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 // This is meant to be a boolean flag, but jbyte for CAS.
740 jbyte _eden_chunk_sampling_active;
741
742 // Support for parallelizing survivor space rescan
743 HeapWord** _survivor_chunk_array;
744 size_t _survivor_chunk_index;
745 size_t _survivor_chunk_capacity;
746 size_t* _cursor;
747 ChunkArray* _survivor_plab_array;
748
749 // Support for marking stack overflow handling
750 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
751 bool par_take_from_overflow_list(size_t num,
752 OopTaskQueue* to_work_q,
753 int no_of_gc_threads);
754 void push_on_overflow_list(oop p);
755 void par_push_on_overflow_list(oop p);
756 // the following is, obviously, not, in general, "MT-stable"
757 bool overflow_list_is_empty() const;
758
759 void preserve_mark_if_necessary(oop p);
760 void par_preserve_mark_if_necessary(oop p);
761 void preserve_mark_work(oop p, markOop m);
762 void restore_preserved_marks_if_any();
763 NOT_PRODUCT(bool no_preserved_marks() const;)
764 // in support of testing overflow code
765 NOT_PRODUCT(int _overflow_counter;)
766 NOT_PRODUCT(bool simulate_overflow();) // sequential
767 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
768
769 // CMS work methods
770 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
771
772 // a return value of false indicates failure due to stack overflow
773 bool markFromRootsWork(bool asynch); // concurrent marking work
774
775 public: // FIX ME!!! only for testing
776 bool do_marking_st(bool asynch); // single-threaded marking
777 bool do_marking_mt(bool asynch); // multi-threaded marking
778
779 private:
780
781 // concurrent precleaning work
782 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
783 ScanMarkedObjectsAgainCarefullyClosure* cl);
784 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
785 ScanMarkedObjectsAgainCarefullyClosure* cl);
786 // Does precleaning work, returning a quantity indicative of
787 // the amount of "useful work" done.
788 size_t preclean_work(bool clean_refs, bool clean_survivors);
789 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
790 void abortable_preclean(); // Preclean while looking for possible abort
791 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
792 // Helper function for above; merge-sorts the per-thread plab samples
793 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
794 // Resets (i.e. clears) the per-thread plab sample vectors
795 void reset_survivor_plab_arrays();
796
797 // final (second) checkpoint work
798 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
799 bool init_mark_was_synchronous);
800 // work routine for parallel version of remark
801 void do_remark_parallel();
802 // work routine for non-parallel version of remark
803 void do_remark_non_parallel();
804 // reference processing work routine (during second checkpoint)
805 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
806
807 // concurrent sweeping work
808 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
809
810 // (concurrent) resetting of support data structures
811 void reset(bool asynch);
812
813 // Clear _expansion_cause fields of constituent generations
814 void clear_expansion_cause();
815
816 // An auxilliary method used to record the ends of
817 // used regions of each generation to limit the extent of sweep
818 void save_sweep_limits();
819
820 // A work method used by foreground collection to determine
821 // what type of collection (compacting or not, continuing or fresh)
822 // it should do.
823 void decide_foreground_collection_type(bool clear_all_soft_refs,
824 bool* should_compact, bool* should_start_over);
825
826 // A work method used by the foreground collector to do
827 // a mark-sweep-compact.
828 void do_compaction_work(bool clear_all_soft_refs);
829
830 // A work method used by the foreground collector to do
831 // a mark-sweep, after taking over from a possibly on-going
832 // concurrent mark-sweep collection.
833 void do_mark_sweep_work(bool clear_all_soft_refs,
834 CollectorState first_state, bool should_start_over);
835
836 // If the backgrould GC is active, acquire control from the background
837 // GC and do the collection.
838 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
839
840 // For synchronizing passing of control from background to foreground
841 // GC. waitForForegroundGC() is called by the background
842 // collector. It if had to wait for a foreground collection,
843 // it returns true and the background collection should assume
844 // that the collection was finished by the foreground
845 // collector.
846 bool waitForForegroundGC();
847
848 // Incremental mode triggering: recompute the icms duty cycle and set the
849 // allocation limits in the young gen.
850 void icms_update_allocation_limits();
851
852 size_t block_size_using_printezis_bits(HeapWord* addr) const;
853 size_t block_size_if_printezis_bits(HeapWord* addr) const;
854 HeapWord* next_card_start_after_block(HeapWord* addr) const;
855
856 void setup_cms_unloading_and_verification_state();
857 public:
858 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
859 CardTableRS* ct,
860 ConcurrentMarkSweepPolicy* cp);
861 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
862
863 ReferenceProcessor* ref_processor() { return _ref_processor; }
864 void ref_processor_init();
865
866 Mutex* bitMapLock() const { return _markBitMap.lock(); }
867 static CollectorState abstract_state() { return _collectorState; }
868
869 bool should_abort_preclean() const; // Whether preclean should be aborted.
870 size_t get_eden_used() const;
871 size_t get_eden_capacity() const;
872
873 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
874
875 // locking checks
876 NOT_PRODUCT(static bool have_cms_token();)
877
878 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
879 bool shouldConcurrentCollect();
880
881 void collect(bool full,
882 bool clear_all_soft_refs,
883 size_t size,
884 bool tlab);
885 void collect_in_background(bool clear_all_soft_refs);
886 void collect_in_foreground(bool clear_all_soft_refs);
887
888 // In support of ExplicitGCInvokesConcurrent
889 static void request_full_gc(unsigned int full_gc_count);
890 // Should we unload classes in a particular concurrent cycle?
891 bool should_unload_classes() const {
892 return _should_unload_classes;
893 }
894 void update_should_unload_classes();
895
896 void direct_allocated(HeapWord* start, size_t size);
897
898 // Object is dead if not marked and current phase is sweeping.
899 bool is_dead_obj(oop obj) const;
900
901 // After a promotion (of "start"), do any necessary marking.
902 // If "par", then it's being done by a parallel GC thread.
903 // The last two args indicate if we need precise marking
904 // and if so the size of the object so it can be dirtied
905 // in its entirety.
906 void promoted(bool par, HeapWord* start,
907 bool is_obj_array, size_t obj_size);
908
909 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
910 size_t word_size);
911
912 void getFreelistLocks() const;
913 void releaseFreelistLocks() const;
914 bool haveFreelistLocks() const;
915
916 // Adjust size of underlying generation
917 void compute_new_size();
918
919 // GC prologue and epilogue
920 void gc_prologue(bool full);
921 void gc_epilogue(bool full);
922
923 jlong time_of_last_gc(jlong now) {
924 if (_collectorState <= Idling) {
925 // gc not in progress
926 return _time_of_last_gc;
927 } else {
928 // collection in progress
929 return now;
930 }
931 }
932
933 // Support for parallel remark of survivor space
934 void* get_data_recorder(int thr_num);
935 void sample_eden_chunk();
936
937 CMSBitMap* markBitMap() { return &_markBitMap; }
938 void directAllocated(HeapWord* start, size_t size);
939
940 // main CMS steps and related support
941 void checkpointRootsInitial(bool asynch);
942 bool markFromRoots(bool asynch); // a return value of false indicates failure
943 // due to stack overflow
944 void preclean();
945 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
946 bool init_mark_was_synchronous);
947 void sweep(bool asynch);
948
949 // Check that the currently executing thread is the expected
950 // one (foreground collector or background collector).
951 static void check_correct_thread_executing() PRODUCT_RETURN;
952 // XXXPERM void print_statistics() PRODUCT_RETURN;
953
954 bool is_cms_reachable(HeapWord* addr);
955
956 // Performance Counter Support
957 CollectorCounters* counters() { return _gc_counters; }
958
959 // timer stuff
960 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
961 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
962 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
963 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
964
965 int yields() { return _numYields; }
966 void resetYields() { _numYields = 0; }
967 void incrementYields() { _numYields++; }
968 void resetNumDirtyCards() { _numDirtyCards = 0; }
969 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
970 size_t numDirtyCards() { return _numDirtyCards; }
971
972 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
973 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
974 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
975 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
976 size_t sweep_count() const { return _sweep_count; }
977 void increment_sweep_count() { _sweep_count++; }
978
979 // Timers/stats for gc scheduling and incremental mode pacing.
980 CMSStats& stats() { return _stats; }
981
982 // Convenience methods that check whether CMSIncrementalMode is enabled and
983 // forward to the corresponding methods in ConcurrentMarkSweepThread.
984 static void start_icms();
985 static void stop_icms(); // Called at the end of the cms cycle.
986 static void disable_icms(); // Called before a foreground collection.
987 static void enable_icms(); // Called after a foreground collection.
988 void icms_wait(); // Called at yield points.
989
990 // Adaptive size policy
991 CMSAdaptiveSizePolicy* size_policy();
992 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
993
994 static void print_on_error(outputStream* st);
995
996 // debugging
997 void verify();
998 bool verify_after_remark(bool silent = VerifySilently);
999 void verify_ok_to_terminate() const PRODUCT_RETURN;
1000 void verify_work_stacks_empty() const PRODUCT_RETURN;
1001 void verify_overflow_empty() const PRODUCT_RETURN;
1002
1003 // convenience methods in support of debugging
1004 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1005 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1006
1007 // accessors
1008 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1009 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1010
1011 // Initialization errors
1012 bool completed_initialization() { return _completed_initialization; }
1013
1014 void print_eden_and_survivor_chunk_arrays();
1015 };
1016
1017 class CMSExpansionCause : public AllStatic {
1018 public:
1019 enum Cause {
1020 _no_expansion,
1021 _satisfy_free_ratio,
1022 _satisfy_promotion,
1023 _satisfy_allocation,
1024 _allocate_par_lab,
1025 _allocate_par_spooling_space,
1026 _adaptive_size_policy
1027 };
1028 // Return a string describing the cause of the expansion.
1029 static const char* to_string(CMSExpansionCause::Cause cause);
1030 };
1031
1032 class ConcurrentMarkSweepGeneration: public CardGeneration {
1033 friend class VMStructs;
1034 friend class ConcurrentMarkSweepThread;
1035 friend class ConcurrentMarkSweep;
1036 friend class CMSCollector;
1037 protected:
1038 static CMSCollector* _collector; // the collector that collects us
1039 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1040
1041 // Performance Counters
1042 GenerationCounters* _gen_counters;
1043 GSpaceCounters* _space_counters;
1044
1045 // Words directly allocated, used by CMSStats.
1046 size_t _direct_allocated_words;
1047
1048 // Non-product stat counters
1049 NOT_PRODUCT(
1050 size_t _numObjectsPromoted;
1051 size_t _numWordsPromoted;
1052 size_t _numObjectsAllocated;
1053 size_t _numWordsAllocated;
1054 )
1055
1056 // Used for sizing decisions
1057 bool _incremental_collection_failed;
1058 bool incremental_collection_failed() {
1059 return _incremental_collection_failed;
1060 }
1061 void set_incremental_collection_failed() {
1062 _incremental_collection_failed = true;
1063 }
1064 void clear_incremental_collection_failed() {
1065 _incremental_collection_failed = false;
1066 }
1067
1068 // accessors
1069 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1070 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1071
1072 private:
1073 // For parallel young-gen GC support.
1074 CMSParGCThreadState** _par_gc_thread_states;
1075
1076 // Reason generation was expanded
1077 CMSExpansionCause::Cause _expansion_cause;
1078
1079 // In support of MinChunkSize being larger than min object size
1080 const double _dilatation_factor;
1081
1082 enum CollectionTypes {
1083 Concurrent_collection_type = 0,
1084 MS_foreground_collection_type = 1,
1085 MSC_foreground_collection_type = 2,
1086 Unknown_collection_type = 3
1087 };
1088
1089 CollectionTypes _debug_collection_type;
1090
1091 // True if a compactiing collection was done.
1092 bool _did_compact;
1093 bool did_compact() { return _did_compact; }
1094
1095 // Fraction of current occupancy at which to start a CMS collection which
1096 // will collect this generation (at least).
1097 double _initiating_occupancy;
1098
1099 protected:
1100 // Shrink generation by specified size (returns false if unable to shrink)
1101 void shrink_free_list_by(size_t bytes);
1102
1103 // Update statistics for GC
1104 virtual void update_gc_stats(int level, bool full);
1105
1106 // Maximum available space in the generation (including uncommitted)
1107 // space.
1108 size_t max_available() const;
1109
1110 // getter and initializer for _initiating_occupancy field.
1111 double initiating_occupancy() const { return _initiating_occupancy; }
1112 void init_initiating_occupancy(intx io, uintx tr);
1113
1114 public:
1115 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1116 int level, CardTableRS* ct,
1117 bool use_adaptive_freelists,
1118 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1119
1120 // Accessors
1121 CMSCollector* collector() const { return _collector; }
1122 static void set_collector(CMSCollector* collector) {
1123 assert(_collector == NULL, "already set");
1124 _collector = collector;
1125 }
1126 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1127
1128 Mutex* freelistLock() const;
1129
1130 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1131
1132 // Adaptive size policy
1133 CMSAdaptiveSizePolicy* size_policy();
1134
1135 void set_did_compact(bool v) { _did_compact = v; }
1136
1137 bool refs_discovery_is_atomic() const { return false; }
1138 bool refs_discovery_is_mt() const {
1139 // Note: CMS does MT-discovery during the parallel-remark
1140 // phases. Use ReferenceProcessorMTMutator to make refs
1141 // discovery MT-safe during such phases or other parallel
1142 // discovery phases in the future. This may all go away
1143 // if/when we decide that refs discovery is sufficiently
1144 // rare that the cost of the CAS's involved is in the
1145 // noise. That's a measurement that should be done, and
1146 // the code simplified if that turns out to be the case.
1147 return ConcGCThreads > 1;
1148 }
1149
1150 // Override
1151 virtual void ref_processor_init();
1152
1153 // Grow generation by specified size (returns false if unable to grow)
1154 bool grow_by(size_t bytes);
1155 // Grow generation to reserved size.
1156 bool grow_to_reserved();
1157
1158 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1159
1160 // Space enquiries
1161 size_t capacity() const;
1162 size_t used() const;
1163 size_t free() const;
1164 double occupancy() const { return ((double)used())/((double)capacity()); }
1165 size_t contiguous_available() const;
1166 size_t unsafe_max_alloc_nogc() const;
1167
1168 // over-rides
1169 MemRegion used_region() const;
1170 MemRegion used_region_at_save_marks() const;
1171
1172 // Does a "full" (forced) collection invoked on this generation collect
1173 // all younger generations as well? Note that the second conjunct is a
1174 // hack to allow the collection of the younger gen first if the flag is
1175 // set. This is better than using th policy's should_collect_gen0_first()
1176 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1177 virtual bool full_collects_younger_generations() const {
1178 return UseCMSCompactAtFullCollection && !CollectGen0First;
1179 }
1180
1181 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1182
1183 // Support for compaction
1184 CompactibleSpace* first_compaction_space() const;
1185 // Adjust quantites in the generation affected by
1186 // the compaction.
1187 void reset_after_compaction();
1188
1189 // Allocation support
1190 HeapWord* allocate(size_t size, bool tlab);
1191 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1192 oop promote(oop obj, size_t obj_size);
1193 HeapWord* par_allocate(size_t size, bool tlab) {
1194 return allocate(size, tlab);
1195 }
1196
1197 // Incremental mode triggering.
1198 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1199 size_t word_size);
1200
1201 // Used by CMSStats to track direct allocation. The value is sampled and
1202 // reset after each young gen collection.
1203 size_t direct_allocated_words() const { return _direct_allocated_words; }
1204 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1205
1206 // Overrides for parallel promotion.
1207 virtual oop par_promote(int thread_num,
1208 oop obj, markOop m, size_t word_sz);
1209 // This one should not be called for CMS.
1210 virtual void par_promote_alloc_undo(int thread_num,
1211 HeapWord* obj, size_t word_sz);
1212 virtual void par_promote_alloc_done(int thread_num);
1213 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1214
1215 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1216
1217 // Inform this (non-young) generation that a promotion failure was
1218 // encountered during a collection of a younger generation that
1219 // promotes into this generation.
1220 virtual void promotion_failure_occurred();
1221
1222 bool should_collect(bool full, size_t size, bool tlab);
1223 virtual bool should_concurrent_collect() const;
1224 virtual bool is_too_full() const;
1225 void collect(bool full,
1226 bool clear_all_soft_refs,
1227 size_t size,
1228 bool tlab);
1229
1230 HeapWord* expand_and_allocate(size_t word_size,
1231 bool tlab,
1232 bool parallel = false);
1233
1234 // GC prologue and epilogue
1235 void gc_prologue(bool full);
1236 void gc_prologue_work(bool full, bool registerClosure,
1237 ModUnionClosure* modUnionClosure);
1238 void gc_epilogue(bool full);
1239 void gc_epilogue_work(bool full);
1240
1241 // Time since last GC of this generation
1242 jlong time_of_last_gc(jlong now) {
1243 return collector()->time_of_last_gc(now);
1244 }
1245 void update_time_of_last_gc(jlong now) {
1246 collector()-> update_time_of_last_gc(now);
1247 }
1248
1249 // Allocation failure
1250 void expand(size_t bytes, size_t expand_bytes,
1251 CMSExpansionCause::Cause cause);
1252 virtual bool expand(size_t bytes, size_t expand_bytes);
1253 void shrink(size_t bytes);
1254 void shrink_by(size_t bytes);
1255 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1256 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1257
1258 // Iteration support and related enquiries
1259 void save_marks();
1260 bool no_allocs_since_save_marks();
1261 void object_iterate_since_last_GC(ObjectClosure* cl);
1262 void younger_refs_iterate(OopsInGenClosure* cl);
1263
1264 // Iteration support specific to CMS generations
1265 void save_sweep_limit();
1266
1267 // More iteration support
1268 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1269 virtual void oop_iterate(ExtendedOopClosure* cl);
1270 virtual void safe_object_iterate(ObjectClosure* cl);
1271 virtual void object_iterate(ObjectClosure* cl);
1272
1273 // Need to declare the full complement of closures, whether we'll
1274 // override them or not, or get message from the compiler:
1275 // oop_since_save_marks_iterate_nv hides virtual function...
1276 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1277 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1278 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1279
1280 // Smart allocation XXX -- move to CFLSpace?
1281 void setNearLargestChunk();
1282 bool isNearLargestChunk(HeapWord* addr);
1283
1284 // Get the chunk at the end of the space. Delagates to
1285 // the space.
1286 FreeChunk* find_chunk_at_end();
1287
1288 void post_compact();
1289
1290 // Debugging
1291 void prepare_for_verify();
1292 void verify();
1293 void print_statistics() PRODUCT_RETURN;
1294
1295 // Performance Counters support
1296 virtual void update_counters();
1297 virtual void update_counters(size_t used);
1298 void initialize_performance_counters();
1299 CollectorCounters* counters() { return collector()->counters(); }
1300
1301 // Support for parallel remark of survivor space
1302 void* get_data_recorder(int thr_num) {
1303 //Delegate to collector
1304 return collector()->get_data_recorder(thr_num);
1305 }
1306 void sample_eden_chunk() {
1307 //Delegate to collector
1308 return collector()->sample_eden_chunk();
1309 }
1310
1311 // Printing
1312 const char* name() const;
1313 virtual const char* short_name() const { return "CMS"; }
1314 void print() const;
1315 void printOccupancy(const char* s);
1316 bool must_be_youngest() const { return false; }
1317 bool must_be_oldest() const { return true; }
1318
1319 // Resize the generation after a compacting GC. The
1320 // generation can be treated as a contiguous space
1321 // after the compaction.
1322 virtual void compute_new_size();
1323 // Resize the generation after a non-compacting
1324 // collection.
1325 void compute_new_size_free_list();
1326
1327 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1328 void rotate_debug_collection_type();
1329 };
1330
1331 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1332
1333 // Return the size policy from the heap's collector
1334 // policy casted to CMSAdaptiveSizePolicy*.
1335 CMSAdaptiveSizePolicy* cms_size_policy() const;
1336
1337 // Resize the generation based on the adaptive size
1338 // policy.
1339 void resize(size_t cur_promo, size_t desired_promo);
1340
1341 // Return the GC counters from the collector policy
1342 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1343
1344 virtual void shrink_by(size_t bytes);
1345
1346 public:
1347 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1348 int level, CardTableRS* ct,
1349 bool use_adaptive_freelists,
1350 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1351 dictionaryChoice) :
1352 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1353 use_adaptive_freelists, dictionaryChoice) {}
1354
1355 virtual const char* short_name() const { return "ASCMS"; }
1356 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1357
1358 virtual void update_counters();
1359 virtual void update_counters(size_t used);
1360 };
1361
1362 //
1363 // Closures of various sorts used by CMS to accomplish its work
1364 //
1365
1366 // This closure is used to check that a certain set of oops is empty.
1367 class FalseClosure: public OopClosure {
1368 public:
1369 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1370 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1371 };
1372
1373 // This closure is used to do concurrent marking from the roots
1374 // following the first checkpoint.
1375 class MarkFromRootsClosure: public BitMapClosure {
1376 CMSCollector* _collector;
1377 MemRegion _span;
1378 CMSBitMap* _bitMap;
1379 CMSBitMap* _mut;
1380 CMSMarkStack* _markStack;
1381 bool _yield;
1382 int _skipBits;
1383 HeapWord* _finger;
1384 HeapWord* _threshold;
1385 DEBUG_ONLY(bool _verifying;)
1386
1387 public:
1388 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1389 CMSBitMap* bitMap,
1390 CMSMarkStack* markStack,
1391 bool should_yield, bool verifying = false);
1392 bool do_bit(size_t offset);
1393 void reset(HeapWord* addr);
1394 inline void do_yield_check();
1395
1396 private:
1397 void scanOopsInOop(HeapWord* ptr);
1398 void do_yield_work();
1399 };
1400
1401 // This closure is used to do concurrent multi-threaded
1402 // marking from the roots following the first checkpoint.
1403 // XXX This should really be a subclass of The serial version
1404 // above, but i have not had the time to refactor things cleanly.
1405 // That willbe done for Dolphin.
1406 class Par_MarkFromRootsClosure: public BitMapClosure {
1407 CMSCollector* _collector;
1408 MemRegion _whole_span;
1409 MemRegion _span;
1410 CMSBitMap* _bit_map;
1411 CMSBitMap* _mut;
1412 OopTaskQueue* _work_queue;
1413 CMSMarkStack* _overflow_stack;
1414 bool _yield;
1415 int _skip_bits;
1416 HeapWord* _finger;
1417 HeapWord* _threshold;
1418 CMSConcMarkingTask* _task;
1419 public:
1420 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1421 MemRegion span,
1422 CMSBitMap* bit_map,
1423 OopTaskQueue* work_queue,
1424 CMSMarkStack* overflow_stack,
1425 bool should_yield);
1426 bool do_bit(size_t offset);
1427 inline void do_yield_check();
1428
1429 private:
1430 void scan_oops_in_oop(HeapWord* ptr);
1431 void do_yield_work();
1432 bool get_work_from_overflow_stack();
1433 };
1434
1435 // The following closures are used to do certain kinds of verification of
1436 // CMS marking.
1437 class PushAndMarkVerifyClosure: public CMSOopClosure {
1438 CMSCollector* _collector;
1439 MemRegion _span;
1440 CMSBitMap* _verification_bm;
1441 CMSBitMap* _cms_bm;
1442 CMSMarkStack* _mark_stack;
1443 protected:
1444 void do_oop(oop p);
1445 template <class T> inline void do_oop_work(T *p) {
1446 oop obj = oopDesc::load_decode_heap_oop(p);
1447 do_oop(obj);
1448 }
1449 public:
1450 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1451 MemRegion span,
1452 CMSBitMap* verification_bm,
1453 CMSBitMap* cms_bm,
1454 CMSMarkStack* mark_stack);
1455 void do_oop(oop* p);
1456 void do_oop(narrowOop* p);
1457
1458 // Deal with a stack overflow condition
1459 void handle_stack_overflow(HeapWord* lost);
1460 };
1461
1462 class MarkFromRootsVerifyClosure: public BitMapClosure {
1463 CMSCollector* _collector;
1464 MemRegion _span;
1465 CMSBitMap* _verification_bm;
1466 CMSBitMap* _cms_bm;
1467 CMSMarkStack* _mark_stack;
1468 HeapWord* _finger;
1469 PushAndMarkVerifyClosure _pam_verify_closure;
1470 public:
1471 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1472 CMSBitMap* verification_bm,
1473 CMSBitMap* cms_bm,
1474 CMSMarkStack* mark_stack);
1475 bool do_bit(size_t offset);
1476 void reset(HeapWord* addr);
1477 };
1478
1479
1480 // This closure is used to check that a certain set of bits is
1481 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1482 class FalseBitMapClosure: public BitMapClosure {
1483 public:
1484 bool do_bit(size_t offset) {
1485 guarantee(false, "Should not have a 1 bit");
1486 return true;
1487 }
1488 };
1489
1490 // This closure is used during the second checkpointing phase
1491 // to rescan the marked objects on the dirty cards in the mod
1492 // union table and the card table proper. It's invoked via
1493 // MarkFromDirtyCardsClosure below. It uses either
1494 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1495 // declared in genOopClosures.hpp to accomplish some of its work.
1496 // In the parallel case the bitMap is shared, so access to
1497 // it needs to be suitably synchronized for updates by embedded
1498 // closures that update it; however, this closure itself only
1499 // reads the bit_map and because it is idempotent, is immune to
1500 // reading stale values.
1501 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1502 #ifdef ASSERT
1503 CMSCollector* _collector;
1504 MemRegion _span;
1505 union {
1506 CMSMarkStack* _mark_stack;
1507 OopTaskQueue* _work_queue;
1508 };
1509 #endif // ASSERT
1510 bool _parallel;
1511 CMSBitMap* _bit_map;
1512 union {
1513 MarkRefsIntoAndScanClosure* _scan_closure;
1514 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1515 };
1516
1517 public:
1518 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1519 MemRegion span,
1520 ReferenceProcessor* rp,
1521 CMSBitMap* bit_map,
1522 CMSMarkStack* mark_stack,
1523 MarkRefsIntoAndScanClosure* cl):
1524 #ifdef ASSERT
1525 _collector(collector),
1526 _span(span),
1527 _mark_stack(mark_stack),
1528 #endif // ASSERT
1529 _parallel(false),
1530 _bit_map(bit_map),
1531 _scan_closure(cl) { }
1532
1533 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1534 MemRegion span,
1535 ReferenceProcessor* rp,
1536 CMSBitMap* bit_map,
1537 OopTaskQueue* work_queue,
1538 Par_MarkRefsIntoAndScanClosure* cl):
1539 #ifdef ASSERT
1540 _collector(collector),
1541 _span(span),
1542 _work_queue(work_queue),
1543 #endif // ASSERT
1544 _parallel(true),
1545 _bit_map(bit_map),
1546 _par_scan_closure(cl) { }
1547
1548 void do_object(oop obj) {
1549 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1550 }
1551 bool do_object_b(oop obj) {
1552 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1553 return false;
1554 }
1555 bool do_object_bm(oop p, MemRegion mr);
1556 };
1557
1558 // This closure is used during the second checkpointing phase
1559 // to rescan the marked objects on the dirty cards in the mod
1560 // union table and the card table proper. It invokes
1561 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1562 // In the parallel case, the bit map is shared and requires
1563 // synchronized access.
1564 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1565 CompactibleFreeListSpace* _space;
1566 ScanMarkedObjectsAgainClosure _scan_cl;
1567 size_t _num_dirty_cards;
1568
1569 public:
1570 MarkFromDirtyCardsClosure(CMSCollector* collector,
1571 MemRegion span,
1572 CompactibleFreeListSpace* space,
1573 CMSBitMap* bit_map,
1574 CMSMarkStack* mark_stack,
1575 MarkRefsIntoAndScanClosure* cl):
1576 _space(space),
1577 _num_dirty_cards(0),
1578 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1579 mark_stack, cl) { }
1580
1581 MarkFromDirtyCardsClosure(CMSCollector* collector,
1582 MemRegion span,
1583 CompactibleFreeListSpace* space,
1584 CMSBitMap* bit_map,
1585 OopTaskQueue* work_queue,
1586 Par_MarkRefsIntoAndScanClosure* cl):
1587 _space(space),
1588 _num_dirty_cards(0),
1589 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1590 work_queue, cl) { }
1591
1592 void do_MemRegion(MemRegion mr);
1593 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1594 size_t num_dirty_cards() { return _num_dirty_cards; }
1595 };
1596
1597 // This closure is used in the non-product build to check
1598 // that there are no MemRegions with a certain property.
1599 class FalseMemRegionClosure: public MemRegionClosure {
1600 void do_MemRegion(MemRegion mr) {
1601 guarantee(!mr.is_empty(), "Shouldn't be empty");
1602 guarantee(false, "Should never be here");
1603 }
1604 };
1605
1606 // This closure is used during the precleaning phase
1607 // to "carefully" rescan marked objects on dirty cards.
1608 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1609 // to accomplish some of its work.
1610 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1611 CMSCollector* _collector;
1612 MemRegion _span;
1613 bool _yield;
1614 Mutex* _freelistLock;
1615 CMSBitMap* _bitMap;
1616 CMSMarkStack* _markStack;
1617 MarkRefsIntoAndScanClosure* _scanningClosure;
1618
1619 public:
1620 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1621 MemRegion span,
1622 CMSBitMap* bitMap,
1623 CMSMarkStack* markStack,
1624 MarkRefsIntoAndScanClosure* cl,
1625 bool should_yield):
1626 _collector(collector),
1627 _span(span),
1628 _yield(should_yield),
1629 _bitMap(bitMap),
1630 _markStack(markStack),
1631 _scanningClosure(cl) {
1632 }
1633
1634 void do_object(oop p) {
1635 guarantee(false, "call do_object_careful instead");
1636 }
1637
1638 size_t do_object_careful(oop p) {
1639 guarantee(false, "Unexpected caller");
1640 return 0;
1641 }
1642
1643 size_t do_object_careful_m(oop p, MemRegion mr);
1644
1645 void setFreelistLock(Mutex* m) {
1646 _freelistLock = m;
1647 _scanningClosure->set_freelistLock(m);
1648 }
1649
1650 private:
1651 inline bool do_yield_check();
1652
1653 void do_yield_work();
1654 };
1655
1656 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1657 CMSCollector* _collector;
1658 MemRegion _span;
1659 bool _yield;
1660 CMSBitMap* _bit_map;
1661 CMSMarkStack* _mark_stack;
1662 PushAndMarkClosure* _scanning_closure;
1663 unsigned int _before_count;
1664
1665 public:
1666 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1667 MemRegion span,
1668 CMSBitMap* bit_map,
1669 CMSMarkStack* mark_stack,
1670 PushAndMarkClosure* cl,
1671 unsigned int before_count,
1672 bool should_yield):
1673 _collector(collector),
1674 _span(span),
1675 _yield(should_yield),
1676 _bit_map(bit_map),
1677 _mark_stack(mark_stack),
1678 _scanning_closure(cl),
1679 _before_count(before_count)
1680 { }
1681
1682 void do_object(oop p) {
1683 guarantee(false, "call do_object_careful instead");
1684 }
1685
1686 size_t do_object_careful(oop p);
1687
1688 size_t do_object_careful_m(oop p, MemRegion mr) {
1689 guarantee(false, "Unexpected caller");
1690 return 0;
1691 }
1692
1693 private:
1694 inline void do_yield_check();
1695 void do_yield_work();
1696 };
1697
1698 // This closure is used to accomplish the sweeping work
1699 // after the second checkpoint but before the concurrent reset
1700 // phase.
1701 //
1702 // Terminology
1703 // left hand chunk (LHC) - block of one or more chunks currently being
1704 // coalesced. The LHC is available for coalescing with a new chunk.
1705 // right hand chunk (RHC) - block that is currently being swept that is
1706 // free or garbage that can be coalesced with the LHC.
1707 // _inFreeRange is true if there is currently a LHC
1708 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1709 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1710 // _freeFinger is the address of the current LHC
1711 class SweepClosure: public BlkClosureCareful {
1712 CMSCollector* _collector; // collector doing the work
1713 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1714 CompactibleFreeListSpace* _sp; // Space being swept
1715 HeapWord* _limit;// the address at or above which the sweep should stop
1716 // because we do not expect newly garbage blocks
1717 // eligible for sweeping past that address.
1718 Mutex* _freelistLock; // Free list lock (in space)
1719 CMSBitMap* _bitMap; // Marking bit map (in
1720 // generation)
1721 bool _inFreeRange; // Indicates if we are in the
1722 // midst of a free run
1723 bool _freeRangeInFreeLists;
1724 // Often, we have just found
1725 // a free chunk and started
1726 // a new free range; we do not
1727 // eagerly remove this chunk from
1728 // the free lists unless there is
1729 // a possibility of coalescing.
1730 // When true, this flag indicates
1731 // that the _freeFinger below
1732 // points to a potentially free chunk
1733 // that may still be in the free lists
1734 bool _lastFreeRangeCoalesced;
1735 // free range contains chunks
1736 // coalesced
1737 bool _yield;
1738 // Whether sweeping should be
1739 // done with yields. For instance
1740 // when done by the foreground
1741 // collector we shouldn't yield.
1742 HeapWord* _freeFinger; // When _inFreeRange is set, the
1743 // pointer to the "left hand
1744 // chunk"
1745 size_t _freeRangeSize;
1746 // When _inFreeRange is set, this
1747 // indicates the accumulated size
1748 // of the "left hand chunk"
1749 NOT_PRODUCT(
1750 size_t _numObjectsFreed;
1751 size_t _numWordsFreed;
1752 size_t _numObjectsLive;
1753 size_t _numWordsLive;
1754 size_t _numObjectsAlreadyFree;
1755 size_t _numWordsAlreadyFree;
1756 FreeChunk* _last_fc;
1757 )
1758 private:
1759 // Code that is common to a free chunk or garbage when
1760 // encountered during sweeping.
1761 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1762 // Process a free chunk during sweeping.
1763 void do_already_free_chunk(FreeChunk *fc);
1764 // Work method called when processing an already free or a
1765 // freshly garbage chunk to do a lookahead and possibly a
1766 // premptive flush if crossing over _limit.
1767 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1768 // Process a garbage chunk during sweeping.
1769 size_t do_garbage_chunk(FreeChunk *fc);
1770 // Process a live chunk during sweeping.
1771 size_t do_live_chunk(FreeChunk* fc);
1772
1773 // Accessors.
1774 HeapWord* freeFinger() const { return _freeFinger; }
1775 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1776 bool inFreeRange() const { return _inFreeRange; }
1777 void set_inFreeRange(bool v) { _inFreeRange = v; }
1778 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1779 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1780 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1781 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1782
1783 // Initialize a free range.
1784 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1785 // Return this chunk to the free lists.
1786 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1787
1788 // Check if we should yield and do so when necessary.
1789 inline void do_yield_check(HeapWord* addr);
1790
1791 // Yield
1792 void do_yield_work(HeapWord* addr);
1793
1794 // Debugging/Printing
1795 void print_free_block_coalesced(FreeChunk* fc) const;
1796
1797 public:
1798 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1799 CMSBitMap* bitMap, bool should_yield);
1800 ~SweepClosure() PRODUCT_RETURN;
1801
1802 size_t do_blk_careful(HeapWord* addr);
1803 void print() const { print_on(tty); }
1804 void print_on(outputStream *st) const;
1805 };
1806
1807 // Closures related to weak references processing
1808
1809 // During CMS' weak reference processing, this is a
1810 // work-routine/closure used to complete transitive
1811 // marking of objects as live after a certain point
1812 // in which an initial set has been completely accumulated.
1813 // This closure is currently used both during the final
1814 // remark stop-world phase, as well as during the concurrent
1815 // precleaning of the discovered reference lists.
1816 class CMSDrainMarkingStackClosure: public VoidClosure {
1817 CMSCollector* _collector;
1818 MemRegion _span;
1819 CMSMarkStack* _mark_stack;
1820 CMSBitMap* _bit_map;
1821 CMSKeepAliveClosure* _keep_alive;
1822 bool _concurrent_precleaning;
1823 public:
1824 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1825 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1826 CMSKeepAliveClosure* keep_alive,
1827 bool cpc):
1828 _collector(collector),
1829 _span(span),
1830 _bit_map(bit_map),
1831 _mark_stack(mark_stack),
1832 _keep_alive(keep_alive),
1833 _concurrent_precleaning(cpc) {
1834 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1835 "Mismatch");
1836 }
1837
1838 void do_void();
1839 };
1840
1841 // A parallel version of CMSDrainMarkingStackClosure above.
1842 class CMSParDrainMarkingStackClosure: public VoidClosure {
1843 CMSCollector* _collector;
1844 MemRegion _span;
1845 OopTaskQueue* _work_queue;
1846 CMSBitMap* _bit_map;
1847 CMSInnerParMarkAndPushClosure _mark_and_push;
1848
1849 public:
1850 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1851 MemRegion span, CMSBitMap* bit_map,
1852 OopTaskQueue* work_queue):
1853 _collector(collector),
1854 _span(span),
1855 _bit_map(bit_map),
1856 _work_queue(work_queue),
1857 _mark_and_push(collector, span, bit_map, work_queue) { }
1858
1859 public:
1860 void trim_queue(uint max);
1861 void do_void();
1862 };
1863
1864 // Allow yielding or short-circuiting of reference list
1865 // prelceaning work.
1866 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1867 CMSCollector* _collector;
1868 void do_yield_work();
1869 public:
1870 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1871 _collector(collector) {}
1872 virtual bool should_return();
1873 };
1874
1875
1876 // Convenience class that locks free list locks for given CMS collector
1877 class FreelistLocker: public StackObj {
1878 private:
1879 CMSCollector* _collector;
1880 public:
1881 FreelistLocker(CMSCollector* collector):
1882 _collector(collector) {
1883 _collector->getFreelistLocks();
1884 }
1885
1886 ~FreelistLocker() {
1887 _collector->releaseFreelistLocks();
1888 }
1889 };
1890
1891 // Mark all dead objects in a given space.
1892 class MarkDeadObjectsClosure: public BlkClosure {
1893 const CMSCollector* _collector;
1894 const CompactibleFreeListSpace* _sp;
1895 CMSBitMap* _live_bit_map;
1896 CMSBitMap* _dead_bit_map;
1897 public:
1898 MarkDeadObjectsClosure(const CMSCollector* collector,
1899 const CompactibleFreeListSpace* sp,
1900 CMSBitMap *live_bit_map,
1901 CMSBitMap *dead_bit_map) :
1902 _collector(collector),
1903 _sp(sp),
1904 _live_bit_map(live_bit_map),
1905 _dead_bit_map(dead_bit_map) {}
1906 size_t do_blk(HeapWord* addr);
1907 };
1908
1909 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1910
1911 public:
1912 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1913 };
1914
1915
1916 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP