1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP
26 #define SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP
27
28 #include "gc/cms/cmsOopClosures.hpp"
29 #include "gc/cms/gSpaceCounters.hpp"
30 #include "gc/cms/yieldingWorkgroup.hpp"
31 #include "gc/shared/cardGeneration.hpp"
32 #include "gc/shared/gcHeapSummary.hpp"
33 #include "gc/shared/gcStats.hpp"
34 #include "gc/shared/gcWhen.hpp"
35 #include "gc/shared/generationCounters.hpp"
36 #include "gc/shared/space.hpp"
37 #include "gc/shared/taskqueue.hpp"
38 #include "memory/freeBlockDictionary.hpp"
39 #include "memory/iterator.hpp"
40 #include "memory/virtualspace.hpp"
41 #include "runtime/mutexLocker.hpp"
42 #include "services/memoryService.hpp"
43 #include "utilities/bitMap.hpp"
44 #include "utilities/stack.hpp"
45
46 // ConcurrentMarkSweepGeneration is in support of a concurrent
47 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
48 // style. We assume, for now, that this generation is always the
49 // seniormost generation and for simplicity
50 // in the first implementation, that this generation is a single compactible
51 // space. Neither of these restrictions appears essential, and will be
52 // relaxed in the future when more time is available to implement the
53 // greater generality (and there's a need for it).
54 //
55 // Concurrent mode failures are currently handled by
56 // means of a sliding mark-compact.
57
58 class AdaptiveSizePolicy;
59 class CMSCollector;
60 class CMSConcMarkingTask;
61 class CMSGCAdaptivePolicyCounters;
62 class CMSTracer;
63 class ConcurrentGCTimer;
64 class ConcurrentMarkSweepGeneration;
65 class ConcurrentMarkSweepPolicy;
66 class ConcurrentMarkSweepThread;
67 class CompactibleFreeListSpace;
68 class FreeChunk;
69 class ParNewGeneration;
70 class PromotionInfo;
71 class ScanMarkedObjectsAgainCarefullyClosure;
72 class TenuredGeneration;
73 class SerialOldTracer;
74
75 // A generic CMS bit map. It's the basis for both the CMS marking bit map
76 // as well as for the mod union table (in each case only a subset of the
77 // methods are used). This is essentially a wrapper around the BitMap class,
78 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
79 // we have _shifter == 0. and for the mod union table we have
80 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
81 // XXX 64-bit issues in BitMap?
82 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
83 friend class VMStructs;
84
85 HeapWord* _bmStartWord; // base address of range covered by map
86 size_t _bmWordSize; // map size (in #HeapWords covered)
87 const int _shifter; // shifts to convert HeapWord to bit position
88 VirtualSpace _virtual_space; // underlying the bit map
89 BitMap _bm; // the bit map itself
90
91 // If true, allocate the backing bit map so that it covers the YG in
92 // addition to the OG and the PG. This is used to share the
93 // underlying bit map (RAM) between the concurrent collector and the
94 // parallel full GC under CMSParallelFullGC if
95 // ShareCMSMarkBitMapWithParallelFullGC is true.
96 bool _allocate_for_entire_heap;
97 public:
98 Mutex* const _lock; // mutex protecting _bm;
99
100 public:
101 // constructor
102 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name,
103 bool allocate_for_entire_heap = false);
104
105 MemRegion vspace_mr() {
106 assert(_virtual_space.reserved_size() == _virtual_space.committed_size(),
107 "Must be fully committed by initialize().");
108 return MemRegion((HeapWord*)_virtual_space.low_boundary(),
109 (HeapWord*)_virtual_space.high_boundary());
110 }
111
112 // allocates the actual storage for the map
113 bool allocate(MemRegion mr);
114 // field getter
115 Mutex* lock() const { return _lock; }
116 // locking verifier convenience function
117 void assert_locked() const PRODUCT_RETURN;
118
119 // inquiries
120 HeapWord* startWord() const { return _bmStartWord; }
121 size_t sizeInWords() const { return _bmWordSize; }
122 size_t sizeInBits() const { return _bm.size(); }
123 // the following is one past the last word in space
124 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
125
126 // reading marks
127 bool isMarked(HeapWord* addr) const;
128 bool par_isMarked(HeapWord* addr) const; // do not lock checks
129 bool isUnmarked(HeapWord* addr) const;
130 bool isAllClear() const;
131
132 // writing marks
133 void mark(HeapWord* addr);
134 // For marking by parallel GC threads;
135 // returns true if we did, false if another thread did
136 bool par_mark(HeapWord* addr);
137
138 void mark_range(MemRegion mr);
139 void par_mark_range(MemRegion mr);
140 void mark_large_range(MemRegion mr);
141 void par_mark_large_range(MemRegion mr);
142 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
143 void clear_range(MemRegion mr);
144 void par_clear_range(MemRegion mr);
145 void clear_large_range(MemRegion mr);
146 void par_clear_large_range(MemRegion mr);
147 void clear_all();
148 void clear_all_incrementally(); // Not yet implemented!!
149
150 NOT_PRODUCT(
151 // checks the memory region for validity
152 void region_invariant(MemRegion mr);
153 )
154
155 // iteration
156 void iterate(BitMapClosure* cl) {
157 _bm.iterate(cl);
158 }
159 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
160 void dirty_range_iterate_clear(MemRegionClosure* cl);
161 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
162
163 // auxiliary support for iteration
164 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
165 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
166 HeapWord* end_addr) const;
167 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
168 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
169 HeapWord* end_addr) const;
170 MemRegion getAndClearMarkedRegion(HeapWord* addr);
171 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
172 HeapWord* end_addr);
173
174 // conversion utilities
175 HeapWord* offsetToHeapWord(size_t offset) const;
176 size_t heapWordToOffset(HeapWord* addr) const;
177 size_t heapWordDiffToOffsetDiff(size_t diff) const;
178
179 void print_on_error(outputStream* st, const char* prefix) const;
180
181 // debugging
182 // is this address range covered by the bit-map?
183 NOT_PRODUCT(
184 bool covers(MemRegion mr) const;
185 bool covers(HeapWord* start, size_t size = 0) const;
186 )
187 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
188 };
189
190 // Represents a marking stack used by the CMS collector.
191 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
192 class CMSMarkStack: public CHeapObj<mtGC> {
193 friend class CMSCollector; // To get at expansion stats further below.
194
195 VirtualSpace _virtual_space; // Space for the stack
196 oop* _base; // Bottom of stack
197 size_t _index; // One more than last occupied index
198 size_t _capacity; // Max #elements
199 Mutex _par_lock; // An advisory lock used in case of parallel access
200 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run
201
202 protected:
203 size_t _hit_limit; // We hit max stack size limit
204 size_t _failed_double; // We failed expansion before hitting limit
205
206 public:
207 CMSMarkStack():
208 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true,
209 Monitor::_safepoint_check_never),
210 _hit_limit(0),
211 _failed_double(0) {}
212
213 bool allocate(size_t size);
214
215 size_t capacity() const { return _capacity; }
216
217 oop pop() {
218 if (!isEmpty()) {
219 return _base[--_index] ;
220 }
221 return NULL;
222 }
223
224 bool push(oop ptr) {
225 if (isFull()) {
226 return false;
227 } else {
228 _base[_index++] = ptr;
229 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
230 return true;
231 }
232 }
233
234 bool isEmpty() const { return _index == 0; }
235 bool isFull() const {
236 assert(_index <= _capacity, "buffer overflow");
237 return _index == _capacity;
238 }
239
240 size_t length() { return _index; }
241
242 // "Parallel versions" of some of the above
243 oop par_pop() {
244 // lock and pop
245 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
246 return pop();
247 }
248
249 bool par_push(oop ptr) {
250 // lock and push
251 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
252 return push(ptr);
253 }
254
255 // Forcibly reset the stack, losing all of its contents.
256 void reset() {
257 _index = 0;
258 }
259
260 // Expand the stack, typically in response to an overflow condition.
261 void expand();
262
263 // Compute the least valued stack element.
264 oop least_value(HeapWord* low) {
265 oop least = (oop)low;
266 for (size_t i = 0; i < _index; i++) {
267 least = MIN2(least, _base[i]);
268 }
269 return least;
270 }
271
272 // Exposed here to allow stack expansion in || case.
273 Mutex* par_lock() { return &_par_lock; }
274 };
275
276 class CardTableRS;
277 class CMSParGCThreadState;
278
279 class ModUnionClosure: public MemRegionClosure {
280 protected:
281 CMSBitMap* _t;
282 public:
283 ModUnionClosure(CMSBitMap* t): _t(t) { }
284 void do_MemRegion(MemRegion mr);
285 };
286
287 class ModUnionClosurePar: public ModUnionClosure {
288 public:
289 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
290 void do_MemRegion(MemRegion mr);
291 };
292
293 // Survivor Chunk Array in support of parallelization of
294 // Survivor Space rescan.
295 class ChunkArray: public CHeapObj<mtGC> {
296 size_t _index;
297 size_t _capacity;
298 size_t _overflows;
299 HeapWord** _array; // storage for array
300
301 public:
302 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
303 ChunkArray(HeapWord** a, size_t c):
304 _index(0), _capacity(c), _overflows(0), _array(a) {}
305
306 HeapWord** array() { return _array; }
307 void set_array(HeapWord** a) { _array = a; }
308
309 size_t capacity() { return _capacity; }
310 void set_capacity(size_t c) { _capacity = c; }
311
312 size_t end() {
313 assert(_index <= capacity(),
314 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
315 _index, _capacity));
316 return _index;
317 } // exclusive
318
319 HeapWord* nth(size_t n) {
320 assert(n < end(), "Out of bounds access");
321 return _array[n];
322 }
323
324 void reset() {
325 _index = 0;
326 if (_overflows > 0 && PrintCMSStatistics > 1) {
327 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
328 _capacity, _overflows);
329 }
330 _overflows = 0;
331 }
332
333 void record_sample(HeapWord* p, size_t sz) {
334 // For now we do not do anything with the size
335 if (_index < _capacity) {
336 _array[_index++] = p;
337 } else {
338 ++_overflows;
339 assert(_index == _capacity,
340 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
341 "): out of bounds at overflow#" SIZE_FORMAT,
342 _index, _capacity, _overflows));
343 }
344 }
345 };
346
347 //
348 // Timing, allocation and promotion statistics for gc scheduling and incremental
349 // mode pacing. Most statistics are exponential averages.
350 //
351 class CMSStats VALUE_OBJ_CLASS_SPEC {
352 private:
353 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
354
355 // The following are exponential averages with factor alpha:
356 // avg = (100 - alpha) * avg + alpha * cur_sample
357 //
358 // The durations measure: end_time[n] - start_time[n]
359 // The periods measure: start_time[n] - start_time[n-1]
360 //
361 // The cms period and duration include only concurrent collections; time spent
362 // in foreground cms collections due to System.gc() or because of a failure to
363 // keep up are not included.
364 //
365 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
366 // real value, but is used only after the first period. A value of 100 is
367 // used for the first sample so it gets the entire weight.
368 unsigned int _saved_alpha; // 0-100
369 unsigned int _gc0_alpha;
370 unsigned int _cms_alpha;
371
372 double _gc0_duration;
373 double _gc0_period;
374 size_t _gc0_promoted; // bytes promoted per gc0
375 double _cms_duration;
376 double _cms_duration_pre_sweep; // time from initiation to start of sweep
377 double _cms_period;
378 size_t _cms_allocated; // bytes of direct allocation per gc0 period
379
380 // Timers.
381 elapsedTimer _cms_timer;
382 TimeStamp _gc0_begin_time;
383 TimeStamp _cms_begin_time;
384 TimeStamp _cms_end_time;
385
386 // Snapshots of the amount used in the CMS generation.
387 size_t _cms_used_at_gc0_begin;
388 size_t _cms_used_at_gc0_end;
389 size_t _cms_used_at_cms_begin;
390
391 // Used to prevent the duty cycle from being reduced in the middle of a cms
392 // cycle.
393 bool _allow_duty_cycle_reduction;
394
395 enum {
396 _GC0_VALID = 0x1,
397 _CMS_VALID = 0x2,
398 _ALL_VALID = _GC0_VALID | _CMS_VALID
399 };
400
401 unsigned int _valid_bits;
402
403 protected:
404 // In support of adjusting of cms trigger ratios based on history
405 // of concurrent mode failure.
406 double cms_free_adjustment_factor(size_t free) const;
407 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
408
409 public:
410 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
411 unsigned int alpha = CMSExpAvgFactor);
412
413 // Whether or not the statistics contain valid data; higher level statistics
414 // cannot be called until this returns true (they require at least one young
415 // gen and one cms cycle to have completed).
416 bool valid() const;
417
418 // Record statistics.
419 void record_gc0_begin();
420 void record_gc0_end(size_t cms_gen_bytes_used);
421 void record_cms_begin();
422 void record_cms_end();
423
424 // Allow management of the cms timer, which must be stopped/started around
425 // yield points.
426 elapsedTimer& cms_timer() { return _cms_timer; }
427 void start_cms_timer() { _cms_timer.start(); }
428 void stop_cms_timer() { _cms_timer.stop(); }
429
430 // Basic statistics; units are seconds or bytes.
431 double gc0_period() const { return _gc0_period; }
432 double gc0_duration() const { return _gc0_duration; }
433 size_t gc0_promoted() const { return _gc0_promoted; }
434 double cms_period() const { return _cms_period; }
435 double cms_duration() const { return _cms_duration; }
436 size_t cms_allocated() const { return _cms_allocated; }
437
438 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
439
440 // Seconds since the last background cms cycle began or ended.
441 double cms_time_since_begin() const;
442 double cms_time_since_end() const;
443
444 // Higher level statistics--caller must check that valid() returns true before
445 // calling.
446
447 // Returns bytes promoted per second of wall clock time.
448 double promotion_rate() const;
449
450 // Returns bytes directly allocated per second of wall clock time.
451 double cms_allocation_rate() const;
452
453 // Rate at which space in the cms generation is being consumed (sum of the
454 // above two).
455 double cms_consumption_rate() const;
456
457 // Returns an estimate of the number of seconds until the cms generation will
458 // fill up, assuming no collection work is done.
459 double time_until_cms_gen_full() const;
460
461 // Returns an estimate of the number of seconds remaining until
462 // the cms generation collection should start.
463 double time_until_cms_start() const;
464
465 // End of higher level statistics.
466
467 // Debugging.
468 void print_on(outputStream* st) const PRODUCT_RETURN;
469 void print() const { print_on(gclog_or_tty); }
470 };
471
472 // A closure related to weak references processing which
473 // we embed in the CMSCollector, since we need to pass
474 // it to the reference processor for secondary filtering
475 // of references based on reachability of referent;
476 // see role of _is_alive_non_header closure in the
477 // ReferenceProcessor class.
478 // For objects in the CMS generation, this closure checks
479 // if the object is "live" (reachable). Used in weak
480 // reference processing.
481 class CMSIsAliveClosure: public BoolObjectClosure {
482 const MemRegion _span;
483 const CMSBitMap* _bit_map;
484
485 friend class CMSCollector;
486 public:
487 CMSIsAliveClosure(MemRegion span,
488 CMSBitMap* bit_map):
489 _span(span),
490 _bit_map(bit_map) {
491 assert(!span.is_empty(), "Empty span could spell trouble");
492 }
493
494 bool do_object_b(oop obj);
495 };
496
497
498 // Implements AbstractRefProcTaskExecutor for CMS.
499 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
500 public:
501
502 CMSRefProcTaskExecutor(CMSCollector& collector)
503 : _collector(collector)
504 { }
505
506 // Executes a task using worker threads.
507 virtual void execute(ProcessTask& task);
508 virtual void execute(EnqueueTask& task);
509 private:
510 CMSCollector& _collector;
511 };
512
513
514 class CMSCollector: public CHeapObj<mtGC> {
515 friend class VMStructs;
516 friend class ConcurrentMarkSweepThread;
517 friend class ConcurrentMarkSweepGeneration;
518 friend class CompactibleFreeListSpace;
519 friend class CMSParMarkTask;
520 friend class CMSParInitialMarkTask;
521 friend class CMSParRemarkTask;
522 friend class CMSConcMarkingTask;
523 friend class CMSRefProcTaskProxy;
524 friend class CMSRefProcTaskExecutor;
525 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
526 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
527 friend class PushOrMarkClosure; // to access _restart_addr
528 friend class Par_PushOrMarkClosure; // to access _restart_addr
529 friend class MarkFromRootsClosure; // -- ditto --
530 // ... and for clearing cards
531 friend class Par_MarkFromRootsClosure; // to access _restart_addr
532 // ... and for clearing cards
533 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
534 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
535 friend class PushAndMarkVerifyClosure; // -- ditto --
536 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
537 friend class PushAndMarkClosure; // -- ditto --
538 friend class Par_PushAndMarkClosure; // -- ditto --
539 friend class CMSKeepAliveClosure; // -- ditto --
540 friend class CMSDrainMarkingStackClosure; // -- ditto --
541 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
542 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
543 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
544 friend class VM_CMS_Operation;
545 friend class VM_CMS_Initial_Mark;
546 friend class VM_CMS_Final_Remark;
547 friend class TraceCMSMemoryManagerStats;
548
549 private:
550 jlong _time_of_last_gc;
551 void update_time_of_last_gc(jlong now) {
552 _time_of_last_gc = now;
553 }
554
555 OopTaskQueueSet* _task_queues;
556
557 // Overflow list of grey objects, threaded through mark-word
558 // Manipulated with CAS in the parallel/multi-threaded case.
559 oop _overflow_list;
560 // The following array-pair keeps track of mark words
561 // displaced for accommodating overflow list above.
562 // This code will likely be revisited under RFE#4922830.
563 Stack<oop, mtGC> _preserved_oop_stack;
564 Stack<markOop, mtGC> _preserved_mark_stack;
565
566 int* _hash_seed;
567
568 // In support of multi-threaded concurrent phases
569 YieldingFlexibleWorkGang* _conc_workers;
570
571 // Performance Counters
572 CollectorCounters* _gc_counters;
573
574 // Initialization Errors
575 bool _completed_initialization;
576
577 // In support of ExplicitGCInvokesConcurrent
578 static bool _full_gc_requested;
579 static GCCause::Cause _full_gc_cause;
580 unsigned int _collection_count_start;
581
582 // Should we unload classes this concurrent cycle?
583 bool _should_unload_classes;
584 unsigned int _concurrent_cycles_since_last_unload;
585 unsigned int concurrent_cycles_since_last_unload() const {
586 return _concurrent_cycles_since_last_unload;
587 }
588 // Did we (allow) unload classes in the previous concurrent cycle?
589 bool unloaded_classes_last_cycle() const {
590 return concurrent_cycles_since_last_unload() == 0;
591 }
592 // Root scanning options for perm gen
593 int _roots_scanning_options;
594 int roots_scanning_options() const { return _roots_scanning_options; }
595 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
596 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
597
598 // Verification support
599 CMSBitMap _verification_mark_bm;
600 void verify_after_remark_work_1();
601 void verify_after_remark_work_2();
602
603 // True if any verification flag is on.
604 bool _verifying;
605 bool verifying() const { return _verifying; }
606 void set_verifying(bool v) { _verifying = v; }
607
608 // Collector policy
609 ConcurrentMarkSweepPolicy* _collector_policy;
610 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
611
612 void set_did_compact(bool v);
613
614 // XXX Move these to CMSStats ??? FIX ME !!!
615 elapsedTimer _inter_sweep_timer; // Time between sweeps
616 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
617 // Padded decaying average estimates of the above
618 AdaptivePaddedAverage _inter_sweep_estimate;
619 AdaptivePaddedAverage _intra_sweep_estimate;
620
621 CMSTracer* _gc_tracer_cm;
622 ConcurrentGCTimer* _gc_timer_cm;
623
624 bool _cms_start_registered;
625
626 GCHeapSummary _last_heap_summary;
627 MetaspaceSummary _last_metaspace_summary;
628
629 void register_gc_start(GCCause::Cause cause);
630 void register_gc_end();
631 void save_heap_summary();
632 void report_heap_summary(GCWhen::Type when);
633
634 protected:
635 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
636 MemRegion _span; // Span covering above two
637 CardTableRS* _ct; // Card table
638
639 // CMS marking support structures
640 CMSBitMap _markBitMap;
641 CMSBitMap _modUnionTable;
642 CMSMarkStack _markStack;
643
644 HeapWord* _restart_addr; // In support of marking stack overflow
645 void lower_restart_addr(HeapWord* low);
646
647 // Counters in support of marking stack / work queue overflow handling:
648 // a non-zero value indicates certain types of overflow events during
649 // the current CMS cycle and could lead to stack resizing efforts at
650 // an opportune future time.
651 size_t _ser_pmc_preclean_ovflw;
652 size_t _ser_pmc_remark_ovflw;
653 size_t _par_pmc_remark_ovflw;
654 size_t _ser_kac_preclean_ovflw;
655 size_t _ser_kac_ovflw;
656 size_t _par_kac_ovflw;
657 NOT_PRODUCT(ssize_t _num_par_pushes;)
658
659 // ("Weak") Reference processing support.
660 ReferenceProcessor* _ref_processor;
661 CMSIsAliveClosure _is_alive_closure;
662 // Keep this textually after _markBitMap and _span; c'tor dependency.
663
664 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
665 ModUnionClosurePar _modUnionClosurePar;
666
667 // CMS abstract state machine
668 // initial_state: Idling
669 // next_state(Idling) = {Marking}
670 // next_state(Marking) = {Precleaning, Sweeping}
671 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
672 // next_state(AbortablePreclean) = {FinalMarking}
673 // next_state(FinalMarking) = {Sweeping}
674 // next_state(Sweeping) = {Resizing}
675 // next_state(Resizing) = {Resetting}
676 // next_state(Resetting) = {Idling}
677 // The numeric values below are chosen so that:
678 // . _collectorState <= Idling == post-sweep && pre-mark
679 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
680 // precleaning || abortablePrecleanb
681 public:
682 enum CollectorState {
683 Resizing = 0,
684 Resetting = 1,
685 Idling = 2,
686 InitialMarking = 3,
687 Marking = 4,
688 Precleaning = 5,
689 AbortablePreclean = 6,
690 FinalMarking = 7,
691 Sweeping = 8
692 };
693 protected:
694 static CollectorState _collectorState;
695
696 // State related to prologue/epilogue invocation for my generations
697 bool _between_prologue_and_epilogue;
698
699 // Signaling/State related to coordination between fore- and background GC
700 // Note: When the baton has been passed from background GC to foreground GC,
701 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
702 static bool _foregroundGCIsActive; // true iff foreground collector is active or
703 // wants to go active
704 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
705 // yet passed the baton to the foreground GC
706
707 // Support for CMSScheduleRemark (abortable preclean)
708 bool _abort_preclean;
709 bool _start_sampling;
710
711 int _numYields;
712 size_t _numDirtyCards;
713 size_t _sweep_count;
714
715 // Occupancy used for bootstrapping stats
716 double _bootstrap_occupancy;
717
718 // Timer
719 elapsedTimer _timer;
720
721 // Timing, allocation and promotion statistics, used for scheduling.
722 CMSStats _stats;
723
724 enum CMS_op_type {
725 CMS_op_checkpointRootsInitial,
726 CMS_op_checkpointRootsFinal
727 };
728
729 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
730 bool stop_world_and_do(CMS_op_type op);
731
732 OopTaskQueueSet* task_queues() { return _task_queues; }
733 int* hash_seed(int i) { return &_hash_seed[i]; }
734 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
735
736 // Support for parallelizing Eden rescan in CMS remark phase
737 void sample_eden(); // ... sample Eden space top
738
739 private:
740 // Support for parallelizing young gen rescan in CMS remark phase
741 ParNewGeneration* _young_gen; // the younger gen
742
743 HeapWord** _top_addr; // ... Top of Eden
744 HeapWord** _end_addr; // ... End of Eden
745 Mutex* _eden_chunk_lock;
746 HeapWord** _eden_chunk_array; // ... Eden partitioning array
747 size_t _eden_chunk_index; // ... top (exclusive) of array
748 size_t _eden_chunk_capacity; // ... max entries in array
749
750 // Support for parallelizing survivor space rescan
751 HeapWord** _survivor_chunk_array;
752 size_t _survivor_chunk_index;
753 size_t _survivor_chunk_capacity;
754 size_t* _cursor;
755 ChunkArray* _survivor_plab_array;
756
757 // A bounded minimum size of PLABs, should not return too small values since
758 // this will affect the size of the data structures used for parallel young gen rescan
759 size_t plab_sample_minimum_size();
760
761 // Support for marking stack overflow handling
762 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
763 bool par_take_from_overflow_list(size_t num,
764 OopTaskQueue* to_work_q,
765 int no_of_gc_threads);
766 void push_on_overflow_list(oop p);
767 void par_push_on_overflow_list(oop p);
768 // The following is, obviously, not, in general, "MT-stable"
769 bool overflow_list_is_empty() const;
770
771 void preserve_mark_if_necessary(oop p);
772 void par_preserve_mark_if_necessary(oop p);
773 void preserve_mark_work(oop p, markOop m);
774 void restore_preserved_marks_if_any();
775 NOT_PRODUCT(bool no_preserved_marks() const;)
776 // In support of testing overflow code
777 NOT_PRODUCT(int _overflow_counter;)
778 NOT_PRODUCT(bool simulate_overflow();) // Sequential
779 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
780
781 // CMS work methods
782 void checkpointRootsInitialWork(); // Initial checkpoint work
783
784 // A return value of false indicates failure due to stack overflow
785 bool markFromRootsWork(); // Concurrent marking work
786
787 public: // FIX ME!!! only for testing
788 bool do_marking_st(); // Single-threaded marking
789 bool do_marking_mt(); // Multi-threaded marking
790
791 private:
792
793 // Concurrent precleaning work
794 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
795 ScanMarkedObjectsAgainCarefullyClosure* cl);
796 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
797 ScanMarkedObjectsAgainCarefullyClosure* cl);
798 // Does precleaning work, returning a quantity indicative of
799 // the amount of "useful work" done.
800 size_t preclean_work(bool clean_refs, bool clean_survivors);
801 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
802 void abortable_preclean(); // Preclean while looking for possible abort
803 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
804 // Helper function for above; merge-sorts the per-thread plab samples
805 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
806 // Resets (i.e. clears) the per-thread plab sample vectors
807 void reset_survivor_plab_arrays();
808
809 // Final (second) checkpoint work
810 void checkpointRootsFinalWork();
811 // Work routine for parallel version of remark
812 void do_remark_parallel();
813 // Work routine for non-parallel version of remark
814 void do_remark_non_parallel();
815 // Reference processing work routine (during second checkpoint)
816 void refProcessingWork();
817
818 // Concurrent sweeping work
819 void sweepWork(ConcurrentMarkSweepGeneration* gen);
820
821 // (Concurrent) resetting of support data structures
822 void reset(bool concurrent);
823
824 // Clear _expansion_cause fields of constituent generations
825 void clear_expansion_cause();
826
827 // An auxiliary method used to record the ends of
828 // used regions of each generation to limit the extent of sweep
829 void save_sweep_limits();
830
831 // A work method used by the foreground collector to do
832 // a mark-sweep-compact.
833 void do_compaction_work(bool clear_all_soft_refs);
834
835 // Work methods for reporting concurrent mode interruption or failure
836 bool is_external_interruption();
837 void report_concurrent_mode_interruption();
838
839 // If the background GC is active, acquire control from the background
840 // GC and do the collection.
841 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
842
843 // For synchronizing passing of control from background to foreground
844 // GC. waitForForegroundGC() is called by the background
845 // collector. It if had to wait for a foreground collection,
846 // it returns true and the background collection should assume
847 // that the collection was finished by the foreground
848 // collector.
849 bool waitForForegroundGC();
850
851 size_t block_size_using_printezis_bits(HeapWord* addr) const;
852 size_t block_size_if_printezis_bits(HeapWord* addr) const;
853 HeapWord* next_card_start_after_block(HeapWord* addr) const;
854
855 void setup_cms_unloading_and_verification_state();
856 public:
857 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
858 CardTableRS* ct,
859 ConcurrentMarkSweepPolicy* cp);
860 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
861
862 ReferenceProcessor* ref_processor() { return _ref_processor; }
863 void ref_processor_init();
864
865 Mutex* bitMapLock() const { return _markBitMap.lock(); }
866 static CollectorState abstract_state() { return _collectorState; }
867
868 bool should_abort_preclean() const; // Whether preclean should be aborted.
869 size_t get_eden_used() const;
870 size_t get_eden_capacity() const;
871
872 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
873
874 // Locking checks
875 NOT_PRODUCT(static bool have_cms_token();)
876
877 bool shouldConcurrentCollect();
878
879 void collect(bool full,
880 bool clear_all_soft_refs,
881 size_t size,
882 bool tlab);
883 void collect_in_background(GCCause::Cause cause);
884
885 // In support of ExplicitGCInvokesConcurrent
886 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
887 // Should we unload classes in a particular concurrent cycle?
888 bool should_unload_classes() const {
889 return _should_unload_classes;
890 }
891 void update_should_unload_classes();
892
893 void direct_allocated(HeapWord* start, size_t size);
894
895 // Object is dead if not marked and current phase is sweeping.
896 bool is_dead_obj(oop obj) const;
897
898 // After a promotion (of "start"), do any necessary marking.
899 // If "par", then it's being done by a parallel GC thread.
900 // The last two args indicate if we need precise marking
901 // and if so the size of the object so it can be dirtied
902 // in its entirety.
903 void promoted(bool par, HeapWord* start,
904 bool is_obj_array, size_t obj_size);
905
906 void getFreelistLocks() const;
907 void releaseFreelistLocks() const;
908 bool haveFreelistLocks() const;
909
910 // Adjust size of underlying generation
911 void compute_new_size();
912
913 // GC prologue and epilogue
914 void gc_prologue(bool full);
915 void gc_epilogue(bool full);
916
917 jlong time_of_last_gc(jlong now) {
918 if (_collectorState <= Idling) {
919 // gc not in progress
920 return _time_of_last_gc;
921 } else {
922 // collection in progress
923 return now;
924 }
925 }
926
927 // Support for parallel remark of survivor space
928 void* get_data_recorder(int thr_num);
929 void sample_eden_chunk();
930
931 CMSBitMap* markBitMap() { return &_markBitMap; }
932 void directAllocated(HeapWord* start, size_t size);
933
934 // Main CMS steps and related support
935 void checkpointRootsInitial();
936 bool markFromRoots(); // a return value of false indicates failure
937 // due to stack overflow
938 void preclean();
939 void checkpointRootsFinal();
940 void sweep();
941
942 // Check that the currently executing thread is the expected
943 // one (foreground collector or background collector).
944 static void check_correct_thread_executing() PRODUCT_RETURN;
945
946 bool is_cms_reachable(HeapWord* addr);
947
948 // Performance Counter Support
949 CollectorCounters* counters() { return _gc_counters; }
950
951 // Timer stuff
952 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
953 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
954 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
955 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
956
957 int yields() { return _numYields; }
958 void resetYields() { _numYields = 0; }
959 void incrementYields() { _numYields++; }
960 void resetNumDirtyCards() { _numDirtyCards = 0; }
961 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
962 size_t numDirtyCards() { return _numDirtyCards; }
963
964 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
965 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
966 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
967 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
968 size_t sweep_count() const { return _sweep_count; }
969 void increment_sweep_count() { _sweep_count++; }
970
971 // Timers/stats for gc scheduling and incremental mode pacing.
972 CMSStats& stats() { return _stats; }
973
974 // Adaptive size policy
975 AdaptiveSizePolicy* size_policy();
976
977 static void print_on_error(outputStream* st);
978
979 // Debugging
980 void verify();
981 bool verify_after_remark(bool silent = VerifySilently);
982 void verify_ok_to_terminate() const PRODUCT_RETURN;
983 void verify_work_stacks_empty() const PRODUCT_RETURN;
984 void verify_overflow_empty() const PRODUCT_RETURN;
985
986 // Convenience methods in support of debugging
987 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
988 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
989
990 // Accessors
991 CMSMarkStack* verification_mark_stack() { return &_markStack; }
992 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
993
994 // Initialization errors
995 bool completed_initialization() { return _completed_initialization; }
996
997 void print_eden_and_survivor_chunk_arrays();
998 };
999
1000 class CMSExpansionCause : public AllStatic {
1001 public:
1002 enum Cause {
1003 _no_expansion,
1004 _satisfy_free_ratio,
1005 _satisfy_promotion,
1006 _satisfy_allocation,
1007 _allocate_par_lab,
1008 _allocate_par_spooling_space,
1009 _adaptive_size_policy
1010 };
1011 // Return a string describing the cause of the expansion.
1012 static const char* to_string(CMSExpansionCause::Cause cause);
1013 };
1014
1015 class ConcurrentMarkSweepGeneration: public CardGeneration {
1016 friend class VMStructs;
1017 friend class ConcurrentMarkSweepThread;
1018 friend class ConcurrentMarkSweep;
1019 friend class CMSCollector;
1020 protected:
1021 static CMSCollector* _collector; // the collector that collects us
1022 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1023
1024 // Performance Counters
1025 GenerationCounters* _gen_counters;
1026 GSpaceCounters* _space_counters;
1027
1028 // Words directly allocated, used by CMSStats.
1029 size_t _direct_allocated_words;
1030
1031 // Non-product stat counters
1032 NOT_PRODUCT(
1033 size_t _numObjectsPromoted;
1034 size_t _numWordsPromoted;
1035 size_t _numObjectsAllocated;
1036 size_t _numWordsAllocated;
1037 )
1038
1039 // Used for sizing decisions
1040 bool _incremental_collection_failed;
1041 bool incremental_collection_failed() {
1042 return _incremental_collection_failed;
1043 }
1044 void set_incremental_collection_failed() {
1045 _incremental_collection_failed = true;
1046 }
1047 void clear_incremental_collection_failed() {
1048 _incremental_collection_failed = false;
1049 }
1050
1051 // accessors
1052 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1053 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1054
1055 // Accessing spaces
1056 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; }
1057
1058 private:
1059 // For parallel young-gen GC support.
1060 CMSParGCThreadState** _par_gc_thread_states;
1061
1062 // Reason generation was expanded
1063 CMSExpansionCause::Cause _expansion_cause;
1064
1065 // In support of MinChunkSize being larger than min object size
1066 const double _dilatation_factor;
1067
1068 // True if a compacting collection was done.
1069 bool _did_compact;
1070 bool did_compact() { return _did_compact; }
1071
1072 // Fraction of current occupancy at which to start a CMS collection which
1073 // will collect this generation (at least).
1074 double _initiating_occupancy;
1075
1076 protected:
1077 // Shrink generation by specified size (returns false if unable to shrink)
1078 void shrink_free_list_by(size_t bytes);
1079
1080 // Update statistics for GC
1081 virtual void update_gc_stats(Generation* current_generation, bool full);
1082
1083 // Maximum available space in the generation (including uncommitted)
1084 // space.
1085 size_t max_available() const;
1086
1087 // getter and initializer for _initiating_occupancy field.
1088 double initiating_occupancy() const { return _initiating_occupancy; }
1089 void init_initiating_occupancy(intx io, uintx tr);
1090
1091 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause);
1092
1093 void assert_correct_size_change_locking();
1094
1095 public:
1096 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1097 CardTableRS* ct,
1098 bool use_adaptive_freelists,
1099 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1100
1101 // Accessors
1102 static CMSCollector* collector() { return _collector; }
1103 static void set_collector(CMSCollector* collector) {
1104 assert(_collector == NULL, "already set");
1105 _collector = collector;
1106 }
1107 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1108
1109 Mutex* freelistLock() const;
1110
1111 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1112
1113 void set_did_compact(bool v) { _did_compact = v; }
1114
1115 bool refs_discovery_is_atomic() const { return false; }
1116 bool refs_discovery_is_mt() const {
1117 // Note: CMS does MT-discovery during the parallel-remark
1118 // phases. Use ReferenceProcessorMTMutator to make refs
1119 // discovery MT-safe during such phases or other parallel
1120 // discovery phases in the future. This may all go away
1121 // if/when we decide that refs discovery is sufficiently
1122 // rare that the cost of the CAS's involved is in the
1123 // noise. That's a measurement that should be done, and
1124 // the code simplified if that turns out to be the case.
1125 return ConcGCThreads > 1;
1126 }
1127
1128 // Override
1129 virtual void ref_processor_init();
1130
1131 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1132
1133 // Space enquiries
1134 double occupancy() const { return ((double)used())/((double)capacity()); }
1135 size_t contiguous_available() const;
1136 size_t unsafe_max_alloc_nogc() const;
1137
1138 // over-rides
1139 MemRegion used_region_at_save_marks() const;
1140
1141 // Does a "full" (forced) collection invoked on this generation collect
1142 // all younger generations as well? Note that the second conjunct is a
1143 // hack to allow the collection of the younger gen first if the flag is
1144 // set.
1145 virtual bool full_collects_younger_generations() const {
1146 return !ScavengeBeforeFullGC;
1147 }
1148
1149 // Adjust quantities in the generation affected by
1150 // the compaction.
1151 void reset_after_compaction();
1152
1153 // Allocation support
1154 HeapWord* allocate(size_t size, bool tlab);
1155 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1156 oop promote(oop obj, size_t obj_size);
1157 HeapWord* par_allocate(size_t size, bool tlab) {
1158 return allocate(size, tlab);
1159 }
1160
1161
1162 // Used by CMSStats to track direct allocation. The value is sampled and
1163 // reset after each young gen collection.
1164 size_t direct_allocated_words() const { return _direct_allocated_words; }
1165 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1166
1167 // Overrides for parallel promotion.
1168 virtual oop par_promote(int thread_num,
1169 oop obj, markOop m, size_t word_sz);
1170 virtual void par_promote_alloc_done(int thread_num);
1171 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1172
1173 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1174
1175 // Inform this (non-young) generation that a promotion failure was
1176 // encountered during a collection of a younger generation that
1177 // promotes into this generation.
1178 virtual void promotion_failure_occurred();
1179
1180 bool should_collect(bool full, size_t size, bool tlab);
1181 virtual bool should_concurrent_collect() const;
1182 virtual bool is_too_full() const;
1183 void collect(bool full,
1184 bool clear_all_soft_refs,
1185 size_t size,
1186 bool tlab);
1187
1188 HeapWord* expand_and_allocate(size_t word_size,
1189 bool tlab,
1190 bool parallel = false);
1191
1192 // GC prologue and epilogue
1193 void gc_prologue(bool full);
1194 void gc_prologue_work(bool full, bool registerClosure,
1195 ModUnionClosure* modUnionClosure);
1196 void gc_epilogue(bool full);
1197 void gc_epilogue_work(bool full);
1198
1199 // Time since last GC of this generation
1200 jlong time_of_last_gc(jlong now) {
1201 return collector()->time_of_last_gc(now);
1202 }
1203 void update_time_of_last_gc(jlong now) {
1204 collector()-> update_time_of_last_gc(now);
1205 }
1206
1207 // Allocation failure
1208 void shrink(size_t bytes);
1209 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1210 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1211
1212 // Iteration support and related enquiries
1213 void save_marks();
1214 bool no_allocs_since_save_marks();
1215
1216 // Iteration support specific to CMS generations
1217 void save_sweep_limit();
1218
1219 // More iteration support
1220 virtual void oop_iterate(ExtendedOopClosure* cl);
1221 virtual void safe_object_iterate(ObjectClosure* cl);
1222 virtual void object_iterate(ObjectClosure* cl);
1223
1224 // Need to declare the full complement of closures, whether we'll
1225 // override them or not, or get message from the compiler:
1226 // oop_since_save_marks_iterate_nv hides virtual function...
1227 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1228 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1229 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1230
1231 // Smart allocation XXX -- move to CFLSpace?
1232 void setNearLargestChunk();
1233 bool isNearLargestChunk(HeapWord* addr);
1234
1235 // Get the chunk at the end of the space. Delegates to
1236 // the space.
1237 FreeChunk* find_chunk_at_end();
1238
1239 void post_compact();
1240
1241 // Debugging
1242 void prepare_for_verify();
1243 void verify();
1244 void print_statistics() PRODUCT_RETURN;
1245
1246 // Performance Counters support
1247 virtual void update_counters();
1248 virtual void update_counters(size_t used);
1249 void initialize_performance_counters();
1250 CollectorCounters* counters() { return collector()->counters(); }
1251
1252 // Support for parallel remark of survivor space
1253 void* get_data_recorder(int thr_num) {
1254 //Delegate to collector
1255 return collector()->get_data_recorder(thr_num);
1256 }
1257 void sample_eden_chunk() {
1258 //Delegate to collector
1259 return collector()->sample_eden_chunk();
1260 }
1261
1262 // Printing
1263 const char* name() const;
1264 virtual const char* short_name() const { return "CMS"; }
1265 void print() const;
1266 void printOccupancy(const char* s);
1267
1268 // Resize the generation after a compacting GC. The
1269 // generation can be treated as a contiguous space
1270 // after the compaction.
1271 virtual void compute_new_size();
1272 // Resize the generation after a non-compacting
1273 // collection.
1274 void compute_new_size_free_list();
1275 };
1276
1277 //
1278 // Closures of various sorts used by CMS to accomplish its work
1279 //
1280
1281 // This closure is used to do concurrent marking from the roots
1282 // following the first checkpoint.
1283 class MarkFromRootsClosure: public BitMapClosure {
1284 CMSCollector* _collector;
1285 MemRegion _span;
1286 CMSBitMap* _bitMap;
1287 CMSBitMap* _mut;
1288 CMSMarkStack* _markStack;
1289 bool _yield;
1290 int _skipBits;
1291 HeapWord* _finger;
1292 HeapWord* _threshold;
1293 DEBUG_ONLY(bool _verifying;)
1294
1295 public:
1296 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1297 CMSBitMap* bitMap,
1298 CMSMarkStack* markStack,
1299 bool should_yield, bool verifying = false);
1300 bool do_bit(size_t offset);
1301 void reset(HeapWord* addr);
1302 inline void do_yield_check();
1303
1304 private:
1305 void scanOopsInOop(HeapWord* ptr);
1306 void do_yield_work();
1307 };
1308
1309 // This closure is used to do concurrent multi-threaded
1310 // marking from the roots following the first checkpoint.
1311 // XXX This should really be a subclass of The serial version
1312 // above, but i have not had the time to refactor things cleanly.
1313 class Par_MarkFromRootsClosure: public BitMapClosure {
1314 CMSCollector* _collector;
1315 MemRegion _whole_span;
1316 MemRegion _span;
1317 CMSBitMap* _bit_map;
1318 CMSBitMap* _mut;
1319 OopTaskQueue* _work_queue;
1320 CMSMarkStack* _overflow_stack;
1321 int _skip_bits;
1322 HeapWord* _finger;
1323 HeapWord* _threshold;
1324 CMSConcMarkingTask* _task;
1325 public:
1326 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1327 MemRegion span,
1328 CMSBitMap* bit_map,
1329 OopTaskQueue* work_queue,
1330 CMSMarkStack* overflow_stack);
1331 bool do_bit(size_t offset);
1332 inline void do_yield_check();
1333
1334 private:
1335 void scan_oops_in_oop(HeapWord* ptr);
1336 void do_yield_work();
1337 bool get_work_from_overflow_stack();
1338 };
1339
1340 // The following closures are used to do certain kinds of verification of
1341 // CMS marking.
1342 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1343 CMSCollector* _collector;
1344 MemRegion _span;
1345 CMSBitMap* _verification_bm;
1346 CMSBitMap* _cms_bm;
1347 CMSMarkStack* _mark_stack;
1348 protected:
1349 void do_oop(oop p);
1350 template <class T> inline void do_oop_work(T *p) {
1351 oop obj = oopDesc::load_decode_heap_oop(p);
1352 do_oop(obj);
1353 }
1354 public:
1355 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1356 MemRegion span,
1357 CMSBitMap* verification_bm,
1358 CMSBitMap* cms_bm,
1359 CMSMarkStack* mark_stack);
1360 void do_oop(oop* p);
1361 void do_oop(narrowOop* p);
1362
1363 // Deal with a stack overflow condition
1364 void handle_stack_overflow(HeapWord* lost);
1365 };
1366
1367 class MarkFromRootsVerifyClosure: public BitMapClosure {
1368 CMSCollector* _collector;
1369 MemRegion _span;
1370 CMSBitMap* _verification_bm;
1371 CMSBitMap* _cms_bm;
1372 CMSMarkStack* _mark_stack;
1373 HeapWord* _finger;
1374 PushAndMarkVerifyClosure _pam_verify_closure;
1375 public:
1376 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1377 CMSBitMap* verification_bm,
1378 CMSBitMap* cms_bm,
1379 CMSMarkStack* mark_stack);
1380 bool do_bit(size_t offset);
1381 void reset(HeapWord* addr);
1382 };
1383
1384
1385 // This closure is used to check that a certain set of bits is
1386 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1387 class FalseBitMapClosure: public BitMapClosure {
1388 public:
1389 bool do_bit(size_t offset) {
1390 guarantee(false, "Should not have a 1 bit");
1391 return true;
1392 }
1393 };
1394
1395 // A version of ObjectClosure with "memory" (see _previous_address below)
1396 class UpwardsObjectClosure: public BoolObjectClosure {
1397 HeapWord* _previous_address;
1398 public:
1399 UpwardsObjectClosure() : _previous_address(NULL) { }
1400 void set_previous(HeapWord* addr) { _previous_address = addr; }
1401 HeapWord* previous() { return _previous_address; }
1402 // A return value of "true" can be used by the caller to decide
1403 // if this object's end should *NOT* be recorded in
1404 // _previous_address above.
1405 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1406 };
1407
1408 // This closure is used during the second checkpointing phase
1409 // to rescan the marked objects on the dirty cards in the mod
1410 // union table and the card table proper. It's invoked via
1411 // MarkFromDirtyCardsClosure below. It uses either
1412 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1413 // declared in genOopClosures.hpp to accomplish some of its work.
1414 // In the parallel case the bitMap is shared, so access to
1415 // it needs to be suitably synchronized for updates by embedded
1416 // closures that update it; however, this closure itself only
1417 // reads the bit_map and because it is idempotent, is immune to
1418 // reading stale values.
1419 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1420 #ifdef ASSERT
1421 CMSCollector* _collector;
1422 MemRegion _span;
1423 union {
1424 CMSMarkStack* _mark_stack;
1425 OopTaskQueue* _work_queue;
1426 };
1427 #endif // ASSERT
1428 bool _parallel;
1429 CMSBitMap* _bit_map;
1430 union {
1431 MarkRefsIntoAndScanClosure* _scan_closure;
1432 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1433 };
1434
1435 public:
1436 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1437 MemRegion span,
1438 ReferenceProcessor* rp,
1439 CMSBitMap* bit_map,
1440 CMSMarkStack* mark_stack,
1441 MarkRefsIntoAndScanClosure* cl):
1442 #ifdef ASSERT
1443 _collector(collector),
1444 _span(span),
1445 _mark_stack(mark_stack),
1446 #endif // ASSERT
1447 _parallel(false),
1448 _bit_map(bit_map),
1449 _scan_closure(cl) { }
1450
1451 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1452 MemRegion span,
1453 ReferenceProcessor* rp,
1454 CMSBitMap* bit_map,
1455 OopTaskQueue* work_queue,
1456 Par_MarkRefsIntoAndScanClosure* cl):
1457 #ifdef ASSERT
1458 _collector(collector),
1459 _span(span),
1460 _work_queue(work_queue),
1461 #endif // ASSERT
1462 _parallel(true),
1463 _bit_map(bit_map),
1464 _par_scan_closure(cl) { }
1465
1466 bool do_object_b(oop obj) {
1467 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1468 return false;
1469 }
1470 bool do_object_bm(oop p, MemRegion mr);
1471 };
1472
1473 // This closure is used during the second checkpointing phase
1474 // to rescan the marked objects on the dirty cards in the mod
1475 // union table and the card table proper. It invokes
1476 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1477 // In the parallel case, the bit map is shared and requires
1478 // synchronized access.
1479 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1480 CompactibleFreeListSpace* _space;
1481 ScanMarkedObjectsAgainClosure _scan_cl;
1482 size_t _num_dirty_cards;
1483
1484 public:
1485 MarkFromDirtyCardsClosure(CMSCollector* collector,
1486 MemRegion span,
1487 CompactibleFreeListSpace* space,
1488 CMSBitMap* bit_map,
1489 CMSMarkStack* mark_stack,
1490 MarkRefsIntoAndScanClosure* cl):
1491 _space(space),
1492 _num_dirty_cards(0),
1493 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1494 mark_stack, cl) { }
1495
1496 MarkFromDirtyCardsClosure(CMSCollector* collector,
1497 MemRegion span,
1498 CompactibleFreeListSpace* space,
1499 CMSBitMap* bit_map,
1500 OopTaskQueue* work_queue,
1501 Par_MarkRefsIntoAndScanClosure* cl):
1502 _space(space),
1503 _num_dirty_cards(0),
1504 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1505 work_queue, cl) { }
1506
1507 void do_MemRegion(MemRegion mr);
1508 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1509 size_t num_dirty_cards() { return _num_dirty_cards; }
1510 };
1511
1512 // This closure is used in the non-product build to check
1513 // that there are no MemRegions with a certain property.
1514 class FalseMemRegionClosure: public MemRegionClosure {
1515 void do_MemRegion(MemRegion mr) {
1516 guarantee(!mr.is_empty(), "Shouldn't be empty");
1517 guarantee(false, "Should never be here");
1518 }
1519 };
1520
1521 // This closure is used during the precleaning phase
1522 // to "carefully" rescan marked objects on dirty cards.
1523 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1524 // to accomplish some of its work.
1525 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1526 CMSCollector* _collector;
1527 MemRegion _span;
1528 bool _yield;
1529 Mutex* _freelistLock;
1530 CMSBitMap* _bitMap;
1531 CMSMarkStack* _markStack;
1532 MarkRefsIntoAndScanClosure* _scanningClosure;
1533
1534 public:
1535 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1536 MemRegion span,
1537 CMSBitMap* bitMap,
1538 CMSMarkStack* markStack,
1539 MarkRefsIntoAndScanClosure* cl,
1540 bool should_yield):
1541 _collector(collector),
1542 _span(span),
1543 _yield(should_yield),
1544 _bitMap(bitMap),
1545 _markStack(markStack),
1546 _scanningClosure(cl) {
1547 }
1548
1549 void do_object(oop p) {
1550 guarantee(false, "call do_object_careful instead");
1551 }
1552
1553 size_t do_object_careful(oop p) {
1554 guarantee(false, "Unexpected caller");
1555 return 0;
1556 }
1557
1558 size_t do_object_careful_m(oop p, MemRegion mr);
1559
1560 void setFreelistLock(Mutex* m) {
1561 _freelistLock = m;
1562 _scanningClosure->set_freelistLock(m);
1563 }
1564
1565 private:
1566 inline bool do_yield_check();
1567
1568 void do_yield_work();
1569 };
1570
1571 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1572 CMSCollector* _collector;
1573 MemRegion _span;
1574 bool _yield;
1575 CMSBitMap* _bit_map;
1576 CMSMarkStack* _mark_stack;
1577 PushAndMarkClosure* _scanning_closure;
1578 unsigned int _before_count;
1579
1580 public:
1581 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1582 MemRegion span,
1583 CMSBitMap* bit_map,
1584 CMSMarkStack* mark_stack,
1585 PushAndMarkClosure* cl,
1586 unsigned int before_count,
1587 bool should_yield):
1588 _collector(collector),
1589 _span(span),
1590 _yield(should_yield),
1591 _bit_map(bit_map),
1592 _mark_stack(mark_stack),
1593 _scanning_closure(cl),
1594 _before_count(before_count)
1595 { }
1596
1597 void do_object(oop p) {
1598 guarantee(false, "call do_object_careful instead");
1599 }
1600
1601 size_t do_object_careful(oop p);
1602
1603 size_t do_object_careful_m(oop p, MemRegion mr) {
1604 guarantee(false, "Unexpected caller");
1605 return 0;
1606 }
1607
1608 private:
1609 inline void do_yield_check();
1610 void do_yield_work();
1611 };
1612
1613 // This closure is used to accomplish the sweeping work
1614 // after the second checkpoint but before the concurrent reset
1615 // phase.
1616 //
1617 // Terminology
1618 // left hand chunk (LHC) - block of one or more chunks currently being
1619 // coalesced. The LHC is available for coalescing with a new chunk.
1620 // right hand chunk (RHC) - block that is currently being swept that is
1621 // free or garbage that can be coalesced with the LHC.
1622 // _inFreeRange is true if there is currently a LHC
1623 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1624 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1625 // _freeFinger is the address of the current LHC
1626 class SweepClosure: public BlkClosureCareful {
1627 CMSCollector* _collector; // collector doing the work
1628 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1629 CompactibleFreeListSpace* _sp; // Space being swept
1630 HeapWord* _limit;// the address at or above which the sweep should stop
1631 // because we do not expect newly garbage blocks
1632 // eligible for sweeping past that address.
1633 Mutex* _freelistLock; // Free list lock (in space)
1634 CMSBitMap* _bitMap; // Marking bit map (in
1635 // generation)
1636 bool _inFreeRange; // Indicates if we are in the
1637 // midst of a free run
1638 bool _freeRangeInFreeLists;
1639 // Often, we have just found
1640 // a free chunk and started
1641 // a new free range; we do not
1642 // eagerly remove this chunk from
1643 // the free lists unless there is
1644 // a possibility of coalescing.
1645 // When true, this flag indicates
1646 // that the _freeFinger below
1647 // points to a potentially free chunk
1648 // that may still be in the free lists
1649 bool _lastFreeRangeCoalesced;
1650 // free range contains chunks
1651 // coalesced
1652 bool _yield;
1653 // Whether sweeping should be
1654 // done with yields. For instance
1655 // when done by the foreground
1656 // collector we shouldn't yield.
1657 HeapWord* _freeFinger; // When _inFreeRange is set, the
1658 // pointer to the "left hand
1659 // chunk"
1660 size_t _freeRangeSize;
1661 // When _inFreeRange is set, this
1662 // indicates the accumulated size
1663 // of the "left hand chunk"
1664 NOT_PRODUCT(
1665 size_t _numObjectsFreed;
1666 size_t _numWordsFreed;
1667 size_t _numObjectsLive;
1668 size_t _numWordsLive;
1669 size_t _numObjectsAlreadyFree;
1670 size_t _numWordsAlreadyFree;
1671 FreeChunk* _last_fc;
1672 )
1673 private:
1674 // Code that is common to a free chunk or garbage when
1675 // encountered during sweeping.
1676 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1677 // Process a free chunk during sweeping.
1678 void do_already_free_chunk(FreeChunk *fc);
1679 // Work method called when processing an already free or a
1680 // freshly garbage chunk to do a lookahead and possibly a
1681 // preemptive flush if crossing over _limit.
1682 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1683 // Process a garbage chunk during sweeping.
1684 size_t do_garbage_chunk(FreeChunk *fc);
1685 // Process a live chunk during sweeping.
1686 size_t do_live_chunk(FreeChunk* fc);
1687
1688 // Accessors.
1689 HeapWord* freeFinger() const { return _freeFinger; }
1690 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1691 bool inFreeRange() const { return _inFreeRange; }
1692 void set_inFreeRange(bool v) { _inFreeRange = v; }
1693 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1694 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1695 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1696 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1697
1698 // Initialize a free range.
1699 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1700 // Return this chunk to the free lists.
1701 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1702
1703 // Check if we should yield and do so when necessary.
1704 inline void do_yield_check(HeapWord* addr);
1705
1706 // Yield
1707 void do_yield_work(HeapWord* addr);
1708
1709 // Debugging/Printing
1710 void print_free_block_coalesced(FreeChunk* fc) const;
1711
1712 public:
1713 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1714 CMSBitMap* bitMap, bool should_yield);
1715 ~SweepClosure() PRODUCT_RETURN;
1716
1717 size_t do_blk_careful(HeapWord* addr);
1718 void print() const { print_on(tty); }
1719 void print_on(outputStream *st) const;
1720 };
1721
1722 // Closures related to weak references processing
1723
1724 // During CMS' weak reference processing, this is a
1725 // work-routine/closure used to complete transitive
1726 // marking of objects as live after a certain point
1727 // in which an initial set has been completely accumulated.
1728 // This closure is currently used both during the final
1729 // remark stop-world phase, as well as during the concurrent
1730 // precleaning of the discovered reference lists.
1731 class CMSDrainMarkingStackClosure: public VoidClosure {
1732 CMSCollector* _collector;
1733 MemRegion _span;
1734 CMSMarkStack* _mark_stack;
1735 CMSBitMap* _bit_map;
1736 CMSKeepAliveClosure* _keep_alive;
1737 bool _concurrent_precleaning;
1738 public:
1739 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1740 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1741 CMSKeepAliveClosure* keep_alive,
1742 bool cpc):
1743 _collector(collector),
1744 _span(span),
1745 _bit_map(bit_map),
1746 _mark_stack(mark_stack),
1747 _keep_alive(keep_alive),
1748 _concurrent_precleaning(cpc) {
1749 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1750 "Mismatch");
1751 }
1752
1753 void do_void();
1754 };
1755
1756 // A parallel version of CMSDrainMarkingStackClosure above.
1757 class CMSParDrainMarkingStackClosure: public VoidClosure {
1758 CMSCollector* _collector;
1759 MemRegion _span;
1760 OopTaskQueue* _work_queue;
1761 CMSBitMap* _bit_map;
1762 CMSInnerParMarkAndPushClosure _mark_and_push;
1763
1764 public:
1765 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1766 MemRegion span, CMSBitMap* bit_map,
1767 OopTaskQueue* work_queue):
1768 _collector(collector),
1769 _span(span),
1770 _bit_map(bit_map),
1771 _work_queue(work_queue),
1772 _mark_and_push(collector, span, bit_map, work_queue) { }
1773
1774 public:
1775 void trim_queue(uint max);
1776 void do_void();
1777 };
1778
1779 // Allow yielding or short-circuiting of reference list
1780 // precleaning work.
1781 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1782 CMSCollector* _collector;
1783 void do_yield_work();
1784 public:
1785 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1786 _collector(collector) {}
1787 virtual bool should_return();
1788 };
1789
1790
1791 // Convenience class that locks free list locks for given CMS collector
1792 class FreelistLocker: public StackObj {
1793 private:
1794 CMSCollector* _collector;
1795 public:
1796 FreelistLocker(CMSCollector* collector):
1797 _collector(collector) {
1798 _collector->getFreelistLocks();
1799 }
1800
1801 ~FreelistLocker() {
1802 _collector->releaseFreelistLocks();
1803 }
1804 };
1805
1806 // Mark all dead objects in a given space.
1807 class MarkDeadObjectsClosure: public BlkClosure {
1808 const CMSCollector* _collector;
1809 const CompactibleFreeListSpace* _sp;
1810 CMSBitMap* _live_bit_map;
1811 CMSBitMap* _dead_bit_map;
1812 public:
1813 MarkDeadObjectsClosure(const CMSCollector* collector,
1814 const CompactibleFreeListSpace* sp,
1815 CMSBitMap *live_bit_map,
1816 CMSBitMap *dead_bit_map) :
1817 _collector(collector),
1818 _sp(sp),
1819 _live_bit_map(live_bit_map),
1820 _dead_bit_map(dead_bit_map) {}
1821 size_t do_blk(HeapWord* addr);
1822 };
1823
1824 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1825
1826 public:
1827 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1828 };
1829
1830
1831 #endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP