1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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/gSpaceCounters.hpp"
29 #include "gc_implementation/shared/gcStats.hpp"
30 #include "gc_implementation/shared/generationCounters.hpp"
31 #include "memory/freeBlockDictionary.hpp"
32 #include "memory/generation.hpp"
33 #include "runtime/mutexLocker.hpp"
34 #include "runtime/virtualspace.hpp"
35 #include "services/memoryService.hpp"
36 #include "utilities/bitMap.inline.hpp"
37 #include "utilities/stack.inline.hpp"
38 #include "utilities/taskqueue.hpp"
39 #include "utilities/yieldingWorkgroup.hpp"
40
41 // ConcurrentMarkSweepGeneration is in support of a concurrent
42 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
43 // style. We assume, for now, that this generation is always the
44 // seniormost generation and for simplicity
45 // in the first implementation, that this generation is a single compactible
46 // space. Neither of these restrictions appears essential, and will be
47 // relaxed in the future when more time is available to implement the
48 // greater generality (and there's a need for it).
49 //
50 // Concurrent mode failures are currently handled by
51 // means of a sliding mark-compact.
52
53 class CMSAdaptiveSizePolicy;
54 class CMSConcMarkingTask;
55 class CMSGCAdaptivePolicyCounters;
56 class ConcurrentMarkSweepGeneration;
57 class ConcurrentMarkSweepPolicy;
58 class ConcurrentMarkSweepThread;
59 class CompactibleFreeListSpace;
60 class FreeChunk;
61 class PromotionInfo;
62 class ScanMarkedObjectsAgainCarefullyClosure;
63 class TenuredGeneration;
64
65 // A generic CMS bit map. It's the basis for both the CMS marking bit map
66 // as well as for the mod union table (in each case only a subset of the
67 // methods are used). This is essentially a wrapper around the BitMap class,
68 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
69 // we have _shifter == 0. and for the mod union table we have
70 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
71 // XXX 64-bit issues in BitMap?
72 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
73 friend class VMStructs;
74
75 HeapWord* _bmStartWord; // base address of range covered by map
76 size_t _bmWordSize; // map size (in #HeapWords covered)
77 const int _shifter; // shifts to convert HeapWord to bit position
78 VirtualSpace _virtual_space; // underlying the bit map
79 BitMap _bm; // the bit map itself
80 public:
81 Mutex* const _lock; // mutex protecting _bm;
82
83 public:
84 // constructor
85 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
86
87 // allocates the actual storage for the map
88 bool allocate(MemRegion mr);
89 // field getter
90 Mutex* lock() const { return _lock; }
91 // locking verifier convenience function
92 void assert_locked() const PRODUCT_RETURN;
93
94 // inquiries
95 HeapWord* startWord() const { return _bmStartWord; }
96 size_t sizeInWords() const { return _bmWordSize; }
97 size_t sizeInBits() const { return _bm.size(); }
98 // the following is one past the last word in space
99 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
100
101 // reading marks
102 bool isMarked(HeapWord* addr) const;
103 bool par_isMarked(HeapWord* addr) const; // do not lock checks
104 bool isUnmarked(HeapWord* addr) const;
105 bool isAllClear() const;
106
107 // writing marks
108 void mark(HeapWord* addr);
109 // For marking by parallel GC threads;
110 // returns true if we did, false if another thread did
111 bool par_mark(HeapWord* addr);
112
113 void mark_range(MemRegion mr);
114 void par_mark_range(MemRegion mr);
115 void mark_large_range(MemRegion mr);
116 void par_mark_large_range(MemRegion mr);
117 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
118 void clear_range(MemRegion mr);
119 void par_clear_range(MemRegion mr);
120 void clear_large_range(MemRegion mr);
121 void par_clear_large_range(MemRegion mr);
122 void clear_all();
123 void clear_all_incrementally(); // Not yet implemented!!
124
125 NOT_PRODUCT(
126 // checks the memory region for validity
127 void region_invariant(MemRegion mr);
128 )
129
130 // iteration
131 void iterate(BitMapClosure* cl) {
132 _bm.iterate(cl);
133 }
134 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
135 void dirty_range_iterate_clear(MemRegionClosure* cl);
136 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
137
138 // auxiliary support for iteration
139 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
140 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
141 HeapWord* end_addr) const;
142 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
143 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
144 HeapWord* end_addr) const;
145 MemRegion getAndClearMarkedRegion(HeapWord* addr);
146 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
147 HeapWord* end_addr);
148
149 // conversion utilities
150 HeapWord* offsetToHeapWord(size_t offset) const;
151 size_t heapWordToOffset(HeapWord* addr) const;
152 size_t heapWordDiffToOffsetDiff(size_t diff) const;
153
154 void print_on_error(outputStream* st, const char* prefix) const;
155
156 // debugging
157 // is this address range covered by the bit-map?
158 NOT_PRODUCT(
159 bool covers(MemRegion mr) const;
160 bool covers(HeapWord* start, size_t size = 0) const;
161 )
162 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
163 };
164
165 // Represents a marking stack used by the CMS collector.
166 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
167 class CMSMarkStack: public CHeapObj<mtGC> {
168 //
169 friend class CMSCollector; // to get at expasion stats further below
170 //
171
172 VirtualSpace _virtual_space; // space for the stack
173 oop* _base; // bottom of stack
174 size_t _index; // one more than last occupied index
175 size_t _capacity; // max #elements
176 Mutex _par_lock; // an advisory lock used in case of parallel access
177 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run
178
179 protected:
180 size_t _hit_limit; // we hit max stack size limit
181 size_t _failed_double; // we failed expansion before hitting limit
182
183 public:
184 CMSMarkStack():
185 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
186 _hit_limit(0),
187 _failed_double(0) {}
188
189 bool allocate(size_t size);
190
191 size_t capacity() const { return _capacity; }
192
193 oop pop() {
194 if (!isEmpty()) {
195 return _base[--_index] ;
196 }
197 return NULL;
198 }
199
200 bool push(oop ptr) {
201 if (isFull()) {
202 return false;
203 } else {
204 _base[_index++] = ptr;
205 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
206 return true;
207 }
208 }
209
210 bool isEmpty() const { return _index == 0; }
211 bool isFull() const {
212 assert(_index <= _capacity, "buffer overflow");
213 return _index == _capacity;
214 }
215
216 size_t length() { return _index; }
217
218 // "Parallel versions" of some of the above
219 oop par_pop() {
220 // lock and pop
221 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
222 return pop();
223 }
224
225 bool par_push(oop ptr) {
226 // lock and push
227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
228 return push(ptr);
229 }
230
231 // Forcibly reset the stack, losing all of its contents.
232 void reset() {
233 _index = 0;
234 }
235
236 // Expand the stack, typically in response to an overflow condition
237 void expand();
238
239 // Compute the least valued stack element.
240 oop least_value(HeapWord* low) {
241 oop least = (oop)low;
242 for (size_t i = 0; i < _index; i++) {
243 least = MIN2(least, _base[i]);
244 }
245 return least;
246 }
247
248 // Exposed here to allow stack expansion in || case
249 Mutex* par_lock() { return &_par_lock; }
250 };
251
252 class CardTableRS;
253 class CMSParGCThreadState;
254
255 class ModUnionClosure: public MemRegionClosure {
256 protected:
257 CMSBitMap* _t;
258 public:
259 ModUnionClosure(CMSBitMap* t): _t(t) { }
260 void do_MemRegion(MemRegion mr);
261 };
262
263 class ModUnionClosurePar: public ModUnionClosure {
264 public:
265 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
266 void do_MemRegion(MemRegion mr);
267 };
268
269 // Survivor Chunk Array in support of parallelization of
270 // Survivor Space rescan.
271 class ChunkArray: public CHeapObj<mtGC> {
272 size_t _index;
273 size_t _capacity;
274 size_t _overflows;
275 HeapWord** _array; // storage for array
276
277 public:
278 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
279 ChunkArray(HeapWord** a, size_t c):
280 _index(0), _capacity(c), _overflows(0), _array(a) {}
281
282 HeapWord** array() { return _array; }
283 void set_array(HeapWord** a) { _array = a; }
284
285 size_t capacity() { return _capacity; }
286 void set_capacity(size_t c) { _capacity = c; }
287
288 size_t end() {
289 assert(_index <= capacity(),
290 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
291 _index, _capacity));
292 return _index;
293 } // exclusive
294
295 HeapWord* nth(size_t n) {
296 assert(n < end(), "Out of bounds access");
297 return _array[n];
298 }
299
300 void reset() {
301 _index = 0;
302 if (_overflows > 0 && PrintCMSStatistics > 1) {
303 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
304 _capacity, _overflows);
305 }
306 _overflows = 0;
307 }
308
309 void record_sample(HeapWord* p, size_t sz) {
310 // For now we do not do anything with the size
311 if (_index < _capacity) {
312 _array[_index++] = p;
313 } else {
314 ++_overflows;
315 assert(_index == _capacity,
316 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
317 "): out of bounds at overflow#" SIZE_FORMAT,
318 _index, _capacity, _overflows));
319 }
320 }
321 };
322
323 //
324 // Timing, allocation and promotion statistics for gc scheduling and incremental
325 // mode pacing. Most statistics are exponential averages.
326 //
327 class CMSStats VALUE_OBJ_CLASS_SPEC {
328 private:
329 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
330
331 // The following are exponential averages with factor alpha:
332 // avg = (100 - alpha) * avg + alpha * cur_sample
333 //
334 // The durations measure: end_time[n] - start_time[n]
335 // The periods measure: start_time[n] - start_time[n-1]
336 //
337 // The cms period and duration include only concurrent collections; time spent
338 // in foreground cms collections due to System.gc() or because of a failure to
339 // keep up are not included.
340 //
341 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
342 // real value, but is used only after the first period. A value of 100 is
343 // used for the first sample so it gets the entire weight.
344 unsigned int _saved_alpha; // 0-100
345 unsigned int _gc0_alpha;
346 unsigned int _cms_alpha;
347
348 double _gc0_duration;
349 double _gc0_period;
350 size_t _gc0_promoted; // bytes promoted per gc0
351 double _cms_duration;
352 double _cms_duration_pre_sweep; // time from initiation to start of sweep
353 double _cms_duration_per_mb;
354 double _cms_period;
355 size_t _cms_allocated; // bytes of direct allocation per gc0 period
356
357 // Timers.
358 elapsedTimer _cms_timer;
359 TimeStamp _gc0_begin_time;
360 TimeStamp _cms_begin_time;
361 TimeStamp _cms_end_time;
362
363 // Snapshots of the amount used in the CMS generation.
364 size_t _cms_used_at_gc0_begin;
365 size_t _cms_used_at_gc0_end;
366 size_t _cms_used_at_cms_begin;
367
368 // Used to prevent the duty cycle from being reduced in the middle of a cms
369 // cycle.
370 bool _allow_duty_cycle_reduction;
371
372 enum {
373 _GC0_VALID = 0x1,
374 _CMS_VALID = 0x2,
375 _ALL_VALID = _GC0_VALID | _CMS_VALID
376 };
377
378 unsigned int _valid_bits;
379
380 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
381
382 protected:
383
384 // Return a duty cycle that avoids wild oscillations, by limiting the amount
385 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
386 // as a recommended value).
387 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
388 unsigned int new_duty_cycle);
389 unsigned int icms_update_duty_cycle_impl();
390
391 // In support of adjusting of cms trigger ratios based on history
392 // of concurrent mode failure.
393 double cms_free_adjustment_factor(size_t free) const;
394 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
395
396 public:
397 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
398 unsigned int alpha = CMSExpAvgFactor);
399
400 // Whether or not the statistics contain valid data; higher level statistics
401 // cannot be called until this returns true (they require at least one young
402 // gen and one cms cycle to have completed).
403 bool valid() const;
404
405 // Record statistics.
406 void record_gc0_begin();
407 void record_gc0_end(size_t cms_gen_bytes_used);
408 void record_cms_begin();
409 void record_cms_end();
410
411 // Allow management of the cms timer, which must be stopped/started around
412 // yield points.
413 elapsedTimer& cms_timer() { return _cms_timer; }
414 void start_cms_timer() { _cms_timer.start(); }
415 void stop_cms_timer() { _cms_timer.stop(); }
416
417 // Basic statistics; units are seconds or bytes.
418 double gc0_period() const { return _gc0_period; }
419 double gc0_duration() const { return _gc0_duration; }
420 size_t gc0_promoted() const { return _gc0_promoted; }
421 double cms_period() const { return _cms_period; }
422 double cms_duration() const { return _cms_duration; }
423 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
424 size_t cms_allocated() const { return _cms_allocated; }
425
426 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
427
428 // Seconds since the last background cms cycle began or ended.
429 double cms_time_since_begin() const;
430 double cms_time_since_end() const;
431
432 // Higher level statistics--caller must check that valid() returns true before
433 // calling.
434
435 // Returns bytes promoted per second of wall clock time.
436 double promotion_rate() const;
437
438 // Returns bytes directly allocated per second of wall clock time.
439 double cms_allocation_rate() const;
440
441 // Rate at which space in the cms generation is being consumed (sum of the
442 // above two).
443 double cms_consumption_rate() const;
444
445 // Returns an estimate of the number of seconds until the cms generation will
446 // fill up, assuming no collection work is done.
447 double time_until_cms_gen_full() const;
448
449 // Returns an estimate of the number of seconds remaining until
450 // the cms generation collection should start.
451 double time_until_cms_start() const;
452
453 // End of higher level statistics.
454
455 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
456 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
457
458 // Update the duty cycle and return the new value.
459 unsigned int icms_update_duty_cycle();
460
461 // Debugging.
462 void print_on(outputStream* st) const PRODUCT_RETURN;
463 void print() const { print_on(gclog_or_tty); }
464 };
465
466 // A closure related to weak references processing which
467 // we embed in the CMSCollector, since we need to pass
468 // it to the reference processor for secondary filtering
469 // of references based on reachability of referent;
470 // see role of _is_alive_non_header closure in the
471 // ReferenceProcessor class.
472 // For objects in the CMS generation, this closure checks
473 // if the object is "live" (reachable). Used in weak
474 // reference processing.
475 class CMSIsAliveClosure: public BoolObjectClosure {
476 const MemRegion _span;
477 const CMSBitMap* _bit_map;
478
479 friend class CMSCollector;
480 public:
481 CMSIsAliveClosure(MemRegion span,
482 CMSBitMap* bit_map):
483 _span(span),
484 _bit_map(bit_map) {
485 assert(!span.is_empty(), "Empty span could spell trouble");
486 }
487
488 void do_object(oop obj) {
489 assert(false, "not to be invoked");
490 }
491
492 bool do_object_b(oop obj);
493 };
494
495
496 // Implements AbstractRefProcTaskExecutor for CMS.
497 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
498 public:
499
500 CMSRefProcTaskExecutor(CMSCollector& collector)
501 : _collector(collector)
502 { }
503
504 // Executes a task using worker threads.
505 virtual void execute(ProcessTask& task);
506 virtual void execute(EnqueueTask& task);
507 private:
508 CMSCollector& _collector;
509 };
510
511
512 class CMSCollector: public CHeapObj<mtGC> {
513 friend class VMStructs;
514 friend class ConcurrentMarkSweepThread;
515 friend class ConcurrentMarkSweepGeneration;
516 friend class CompactibleFreeListSpace;
517 friend class CMSParRemarkTask;
518 friend class CMSConcMarkingTask;
519 friend class CMSRefProcTaskProxy;
520 friend class CMSRefProcTaskExecutor;
521 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
522 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
523 friend class PushOrMarkClosure; // to access _restart_addr
524 friend class Par_PushOrMarkClosure; // to access _restart_addr
525 friend class MarkFromRootsClosure; // -- ditto --
526 // ... and for clearing cards
527 friend class Par_MarkFromRootsClosure; // to access _restart_addr
528 // ... and for clearing cards
529 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
530 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
531 friend class PushAndMarkVerifyClosure; // -- ditto --
532 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
533 friend class PushAndMarkClosure; // -- ditto --
534 friend class Par_PushAndMarkClosure; // -- ditto --
535 friend class CMSKeepAliveClosure; // -- ditto --
536 friend class CMSDrainMarkingStackClosure; // -- ditto --
537 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
538 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
539 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
540 friend class VM_CMS_Operation;
541 friend class VM_CMS_Initial_Mark;
542 friend class VM_CMS_Final_Remark;
543 friend class TraceCMSMemoryManagerStats;
544
545 private:
546 jlong _time_of_last_gc;
547 void update_time_of_last_gc(jlong now) {
548 _time_of_last_gc = now;
549 }
550
551 OopTaskQueueSet* _task_queues;
552
553 // Overflow list of grey objects, threaded through mark-word
554 // Manipulated with CAS in the parallel/multi-threaded case.
555 oop _overflow_list;
556 // The following array-pair keeps track of mark words
557 // displaced for accomodating overflow list above.
558 // This code will likely be revisited under RFE#4922830.
559 Stack<oop, mtGC> _preserved_oop_stack;
560 Stack<markOop, mtGC> _preserved_mark_stack;
561
562 int* _hash_seed;
563
564 // In support of multi-threaded concurrent phases
565 YieldingFlexibleWorkGang* _conc_workers;
566
567 // Performance Counters
568 CollectorCounters* _gc_counters;
569
570 // Initialization Errors
571 bool _completed_initialization;
572
573 // In support of ExplicitGCInvokesConcurrent
574 static bool _full_gc_requested;
575 unsigned int _collection_count_start;
576
577 // Should we unload classes this concurrent cycle?
578 bool _should_unload_classes;
579 unsigned int _concurrent_cycles_since_last_unload;
580 unsigned int concurrent_cycles_since_last_unload() const {
581 return _concurrent_cycles_since_last_unload;
582 }
583 // Did we (allow) unload classes in the previous concurrent cycle?
584 bool unloaded_classes_last_cycle() const {
585 return concurrent_cycles_since_last_unload() == 0;
586 }
587 // Root scanning options for perm gen
588 int _roots_scanning_options;
589 int roots_scanning_options() const { return _roots_scanning_options; }
590 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
591 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
592
593 // Verification support
594 CMSBitMap _verification_mark_bm;
595 void verify_after_remark_work_1();
596 void verify_after_remark_work_2();
597
598 // true if any verification flag is on.
599 bool _verifying;
600 bool verifying() const { return _verifying; }
601 void set_verifying(bool v) { _verifying = v; }
602
603 // Collector policy
604 ConcurrentMarkSweepPolicy* _collector_policy;
605 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
606
607 void set_did_compact(bool v);
608
609 // XXX Move these to CMSStats ??? FIX ME !!!
610 elapsedTimer _inter_sweep_timer; // time between sweeps
611 elapsedTimer _intra_sweep_timer; // time _in_ sweeps
612 // padded decaying average estimates of the above
613 AdaptivePaddedAverage _inter_sweep_estimate;
614 AdaptivePaddedAverage _intra_sweep_estimate;
615
616 protected:
617 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
618 MemRegion _span; // span covering above two
619 CardTableRS* _ct; // card table
620
621 // CMS marking support structures
622 CMSBitMap _markBitMap;
623 CMSBitMap _modUnionTable;
624 CMSMarkStack _markStack;
625
626 HeapWord* _restart_addr; // in support of marking stack overflow
627 void lower_restart_addr(HeapWord* low);
628
629 // Counters in support of marking stack / work queue overflow handling:
630 // a non-zero value indicates certain types of overflow events during
631 // the current CMS cycle and could lead to stack resizing efforts at
632 // an opportune future time.
633 size_t _ser_pmc_preclean_ovflw;
634 size_t _ser_pmc_remark_ovflw;
635 size_t _par_pmc_remark_ovflw;
636 size_t _ser_kac_preclean_ovflw;
637 size_t _ser_kac_ovflw;
638 size_t _par_kac_ovflw;
639 NOT_PRODUCT(ssize_t _num_par_pushes;)
640
641 // ("Weak") Reference processing support
642 ReferenceProcessor* _ref_processor;
643 CMSIsAliveClosure _is_alive_closure;
644 // keep this textually after _markBitMap and _span; c'tor dependency
645
646 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
647 ModUnionClosure _modUnionClosure;
648 ModUnionClosurePar _modUnionClosurePar;
649
650 // CMS abstract state machine
651 // initial_state: Idling
652 // next_state(Idling) = {Marking}
653 // next_state(Marking) = {Precleaning, Sweeping}
654 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
655 // next_state(AbortablePreclean) = {FinalMarking}
656 // next_state(FinalMarking) = {Sweeping}
657 // next_state(Sweeping) = {Resizing}
658 // next_state(Resizing) = {Resetting}
659 // next_state(Resetting) = {Idling}
660 // The numeric values below are chosen so that:
661 // . _collectorState <= Idling == post-sweep && pre-mark
662 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
663 // precleaning || abortablePrecleanb
664 public:
665 enum CollectorState {
666 Resizing = 0,
667 Resetting = 1,
668 Idling = 2,
669 InitialMarking = 3,
670 Marking = 4,
671 Precleaning = 5,
672 AbortablePreclean = 6,
673 FinalMarking = 7,
674 Sweeping = 8
675 };
676 protected:
677 static CollectorState _collectorState;
678
679 // State related to prologue/epilogue invocation for my generations
680 bool _between_prologue_and_epilogue;
681
682 // Signalling/State related to coordination between fore- and backgroud GC
683 // Note: When the baton has been passed from background GC to foreground GC,
684 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
685 static bool _foregroundGCIsActive; // true iff foreground collector is active or
686 // wants to go active
687 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
688 // yet passed the baton to the foreground GC
689
690 // Support for CMSScheduleRemark (abortable preclean)
691 bool _abort_preclean;
692 bool _start_sampling;
693
694 int _numYields;
695 size_t _numDirtyCards;
696 size_t _sweep_count;
697 // number of full gc's since the last concurrent gc.
698 uint _full_gcs_since_conc_gc;
699
700 // occupancy used for bootstrapping stats
701 double _bootstrap_occupancy;
702
703 // timer
704 elapsedTimer _timer;
705
706 // Timing, allocation and promotion statistics, used for scheduling.
707 CMSStats _stats;
708
709 // Allocation limits installed in the young gen, used only in
710 // CMSIncrementalMode. When an allocation in the young gen would cross one of
711 // these limits, the cms generation is notified and the cms thread is started
712 // or stopped, respectively.
713 HeapWord* _icms_start_limit;
714 HeapWord* _icms_stop_limit;
715
716 enum CMS_op_type {
717 CMS_op_checkpointRootsInitial,
718 CMS_op_checkpointRootsFinal
719 };
720
721 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
722 bool stop_world_and_do(CMS_op_type op);
723
724 OopTaskQueueSet* task_queues() { return _task_queues; }
725 int* hash_seed(int i) { return &_hash_seed[i]; }
726 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
727
728 // Support for parallelizing Eden rescan in CMS remark phase
729 void sample_eden(); // ... sample Eden space top
730
731 private:
732 // Support for parallelizing young gen rescan in CMS remark phase
733 Generation* _young_gen; // the younger gen
734 HeapWord** _top_addr; // ... Top of Eden
735 HeapWord** _end_addr; // ... End of Eden
736 HeapWord** _eden_chunk_array; // ... Eden partitioning array
737 size_t _eden_chunk_index; // ... top (exclusive) of array
738 size_t _eden_chunk_capacity; // ... max entries in array
739
740 // Support for parallelizing survivor space rescan
741 HeapWord** _survivor_chunk_array;
742 size_t _survivor_chunk_index;
743 size_t _survivor_chunk_capacity;
744 size_t* _cursor;
745 ChunkArray* _survivor_plab_array;
746
747 // Support for marking stack overflow handling
748 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
749 bool par_take_from_overflow_list(size_t num,
750 OopTaskQueue* to_work_q,
751 int no_of_gc_threads);
752 void push_on_overflow_list(oop p);
753 void par_push_on_overflow_list(oop p);
754 // the following is, obviously, not, in general, "MT-stable"
755 bool overflow_list_is_empty() const;
756
757 void preserve_mark_if_necessary(oop p);
758 void par_preserve_mark_if_necessary(oop p);
759 void preserve_mark_work(oop p, markOop m);
760 void restore_preserved_marks_if_any();
761 NOT_PRODUCT(bool no_preserved_marks() const;)
762 // in support of testing overflow code
763 NOT_PRODUCT(int _overflow_counter;)
764 NOT_PRODUCT(bool simulate_overflow();) // sequential
765 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
766
767 // CMS work methods
768 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
769
770 // a return value of false indicates failure due to stack overflow
771 bool markFromRootsWork(bool asynch); // concurrent marking work
772
773 public: // FIX ME!!! only for testing
774 bool do_marking_st(bool asynch); // single-threaded marking
775 bool do_marking_mt(bool asynch); // multi-threaded marking
776
777 private:
778
779 // concurrent precleaning work
780 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
781 ScanMarkedObjectsAgainCarefullyClosure* cl);
782 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
783 ScanMarkedObjectsAgainCarefullyClosure* cl);
784 // Does precleaning work, returning a quantity indicative of
785 // the amount of "useful work" done.
786 size_t preclean_work(bool clean_refs, bool clean_survivors);
787 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
788 void abortable_preclean(); // Preclean while looking for possible abort
789 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
790 // Helper function for above; merge-sorts the per-thread plab samples
791 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
792 // Resets (i.e. clears) the per-thread plab sample vectors
793 void reset_survivor_plab_arrays();
794
795 // final (second) checkpoint work
796 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
797 bool init_mark_was_synchronous);
798 // work routine for parallel version of remark
799 void do_remark_parallel();
800 // work routine for non-parallel version of remark
801 void do_remark_non_parallel();
802 // reference processing work routine (during second checkpoint)
803 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
804
805 // concurrent sweeping work
806 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
807
808 // (concurrent) resetting of support data structures
809 void reset(bool asynch);
810
811 // Clear _expansion_cause fields of constituent generations
812 void clear_expansion_cause();
813
814 // An auxilliary method used to record the ends of
815 // used regions of each generation to limit the extent of sweep
816 void save_sweep_limits();
817
818 // A work method used by foreground collection to determine
819 // what type of collection (compacting or not, continuing or fresh)
820 // it should do.
821 void decide_foreground_collection_type(bool clear_all_soft_refs,
822 bool* should_compact, bool* should_start_over);
823
824 // A work method used by the foreground collector to do
825 // a mark-sweep-compact.
826 void do_compaction_work(bool clear_all_soft_refs);
827
828 // A work method used by the foreground collector to do
829 // a mark-sweep, after taking over from a possibly on-going
830 // concurrent mark-sweep collection.
831 void do_mark_sweep_work(bool clear_all_soft_refs,
832 CollectorState first_state, bool should_start_over);
833
834 // If the backgrould GC is active, acquire control from the background
835 // GC and do the collection.
836 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
837
838 // For synchronizing passing of control from background to foreground
839 // GC. waitForForegroundGC() is called by the background
840 // collector. It if had to wait for a foreground collection,
841 // it returns true and the background collection should assume
842 // that the collection was finished by the foreground
843 // collector.
844 bool waitForForegroundGC();
845
846 // Incremental mode triggering: recompute the icms duty cycle and set the
847 // allocation limits in the young gen.
848 void icms_update_allocation_limits();
849
850 size_t block_size_using_printezis_bits(HeapWord* addr) const;
851 size_t block_size_if_printezis_bits(HeapWord* addr) const;
852 HeapWord* next_card_start_after_block(HeapWord* addr) const;
853
854 void setup_cms_unloading_and_verification_state();
855 public:
856 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
857 CardTableRS* ct,
858 ConcurrentMarkSweepPolicy* cp);
859 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
860
861 ReferenceProcessor* ref_processor() { return _ref_processor; }
862 void ref_processor_init();
863
864 Mutex* bitMapLock() const { return _markBitMap.lock(); }
865 static CollectorState abstract_state() { return _collectorState; }
866
867 bool should_abort_preclean() const; // Whether preclean should be aborted.
868 size_t get_eden_used() const;
869 size_t get_eden_capacity() const;
870
871 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
872
873 // locking checks
874 NOT_PRODUCT(static bool have_cms_token();)
875
876 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
877 bool shouldConcurrentCollect();
878
879 void collect(bool full,
880 bool clear_all_soft_refs,
881 size_t size,
882 bool tlab);
883 void collect_in_background(bool clear_all_soft_refs);
884 void collect_in_foreground(bool clear_all_soft_refs);
885
886 // In support of ExplicitGCInvokesConcurrent
887 static void request_full_gc(unsigned int full_gc_count);
888 // Should we unload classes in a particular concurrent cycle?
889 bool should_unload_classes() const {
890 return _should_unload_classes;
891 }
892 void update_should_unload_classes();
893
894 void direct_allocated(HeapWord* start, size_t size);
895
896 // Object is dead if not marked and current phase is sweeping.
897 bool is_dead_obj(oop obj) const;
898
899 // After a promotion (of "start"), do any necessary marking.
900 // If "par", then it's being done by a parallel GC thread.
901 // The last two args indicate if we need precise marking
902 // and if so the size of the object so it can be dirtied
903 // in its entirety.
904 void promoted(bool par, HeapWord* start,
905 bool is_obj_array, size_t obj_size);
906
907 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
908 size_t word_size);
909
910 void getFreelistLocks() const;
911 void releaseFreelistLocks() const;
912 bool haveFreelistLocks() const;
913
914 // Adjust size of underlying generation
915 void compute_new_size();
916
917 // GC prologue and epilogue
918 void gc_prologue(bool full);
919 void gc_epilogue(bool full);
920
921 jlong time_of_last_gc(jlong now) {
922 if (_collectorState <= Idling) {
923 // gc not in progress
924 return _time_of_last_gc;
925 } else {
926 // collection in progress
927 return now;
928 }
929 }
930
931 // Support for parallel remark of survivor space
932 void* get_data_recorder(int thr_num);
933
934 CMSBitMap* markBitMap() { return &_markBitMap; }
935 void directAllocated(HeapWord* start, size_t size);
936
937 // main CMS steps and related support
938 void checkpointRootsInitial(bool asynch);
939 bool markFromRoots(bool asynch); // a return value of false indicates failure
940 // due to stack overflow
941 void preclean();
942 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
943 bool init_mark_was_synchronous);
944 void sweep(bool asynch);
945
946 // Check that the currently executing thread is the expected
947 // one (foreground collector or background collector).
948 static void check_correct_thread_executing() PRODUCT_RETURN;
949 // XXXPERM void print_statistics() PRODUCT_RETURN;
950
951 bool is_cms_reachable(HeapWord* addr);
952
953 // Performance Counter Support
954 CollectorCounters* counters() { return _gc_counters; }
955
956 // timer stuff
957 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
958 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
959 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
960 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
961
962 int yields() { return _numYields; }
963 void resetYields() { _numYields = 0; }
964 void incrementYields() { _numYields++; }
965 void resetNumDirtyCards() { _numDirtyCards = 0; }
966 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
967 size_t numDirtyCards() { return _numDirtyCards; }
968
969 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
970 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
971 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
972 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
973 size_t sweep_count() const { return _sweep_count; }
974 void increment_sweep_count() { _sweep_count++; }
975
976 // Timers/stats for gc scheduling and incremental mode pacing.
977 CMSStats& stats() { return _stats; }
978
979 // Convenience methods that check whether CMSIncrementalMode is enabled and
980 // forward to the corresponding methods in ConcurrentMarkSweepThread.
981 static void start_icms();
982 static void stop_icms(); // Called at the end of the cms cycle.
983 static void disable_icms(); // Called before a foreground collection.
984 static void enable_icms(); // Called after a foreground collection.
985 void icms_wait(); // Called at yield points.
986
987 // Adaptive size policy
988 CMSAdaptiveSizePolicy* size_policy();
989 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
990
991 static void print_on_error(outputStream* st);
992
993 // debugging
994 void verify();
995 bool verify_after_remark(bool silent = VerifySilently);
996 void verify_ok_to_terminate() const PRODUCT_RETURN;
997 void verify_work_stacks_empty() const PRODUCT_RETURN;
998 void verify_overflow_empty() const PRODUCT_RETURN;
999
1000 // convenience methods in support of debugging
1001 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1002 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1003
1004 // accessors
1005 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1006 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1007
1008 // Initialization errors
1009 bool completed_initialization() { return _completed_initialization; }
1010 };
1011
1012 class CMSExpansionCause : public AllStatic {
1013 public:
1014 enum Cause {
1015 _no_expansion,
1016 _satisfy_free_ratio,
1017 _satisfy_promotion,
1018 _satisfy_allocation,
1019 _allocate_par_lab,
1020 _allocate_par_spooling_space,
1021 _adaptive_size_policy
1022 };
1023 // Return a string describing the cause of the expansion.
1024 static const char* to_string(CMSExpansionCause::Cause cause);
1025 };
1026
1027 class ConcurrentMarkSweepGeneration: public CardGeneration {
1028 friend class VMStructs;
1029 friend class ConcurrentMarkSweepThread;
1030 friend class ConcurrentMarkSweep;
1031 friend class CMSCollector;
1032 protected:
1033 static CMSCollector* _collector; // the collector that collects us
1034 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1035
1036 // Performance Counters
1037 GenerationCounters* _gen_counters;
1038 GSpaceCounters* _space_counters;
1039
1040 // Words directly allocated, used by CMSStats.
1041 size_t _direct_allocated_words;
1042
1043 // Non-product stat counters
1044 NOT_PRODUCT(
1045 size_t _numObjectsPromoted;
1046 size_t _numWordsPromoted;
1047 size_t _numObjectsAllocated;
1048 size_t _numWordsAllocated;
1049 )
1050
1051 // Used for sizing decisions
1052 bool _incremental_collection_failed;
1053 bool incremental_collection_failed() {
1054 return _incremental_collection_failed;
1055 }
1056 void set_incremental_collection_failed() {
1057 _incremental_collection_failed = true;
1058 }
1059 void clear_incremental_collection_failed() {
1060 _incremental_collection_failed = false;
1061 }
1062
1063 // accessors
1064 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1065 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1066
1067 private:
1068 // For parallel young-gen GC support.
1069 CMSParGCThreadState** _par_gc_thread_states;
1070
1071 // Reason generation was expanded
1072 CMSExpansionCause::Cause _expansion_cause;
1073
1074 // In support of MinChunkSize being larger than min object size
1075 const double _dilatation_factor;
1076
1077 enum CollectionTypes {
1078 Concurrent_collection_type = 0,
1079 MS_foreground_collection_type = 1,
1080 MSC_foreground_collection_type = 2,
1081 Unknown_collection_type = 3
1082 };
1083
1084 CollectionTypes _debug_collection_type;
1085
1086 // True if a compactiing collection was done.
1087 bool _did_compact;
1088 bool did_compact() { return _did_compact; }
1089
1090 // Fraction of current occupancy at which to start a CMS collection which
1091 // will collect this generation (at least).
1092 double _initiating_occupancy;
1093
1094 protected:
1095 // Shrink generation by specified size (returns false if unable to shrink)
1096 void shrink_free_list_by(size_t bytes);
1097
1098 // Update statistics for GC
1099 virtual void update_gc_stats(int level, bool full);
1100
1101 // Maximum available space in the generation (including uncommitted)
1102 // space.
1103 size_t max_available() const;
1104
1105 // getter and initializer for _initiating_occupancy field.
1106 double initiating_occupancy() const { return _initiating_occupancy; }
1107 void init_initiating_occupancy(intx io, uintx tr);
1108
1109 public:
1110 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1111 int level, CardTableRS* ct,
1112 bool use_adaptive_freelists,
1113 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1114
1115 // Accessors
1116 CMSCollector* collector() const { return _collector; }
1117 static void set_collector(CMSCollector* collector) {
1118 assert(_collector == NULL, "already set");
1119 _collector = collector;
1120 }
1121 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1122
1123 Mutex* freelistLock() const;
1124
1125 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1126
1127 // Adaptive size policy
1128 CMSAdaptiveSizePolicy* size_policy();
1129
1130 void set_did_compact(bool v) { _did_compact = v; }
1131
1132 bool refs_discovery_is_atomic() const { return false; }
1133 bool refs_discovery_is_mt() const {
1134 // Note: CMS does MT-discovery during the parallel-remark
1135 // phases. Use ReferenceProcessorMTMutator to make refs
1136 // discovery MT-safe during such phases or other parallel
1137 // discovery phases in the future. This may all go away
1138 // if/when we decide that refs discovery is sufficiently
1139 // rare that the cost of the CAS's involved is in the
1140 // noise. That's a measurement that should be done, and
1141 // the code simplified if that turns out to be the case.
1142 return ConcGCThreads > 1;
1143 }
1144
1145 // Override
1146 virtual void ref_processor_init();
1147
1148 // Grow generation by specified size (returns false if unable to grow)
1149 bool grow_by(size_t bytes);
1150 // Grow generation to reserved size.
1151 bool grow_to_reserved();
1152
1153 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1154
1155 // Space enquiries
1156 size_t capacity() const;
1157 size_t used() const;
1158 size_t free() const;
1159 double occupancy() const { return ((double)used())/((double)capacity()); }
1160 size_t contiguous_available() const;
1161 size_t unsafe_max_alloc_nogc() const;
1162
1163 // over-rides
1164 MemRegion used_region() const;
1165 MemRegion used_region_at_save_marks() const;
1166
1167 // Does a "full" (forced) collection invoked on this generation collect
1168 // all younger generations as well? Note that the second conjunct is a
1169 // hack to allow the collection of the younger gen first if the flag is
1170 // set. This is better than using th policy's should_collect_gen0_first()
1171 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1172 virtual bool full_collects_younger_generations() const {
1173 return UseCMSCompactAtFullCollection && !CollectGen0First;
1174 }
1175
1176 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1177
1178 // Support for compaction
1179 CompactibleSpace* first_compaction_space() const;
1180 // Adjust quantites in the generation affected by
1181 // the compaction.
1182 void reset_after_compaction();
1183
1184 // Allocation support
1185 HeapWord* allocate(size_t size, bool tlab);
1186 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1187 oop promote(oop obj, size_t obj_size);
1188 HeapWord* par_allocate(size_t size, bool tlab) {
1189 return allocate(size, tlab);
1190 }
1191
1192 // Incremental mode triggering.
1193 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1194 size_t word_size);
1195
1196 // Used by CMSStats to track direct allocation. The value is sampled and
1197 // reset after each young gen collection.
1198 size_t direct_allocated_words() const { return _direct_allocated_words; }
1199 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1200
1201 // Overrides for parallel promotion.
1202 virtual oop par_promote(int thread_num,
1203 oop obj, markOop m, size_t word_sz);
1204 // This one should not be called for CMS.
1205 virtual void par_promote_alloc_undo(int thread_num,
1206 HeapWord* obj, size_t word_sz);
1207 virtual void par_promote_alloc_done(int thread_num);
1208 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1209
1210 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1211
1212 // Inform this (non-young) generation that a promotion failure was
1213 // encountered during a collection of a younger generation that
1214 // promotes into this generation.
1215 virtual void promotion_failure_occurred();
1216
1217 bool should_collect(bool full, size_t size, bool tlab);
1218 virtual bool should_concurrent_collect() const;
1219 virtual bool is_too_full() const;
1220 void collect(bool full,
1221 bool clear_all_soft_refs,
1222 size_t size,
1223 bool tlab);
1224
1225 HeapWord* expand_and_allocate(size_t word_size,
1226 bool tlab,
1227 bool parallel = false);
1228
1229 // GC prologue and epilogue
1230 void gc_prologue(bool full);
1231 void gc_prologue_work(bool full, bool registerClosure,
1232 ModUnionClosure* modUnionClosure);
1233 void gc_epilogue(bool full);
1234 void gc_epilogue_work(bool full);
1235
1236 // Time since last GC of this generation
1237 jlong time_of_last_gc(jlong now) {
1238 return collector()->time_of_last_gc(now);
1239 }
1240 void update_time_of_last_gc(jlong now) {
1241 collector()-> update_time_of_last_gc(now);
1242 }
1243
1244 // Allocation failure
1245 void expand(size_t bytes, size_t expand_bytes,
1246 CMSExpansionCause::Cause cause);
1247 virtual bool expand(size_t bytes, size_t expand_bytes);
1248 void shrink(size_t bytes);
1249 void shrink_by(size_t bytes);
1250 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1251 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1252
1253 // Iteration support and related enquiries
1254 void save_marks();
1255 bool no_allocs_since_save_marks();
1256 void object_iterate_since_last_GC(ObjectClosure* cl);
1257 void younger_refs_iterate(OopsInGenClosure* cl);
1258
1259 // Iteration support specific to CMS generations
1260 void save_sweep_limit();
1261
1262 // More iteration support
1263 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1264 virtual void oop_iterate(ExtendedOopClosure* cl);
1265 virtual void safe_object_iterate(ObjectClosure* cl);
1266 virtual void object_iterate(ObjectClosure* cl);
1267
1268 // Need to declare the full complement of closures, whether we'll
1269 // override them or not, or get message from the compiler:
1270 // oop_since_save_marks_iterate_nv hides virtual function...
1271 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1272 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1273 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1274
1275 // Smart allocation XXX -- move to CFLSpace?
1276 void setNearLargestChunk();
1277 bool isNearLargestChunk(HeapWord* addr);
1278
1279 // Get the chunk at the end of the space. Delagates to
1280 // the space.
1281 FreeChunk* find_chunk_at_end();
1282
1283 void post_compact();
1284
1285 // Debugging
1286 void prepare_for_verify();
1287 void verify();
1288 void print_statistics() PRODUCT_RETURN;
1289
1290 // Performance Counters support
1291 virtual void update_counters();
1292 virtual void update_counters(size_t used);
1293 void initialize_performance_counters();
1294 CollectorCounters* counters() { return collector()->counters(); }
1295
1296 // Support for parallel remark of survivor space
1297 void* get_data_recorder(int thr_num) {
1298 //Delegate to collector
1299 return collector()->get_data_recorder(thr_num);
1300 }
1301
1302 // Printing
1303 const char* name() const;
1304 virtual const char* short_name() const { return "CMS"; }
1305 void print() const;
1306 void printOccupancy(const char* s);
1307 bool must_be_youngest() const { return false; }
1308 bool must_be_oldest() const { return true; }
1309
1310 // Resize the generation after a compacting GC. The
1311 // generation can be treated as a contiguous space
1312 // after the compaction.
1313 virtual void compute_new_size();
1314 // Resize the generation after a non-compacting
1315 // collection.
1316 void compute_new_size_free_list();
1317
1318 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1319 void rotate_debug_collection_type();
1320 };
1321
1322 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1323
1324 // Return the size policy from the heap's collector
1325 // policy casted to CMSAdaptiveSizePolicy*.
1326 CMSAdaptiveSizePolicy* cms_size_policy() const;
1327
1328 // Resize the generation based on the adaptive size
1329 // policy.
1330 void resize(size_t cur_promo, size_t desired_promo);
1331
1332 // Return the GC counters from the collector policy
1333 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1334
1335 virtual void shrink_by(size_t bytes);
1336
1337 public:
1338 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1339 int level, CardTableRS* ct,
1340 bool use_adaptive_freelists,
1341 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1342 dictionaryChoice) :
1343 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1344 use_adaptive_freelists, dictionaryChoice) {}
1345
1346 virtual const char* short_name() const { return "ASCMS"; }
1347 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1348
1349 virtual void update_counters();
1350 virtual void update_counters(size_t used);
1351 };
1352
1353 //
1354 // Closures of various sorts used by CMS to accomplish its work
1355 //
1356
1357 // This closure is used to check that a certain set of oops is empty.
1358 class FalseClosure: public OopClosure {
1359 public:
1360 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1361 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1362 };
1363
1364 // This closure is used to do concurrent marking from the roots
1365 // following the first checkpoint.
1366 class MarkFromRootsClosure: public BitMapClosure {
1367 CMSCollector* _collector;
1368 MemRegion _span;
1369 CMSBitMap* _bitMap;
1370 CMSBitMap* _mut;
1371 CMSMarkStack* _markStack;
1372 bool _yield;
1373 int _skipBits;
1374 HeapWord* _finger;
1375 HeapWord* _threshold;
1376 DEBUG_ONLY(bool _verifying;)
1377
1378 public:
1379 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1380 CMSBitMap* bitMap,
1381 CMSMarkStack* markStack,
1382 bool should_yield, bool verifying = false);
1383 bool do_bit(size_t offset);
1384 void reset(HeapWord* addr);
1385 inline void do_yield_check();
1386
1387 private:
1388 void scanOopsInOop(HeapWord* ptr);
1389 void do_yield_work();
1390 };
1391
1392 // This closure is used to do concurrent multi-threaded
1393 // marking from the roots following the first checkpoint.
1394 // XXX This should really be a subclass of The serial version
1395 // above, but i have not had the time to refactor things cleanly.
1396 // That willbe done for Dolphin.
1397 class Par_MarkFromRootsClosure: public BitMapClosure {
1398 CMSCollector* _collector;
1399 MemRegion _whole_span;
1400 MemRegion _span;
1401 CMSBitMap* _bit_map;
1402 CMSBitMap* _mut;
1403 OopTaskQueue* _work_queue;
1404 CMSMarkStack* _overflow_stack;
1405 bool _yield;
1406 int _skip_bits;
1407 HeapWord* _finger;
1408 HeapWord* _threshold;
1409 CMSConcMarkingTask* _task;
1410 public:
1411 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1412 MemRegion span,
1413 CMSBitMap* bit_map,
1414 OopTaskQueue* work_queue,
1415 CMSMarkStack* overflow_stack,
1416 bool should_yield);
1417 bool do_bit(size_t offset);
1418 inline void do_yield_check();
1419
1420 private:
1421 void scan_oops_in_oop(HeapWord* ptr);
1422 void do_yield_work();
1423 bool get_work_from_overflow_stack();
1424 };
1425
1426 // The following closures are used to do certain kinds of verification of
1427 // CMS marking.
1428 class PushAndMarkVerifyClosure: public CMSOopClosure {
1429 CMSCollector* _collector;
1430 MemRegion _span;
1431 CMSBitMap* _verification_bm;
1432 CMSBitMap* _cms_bm;
1433 CMSMarkStack* _mark_stack;
1434 protected:
1435 void do_oop(oop p);
1436 template <class T> inline void do_oop_work(T *p) {
1437 oop obj = oopDesc::load_decode_heap_oop(p);
1438 do_oop(obj);
1439 }
1440 public:
1441 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1442 MemRegion span,
1443 CMSBitMap* verification_bm,
1444 CMSBitMap* cms_bm,
1445 CMSMarkStack* mark_stack);
1446 void do_oop(oop* p);
1447 void do_oop(narrowOop* p);
1448
1449 // Deal with a stack overflow condition
1450 void handle_stack_overflow(HeapWord* lost);
1451 };
1452
1453 class MarkFromRootsVerifyClosure: public BitMapClosure {
1454 CMSCollector* _collector;
1455 MemRegion _span;
1456 CMSBitMap* _verification_bm;
1457 CMSBitMap* _cms_bm;
1458 CMSMarkStack* _mark_stack;
1459 HeapWord* _finger;
1460 PushAndMarkVerifyClosure _pam_verify_closure;
1461 public:
1462 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1463 CMSBitMap* verification_bm,
1464 CMSBitMap* cms_bm,
1465 CMSMarkStack* mark_stack);
1466 bool do_bit(size_t offset);
1467 void reset(HeapWord* addr);
1468 };
1469
1470
1471 // This closure is used to check that a certain set of bits is
1472 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1473 class FalseBitMapClosure: public BitMapClosure {
1474 public:
1475 bool do_bit(size_t offset) {
1476 guarantee(false, "Should not have a 1 bit");
1477 return true;
1478 }
1479 };
1480
1481 // This closure is used during the second checkpointing phase
1482 // to rescan the marked objects on the dirty cards in the mod
1483 // union table and the card table proper. It's invoked via
1484 // MarkFromDirtyCardsClosure below. It uses either
1485 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1486 // declared in genOopClosures.hpp to accomplish some of its work.
1487 // In the parallel case the bitMap is shared, so access to
1488 // it needs to be suitably synchronized for updates by embedded
1489 // closures that update it; however, this closure itself only
1490 // reads the bit_map and because it is idempotent, is immune to
1491 // reading stale values.
1492 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1493 #ifdef ASSERT
1494 CMSCollector* _collector;
1495 MemRegion _span;
1496 union {
1497 CMSMarkStack* _mark_stack;
1498 OopTaskQueue* _work_queue;
1499 };
1500 #endif // ASSERT
1501 bool _parallel;
1502 CMSBitMap* _bit_map;
1503 union {
1504 MarkRefsIntoAndScanClosure* _scan_closure;
1505 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1506 };
1507
1508 public:
1509 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1510 MemRegion span,
1511 ReferenceProcessor* rp,
1512 CMSBitMap* bit_map,
1513 CMSMarkStack* mark_stack,
1514 MarkRefsIntoAndScanClosure* cl):
1515 #ifdef ASSERT
1516 _collector(collector),
1517 _span(span),
1518 _mark_stack(mark_stack),
1519 #endif // ASSERT
1520 _parallel(false),
1521 _bit_map(bit_map),
1522 _scan_closure(cl) { }
1523
1524 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1525 MemRegion span,
1526 ReferenceProcessor* rp,
1527 CMSBitMap* bit_map,
1528 OopTaskQueue* work_queue,
1529 Par_MarkRefsIntoAndScanClosure* cl):
1530 #ifdef ASSERT
1531 _collector(collector),
1532 _span(span),
1533 _work_queue(work_queue),
1534 #endif // ASSERT
1535 _parallel(true),
1536 _bit_map(bit_map),
1537 _par_scan_closure(cl) { }
1538
1539 void do_object(oop obj) {
1540 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1541 }
1542 bool do_object_b(oop obj) {
1543 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1544 return false;
1545 }
1546 bool do_object_bm(oop p, MemRegion mr);
1547 };
1548
1549 // This closure is used during the second checkpointing phase
1550 // to rescan the marked objects on the dirty cards in the mod
1551 // union table and the card table proper. It invokes
1552 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1553 // In the parallel case, the bit map is shared and requires
1554 // synchronized access.
1555 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1556 CompactibleFreeListSpace* _space;
1557 ScanMarkedObjectsAgainClosure _scan_cl;
1558 size_t _num_dirty_cards;
1559
1560 public:
1561 MarkFromDirtyCardsClosure(CMSCollector* collector,
1562 MemRegion span,
1563 CompactibleFreeListSpace* space,
1564 CMSBitMap* bit_map,
1565 CMSMarkStack* mark_stack,
1566 MarkRefsIntoAndScanClosure* cl):
1567 _space(space),
1568 _num_dirty_cards(0),
1569 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1570 mark_stack, cl) { }
1571
1572 MarkFromDirtyCardsClosure(CMSCollector* collector,
1573 MemRegion span,
1574 CompactibleFreeListSpace* space,
1575 CMSBitMap* bit_map,
1576 OopTaskQueue* work_queue,
1577 Par_MarkRefsIntoAndScanClosure* cl):
1578 _space(space),
1579 _num_dirty_cards(0),
1580 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1581 work_queue, cl) { }
1582
1583 void do_MemRegion(MemRegion mr);
1584 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1585 size_t num_dirty_cards() { return _num_dirty_cards; }
1586 };
1587
1588 // This closure is used in the non-product build to check
1589 // that there are no MemRegions with a certain property.
1590 class FalseMemRegionClosure: public MemRegionClosure {
1591 void do_MemRegion(MemRegion mr) {
1592 guarantee(!mr.is_empty(), "Shouldn't be empty");
1593 guarantee(false, "Should never be here");
1594 }
1595 };
1596
1597 // This closure is used during the precleaning phase
1598 // to "carefully" rescan marked objects on dirty cards.
1599 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1600 // to accomplish some of its work.
1601 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1602 CMSCollector* _collector;
1603 MemRegion _span;
1604 bool _yield;
1605 Mutex* _freelistLock;
1606 CMSBitMap* _bitMap;
1607 CMSMarkStack* _markStack;
1608 MarkRefsIntoAndScanClosure* _scanningClosure;
1609
1610 public:
1611 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1612 MemRegion span,
1613 CMSBitMap* bitMap,
1614 CMSMarkStack* markStack,
1615 MarkRefsIntoAndScanClosure* cl,
1616 bool should_yield):
1617 _collector(collector),
1618 _span(span),
1619 _yield(should_yield),
1620 _bitMap(bitMap),
1621 _markStack(markStack),
1622 _scanningClosure(cl) {
1623 }
1624
1625 void do_object(oop p) {
1626 guarantee(false, "call do_object_careful instead");
1627 }
1628
1629 size_t do_object_careful(oop p) {
1630 guarantee(false, "Unexpected caller");
1631 return 0;
1632 }
1633
1634 size_t do_object_careful_m(oop p, MemRegion mr);
1635
1636 void setFreelistLock(Mutex* m) {
1637 _freelistLock = m;
1638 _scanningClosure->set_freelistLock(m);
1639 }
1640
1641 private:
1642 inline bool do_yield_check();
1643
1644 void do_yield_work();
1645 };
1646
1647 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1648 CMSCollector* _collector;
1649 MemRegion _span;
1650 bool _yield;
1651 CMSBitMap* _bit_map;
1652 CMSMarkStack* _mark_stack;
1653 PushAndMarkClosure* _scanning_closure;
1654 unsigned int _before_count;
1655
1656 public:
1657 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1658 MemRegion span,
1659 CMSBitMap* bit_map,
1660 CMSMarkStack* mark_stack,
1661 PushAndMarkClosure* cl,
1662 unsigned int before_count,
1663 bool should_yield):
1664 _collector(collector),
1665 _span(span),
1666 _yield(should_yield),
1667 _bit_map(bit_map),
1668 _mark_stack(mark_stack),
1669 _scanning_closure(cl),
1670 _before_count(before_count)
1671 { }
1672
1673 void do_object(oop p) {
1674 guarantee(false, "call do_object_careful instead");
1675 }
1676
1677 size_t do_object_careful(oop p);
1678
1679 size_t do_object_careful_m(oop p, MemRegion mr) {
1680 guarantee(false, "Unexpected caller");
1681 return 0;
1682 }
1683
1684 private:
1685 inline void do_yield_check();
1686 void do_yield_work();
1687 };
1688
1689 // This closure is used to accomplish the sweeping work
1690 // after the second checkpoint but before the concurrent reset
1691 // phase.
1692 //
1693 // Terminology
1694 // left hand chunk (LHC) - block of one or more chunks currently being
1695 // coalesced. The LHC is available for coalescing with a new chunk.
1696 // right hand chunk (RHC) - block that is currently being swept that is
1697 // free or garbage that can be coalesced with the LHC.
1698 // _inFreeRange is true if there is currently a LHC
1699 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1700 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1701 // _freeFinger is the address of the current LHC
1702 class SweepClosure: public BlkClosureCareful {
1703 CMSCollector* _collector; // collector doing the work
1704 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1705 CompactibleFreeListSpace* _sp; // Space being swept
1706 HeapWord* _limit;// the address at or above which the sweep should stop
1707 // because we do not expect newly garbage blocks
1708 // eligible for sweeping past that address.
1709 Mutex* _freelistLock; // Free list lock (in space)
1710 CMSBitMap* _bitMap; // Marking bit map (in
1711 // generation)
1712 bool _inFreeRange; // Indicates if we are in the
1713 // midst of a free run
1714 bool _freeRangeInFreeLists;
1715 // Often, we have just found
1716 // a free chunk and started
1717 // a new free range; we do not
1718 // eagerly remove this chunk from
1719 // the free lists unless there is
1720 // a possibility of coalescing.
1721 // When true, this flag indicates
1722 // that the _freeFinger below
1723 // points to a potentially free chunk
1724 // that may still be in the free lists
1725 bool _lastFreeRangeCoalesced;
1726 // free range contains chunks
1727 // coalesced
1728 bool _yield;
1729 // Whether sweeping should be
1730 // done with yields. For instance
1731 // when done by the foreground
1732 // collector we shouldn't yield.
1733 HeapWord* _freeFinger; // When _inFreeRange is set, the
1734 // pointer to the "left hand
1735 // chunk"
1736 size_t _freeRangeSize;
1737 // When _inFreeRange is set, this
1738 // indicates the accumulated size
1739 // of the "left hand chunk"
1740 NOT_PRODUCT(
1741 size_t _numObjectsFreed;
1742 size_t _numWordsFreed;
1743 size_t _numObjectsLive;
1744 size_t _numWordsLive;
1745 size_t _numObjectsAlreadyFree;
1746 size_t _numWordsAlreadyFree;
1747 FreeChunk* _last_fc;
1748 )
1749 private:
1750 // Code that is common to a free chunk or garbage when
1751 // encountered during sweeping.
1752 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1753 // Process a free chunk during sweeping.
1754 void do_already_free_chunk(FreeChunk *fc);
1755 // Work method called when processing an already free or a
1756 // freshly garbage chunk to do a lookahead and possibly a
1757 // premptive flush if crossing over _limit.
1758 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1759 // Process a garbage chunk during sweeping.
1760 size_t do_garbage_chunk(FreeChunk *fc);
1761 // Process a live chunk during sweeping.
1762 size_t do_live_chunk(FreeChunk* fc);
1763
1764 // Accessors.
1765 HeapWord* freeFinger() const { return _freeFinger; }
1766 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1767 bool inFreeRange() const { return _inFreeRange; }
1768 void set_inFreeRange(bool v) { _inFreeRange = v; }
1769 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1770 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1771 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1772 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1773
1774 // Initialize a free range.
1775 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1776 // Return this chunk to the free lists.
1777 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1778
1779 // Check if we should yield and do so when necessary.
1780 inline void do_yield_check(HeapWord* addr);
1781
1782 // Yield
1783 void do_yield_work(HeapWord* addr);
1784
1785 // Debugging/Printing
1786 void print_free_block_coalesced(FreeChunk* fc) const;
1787
1788 public:
1789 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1790 CMSBitMap* bitMap, bool should_yield);
1791 ~SweepClosure() PRODUCT_RETURN;
1792
1793 size_t do_blk_careful(HeapWord* addr);
1794 void print() const { print_on(tty); }
1795 void print_on(outputStream *st) const;
1796 };
1797
1798 // Closures related to weak references processing
1799
1800 // During CMS' weak reference processing, this is a
1801 // work-routine/closure used to complete transitive
1802 // marking of objects as live after a certain point
1803 // in which an initial set has been completely accumulated.
1804 // This closure is currently used both during the final
1805 // remark stop-world phase, as well as during the concurrent
1806 // precleaning of the discovered reference lists.
1807 class CMSDrainMarkingStackClosure: public VoidClosure {
1808 CMSCollector* _collector;
1809 MemRegion _span;
1810 CMSMarkStack* _mark_stack;
1811 CMSBitMap* _bit_map;
1812 CMSKeepAliveClosure* _keep_alive;
1813 bool _concurrent_precleaning;
1814 public:
1815 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1816 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1817 CMSKeepAliveClosure* keep_alive,
1818 bool cpc):
1819 _collector(collector),
1820 _span(span),
1821 _bit_map(bit_map),
1822 _mark_stack(mark_stack),
1823 _keep_alive(keep_alive),
1824 _concurrent_precleaning(cpc) {
1825 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1826 "Mismatch");
1827 }
1828
1829 void do_void();
1830 };
1831
1832 // A parallel version of CMSDrainMarkingStackClosure above.
1833 class CMSParDrainMarkingStackClosure: public VoidClosure {
1834 CMSCollector* _collector;
1835 MemRegion _span;
1836 OopTaskQueue* _work_queue;
1837 CMSBitMap* _bit_map;
1838 CMSInnerParMarkAndPushClosure _mark_and_push;
1839
1840 public:
1841 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1842 MemRegion span, CMSBitMap* bit_map,
1843 OopTaskQueue* work_queue):
1844 _collector(collector),
1845 _span(span),
1846 _bit_map(bit_map),
1847 _work_queue(work_queue),
1848 _mark_and_push(collector, span, bit_map, work_queue) { }
1849
1850 public:
1851 void trim_queue(uint max);
1852 void do_void();
1853 };
1854
1855 // Allow yielding or short-circuiting of reference list
1856 // prelceaning work.
1857 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1858 CMSCollector* _collector;
1859 void do_yield_work();
1860 public:
1861 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1862 _collector(collector) {}
1863 virtual bool should_return();
1864 };
1865
1866
1867 // Convenience class that locks free list locks for given CMS collector
1868 class FreelistLocker: public StackObj {
1869 private:
1870 CMSCollector* _collector;
1871 public:
1872 FreelistLocker(CMSCollector* collector):
1873 _collector(collector) {
1874 _collector->getFreelistLocks();
1875 }
1876
1877 ~FreelistLocker() {
1878 _collector->releaseFreelistLocks();
1879 }
1880 };
1881
1882 // Mark all dead objects in a given space.
1883 class MarkDeadObjectsClosure: public BlkClosure {
1884 const CMSCollector* _collector;
1885 const CompactibleFreeListSpace* _sp;
1886 CMSBitMap* _live_bit_map;
1887 CMSBitMap* _dead_bit_map;
1888 public:
1889 MarkDeadObjectsClosure(const CMSCollector* collector,
1890 const CompactibleFreeListSpace* sp,
1891 CMSBitMap *live_bit_map,
1892 CMSBitMap *dead_bit_map) :
1893 _collector(collector),
1894 _sp(sp),
1895 _live_bit_map(live_bit_map),
1896 _dead_bit_map(dead_bit_map) {}
1897 size_t do_blk(HeapWord* addr);
1898 };
1899
1900 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1901
1902 public:
1903 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1904 };
1905
1906
1907 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP