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