1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
27
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gSpaceCounters.hpp"
30 #include "gc_implementation/shared/gcStats.hpp"
31 #include "gc_implementation/shared/gcWhen.hpp"
32 #include "gc_implementation/shared/generationCounters.hpp"
33 #include "memory/freeBlockDictionary.hpp"
34 #include "memory/generation.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "runtime/virtualspace.hpp"
37 #include "services/memoryService.hpp"
38 #include "utilities/bitMap.inline.hpp"
39 #include "utilities/stack.inline.hpp"
40 #include "utilities/taskqueue.hpp"
41 #include "utilities/yieldingWorkgroup.hpp"
42
43 // ConcurrentMarkSweepGeneration is in support of a concurrent
44 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
45 // style. We assume, for now, that this generation is always the
46 // seniormost generation (modulo the PermGeneration), and for simplicity
47 // in the first implementation, that this generation is a single compactible
48 // space. Neither of these restrictions appears essential, and will be
49 // relaxed in the future when more time is available to implement the
50 // greater generality (and there's a need for it).
51 //
52 // Concurrent mode failures are currently handled by
53 // means of a sliding mark-compact.
54
55 class CMSAdaptiveSizePolicy;
56 class CMSConcMarkingTask;
57 class CMSGCAdaptivePolicyCounters;
58 class CMSTracer;
59 class ConcurrentGCTimer;
60 class ConcurrentMarkSweepGeneration;
61 class ConcurrentMarkSweepPolicy;
62 class ConcurrentMarkSweepThread;
63 class CompactibleFreeListSpace;
64 class FreeChunk;
65 class PromotionInfo;
66 class ScanMarkedObjectsAgainCarefullyClosure;
67 class SerialOldTracer;
68
69 // A generic CMS bit map. It's the basis for both the CMS marking bit map
70 // as well as for the mod union table (in each case only a subset of the
71 // methods are used). This is essentially a wrapper around the BitMap class,
72 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
73 // we have _shifter == 0. and for the mod union table we have
74 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
75 // XXX 64-bit issues in BitMap?
76 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
77 friend class VMStructs;
78
79 HeapWord* _bmStartWord; // base address of range covered by map
80 size_t _bmWordSize; // map size (in #HeapWords covered)
81 const int _shifter; // shifts to convert HeapWord to bit position
82 VirtualSpace _virtual_space; // underlying the bit map
83 BitMap _bm; // the bit map itself
84 public:
85 Mutex* const _lock; // mutex protecting _bm;
86
87 public:
88 // constructor
89 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
90
91 // allocates the actual storage for the map
92 bool allocate(MemRegion mr);
93 // field getter
94 Mutex* lock() const { return _lock; }
95 // locking verifier convenience function
96 void assert_locked() const PRODUCT_RETURN;
97
98 // inquiries
99 HeapWord* startWord() const { return _bmStartWord; }
100 size_t sizeInWords() const { return _bmWordSize; }
101 size_t sizeInBits() const { return _bm.size(); }
102 // the following is one past the last word in space
103 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
104
105 // reading marks
106 bool isMarked(HeapWord* addr) const;
107 bool par_isMarked(HeapWord* addr) const; // do not lock checks
108 bool isUnmarked(HeapWord* addr) const;
109 bool isAllClear() const;
110
111 // writing marks
112 void mark(HeapWord* addr);
113 // For marking by parallel GC threads;
114 // returns true if we did, false if another thread did
115 bool par_mark(HeapWord* addr);
116
117 void mark_range(MemRegion mr);
118 void par_mark_range(MemRegion mr);
119 void mark_large_range(MemRegion mr);
120 void par_mark_large_range(MemRegion mr);
121 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
122 void clear_range(MemRegion mr);
123 void par_clear_range(MemRegion mr);
124 void clear_large_range(MemRegion mr);
125 void par_clear_large_range(MemRegion mr);
126 void clear_all();
127 void clear_all_incrementally(); // Not yet implemented!!
128
129 NOT_PRODUCT(
130 // checks the memory region for validity
131 void region_invariant(MemRegion mr);
132 )
133
134 // iteration
135 void iterate(BitMapClosure* cl) {
136 _bm.iterate(cl);
137 }
138 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
139 void dirty_range_iterate_clear(MemRegionClosure* cl);
140 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
141
142 // auxiliary support for iteration
143 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
144 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
145 HeapWord* end_addr) const;
146 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
147 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
148 HeapWord* end_addr) const;
149 MemRegion getAndClearMarkedRegion(HeapWord* addr);
150 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
151 HeapWord* end_addr);
152
153 // conversion utilities
154 HeapWord* offsetToHeapWord(size_t offset) const;
155 size_t heapWordToOffset(HeapWord* addr) const;
156 size_t heapWordDiffToOffsetDiff(size_t diff) const;
157
158 // debugging
159 // is this address range covered by the bit-map?
160 NOT_PRODUCT(
161 bool covers(MemRegion mr) const;
162 bool covers(HeapWord* start, size_t size = 0) const;
163 )
164 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
165 };
166
167 // Represents a marking stack used by the CMS collector.
168 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
169 class CMSMarkStack: public CHeapObj<mtGC> {
170 //
171 friend class CMSCollector; // to get at expasion stats further below
172 //
173
174 VirtualSpace _virtual_space; // space for the stack
175 oop* _base; // bottom of stack
176 size_t _index; // one more than last occupied index
177 size_t _capacity; // max #elements
178 Mutex _par_lock; // an advisory lock used in case of parallel access
179 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run
180
181 protected:
182 size_t _hit_limit; // we hit max stack size limit
183 size_t _failed_double; // we failed expansion before hitting limit
184
185 public:
186 CMSMarkStack():
187 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
188 _hit_limit(0),
189 _failed_double(0) {}
190
191 bool allocate(size_t size);
192
193 size_t capacity() const { return _capacity; }
194
195 oop pop() {
196 if (!isEmpty()) {
197 return _base[--_index] ;
198 }
199 return NULL;
200 }
201
202 bool push(oop ptr) {
203 if (isFull()) {
204 return false;
205 } else {
206 _base[_index++] = ptr;
207 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
208 return true;
209 }
210 }
211
212 bool isEmpty() const { return _index == 0; }
213 bool isFull() const {
214 assert(_index <= _capacity, "buffer overflow");
215 return _index == _capacity;
216 }
217
218 size_t length() { return _index; }
219
220 // "Parallel versions" of some of the above
221 oop par_pop() {
222 // lock and pop
223 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
224 return pop();
225 }
226
227 bool par_push(oop ptr) {
228 // lock and push
229 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
230 return push(ptr);
231 }
232
233 // Forcibly reset the stack, losing all of its contents.
234 void reset() {
235 _index = 0;
236 }
237
238 // Expand the stack, typically in response to an overflow condition
239 void expand();
240
241 // Compute the least valued stack element.
242 oop least_value(HeapWord* low) {
243 oop least = (oop)low;
244 for (size_t i = 0; i < _index; i++) {
245 least = MIN2(least, _base[i]);
246 }
247 return least;
248 }
249
250 // Exposed here to allow stack expansion in || case
251 Mutex* par_lock() { return &_par_lock; }
252 };
253
254 class CardTableRS;
255 class CMSParGCThreadState;
256
257 class ModUnionClosure: public MemRegionClosure {
258 protected:
259 CMSBitMap* _t;
260 public:
261 ModUnionClosure(CMSBitMap* t): _t(t) { }
262 void do_MemRegion(MemRegion mr);
263 };
264
265 class ModUnionClosurePar: public ModUnionClosure {
266 public:
267 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
268 void do_MemRegion(MemRegion mr);
269 };
270
271 // Survivor Chunk Array in support of parallelization of
272 // Survivor Space rescan.
273 class ChunkArray: public CHeapObj<mtGC> {
274 size_t _index;
275 size_t _capacity;
276 size_t _overflows;
277 HeapWord** _array; // storage for array
278
279 public:
280 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
281 ChunkArray(HeapWord** a, size_t c):
282 _index(0), _capacity(c), _overflows(0), _array(a) {}
283
284 HeapWord** array() { return _array; }
285 void set_array(HeapWord** a) { _array = a; }
286
287 size_t capacity() { return _capacity; }
288 void set_capacity(size_t c) { _capacity = c; }
289
290 size_t end() {
291 assert(_index <= capacity(),
292 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
293 _index, _capacity));
294 return _index;
295 } // exclusive
296
297 HeapWord* nth(size_t n) {
298 assert(n < end(), "Out of bounds access");
299 return _array[n];
300 }
301
302 void reset() {
303 _index = 0;
304 if (_overflows > 0 && PrintCMSStatistics > 1) {
305 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
306 _capacity, _overflows);
307 }
308 _overflows = 0;
309 }
310
311 void record_sample(HeapWord* p, size_t sz) {
312 // For now we do not do anything with the size
313 if (_index < _capacity) {
314 _array[_index++] = p;
315 } else {
316 ++_overflows;
317 assert(_index == _capacity,
318 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
319 "): out of bounds at overflow#" SIZE_FORMAT,
320 _index, _capacity, _overflows));
321 }
322 }
323 };
324
325 //
326 // Timing, allocation and promotion statistics for gc scheduling and incremental
327 // mode pacing. Most statistics are exponential averages.
328 //
329 class CMSStats VALUE_OBJ_CLASS_SPEC {
330 private:
331 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
332
333 // The following are exponential averages with factor alpha:
334 // avg = (100 - alpha) * avg + alpha * cur_sample
335 //
336 // The durations measure: end_time[n] - start_time[n]
337 // The periods measure: start_time[n] - start_time[n-1]
338 //
339 // The cms period and duration include only concurrent collections; time spent
340 // in foreground cms collections due to System.gc() or because of a failure to
341 // keep up are not included.
342 //
343 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
344 // real value, but is used only after the first period. A value of 100 is
345 // used for the first sample so it gets the entire weight.
346 unsigned int _saved_alpha; // 0-100
347 unsigned int _gc0_alpha;
348 unsigned int _cms_alpha;
349
350 double _gc0_duration;
351 double _gc0_period;
352 size_t _gc0_promoted; // bytes promoted per gc0
353 double _cms_duration;
354 double _cms_duration_pre_sweep; // time from initiation to start of sweep
355 double _cms_duration_per_mb;
356 double _cms_period;
357 size_t _cms_allocated; // bytes of direct allocation per gc0 period
358
359 // Timers.
360 elapsedTimer _cms_timer;
361 TimeStamp _gc0_begin_time;
362 TimeStamp _cms_begin_time;
363 TimeStamp _cms_end_time;
364
365 // Snapshots of the amount used in the CMS generation.
366 size_t _cms_used_at_gc0_begin;
367 size_t _cms_used_at_gc0_end;
368 size_t _cms_used_at_cms_begin;
369
370 // Used to prevent the duty cycle from being reduced in the middle of a cms
371 // cycle.
372 bool _allow_duty_cycle_reduction;
373
374 enum {
375 _GC0_VALID = 0x1,
376 _CMS_VALID = 0x2,
377 _ALL_VALID = _GC0_VALID | _CMS_VALID
378 };
379
380 unsigned int _valid_bits;
381
382 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
383
384 protected:
385
386 // Return a duty cycle that avoids wild oscillations, by limiting the amount
387 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
388 // as a recommended value).
389 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
390 unsigned int new_duty_cycle);
391 unsigned int icms_update_duty_cycle_impl();
392
393 // In support of adjusting of cms trigger ratios based on history
394 // of concurrent mode failure.
395 double cms_free_adjustment_factor(size_t free) const;
396 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
397
398 public:
399 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
400 unsigned int alpha = CMSExpAvgFactor);
401
402 // Whether or not the statistics contain valid data; higher level statistics
403 // cannot be called until this returns true (they require at least one young
404 // gen and one cms cycle to have completed).
405 bool valid() const;
406
407 // Record statistics.
408 void record_gc0_begin();
409 void record_gc0_end(size_t cms_gen_bytes_used);
410 void record_cms_begin();
411 void record_cms_end();
412
413 // Allow management of the cms timer, which must be stopped/started around
414 // yield points.
415 elapsedTimer& cms_timer() { return _cms_timer; }
416 void start_cms_timer() { _cms_timer.start(); }
417 void stop_cms_timer() { _cms_timer.stop(); }
418
419 // Basic statistics; units are seconds or bytes.
420 double gc0_period() const { return _gc0_period; }
421 double gc0_duration() const { return _gc0_duration; }
422 size_t gc0_promoted() const { return _gc0_promoted; }
423 double cms_period() const { return _cms_period; }
424 double cms_duration() const { return _cms_duration; }
425 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
426 size_t cms_allocated() const { return _cms_allocated; }
427
428 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
429
430 // Seconds since the last background cms cycle began or ended.
431 double cms_time_since_begin() const;
432 double cms_time_since_end() const;
433
434 // Higher level statistics--caller must check that valid() returns true before
435 // calling.
436
437 // Returns bytes promoted per second of wall clock time.
438 double promotion_rate() const;
439
440 // Returns bytes directly allocated per second of wall clock time.
441 double cms_allocation_rate() const;
442
443 // Rate at which space in the cms generation is being consumed (sum of the
444 // above two).
445 double cms_consumption_rate() const;
446
447 // Returns an estimate of the number of seconds until the cms generation will
448 // fill up, assuming no collection work is done.
449 double time_until_cms_gen_full() const;
450
451 // Returns an estimate of the number of seconds remaining until
452 // the cms generation collection should start.
453 double time_until_cms_start() const;
454
455 // End of higher level statistics.
456
457 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
458 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
459
460 // Update the duty cycle and return the new value.
461 unsigned int icms_update_duty_cycle();
462
463 // Debugging.
464 void print_on(outputStream* st) const PRODUCT_RETURN;
465 void print() const { print_on(gclog_or_tty); }
466 };
467
468 // A closure related to weak references processing which
469 // we embed in the CMSCollector, since we need to pass
470 // it to the reference processor for secondary filtering
471 // of references based on reachability of referent;
472 // see role of _is_alive_non_header closure in the
473 // ReferenceProcessor class.
474 // For objects in the CMS generation, this closure checks
475 // if the object is "live" (reachable). Used in weak
476 // reference processing.
477 class CMSIsAliveClosure: public BoolObjectClosure {
478 const MemRegion _span;
479 const CMSBitMap* _bit_map;
480
481 friend class CMSCollector;
482 public:
483 CMSIsAliveClosure(MemRegion span,
484 CMSBitMap* bit_map):
485 _span(span),
486 _bit_map(bit_map) {
487 assert(!span.is_empty(), "Empty span could spell trouble");
488 }
489
490 void do_object(oop obj) {
491 assert(false, "not to be invoked");
492 }
493
494 bool do_object_b(oop obj);
495 };
496
497
498 // Implements AbstractRefProcTaskExecutor for CMS.
499 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
500 public:
501
502 CMSRefProcTaskExecutor(CMSCollector& collector)
503 : _collector(collector)
504 { }
505
506 // Executes a task using worker threads.
507 virtual void execute(ProcessTask& task);
508 virtual void execute(EnqueueTask& task);
509 private:
510 CMSCollector& _collector;
511 };
512
513
514 class CMSCollector: public CHeapObj<mtGC> {
515 friend class VMStructs;
516 friend class ConcurrentMarkSweepThread;
517 friend class ConcurrentMarkSweepGeneration;
518 friend class CompactibleFreeListSpace;
519 friend class CMSParMarkTask;
520 friend class CMSParInitialMarkTask;
521 friend class CMSParRemarkTask;
522 friend class CMSConcMarkingTask;
523 friend class CMSRefProcTaskProxy;
524 friend class CMSRefProcTaskExecutor;
525 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
526 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
527 friend class PushOrMarkClosure; // to access _restart_addr
528 friend class Par_PushOrMarkClosure; // to access _restart_addr
529 friend class MarkFromRootsClosure; // -- ditto --
530 // ... and for clearing cards
531 friend class Par_MarkFromRootsClosure; // to access _restart_addr
532 // ... and for clearing cards
533 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
534 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
535 friend class PushAndMarkVerifyClosure; // -- ditto --
536 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
537 friend class PushAndMarkClosure; // -- ditto --
538 friend class Par_PushAndMarkClosure; // -- ditto --
539 friend class CMSKeepAliveClosure; // -- ditto --
540 friend class CMSDrainMarkingStackClosure; // -- ditto --
541 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
542 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
543 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
544 friend class VM_CMS_Operation;
545 friend class VM_CMS_Initial_Mark;
546 friend class VM_CMS_Final_Remark;
547 friend class TraceCMSMemoryManagerStats;
548
549 private:
550 jlong _time_of_last_gc;
551 void update_time_of_last_gc(jlong now) {
552 _time_of_last_gc = now;
553 }
554
555 OopTaskQueueSet* _task_queues;
556
557 // Overflow list of grey objects, threaded through mark-word
558 // Manipulated with CAS in the parallel/multi-threaded case.
559 oop _overflow_list;
560 // The following array-pair keeps track of mark words
561 // displaced for accomodating overflow list above.
562 // This code will likely be revisited under RFE#4922830.
563 Stack<oop, mtGC> _preserved_oop_stack;
564 Stack<markOop, mtGC> _preserved_mark_stack;
565
566 int* _hash_seed;
567
568 // In support of multi-threaded concurrent phases
569 YieldingFlexibleWorkGang* _conc_workers;
570
571 // Performance Counters
572 CollectorCounters* _gc_counters;
573
574 // Initialization Errors
575 bool _completed_initialization;
576
577 // In support of ExplicitGCInvokesConcurrent
578 static bool _full_gc_requested;
579 static GCCause::Cause _full_gc_cause;
580 unsigned int _collection_count_start;
581
582 // Should we unload classes this concurrent cycle?
583 bool _should_unload_classes;
584 unsigned int _concurrent_cycles_since_last_unload;
585 unsigned int concurrent_cycles_since_last_unload() const {
586 return _concurrent_cycles_since_last_unload;
587 }
588 // Did we (allow) unload classes in the previous concurrent cycle?
589 bool unloaded_classes_last_cycle() const {
590 return concurrent_cycles_since_last_unload() == 0;
591 }
592 // Root scanning options for perm gen
593 int _roots_scanning_options;
594 int roots_scanning_options() const { return _roots_scanning_options; }
595 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
596 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
597
598 // Verification support
599 CMSBitMap _verification_mark_bm;
600 void verify_after_remark_work_1();
601 void verify_after_remark_work_2();
602
603 // true if any verification flag is on.
604 bool _verifying;
605 bool verifying() const { return _verifying; }
606 void set_verifying(bool v) { _verifying = v; }
607
608 // Collector policy
609 ConcurrentMarkSweepPolicy* _collector_policy;
610 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
611
612 // XXX Move these to CMSStats ??? FIX ME !!!
613 elapsedTimer _inter_sweep_timer; // time between sweeps
614 elapsedTimer _intra_sweep_timer; // time _in_ sweeps
615 // padded decaying average estimates of the above
616 AdaptivePaddedAverage _inter_sweep_estimate;
617 AdaptivePaddedAverage _intra_sweep_estimate;
618
619 CMSTracer* _gc_tracer_cm;
620 ConcurrentGCTimer* _gc_timer_cm;
621
622 bool _cms_start_registered;
623
624 GCHeapSummary _last_heap_summary;
625 PermGenSummary _last_perm_gen_summary;
626
627 void register_foreground_gc_start(GCCause::Cause cause);
628 void register_gc_start(GCCause::Cause cause);
629 void register_gc_end();
630 void save_heap_summary();
631 void report_heap_summary(GCWhen::Type when);
632
633 protected:
634 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
635 ConcurrentMarkSweepGeneration* _permGen; // perm gen
636 MemRegion _span; // span covering above two
637 CardTableRS* _ct; // card table
638
639 // CMS marking support structures
640 CMSBitMap _markBitMap;
641 CMSBitMap _modUnionTable;
642 CMSMarkStack _markStack;
643 CMSMarkStack _revisitStack; // used to keep track of klassKlass objects
644 // to revisit
645 CMSBitMap _perm_gen_verify_bit_map; // Mark bit map for perm gen verification support.
646
647 HeapWord* _restart_addr; // in support of marking stack overflow
648 void lower_restart_addr(HeapWord* low);
649
650 // Counters in support of marking stack / work queue overflow handling:
651 // a non-zero value indicates certain types of overflow events during
652 // the current CMS cycle and could lead to stack resizing efforts at
653 // an opportune future time.
654 size_t _ser_pmc_preclean_ovflw;
655 size_t _ser_pmc_remark_ovflw;
656 size_t _par_pmc_remark_ovflw;
657 size_t _ser_kac_preclean_ovflw;
658 size_t _ser_kac_ovflw;
659 size_t _par_kac_ovflw;
660 NOT_PRODUCT(ssize_t _num_par_pushes;)
661
662 // ("Weak") Reference processing support
663 ReferenceProcessor* _ref_processor;
664 CMSIsAliveClosure _is_alive_closure;
665 // keep this textually after _markBitMap and _span; c'tor dependency
666
667 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
668 ModUnionClosure _modUnionClosure;
669 ModUnionClosurePar _modUnionClosurePar;
670
671 // CMS abstract state machine
672 // initial_state: Idling
673 // next_state(Idling) = {Marking}
674 // next_state(Marking) = {Precleaning, Sweeping}
675 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
676 // next_state(AbortablePreclean) = {FinalMarking}
677 // next_state(FinalMarking) = {Sweeping}
678 // next_state(Sweeping) = {Resizing}
679 // next_state(Resizing) = {Resetting}
680 // next_state(Resetting) = {Idling}
681 // The numeric values below are chosen so that:
682 // . _collectorState <= Idling == post-sweep && pre-mark
683 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
684 // precleaning || abortablePrecleanb
685 public:
686 enum CollectorState {
687 Resizing = 0,
688 Resetting = 1,
689 Idling = 2,
690 InitialMarking = 3,
691 Marking = 4,
692 Precleaning = 5,
693 AbortablePreclean = 6,
694 FinalMarking = 7,
695 Sweeping = 8
696 };
697 protected:
698 static CollectorState _collectorState;
699
700 // State related to prologue/epilogue invocation for my generations
701 bool _between_prologue_and_epilogue;
702
703 // Signalling/State related to coordination between fore- and backgroud GC
704 // Note: When the baton has been passed from background GC to foreground GC,
705 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
706 static bool _foregroundGCIsActive; // true iff foreground collector is active or
707 // wants to go active
708 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
709 // yet passed the baton to the foreground GC
710
711 // Support for CMSScheduleRemark (abortable preclean)
712 bool _abort_preclean;
713 bool _start_sampling;
714
715 int _numYields;
716 size_t _numDirtyCards;
717 size_t _sweep_count;
718 // number of full gc's since the last concurrent gc.
719 uint _full_gcs_since_conc_gc;
720
721 // occupancy used for bootstrapping stats
722 double _bootstrap_occupancy;
723
724 // timer
725 elapsedTimer _timer;
726
727 // Timing, allocation and promotion statistics, used for scheduling.
728 CMSStats _stats;
729
730 // Allocation limits installed in the young gen, used only in
731 // CMSIncrementalMode. When an allocation in the young gen would cross one of
732 // these limits, the cms generation is notified and the cms thread is started
733 // or stopped, respectively.
734 HeapWord* _icms_start_limit;
735 HeapWord* _icms_stop_limit;
736
737 enum CMS_op_type {
738 CMS_op_checkpointRootsInitial,
739 CMS_op_checkpointRootsFinal
740 };
741
742 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
743 bool stop_world_and_do(CMS_op_type op);
744
745 OopTaskQueueSet* task_queues() { return _task_queues; }
746 int* hash_seed(int i) { return &_hash_seed[i]; }
747 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
748
749 // Support for parallelizing Eden rescan in CMS remark phase
750 void sample_eden(); // ... sample Eden space top
751
752 private:
753 // Support for parallelizing young gen rescan in CMS remark phase
754 Generation* _young_gen; // the younger gen
755 HeapWord** _top_addr; // ... Top of Eden
756 HeapWord** _end_addr; // ... End of Eden
757 Mutex* _eden_chunk_lock;
758 HeapWord** _eden_chunk_array; // ... Eden partitioning array
759 size_t _eden_chunk_index; // ... top (exclusive) of array
760 size_t _eden_chunk_capacity; // ... max entries in array
761
762 // Support for parallelizing survivor space rescan
763 HeapWord** _survivor_chunk_array;
764 size_t _survivor_chunk_index;
765 size_t _survivor_chunk_capacity;
766 size_t* _cursor;
767 ChunkArray* _survivor_plab_array;
768
769 // Support for marking stack overflow handling
770 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
771 bool par_take_from_overflow_list(size_t num,
772 OopTaskQueue* to_work_q,
773 int no_of_gc_threads);
774 void push_on_overflow_list(oop p);
775 void par_push_on_overflow_list(oop p);
776 // the following is, obviously, not, in general, "MT-stable"
777 bool overflow_list_is_empty() const;
778
779 void preserve_mark_if_necessary(oop p);
780 void par_preserve_mark_if_necessary(oop p);
781 void preserve_mark_work(oop p, markOop m);
782 void restore_preserved_marks_if_any();
783 NOT_PRODUCT(bool no_preserved_marks() const;)
784 // in support of testing overflow code
785 NOT_PRODUCT(int _overflow_counter;)
786 NOT_PRODUCT(bool simulate_overflow();) // sequential
787 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
788
789 // CMS work methods
790 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
791
792 // a return value of false indicates failure due to stack overflow
793 bool markFromRootsWork(bool asynch); // concurrent marking work
794
795 public: // FIX ME!!! only for testing
796 bool do_marking_st(bool asynch); // single-threaded marking
797 bool do_marking_mt(bool asynch); // multi-threaded marking
798
799 private:
800
801 // concurrent precleaning work
802 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
803 ScanMarkedObjectsAgainCarefullyClosure* cl);
804 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
805 ScanMarkedObjectsAgainCarefullyClosure* cl);
806 // Does precleaning work, returning a quantity indicative of
807 // the amount of "useful work" done.
808 size_t preclean_work(bool clean_refs, bool clean_survivors);
809 void abortable_preclean(); // Preclean while looking for possible abort
810 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
811 // Helper function for above; merge-sorts the per-thread plab samples
812 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
813 // Resets (i.e. clears) the per-thread plab sample vectors
814 void reset_survivor_plab_arrays();
815
816 // final (second) checkpoint work
817 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
818 bool init_mark_was_synchronous);
819 // work routine for parallel version of remark
820 void do_remark_parallel();
821 // work routine for non-parallel version of remark
822 void do_remark_non_parallel();
823 // reference processing work routine (during second checkpoint)
824 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
825
826 // concurrent sweeping work
827 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
828
829 // (concurrent) resetting of support data structures
830 void reset(bool asynch);
831
832 // Clear _expansion_cause fields of constituent generations
833 void clear_expansion_cause();
834
835 // An auxilliary method used to record the ends of
836 // used regions of each generation to limit the extent of sweep
837 void save_sweep_limits();
838
839 // Resize the generations included in the collector.
840 void compute_new_size();
841
842 // A work method used by foreground collection to determine
843 // what type of collection (compacting or not, continuing or fresh)
844 // it should do.
845 void decide_foreground_collection_type(bool clear_all_soft_refs,
846 bool* should_compact, bool* should_start_over);
847
848 // A work method used by the foreground collector to do
849 // a mark-sweep-compact.
850 void do_compaction_work(bool clear_all_soft_refs);
851
852 // A work method used by the foreground collector to do
853 // a mark-sweep, after taking over from a possibly on-going
854 // concurrent mark-sweep collection.
855 void do_mark_sweep_work(bool clear_all_soft_refs,
856 CollectorState first_state, bool should_start_over);
857
858 // Work methods for reporting concurrent mode interruption or failure
859 bool is_external_interruption();
860 void report_concurrent_mode_interruption();
861
862 // If the backgrould GC is active, acquire control from the background
863 // GC and do the collection.
864 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
865
866 // For synchronizing passing of control from background to foreground
867 // GC. waitForForegroundGC() is called by the background
868 // collector. It if had to wait for a foreground collection,
869 // it returns true and the background collection should assume
870 // that the collection was finished by the foreground
871 // collector.
872 bool waitForForegroundGC();
873
874 // Incremental mode triggering: recompute the icms duty cycle and set the
875 // allocation limits in the young gen.
876 void icms_update_allocation_limits();
877
878 size_t block_size_using_printezis_bits(HeapWord* addr) const;
879 size_t block_size_if_printezis_bits(HeapWord* addr) const;
880 HeapWord* next_card_start_after_block(HeapWord* addr) const;
881
882 void setup_cms_unloading_and_verification_state();
883 public:
884 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
885 ConcurrentMarkSweepGeneration* permGen,
886 CardTableRS* ct,
887 ConcurrentMarkSweepPolicy* cp);
888 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
889
890 ReferenceProcessor* ref_processor() { return _ref_processor; }
891 void ref_processor_init();
892
893 Mutex* bitMapLock() const { return _markBitMap.lock(); }
894 static CollectorState abstract_state() { return _collectorState; }
895
896 bool should_abort_preclean() const; // Whether preclean should be aborted.
897 size_t get_eden_used() const;
898 size_t get_eden_capacity() const;
899
900 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
901
902 // locking checks
903 NOT_PRODUCT(static bool have_cms_token();)
904
905 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
906 bool shouldConcurrentCollect();
907
908 void collect(bool full,
909 bool clear_all_soft_refs,
910 size_t size,
911 bool tlab);
912 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
913 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
914
915 // In support of ExplicitGCInvokesConcurrent
916 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
917 // Should we unload classes in a particular concurrent cycle?
918 bool should_unload_classes() const {
919 return _should_unload_classes;
920 }
921 bool update_should_unload_classes();
922
923 void direct_allocated(HeapWord* start, size_t size);
924
925 // Object is dead if not marked and current phase is sweeping.
926 bool is_dead_obj(oop obj) const;
927
928 // After a promotion (of "start"), do any necessary marking.
929 // If "par", then it's being done by a parallel GC thread.
930 // The last two args indicate if we need precise marking
931 // and if so the size of the object so it can be dirtied
932 // in its entirety.
933 void promoted(bool par, HeapWord* start,
934 bool is_obj_array, size_t obj_size);
935
936 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
937 size_t word_size);
938
939 void getFreelistLocks() const;
940 void releaseFreelistLocks() const;
941 bool haveFreelistLocks() const;
942
943 // GC prologue and epilogue
944 void gc_prologue(bool full);
945 void gc_epilogue(bool full);
946
947 jlong time_of_last_gc(jlong now) {
948 if (_collectorState <= Idling) {
949 // gc not in progress
950 return _time_of_last_gc;
951 } else {
952 // collection in progress
953 return now;
954 }
955 }
956
957 // Support for parallel remark of survivor space
958 void* get_data_recorder(int thr_num);
959 void sample_eden_chunk();
960
961 CMSBitMap* markBitMap() { return &_markBitMap; }
962 void directAllocated(HeapWord* start, size_t size);
963
964 // main CMS steps and related support
965 void checkpointRootsInitial(bool asynch);
966 bool markFromRoots(bool asynch); // a return value of false indicates failure
967 // due to stack overflow
968 void preclean();
969 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
970 bool init_mark_was_synchronous);
971 void sweep(bool asynch);
972
973 // Check that the currently executing thread is the expected
974 // one (foreground collector or background collector).
975 static void check_correct_thread_executing() PRODUCT_RETURN;
976 // XXXPERM void print_statistics() PRODUCT_RETURN;
977
978 bool is_cms_reachable(HeapWord* addr);
979
980 // Performance Counter Support
981 CollectorCounters* counters() { return _gc_counters; }
982
983 // timer stuff
984 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
985 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
986 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
987 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
988
989 int yields() { return _numYields; }
990 void resetYields() { _numYields = 0; }
991 void incrementYields() { _numYields++; }
992 void resetNumDirtyCards() { _numDirtyCards = 0; }
993 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
994 size_t numDirtyCards() { return _numDirtyCards; }
995
996 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
997 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
998 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
999 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
1000 size_t sweep_count() const { return _sweep_count; }
1001 void increment_sweep_count() { _sweep_count++; }
1002
1003 // Timers/stats for gc scheduling and incremental mode pacing.
1004 CMSStats& stats() { return _stats; }
1005
1006 // Convenience methods that check whether CMSIncrementalMode is enabled and
1007 // forward to the corresponding methods in ConcurrentMarkSweepThread.
1008 static void start_icms();
1009 static void stop_icms(); // Called at the end of the cms cycle.
1010 static void disable_icms(); // Called before a foreground collection.
1011 static void enable_icms(); // Called after a foreground collection.
1012 void icms_wait(); // Called at yield points.
1013
1014 // Adaptive size policy
1015 CMSAdaptiveSizePolicy* size_policy();
1016 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1017
1018 // debugging
1019 void verify();
1020 bool verify_after_remark();
1021 void verify_ok_to_terminate() const PRODUCT_RETURN;
1022 void verify_work_stacks_empty() const PRODUCT_RETURN;
1023 void verify_overflow_empty() const PRODUCT_RETURN;
1024
1025 // convenience methods in support of debugging
1026 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1027 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1028
1029 // accessors
1030 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1031 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1032
1033 // Get the bit map with a perm gen "deadness" information.
1034 CMSBitMap* perm_gen_verify_bit_map() { return &_perm_gen_verify_bit_map; }
1035
1036 // Initialization errors
1037 bool completed_initialization() { return _completed_initialization; }
1038
1039 void print_eden_and_survivor_chunk_arrays();
1040 };
1041
1042 class CMSExpansionCause : public AllStatic {
1043 public:
1044 enum Cause {
1045 _no_expansion,
1046 _satisfy_free_ratio,
1047 _satisfy_promotion,
1048 _satisfy_allocation,
1049 _allocate_par_lab,
1050 _allocate_par_spooling_space,
1051 _adaptive_size_policy
1052 };
1053 // Return a string describing the cause of the expansion.
1054 static const char* to_string(CMSExpansionCause::Cause cause);
1055 };
1056
1057 class ConcurrentMarkSweepGeneration: public CardGeneration {
1058 friend class VMStructs;
1059 friend class ConcurrentMarkSweepThread;
1060 friend class ConcurrentMarkSweep;
1061 friend class CMSCollector;
1062 protected:
1063 static CMSCollector* _collector; // the collector that collects us
1064 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1065
1066 // Performance Counters
1067 GenerationCounters* _gen_counters;
1068 GSpaceCounters* _space_counters;
1069
1070 // Words directly allocated, used by CMSStats.
1071 size_t _direct_allocated_words;
1072
1073 // Non-product stat counters
1074 NOT_PRODUCT(
1075 size_t _numObjectsPromoted;
1076 size_t _numWordsPromoted;
1077 size_t _numObjectsAllocated;
1078 size_t _numWordsAllocated;
1079 )
1080
1081 // Used for sizing decisions
1082 bool _incremental_collection_failed;
1083 bool incremental_collection_failed() {
1084 return _incremental_collection_failed;
1085 }
1086 void set_incremental_collection_failed() {
1087 _incremental_collection_failed = true;
1088 }
1089 void clear_incremental_collection_failed() {
1090 _incremental_collection_failed = false;
1091 }
1092
1093 // accessors
1094 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1095 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1096
1097 private:
1098 // For parallel young-gen GC support.
1099 CMSParGCThreadState** _par_gc_thread_states;
1100
1101 // Reason generation was expanded
1102 CMSExpansionCause::Cause _expansion_cause;
1103
1104 // In support of MinChunkSize being larger than min object size
1105 const double _dilatation_factor;
1106
1107 enum CollectionTypes {
1108 Concurrent_collection_type = 0,
1109 MS_foreground_collection_type = 1,
1110 MSC_foreground_collection_type = 2,
1111 Unknown_collection_type = 3
1112 };
1113
1114 CollectionTypes _debug_collection_type;
1115
1116 // Fraction of current occupancy at which to start a CMS collection which
1117 // will collect this generation (at least).
1118 double _initiating_occupancy;
1119
1120 protected:
1121 // Shrink generation by specified size (returns false if unable to shrink)
1122 virtual void shrink_by(size_t bytes);
1123
1124 // Update statistics for GC
1125 virtual void update_gc_stats(int level, bool full);
1126
1127 // Maximum available space in the generation (including uncommitted)
1128 // space.
1129 size_t max_available() const;
1130
1131 // getter and initializer for _initiating_occupancy field.
1132 double initiating_occupancy() const { return _initiating_occupancy; }
1133 void init_initiating_occupancy(intx io, intx tr);
1134
1135 public:
1136 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1137 int level, CardTableRS* ct,
1138 bool use_adaptive_freelists,
1139 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1140
1141 // Accessors
1142 CMSCollector* collector() const { return _collector; }
1143 static void set_collector(CMSCollector* collector) {
1144 assert(_collector == NULL, "already set");
1145 _collector = collector;
1146 }
1147 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1148
1149 Mutex* freelistLock() const;
1150
1151 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1152
1153 // Adaptive size policy
1154 CMSAdaptiveSizePolicy* size_policy();
1155
1156 bool refs_discovery_is_atomic() const { return false; }
1157 bool refs_discovery_is_mt() const {
1158 // Note: CMS does MT-discovery during the parallel-remark
1159 // phases. Use ReferenceProcessorMTMutator to make refs
1160 // discovery MT-safe during such phases or other parallel
1161 // discovery phases in the future. This may all go away
1162 // if/when we decide that refs discovery is sufficiently
1163 // rare that the cost of the CAS's involved is in the
1164 // noise. That's a measurement that should be done, and
1165 // the code simplified if that turns out to be the case.
1166 return ConcGCThreads > 1;
1167 }
1168
1169 // Override
1170 virtual void ref_processor_init();
1171
1172 // Grow generation by specified size (returns false if unable to grow)
1173 bool grow_by(size_t bytes);
1174 // Grow generation to reserved size.
1175 bool grow_to_reserved();
1176
1177 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1178
1179 // Space enquiries
1180 size_t capacity() const;
1181 size_t used() const;
1182 size_t free() const;
1183 double occupancy() const { return ((double)used())/((double)capacity()); }
1184 size_t contiguous_available() const;
1185 size_t unsafe_max_alloc_nogc() const;
1186
1187 // over-rides
1188 MemRegion used_region() const;
1189 MemRegion used_region_at_save_marks() const;
1190
1191 // Does a "full" (forced) collection invoked on this generation collect
1192 // all younger generations as well? Note that the second conjunct is a
1193 // hack to allow the collection of the younger gen first if the flag is
1194 // set. This is better than using th policy's should_collect_gen0_first()
1195 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1196 virtual bool full_collects_younger_generations() const {
1197 return UseCMSCompactAtFullCollection && !CollectGen0First;
1198 }
1199
1200 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1201
1202 // Support for compaction
1203 CompactibleSpace* first_compaction_space() const;
1204 // Adjust quantites in the generation affected by
1205 // the compaction.
1206 void reset_after_compaction();
1207
1208 // Allocation support
1209 HeapWord* allocate(size_t size, bool tlab);
1210 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1211 oop promote(oop obj, size_t obj_size);
1212 HeapWord* par_allocate(size_t size, bool tlab) {
1213 return allocate(size, tlab);
1214 }
1215
1216 // Incremental mode triggering.
1217 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1218 size_t word_size);
1219
1220 // Used by CMSStats to track direct allocation. The value is sampled and
1221 // reset after each young gen collection.
1222 size_t direct_allocated_words() const { return _direct_allocated_words; }
1223 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1224
1225 // Overrides for parallel promotion.
1226 virtual oop par_promote(int thread_num,
1227 oop obj, markOop m, size_t word_sz);
1228 // This one should not be called for CMS.
1229 virtual void par_promote_alloc_undo(int thread_num,
1230 HeapWord* obj, size_t word_sz);
1231 virtual void par_promote_alloc_done(int thread_num);
1232 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1233
1234 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1235
1236 // Inform this (non-young) generation that a promotion failure was
1237 // encountered during a collection of a younger generation that
1238 // promotes into this generation.
1239 virtual void promotion_failure_occurred();
1240
1241 bool should_collect(bool full, size_t size, bool tlab);
1242 virtual bool should_concurrent_collect() const;
1243 virtual bool is_too_full() const;
1244 void collect(bool full,
1245 bool clear_all_soft_refs,
1246 size_t size,
1247 bool tlab);
1248
1249 HeapWord* expand_and_allocate(size_t word_size,
1250 bool tlab,
1251 bool parallel = false);
1252
1253 // GC prologue and epilogue
1254 void gc_prologue(bool full);
1255 void gc_prologue_work(bool full, bool registerClosure,
1256 ModUnionClosure* modUnionClosure);
1257 void gc_epilogue(bool full);
1258 void gc_epilogue_work(bool full);
1259
1260 // Time since last GC of this generation
1261 jlong time_of_last_gc(jlong now) {
1262 return collector()->time_of_last_gc(now);
1263 }
1264 void update_time_of_last_gc(jlong now) {
1265 collector()-> update_time_of_last_gc(now);
1266 }
1267
1268 // Allocation failure
1269 void expand(size_t bytes, size_t expand_bytes,
1270 CMSExpansionCause::Cause cause);
1271 virtual bool expand(size_t bytes, size_t expand_bytes);
1272 void shrink(size_t bytes);
1273 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1274 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1275
1276 // Iteration support and related enquiries
1277 void save_marks();
1278 bool no_allocs_since_save_marks();
1279 void object_iterate_since_last_GC(ObjectClosure* cl);
1280 void younger_refs_iterate(OopsInGenClosure* cl);
1281
1282 // Iteration support specific to CMS generations
1283 void save_sweep_limit();
1284
1285 // More iteration support
1286 virtual void oop_iterate(MemRegion mr, OopClosure* cl);
1287 virtual void oop_iterate(OopClosure* cl);
1288 virtual void safe_object_iterate(ObjectClosure* cl);
1289 virtual void object_iterate(ObjectClosure* cl);
1290
1291 // Need to declare the full complement of closures, whether we'll
1292 // override them or not, or get message from the compiler:
1293 // oop_since_save_marks_iterate_nv hides virtual function...
1294 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1295 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1296 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1297
1298 // Smart allocation XXX -- move to CFLSpace?
1299 void setNearLargestChunk();
1300 bool isNearLargestChunk(HeapWord* addr);
1301
1302 // Get the chunk at the end of the space. Delagates to
1303 // the space.
1304 FreeChunk* find_chunk_at_end();
1305
1306 // Overriding of unused functionality (sharing not yet supported with CMS)
1307 void pre_adjust_pointers();
1308 void post_compact();
1309
1310 // Debugging
1311 void prepare_for_verify();
1312 void verify();
1313 void print_statistics() PRODUCT_RETURN;
1314
1315 // Performance Counters support
1316 virtual void update_counters();
1317 virtual void update_counters(size_t used);
1318 void initialize_performance_counters();
1319 CollectorCounters* counters() { return collector()->counters(); }
1320
1321 // Support for parallel remark of survivor space
1322 void* get_data_recorder(int thr_num) {
1323 //Delegate to collector
1324 return collector()->get_data_recorder(thr_num);
1325 }
1326 void sample_eden_chunk() {
1327 //Delegate to collector
1328 return collector()->sample_eden_chunk();
1329 }
1330
1331 // Printing
1332 const char* name() const;
1333 virtual const char* short_name() const { return "CMS"; }
1334 void print() const;
1335 void printOccupancy(const char* s);
1336 bool must_be_youngest() const { return false; }
1337 bool must_be_oldest() const { return true; }
1338
1339 void compute_new_size();
1340
1341 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1342 void rotate_debug_collection_type();
1343 };
1344
1345 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1346
1347 // Return the size policy from the heap's collector
1348 // policy casted to CMSAdaptiveSizePolicy*.
1349 CMSAdaptiveSizePolicy* cms_size_policy() const;
1350
1351 // Resize the generation based on the adaptive size
1352 // policy.
1353 void resize(size_t cur_promo, size_t desired_promo);
1354
1355 // Return the GC counters from the collector policy
1356 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1357
1358 virtual void shrink_by(size_t bytes);
1359
1360 public:
1361 virtual void compute_new_size();
1362 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1363 int level, CardTableRS* ct,
1364 bool use_adaptive_freelists,
1365 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1366 dictionaryChoice) :
1367 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1368 use_adaptive_freelists, dictionaryChoice) {}
1369
1370 virtual const char* short_name() const { return "ASCMS"; }
1371 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1372
1373 virtual void update_counters();
1374 virtual void update_counters(size_t used);
1375 };
1376
1377 //
1378 // Closures of various sorts used by CMS to accomplish its work
1379 //
1380
1381 // This closure is used to check that a certain set of oops is empty.
1382 class FalseClosure: public OopClosure {
1383 public:
1384 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1385 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1386 };
1387
1388 // This closure is used to do concurrent marking from the roots
1389 // following the first checkpoint.
1390 class MarkFromRootsClosure: public BitMapClosure {
1391 CMSCollector* _collector;
1392 MemRegion _span;
1393 CMSBitMap* _bitMap;
1394 CMSBitMap* _mut;
1395 CMSMarkStack* _markStack;
1396 CMSMarkStack* _revisitStack;
1397 bool _yield;
1398 int _skipBits;
1399 HeapWord* _finger;
1400 HeapWord* _threshold;
1401 DEBUG_ONLY(bool _verifying;)
1402
1403 public:
1404 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1405 CMSBitMap* bitMap,
1406 CMSMarkStack* markStack,
1407 CMSMarkStack* revisitStack,
1408 bool should_yield, bool verifying = false);
1409 bool do_bit(size_t offset);
1410 void reset(HeapWord* addr);
1411 inline void do_yield_check();
1412
1413 private:
1414 void scanOopsInOop(HeapWord* ptr);
1415 void do_yield_work();
1416 };
1417
1418 // This closure is used to do concurrent multi-threaded
1419 // marking from the roots following the first checkpoint.
1420 // XXX This should really be a subclass of The serial version
1421 // above, but i have not had the time to refactor things cleanly.
1422 // That willbe done for Dolphin.
1423 class Par_MarkFromRootsClosure: public BitMapClosure {
1424 CMSCollector* _collector;
1425 MemRegion _whole_span;
1426 MemRegion _span;
1427 CMSBitMap* _bit_map;
1428 CMSBitMap* _mut;
1429 OopTaskQueue* _work_queue;
1430 CMSMarkStack* _overflow_stack;
1431 CMSMarkStack* _revisit_stack;
1432 bool _yield;
1433 int _skip_bits;
1434 HeapWord* _finger;
1435 HeapWord* _threshold;
1436 CMSConcMarkingTask* _task;
1437 public:
1438 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1439 MemRegion span,
1440 CMSBitMap* bit_map,
1441 OopTaskQueue* work_queue,
1442 CMSMarkStack* overflow_stack,
1443 CMSMarkStack* revisit_stack,
1444 bool should_yield);
1445 bool do_bit(size_t offset);
1446 inline void do_yield_check();
1447
1448 private:
1449 void scan_oops_in_oop(HeapWord* ptr);
1450 void do_yield_work();
1451 bool get_work_from_overflow_stack();
1452 };
1453
1454 // The following closures are used to do certain kinds of verification of
1455 // CMS marking.
1456 class PushAndMarkVerifyClosure: public OopClosure {
1457 CMSCollector* _collector;
1458 MemRegion _span;
1459 CMSBitMap* _verification_bm;
1460 CMSBitMap* _cms_bm;
1461 CMSMarkStack* _mark_stack;
1462 protected:
1463 void do_oop(oop p);
1464 template <class T> inline void do_oop_work(T *p) {
1465 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
1466 do_oop(obj);
1467 }
1468 public:
1469 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1470 MemRegion span,
1471 CMSBitMap* verification_bm,
1472 CMSBitMap* cms_bm,
1473 CMSMarkStack* mark_stack);
1474 void do_oop(oop* p);
1475 void do_oop(narrowOop* p);
1476 // Deal with a stack overflow condition
1477 void handle_stack_overflow(HeapWord* lost);
1478 };
1479
1480 class MarkFromRootsVerifyClosure: public BitMapClosure {
1481 CMSCollector* _collector;
1482 MemRegion _span;
1483 CMSBitMap* _verification_bm;
1484 CMSBitMap* _cms_bm;
1485 CMSMarkStack* _mark_stack;
1486 HeapWord* _finger;
1487 PushAndMarkVerifyClosure _pam_verify_closure;
1488 public:
1489 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1490 CMSBitMap* verification_bm,
1491 CMSBitMap* cms_bm,
1492 CMSMarkStack* mark_stack);
1493 bool do_bit(size_t offset);
1494 void reset(HeapWord* addr);
1495 };
1496
1497
1498 // This closure is used to check that a certain set of bits is
1499 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1500 class FalseBitMapClosure: public BitMapClosure {
1501 public:
1502 bool do_bit(size_t offset) {
1503 guarantee(false, "Should not have a 1 bit");
1504 return true;
1505 }
1506 };
1507
1508 // This closure is used during the second checkpointing phase
1509 // to rescan the marked objects on the dirty cards in the mod
1510 // union table and the card table proper. It's invoked via
1511 // MarkFromDirtyCardsClosure below. It uses either
1512 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1513 // declared in genOopClosures.hpp to accomplish some of its work.
1514 // In the parallel case the bitMap is shared, so access to
1515 // it needs to be suitably synchronized for updates by embedded
1516 // closures that update it; however, this closure itself only
1517 // reads the bit_map and because it is idempotent, is immune to
1518 // reading stale values.
1519 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1520 #ifdef ASSERT
1521 CMSCollector* _collector;
1522 MemRegion _span;
1523 union {
1524 CMSMarkStack* _mark_stack;
1525 OopTaskQueue* _work_queue;
1526 };
1527 #endif // ASSERT
1528 bool _parallel;
1529 CMSBitMap* _bit_map;
1530 union {
1531 MarkRefsIntoAndScanClosure* _scan_closure;
1532 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1533 };
1534
1535 public:
1536 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1537 MemRegion span,
1538 ReferenceProcessor* rp,
1539 CMSBitMap* bit_map,
1540 CMSMarkStack* mark_stack,
1541 CMSMarkStack* revisit_stack,
1542 MarkRefsIntoAndScanClosure* cl):
1543 #ifdef ASSERT
1544 _collector(collector),
1545 _span(span),
1546 _mark_stack(mark_stack),
1547 #endif // ASSERT
1548 _parallel(false),
1549 _bit_map(bit_map),
1550 _scan_closure(cl) { }
1551
1552 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1553 MemRegion span,
1554 ReferenceProcessor* rp,
1555 CMSBitMap* bit_map,
1556 OopTaskQueue* work_queue,
1557 CMSMarkStack* revisit_stack,
1558 Par_MarkRefsIntoAndScanClosure* cl):
1559 #ifdef ASSERT
1560 _collector(collector),
1561 _span(span),
1562 _work_queue(work_queue),
1563 #endif // ASSERT
1564 _parallel(true),
1565 _bit_map(bit_map),
1566 _par_scan_closure(cl) { }
1567
1568 void do_object(oop obj) {
1569 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1570 }
1571 bool do_object_b(oop obj) {
1572 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1573 return false;
1574 }
1575 bool do_object_bm(oop p, MemRegion mr);
1576 };
1577
1578 // This closure is used during the second checkpointing phase
1579 // to rescan the marked objects on the dirty cards in the mod
1580 // union table and the card table proper. It invokes
1581 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1582 // In the parallel case, the bit map is shared and requires
1583 // synchronized access.
1584 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1585 CompactibleFreeListSpace* _space;
1586 ScanMarkedObjectsAgainClosure _scan_cl;
1587 size_t _num_dirty_cards;
1588
1589 public:
1590 MarkFromDirtyCardsClosure(CMSCollector* collector,
1591 MemRegion span,
1592 CompactibleFreeListSpace* space,
1593 CMSBitMap* bit_map,
1594 CMSMarkStack* mark_stack,
1595 CMSMarkStack* revisit_stack,
1596 MarkRefsIntoAndScanClosure* cl):
1597 _space(space),
1598 _num_dirty_cards(0),
1599 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1600 mark_stack, revisit_stack, cl) { }
1601
1602 MarkFromDirtyCardsClosure(CMSCollector* collector,
1603 MemRegion span,
1604 CompactibleFreeListSpace* space,
1605 CMSBitMap* bit_map,
1606 OopTaskQueue* work_queue,
1607 CMSMarkStack* revisit_stack,
1608 Par_MarkRefsIntoAndScanClosure* cl):
1609 _space(space),
1610 _num_dirty_cards(0),
1611 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1612 work_queue, revisit_stack, cl) { }
1613
1614 void do_MemRegion(MemRegion mr);
1615 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1616 size_t num_dirty_cards() { return _num_dirty_cards; }
1617 };
1618
1619 // This closure is used in the non-product build to check
1620 // that there are no MemRegions with a certain property.
1621 class FalseMemRegionClosure: public MemRegionClosure {
1622 void do_MemRegion(MemRegion mr) {
1623 guarantee(!mr.is_empty(), "Shouldn't be empty");
1624 guarantee(false, "Should never be here");
1625 }
1626 };
1627
1628 // This closure is used during the precleaning phase
1629 // to "carefully" rescan marked objects on dirty cards.
1630 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1631 // to accomplish some of its work.
1632 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1633 CMSCollector* _collector;
1634 MemRegion _span;
1635 bool _yield;
1636 Mutex* _freelistLock;
1637 CMSBitMap* _bitMap;
1638 CMSMarkStack* _markStack;
1639 MarkRefsIntoAndScanClosure* _scanningClosure;
1640
1641 public:
1642 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1643 MemRegion span,
1644 CMSBitMap* bitMap,
1645 CMSMarkStack* markStack,
1646 CMSMarkStack* revisitStack,
1647 MarkRefsIntoAndScanClosure* cl,
1648 bool should_yield):
1649 _collector(collector),
1650 _span(span),
1651 _yield(should_yield),
1652 _bitMap(bitMap),
1653 _markStack(markStack),
1654 _scanningClosure(cl) {
1655 }
1656
1657 void do_object(oop p) {
1658 guarantee(false, "call do_object_careful instead");
1659 }
1660
1661 size_t do_object_careful(oop p) {
1662 guarantee(false, "Unexpected caller");
1663 return 0;
1664 }
1665
1666 size_t do_object_careful_m(oop p, MemRegion mr);
1667
1668 void setFreelistLock(Mutex* m) {
1669 _freelistLock = m;
1670 _scanningClosure->set_freelistLock(m);
1671 }
1672
1673 private:
1674 inline bool do_yield_check();
1675
1676 void do_yield_work();
1677 };
1678
1679 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1680 CMSCollector* _collector;
1681 MemRegion _span;
1682 bool _yield;
1683 CMSBitMap* _bit_map;
1684 CMSMarkStack* _mark_stack;
1685 PushAndMarkClosure* _scanning_closure;
1686 unsigned int _before_count;
1687
1688 public:
1689 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1690 MemRegion span,
1691 CMSBitMap* bit_map,
1692 CMSMarkStack* mark_stack,
1693 PushAndMarkClosure* cl,
1694 unsigned int before_count,
1695 bool should_yield):
1696 _collector(collector),
1697 _span(span),
1698 _yield(should_yield),
1699 _bit_map(bit_map),
1700 _mark_stack(mark_stack),
1701 _scanning_closure(cl),
1702 _before_count(before_count)
1703 { }
1704
1705 void do_object(oop p) {
1706 guarantee(false, "call do_object_careful instead");
1707 }
1708
1709 size_t do_object_careful(oop p);
1710
1711 size_t do_object_careful_m(oop p, MemRegion mr) {
1712 guarantee(false, "Unexpected caller");
1713 return 0;
1714 }
1715
1716 private:
1717 inline void do_yield_check();
1718 void do_yield_work();
1719 };
1720
1721 // This closure is used to accomplish the sweeping work
1722 // after the second checkpoint but before the concurrent reset
1723 // phase.
1724 //
1725 // Terminology
1726 // left hand chunk (LHC) - block of one or more chunks currently being
1727 // coalesced. The LHC is available for coalescing with a new chunk.
1728 // right hand chunk (RHC) - block that is currently being swept that is
1729 // free or garbage that can be coalesced with the LHC.
1730 // _inFreeRange is true if there is currently a LHC
1731 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1732 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1733 // _freeFinger is the address of the current LHC
1734 class SweepClosure: public BlkClosureCareful {
1735 CMSCollector* _collector; // collector doing the work
1736 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1737 CompactibleFreeListSpace* _sp; // Space being swept
1738 HeapWord* _limit;// the address at or above which the sweep should stop
1739 // because we do not expect newly garbage blocks
1740 // eligible for sweeping past that address.
1741 Mutex* _freelistLock; // Free list lock (in space)
1742 CMSBitMap* _bitMap; // Marking bit map (in
1743 // generation)
1744 bool _inFreeRange; // Indicates if we are in the
1745 // midst of a free run
1746 bool _freeRangeInFreeLists;
1747 // Often, we have just found
1748 // a free chunk and started
1749 // a new free range; we do not
1750 // eagerly remove this chunk from
1751 // the free lists unless there is
1752 // a possibility of coalescing.
1753 // When true, this flag indicates
1754 // that the _freeFinger below
1755 // points to a potentially free chunk
1756 // that may still be in the free lists
1757 bool _lastFreeRangeCoalesced;
1758 // free range contains chunks
1759 // coalesced
1760 bool _yield;
1761 // Whether sweeping should be
1762 // done with yields. For instance
1763 // when done by the foreground
1764 // collector we shouldn't yield.
1765 HeapWord* _freeFinger; // When _inFreeRange is set, the
1766 // pointer to the "left hand
1767 // chunk"
1768 size_t _freeRangeSize;
1769 // When _inFreeRange is set, this
1770 // indicates the accumulated size
1771 // of the "left hand chunk"
1772 NOT_PRODUCT(
1773 size_t _numObjectsFreed;
1774 size_t _numWordsFreed;
1775 size_t _numObjectsLive;
1776 size_t _numWordsLive;
1777 size_t _numObjectsAlreadyFree;
1778 size_t _numWordsAlreadyFree;
1779 FreeChunk* _last_fc;
1780 )
1781 private:
1782 // Code that is common to a free chunk or garbage when
1783 // encountered during sweeping.
1784 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1785 // Process a free chunk during sweeping.
1786 void do_already_free_chunk(FreeChunk *fc);
1787 // Work method called when processing an already free or a
1788 // freshly garbage chunk to do a lookahead and possibly a
1789 // premptive flush if crossing over _limit.
1790 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1791 // Process a garbage chunk during sweeping.
1792 size_t do_garbage_chunk(FreeChunk *fc);
1793 // Process a live chunk during sweeping.
1794 size_t do_live_chunk(FreeChunk* fc);
1795
1796 // Accessors.
1797 HeapWord* freeFinger() const { return _freeFinger; }
1798 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1799 bool inFreeRange() const { return _inFreeRange; }
1800 void set_inFreeRange(bool v) { _inFreeRange = v; }
1801 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1802 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1803 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1804 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1805
1806 // Initialize a free range.
1807 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1808 // Return this chunk to the free lists.
1809 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1810
1811 // Check if we should yield and do so when necessary.
1812 inline void do_yield_check(HeapWord* addr);
1813
1814 // Yield
1815 void do_yield_work(HeapWord* addr);
1816
1817 // Debugging/Printing
1818 void print_free_block_coalesced(FreeChunk* fc) const;
1819
1820 public:
1821 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1822 CMSBitMap* bitMap, bool should_yield);
1823 ~SweepClosure() PRODUCT_RETURN;
1824
1825 size_t do_blk_careful(HeapWord* addr);
1826 void print() const { print_on(tty); }
1827 void print_on(outputStream *st) const;
1828 };
1829
1830 // Closures related to weak references processing
1831
1832 // During CMS' weak reference processing, this is a
1833 // work-routine/closure used to complete transitive
1834 // marking of objects as live after a certain point
1835 // in which an initial set has been completely accumulated.
1836 // This closure is currently used both during the final
1837 // remark stop-world phase, as well as during the concurrent
1838 // precleaning of the discovered reference lists.
1839 class CMSDrainMarkingStackClosure: public VoidClosure {
1840 CMSCollector* _collector;
1841 MemRegion _span;
1842 CMSMarkStack* _mark_stack;
1843 CMSBitMap* _bit_map;
1844 CMSKeepAliveClosure* _keep_alive;
1845 bool _concurrent_precleaning;
1846 public:
1847 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1848 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1849 CMSKeepAliveClosure* keep_alive,
1850 bool cpc):
1851 _collector(collector),
1852 _span(span),
1853 _bit_map(bit_map),
1854 _mark_stack(mark_stack),
1855 _keep_alive(keep_alive),
1856 _concurrent_precleaning(cpc) {
1857 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1858 "Mismatch");
1859 }
1860
1861 void do_void();
1862 };
1863
1864 // A parallel version of CMSDrainMarkingStackClosure above.
1865 class CMSParDrainMarkingStackClosure: public VoidClosure {
1866 CMSCollector* _collector;
1867 MemRegion _span;
1868 OopTaskQueue* _work_queue;
1869 CMSBitMap* _bit_map;
1870 CMSInnerParMarkAndPushClosure _mark_and_push;
1871
1872 public:
1873 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1874 MemRegion span, CMSBitMap* bit_map,
1875 CMSMarkStack* revisit_stack,
1876 OopTaskQueue* work_queue):
1877 _collector(collector),
1878 _span(span),
1879 _bit_map(bit_map),
1880 _work_queue(work_queue),
1881 _mark_and_push(collector, span, bit_map, revisit_stack, work_queue) { }
1882
1883 public:
1884 void trim_queue(uint max);
1885 void do_void();
1886 };
1887
1888 // Allow yielding or short-circuiting of reference list
1889 // prelceaning work.
1890 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1891 CMSCollector* _collector;
1892 void do_yield_work();
1893 public:
1894 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1895 _collector(collector) {}
1896 virtual bool should_return();
1897 };
1898
1899
1900 // Convenience class that locks free list locks for given CMS collector
1901 class FreelistLocker: public StackObj {
1902 private:
1903 CMSCollector* _collector;
1904 public:
1905 FreelistLocker(CMSCollector* collector):
1906 _collector(collector) {
1907 _collector->getFreelistLocks();
1908 }
1909
1910 ~FreelistLocker() {
1911 _collector->releaseFreelistLocks();
1912 }
1913 };
1914
1915 // Mark all dead objects in a given space.
1916 class MarkDeadObjectsClosure: public BlkClosure {
1917 const CMSCollector* _collector;
1918 const CompactibleFreeListSpace* _sp;
1919 CMSBitMap* _live_bit_map;
1920 CMSBitMap* _dead_bit_map;
1921 public:
1922 MarkDeadObjectsClosure(const CMSCollector* collector,
1923 const CompactibleFreeListSpace* sp,
1924 CMSBitMap *live_bit_map,
1925 CMSBitMap *dead_bit_map) :
1926 _collector(collector),
1927 _sp(sp),
1928 _live_bit_map(live_bit_map),
1929 _dead_bit_map(dead_bit_map) {}
1930 size_t do_blk(HeapWord* addr);
1931 };
1932
1933 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1934
1935 public:
1936 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1937 };
1938
1939
1940 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP