkpointing phase
1480 // to rescan the marked objects on the dirty cards in the mod
1481 // union table and the card table proper. It's invoked via
1482 // MarkFromDirtyCardsClosure below. It uses either
1483 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1484 // declared in genOopClosures.hpp to accomplish some of its work.
1485 // In the parallel case the bitMap is shared, so access to
1486 // it needs to be suitably synchronized for updates by embedded
1487 // closures that update it; however, this closure itself only
1488 // reads the bit_map and because it is idempotent, is immune to
1489 // reading stale values.
1490 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1491 #ifdef ASSERT
1492 CMSCollector* _collector;
1493 MemRegion _span;
1494 union {
1495 CMSMarkStack* _mark_stack;
1496 OopTaskQueue* _work_queue;
1497 };
1498 #endif // ASSERT
1499 bool _parallel;
1500 CMSBitMap* _bit_map;
1501 union {
1502 MarkRefsIntoAndScanClosure* _scan_closure;
1503 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1504 };
1505
1506 public:
1507 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1508 MemRegion span,
1509 ReferenceProcessor* rp,
1510 CMSBitMap* bit_map,
1511 CMSMarkStack* mark_stack,
1512 MarkRefsIntoAndScanClosure* cl):
1513 #ifdef ASSERT
1514 _collector(collector),
1515 _span(span),
1516 _mark_stack(mark_stack),
1517 #endif // ASSERT
1518 _parallel(false),
1519 _bit_map(bit_map),
1520 _scan_closure(cl) { }
1521
1522 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1523 MemRegion span,
1524 ReferenceProcessor* rp,
1525 CMSBitMap* bit_map,
1526 OopTaskQueue* work_queue,
1527 Par_MarkRefsIntoAndScanClosure* cl):
1528 #ifdef ASSERT
1529 _collector(collector),
1530 _span(span),
1531 _work_queue(work_queue),
1532 #endif // ASSERT
1533 _parallel(true),
1534 _bit_map(bit_map),
1535 _par_scan_closure(cl) { }
1536
1537 bool do_object_b(oop obj) {
1538 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1539 return false;
1540 }
1541 bool do_object_bm(oop p, MemRegion mr);
1542 };
1543
1544 // This closure is used during the second checkpointing phase
1545 // to rescan the marked objects on the dirty cards in the mod
1546 // union table and the card table proper. It invokes
1547 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1548 // In the parallel case, the bit map is shared and requires
1549 // synchronized access.
1550 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1551 CompactibleFreeListSpace* _space;
1552 ScanMarkedObjectsAgainClosure _scan_cl;
1553 size_t _num_dirty_cards;
1554
1555 public:
1556 MarkFromDirtyCardsClosure(CMSCollector* collector,
1557 MemRegion span,
1558 CompactibleFreeListSpace* space,
1559 CMSBitMap* bit_map,
1560 CMSMarkStack* mark_stack,
1561 MarkRefsIntoAndScanClosure* cl):
1562 _space(space),
1563 _num_dirty_cards(0),
1564 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1565 mark_stack, cl) { }
1566
1567 MarkFromDirtyCardsClosure(CMSCollector* collector,
1568 MemRegion span,
1569 CompactibleFreeListSpace* space,
1570 CMSBitMap* bit_map,
1571 OopTaskQueue* work_queue,
1572 Par_MarkRefsIntoAndScanClosure* cl):
1573 _space(space),
1574 _num_dirty_cards(0),
1575 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1576 work_queue, cl) { }
1577
1578 void do_MemRegion(MemRegion mr);
1579 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1580 size_t num_dirty_cards() { return _num_dirty_cards; }
1581 };
1582
1583 // This closure is used in the non-product build to check
1584 // that there are no MemRegions with a certain property.
1585 class FalseMemRegionClosure: public MemRegionClosure {
1586 void do_MemRegion(MemRegion mr) {
1587 guarantee(!mr.is_empty(), "Shouldn't be empty");
1588 guarantee(false, "Should never be here");
1589 }
1590 };
1591
1592 // This closure is used during the precleaning phase
1593 // to "carefully" rescan marked objects on dirty cards.
1594 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1595 // to accomplish some of its work.
1596 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1597 CMSCollector* _collector;
1598 MemRegion _span;
1599 bool _yield;
1600 Mutex* _freelistLock;
1601 CMSBitMap* _bitMap;
1602 CMSMarkStack* _markStack;
1603 MarkRefsIntoAndScanClosure* _scanningClosure;
1604
1605 public:
1606 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1607 MemRegion span,
1608 CMSBitMap* bitMap,
1609 CMSMarkStack* markStack,
1610 MarkRefsIntoAndScanClosure* cl,
1611 bool should_yield):
1612 _collector(collector),
1613 _span(span),
1614 _yield(should_yield),
1615 _bitMap(bitMap),
1616 _markStack(markStack),
1617 _scanningClosure(cl) {
1618 }
1619
1620 void do_object(oop p) {
1621 guarantee(false, "call do_object_careful instead");
1622 }
1623
1624 size_t do_object_careful(oop p) {
1625 guarantee(false, "Unexpected caller");
1626 return 0;
1627 }
1628
1629 size_t do_object_careful_m(oop p, MemRegion mr);
1630
1631 void setFreelistLock(Mutex* m) {
1632 _freelistLock = m;
1633 _scanningClosure->set_freelistLock(m);
1634 }
1635
1636 private:
1637 inline bool do_yield_check();
1638
1639 void do_yield_work();
1640 };
1641
1642 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1643 CMSCollector* _collector;
1644 MemRegion _span;
1645 bool _yield;
1646 CMSBitMap* _bit_map;
1647 CMSMarkStack* _mark_stack;
1648 PushAndMarkClosure* _scanning_closure;
1649 unsigned int _before_count;
1650
1651 public:
1652 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1653 MemRegion span,
1654 CMSBitMap* bit_map,
1655 CMSMarkStack* mark_stack,
1656 PushAndMarkClosure* cl,
1657 unsigned int before_count,
1658 bool should_yield):
1659 _collector(collector),
1660 _span(span),
1661 _yield(should_yield),
1662 _bit_map(bit_map),
1663 _mark_stack(mark_stack),
1664 _scanning_closure(cl),
1665 _before_count(before_count)
1666 { }
1667
1668 void do_object(oop p) {
1669 guarantee(false, "call do_object_careful instead");
1670 }
1671
1672 size_t do_object_careful(oop p);
1673
1674 size_t do_object_careful_m(oop p, MemRegion mr) {
1675 guarantee(false, "Unexpected caller");
1676 return 0;
1677 }
1678
1679 private:
1680 inline void do_yield_check();
1681 void do_yield_work();
1682 };
1683
1684 // This closure is used to accomplish the sweeping work
1685 // after the second checkpoint but before the concurrent reset
1686 // phase.
1687 //
1688 // Terminology
1689 // left hand chunk (LHC) - block of one or more chunks currently being
1690 // coalesced. The LHC is available for coalescing with a new chunk.
1691 // right hand chunk (RHC) - block that is currently being swept that is
1692 // free or garbage that can be coalesced with the LHC.
1693 // _inFreeRange is true if there is currently a LHC
1694 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1695 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1696 // _freeFinger is the address of the current LHC
1697 class SweepClosure: public BlkClosureCareful {
1698 CMSCollector* _collector; // collector doing the work
1699 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1700 CompactibleFreeListSpace* _sp; // Space being swept
1701 HeapWord* _limit;// the address at or above which the sweep should stop
1702 // because we do not expect newly garbage blocks
1703 // eligible for sweeping past that address.
1704 Mutex* _freelistLock; // Free list lock (in space)
1705 CMSBitMap* _bitMap; // Marking bit map (in
1706 // generation)
1707 bool _inFreeRange; // Indicates if we are in the
1708 // midst of a free run
1709 bool _freeRangeInFreeLists;
1710 // Often, we have just found
1711 // a free chunk and started
1712 // a new free range; we do not
1713 // eagerly remove this chunk from
1714 // the free lists unless there is
1715 // a possibility of coalescing.
1716 // When true, this flag indicates
1717 // that the _freeFinger below
1718 // points to a potentially free chunk
1719 // that may still be in the free lists
1720 bool _lastFreeRangeCoalesced;
1721 // free range contains chunks
1722 // coalesced
1723 bool _yield;
1724 // Whether sweeping should be
1725 // done with yields. For instance
1726 // when done by the foreground
1727 // collector we shouldn't yield.
1728 HeapWord* _freeFinger; // When _inFreeRange is set, the
1729 // pointer to the "left hand
1730 // chunk"
1731 size_t _freeRangeSize;
1732 // When _inFreeRange is set, this
1733 // indicates the accumulated size
1734 // of the "left hand chunk"
1735 NOT_PRODUCT(
1736 size_t _numObjectsFreed;
1737 size_t _numWordsFreed;
1738 size_t _numObjectsLive;
1739 size_t _numWordsLive;
1740 size_t _numObjectsAlreadyFree;
1741 size_t _numWordsAlreadyFree;
1742 FreeChunk* _last_fc;
1743 )
1744 private:
1745 // Code that is common to a free chunk or garbage when
1746 // encountered during sweeping.
1747 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1748 // Process a free chunk during sweeping.
1749 void do_already_free_chunk(FreeChunk *fc);
1750 // Work method called when processing an already free or a
1751 // freshly garbage chunk to do a lookahead and possibly a
1752 // preemptive flush if crossing over _limit.
1753 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1754 // Process a garbage chunk during sweeping.
1755 size_t do_garbage_chunk(FreeChunk *fc);
1756 // Process a live chunk during sweeping.
1757 size_t do_live_chunk(FreeChunk* fc);
1758
1759 // Accessors.
1760 HeapWord* freeFinger() const { return _freeFinger; }
1761 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1762 bool inFreeRange() const { return _inFreeRange; }
1763 void set_inFreeRange(bool v) { _inFreeRange = v; }
1764 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1765 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1766 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1767 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1768
1769 // Initialize a free range.
1770 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1771 // Return this chunk to the free lists.
1772 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1773
1774 // Check if we should yield and do so when necessary.
1775 inline void do_yield_check(HeapWord* addr);
1776
1777 // Yield
1778 void do_yield_work(HeapWord* addr);
1779
1780 // Debugging/Printing
1781 void print_free_block_coalesced(FreeChunk* fc) const;
1782
1783 public:
1784 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1785 CMSBitMap* bitMap, bool should_yield);
1786 ~SweepClosure() PRODUCT_RETURN;
1787
1788 size_t do_blk_careful(HeapWord* addr);
1789 void print() const { print_on(tty); }
1790 void print_on(outputStream *st) const;
1791 };
1792
1793 // Closures related to weak references processing
1794
1795 // During CMS' weak reference processing, this is a
1796 // work-routine/closure used to complete transitive
1797 // marking of objects as live after a certain point
1798 // in which an initial set has been completely accumulated.
1799 // This closure is currently used both during the final
1800 // remark stop-world phase, as well as during the concurrent
1801 // precleaning of the discovered reference lists.
1802 class CMSDrainMarkingStackClosure: public VoidClosure {
1803 CMSCollector* _collector;
1804 MemRegion _span;
1805 CMSMarkStack* _mark_stack;
1806 CMSBitMap* _bit_map;
1807 CMSKeepAliveClosure* _keep_alive;
1808 bool _concurrent_precleaning;
1809 public:
1810 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1811 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1812 CMSKeepAliveClosure* keep_alive,
1813 bool cpc):
1814 _collector(collector),
1815 _span(span),
1816 _bit_map(bit_map),
1817 _mark_stack(mark_stack),
1818 _keep_alive(keep_alive),
1819 _concurrent_precleaning(cpc) {
1820 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1821 "Mismatch");
1822 }
1823
1824 void do_void();
1825 };
1826
1827 // A parallel version of CMSDrainMarkingStackClosure above.
1828 class CMSParDrainMarkingStackClosure: public VoidClosure {
1829 CMSCollector* _collector;
1830 MemRegion _span;
1831 OopTaskQueue* _work_queue;
1832 CMSBitMap* _bit_map;
1833 CMSInnerParMarkAndPushClosure _mark_and_push;
1834
1835 public:
1836 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1837 MemRegion span, CMSBitMap* bit_map,
1838 OopTaskQueue* work_queue):
1839 _collector(collector),
1840 _span(span),
1841 _bit_map(bit_map),
1842 _work_queue(work_queue),
1843 _mark_and_push(collector, span, bit_map, work_queue) { }
1844
1845 public:
1846 void trim_queue(uint max);
1847 void do_void();
1848 };
1849
1850 // Allow yielding or short-circuiting of reference list
1851 // precleaning work.
1852 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1853 CMSCollector* _collector;
1854 void do_yield_work();
1855 public:
1856 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1857 _collector(collector) {}
1858 virtual bool should_return();
1859 };
1860
1861
1862 // Convenience class that locks free list locks for given CMS collector
1863 class FreelistLocker: public StackObj {
1864 private:
1865 CMSCollector* _collector;
1866 public:
1867 FreelistLocker(CMSCollector* collector):
1868 _collector(collector) {
1869 _collector->getFreelistLocks();
1870 }
1871
1872 ~FreelistLocker() {
1873 _collector->releaseFreelistLocks();
1874 }
1875 };
1876
1877 // Mark all dead objects in a given space.
1878 class MarkDeadObjectsClosure: public BlkClosure {
1879 const CMSCollector* _collector;
1880 const CompactibleFreeListSpace* _sp;
1881 CMSBitMap* _live_bit_map;
1882 CMSBitMap* _dead_bit_map;
1883 public:
1884 MarkDeadObjectsClosure(const CMSCollector* collector,
1885 const CompactibleFreeListSpace* sp,
1886 CMSBitMap *live_bit_map,
1887 CMSBitMap *dead_bit_map) :
1888 _collector(collector),
1889 _sp(sp),
1890 _live_bit_map(live_bit_map),
1891 _dead_bit_map(dead_bit_map) {}
1892 size_t do_blk(HeapWord* addr);
1893 };
1894
1895 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1896
1897 public:
1898 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1899 };
1900
1901
1902 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP