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