1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
27
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gSpaceCounters.hpp"
30 #include "gc_implementation/shared/gcStats.hpp"
31 #include "gc_implementation/shared/gcWhen.hpp"
32 #include "gc_implementation/shared/generationCounters.hpp"
33 #include "memory/freeBlockDictionary.hpp"
34 #include "memory/generation.hpp"
35 #include "memory/iterator.hpp"
36 #include "runtime/mutexLocker.hpp"
37 #include "runtime/virtualspace.hpp"
38 #include "services/memoryService.hpp"
39 #include "utilities/bitMap.inline.hpp"
40 #include "utilities/stack.inline.hpp"
41 #include "utilities/taskqueue.hpp"
42 #include "utilities/yieldingWorkgroup.hpp"
43
44 // ConcurrentMarkSweepGeneration is in support of a concurrent
45 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
46 // style. We assume, for now, that this generation is always the
47 // seniormost generation and for simplicity
48 // in the first implementation, that this generation is a single compactible
49 // space. Neither of these restrictions appears essential, and will be
50 // relaxed in the future when more time is available to implement the
51 // greater generality (and there's a need for it).
52 //
53 // Concurrent mode failures are currently handled by
54 // means of a sliding mark-compact.
55
56 class AdaptiveSizePolicy;
57 class CMSConcMarkingTask;
58 class CMSGCAdaptivePolicyCounters;
59 class CMSTracer;
60 class ConcurrentGCTimer;
61 class ConcurrentMarkSweepGeneration;
62 class ConcurrentMarkSweepPolicy;
63 class ConcurrentMarkSweepThread;
64 class CompactibleFreeListSpace;
65 class FreeChunk;
66 class PromotionInfo;
67 class ScanMarkedObjectsAgainCarefullyClosure;
68 class TenuredGeneration;
69 class SerialOldTracer;
70
71 // A generic CMS bit map. It's the basis for both the CMS marking bit map
72 // as well as for the mod union table (in each case only a subset of the
73 // methods are used). This is essentially a wrapper around the BitMap class,
74 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
75 // we have _shifter == 0. and for the mod union table we have
76 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
77 // XXX 64-bit issues in BitMap?
78 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
79 friend class VMStructs;
80
81 HeapWord* _bmStartWord; // base address of range covered by map
82 size_t _bmWordSize; // map size (in #HeapWords covered)
83 const int _shifter; // shifts to convert HeapWord to bit position
84 VirtualSpace _virtual_space; // underlying the bit map
85 BitMap _bm; // the bit map itself
86 public:
87 Mutex* const _lock; // mutex protecting _bm;
88
89 public:
90 // constructor
91 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
92
93 // allocates the actual storage for the map
94 bool allocate(MemRegion mr);
95 // field getter
96 Mutex* lock() const { return _lock; }
97 // locking verifier convenience function
98 void assert_locked() const PRODUCT_RETURN;
99
100 // inquiries
101 HeapWord* startWord() const { return _bmStartWord; }
102 size_t sizeInWords() const { return _bmWordSize; }
103 size_t sizeInBits() const { return _bm.size(); }
104 // the following is one past the last word in space
105 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
106
107 // reading marks
108 bool isMarked(HeapWord* addr) const;
109 bool par_isMarked(HeapWord* addr) const; // do not lock checks
110 bool isUnmarked(HeapWord* addr) const;
111 bool isAllClear() const;
112
113 // writing marks
114 void mark(HeapWord* addr);
115 // For marking by parallel GC threads;
116 // returns true if we did, false if another thread did
117 bool par_mark(HeapWord* addr);
118
119 void mark_range(MemRegion mr);
120 void par_mark_range(MemRegion mr);
121 void mark_large_range(MemRegion mr);
122 void par_mark_large_range(MemRegion mr);
123 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
124 void clear_range(MemRegion mr);
125 void par_clear_range(MemRegion mr);
126 void clear_large_range(MemRegion mr);
127 void par_clear_large_range(MemRegion mr);
128 void clear_all();
129 void clear_all_incrementally(); // Not yet implemented!!
130
131 NOT_PRODUCT(
132 // checks the memory region for validity
133 void region_invariant(MemRegion mr);
134 )
135
136 // iteration
137 void iterate(BitMapClosure* cl) {
138 _bm.iterate(cl);
139 }
140 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
141 void dirty_range_iterate_clear(MemRegionClosure* cl);
142 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
143
144 // auxiliary support for iteration
145 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
146 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
147 HeapWord* end_addr) const;
148 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
149 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
150 HeapWord* end_addr) const;
151 MemRegion getAndClearMarkedRegion(HeapWord* addr);
152 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
153 HeapWord* end_addr);
154
155 // conversion utilities
156 HeapWord* offsetToHeapWord(size_t offset) const;
157 size_t heapWordToOffset(HeapWord* addr) const;
158 size_t heapWordDiffToOffsetDiff(size_t diff) const;
159
160 void print_on_error(outputStream* st, const char* prefix) const;
161
162 // debugging
163 // is this address range covered by the bit-map?
164 NOT_PRODUCT(
165 bool covers(MemRegion mr) const;
166 bool covers(HeapWord* start, size_t size = 0) const;
167 )
168 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
169 };
170
171 // Represents a marking stack used by the CMS collector.
172 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
173 class CMSMarkStack: public CHeapObj<mtGC> {
174 //
175 friend class CMSCollector; // To get at expansion stats further below.
176 //
177
178 VirtualSpace _virtual_space; // Space for the stack
179 oop* _base; // Bottom of stack
180 size_t _index; // One more than last occupied index
181 size_t _capacity; // Max #elements
182 Mutex _par_lock; // An advisory lock used in case of parallel access
183 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run
184
185 protected:
186 size_t _hit_limit; // We hit max stack size limit
187 size_t _failed_double; // We failed expansion before hitting limit
188
189 public:
190 CMSMarkStack():
191 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
192 _hit_limit(0),
193 _failed_double(0) {}
194
195 bool allocate(size_t size);
196
197 size_t capacity() const { return _capacity; }
198
199 oop pop() {
200 if (!isEmpty()) {
201 return _base[--_index] ;
202 }
203 return NULL;
204 }
205
206 bool push(oop ptr) {
207 if (isFull()) {
208 return false;
209 } else {
210 _base[_index++] = ptr;
211 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
212 return true;
213 }
214 }
215
216 bool isEmpty() const { return _index == 0; }
217 bool isFull() const {
218 assert(_index <= _capacity, "buffer overflow");
219 return _index == _capacity;
220 }
221
222 size_t length() { return _index; }
223
224 // "Parallel versions" of some of the above
225 oop par_pop() {
226 // lock and pop
227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
228 return pop();
229 }
230
231 bool par_push(oop ptr) {
232 // lock and push
233 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
234 return push(ptr);
235 }
236
237 // Forcibly reset the stack, losing all of its contents.
238 void reset() {
239 _index = 0;
240 }
241
242 // Expand the stack, typically in response to an overflow condition.
243 void expand();
244
245 // Compute the least valued stack element.
246 oop least_value(HeapWord* low) {
247 oop least = (oop)low;
248 for (size_t i = 0; i < _index; i++) {
249 least = MIN2(least, _base[i]);
250 }
251 return least;
252 }
253
254 // Exposed here to allow stack expansion in || case.
255 Mutex* par_lock() { return &_par_lock; }
256 };
257
258 class CardTableRS;
259 class CMSParGCThreadState;
260
261 class ModUnionClosure: public MemRegionClosure {
262 protected:
263 CMSBitMap* _t;
264 public:
265 ModUnionClosure(CMSBitMap* t): _t(t) { }
266 void do_MemRegion(MemRegion mr);
267 };
268
269 class ModUnionClosurePar: public ModUnionClosure {
270 public:
271 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
272 void do_MemRegion(MemRegion mr);
273 };
274
275 // Survivor Chunk Array in support of parallelization of
276 // Survivor Space rescan.
277 class ChunkArray: public CHeapObj<mtGC> {
278 size_t _index;
279 size_t _capacity;
280 size_t _overflows;
281 HeapWord** _array; // storage for array
282
283 public:
284 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
285 ChunkArray(HeapWord** a, size_t c):
286 _index(0), _capacity(c), _overflows(0), _array(a) {}
287
288 HeapWord** array() { return _array; }
289 void set_array(HeapWord** a) { _array = a; }
290
291 size_t capacity() { return _capacity; }
292 void set_capacity(size_t c) { _capacity = c; }
293
294 size_t end() {
295 assert(_index <= capacity(),
296 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
297 _index, _capacity));
298 return _index;
299 } // exclusive
300
301 HeapWord* nth(size_t n) {
302 assert(n < end(), "Out of bounds access");
303 return _array[n];
304 }
305
306 void reset() {
307 _index = 0;
308 if (_overflows > 0 && PrintCMSStatistics > 1) {
309 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
310 _capacity, _overflows);
311 }
312 _overflows = 0;
313 }
314
315 void record_sample(HeapWord* p, size_t sz) {
316 // For now we do not do anything with the size
317 if (_index < _capacity) {
318 _array[_index++] = p;
319 } else {
320 ++_overflows;
321 assert(_index == _capacity,
322 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
323 "): out of bounds at overflow#" SIZE_FORMAT,
324 _index, _capacity, _overflows));
325 }
326 }
327 };
328
329 //
330 // Timing, allocation and promotion statistics for gc scheduling and incremental
331 // mode pacing. Most statistics are exponential averages.
332 //
333 class CMSStats VALUE_OBJ_CLASS_SPEC {
334 private:
335 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
336
337 // The following are exponential averages with factor alpha:
338 // avg = (100 - alpha) * avg + alpha * cur_sample
339 //
340 // The durations measure: end_time[n] - start_time[n]
341 // The periods measure: start_time[n] - start_time[n-1]
342 //
343 // The cms period and duration include only concurrent collections; time spent
344 // in foreground cms collections due to System.gc() or because of a failure to
345 // keep up are not included.
346 //
347 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
348 // real value, but is used only after the first period. A value of 100 is
349 // used for the first sample so it gets the entire weight.
350 unsigned int _saved_alpha; // 0-100
351 unsigned int _gc0_alpha;
352 unsigned int _cms_alpha;
353
354 double _gc0_duration;
355 double _gc0_period;
356 size_t _gc0_promoted; // bytes promoted per gc0
357 double _cms_duration;
358 double _cms_duration_pre_sweep; // time from initiation to start of sweep
359 double _cms_period;
360 size_t _cms_allocated; // bytes of direct allocation per gc0 period
361
362 // Timers.
363 elapsedTimer _cms_timer;
364 TimeStamp _gc0_begin_time;
365 TimeStamp _cms_begin_time;
366 TimeStamp _cms_end_time;
367
368 // Snapshots of the amount used in the CMS generation.
369 size_t _cms_used_at_gc0_begin;
370 size_t _cms_used_at_gc0_end;
371 size_t _cms_used_at_cms_begin;
372
373 // Used to prevent the duty cycle from being reduced in the middle of a cms
374 // cycle.
375 bool _allow_duty_cycle_reduction;
376
377 enum {
378 _GC0_VALID = 0x1,
379 _CMS_VALID = 0x2,
380 _ALL_VALID = _GC0_VALID | _CMS_VALID
381 };
382
383 unsigned int _valid_bits;
384
385 protected:
386 // In support of adjusting of cms trigger ratios based on history
387 // of concurrent mode failure.
388 double cms_free_adjustment_factor(size_t free) const;
389 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
390
391 public:
392 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
393 unsigned int alpha = CMSExpAvgFactor);
394
395 // Whether or not the statistics contain valid data; higher level statistics
396 // cannot be called until this returns true (they require at least one young
397 // gen and one cms cycle to have completed).
398 bool valid() const;
399
400 // Record statistics.
401 void record_gc0_begin();
402 void record_gc0_end(size_t cms_gen_bytes_used);
403 void record_cms_begin();
404 void record_cms_end();
405
406 // Allow management of the cms timer, which must be stopped/started around
407 // yield points.
408 elapsedTimer& cms_timer() { return _cms_timer; }
409 void start_cms_timer() { _cms_timer.start(); }
410 void stop_cms_timer() { _cms_timer.stop(); }
411
412 // Basic statistics; units are seconds or bytes.
413 double gc0_period() const { return _gc0_period; }
414 double gc0_duration() const { return _gc0_duration; }
415 size_t gc0_promoted() const { return _gc0_promoted; }
416 double cms_period() const { return _cms_period; }
417 double cms_duration() const { return _cms_duration; }
418 size_t cms_allocated() const { return _cms_allocated; }
419
420 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
421
422 // Seconds since the last background cms cycle began or ended.
423 double cms_time_since_begin() const;
424 double cms_time_since_end() const;
425
426 // Higher level statistics--caller must check that valid() returns true before
427 // calling.
428
429 // Returns bytes promoted per second of wall clock time.
430 double promotion_rate() const;
431
432 // Returns bytes directly allocated per second of wall clock time.
433 double cms_allocation_rate() const;
434
435 // Rate at which space in the cms generation is being consumed (sum of the
436 // above two).
437 double cms_consumption_rate() const;
438
439 // Returns an estimate of the number of seconds until the cms generation will
440 // fill up, assuming no collection work is done.
441 double time_until_cms_gen_full() const;
442
443 // Returns an estimate of the number of seconds remaining until
444 // the cms generation collection should start.
445 double time_until_cms_start() const;
446
447 // End of higher level statistics.
448
449 // Debugging.
450 void print_on(outputStream* st) const PRODUCT_RETURN;
451 void print() const { print_on(gclog_or_tty); }
452 };
453
454 // A closure related to weak references processing which
455 // we embed in the CMSCollector, since we need to pass
456 // it to the reference processor for secondary filtering
457 // of references based on reachability of referent;
458 // see role of _is_alive_non_header closure in the
459 // ReferenceProcessor class.
460 // For objects in the CMS generation, this closure checks
461 // if the object is "live" (reachable). Used in weak
462 // reference processing.
463 class CMSIsAliveClosure: public BoolObjectClosure {
464 const MemRegion _span;
465 const CMSBitMap* _bit_map;
466
467 friend class CMSCollector;
468 public:
469 CMSIsAliveClosure(MemRegion span,
470 CMSBitMap* bit_map):
471 _span(span),
472 _bit_map(bit_map) {
473 assert(!span.is_empty(), "Empty span could spell trouble");
474 }
475
476 bool do_object_b(oop obj);
477 };
478
479
480 // Implements AbstractRefProcTaskExecutor for CMS.
481 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
482 public:
483
484 CMSRefProcTaskExecutor(CMSCollector& collector)
485 : _collector(collector)
486 { }
487
488 // Executes a task using worker threads.
489 virtual void execute(ProcessTask& task);
490 virtual void execute(EnqueueTask& task);
491 private:
492 CMSCollector& _collector;
493 };
494
495
496 class CMSCollector: public CHeapObj<mtGC> {
497 friend class VMStructs;
498 friend class ConcurrentMarkSweepThread;
499 friend class ConcurrentMarkSweepGeneration;
500 friend class CompactibleFreeListSpace;
501 friend class CMSParMarkTask;
502 friend class CMSParInitialMarkTask;
503 friend class CMSParRemarkTask;
504 friend class CMSConcMarkingTask;
505 friend class CMSRefProcTaskProxy;
506 friend class CMSRefProcTaskExecutor;
507 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
508 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
509 friend class PushOrMarkClosure; // to access _restart_addr
510 friend class Par_PushOrMarkClosure; // to access _restart_addr
511 friend class MarkFromRootsClosure; // -- ditto --
512 // ... and for clearing cards
513 friend class Par_MarkFromRootsClosure; // to access _restart_addr
514 // ... and for clearing cards
515 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
516 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
517 friend class PushAndMarkVerifyClosure; // -- ditto --
518 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
519 friend class PushAndMarkClosure; // -- ditto --
520 friend class Par_PushAndMarkClosure; // -- ditto --
521 friend class CMSKeepAliveClosure; // -- ditto --
522 friend class CMSDrainMarkingStackClosure; // -- ditto --
523 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
524 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
525 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
526 friend class VM_CMS_Operation;
527 friend class VM_CMS_Initial_Mark;
528 friend class VM_CMS_Final_Remark;
529 friend class TraceCMSMemoryManagerStats;
530
531 private:
532 jlong _time_of_last_gc;
533 void update_time_of_last_gc(jlong now) {
534 _time_of_last_gc = now;
535 }
536
537 OopTaskQueueSet* _task_queues;
538
539 // Overflow list of grey objects, threaded through mark-word
540 // Manipulated with CAS in the parallel/multi-threaded case.
541 oop _overflow_list;
542 // The following array-pair keeps track of mark words
543 // displaced for accommodating overflow list above.
544 // This code will likely be revisited under RFE#4922830.
545 Stack<oop, mtGC> _preserved_oop_stack;
546 Stack<markOop, mtGC> _preserved_mark_stack;
547
548 int* _hash_seed;
549
550 // In support of multi-threaded concurrent phases
551 YieldingFlexibleWorkGang* _conc_workers;
552
553 // Performance Counters
554 CollectorCounters* _gc_counters;
555
556 // Initialization Errors
557 bool _completed_initialization;
558
559 // In support of ExplicitGCInvokesConcurrent
560 static bool _full_gc_requested;
561 static GCCause::Cause _full_gc_cause;
562 unsigned int _collection_count_start;
563
564 // Should we unload classes this concurrent cycle?
565 bool _should_unload_classes;
566 unsigned int _concurrent_cycles_since_last_unload;
567 unsigned int concurrent_cycles_since_last_unload() const {
568 return _concurrent_cycles_since_last_unload;
569 }
570 // Did we (allow) unload classes in the previous concurrent cycle?
571 bool unloaded_classes_last_cycle() const {
572 return concurrent_cycles_since_last_unload() == 0;
573 }
574 // Root scanning options for perm gen
575 int _roots_scanning_options;
576 int roots_scanning_options() const { return _roots_scanning_options; }
577 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
578 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
579
580 // Verification support
581 CMSBitMap _verification_mark_bm;
582 void verify_after_remark_work_1();
583 void verify_after_remark_work_2();
584
585 // True if any verification flag is on.
586 bool _verifying;
587 bool verifying() const { return _verifying; }
588 void set_verifying(bool v) { _verifying = v; }
589
590 // Collector policy
591 ConcurrentMarkSweepPolicy* _collector_policy;
592 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
593
594 void set_did_compact(bool v);
595
596 // XXX Move these to CMSStats ??? FIX ME !!!
597 elapsedTimer _inter_sweep_timer; // Time between sweeps
598 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
599 // Padded decaying average estimates of the above
600 AdaptivePaddedAverage _inter_sweep_estimate;
601 AdaptivePaddedAverage _intra_sweep_estimate;
602
603 CMSTracer* _gc_tracer_cm;
604 ConcurrentGCTimer* _gc_timer_cm;
605
606 bool _cms_start_registered;
607
608 GCHeapSummary _last_heap_summary;
609 MetaspaceSummary _last_metaspace_summary;
610
611 void register_gc_start(GCCause::Cause cause);
612 void register_gc_end();
613 void save_heap_summary();
614 void report_heap_summary(GCWhen::Type when);
615
616 protected:
617 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
618 MemRegion _span; // Span covering above two
619 CardTableRS* _ct; // Card table
620
621 // CMS marking support structures
622 CMSBitMap _markBitMap;
623 CMSBitMap _modUnionTable;
624 CMSMarkStack _markStack;
625
626 HeapWord* _restart_addr; // In support of marking stack overflow
627 void lower_restart_addr(HeapWord* low);
628
629 // Counters in support of marking stack / work queue overflow handling:
630 // a non-zero value indicates certain types of overflow events during
631 // the current CMS cycle and could lead to stack resizing efforts at
632 // an opportune future time.
633 size_t _ser_pmc_preclean_ovflw;
634 size_t _ser_pmc_remark_ovflw;
635 size_t _par_pmc_remark_ovflw;
636 size_t _ser_kac_preclean_ovflw;
637 size_t _ser_kac_ovflw;
638 size_t _par_kac_ovflw;
639 NOT_PRODUCT(ssize_t _num_par_pushes;)
640
641 // ("Weak") Reference processing support.
642 ReferenceProcessor* _ref_processor;
643 CMSIsAliveClosure _is_alive_closure;
644 // Keep this textually after _markBitMap and _span; c'tor dependency.
645
646 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
647 ModUnionClosure _modUnionClosure;
648 ModUnionClosurePar _modUnionClosurePar;
649
650 // CMS abstract state machine
651 // initial_state: Idling
652 // next_state(Idling) = {Marking}
653 // next_state(Marking) = {Precleaning, Sweeping}
654 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
655 // next_state(AbortablePreclean) = {FinalMarking}
656 // next_state(FinalMarking) = {Sweeping}
657 // next_state(Sweeping) = {Resizing}
658 // next_state(Resizing) = {Resetting}
659 // next_state(Resetting) = {Idling}
660 // The numeric values below are chosen so that:
661 // . _collectorState <= Idling == post-sweep && pre-mark
662 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
663 // precleaning || abortablePrecleanb
664 public:
665 enum CollectorState {
666 Resizing = 0,
667 Resetting = 1,
668 Idling = 2,
669 InitialMarking = 3,
670 Marking = 4,
671 Precleaning = 5,
672 AbortablePreclean = 6,
673 FinalMarking = 7,
674 Sweeping = 8
675 };
676 protected:
677 static CollectorState _collectorState;
678
679 // State related to prologue/epilogue invocation for my generations
680 bool _between_prologue_and_epilogue;
681
682 // Signaling/State related to coordination between fore- and background GC
683 // Note: When the baton has been passed from background GC to foreground GC,
684 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
685 static bool _foregroundGCIsActive; // true iff foreground collector is active or
686 // wants to go active
687 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
688 // yet passed the baton to the foreground GC
689
690 // Support for CMSScheduleRemark (abortable preclean)
691 bool _abort_preclean;
692 bool _start_sampling;
693
694 int _numYields;
695 size_t _numDirtyCards;
696 size_t _sweep_count;
697
698 // Occupancy used for bootstrapping stats
699 double _bootstrap_occupancy;
700
701 // Timer
702 elapsedTimer _timer;
703
704 // Timing, allocation and promotion statistics, used for scheduling.
705 CMSStats _stats;
706
707 enum CMS_op_type {
708 CMS_op_checkpointRootsInitial,
709 CMS_op_checkpointRootsFinal
710 };
711
712 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
713 bool stop_world_and_do(CMS_op_type op);
714
715 OopTaskQueueSet* task_queues() { return _task_queues; }
716 int* hash_seed(int i) { return &_hash_seed[i]; }
717 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
718
719 // Support for parallelizing Eden rescan in CMS remark phase
720 void sample_eden(); // ... sample Eden space top
721
722 private:
723 // Support for parallelizing young gen rescan in CMS remark phase
724 Generation* _young_gen; // the younger gen
725 HeapWord** _top_addr; // ... Top of Eden
726 HeapWord** _end_addr; // ... End of Eden
727 Mutex* _eden_chunk_lock;
728 HeapWord** _eden_chunk_array; // ... Eden partitioning array
729 size_t _eden_chunk_index; // ... top (exclusive) of array
730 size_t _eden_chunk_capacity; // ... max entries in array
731
732 // Support for parallelizing survivor space rescan
733 HeapWord** _survivor_chunk_array;
734 size_t _survivor_chunk_index;
735 size_t _survivor_chunk_capacity;
736 size_t* _cursor;
737 ChunkArray* _survivor_plab_array;
738
739 // Support for marking stack overflow handling
740 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
741 bool par_take_from_overflow_list(size_t num,
742 OopTaskQueue* to_work_q,
743 int no_of_gc_threads);
744 void push_on_overflow_list(oop p);
745 void par_push_on_overflow_list(oop p);
746 // The following is, obviously, not, in general, "MT-stable"
747 bool overflow_list_is_empty() const;
748
749 void preserve_mark_if_necessary(oop p);
750 void par_preserve_mark_if_necessary(oop p);
751 void preserve_mark_work(oop p, markOop m);
752 void restore_preserved_marks_if_any();
753 NOT_PRODUCT(bool no_preserved_marks() const;)
754 // In support of testing overflow code
755 NOT_PRODUCT(int _overflow_counter;)
756 NOT_PRODUCT(bool simulate_overflow();) // Sequential
757 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
758
759 // CMS work methods
760 void checkpointRootsInitialWork(); // Initial checkpoint work
761
762 // A return value of false indicates failure due to stack overflow
763 bool markFromRootsWork(); // Concurrent marking work
764
765 public: // FIX ME!!! only for testing
766 bool do_marking_st(); // Single-threaded marking
767 bool do_marking_mt(); // Multi-threaded marking
768
769 private:
770
771 // Concurrent precleaning work
772 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
773 ScanMarkedObjectsAgainCarefullyClosure* cl);
774 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
775 ScanMarkedObjectsAgainCarefullyClosure* cl);
776 // Does precleaning work, returning a quantity indicative of
777 // the amount of "useful work" done.
778 size_t preclean_work(bool clean_refs, bool clean_survivors);
779 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
780 void abortable_preclean(); // Preclean while looking for possible abort
781 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
782 // Helper function for above; merge-sorts the per-thread plab samples
783 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
784 // Resets (i.e. clears) the per-thread plab sample vectors
785 void reset_survivor_plab_arrays();
786
787 // Final (second) checkpoint work
788 void checkpointRootsFinalWork();
789 // Work routine for parallel version of remark
790 void do_remark_parallel();
791 // Work routine for non-parallel version of remark
792 void do_remark_non_parallel();
793 // Reference processing work routine (during second checkpoint)
794 void refProcessingWork();
795
796 // Concurrent sweeping work
797 void sweepWork(ConcurrentMarkSweepGeneration* gen);
798
799 // (Concurrent) resetting of support data structures
800 void reset(bool concurrent);
801
802 // Clear _expansion_cause fields of constituent generations
803 void clear_expansion_cause();
804
805 // An auxiliary method used to record the ends of
806 // used regions of each generation to limit the extent of sweep
807 void save_sweep_limits();
808
809 // A work method used by the foreground collector to do
810 // a mark-sweep-compact.
811 void do_compaction_work(bool clear_all_soft_refs);
812
813 // Work methods for reporting concurrent mode interruption or failure
814 bool is_external_interruption();
815 void report_concurrent_mode_interruption();
816
817 // If the background GC is active, acquire control from the background
818 // GC and do the collection.
819 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
820
821 // For synchronizing passing of control from background to foreground
822 // GC. waitForForegroundGC() is called by the background
823 // collector. It if had to wait for a foreground collection,
824 // it returns true and the background collection should assume
825 // that the collection was finished by the foreground
826 // collector.
827 bool waitForForegroundGC();
828
829 size_t block_size_using_printezis_bits(HeapWord* addr) const;
830 size_t block_size_if_printezis_bits(HeapWord* addr) const;
831 HeapWord* next_card_start_after_block(HeapWord* addr) const;
832
833 void setup_cms_unloading_and_verification_state();
834 public:
835 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
836 CardTableRS* ct,
837 ConcurrentMarkSweepPolicy* cp);
838 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
839
840 ReferenceProcessor* ref_processor() { return _ref_processor; }
841 void ref_processor_init();
842
843 Mutex* bitMapLock() const { return _markBitMap.lock(); }
844 static CollectorState abstract_state() { return _collectorState; }
845
846 bool should_abort_preclean() const; // Whether preclean should be aborted.
847 size_t get_eden_used() const;
848 size_t get_eden_capacity() const;
849
850 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
851
852 // Locking checks
853 NOT_PRODUCT(static bool have_cms_token();)
854
855 bool shouldConcurrentCollect();
856
857 void collect(bool full,
858 bool clear_all_soft_refs,
859 size_t size,
860 bool tlab);
861 void collect_in_background(GCCause::Cause cause);
862
863 // In support of ExplicitGCInvokesConcurrent
864 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
865 // Should we unload classes in a particular concurrent cycle?
866 bool should_unload_classes() const {
867 return _should_unload_classes;
868 }
869 void update_should_unload_classes();
870
871 void direct_allocated(HeapWord* start, size_t size);
872
873 // Object is dead if not marked and current phase is sweeping.
874 bool is_dead_obj(oop obj) const;
875
876 // After a promotion (of "start"), do any necessary marking.
877 // If "par", then it's being done by a parallel GC thread.
878 // The last two args indicate if we need precise marking
879 // and if so the size of the object so it can be dirtied
880 // in its entirety.
881 void promoted(bool par, HeapWord* start,
882 bool is_obj_array, size_t obj_size);
883
884 void getFreelistLocks() const;
885 void releaseFreelistLocks() const;
886 bool haveFreelistLocks() const;
887
888 // Adjust size of underlying generation
889 void compute_new_size();
890
891 // GC prologue and epilogue
892 void gc_prologue(bool full);
893 void gc_epilogue(bool full);
894
895 jlong time_of_last_gc(jlong now) {
896 if (_collectorState <= Idling) {
897 // gc not in progress
898 return _time_of_last_gc;
899 } else {
900 // collection in progress
901 return now;
902 }
903 }
904
905 // Support for parallel remark of survivor space
906 void* get_data_recorder(int thr_num);
907 void sample_eden_chunk();
908
909 CMSBitMap* markBitMap() { return &_markBitMap; }
910 void directAllocated(HeapWord* start, size_t size);
911
912 // Main CMS steps and related support
913 void checkpointRootsInitial();
914 bool markFromRoots(); // a return value of false indicates failure
915 // due to stack overflow
916 void preclean();
917 void checkpointRootsFinal();
918 void sweep();
919
920 // Check that the currently executing thread is the expected
921 // one (foreground collector or background collector).
922 static void check_correct_thread_executing() PRODUCT_RETURN;
923
924 bool is_cms_reachable(HeapWord* addr);
925
926 // Performance Counter Support
927 CollectorCounters* counters() { return _gc_counters; }
928
929 // Timer stuff
930 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
931 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
932 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
933 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
934
935 int yields() { return _numYields; }
936 void resetYields() { _numYields = 0; }
937 void incrementYields() { _numYields++; }
938 void resetNumDirtyCards() { _numDirtyCards = 0; }
939 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
940 size_t numDirtyCards() { return _numDirtyCards; }
941
942 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
943 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
944 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
945 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
946 size_t sweep_count() const { return _sweep_count; }
947 void increment_sweep_count() { _sweep_count++; }
948
949 // Timers/stats for gc scheduling and incremental mode pacing.
950 CMSStats& stats() { return _stats; }
951
952 // Adaptive size policy
953 AdaptiveSizePolicy* size_policy();
954
955 static void print_on_error(outputStream* st);
956
957 // Debugging
958 void verify();
959 bool verify_after_remark(bool silent = VerifySilently);
960 void verify_ok_to_terminate() const PRODUCT_RETURN;
961 void verify_work_stacks_empty() const PRODUCT_RETURN;
962 void verify_overflow_empty() const PRODUCT_RETURN;
963
964 // Convenience methods in support of debugging
965 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
966 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
967
968 // Accessors
969 CMSMarkStack* verification_mark_stack() { return &_markStack; }
970 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
971
972 // Initialization errors
973 bool completed_initialization() { return _completed_initialization; }
974
975 void print_eden_and_survivor_chunk_arrays();
976 };
977
978 class CMSExpansionCause : public AllStatic {
979 public:
980 enum Cause {
981 _no_expansion,
982 _satisfy_free_ratio,
983 _satisfy_promotion,
984 _satisfy_allocation,
985 _allocate_par_lab,
986 _allocate_par_spooling_space,
987 _adaptive_size_policy
988 };
989 // Return a string describing the cause of the expansion.
990 static const char* to_string(CMSExpansionCause::Cause cause);
991 };
992
993 class ConcurrentMarkSweepGeneration: public CardGeneration {
994 friend class VMStructs;
995 friend class ConcurrentMarkSweepThread;
996 friend class ConcurrentMarkSweep;
997 friend class CMSCollector;
998 protected:
999 static CMSCollector* _collector; // the collector that collects us
1000 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1001
1002 // Performance Counters
1003 GenerationCounters* _gen_counters;
1004 GSpaceCounters* _space_counters;
1005
1006 // Words directly allocated, used by CMSStats.
1007 size_t _direct_allocated_words;
1008
1009 // Non-product stat counters
1010 NOT_PRODUCT(
1011 size_t _numObjectsPromoted;
1012 size_t _numWordsPromoted;
1013 size_t _numObjectsAllocated;
1014 size_t _numWordsAllocated;
1015 )
1016
1017 // Used for sizing decisions
1018 bool _incremental_collection_failed;
1019 bool incremental_collection_failed() {
1020 return _incremental_collection_failed;
1021 }
1022 void set_incremental_collection_failed() {
1023 _incremental_collection_failed = true;
1024 }
1025 void clear_incremental_collection_failed() {
1026 _incremental_collection_failed = false;
1027 }
1028
1029 // accessors
1030 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1031 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1032
1033 private:
1034 // For parallel young-gen GC support.
1035 CMSParGCThreadState** _par_gc_thread_states;
1036
1037 // Reason generation was expanded
1038 CMSExpansionCause::Cause _expansion_cause;
1039
1040 // In support of MinChunkSize being larger than min object size
1041 const double _dilatation_factor;
1042
1043 // True if a compacting collection was done.
1044 bool _did_compact;
1045 bool did_compact() { return _did_compact; }
1046
1047 // Fraction of current occupancy at which to start a CMS collection which
1048 // will collect this generation (at least).
1049 double _initiating_occupancy;
1050
1051 protected:
1052 // Shrink generation by specified size (returns false if unable to shrink)
1053 void shrink_free_list_by(size_t bytes);
1054
1055 // Update statistics for GC
1056 virtual void update_gc_stats(int level, bool full);
1057
1058 // Maximum available space in the generation (including uncommitted)
1059 // space.
1060 size_t max_available() const;
1061
1062 // getter and initializer for _initiating_occupancy field.
1063 double initiating_occupancy() const { return _initiating_occupancy; }
1064 void init_initiating_occupancy(intx io, uintx tr);
1065
1066 public:
1067 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1068 int level, CardTableRS* ct,
1069 bool use_adaptive_freelists,
1070 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1071
1072 // Accessors
1073 CMSCollector* collector() const { return _collector; }
1074 static void set_collector(CMSCollector* collector) {
1075 assert(_collector == NULL, "already set");
1076 _collector = collector;
1077 }
1078 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1079
1080 Mutex* freelistLock() const;
1081
1082 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1083
1084 void set_did_compact(bool v) { _did_compact = v; }
1085
1086 bool refs_discovery_is_atomic() const { return false; }
1087 bool refs_discovery_is_mt() const {
1088 // Note: CMS does MT-discovery during the parallel-remark
1089 // phases. Use ReferenceProcessorMTMutator to make refs
1090 // discovery MT-safe during such phases or other parallel
1091 // discovery phases in the future. This may all go away
1092 // if/when we decide that refs discovery is sufficiently
1093 // rare that the cost of the CAS's involved is in the
1094 // noise. That's a measurement that should be done, and
1095 // the code simplified if that turns out to be the case.
1096 return ConcGCThreads > 1;
1097 }
1098
1099 // Override
1100 virtual void ref_processor_init();
1101
1102 // Grow generation by specified size (returns false if unable to grow)
1103 bool grow_by(size_t bytes);
1104 // Grow generation to reserved size.
1105 bool grow_to_reserved();
1106
1107 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1108
1109 // Space enquiries
1110 size_t capacity() const;
1111 size_t used() const;
1112 size_t free() const;
1113 double occupancy() const { return ((double)used())/((double)capacity()); }
1114 size_t contiguous_available() const;
1115 size_t unsafe_max_alloc_nogc() const;
1116
1117 // over-rides
1118 MemRegion used_region() const;
1119 MemRegion used_region_at_save_marks() const;
1120
1121 // Does a "full" (forced) collection invoked on this generation collect
1122 // all younger generations as well? Note that the second conjunct is a
1123 // hack to allow the collection of the younger gen first if the flag is
1124 // set.
1125 virtual bool full_collects_younger_generations() const {
1126 return !ScavengeBeforeFullGC;
1127 }
1128
1129 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1130
1131 // Support for compaction
1132 CompactibleSpace* first_compaction_space() const;
1133 // Adjust quantities in the generation affected by
1134 // the compaction.
1135 void reset_after_compaction();
1136
1137 // Allocation support
1138 HeapWord* allocate(size_t size, bool tlab);
1139 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1140 oop promote(oop obj, size_t obj_size);
1141 HeapWord* par_allocate(size_t size, bool tlab) {
1142 return allocate(size, tlab);
1143 }
1144
1145
1146 // Used by CMSStats to track direct allocation. The value is sampled and
1147 // reset after each young gen collection.
1148 size_t direct_allocated_words() const { return _direct_allocated_words; }
1149 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1150
1151 // Overrides for parallel promotion.
1152 virtual oop par_promote(int thread_num,
1153 oop obj, markOop m, size_t word_sz);
1154 // This one should not be called for CMS.
1155 virtual void par_promote_alloc_undo(int thread_num,
1156 HeapWord* obj, size_t word_sz);
1157 virtual void par_promote_alloc_done(int thread_num);
1158 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1159
1160 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1161
1162 // Inform this (non-young) generation that a promotion failure was
1163 // encountered during a collection of a younger generation that
1164 // promotes into this generation.
1165 virtual void promotion_failure_occurred();
1166
1167 bool should_collect(bool full, size_t size, bool tlab);
1168 virtual bool should_concurrent_collect() const;
1169 virtual bool is_too_full() const;
1170 void collect(bool full,
1171 bool clear_all_soft_refs,
1172 size_t size,
1173 bool tlab);
1174
1175 HeapWord* expand_and_allocate(size_t word_size,
1176 bool tlab,
1177 bool parallel = false);
1178
1179 // GC prologue and epilogue
1180 void gc_prologue(bool full);
1181 void gc_prologue_work(bool full, bool registerClosure,
1182 ModUnionClosure* modUnionClosure);
1183 void gc_epilogue(bool full);
1184 void gc_epilogue_work(bool full);
1185
1186 // Time since last GC of this generation
1187 jlong time_of_last_gc(jlong now) {
1188 return collector()->time_of_last_gc(now);
1189 }
1190 void update_time_of_last_gc(jlong now) {
1191 collector()-> update_time_of_last_gc(now);
1192 }
1193
1194 // Allocation failure
1195 void expand(size_t bytes, size_t expand_bytes,
1196 CMSExpansionCause::Cause cause);
1197 virtual bool expand(size_t bytes, size_t expand_bytes);
1198 void shrink(size_t bytes);
1199 void shrink_by(size_t bytes);
1200 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1201 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1202
1203 // Iteration support and related enquiries
1204 void save_marks();
1205 bool no_allocs_since_save_marks();
1206 void younger_refs_iterate(OopsInGenClosure* cl);
1207
1208 // Iteration support specific to CMS generations
1209 void save_sweep_limit();
1210
1211 // More iteration support
1212 virtual void oop_iterate(ExtendedOopClosure* cl);
1213 virtual void safe_object_iterate(ObjectClosure* cl);
1214 virtual void object_iterate(ObjectClosure* cl);
1215
1216 // Need to declare the full complement of closures, whether we'll
1217 // override them or not, or get message from the compiler:
1218 // oop_since_save_marks_iterate_nv hides virtual function...
1219 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1220 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1221 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1222
1223 // Smart allocation XXX -- move to CFLSpace?
1224 void setNearLargestChunk();
1225 bool isNearLargestChunk(HeapWord* addr);
1226
1227 // Get the chunk at the end of the space. Delegates to
1228 // the space.
1229 FreeChunk* find_chunk_at_end();
1230
1231 void post_compact();
1232
1233 // Debugging
1234 void prepare_for_verify();
1235 void verify();
1236 void print_statistics() PRODUCT_RETURN;
1237
1238 // Performance Counters support
1239 virtual void update_counters();
1240 virtual void update_counters(size_t used);
1241 void initialize_performance_counters();
1242 CollectorCounters* counters() { return collector()->counters(); }
1243
1244 // Support for parallel remark of survivor space
1245 void* get_data_recorder(int thr_num) {
1246 //Delegate to collector
1247 return collector()->get_data_recorder(thr_num);
1248 }
1249 void sample_eden_chunk() {
1250 //Delegate to collector
1251 return collector()->sample_eden_chunk();
1252 }
1253
1254 // Printing
1255 const char* name() const;
1256 virtual const char* short_name() const { return "CMS"; }
1257 void print() const;
1258 void printOccupancy(const char* s);
1259 bool must_be_youngest() const { return false; }
1260 bool must_be_oldest() const { return true; }
1261
1262 // Resize the generation after a compacting GC. The
1263 // generation can be treated as a contiguous space
1264 // after the compaction.
1265 virtual void compute_new_size();
1266 // Resize the generation after a non-compacting
1267 // collection.
1268 void compute_new_size_free_list();
1269 };
1270
1271 //
1272 // Closures of various sorts used by CMS to accomplish its work
1273 //
1274
1275 // This closure is used to do concurrent marking from the roots
1276 // following the first checkpoint.
1277 class MarkFromRootsClosure: public BitMapClosure {
1278 CMSCollector* _collector;
1279 MemRegion _span;
1280 CMSBitMap* _bitMap;
1281 CMSBitMap* _mut;
1282 CMSMarkStack* _markStack;
1283 bool _yield;
1284 int _skipBits;
1285 HeapWord* _finger;
1286 HeapWord* _threshold;
1287 DEBUG_ONLY(bool _verifying;)
1288
1289 public:
1290 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1291 CMSBitMap* bitMap,
1292 CMSMarkStack* markStack,
1293 bool should_yield, bool verifying = false);
1294 bool do_bit(size_t offset);
1295 void reset(HeapWord* addr);
1296 inline void do_yield_check();
1297
1298 private:
1299 void scanOopsInOop(HeapWord* ptr);
1300 void do_yield_work();
1301 };
1302
1303 // This closure is used to do concurrent multi-threaded
1304 // marking from the roots following the first checkpoint.
1305 // XXX This should really be a subclass of The serial version
1306 // above, but i have not had the time to refactor things cleanly.
1307 class Par_MarkFromRootsClosure: public BitMapClosure {
1308 CMSCollector* _collector;
1309 MemRegion _whole_span;
1310 MemRegion _span;
1311 CMSBitMap* _bit_map;
1312 CMSBitMap* _mut;
1313 OopTaskQueue* _work_queue;
1314 CMSMarkStack* _overflow_stack;
1315 int _skip_bits;
1316 HeapWord* _finger;
1317 HeapWord* _threshold;
1318 CMSConcMarkingTask* _task;
1319 public:
1320 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1321 MemRegion span,
1322 CMSBitMap* bit_map,
1323 OopTaskQueue* work_queue,
1324 CMSMarkStack* overflow_stack);
1325 bool do_bit(size_t offset);
1326 inline void do_yield_check();
1327
1328 private:
1329 void scan_oops_in_oop(HeapWord* ptr);
1330 void do_yield_work();
1331 bool get_work_from_overflow_stack();
1332 };
1333
1334 // The following closures are used to do certain kinds of verification of
1335 // CMS marking.
1336 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1337 CMSCollector* _collector;
1338 MemRegion _span;
1339 CMSBitMap* _verification_bm;
1340 CMSBitMap* _cms_bm;
1341 CMSMarkStack* _mark_stack;
1342 protected:
1343 void do_oop(oop p);
1344 template <class T> inline void do_oop_work(T *p) {
1345 oop obj = oopDesc::load_decode_heap_oop(p);
1346 do_oop(obj);
1347 }
1348 public:
1349 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1350 MemRegion span,
1351 CMSBitMap* verification_bm,
1352 CMSBitMap* cms_bm,
1353 CMSMarkStack* mark_stack);
1354 void do_oop(oop* p);
1355 void do_oop(narrowOop* p);
1356
1357 // Deal with a stack overflow condition
1358 void handle_stack_overflow(HeapWord* lost);
1359 };
1360
1361 class MarkFromRootsVerifyClosure: public BitMapClosure {
1362 CMSCollector* _collector;
1363 MemRegion _span;
1364 CMSBitMap* _verification_bm;
1365 CMSBitMap* _cms_bm;
1366 CMSMarkStack* _mark_stack;
1367 HeapWord* _finger;
1368 PushAndMarkVerifyClosure _pam_verify_closure;
1369 public:
1370 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1371 CMSBitMap* verification_bm,
1372 CMSBitMap* cms_bm,
1373 CMSMarkStack* mark_stack);
1374 bool do_bit(size_t offset);
1375 void reset(HeapWord* addr);
1376 };
1377
1378
1379 // This closure is used to check that a certain set of bits is
1380 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1381 class FalseBitMapClosure: public BitMapClosure {
1382 public:
1383 bool do_bit(size_t offset) {
1384 guarantee(false, "Should not have a 1 bit");
1385 return true;
1386 }
1387 };
1388
1389 // A version of ObjectClosure with "memory" (see _previous_address below)
1390 class UpwardsObjectClosure: public BoolObjectClosure {
1391 HeapWord* _previous_address;
1392 public:
1393 UpwardsObjectClosure() : _previous_address(NULL) { }
1394 void set_previous(HeapWord* addr) { _previous_address = addr; }
1395 HeapWord* previous() { return _previous_address; }
1396 // A return value of "true" can be used by the caller to decide
1397 // if this object's end should *NOT* be recorded in
1398 // _previous_address above.
1399 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1400 };
1401
1402 // This closure is used during the second checkpointing phase
1403 // to rescan the marked objects on the dirty cards in the mod
1404 // union table and the card table proper. It's invoked via
1405 // MarkFromDirtyCardsClosure below. It uses either
1406 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1407 // declared in genOopClosures.hpp to accomplish some of its work.
1408 // In the parallel case the bitMap is shared, so access to
1409 // it needs to be suitably synchronized for updates by embedded
1410 // closures that update it; however, this closure itself only
1411 // reads the bit_map and because it is idempotent, is immune to
1412 // reading stale values.
1413 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1414 #ifdef ASSERT
1415 CMSCollector* _collector;
1416 MemRegion _span;
1417 union {
1418 CMSMarkStack* _mark_stack;
1419 OopTaskQueue* _work_queue;
1420 };
1421 #endif // ASSERT
1422 bool _parallel;
1423 CMSBitMap* _bit_map;
1424 union {
1425 MarkRefsIntoAndScanClosure* _scan_closure;
1426 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1427 };
1428
1429 public:
1430 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1431 MemRegion span,
1432 ReferenceProcessor* rp,
1433 CMSBitMap* bit_map,
1434 CMSMarkStack* mark_stack,
1435 MarkRefsIntoAndScanClosure* cl):
1436 #ifdef ASSERT
1437 _collector(collector),
1438 _span(span),
1439 _mark_stack(mark_stack),
1440 #endif // ASSERT
1441 _parallel(false),
1442 _bit_map(bit_map),
1443 _scan_closure(cl) { }
1444
1445 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1446 MemRegion span,
1447 ReferenceProcessor* rp,
1448 CMSBitMap* bit_map,
1449 OopTaskQueue* work_queue,
1450 Par_MarkRefsIntoAndScanClosure* cl):
1451 #ifdef ASSERT
1452 _collector(collector),
1453 _span(span),
1454 _work_queue(work_queue),
1455 #endif // ASSERT
1456 _parallel(true),
1457 _bit_map(bit_map),
1458 _par_scan_closure(cl) { }
1459
1460 bool do_object_b(oop obj) {
1461 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1462 return false;
1463 }
1464 bool do_object_bm(oop p, MemRegion mr);
1465 };
1466
1467 // This closure is used during the second checkpointing phase
1468 // to rescan the marked objects on the dirty cards in the mod
1469 // union table and the card table proper. It invokes
1470 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1471 // In the parallel case, the bit map is shared and requires
1472 // synchronized access.
1473 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1474 CompactibleFreeListSpace* _space;
1475 ScanMarkedObjectsAgainClosure _scan_cl;
1476 size_t _num_dirty_cards;
1477
1478 public:
1479 MarkFromDirtyCardsClosure(CMSCollector* collector,
1480 MemRegion span,
1481 CompactibleFreeListSpace* space,
1482 CMSBitMap* bit_map,
1483 CMSMarkStack* mark_stack,
1484 MarkRefsIntoAndScanClosure* cl):
1485 _space(space),
1486 _num_dirty_cards(0),
1487 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1488 mark_stack, cl) { }
1489
1490 MarkFromDirtyCardsClosure(CMSCollector* collector,
1491 MemRegion span,
1492 CompactibleFreeListSpace* space,
1493 CMSBitMap* bit_map,
1494 OopTaskQueue* work_queue,
1495 Par_MarkRefsIntoAndScanClosure* cl):
1496 _space(space),
1497 _num_dirty_cards(0),
1498 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1499 work_queue, cl) { }
1500
1501 void do_MemRegion(MemRegion mr);
1502 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1503 size_t num_dirty_cards() { return _num_dirty_cards; }
1504 };
1505
1506 // This closure is used in the non-product build to check
1507 // that there are no MemRegions with a certain property.
1508 class FalseMemRegionClosure: public MemRegionClosure {
1509 void do_MemRegion(MemRegion mr) {
1510 guarantee(!mr.is_empty(), "Shouldn't be empty");
1511 guarantee(false, "Should never be here");
1512 }
1513 };
1514
1515 // This closure is used during the precleaning phase
1516 // to "carefully" rescan marked objects on dirty cards.
1517 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1518 // to accomplish some of its work.
1519 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1520 CMSCollector* _collector;
1521 MemRegion _span;
1522 bool _yield;
1523 Mutex* _freelistLock;
1524 CMSBitMap* _bitMap;
1525 CMSMarkStack* _markStack;
1526 MarkRefsIntoAndScanClosure* _scanningClosure;
1527
1528 public:
1529 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1530 MemRegion span,
1531 CMSBitMap* bitMap,
1532 CMSMarkStack* markStack,
1533 MarkRefsIntoAndScanClosure* cl,
1534 bool should_yield):
1535 _collector(collector),
1536 _span(span),
1537 _yield(should_yield),
1538 _bitMap(bitMap),
1539 _markStack(markStack),
1540 _scanningClosure(cl) {
1541 }
1542
1543 void do_object(oop p) {
1544 guarantee(false, "call do_object_careful instead");
1545 }
1546
1547 size_t do_object_careful(oop p) {
1548 guarantee(false, "Unexpected caller");
1549 return 0;
1550 }
1551
1552 size_t do_object_careful_m(oop p, MemRegion mr);
1553
1554 void setFreelistLock(Mutex* m) {
1555 _freelistLock = m;
1556 _scanningClosure->set_freelistLock(m);
1557 }
1558
1559 private:
1560 inline bool do_yield_check();
1561
1562 void do_yield_work();
1563 };
1564
1565 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1566 CMSCollector* _collector;
1567 MemRegion _span;
1568 bool _yield;
1569 CMSBitMap* _bit_map;
1570 CMSMarkStack* _mark_stack;
1571 PushAndMarkClosure* _scanning_closure;
1572 unsigned int _before_count;
1573
1574 public:
1575 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1576 MemRegion span,
1577 CMSBitMap* bit_map,
1578 CMSMarkStack* mark_stack,
1579 PushAndMarkClosure* cl,
1580 unsigned int before_count,
1581 bool should_yield):
1582 _collector(collector),
1583 _span(span),
1584 _yield(should_yield),
1585 _bit_map(bit_map),
1586 _mark_stack(mark_stack),
1587 _scanning_closure(cl),
1588 _before_count(before_count)
1589 { }
1590
1591 void do_object(oop p) {
1592 guarantee(false, "call do_object_careful instead");
1593 }
1594
1595 size_t do_object_careful(oop p);
1596
1597 size_t do_object_careful_m(oop p, MemRegion mr) {
1598 guarantee(false, "Unexpected caller");
1599 return 0;
1600 }
1601
1602 private:
1603 inline void do_yield_check();
1604 void do_yield_work();
1605 };
1606
1607 // This closure is used to accomplish the sweeping work
1608 // after the second checkpoint but before the concurrent reset
1609 // phase.
1610 //
1611 // Terminology
1612 // left hand chunk (LHC) - block of one or more chunks currently being
1613 // coalesced. The LHC is available for coalescing with a new chunk.
1614 // right hand chunk (RHC) - block that is currently being swept that is
1615 // free or garbage that can be coalesced with the LHC.
1616 // _inFreeRange is true if there is currently a LHC
1617 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1618 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1619 // _freeFinger is the address of the current LHC
1620 class SweepClosure: public BlkClosureCareful {
1621 CMSCollector* _collector; // collector doing the work
1622 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1623 CompactibleFreeListSpace* _sp; // Space being swept
1624 HeapWord* _limit;// the address at or above which the sweep should stop
1625 // because we do not expect newly garbage blocks
1626 // eligible for sweeping past that address.
1627 Mutex* _freelistLock; // Free list lock (in space)
1628 CMSBitMap* _bitMap; // Marking bit map (in
1629 // generation)
1630 bool _inFreeRange; // Indicates if we are in the
1631 // midst of a free run
1632 bool _freeRangeInFreeLists;
1633 // Often, we have just found
1634 // a free chunk and started
1635 // a new free range; we do not
1636 // eagerly remove this chunk from
1637 // the free lists unless there is
1638 // a possibility of coalescing.
1639 // When true, this flag indicates
1640 // that the _freeFinger below
1641 // points to a potentially free chunk
1642 // that may still be in the free lists
1643 bool _lastFreeRangeCoalesced;
1644 // free range contains chunks
1645 // coalesced
1646 bool _yield;
1647 // Whether sweeping should be
1648 // done with yields. For instance
1649 // when done by the foreground
1650 // collector we shouldn't yield.
1651 HeapWord* _freeFinger; // When _inFreeRange is set, the
1652 // pointer to the "left hand
1653 // chunk"
1654 size_t _freeRangeSize;
1655 // When _inFreeRange is set, this
1656 // indicates the accumulated size
1657 // of the "left hand chunk"
1658 NOT_PRODUCT(
1659 size_t _numObjectsFreed;
1660 size_t _numWordsFreed;
1661 size_t _numObjectsLive;
1662 size_t _numWordsLive;
1663 size_t _numObjectsAlreadyFree;
1664 size_t _numWordsAlreadyFree;
1665 FreeChunk* _last_fc;
1666 )
1667 private:
1668 // Code that is common to a free chunk or garbage when
1669 // encountered during sweeping.
1670 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1671 // Process a free chunk during sweeping.
1672 void do_already_free_chunk(FreeChunk *fc);
1673 // Work method called when processing an already free or a
1674 // freshly garbage chunk to do a lookahead and possibly a
1675 // preemptive flush if crossing over _limit.
1676 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1677 // Process a garbage chunk during sweeping.
1678 size_t do_garbage_chunk(FreeChunk *fc);
1679 // Process a live chunk during sweeping.
1680 size_t do_live_chunk(FreeChunk* fc);
1681
1682 // Accessors.
1683 HeapWord* freeFinger() const { return _freeFinger; }
1684 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1685 bool inFreeRange() const { return _inFreeRange; }
1686 void set_inFreeRange(bool v) { _inFreeRange = v; }
1687 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1688 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1689 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1690 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1691
1692 // Initialize a free range.
1693 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1694 // Return this chunk to the free lists.
1695 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1696
1697 // Check if we should yield and do so when necessary.
1698 inline void do_yield_check(HeapWord* addr);
1699
1700 // Yield
1701 void do_yield_work(HeapWord* addr);
1702
1703 // Debugging/Printing
1704 void print_free_block_coalesced(FreeChunk* fc) const;
1705
1706 public:
1707 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1708 CMSBitMap* bitMap, bool should_yield);
1709 ~SweepClosure() PRODUCT_RETURN;
1710
1711 size_t do_blk_careful(HeapWord* addr);
1712 void print() const { print_on(tty); }
1713 void print_on(outputStream *st) const;
1714 };
1715
1716 // Closures related to weak references processing
1717
1718 // During CMS' weak reference processing, this is a
1719 // work-routine/closure used to complete transitive
1720 // marking of objects as live after a certain point
1721 // in which an initial set has been completely accumulated.
1722 // This closure is currently used both during the final
1723 // remark stop-world phase, as well as during the concurrent
1724 // precleaning of the discovered reference lists.
1725 class CMSDrainMarkingStackClosure: public VoidClosure {
1726 CMSCollector* _collector;
1727 MemRegion _span;
1728 CMSMarkStack* _mark_stack;
1729 CMSBitMap* _bit_map;
1730 CMSKeepAliveClosure* _keep_alive;
1731 bool _concurrent_precleaning;
1732 public:
1733 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1734 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1735 CMSKeepAliveClosure* keep_alive,
1736 bool cpc):
1737 _collector(collector),
1738 _span(span),
1739 _bit_map(bit_map),
1740 _mark_stack(mark_stack),
1741 _keep_alive(keep_alive),
1742 _concurrent_precleaning(cpc) {
1743 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1744 "Mismatch");
1745 }
1746
1747 void do_void();
1748 };
1749
1750 // A parallel version of CMSDrainMarkingStackClosure above.
1751 class CMSParDrainMarkingStackClosure: public VoidClosure {
1752 CMSCollector* _collector;
1753 MemRegion _span;
1754 OopTaskQueue* _work_queue;
1755 CMSBitMap* _bit_map;
1756 CMSInnerParMarkAndPushClosure _mark_and_push;
1757
1758 public:
1759 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1760 MemRegion span, CMSBitMap* bit_map,
1761 OopTaskQueue* work_queue):
1762 _collector(collector),
1763 _span(span),
1764 _bit_map(bit_map),
1765 _work_queue(work_queue),
1766 _mark_and_push(collector, span, bit_map, work_queue) { }
1767
1768 public:
1769 void trim_queue(uint max);
1770 void do_void();
1771 };
1772
1773 // Allow yielding or short-circuiting of reference list
1774 // precleaning work.
1775 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1776 CMSCollector* _collector;
1777 void do_yield_work();
1778 public:
1779 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1780 _collector(collector) {}
1781 virtual bool should_return();
1782 };
1783
1784
1785 // Convenience class that locks free list locks for given CMS collector
1786 class FreelistLocker: public StackObj {
1787 private:
1788 CMSCollector* _collector;
1789 public:
1790 FreelistLocker(CMSCollector* collector):
1791 _collector(collector) {
1792 _collector->getFreelistLocks();
1793 }
1794
1795 ~FreelistLocker() {
1796 _collector->releaseFreelistLocks();
1797 }
1798 };
1799
1800 // Mark all dead objects in a given space.
1801 class MarkDeadObjectsClosure: public BlkClosure {
1802 const CMSCollector* _collector;
1803 const CompactibleFreeListSpace* _sp;
1804 CMSBitMap* _live_bit_map;
1805 CMSBitMap* _dead_bit_map;
1806 public:
1807 MarkDeadObjectsClosure(const CMSCollector* collector,
1808 const CompactibleFreeListSpace* sp,
1809 CMSBitMap *live_bit_map,
1810 CMSBitMap *dead_bit_map) :
1811 _collector(collector),
1812 _sp(sp),
1813 _live_bit_map(live_bit_map),
1814 _dead_bit_map(dead_bit_map) {}
1815 size_t do_blk(HeapWord* addr);
1816 };
1817
1818 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1819
1820 public:
1821 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1822 };
1823
1824
1825 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP