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 "logging/log.hpp"
39 #include "memory/freeBlockDictionary.hpp"
40 #include "memory/iterator.hpp"
41 #include "memory/virtualspace.hpp"
42 #include "runtime/mutexLocker.hpp"
43 #include "services/memoryService.hpp"
44 #include "utilities/bitMap.hpp"
45 #include "utilities/stack.hpp"
46
47 // ConcurrentMarkSweepGeneration is in support of a concurrent
48 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
49 // style. We assume, for now, that this generation is always the
50 // seniormost generation and for simplicity
51 // in the first implementation, that this generation is a single compactible
52 // space. Neither of these restrictions appears essential, and will be
53 // relaxed in the future when more time is available to implement the
54 // greater generality (and there's a need for it).
55 //
56 // Concurrent mode failures are currently handled by
57 // means of a sliding mark-compact.
58
59 class AdaptiveSizePolicy;
60 class CMSCollector;
61 class CMSConcMarkingTask;
62 class CMSGCAdaptivePolicyCounters;
63 class CMSTracer;
64 class ConcurrentGCTimer;
65 class ConcurrentMarkSweepGeneration;
66 class ConcurrentMarkSweepPolicy;
67 class ConcurrentMarkSweepThread;
68 class CompactibleFreeListSpace;
69 class FreeChunk;
70 class ParNewGeneration;
71 class PromotionInfo;
72 class ScanMarkedObjectsAgainCarefullyClosure;
73 class TenuredGeneration;
74 class SerialOldTracer;
75
76 // A generic CMS bit map. It's the basis for both the CMS marking bit map
77 // as well as for the mod union table (in each case only a subset of the
78 // methods are used). This is essentially a wrapper around the BitMap class,
79 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
80 // we have _shifter == 0. and for the mod union table we have
81 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
82 // XXX 64-bit issues in BitMap?
83 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
84 friend class VMStructs;
85
86 HeapWord* _bmStartWord; // base address of range covered by map
87 size_t _bmWordSize; // map size (in #HeapWords covered)
88 const int _shifter; // shifts to convert HeapWord to bit position
89 VirtualSpace _virtual_space; // underlying the bit map
90 BitMapView _bm; // the bit map itself
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 "_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) {
312 log_trace(gc)("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", _capacity, _overflows);
313 }
314 _overflows = 0;
315 }
316
317 void record_sample(HeapWord* p, size_t sz) {
318 // For now we do not do anything with the size
319 if (_index < _capacity) {
320 _array[_index++] = p;
321 } else {
322 ++_overflows;
323 assert(_index == _capacity,
324 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
325 "): out of bounds at overflow#" SIZE_FORMAT,
326 _index, _capacity, _overflows);
327 }
328 }
329 };
330
331 //
332 // Timing, allocation and promotion statistics for gc scheduling and incremental
333 // mode pacing. Most statistics are exponential averages.
334 //
335 class CMSStats VALUE_OBJ_CLASS_SPEC {
336 private:
337 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
338
339 // The following are exponential averages with factor alpha:
340 // avg = (100 - alpha) * avg + alpha * cur_sample
341 //
342 // The durations measure: end_time[n] - start_time[n]
343 // The periods measure: start_time[n] - start_time[n-1]
344 //
345 // The cms period and duration include only concurrent collections; time spent
346 // in foreground cms collections due to System.gc() or because of a failure to
347 // keep up are not included.
348 //
349 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
350 // real value, but is used only after the first period. A value of 100 is
351 // used for the first sample so it gets the entire weight.
352 unsigned int _saved_alpha; // 0-100
353 unsigned int _gc0_alpha;
354 unsigned int _cms_alpha;
355
356 double _gc0_duration;
357 double _gc0_period;
358 size_t _gc0_promoted; // bytes promoted per gc0
359 double _cms_duration;
360 double _cms_duration_pre_sweep; // time from initiation to start of sweep
361 double _cms_period;
362 size_t _cms_allocated; // bytes of direct allocation per gc0 period
363
364 // Timers.
365 elapsedTimer _cms_timer;
366 TimeStamp _gc0_begin_time;
367 TimeStamp _cms_begin_time;
368 TimeStamp _cms_end_time;
369
370 // Snapshots of the amount used in the CMS generation.
371 size_t _cms_used_at_gc0_begin;
372 size_t _cms_used_at_gc0_end;
373 size_t _cms_used_at_cms_begin;
374
375 // Used to prevent the duty cycle from being reduced in the middle of a cms
376 // cycle.
377 bool _allow_duty_cycle_reduction;
378
379 enum {
380 _GC0_VALID = 0x1,
381 _CMS_VALID = 0x2,
382 _ALL_VALID = _GC0_VALID | _CMS_VALID
383 };
384
385 unsigned int _valid_bits;
386
387 protected:
388 // In support of adjusting of cms trigger ratios based on history
389 // of concurrent mode failure.
390 double cms_free_adjustment_factor(size_t free) const;
391 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
392
393 public:
394 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
395 unsigned int alpha = CMSExpAvgFactor);
396
397 // Whether or not the statistics contain valid data; higher level statistics
398 // cannot be called until this returns true (they require at least one young
399 // gen and one cms cycle to have completed).
400 bool valid() const;
401
402 // Record statistics.
403 void record_gc0_begin();
404 void record_gc0_end(size_t cms_gen_bytes_used);
405 void record_cms_begin();
406 void record_cms_end();
407
408 // Allow management of the cms timer, which must be stopped/started around
409 // yield points.
410 elapsedTimer& cms_timer() { return _cms_timer; }
411 void start_cms_timer() { _cms_timer.start(); }
412 void stop_cms_timer() { _cms_timer.stop(); }
413
414 // Basic statistics; units are seconds or bytes.
415 double gc0_period() const { return _gc0_period; }
416 double gc0_duration() const { return _gc0_duration; }
417 size_t gc0_promoted() const { return _gc0_promoted; }
418 double cms_period() const { return _cms_period; }
419 double cms_duration() const { return _cms_duration; }
420 size_t cms_allocated() const { return _cms_allocated; }
421
422 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
423
424 // Seconds since the last background cms cycle began or ended.
425 double cms_time_since_begin() const;
426 double cms_time_since_end() const;
427
428 // Higher level statistics--caller must check that valid() returns true before
429 // calling.
430
431 // Returns bytes promoted per second of wall clock time.
432 double promotion_rate() const;
433
434 // Returns bytes directly allocated per second of wall clock time.
435 double cms_allocation_rate() const;
436
437 // Rate at which space in the cms generation is being consumed (sum of the
438 // above two).
439 double cms_consumption_rate() const;
440
441 // Returns an estimate of the number of seconds until the cms generation will
442 // fill up, assuming no collection work is done.
443 double time_until_cms_gen_full() const;
444
445 // Returns an estimate of the number of seconds remaining until
446 // the cms generation collection should start.
447 double time_until_cms_start() const;
448
449 // End of higher level statistics.
450
451 // Debugging.
452 void print_on(outputStream* st) const PRODUCT_RETURN;
453 void print() const { print_on(tty); }
454 };
455
456 // A closure related to weak references processing which
457 // we embed in the CMSCollector, since we need to pass
458 // it to the reference processor for secondary filtering
459 // of references based on reachability of referent;
460 // see role of _is_alive_non_header closure in the
461 // ReferenceProcessor class.
462 // For objects in the CMS generation, this closure checks
463 // if the object is "live" (reachable). Used in weak
464 // reference processing.
465 class CMSIsAliveClosure: public BoolObjectClosure {
466 const MemRegion _span;
467 const CMSBitMap* _bit_map;
468
469 friend class CMSCollector;
470 public:
471 CMSIsAliveClosure(MemRegion span,
472 CMSBitMap* bit_map):
473 _span(span),
474 _bit_map(bit_map) {
475 assert(!span.is_empty(), "Empty span could spell trouble");
476 }
477
478 bool do_object_b(oop obj);
479 };
480
481
482 // Implements AbstractRefProcTaskExecutor for CMS.
483 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
484 public:
485
486 CMSRefProcTaskExecutor(CMSCollector& collector)
487 : _collector(collector)
488 { }
489
490 // Executes a task using worker threads.
491 virtual void execute(ProcessTask& task);
492 virtual void execute(EnqueueTask& task);
493 private:
494 CMSCollector& _collector;
495 };
496
497
498 class CMSCollector: public CHeapObj<mtGC> {
499 friend class VMStructs;
500 friend class ConcurrentMarkSweepThread;
501 friend class ConcurrentMarkSweepGeneration;
502 friend class CompactibleFreeListSpace;
503 friend class CMSParMarkTask;
504 friend class CMSParInitialMarkTask;
505 friend class CMSParRemarkTask;
506 friend class CMSConcMarkingTask;
507 friend class CMSRefProcTaskProxy;
508 friend class CMSRefProcTaskExecutor;
509 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
510 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
511 friend class PushOrMarkClosure; // to access _restart_addr
512 friend class ParPushOrMarkClosure; // to access _restart_addr
513 friend class MarkFromRootsClosure; // -- ditto --
514 // ... and for clearing cards
515 friend class ParMarkFromRootsClosure; // to access _restart_addr
516 // ... and for clearing cards
517 friend class ParConcMarkingClosure; // to access _restart_addr etc.
518 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
519 friend class PushAndMarkVerifyClosure; // -- ditto --
520 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
521 friend class PushAndMarkClosure; // -- ditto --
522 friend class ParPushAndMarkClosure; // -- ditto --
523 friend class CMSKeepAliveClosure; // -- ditto --
524 friend class CMSDrainMarkingStackClosure; // -- ditto --
525 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
526 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
527 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
528 friend class VM_CMS_Operation;
529 friend class VM_CMS_Initial_Mark;
530 friend class VM_CMS_Final_Remark;
531 friend class TraceCMSMemoryManagerStats;
532
533 private:
534 jlong _time_of_last_gc;
535 void update_time_of_last_gc(jlong now) {
536 _time_of_last_gc = now;
537 }
538
539 OopTaskQueueSet* _task_queues;
540
541 // Overflow list of grey objects, threaded through mark-word
542 // Manipulated with CAS in the parallel/multi-threaded case.
543 oopDesc* volatile _overflow_list;
544 // The following array-pair keeps track of mark words
545 // displaced for accommodating overflow list above.
546 // This code will likely be revisited under RFE#4922830.
547 Stack<oop, mtGC> _preserved_oop_stack;
548 Stack<markOop, mtGC> _preserved_mark_stack;
549
550 int* _hash_seed;
551
552 // In support of multi-threaded concurrent phases
553 YieldingFlexibleWorkGang* _conc_workers;
554
555 // Performance Counters
556 CollectorCounters* _gc_counters;
557 CollectorCounters* _cgc_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;
727
728 HeapWord* volatile* _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 // Support for marking stack overflow handling
743 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
744 bool par_take_from_overflow_list(size_t num,
745 OopTaskQueue* to_work_q,
746 int no_of_gc_threads);
747 void push_on_overflow_list(oop p);
748 void par_push_on_overflow_list(oop p);
749 // The following is, obviously, not, in general, "MT-stable"
750 bool overflow_list_is_empty() const;
751
752 void preserve_mark_if_necessary(oop p);
753 void par_preserve_mark_if_necessary(oop p);
754 void preserve_mark_work(oop p, markOop m);
755 void restore_preserved_marks_if_any();
756 NOT_PRODUCT(bool no_preserved_marks() const;)
757 // In support of testing overflow code
758 NOT_PRODUCT(int _overflow_counter;)
759 NOT_PRODUCT(bool simulate_overflow();) // Sequential
760 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
761
762 // CMS work methods
763 void checkpointRootsInitialWork(); // Initial checkpoint work
764
765 // A return value of false indicates failure due to stack overflow
766 bool markFromRootsWork(); // Concurrent marking work
767
768 public: // FIX ME!!! only for testing
769 bool do_marking_st(); // Single-threaded marking
770 bool do_marking_mt(); // Multi-threaded marking
771
772 private:
773
774 // Concurrent precleaning work
775 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen,
776 ScanMarkedObjectsAgainCarefullyClosure* cl);
777 size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen,
778 ScanMarkedObjectsAgainCarefullyClosure* cl);
779 // Does precleaning work, returning a quantity indicative of
780 // the amount of "useful work" done.
781 size_t preclean_work(bool clean_refs, bool clean_survivors);
782 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
783 void abortable_preclean(); // Preclean while looking for possible abort
784 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
785 // Helper function for above; merge-sorts the per-thread plab samples
786 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
787 // Resets (i.e. clears) the per-thread plab sample vectors
788 void reset_survivor_plab_arrays();
789
790 // Final (second) checkpoint work
791 void checkpointRootsFinalWork();
792 // Work routine for parallel version of remark
793 void do_remark_parallel();
794 // Work routine for non-parallel version of remark
795 void do_remark_non_parallel();
796 // Reference processing work routine (during second checkpoint)
797 void refProcessingWork();
798
799 // Concurrent sweeping work
800 void sweepWork(ConcurrentMarkSweepGeneration* old_gen);
801
802 // Concurrent resetting of support data structures
803 void reset_concurrent();
804 // Resetting of support data structures from a STW full GC
805 void reset_stw();
806
807 // Clear _expansion_cause fields of constituent generations
808 void clear_expansion_cause();
809
810 // An auxiliary method used to record the ends of
811 // used regions of each generation to limit the extent of sweep
812 void save_sweep_limits();
813
814 // A work method used by the foreground collector to do
815 // a mark-sweep-compact.
816 void do_compaction_work(bool clear_all_soft_refs);
817
818 // Work methods for reporting concurrent mode interruption or failure
819 bool is_external_interruption();
820 void report_concurrent_mode_interruption();
821
822 // If the background GC is active, acquire control from the background
823 // GC and do the collection.
824 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
825
826 // For synchronizing passing of control from background to foreground
827 // GC. waitForForegroundGC() is called by the background
828 // collector. It if had to wait for a foreground collection,
829 // it returns true and the background collection should assume
830 // that the collection was finished by the foreground
831 // collector.
832 bool waitForForegroundGC();
833
834 size_t block_size_using_printezis_bits(HeapWord* addr) const;
835 size_t block_size_if_printezis_bits(HeapWord* addr) const;
836 HeapWord* next_card_start_after_block(HeapWord* addr) const;
837
838 void setup_cms_unloading_and_verification_state();
839 public:
840 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
841 CardTableRS* ct,
842 ConcurrentMarkSweepPolicy* cp);
843 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
844
845 ReferenceProcessor* ref_processor() { return _ref_processor; }
846 void ref_processor_init();
847
848 Mutex* bitMapLock() const { return _markBitMap.lock(); }
849 static CollectorState abstract_state() { return _collectorState; }
850
851 bool should_abort_preclean() const; // Whether preclean should be aborted.
852 size_t get_eden_used() const;
853 size_t get_eden_capacity() const;
854
855 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
856
857 // Locking checks
858 NOT_PRODUCT(static bool have_cms_token();)
859
860 bool shouldConcurrentCollect();
861
862 void collect(bool full,
863 bool clear_all_soft_refs,
864 size_t size,
865 bool tlab);
866 void collect_in_background(GCCause::Cause cause);
867
868 // In support of ExplicitGCInvokesConcurrent
869 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
870 // Should we unload classes in a particular concurrent cycle?
871 bool should_unload_classes() const {
872 return _should_unload_classes;
873 }
874 void update_should_unload_classes();
875
876 void direct_allocated(HeapWord* start, size_t size);
877
878 // Object is dead if not marked and current phase is sweeping.
879 bool is_dead_obj(oop obj) const;
880
881 // After a promotion (of "start"), do any necessary marking.
882 // If "par", then it's being done by a parallel GC thread.
883 // The last two args indicate if we need precise marking
884 // and if so the size of the object so it can be dirtied
885 // in its entirety.
886 void promoted(bool par, HeapWord* start,
887 bool is_obj_array, size_t obj_size);
888
889 void getFreelistLocks() const;
890 void releaseFreelistLocks() const;
891 bool haveFreelistLocks() const;
892
893 // Adjust size of underlying generation
894 void compute_new_size();
895
896 // GC prologue and epilogue
897 void gc_prologue(bool full);
898 void gc_epilogue(bool full);
899
900 jlong time_of_last_gc(jlong now) {
901 if (_collectorState <= Idling) {
902 // gc not in progress
903 return _time_of_last_gc;
904 } else {
905 // collection in progress
906 return now;
907 }
908 }
909
910 // Support for parallel remark of survivor space
911 void* get_data_recorder(int thr_num);
912 void sample_eden_chunk();
913
914 CMSBitMap* markBitMap() { return &_markBitMap; }
915 void directAllocated(HeapWord* start, size_t size);
916
917 // Main CMS steps and related support
918 void checkpointRootsInitial();
919 bool markFromRoots(); // a return value of false indicates failure
920 // due to stack overflow
921 void preclean();
922 void checkpointRootsFinal();
923 void sweep();
924
925 // Check that the currently executing thread is the expected
926 // one (foreground collector or background collector).
927 static void check_correct_thread_executing() PRODUCT_RETURN;
928
929 NOT_PRODUCT(bool is_cms_reachable(HeapWord* addr);)
930
931 // Performance Counter Support
932 CollectorCounters* counters() { return _gc_counters; }
933 CollectorCounters* cgc_counters() { return _cgc_counters; }
934
935 // Timer stuff
936 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
937 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
938 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
939 jlong timerTicks() { assert(!_timer.is_active(), "Error"); return _timer.ticks(); }
940
941 int yields() { return _numYields; }
942 void resetYields() { _numYields = 0; }
943 void incrementYields() { _numYields++; }
944 void resetNumDirtyCards() { _numDirtyCards = 0; }
945 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
946 size_t numDirtyCards() { return _numDirtyCards; }
947
948 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
949 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
950 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
951 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
952 size_t sweep_count() const { return _sweep_count; }
953 void increment_sweep_count() { _sweep_count++; }
954
955 // Timers/stats for gc scheduling and incremental mode pacing.
956 CMSStats& stats() { return _stats; }
957
958 // Adaptive size policy
959 AdaptiveSizePolicy* size_policy();
960
961 static void print_on_error(outputStream* st);
962
963 // Debugging
964 void verify();
965 bool verify_after_remark();
966 void verify_ok_to_terminate() const PRODUCT_RETURN;
967 void verify_work_stacks_empty() const PRODUCT_RETURN;
968 void verify_overflow_empty() const PRODUCT_RETURN;
969
970 // Convenience methods in support of debugging
971 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
972 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
973
974 // Accessors
975 CMSMarkStack* verification_mark_stack() { return &_markStack; }
976 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
977
978 // Initialization errors
979 bool completed_initialization() { return _completed_initialization; }
980
981 void print_eden_and_survivor_chunk_arrays();
982
983 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
984 };
985
986 class CMSExpansionCause : public AllStatic {
987 public:
988 enum Cause {
989 _no_expansion,
990 _satisfy_free_ratio,
991 _satisfy_promotion,
992 _satisfy_allocation,
993 _allocate_par_lab,
994 _allocate_par_spooling_space,
995 _adaptive_size_policy
996 };
997 // Return a string describing the cause of the expansion.
998 static const char* to_string(CMSExpansionCause::Cause cause);
999 };
1000
1001 class ConcurrentMarkSweepGeneration: public CardGeneration {
1002 friend class VMStructs;
1003 friend class ConcurrentMarkSweepThread;
1004 friend class ConcurrentMarkSweep;
1005 friend class CMSCollector;
1006 protected:
1007 static CMSCollector* _collector; // the collector that collects us
1008 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1009
1010 // Performance Counters
1011 GenerationCounters* _gen_counters;
1012 GSpaceCounters* _space_counters;
1013
1014 // Words directly allocated, used by CMSStats.
1015 size_t _direct_allocated_words;
1016
1017 // Non-product stat counters
1018 NOT_PRODUCT(
1019 size_t _numObjectsPromoted;
1020 size_t _numWordsPromoted;
1021 size_t _numObjectsAllocated;
1022 size_t _numWordsAllocated;
1023 )
1024
1025 // Used for sizing decisions
1026 bool _incremental_collection_failed;
1027 bool incremental_collection_failed() {
1028 return _incremental_collection_failed;
1029 }
1030 void set_incremental_collection_failed() {
1031 _incremental_collection_failed = true;
1032 }
1033 void clear_incremental_collection_failed() {
1034 _incremental_collection_failed = false;
1035 }
1036
1037 // accessors
1038 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1039 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1040
1041 // Accessing spaces
1042 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; }
1043
1044 private:
1045 // For parallel young-gen GC support.
1046 CMSParGCThreadState** _par_gc_thread_states;
1047
1048 // Reason generation was expanded
1049 CMSExpansionCause::Cause _expansion_cause;
1050
1051 // In support of MinChunkSize being larger than min object size
1052 const double _dilatation_factor;
1053
1054 // True if a compacting collection was done.
1055 bool _did_compact;
1056 bool did_compact() { return _did_compact; }
1057
1058 // Fraction of current occupancy at which to start a CMS collection which
1059 // will collect this generation (at least).
1060 double _initiating_occupancy;
1061
1062 protected:
1063 // Shrink generation by specified size (returns false if unable to shrink)
1064 void shrink_free_list_by(size_t bytes);
1065
1066 // Update statistics for GC
1067 virtual void update_gc_stats(Generation* current_generation, bool full);
1068
1069 // Maximum available space in the generation (including uncommitted)
1070 // space.
1071 size_t max_available() const;
1072
1073 // getter and initializer for _initiating_occupancy field.
1074 double initiating_occupancy() const { return _initiating_occupancy; }
1075 void init_initiating_occupancy(intx io, uintx tr);
1076
1077 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause);
1078
1079 void assert_correct_size_change_locking();
1080
1081 public:
1082 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, CardTableRS* ct);
1083
1084 // Accessors
1085 CMSCollector* collector() const { return _collector; }
1086 static void set_collector(CMSCollector* collector) {
1087 assert(_collector == NULL, "already set");
1088 _collector = collector;
1089 }
1090 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1091
1092 Mutex* freelistLock() const;
1093
1094 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1095
1096 void set_did_compact(bool v) { _did_compact = v; }
1097
1098 bool refs_discovery_is_atomic() const { return false; }
1099 bool refs_discovery_is_mt() const {
1100 // Note: CMS does MT-discovery during the parallel-remark
1101 // phases. Use ReferenceProcessorMTMutator to make refs
1102 // discovery MT-safe during such phases or other parallel
1103 // discovery phases in the future. This may all go away
1104 // if/when we decide that refs discovery is sufficiently
1105 // rare that the cost of the CAS's involved is in the
1106 // noise. That's a measurement that should be done, and
1107 // the code simplified if that turns out to be the case.
1108 return ConcGCThreads > 1;
1109 }
1110
1111 // Override
1112 virtual void ref_processor_init();
1113
1114 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1115
1116 // Space enquiries
1117 double occupancy() const { return ((double)used())/((double)capacity()); }
1118 size_t contiguous_available() const;
1119 size_t unsafe_max_alloc_nogc() const;
1120
1121 // over-rides
1122 MemRegion used_region_at_save_marks() const;
1123
1124 // Adjust quantities in the generation affected by
1125 // the compaction.
1126 void reset_after_compaction();
1127
1128 // Allocation support
1129 HeapWord* allocate(size_t size, bool tlab);
1130 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1131 oop promote(oop obj, size_t obj_size);
1132 HeapWord* par_allocate(size_t size, bool tlab) {
1133 return allocate(size, tlab);
1134 }
1135
1136
1137 // Used by CMSStats to track direct allocation. The value is sampled and
1138 // reset after each young gen collection.
1139 size_t direct_allocated_words() const { return _direct_allocated_words; }
1140 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1141
1142 // Overrides for parallel promotion.
1143 virtual oop par_promote(int thread_num,
1144 oop obj, markOop m, size_t word_sz);
1145 virtual void par_promote_alloc_done(int thread_num);
1146 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1147
1148 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1149
1150 // Inform this (old) generation that a promotion failure was
1151 // encountered during a collection of the young generation.
1152 virtual void promotion_failure_occurred();
1153
1154 bool should_collect(bool full, size_t size, bool tlab);
1155 virtual bool should_concurrent_collect() const;
1156 virtual bool is_too_full() const;
1157 void collect(bool full,
1158 bool clear_all_soft_refs,
1159 size_t size,
1160 bool tlab);
1161
1162 HeapWord* expand_and_allocate(size_t word_size,
1163 bool tlab,
1164 bool parallel = false);
1165
1166 // GC prologue and epilogue
1167 void gc_prologue(bool full);
1168 void gc_prologue_work(bool full, bool registerClosure,
1169 ModUnionClosure* modUnionClosure);
1170 void gc_epilogue(bool full);
1171 void gc_epilogue_work(bool full);
1172
1173 // Time since last GC of this generation
1174 jlong time_of_last_gc(jlong now) {
1175 return collector()->time_of_last_gc(now);
1176 }
1177 void update_time_of_last_gc(jlong now) {
1178 collector()-> update_time_of_last_gc(now);
1179 }
1180
1181 // Allocation failure
1182 void shrink(size_t bytes);
1183 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1184 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1185
1186 // Iteration support and related enquiries
1187 void save_marks();
1188 bool no_allocs_since_save_marks();
1189
1190 // Iteration support specific to CMS generations
1191 void save_sweep_limit();
1192
1193 // More iteration support
1194 virtual void oop_iterate(ExtendedOopClosure* cl);
1195 virtual void safe_object_iterate(ObjectClosure* cl);
1196 virtual void object_iterate(ObjectClosure* cl);
1197
1198 // Need to declare the full complement of closures, whether we'll
1199 // override them or not, or get message from the compiler:
1200 // oop_since_save_marks_iterate_nv hides virtual function...
1201 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1202 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1203 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1204
1205 // Smart allocation XXX -- move to CFLSpace?
1206 void setNearLargestChunk();
1207 bool isNearLargestChunk(HeapWord* addr);
1208
1209 // Get the chunk at the end of the space. Delegates to
1210 // the space.
1211 FreeChunk* find_chunk_at_end();
1212
1213 void post_compact();
1214
1215 // Debugging
1216 void prepare_for_verify();
1217 void verify();
1218 void print_statistics() PRODUCT_RETURN;
1219
1220 // Performance Counters support
1221 virtual void update_counters();
1222 virtual void update_counters(size_t used);
1223 void initialize_performance_counters();
1224 CollectorCounters* counters() { return collector()->counters(); }
1225
1226 // Support for parallel remark of survivor space
1227 void* get_data_recorder(int thr_num) {
1228 //Delegate to collector
1229 return collector()->get_data_recorder(thr_num);
1230 }
1231 void sample_eden_chunk() {
1232 //Delegate to collector
1233 return collector()->sample_eden_chunk();
1234 }
1235
1236 // Printing
1237 const char* name() const;
1238 virtual const char* short_name() const { return "CMS"; }
1239 void print() const;
1240
1241 // Resize the generation after a compacting GC. The
1242 // generation can be treated as a contiguous space
1243 // after the compaction.
1244 virtual void compute_new_size();
1245 // Resize the generation after a non-compacting
1246 // collection.
1247 void compute_new_size_free_list();
1248 };
1249
1250 //
1251 // Closures of various sorts used by CMS to accomplish its work
1252 //
1253
1254 // This closure is used to do concurrent marking from the roots
1255 // following the first checkpoint.
1256 class MarkFromRootsClosure: public BitMapClosure {
1257 CMSCollector* _collector;
1258 MemRegion _span;
1259 CMSBitMap* _bitMap;
1260 CMSBitMap* _mut;
1261 CMSMarkStack* _markStack;
1262 bool _yield;
1263 int _skipBits;
1264 HeapWord* _finger;
1265 HeapWord* _threshold;
1266 DEBUG_ONLY(bool _verifying;)
1267
1268 public:
1269 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1270 CMSBitMap* bitMap,
1271 CMSMarkStack* markStack,
1272 bool should_yield, bool verifying = false);
1273 bool do_bit(size_t offset);
1274 void reset(HeapWord* addr);
1275 inline void do_yield_check();
1276
1277 private:
1278 void scanOopsInOop(HeapWord* ptr);
1279 void do_yield_work();
1280 };
1281
1282 // This closure is used to do concurrent multi-threaded
1283 // marking from the roots following the first checkpoint.
1284 // XXX This should really be a subclass of The serial version
1285 // above, but i have not had the time to refactor things cleanly.
1286 class ParMarkFromRootsClosure: public BitMapClosure {
1287 CMSCollector* _collector;
1288 MemRegion _whole_span;
1289 MemRegion _span;
1290 CMSBitMap* _bit_map;
1291 CMSBitMap* _mut;
1292 OopTaskQueue* _work_queue;
1293 CMSMarkStack* _overflow_stack;
1294 int _skip_bits;
1295 HeapWord* _finger;
1296 HeapWord* _threshold;
1297 CMSConcMarkingTask* _task;
1298 public:
1299 ParMarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1300 MemRegion span,
1301 CMSBitMap* bit_map,
1302 OopTaskQueue* work_queue,
1303 CMSMarkStack* overflow_stack);
1304 bool do_bit(size_t offset);
1305 inline void do_yield_check();
1306
1307 private:
1308 void scan_oops_in_oop(HeapWord* ptr);
1309 void do_yield_work();
1310 bool get_work_from_overflow_stack();
1311 };
1312
1313 // The following closures are used to do certain kinds of verification of
1314 // CMS marking.
1315 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1316 CMSCollector* _collector;
1317 MemRegion _span;
1318 CMSBitMap* _verification_bm;
1319 CMSBitMap* _cms_bm;
1320 CMSMarkStack* _mark_stack;
1321 protected:
1322 void do_oop(oop p);
1323 template <class T> inline void do_oop_work(T *p) {
1324 oop obj = oopDesc::load_decode_heap_oop(p);
1325 do_oop(obj);
1326 }
1327 public:
1328 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1329 MemRegion span,
1330 CMSBitMap* verification_bm,
1331 CMSBitMap* cms_bm,
1332 CMSMarkStack* mark_stack);
1333 void do_oop(oop* p);
1334 void do_oop(narrowOop* p);
1335
1336 // Deal with a stack overflow condition
1337 void handle_stack_overflow(HeapWord* lost);
1338 };
1339
1340 class MarkFromRootsVerifyClosure: public BitMapClosure {
1341 CMSCollector* _collector;
1342 MemRegion _span;
1343 CMSBitMap* _verification_bm;
1344 CMSBitMap* _cms_bm;
1345 CMSMarkStack* _mark_stack;
1346 HeapWord* _finger;
1347 PushAndMarkVerifyClosure _pam_verify_closure;
1348 public:
1349 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1350 CMSBitMap* verification_bm,
1351 CMSBitMap* cms_bm,
1352 CMSMarkStack* mark_stack);
1353 bool do_bit(size_t offset);
1354 void reset(HeapWord* addr);
1355 };
1356
1357
1358 // This closure is used to check that a certain set of bits is
1359 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1360 class FalseBitMapClosure: public BitMapClosure {
1361 public:
1362 bool do_bit(size_t offset) {
1363 guarantee(false, "Should not have a 1 bit");
1364 return true;
1365 }
1366 };
1367
1368 // A version of ObjectClosure with "memory" (see _previous_address below)
1369 class UpwardsObjectClosure: public BoolObjectClosure {
1370 HeapWord* _previous_address;
1371 public:
1372 UpwardsObjectClosure() : _previous_address(NULL) { }
1373 void set_previous(HeapWord* addr) { _previous_address = addr; }
1374 HeapWord* previous() { return _previous_address; }
1375 // A return value of "true" can be used by the caller to decide
1376 // if this object's end should *NOT* be recorded in
1377 // _previous_address above.
1378 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1379 };
1380
1381 // This closure is used during the second checkpointing phase
1382 // to rescan the marked objects on the dirty cards in the mod
1383 // union table and the card table proper. It's invoked via
1384 // MarkFromDirtyCardsClosure below. It uses either
1385 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1386 // declared in genOopClosures.hpp to accomplish some of its work.
1387 // In the parallel case the bitMap is shared, so access to
1388 // it needs to be suitably synchronized for updates by embedded
1389 // closures that update it; however, this closure itself only
1390 // reads the bit_map and because it is idempotent, is immune to
1391 // reading stale values.
1392 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1393 #ifdef ASSERT
1394 CMSCollector* _collector;
1395 MemRegion _span;
1396 union {
1397 CMSMarkStack* _mark_stack;
1398 OopTaskQueue* _work_queue;
1399 };
1400 #endif // ASSERT
1401 bool _parallel;
1402 CMSBitMap* _bit_map;
1403 union {
1404 MarkRefsIntoAndScanClosure* _scan_closure;
1405 ParMarkRefsIntoAndScanClosure* _par_scan_closure;
1406 };
1407
1408 public:
1409 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1410 MemRegion span,
1411 ReferenceProcessor* rp,
1412 CMSBitMap* bit_map,
1413 CMSMarkStack* mark_stack,
1414 MarkRefsIntoAndScanClosure* cl):
1415 #ifdef ASSERT
1416 _collector(collector),
1417 _span(span),
1418 _mark_stack(mark_stack),
1419 #endif // ASSERT
1420 _parallel(false),
1421 _bit_map(bit_map),
1422 _scan_closure(cl) { }
1423
1424 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1425 MemRegion span,
1426 ReferenceProcessor* rp,
1427 CMSBitMap* bit_map,
1428 OopTaskQueue* work_queue,
1429 ParMarkRefsIntoAndScanClosure* cl):
1430 #ifdef ASSERT
1431 _collector(collector),
1432 _span(span),
1433 _work_queue(work_queue),
1434 #endif // ASSERT
1435 _parallel(true),
1436 _bit_map(bit_map),
1437 _par_scan_closure(cl) { }
1438
1439 bool do_object_b(oop obj) {
1440 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1441 return false;
1442 }
1443 bool do_object_bm(oop p, MemRegion mr);
1444 };
1445
1446 // This closure is used during the second checkpointing phase
1447 // to rescan the marked objects on the dirty cards in the mod
1448 // union table and the card table proper. It invokes
1449 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1450 // In the parallel case, the bit map is shared and requires
1451 // synchronized access.
1452 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1453 CompactibleFreeListSpace* _space;
1454 ScanMarkedObjectsAgainClosure _scan_cl;
1455 size_t _num_dirty_cards;
1456
1457 public:
1458 MarkFromDirtyCardsClosure(CMSCollector* collector,
1459 MemRegion span,
1460 CompactibleFreeListSpace* space,
1461 CMSBitMap* bit_map,
1462 CMSMarkStack* mark_stack,
1463 MarkRefsIntoAndScanClosure* cl):
1464 _space(space),
1465 _num_dirty_cards(0),
1466 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1467 mark_stack, cl) { }
1468
1469 MarkFromDirtyCardsClosure(CMSCollector* collector,
1470 MemRegion span,
1471 CompactibleFreeListSpace* space,
1472 CMSBitMap* bit_map,
1473 OopTaskQueue* work_queue,
1474 ParMarkRefsIntoAndScanClosure* cl):
1475 _space(space),
1476 _num_dirty_cards(0),
1477 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1478 work_queue, cl) { }
1479
1480 void do_MemRegion(MemRegion mr);
1481 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1482 size_t num_dirty_cards() { return _num_dirty_cards; }
1483 };
1484
1485 // This closure is used in the non-product build to check
1486 // that there are no MemRegions with a certain property.
1487 class FalseMemRegionClosure: public MemRegionClosure {
1488 void do_MemRegion(MemRegion mr) {
1489 guarantee(!mr.is_empty(), "Shouldn't be empty");
1490 guarantee(false, "Should never be here");
1491 }
1492 };
1493
1494 // This closure is used during the precleaning phase
1495 // to "carefully" rescan marked objects on dirty cards.
1496 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1497 // to accomplish some of its work.
1498 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1499 CMSCollector* _collector;
1500 MemRegion _span;
1501 bool _yield;
1502 Mutex* _freelistLock;
1503 CMSBitMap* _bitMap;
1504 CMSMarkStack* _markStack;
1505 MarkRefsIntoAndScanClosure* _scanningClosure;
1506 DEBUG_ONLY(HeapWord* _last_scanned_object;)
1507
1508 public:
1509 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1510 MemRegion span,
1511 CMSBitMap* bitMap,
1512 CMSMarkStack* markStack,
1513 MarkRefsIntoAndScanClosure* cl,
1514 bool should_yield):
1515 _collector(collector),
1516 _span(span),
1517 _yield(should_yield),
1518 _bitMap(bitMap),
1519 _markStack(markStack),
1520 _scanningClosure(cl)
1521 DEBUG_ONLY(COMMA _last_scanned_object(NULL))
1522 { }
1523
1524 void do_object(oop p) {
1525 guarantee(false, "call do_object_careful instead");
1526 }
1527
1528 size_t do_object_careful(oop p) {
1529 guarantee(false, "Unexpected caller");
1530 return 0;
1531 }
1532
1533 size_t do_object_careful_m(oop p, MemRegion mr);
1534
1535 void setFreelistLock(Mutex* m) {
1536 _freelistLock = m;
1537 _scanningClosure->set_freelistLock(m);
1538 }
1539
1540 private:
1541 inline bool do_yield_check();
1542
1543 void do_yield_work();
1544 };
1545
1546 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1547 CMSCollector* _collector;
1548 MemRegion _span;
1549 bool _yield;
1550 CMSBitMap* _bit_map;
1551 CMSMarkStack* _mark_stack;
1552 PushAndMarkClosure* _scanning_closure;
1553 unsigned int _before_count;
1554
1555 public:
1556 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1557 MemRegion span,
1558 CMSBitMap* bit_map,
1559 CMSMarkStack* mark_stack,
1560 PushAndMarkClosure* cl,
1561 unsigned int before_count,
1562 bool should_yield):
1563 _collector(collector),
1564 _span(span),
1565 _yield(should_yield),
1566 _bit_map(bit_map),
1567 _mark_stack(mark_stack),
1568 _scanning_closure(cl),
1569 _before_count(before_count)
1570 { }
1571
1572 void do_object(oop p) {
1573 guarantee(false, "call do_object_careful instead");
1574 }
1575
1576 size_t do_object_careful(oop p);
1577
1578 size_t do_object_careful_m(oop p, MemRegion mr) {
1579 guarantee(false, "Unexpected caller");
1580 return 0;
1581 }
1582
1583 private:
1584 inline void do_yield_check();
1585 void do_yield_work();
1586 };
1587
1588 // This closure is used to accomplish the sweeping work
1589 // after the second checkpoint but before the concurrent reset
1590 // phase.
1591 //
1592 // Terminology
1593 // left hand chunk (LHC) - block of one or more chunks currently being
1594 // coalesced. The LHC is available for coalescing with a new chunk.
1595 // right hand chunk (RHC) - block that is currently being swept that is
1596 // free or garbage that can be coalesced with the LHC.
1597 // _inFreeRange is true if there is currently a LHC
1598 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1599 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1600 // _freeFinger is the address of the current LHC
1601 class SweepClosure: public BlkClosureCareful {
1602 CMSCollector* _collector; // collector doing the work
1603 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1604 CompactibleFreeListSpace* _sp; // Space being swept
1605 HeapWord* _limit;// the address at or above which the sweep should stop
1606 // because we do not expect newly garbage blocks
1607 // eligible for sweeping past that address.
1608 Mutex* _freelistLock; // Free list lock (in space)
1609 CMSBitMap* _bitMap; // Marking bit map (in
1610 // generation)
1611 bool _inFreeRange; // Indicates if we are in the
1612 // midst of a free run
1613 bool _freeRangeInFreeLists;
1614 // Often, we have just found
1615 // a free chunk and started
1616 // a new free range; we do not
1617 // eagerly remove this chunk from
1618 // the free lists unless there is
1619 // a possibility of coalescing.
1620 // When true, this flag indicates
1621 // that the _freeFinger below
1622 // points to a potentially free chunk
1623 // that may still be in the free lists
1624 bool _lastFreeRangeCoalesced;
1625 // free range contains chunks
1626 // coalesced
1627 bool _yield;
1628 // Whether sweeping should be
1629 // done with yields. For instance
1630 // when done by the foreground
1631 // collector we shouldn't yield.
1632 HeapWord* _freeFinger; // When _inFreeRange is set, the
1633 // pointer to the "left hand
1634 // chunk"
1635 size_t _freeRangeSize;
1636 // When _inFreeRange is set, this
1637 // indicates the accumulated size
1638 // of the "left hand chunk"
1639 NOT_PRODUCT(
1640 size_t _numObjectsFreed;
1641 size_t _numWordsFreed;
1642 size_t _numObjectsLive;
1643 size_t _numWordsLive;
1644 size_t _numObjectsAlreadyFree;
1645 size_t _numWordsAlreadyFree;
1646 FreeChunk* _last_fc;
1647 )
1648 private:
1649 // Code that is common to a free chunk or garbage when
1650 // encountered during sweeping.
1651 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1652 // Process a free chunk during sweeping.
1653 void do_already_free_chunk(FreeChunk *fc);
1654 // Work method called when processing an already free or a
1655 // freshly garbage chunk to do a lookahead and possibly a
1656 // preemptive flush if crossing over _limit.
1657 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1658 // Process a garbage chunk during sweeping.
1659 size_t do_garbage_chunk(FreeChunk *fc);
1660 // Process a live chunk during sweeping.
1661 size_t do_live_chunk(FreeChunk* fc);
1662
1663 // Accessors.
1664 HeapWord* freeFinger() const { return _freeFinger; }
1665 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1666 bool inFreeRange() const { return _inFreeRange; }
1667 void set_inFreeRange(bool v) { _inFreeRange = v; }
1668 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1669 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1670 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1671 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1672
1673 // Initialize a free range.
1674 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1675 // Return this chunk to the free lists.
1676 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1677
1678 // Check if we should yield and do so when necessary.
1679 inline void do_yield_check(HeapWord* addr);
1680
1681 // Yield
1682 void do_yield_work(HeapWord* addr);
1683
1684 // Debugging/Printing
1685 void print_free_block_coalesced(FreeChunk* fc) const;
1686
1687 public:
1688 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1689 CMSBitMap* bitMap, bool should_yield);
1690 ~SweepClosure() PRODUCT_RETURN;
1691
1692 size_t do_blk_careful(HeapWord* addr);
1693 void print() const { print_on(tty); }
1694 void print_on(outputStream *st) const;
1695 };
1696
1697 // Closures related to weak references processing
1698
1699 // During CMS' weak reference processing, this is a
1700 // work-routine/closure used to complete transitive
1701 // marking of objects as live after a certain point
1702 // in which an initial set has been completely accumulated.
1703 // This closure is currently used both during the final
1704 // remark stop-world phase, as well as during the concurrent
1705 // precleaning of the discovered reference lists.
1706 class CMSDrainMarkingStackClosure: public VoidClosure {
1707 CMSCollector* _collector;
1708 MemRegion _span;
1709 CMSMarkStack* _mark_stack;
1710 CMSBitMap* _bit_map;
1711 CMSKeepAliveClosure* _keep_alive;
1712 bool _concurrent_precleaning;
1713 public:
1714 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1715 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1716 CMSKeepAliveClosure* keep_alive,
1717 bool cpc):
1718 _collector(collector),
1719 _span(span),
1720 _bit_map(bit_map),
1721 _mark_stack(mark_stack),
1722 _keep_alive(keep_alive),
1723 _concurrent_precleaning(cpc) {
1724 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1725 "Mismatch");
1726 }
1727
1728 void do_void();
1729 };
1730
1731 // A parallel version of CMSDrainMarkingStackClosure above.
1732 class CMSParDrainMarkingStackClosure: public VoidClosure {
1733 CMSCollector* _collector;
1734 MemRegion _span;
1735 OopTaskQueue* _work_queue;
1736 CMSBitMap* _bit_map;
1737 CMSInnerParMarkAndPushClosure _mark_and_push;
1738
1739 public:
1740 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1741 MemRegion span, CMSBitMap* bit_map,
1742 OopTaskQueue* work_queue):
1743 _collector(collector),
1744 _span(span),
1745 _bit_map(bit_map),
1746 _work_queue(work_queue),
1747 _mark_and_push(collector, span, bit_map, work_queue) { }
1748
1749 public:
1750 void trim_queue(uint max);
1751 void do_void();
1752 };
1753
1754 // Allow yielding or short-circuiting of reference list
1755 // precleaning work.
1756 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1757 CMSCollector* _collector;
1758 void do_yield_work();
1759 public:
1760 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1761 _collector(collector) {}
1762 virtual bool should_return();
1763 };
1764
1765
1766 // Convenience class that locks free list locks for given CMS collector
1767 class FreelistLocker: public StackObj {
1768 private:
1769 CMSCollector* _collector;
1770 public:
1771 FreelistLocker(CMSCollector* collector):
1772 _collector(collector) {
1773 _collector->getFreelistLocks();
1774 }
1775
1776 ~FreelistLocker() {
1777 _collector->releaseFreelistLocks();
1778 }
1779 };
1780
1781 // Mark all dead objects in a given space.
1782 class MarkDeadObjectsClosure: public BlkClosure {
1783 const CMSCollector* _collector;
1784 const CompactibleFreeListSpace* _sp;
1785 CMSBitMap* _live_bit_map;
1786 CMSBitMap* _dead_bit_map;
1787 public:
1788 MarkDeadObjectsClosure(const CMSCollector* collector,
1789 const CompactibleFreeListSpace* sp,
1790 CMSBitMap *live_bit_map,
1791 CMSBitMap *dead_bit_map) :
1792 _collector(collector),
1793 _sp(sp),
1794 _live_bit_map(live_bit_map),
1795 _dead_bit_map(dead_bit_map) {}
1796 size_t do_blk(HeapWord* addr);
1797 };
1798
1799 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1800
1801 public:
1802 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1803 };
1804
1805
1806 #endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP