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 CMSParRemarkTask;
520 friend class CMSConcMarkingTask;
521 friend class CMSRefProcTaskProxy;
522 friend class CMSRefProcTaskExecutor;
523 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
524 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
525 friend class PushOrMarkClosure; // to access _restart_addr
526 friend class Par_PushOrMarkClosure; // to access _restart_addr
527 friend class MarkFromRootsClosure; // -- ditto --
528 // ... and for clearing cards
529 friend class Par_MarkFromRootsClosure; // to access _restart_addr
530 // ... and for clearing cards
531 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
532 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
533 friend class PushAndMarkVerifyClosure; // -- ditto --
534 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
535 friend class PushAndMarkClosure; // -- ditto --
536 friend class Par_PushAndMarkClosure; // -- ditto --
537 friend class CMSKeepAliveClosure; // -- ditto --
538 friend class CMSDrainMarkingStackClosure; // -- ditto --
539 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
540 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
541 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
542 friend class VM_CMS_Operation;
543 friend class VM_CMS_Initial_Mark;
544 friend class VM_CMS_Final_Remark;
545 friend class TraceCMSMemoryManagerStats;
546
547 private:
548 jlong _time_of_last_gc;
549 void update_time_of_last_gc(jlong now) {
550 _time_of_last_gc = now;
551 }
552
553 OopTaskQueueSet* _task_queues;
554
555 // Overflow list of grey objects, threaded through mark-word
556 // Manipulated with CAS in the parallel/multi-threaded case.
557 oop _overflow_list;
558 // The following array-pair keeps track of mark words
559 // displaced for accomodating overflow list above.
560 // This code will likely be revisited under RFE#4922830.
561 Stack<oop, mtGC> _preserved_oop_stack;
562 Stack<markOop, mtGC> _preserved_mark_stack;
563
564 int* _hash_seed;
565
566 // In support of multi-threaded concurrent phases
567 YieldingFlexibleWorkGang* _conc_workers;
568
569 // Performance Counters
570 CollectorCounters* _gc_counters;
571
572 // Initialization Errors
573 bool _completed_initialization;
574
575 // In support of ExplicitGCInvokesConcurrent
576 static bool _full_gc_requested;
577 static GCCause::Cause _full_gc_cause;
578 unsigned int _collection_count_start;
579
580 // Should we unload classes this concurrent cycle?
581 bool _should_unload_classes;
582 unsigned int _concurrent_cycles_since_last_unload;
583 unsigned int concurrent_cycles_since_last_unload() const {
584 return _concurrent_cycles_since_last_unload;
585 }
586 // Did we (allow) unload classes in the previous concurrent cycle?
587 bool unloaded_classes_last_cycle() const {
588 return concurrent_cycles_since_last_unload() == 0;
589 }
590 // Root scanning options for perm gen
591 int _roots_scanning_options;
592 int roots_scanning_options() const { return _roots_scanning_options; }
593 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
594 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
595
596 // Verification support
597 CMSBitMap _verification_mark_bm;
598 void verify_after_remark_work_1();
599 void verify_after_remark_work_2();
600
601 // true if any verification flag is on.
602 bool _verifying;
603 bool verifying() const { return _verifying; }
604 void set_verifying(bool v) { _verifying = v; }
605
606 // Collector policy
607 ConcurrentMarkSweepPolicy* _collector_policy;
608 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
609
610 // XXX Move these to CMSStats ??? FIX ME !!!
611 elapsedTimer _inter_sweep_timer; // time between sweeps
612 elapsedTimer _intra_sweep_timer; // time _in_ sweeps
613 // padded decaying average estimates of the above
614 AdaptivePaddedAverage _inter_sweep_estimate;
615 AdaptivePaddedAverage _intra_sweep_estimate;
616
617 CMSTracer* _gc_tracer_cm;
618 ConcurrentGCTimer* _gc_timer_cm;
619
620 bool _cms_start_registered;
621
622 GCHeapSummary _last_heap_summary;
623 PermGenSummary _last_perm_gen_summary;
624
625 void register_foreground_gc_start(GCCause::Cause cause);
626 void register_gc_start(GCCause::Cause cause);
627 void register_gc_end();
628 void save_heap_summary();
629 void report_heap_summary(GCWhen::Type when);
630
631 protected:
632 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
633 ConcurrentMarkSweepGeneration* _permGen; // perm gen
634 MemRegion _span; // span covering above two
635 CardTableRS* _ct; // card table
636
637 // CMS marking support structures
638 CMSBitMap _markBitMap;
639 CMSBitMap _modUnionTable;
640 CMSMarkStack _markStack;
641 CMSMarkStack _revisitStack; // used to keep track of klassKlass objects
642 // to revisit
643 CMSBitMap _perm_gen_verify_bit_map; // Mark bit map for perm gen verification support.
644
645 HeapWord* _restart_addr; // in support of marking stack overflow
646 void lower_restart_addr(HeapWord* low);
647
648 // Counters in support of marking stack / work queue overflow handling:
649 // a non-zero value indicates certain types of overflow events during
650 // the current CMS cycle and could lead to stack resizing efforts at
651 // an opportune future time.
652 size_t _ser_pmc_preclean_ovflw;
653 size_t _ser_pmc_remark_ovflw;
654 size_t _par_pmc_remark_ovflw;
655 size_t _ser_kac_preclean_ovflw;
656 size_t _ser_kac_ovflw;
657 size_t _par_kac_ovflw;
658 NOT_PRODUCT(ssize_t _num_par_pushes;)
659
660 // ("Weak") Reference processing support
661 ReferenceProcessor* _ref_processor;
662 CMSIsAliveClosure _is_alive_closure;
663 // keep this textually after _markBitMap and _span; c'tor dependency
664
665 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
666 ModUnionClosure _modUnionClosure;
667 ModUnionClosurePar _modUnionClosurePar;
668
669 // CMS abstract state machine
670 // initial_state: Idling
671 // next_state(Idling) = {Marking}
672 // next_state(Marking) = {Precleaning, Sweeping}
673 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
674 // next_state(AbortablePreclean) = {FinalMarking}
675 // next_state(FinalMarking) = {Sweeping}
676 // next_state(Sweeping) = {Resizing}
677 // next_state(Resizing) = {Resetting}
678 // next_state(Resetting) = {Idling}
679 // The numeric values below are chosen so that:
680 // . _collectorState <= Idling == post-sweep && pre-mark
681 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
682 // precleaning || abortablePrecleanb
683 public:
684 enum CollectorState {
685 Resizing = 0,
686 Resetting = 1,
687 Idling = 2,
688 InitialMarking = 3,
689 Marking = 4,
690 Precleaning = 5,
691 AbortablePreclean = 6,
692 FinalMarking = 7,
693 Sweeping = 8
694 };
695 protected:
696 static CollectorState _collectorState;
697
698 // State related to prologue/epilogue invocation for my generations
699 bool _between_prologue_and_epilogue;
700
701 // Signalling/State related to coordination between fore- and backgroud GC
702 // Note: When the baton has been passed from background GC to foreground GC,
703 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
704 static bool _foregroundGCIsActive; // true iff foreground collector is active or
705 // wants to go active
706 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
707 // yet passed the baton to the foreground GC
708
709 // Support for CMSScheduleRemark (abortable preclean)
710 bool _abort_preclean;
711 bool _start_sampling;
712
713 int _numYields;
714 size_t _numDirtyCards;
715 size_t _sweep_count;
716 // number of full gc's since the last concurrent gc.
717 uint _full_gcs_since_conc_gc;
718
719 // occupancy used for bootstrapping stats
720 double _bootstrap_occupancy;
721
722 // timer
723 elapsedTimer _timer;
724
725 // Timing, allocation and promotion statistics, used for scheduling.
726 CMSStats _stats;
727
728 // Allocation limits installed in the young gen, used only in
729 // CMSIncrementalMode. When an allocation in the young gen would cross one of
730 // these limits, the cms generation is notified and the cms thread is started
731 // or stopped, respectively.
732 HeapWord* _icms_start_limit;
733 HeapWord* _icms_stop_limit;
734
735 enum CMS_op_type {
736 CMS_op_checkpointRootsInitial,
737 CMS_op_checkpointRootsFinal
738 };
739
740 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
741 bool stop_world_and_do(CMS_op_type op);
742
743 OopTaskQueueSet* task_queues() { return _task_queues; }
744 int* hash_seed(int i) { return &_hash_seed[i]; }
745 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
746
747 // Support for parallelizing Eden rescan in CMS remark phase
748 void sample_eden(); // ... sample Eden space top
749
750 private:
751 // Support for parallelizing young gen rescan in CMS remark phase
752 Generation* _young_gen; // the younger gen
753 HeapWord** _top_addr; // ... Top of Eden
754 HeapWord** _end_addr; // ... End of Eden
755 HeapWord** _eden_chunk_array; // ... Eden partitioning array
756 size_t _eden_chunk_index; // ... top (exclusive) of array
757 size_t _eden_chunk_capacity; // ... max entries in array
758
759 // Support for parallelizing survivor space rescan
760 HeapWord** _survivor_chunk_array;
761 size_t _survivor_chunk_index;
762 size_t _survivor_chunk_capacity;
763 size_t* _cursor;
764 ChunkArray* _survivor_plab_array;
765
766 // Support for marking stack overflow handling
767 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
768 bool par_take_from_overflow_list(size_t num,
769 OopTaskQueue* to_work_q,
770 int no_of_gc_threads);
771 void push_on_overflow_list(oop p);
772 void par_push_on_overflow_list(oop p);
773 // the following is, obviously, not, in general, "MT-stable"
774 bool overflow_list_is_empty() const;
775
776 void preserve_mark_if_necessary(oop p);
777 void par_preserve_mark_if_necessary(oop p);
778 void preserve_mark_work(oop p, markOop m);
779 void restore_preserved_marks_if_any();
780 NOT_PRODUCT(bool no_preserved_marks() const;)
781 // in support of testing overflow code
782 NOT_PRODUCT(int _overflow_counter;)
783 NOT_PRODUCT(bool simulate_overflow();) // sequential
784 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
785
786 // CMS work methods
787 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
788
789 // a return value of false indicates failure due to stack overflow
790 bool markFromRootsWork(bool asynch); // concurrent marking work
791
792 public: // FIX ME!!! only for testing
793 bool do_marking_st(bool asynch); // single-threaded marking
794 bool do_marking_mt(bool asynch); // multi-threaded marking
795
796 private:
797
798 // concurrent precleaning work
799 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
800 ScanMarkedObjectsAgainCarefullyClosure* cl);
801 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
802 ScanMarkedObjectsAgainCarefullyClosure* cl);
803 // Does precleaning work, returning a quantity indicative of
804 // the amount of "useful work" done.
805 size_t preclean_work(bool clean_refs, bool clean_survivors);
806 void abortable_preclean(); // Preclean while looking for possible abort
807 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
808 // Helper function for above; merge-sorts the per-thread plab samples
809 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
810 // Resets (i.e. clears) the per-thread plab sample vectors
811 void reset_survivor_plab_arrays();
812
813 // final (second) checkpoint work
814 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
815 bool init_mark_was_synchronous);
816 // work routine for parallel version of remark
817 void do_remark_parallel();
818 // work routine for non-parallel version of remark
819 void do_remark_non_parallel();
820 // reference processing work routine (during second checkpoint)
821 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
822
823 // concurrent sweeping work
824 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
825
826 // (concurrent) resetting of support data structures
827 void reset(bool asynch);
828
829 // Clear _expansion_cause fields of constituent generations
830 void clear_expansion_cause();
831
832 // An auxilliary method used to record the ends of
833 // used regions of each generation to limit the extent of sweep
834 void save_sweep_limits();
835
836 // Resize the generations included in the collector.
837 void compute_new_size();
838
839 // A work method used by foreground collection to determine
840 // what type of collection (compacting or not, continuing or fresh)
841 // it should do.
842 void decide_foreground_collection_type(bool clear_all_soft_refs,
843 bool* should_compact, bool* should_start_over);
844
845 // A work method used by the foreground collector to do
846 // a mark-sweep-compact.
847 void do_compaction_work(bool clear_all_soft_refs);
848
849 // A work method used by the foreground collector to do
850 // a mark-sweep, after taking over from a possibly on-going
851 // concurrent mark-sweep collection.
852 void do_mark_sweep_work(bool clear_all_soft_refs,
853 CollectorState first_state, bool should_start_over);
854
855 // Work methods for reporting concurrent mode interruption or failure
856 bool is_external_interruption();
857 void report_concurrent_mode_interruption();
858
859 // If the backgrould GC is active, acquire control from the background
860 // GC and do the collection.
861 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
862
863 // For synchronizing passing of control from background to foreground
864 // GC. waitForForegroundGC() is called by the background
865 // collector. It if had to wait for a foreground collection,
866 // it returns true and the background collection should assume
867 // that the collection was finished by the foreground
868 // collector.
869 bool waitForForegroundGC();
870
871 // Incremental mode triggering: recompute the icms duty cycle and set the
872 // allocation limits in the young gen.
873 void icms_update_allocation_limits();
874
875 size_t block_size_using_printezis_bits(HeapWord* addr) const;
876 size_t block_size_if_printezis_bits(HeapWord* addr) const;
877 HeapWord* next_card_start_after_block(HeapWord* addr) const;
878
879 void setup_cms_unloading_and_verification_state();
880 public:
881 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
882 ConcurrentMarkSweepGeneration* permGen,
883 CardTableRS* ct,
884 ConcurrentMarkSweepPolicy* cp);
885 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
886
887 ReferenceProcessor* ref_processor() { return _ref_processor; }
888 void ref_processor_init();
889
890 Mutex* bitMapLock() const { return _markBitMap.lock(); }
891 static CollectorState abstract_state() { return _collectorState; }
892
893 bool should_abort_preclean() const; // Whether preclean should be aborted.
894 size_t get_eden_used() const;
895 size_t get_eden_capacity() const;
896
897 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
898
899 // locking checks
900 NOT_PRODUCT(static bool have_cms_token();)
901
902 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
903 bool shouldConcurrentCollect();
904
905 void collect(bool full,
906 bool clear_all_soft_refs,
907 size_t size,
908 bool tlab);
909 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
910 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
911
912 // In support of ExplicitGCInvokesConcurrent
913 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
914 // Should we unload classes in a particular concurrent cycle?
915 bool should_unload_classes() const {
916 return _should_unload_classes;
917 }
918 bool update_should_unload_classes();
919
920 void direct_allocated(HeapWord* start, size_t size);
921
922 // Object is dead if not marked and current phase is sweeping.
923 bool is_dead_obj(oop obj) const;
924
925 // After a promotion (of "start"), do any necessary marking.
926 // If "par", then it's being done by a parallel GC thread.
927 // The last two args indicate if we need precise marking
928 // and if so the size of the object so it can be dirtied
929 // in its entirety.
930 void promoted(bool par, HeapWord* start,
931 bool is_obj_array, size_t obj_size);
932
933 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
934 size_t word_size);
935
936 void getFreelistLocks() const;
937 void releaseFreelistLocks() const;
938 bool haveFreelistLocks() const;
939
940 // GC prologue and epilogue
941 void gc_prologue(bool full);
942 void gc_epilogue(bool full);
943
944 jlong time_of_last_gc(jlong now) {
945 if (_collectorState <= Idling) {
946 // gc not in progress
947 return _time_of_last_gc;
948 } else {
949 // collection in progress
950 return now;
951 }
952 }
953
954 // Support for parallel remark of survivor space
955 void* get_data_recorder(int thr_num);
956
957 CMSBitMap* markBitMap() { return &_markBitMap; }
958 void directAllocated(HeapWord* start, size_t size);
959
960 // main CMS steps and related support
961 void checkpointRootsInitial(bool asynch);
962 bool markFromRoots(bool asynch); // a return value of false indicates failure
963 // due to stack overflow
964 void preclean();
965 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
966 bool init_mark_was_synchronous);
967 void sweep(bool asynch);
968
969 // Check that the currently executing thread is the expected
970 // one (foreground collector or background collector).
971 static void check_correct_thread_executing() PRODUCT_RETURN;
972 // XXXPERM void print_statistics() PRODUCT_RETURN;
973
974 bool is_cms_reachable(HeapWord* addr);
975
976 // Performance Counter Support
977 CollectorCounters* counters() { return _gc_counters; }
978
979 // timer stuff
980 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
981 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
982 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
983 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
984
985 int yields() { return _numYields; }
986 void resetYields() { _numYields = 0; }
987 void incrementYields() { _numYields++; }
988 void resetNumDirtyCards() { _numDirtyCards = 0; }
989 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
990 size_t numDirtyCards() { return _numDirtyCards; }
991
992 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
993 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
994 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
995 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
996 size_t sweep_count() const { return _sweep_count; }
997 void increment_sweep_count() { _sweep_count++; }
998
999 // Timers/stats for gc scheduling and incremental mode pacing.
1000 CMSStats& stats() { return _stats; }
1001
1002 // Convenience methods that check whether CMSIncrementalMode is enabled and
1003 // forward to the corresponding methods in ConcurrentMarkSweepThread.
1004 static void start_icms();
1005 static void stop_icms(); // Called at the end of the cms cycle.
1006 static void disable_icms(); // Called before a foreground collection.
1007 static void enable_icms(); // Called after a foreground collection.
1008 void icms_wait(); // Called at yield points.
1009
1010 // Adaptive size policy
1011 CMSAdaptiveSizePolicy* size_policy();
1012 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1013
1014 // debugging
1015 void verify();
1016 bool verify_after_remark();
1017 void verify_ok_to_terminate() const PRODUCT_RETURN;
1018 void verify_work_stacks_empty() const PRODUCT_RETURN;
1019 void verify_overflow_empty() const PRODUCT_RETURN;
1020
1021 // convenience methods in support of debugging
1022 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1023 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1024
1025 // accessors
1026 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1027 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1028
1029 // Get the bit map with a perm gen "deadness" information.
1030 CMSBitMap* perm_gen_verify_bit_map() { return &_perm_gen_verify_bit_map; }
1031
1032 // Initialization errors
1033 bool completed_initialization() { return _completed_initialization; }
1034 };
1035
1036 class CMSExpansionCause : public AllStatic {
1037 public:
1038 enum Cause {
1039 _no_expansion,
1040 _satisfy_free_ratio,
1041 _satisfy_promotion,
1042 _satisfy_allocation,
1043 _allocate_par_lab,
1044 _allocate_par_spooling_space,
1045 _adaptive_size_policy
1046 };
1047 // Return a string describing the cause of the expansion.
1048 static const char* to_string(CMSExpansionCause::Cause cause);
1049 };
1050
1051 class ConcurrentMarkSweepGeneration: public CardGeneration {
1052 friend class VMStructs;
1053 friend class ConcurrentMarkSweepThread;
1054 friend class ConcurrentMarkSweep;
1055 friend class CMSCollector;
1056 protected:
1057 static CMSCollector* _collector; // the collector that collects us
1058 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1059
1060 // Performance Counters
1061 GenerationCounters* _gen_counters;
1062 GSpaceCounters* _space_counters;
1063
1064 // Words directly allocated, used by CMSStats.
1065 size_t _direct_allocated_words;
1066
1067 // Non-product stat counters
1068 NOT_PRODUCT(
1069 size_t _numObjectsPromoted;
1070 size_t _numWordsPromoted;
1071 size_t _numObjectsAllocated;
1072 size_t _numWordsAllocated;
1073 )
1074
1075 // Used for sizing decisions
1076 bool _incremental_collection_failed;
1077 bool incremental_collection_failed() {
1078 return _incremental_collection_failed;
1079 }
1080 void set_incremental_collection_failed() {
1081 _incremental_collection_failed = true;
1082 }
1083 void clear_incremental_collection_failed() {
1084 _incremental_collection_failed = false;
1085 }
1086
1087 // accessors
1088 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1089 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1090
1091 private:
1092 // For parallel young-gen GC support.
1093 CMSParGCThreadState** _par_gc_thread_states;
1094
1095 // Reason generation was expanded
1096 CMSExpansionCause::Cause _expansion_cause;
1097
1098 // In support of MinChunkSize being larger than min object size
1099 const double _dilatation_factor;
1100
1101 enum CollectionTypes {
1102 Concurrent_collection_type = 0,
1103 MS_foreground_collection_type = 1,
1104 MSC_foreground_collection_type = 2,
1105 Unknown_collection_type = 3
1106 };
1107
1108 CollectionTypes _debug_collection_type;
1109
1110 // Fraction of current occupancy at which to start a CMS collection which
1111 // will collect this generation (at least).
1112 double _initiating_occupancy;
1113
1114 protected:
1115 // Shrink generation by specified size (returns false if unable to shrink)
1116 virtual void shrink_by(size_t bytes);
1117
1118 // Update statistics for GC
1119 virtual void update_gc_stats(int level, bool full);
1120
1121 // Maximum available space in the generation (including uncommitted)
1122 // space.
1123 size_t max_available() const;
1124
1125 // getter and initializer for _initiating_occupancy field.
1126 double initiating_occupancy() const { return _initiating_occupancy; }
1127 void init_initiating_occupancy(intx io, intx tr);
1128
1129 public:
1130 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1131 int level, CardTableRS* ct,
1132 bool use_adaptive_freelists,
1133 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1134
1135 // Accessors
1136 CMSCollector* collector() const { return _collector; }
1137 static void set_collector(CMSCollector* collector) {
1138 assert(_collector == NULL, "already set");
1139 _collector = collector;
1140 }
1141 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1142
1143 Mutex* freelistLock() const;
1144
1145 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1146
1147 // Adaptive size policy
1148 CMSAdaptiveSizePolicy* size_policy();
1149
1150 bool refs_discovery_is_atomic() const { return false; }
1151 bool refs_discovery_is_mt() const {
1152 // Note: CMS does MT-discovery during the parallel-remark
1153 // phases. Use ReferenceProcessorMTMutator to make refs
1154 // discovery MT-safe during such phases or other parallel
1155 // discovery phases in the future. This may all go away
1156 // if/when we decide that refs discovery is sufficiently
1157 // rare that the cost of the CAS's involved is in the
1158 // noise. That's a measurement that should be done, and
1159 // the code simplified if that turns out to be the case.
1160 return ConcGCThreads > 1;
1161 }
1162
1163 // Override
1164 virtual void ref_processor_init();
1165
1166 // Grow generation by specified size (returns false if unable to grow)
1167 bool grow_by(size_t bytes);
1168 // Grow generation to reserved size.
1169 bool grow_to_reserved();
1170
1171 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1172
1173 // Space enquiries
1174 size_t capacity() const;
1175 size_t used() const;
1176 size_t free() const;
1177 double occupancy() const { return ((double)used())/((double)capacity()); }
1178 size_t contiguous_available() const;
1179 size_t unsafe_max_alloc_nogc() const;
1180
1181 // over-rides
1182 MemRegion used_region() const;
1183 MemRegion used_region_at_save_marks() const;
1184
1185 // Does a "full" (forced) collection invoked on this generation collect
1186 // all younger generations as well? Note that the second conjunct is a
1187 // hack to allow the collection of the younger gen first if the flag is
1188 // set. This is better than using th policy's should_collect_gen0_first()
1189 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1190 virtual bool full_collects_younger_generations() const {
1191 return UseCMSCompactAtFullCollection && !CollectGen0First;
1192 }
1193
1194 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1195
1196 // Support for compaction
1197 CompactibleSpace* first_compaction_space() const;
1198 // Adjust quantites in the generation affected by
1199 // the compaction.
1200 void reset_after_compaction();
1201
1202 // Allocation support
1203 HeapWord* allocate(size_t size, bool tlab);
1204 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1205 oop promote(oop obj, size_t obj_size);
1206 HeapWord* par_allocate(size_t size, bool tlab) {
1207 return allocate(size, tlab);
1208 }
1209
1210 // Incremental mode triggering.
1211 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1212 size_t word_size);
1213
1214 // Used by CMSStats to track direct allocation. The value is sampled and
1215 // reset after each young gen collection.
1216 size_t direct_allocated_words() const { return _direct_allocated_words; }
1217 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1218
1219 // Overrides for parallel promotion.
1220 virtual oop par_promote(int thread_num,
1221 oop obj, markOop m, size_t word_sz);
1222 // This one should not be called for CMS.
1223 virtual void par_promote_alloc_undo(int thread_num,
1224 HeapWord* obj, size_t word_sz);
1225 virtual void par_promote_alloc_done(int thread_num);
1226 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1227
1228 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1229
1230 // Inform this (non-young) generation that a promotion failure was
1231 // encountered during a collection of a younger generation that
1232 // promotes into this generation.
1233 virtual void promotion_failure_occurred();
1234
1235 bool should_collect(bool full, size_t size, bool tlab);
1236 virtual bool should_concurrent_collect() const;
1237 virtual bool is_too_full() const;
1238 void collect(bool full,
1239 bool clear_all_soft_refs,
1240 size_t size,
1241 bool tlab);
1242
1243 HeapWord* expand_and_allocate(size_t word_size,
1244 bool tlab,
1245 bool parallel = false);
1246
1247 // GC prologue and epilogue
1248 void gc_prologue(bool full);
1249 void gc_prologue_work(bool full, bool registerClosure,
1250 ModUnionClosure* modUnionClosure);
1251 void gc_epilogue(bool full);
1252 void gc_epilogue_work(bool full);
1253
1254 // Time since last GC of this generation
1255 jlong time_of_last_gc(jlong now) {
1256 return collector()->time_of_last_gc(now);
1257 }
1258 void update_time_of_last_gc(jlong now) {
1259 collector()-> update_time_of_last_gc(now);
1260 }
1261
1262 // Allocation failure
1263 void expand(size_t bytes, size_t expand_bytes,
1264 CMSExpansionCause::Cause cause);
1265 virtual bool expand(size_t bytes, size_t expand_bytes);
1266 void shrink(size_t bytes);
1267 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1268 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1269
1270 // Iteration support and related enquiries
1271 void save_marks();
1272 bool no_allocs_since_save_marks();
1273 void object_iterate_since_last_GC(ObjectClosure* cl);
1274 void younger_refs_iterate(OopsInGenClosure* cl);
1275
1276 // Iteration support specific to CMS generations
1277 void save_sweep_limit();
1278
1279 // More iteration support
1280 virtual void oop_iterate(MemRegion mr, OopClosure* cl);
1281 virtual void oop_iterate(OopClosure* cl);
1282 virtual void safe_object_iterate(ObjectClosure* cl);
1283 virtual void object_iterate(ObjectClosure* cl);
1284
1285 // Need to declare the full complement of closures, whether we'll
1286 // override them or not, or get message from the compiler:
1287 // oop_since_save_marks_iterate_nv hides virtual function...
1288 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1289 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1290 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1291
1292 // Smart allocation XXX -- move to CFLSpace?
1293 void setNearLargestChunk();
1294 bool isNearLargestChunk(HeapWord* addr);
1295
1296 // Get the chunk at the end of the space. Delagates to
1297 // the space.
1298 FreeChunk* find_chunk_at_end();
1299
1300 // Overriding of unused functionality (sharing not yet supported with CMS)
1301 void pre_adjust_pointers();
1302 void post_compact();
1303
1304 // Debugging
1305 void prepare_for_verify();
1306 void verify();
1307 void print_statistics() PRODUCT_RETURN;
1308
1309 // Performance Counters support
1310 virtual void update_counters();
1311 virtual void update_counters(size_t used);
1312 void initialize_performance_counters();
1313 CollectorCounters* counters() { return collector()->counters(); }
1314
1315 // Support for parallel remark of survivor space
1316 void* get_data_recorder(int thr_num) {
1317 //Delegate to collector
1318 return collector()->get_data_recorder(thr_num);
1319 }
1320
1321 // Printing
1322 const char* name() const;
1323 virtual const char* short_name() const { return "CMS"; }
1324 void print() const;
1325 void printOccupancy(const char* s);
1326 bool must_be_youngest() const { return false; }
1327 bool must_be_oldest() const { return true; }
1328
1329 void compute_new_size();
1330
1331 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1332 void rotate_debug_collection_type();
1333 };
1334
1335 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1336
1337 // Return the size policy from the heap's collector
1338 // policy casted to CMSAdaptiveSizePolicy*.
1339 CMSAdaptiveSizePolicy* cms_size_policy() const;
1340
1341 // Resize the generation based on the adaptive size
1342 // policy.
1343 void resize(size_t cur_promo, size_t desired_promo);
1344
1345 // Return the GC counters from the collector policy
1346 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1347
1348 virtual void shrink_by(size_t bytes);
1349
1350 public:
1351 virtual void compute_new_size();
1352 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1353 int level, CardTableRS* ct,
1354 bool use_adaptive_freelists,
1355 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1356 dictionaryChoice) :
1357 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1358 use_adaptive_freelists, dictionaryChoice) {}
1359
1360 virtual const char* short_name() const { return "ASCMS"; }
1361 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1362
1363 virtual void update_counters();
1364 virtual void update_counters(size_t used);
1365 };
1366
1367 //
1368 // Closures of various sorts used by CMS to accomplish its work
1369 //
1370
1371 // This closure is used to check that a certain set of oops is empty.
1372 class FalseClosure: public OopClosure {
1373 public:
1374 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1375 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1376 };
1377
1378 // This closure is used to do concurrent marking from the roots
1379 // following the first checkpoint.
1380 class MarkFromRootsClosure: public BitMapClosure {
1381 CMSCollector* _collector;
1382 MemRegion _span;
1383 CMSBitMap* _bitMap;
1384 CMSBitMap* _mut;
1385 CMSMarkStack* _markStack;
1386 CMSMarkStack* _revisitStack;
1387 bool _yield;
1388 int _skipBits;
1389 HeapWord* _finger;
1390 HeapWord* _threshold;
1391 DEBUG_ONLY(bool _verifying;)
1392
1393 public:
1394 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1395 CMSBitMap* bitMap,
1396 CMSMarkStack* markStack,
1397 CMSMarkStack* revisitStack,
1398 bool should_yield, bool verifying = false);
1399 bool do_bit(size_t offset);
1400 void reset(HeapWord* addr);
1401 inline void do_yield_check();
1402
1403 private:
1404 void scanOopsInOop(HeapWord* ptr);
1405 void do_yield_work();
1406 };
1407
1408 // This closure is used to do concurrent multi-threaded
1409 // marking from the roots following the first checkpoint.
1410 // XXX This should really be a subclass of The serial version
1411 // above, but i have not had the time to refactor things cleanly.
1412 // That willbe done for Dolphin.
1413 class Par_MarkFromRootsClosure: public BitMapClosure {
1414 CMSCollector* _collector;
1415 MemRegion _whole_span;
1416 MemRegion _span;
1417 CMSBitMap* _bit_map;
1418 CMSBitMap* _mut;
1419 OopTaskQueue* _work_queue;
1420 CMSMarkStack* _overflow_stack;
1421 CMSMarkStack* _revisit_stack;
1422 bool _yield;
1423 int _skip_bits;
1424 HeapWord* _finger;
1425 HeapWord* _threshold;
1426 CMSConcMarkingTask* _task;
1427 public:
1428 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1429 MemRegion span,
1430 CMSBitMap* bit_map,
1431 OopTaskQueue* work_queue,
1432 CMSMarkStack* overflow_stack,
1433 CMSMarkStack* revisit_stack,
1434 bool should_yield);
1435 bool do_bit(size_t offset);
1436 inline void do_yield_check();
1437
1438 private:
1439 void scan_oops_in_oop(HeapWord* ptr);
1440 void do_yield_work();
1441 bool get_work_from_overflow_stack();
1442 };
1443
1444 // The following closures are used to do certain kinds of verification of
1445 // CMS marking.
1446 class PushAndMarkVerifyClosure: public OopClosure {
1447 CMSCollector* _collector;
1448 MemRegion _span;
1449 CMSBitMap* _verification_bm;
1450 CMSBitMap* _cms_bm;
1451 CMSMarkStack* _mark_stack;
1452 protected:
1453 void do_oop(oop p);
1454 template <class T> inline void do_oop_work(T *p) {
1455 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
1456 do_oop(obj);
1457 }
1458 public:
1459 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1460 MemRegion span,
1461 CMSBitMap* verification_bm,
1462 CMSBitMap* cms_bm,
1463 CMSMarkStack* mark_stack);
1464 void do_oop(oop* p);
1465 void do_oop(narrowOop* p);
1466 // Deal with a stack overflow condition
1467 void handle_stack_overflow(HeapWord* lost);
1468 };
1469
1470 class MarkFromRootsVerifyClosure: public BitMapClosure {
1471 CMSCollector* _collector;
1472 MemRegion _span;
1473 CMSBitMap* _verification_bm;
1474 CMSBitMap* _cms_bm;
1475 CMSMarkStack* _mark_stack;
1476 HeapWord* _finger;
1477 PushAndMarkVerifyClosure _pam_verify_closure;
1478 public:
1479 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1480 CMSBitMap* verification_bm,
1481 CMSBitMap* cms_bm,
1482 CMSMarkStack* mark_stack);
1483 bool do_bit(size_t offset);
1484 void reset(HeapWord* addr);
1485 };
1486
1487
1488 // This closure is used to check that a certain set of bits is
1489 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1490 class FalseBitMapClosure: public BitMapClosure {
1491 public:
1492 bool do_bit(size_t offset) {
1493 guarantee(false, "Should not have a 1 bit");
1494 return true;
1495 }
1496 };
1497
1498 // This closure is used during the second checkpointing phase
1499 // to rescan the marked objects on the dirty cards in the mod
1500 // union table and the card table proper. It's invoked via
1501 // MarkFromDirtyCardsClosure below. It uses either
1502 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1503 // declared in genOopClosures.hpp to accomplish some of its work.
1504 // In the parallel case the bitMap is shared, so access to
1505 // it needs to be suitably synchronized for updates by embedded
1506 // closures that update it; however, this closure itself only
1507 // reads the bit_map and because it is idempotent, is immune to
1508 // reading stale values.
1509 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1510 #ifdef ASSERT
1511 CMSCollector* _collector;
1512 MemRegion _span;
1513 union {
1514 CMSMarkStack* _mark_stack;
1515 OopTaskQueue* _work_queue;
1516 };
1517 #endif // ASSERT
1518 bool _parallel;
1519 CMSBitMap* _bit_map;
1520 union {
1521 MarkRefsIntoAndScanClosure* _scan_closure;
1522 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1523 };
1524
1525 public:
1526 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1527 MemRegion span,
1528 ReferenceProcessor* rp,
1529 CMSBitMap* bit_map,
1530 CMSMarkStack* mark_stack,
1531 CMSMarkStack* revisit_stack,
1532 MarkRefsIntoAndScanClosure* cl):
1533 #ifdef ASSERT
1534 _collector(collector),
1535 _span(span),
1536 _mark_stack(mark_stack),
1537 #endif // ASSERT
1538 _parallel(false),
1539 _bit_map(bit_map),
1540 _scan_closure(cl) { }
1541
1542 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1543 MemRegion span,
1544 ReferenceProcessor* rp,
1545 CMSBitMap* bit_map,
1546 OopTaskQueue* work_queue,
1547 CMSMarkStack* revisit_stack,
1548 Par_MarkRefsIntoAndScanClosure* cl):
1549 #ifdef ASSERT
1550 _collector(collector),
1551 _span(span),
1552 _work_queue(work_queue),
1553 #endif // ASSERT
1554 _parallel(true),
1555 _bit_map(bit_map),
1556 _par_scan_closure(cl) { }
1557
1558 void do_object(oop obj) {
1559 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1560 }
1561 bool do_object_b(oop obj) {
1562 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1563 return false;
1564 }
1565 bool do_object_bm(oop p, MemRegion mr);
1566 };
1567
1568 // This closure is used during the second checkpointing phase
1569 // to rescan the marked objects on the dirty cards in the mod
1570 // union table and the card table proper. It invokes
1571 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1572 // In the parallel case, the bit map is shared and requires
1573 // synchronized access.
1574 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1575 CompactibleFreeListSpace* _space;
1576 ScanMarkedObjectsAgainClosure _scan_cl;
1577 size_t _num_dirty_cards;
1578
1579 public:
1580 MarkFromDirtyCardsClosure(CMSCollector* collector,
1581 MemRegion span,
1582 CompactibleFreeListSpace* space,
1583 CMSBitMap* bit_map,
1584 CMSMarkStack* mark_stack,
1585 CMSMarkStack* revisit_stack,
1586 MarkRefsIntoAndScanClosure* cl):
1587 _space(space),
1588 _num_dirty_cards(0),
1589 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1590 mark_stack, revisit_stack, cl) { }
1591
1592 MarkFromDirtyCardsClosure(CMSCollector* collector,
1593 MemRegion span,
1594 CompactibleFreeListSpace* space,
1595 CMSBitMap* bit_map,
1596 OopTaskQueue* work_queue,
1597 CMSMarkStack* revisit_stack,
1598 Par_MarkRefsIntoAndScanClosure* cl):
1599 _space(space),
1600 _num_dirty_cards(0),
1601 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1602 work_queue, revisit_stack, cl) { }
1603
1604 void do_MemRegion(MemRegion mr);
1605 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1606 size_t num_dirty_cards() { return _num_dirty_cards; }
1607 };
1608
1609 // This closure is used in the non-product build to check
1610 // that there are no MemRegions with a certain property.
1611 class FalseMemRegionClosure: public MemRegionClosure {
1612 void do_MemRegion(MemRegion mr) {
1613 guarantee(!mr.is_empty(), "Shouldn't be empty");
1614 guarantee(false, "Should never be here");
1615 }
1616 };
1617
1618 // This closure is used during the precleaning phase
1619 // to "carefully" rescan marked objects on dirty cards.
1620 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1621 // to accomplish some of its work.
1622 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1623 CMSCollector* _collector;
1624 MemRegion _span;
1625 bool _yield;
1626 Mutex* _freelistLock;
1627 CMSBitMap* _bitMap;
1628 CMSMarkStack* _markStack;
1629 MarkRefsIntoAndScanClosure* _scanningClosure;
1630
1631 public:
1632 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1633 MemRegion span,
1634 CMSBitMap* bitMap,
1635 CMSMarkStack* markStack,
1636 CMSMarkStack* revisitStack,
1637 MarkRefsIntoAndScanClosure* cl,
1638 bool should_yield):
1639 _collector(collector),
1640 _span(span),
1641 _yield(should_yield),
1642 _bitMap(bitMap),
1643 _markStack(markStack),
1644 _scanningClosure(cl) {
1645 }
1646
1647 void do_object(oop p) {
1648 guarantee(false, "call do_object_careful instead");
1649 }
1650
1651 size_t do_object_careful(oop p) {
1652 guarantee(false, "Unexpected caller");
1653 return 0;
1654 }
1655
1656 size_t do_object_careful_m(oop p, MemRegion mr);
1657
1658 void setFreelistLock(Mutex* m) {
1659 _freelistLock = m;
1660 _scanningClosure->set_freelistLock(m);
1661 }
1662
1663 private:
1664 inline bool do_yield_check();
1665
1666 void do_yield_work();
1667 };
1668
1669 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1670 CMSCollector* _collector;
1671 MemRegion _span;
1672 bool _yield;
1673 CMSBitMap* _bit_map;
1674 CMSMarkStack* _mark_stack;
1675 PushAndMarkClosure* _scanning_closure;
1676 unsigned int _before_count;
1677
1678 public:
1679 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1680 MemRegion span,
1681 CMSBitMap* bit_map,
1682 CMSMarkStack* mark_stack,
1683 PushAndMarkClosure* cl,
1684 unsigned int before_count,
1685 bool should_yield):
1686 _collector(collector),
1687 _span(span),
1688 _yield(should_yield),
1689 _bit_map(bit_map),
1690 _mark_stack(mark_stack),
1691 _scanning_closure(cl),
1692 _before_count(before_count)
1693 { }
1694
1695 void do_object(oop p) {
1696 guarantee(false, "call do_object_careful instead");
1697 }
1698
1699 size_t do_object_careful(oop p);
1700
1701 size_t do_object_careful_m(oop p, MemRegion mr) {
1702 guarantee(false, "Unexpected caller");
1703 return 0;
1704 }
1705
1706 private:
1707 inline void do_yield_check();
1708 void do_yield_work();
1709 };
1710
1711 // This closure is used to accomplish the sweeping work
1712 // after the second checkpoint but before the concurrent reset
1713 // phase.
1714 //
1715 // Terminology
1716 // left hand chunk (LHC) - block of one or more chunks currently being
1717 // coalesced. The LHC is available for coalescing with a new chunk.
1718 // right hand chunk (RHC) - block that is currently being swept that is
1719 // free or garbage that can be coalesced with the LHC.
1720 // _inFreeRange is true if there is currently a LHC
1721 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1722 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1723 // _freeFinger is the address of the current LHC
1724 class SweepClosure: public BlkClosureCareful {
1725 CMSCollector* _collector; // collector doing the work
1726 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1727 CompactibleFreeListSpace* _sp; // Space being swept
1728 HeapWord* _limit;// the address at or above which the sweep should stop
1729 // because we do not expect newly garbage blocks
1730 // eligible for sweeping past that address.
1731 Mutex* _freelistLock; // Free list lock (in space)
1732 CMSBitMap* _bitMap; // Marking bit map (in
1733 // generation)
1734 bool _inFreeRange; // Indicates if we are in the
1735 // midst of a free run
1736 bool _freeRangeInFreeLists;
1737 // Often, we have just found
1738 // a free chunk and started
1739 // a new free range; we do not
1740 // eagerly remove this chunk from
1741 // the free lists unless there is
1742 // a possibility of coalescing.
1743 // When true, this flag indicates
1744 // that the _freeFinger below
1745 // points to a potentially free chunk
1746 // that may still be in the free lists
1747 bool _lastFreeRangeCoalesced;
1748 // free range contains chunks
1749 // coalesced
1750 bool _yield;
1751 // Whether sweeping should be
1752 // done with yields. For instance
1753 // when done by the foreground
1754 // collector we shouldn't yield.
1755 HeapWord* _freeFinger; // When _inFreeRange is set, the
1756 // pointer to the "left hand
1757 // chunk"
1758 size_t _freeRangeSize;
1759 // When _inFreeRange is set, this
1760 // indicates the accumulated size
1761 // of the "left hand chunk"
1762 NOT_PRODUCT(
1763 size_t _numObjectsFreed;
1764 size_t _numWordsFreed;
1765 size_t _numObjectsLive;
1766 size_t _numWordsLive;
1767 size_t _numObjectsAlreadyFree;
1768 size_t _numWordsAlreadyFree;
1769 FreeChunk* _last_fc;
1770 )
1771 private:
1772 // Code that is common to a free chunk or garbage when
1773 // encountered during sweeping.
1774 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1775 // Process a free chunk during sweeping.
1776 void do_already_free_chunk(FreeChunk *fc);
1777 // Work method called when processing an already free or a
1778 // freshly garbage chunk to do a lookahead and possibly a
1779 // premptive flush if crossing over _limit.
1780 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1781 // Process a garbage chunk during sweeping.
1782 size_t do_garbage_chunk(FreeChunk *fc);
1783 // Process a live chunk during sweeping.
1784 size_t do_live_chunk(FreeChunk* fc);
1785
1786 // Accessors.
1787 HeapWord* freeFinger() const { return _freeFinger; }
1788 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1789 bool inFreeRange() const { return _inFreeRange; }
1790 void set_inFreeRange(bool v) { _inFreeRange = v; }
1791 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1792 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1793 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1794 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1795
1796 // Initialize a free range.
1797 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1798 // Return this chunk to the free lists.
1799 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1800
1801 // Check if we should yield and do so when necessary.
1802 inline void do_yield_check(HeapWord* addr);
1803
1804 // Yield
1805 void do_yield_work(HeapWord* addr);
1806
1807 // Debugging/Printing
1808 void print_free_block_coalesced(FreeChunk* fc) const;
1809
1810 public:
1811 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1812 CMSBitMap* bitMap, bool should_yield);
1813 ~SweepClosure() PRODUCT_RETURN;
1814
1815 size_t do_blk_careful(HeapWord* addr);
1816 void print() const { print_on(tty); }
1817 void print_on(outputStream *st) const;
1818 };
1819
1820 // Closures related to weak references processing
1821
1822 // During CMS' weak reference processing, this is a
1823 // work-routine/closure used to complete transitive
1824 // marking of objects as live after a certain point
1825 // in which an initial set has been completely accumulated.
1826 // This closure is currently used both during the final
1827 // remark stop-world phase, as well as during the concurrent
1828 // precleaning of the discovered reference lists.
1829 class CMSDrainMarkingStackClosure: public VoidClosure {
1830 CMSCollector* _collector;
1831 MemRegion _span;
1832 CMSMarkStack* _mark_stack;
1833 CMSBitMap* _bit_map;
1834 CMSKeepAliveClosure* _keep_alive;
1835 bool _concurrent_precleaning;
1836 public:
1837 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1838 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1839 CMSKeepAliveClosure* keep_alive,
1840 bool cpc):
1841 _collector(collector),
1842 _span(span),
1843 _bit_map(bit_map),
1844 _mark_stack(mark_stack),
1845 _keep_alive(keep_alive),
1846 _concurrent_precleaning(cpc) {
1847 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1848 "Mismatch");
1849 }
1850
1851 void do_void();
1852 };
1853
1854 // A parallel version of CMSDrainMarkingStackClosure above.
1855 class CMSParDrainMarkingStackClosure: public VoidClosure {
1856 CMSCollector* _collector;
1857 MemRegion _span;
1858 OopTaskQueue* _work_queue;
1859 CMSBitMap* _bit_map;
1860 CMSInnerParMarkAndPushClosure _mark_and_push;
1861
1862 public:
1863 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1864 MemRegion span, CMSBitMap* bit_map,
1865 CMSMarkStack* revisit_stack,
1866 OopTaskQueue* work_queue):
1867 _collector(collector),
1868 _span(span),
1869 _bit_map(bit_map),
1870 _work_queue(work_queue),
1871 _mark_and_push(collector, span, bit_map, revisit_stack, work_queue) { }
1872
1873 public:
1874 void trim_queue(uint max);
1875 void do_void();
1876 };
1877
1878 // Allow yielding or short-circuiting of reference list
1879 // prelceaning work.
1880 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1881 CMSCollector* _collector;
1882 void do_yield_work();
1883 public:
1884 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1885 _collector(collector) {}
1886 virtual bool should_return();
1887 };
1888
1889
1890 // Convenience class that locks free list locks for given CMS collector
1891 class FreelistLocker: public StackObj {
1892 private:
1893 CMSCollector* _collector;
1894 public:
1895 FreelistLocker(CMSCollector* collector):
1896 _collector(collector) {
1897 _collector->getFreelistLocks();
1898 }
1899
1900 ~FreelistLocker() {
1901 _collector->releaseFreelistLocks();
1902 }
1903 };
1904
1905 // Mark all dead objects in a given space.
1906 class MarkDeadObjectsClosure: public BlkClosure {
1907 const CMSCollector* _collector;
1908 const CompactibleFreeListSpace* _sp;
1909 CMSBitMap* _live_bit_map;
1910 CMSBitMap* _dead_bit_map;
1911 public:
1912 MarkDeadObjectsClosure(const CMSCollector* collector,
1913 const CompactibleFreeListSpace* sp,
1914 CMSBitMap *live_bit_map,
1915 CMSBitMap *dead_bit_map) :
1916 _collector(collector),
1917 _sp(sp),
1918 _live_bit_map(live_bit_map),
1919 _dead_bit_map(dead_bit_map) {}
1920 size_t do_blk(HeapWord* addr);
1921 };
1922
1923 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1924
1925 public:
1926 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1927 };
1928
1929
1930 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP