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