1 /*
2 * Copyright (c) 2001, 2014, 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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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/cardGeneration.hpp"
34 #include "memory/freeBlockDictionary.hpp"
35 #include "memory/iterator.hpp"
36 #include "memory/space.hpp"
37 #include "runtime/mutexLocker.hpp"
38 #include "runtime/virtualspace.hpp"
39 #include "services/memoryService.hpp"
40 #include "utilities/bitMap.inline.hpp"
41 #include "utilities/stack.inline.hpp"
42 #include "utilities/taskqueue.hpp"
43 #include "utilities/yieldingWorkgroup.hpp"
44
45 // ConcurrentMarkSweepGeneration is in support of a concurrent
46 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
47 // style. We assume, for now, that this generation is always the
48 // seniormost generation and for simplicity
49 // in the first implementation, that this generation is a single compactible
50 // space. Neither of these restrictions appears essential, and will be
51 // relaxed in the future when more time is available to implement the
52 // greater generality (and there's a need for it).
53 //
54 // Concurrent mode failures are currently handled by
55 // means of a sliding mark-compact.
56
57 class AdaptiveSizePolicy;
58 class CMSConcMarkingTask;
59 class CMSGCAdaptivePolicyCounters;
60 class CMSTracer;
61 class ConcurrentGCTimer;
62 class ConcurrentMarkSweepGeneration;
63 class ConcurrentMarkSweepPolicy;
64 class ConcurrentMarkSweepThread;
65 class CompactibleFreeListSpace;
66 class FreeChunk;
67 class PromotionInfo;
68 class ScanMarkedObjectsAgainCarefullyClosure;
69 class TenuredGeneration;
70 class SerialOldTracer;
71
72 // A generic CMS bit map. It's the basis for both the CMS marking bit map
73 // as well as for the mod union table (in each case only a subset of the
74 // methods are used). This is essentially a wrapper around the BitMap class,
75 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
76 // we have _shifter == 0. and for the mod union table we have
77 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
78 // XXX 64-bit issues in BitMap?
79 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
80 friend class VMStructs;
81
82 HeapWord* _bmStartWord; // base address of range covered by map
83 size_t _bmWordSize; // map size (in #HeapWords covered)
84 const int _shifter; // shifts to convert HeapWord to bit position
85 VirtualSpace _virtual_space; // underlying the bit map
86 BitMap _bm; // the bit map itself
87 public:
88 Mutex* const _lock; // mutex protecting _bm;
89
90 public:
91 // constructor
92 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
93
94 // allocates the actual storage for the map
95 bool allocate(MemRegion mr);
96 // field getter
97 Mutex* lock() const { return _lock; }
98 // locking verifier convenience function
99 void assert_locked() const PRODUCT_RETURN;
100
101 // inquiries
102 HeapWord* startWord() const { return _bmStartWord; }
103 size_t sizeInWords() const { return _bmWordSize; }
104 size_t sizeInBits() const { return _bm.size(); }
105 // the following is one past the last word in space
106 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
107
108 // reading marks
109 bool isMarked(HeapWord* addr) const;
110 bool par_isMarked(HeapWord* addr) const; // do not lock checks
111 bool isUnmarked(HeapWord* addr) const;
112 bool isAllClear() const;
113
114 // writing marks
115 void mark(HeapWord* addr);
116 // For marking by parallel GC threads;
117 // returns true if we did, false if another thread did
118 bool par_mark(HeapWord* addr);
119
120 void mark_range(MemRegion mr);
121 void par_mark_range(MemRegion mr);
122 void mark_large_range(MemRegion mr);
123 void par_mark_large_range(MemRegion mr);
124 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
125 void clear_range(MemRegion mr);
126 void par_clear_range(MemRegion mr);
127 void clear_large_range(MemRegion mr);
128 void par_clear_large_range(MemRegion mr);
129 void clear_all();
130 void clear_all_incrementally(); // Not yet implemented!!
131
132 NOT_PRODUCT(
133 // checks the memory region for validity
134 void region_invariant(MemRegion mr);
135 )
136
137 // iteration
138 void iterate(BitMapClosure* cl) {
139 _bm.iterate(cl);
140 }
141 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
142 void dirty_range_iterate_clear(MemRegionClosure* cl);
143 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
144
145 // auxiliary support for iteration
146 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
147 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
148 HeapWord* end_addr) const;
149 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
150 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
151 HeapWord* end_addr) const;
152 MemRegion getAndClearMarkedRegion(HeapWord* addr);
153 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
154 HeapWord* end_addr);
155
156 // conversion utilities
157 HeapWord* offsetToHeapWord(size_t offset) const;
158 size_t heapWordToOffset(HeapWord* addr) const;
159 size_t heapWordDiffToOffsetDiff(size_t diff) const;
160
161 void print_on_error(outputStream* st, const char* prefix) const;
162
163 // debugging
164 // is this address range covered by the bit-map?
165 NOT_PRODUCT(
166 bool covers(MemRegion mr) const;
167 bool covers(HeapWord* start, size_t size = 0) const;
168 )
169 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
170 };
171
172 // Represents a marking stack used by the CMS collector.
173 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
174 class CMSMarkStack: public CHeapObj<mtGC> {
175 //
176 friend class CMSCollector; // To get at expansion stats further below.
177 //
178
179 VirtualSpace _virtual_space; // Space for the stack
180 oop* _base; // Bottom of stack
181 size_t _index; // One more than last occupied index
182 size_t _capacity; // Max #elements
183 Mutex _par_lock; // An advisory lock used in case of parallel access
184 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run
185
186 protected:
187 size_t _hit_limit; // We hit max stack size limit
188 size_t _failed_double; // We failed expansion before hitting limit
189
190 public:
191 CMSMarkStack():
192 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
193 _hit_limit(0),
194 _failed_double(0) {}
195
196 bool allocate(size_t size);
197
198 size_t capacity() const { return _capacity; }
199
200 oop pop() {
201 if (!isEmpty()) {
202 return _base[--_index] ;
203 }
204 return NULL;
205 }
206
207 bool push(oop ptr) {
208 if (isFull()) {
209 return false;
210 } else {
211 _base[_index++] = ptr;
212 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
213 return true;
214 }
215 }
216
217 bool isEmpty() const { return _index == 0; }
218 bool isFull() const {
219 assert(_index <= _capacity, "buffer overflow");
220 return _index == _capacity;
221 }
222
223 size_t length() { return _index; }
224
225 // "Parallel versions" of some of the above
226 oop par_pop() {
227 // lock and pop
228 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
229 return pop();
230 }
231
232 bool par_push(oop ptr) {
233 // lock and push
234 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
235 return push(ptr);
236 }
237
238 // Forcibly reset the stack, losing all of its contents.
239 void reset() {
240 _index = 0;
241 }
242
243 // Expand the stack, typically in response to an overflow condition.
244 void expand();
245
246 // Compute the least valued stack element.
247 oop least_value(HeapWord* low) {
248 oop least = (oop)low;
249 for (size_t i = 0; i < _index; i++) {
250 least = MIN2(least, _base[i]);
251 }
252 return least;
253 }
254
255 // Exposed here to allow stack expansion in || case.
256 Mutex* par_lock() { return &_par_lock; }
257 };
258
259 class CardTableRS;
260 class CMSParGCThreadState;
261
262 class ModUnionClosure: public MemRegionClosure {
263 protected:
264 CMSBitMap* _t;
265 public:
266 ModUnionClosure(CMSBitMap* t): _t(t) { }
267 void do_MemRegion(MemRegion mr);
268 };
269
270 class ModUnionClosurePar: public ModUnionClosure {
271 public:
272 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
273 void do_MemRegion(MemRegion mr);
274 };
275
276 // Survivor Chunk Array in support of parallelization of
277 // Survivor Space rescan.
278 class ChunkArray: public CHeapObj<mtGC> {
279 size_t _index;
280 size_t _capacity;
281 size_t _overflows;
282 HeapWord** _array; // storage for array
283
284 public:
285 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
286 ChunkArray(HeapWord** a, size_t c):
287 _index(0), _capacity(c), _overflows(0), _array(a) {}
288
289 HeapWord** array() { return _array; }
290 void set_array(HeapWord** a) { _array = a; }
291
292 size_t capacity() { return _capacity; }
293 void set_capacity(size_t c) { _capacity = c; }
294
295 size_t end() {
296 assert(_index <= capacity(),
297 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
298 _index, _capacity));
299 return _index;
300 } // exclusive
301
302 HeapWord* nth(size_t n) {
303 assert(n < end(), "Out of bounds access");
304 return _array[n];
305 }
306
307 void reset() {
308 _index = 0;
309 if (_overflows > 0 && PrintCMSStatistics > 1) {
310 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
311 _capacity, _overflows);
312 }
313 _overflows = 0;
314 }
315
316 void record_sample(HeapWord* p, size_t sz) {
317 // For now we do not do anything with the size
318 if (_index < _capacity) {
319 _array[_index++] = p;
320 } else {
321 ++_overflows;
322 assert(_index == _capacity,
323 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
324 "): out of bounds at overflow#" SIZE_FORMAT,
325 _index, _capacity, _overflows));
326 }
327 }
328 };
329
330 //
331 // Timing, allocation and promotion statistics for gc scheduling and incremental
332 // mode pacing. Most statistics are exponential averages.
333 //
334 class CMSStats VALUE_OBJ_CLASS_SPEC {
335 private:
336 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
337
338 // The following are exponential averages with factor alpha:
339 // avg = (100 - alpha) * avg + alpha * cur_sample
340 //
341 // The durations measure: end_time[n] - start_time[n]
342 // The periods measure: start_time[n] - start_time[n-1]
343 //
344 // The cms period and duration include only concurrent collections; time spent
345 // in foreground cms collections due to System.gc() or because of a failure to
346 // keep up are not included.
347 //
348 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
349 // real value, but is used only after the first period. A value of 100 is
350 // used for the first sample so it gets the entire weight.
351 unsigned int _saved_alpha; // 0-100
352 unsigned int _gc0_alpha;
353 unsigned int _cms_alpha;
354
355 double _gc0_duration;
356 double _gc0_period;
357 size_t _gc0_promoted; // bytes promoted per gc0
358 double _cms_duration;
359 double _cms_duration_pre_sweep; // time from initiation to start of sweep
360 double _cms_period;
361 size_t _cms_allocated; // bytes of direct allocation per gc0 period
362
363 // Timers.
364 elapsedTimer _cms_timer;
365 TimeStamp _gc0_begin_time;
366 TimeStamp _cms_begin_time;
367 TimeStamp _cms_end_time;
368
369 // Snapshots of the amount used in the CMS generation.
370 size_t _cms_used_at_gc0_begin;
371 size_t _cms_used_at_gc0_end;
372 size_t _cms_used_at_cms_begin;
373
374 // Used to prevent the duty cycle from being reduced in the middle of a cms
375 // cycle.
376 bool _allow_duty_cycle_reduction;
377
378 enum {
379 _GC0_VALID = 0x1,
380 _CMS_VALID = 0x2,
381 _ALL_VALID = _GC0_VALID | _CMS_VALID
382 };
383
384 unsigned int _valid_bits;
385
386 protected:
387 // In support of adjusting of cms trigger ratios based on history
388 // of concurrent mode failure.
389 double cms_free_adjustment_factor(size_t free) const;
390 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
391
392 public:
393 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
394 unsigned int alpha = CMSExpAvgFactor);
395
396 // Whether or not the statistics contain valid data; higher level statistics
397 // cannot be called until this returns true (they require at least one young
398 // gen and one cms cycle to have completed).
399 bool valid() const;
400
401 // Record statistics.
402 void record_gc0_begin();
403 void record_gc0_end(size_t cms_gen_bytes_used);
404 void record_cms_begin();
405 void record_cms_end();
406
407 // Allow management of the cms timer, which must be stopped/started around
408 // yield points.
409 elapsedTimer& cms_timer() { return _cms_timer; }
410 void start_cms_timer() { _cms_timer.start(); }
411 void stop_cms_timer() { _cms_timer.stop(); }
412
413 // Basic statistics; units are seconds or bytes.
414 double gc0_period() const { return _gc0_period; }
415 double gc0_duration() const { return _gc0_duration; }
416 size_t gc0_promoted() const { return _gc0_promoted; }
417 double cms_period() const { return _cms_period; }
418 double cms_duration() const { return _cms_duration; }
419 size_t cms_allocated() const { return _cms_allocated; }
420
421 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
422
423 // Seconds since the last background cms cycle began or ended.
424 double cms_time_since_begin() const;
425 double cms_time_since_end() const;
426
427 // Higher level statistics--caller must check that valid() returns true before
428 // calling.
429
430 // Returns bytes promoted per second of wall clock time.
431 double promotion_rate() const;
432
433 // Returns bytes directly allocated per second of wall clock time.
434 double cms_allocation_rate() const;
435
436 // Rate at which space in the cms generation is being consumed (sum of the
437 // above two).
438 double cms_consumption_rate() const;
439
440 // Returns an estimate of the number of seconds until the cms generation will
441 // fill up, assuming no collection work is done.
442 double time_until_cms_gen_full() const;
443
444 // Returns an estimate of the number of seconds remaining until
445 // the cms generation collection should start.
446 double time_until_cms_start() const;
447
448 // End of higher level statistics.
449
450 // Debugging.
451 void print_on(outputStream* st) const PRODUCT_RETURN;
452 void print() const { print_on(gclog_or_tty); }
453 };
454
455 // A closure related to weak references processing which
456 // we embed in the CMSCollector, since we need to pass
457 // it to the reference processor for secondary filtering
458 // of references based on reachability of referent;
459 // see role of _is_alive_non_header closure in the
460 // ReferenceProcessor class.
461 // For objects in the CMS generation, this closure checks
462 // if the object is "live" (reachable). Used in weak
463 // reference processing.
464 class CMSIsAliveClosure: public BoolObjectClosure {
465 const MemRegion _span;
466 const CMSBitMap* _bit_map;
467
468 friend class CMSCollector;
469 public:
470 CMSIsAliveClosure(MemRegion span,
471 CMSBitMap* bit_map):
472 _span(span),
473 _bit_map(bit_map) {
474 assert(!span.is_empty(), "Empty span could spell trouble");
475 }
476
477 bool do_object_b(oop obj);
478 };
479
480
481 // Implements AbstractRefProcTaskExecutor for CMS.
482 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
483 public:
484
485 CMSRefProcTaskExecutor(CMSCollector& collector)
486 : _collector(collector)
487 { }
488
489 // Executes a task using worker threads.
490 virtual void execute(ProcessTask& task);
491 virtual void execute(EnqueueTask& task);
492 private:
493 CMSCollector& _collector;
494 };
495
496
497 class CMSCollector: public CHeapObj<mtGC> {
498 friend class VMStructs;
499 friend class ConcurrentMarkSweepThread;
500 friend class ConcurrentMarkSweepGeneration;
501 friend class CompactibleFreeListSpace;
502 friend class CMSParMarkTask;
503 friend class CMSParInitialMarkTask;
504 friend class CMSParRemarkTask;
505 friend class CMSConcMarkingTask;
506 friend class CMSRefProcTaskProxy;
507 friend class CMSRefProcTaskExecutor;
508 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
509 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
510 friend class PushOrMarkClosure; // to access _restart_addr
511 friend class Par_PushOrMarkClosure; // to access _restart_addr
512 friend class MarkFromRootsClosure; // -- ditto --
513 // ... and for clearing cards
514 friend class Par_MarkFromRootsClosure; // to access _restart_addr
515 // ... and for clearing cards
516 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
517 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
518 friend class PushAndMarkVerifyClosure; // -- ditto --
519 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
520 friend class PushAndMarkClosure; // -- ditto --
521 friend class Par_PushAndMarkClosure; // -- ditto --
522 friend class CMSKeepAliveClosure; // -- ditto --
523 friend class CMSDrainMarkingStackClosure; // -- ditto --
524 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
525 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
526 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
527 friend class VM_CMS_Operation;
528 friend class VM_CMS_Initial_Mark;
529 friend class VM_CMS_Final_Remark;
530 friend class TraceCMSMemoryManagerStats;
531
532 private:
533 jlong _time_of_last_gc;
534 void update_time_of_last_gc(jlong now) {
535 _time_of_last_gc = now;
536 }
537
538 OopTaskQueueSet* _task_queues;
539
540 // Overflow list of grey objects, threaded through mark-word
541 // Manipulated with CAS in the parallel/multi-threaded case.
542 oop _overflow_list;
543 // The following array-pair keeps track of mark words
544 // displaced for accommodating overflow list above.
545 // This code will likely be revisited under RFE#4922830.
546 Stack<oop, mtGC> _preserved_oop_stack;
547 Stack<markOop, mtGC> _preserved_mark_stack;
548
549 int* _hash_seed;
550
551 // In support of multi-threaded concurrent phases
552 YieldingFlexibleWorkGang* _conc_workers;
553
554 // Performance Counters
555 CollectorCounters* _gc_counters;
556
557 // Initialization Errors
558 bool _completed_initialization;
559
560 // In support of ExplicitGCInvokesConcurrent
561 static bool _full_gc_requested;
562 static GCCause::Cause _full_gc_cause;
563 unsigned int _collection_count_start;
564
565 // Should we unload classes this concurrent cycle?
566 bool _should_unload_classes;
567 unsigned int _concurrent_cycles_since_last_unload;
568 unsigned int concurrent_cycles_since_last_unload() const {
569 return _concurrent_cycles_since_last_unload;
570 }
571 // Did we (allow) unload classes in the previous concurrent cycle?
572 bool unloaded_classes_last_cycle() const {
573 return concurrent_cycles_since_last_unload() == 0;
574 }
575 // Root scanning options for perm gen
576 int _roots_scanning_options;
577 int roots_scanning_options() const { return _roots_scanning_options; }
578 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
579 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
580
581 // Verification support
582 CMSBitMap _verification_mark_bm;
583 void verify_after_remark_work_1();
584 void verify_after_remark_work_2();
585
586 // True if any verification flag is on.
587 bool _verifying;
588 bool verifying() const { return _verifying; }
589 void set_verifying(bool v) { _verifying = v; }
590
591 // Collector policy
592 ConcurrentMarkSweepPolicy* _collector_policy;
593 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
594
595 void set_did_compact(bool v);
596
597 // XXX Move these to CMSStats ??? FIX ME !!!
598 elapsedTimer _inter_sweep_timer; // Time between sweeps
599 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
600 // Padded decaying average estimates of the above
601 AdaptivePaddedAverage _inter_sweep_estimate;
602 AdaptivePaddedAverage _intra_sweep_estimate;
603
604 CMSTracer* _gc_tracer_cm;
605 ConcurrentGCTimer* _gc_timer_cm;
606
607 bool _cms_start_registered;
608
609 GCHeapSummary _last_heap_summary;
610 MetaspaceSummary _last_metaspace_summary;
611
612 void register_gc_start(GCCause::Cause cause);
613 void register_gc_end();
614 void save_heap_summary();
615 void report_heap_summary(GCWhen::Type when);
616
617 protected:
618 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
619 MemRegion _span; // Span covering above two
620 CardTableRS* _ct; // Card table
621
622 // CMS marking support structures
623 CMSBitMap _markBitMap;
624 CMSBitMap _modUnionTable;
625 CMSMarkStack _markStack;
626
627 HeapWord* _restart_addr; // In support of marking stack overflow
628 void lower_restart_addr(HeapWord* low);
629
630 // Counters in support of marking stack / work queue overflow handling:
631 // a non-zero value indicates certain types of overflow events during
632 // the current CMS cycle and could lead to stack resizing efforts at
633 // an opportune future time.
634 size_t _ser_pmc_preclean_ovflw;
635 size_t _ser_pmc_remark_ovflw;
636 size_t _par_pmc_remark_ovflw;
637 size_t _ser_kac_preclean_ovflw;
638 size_t _ser_kac_ovflw;
639 size_t _par_kac_ovflw;
640 NOT_PRODUCT(ssize_t _num_par_pushes;)
641
642 // ("Weak") Reference processing support.
643 ReferenceProcessor* _ref_processor;
644 CMSIsAliveClosure _is_alive_closure;
645 // Keep this textually after _markBitMap and _span; c'tor dependency.
646
647 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
648 ModUnionClosure _modUnionClosure;
649 ModUnionClosurePar _modUnionClosurePar;
650
651 // CMS abstract state machine
652 // initial_state: Idling
653 // next_state(Idling) = {Marking}
654 // next_state(Marking) = {Precleaning, Sweeping}
655 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
656 // next_state(AbortablePreclean) = {FinalMarking}
657 // next_state(FinalMarking) = {Sweeping}
658 // next_state(Sweeping) = {Resizing}
659 // next_state(Resizing) = {Resetting}
660 // next_state(Resetting) = {Idling}
661 // The numeric values below are chosen so that:
662 // . _collectorState <= Idling == post-sweep && pre-mark
663 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
664 // precleaning || abortablePrecleanb
665 public:
666 enum CollectorState {
667 Resizing = 0,
668 Resetting = 1,
669 Idling = 2,
670 InitialMarking = 3,
671 Marking = 4,
672 Precleaning = 5,
673 AbortablePreclean = 6,
674 FinalMarking = 7,
675 Sweeping = 8
676 };
677 protected:
678 static CollectorState _collectorState;
679
680 // State related to prologue/epilogue invocation for my generations
681 bool _between_prologue_and_epilogue;
682
683 // Signaling/State related to coordination between fore- and background GC
684 // Note: When the baton has been passed from background GC to foreground GC,
685 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
686 static bool _foregroundGCIsActive; // true iff foreground collector is active or
687 // wants to go active
688 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
689 // yet passed the baton to the foreground GC
690
691 // Support for CMSScheduleRemark (abortable preclean)
692 bool _abort_preclean;
693 bool _start_sampling;
694
695 int _numYields;
696 size_t _numDirtyCards;
697 size_t _sweep_count;
698
699 // Occupancy used for bootstrapping stats
700 double _bootstrap_occupancy;
701
702 // Timer
703 elapsedTimer _timer;
704
705 // Timing, allocation and promotion statistics, used for scheduling.
706 CMSStats _stats;
707
708 enum CMS_op_type {
709 CMS_op_checkpointRootsInitial,
710 CMS_op_checkpointRootsFinal
711 };
712
713 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
714 bool stop_world_and_do(CMS_op_type op);
715
716 OopTaskQueueSet* task_queues() { return _task_queues; }
717 int* hash_seed(int i) { return &_hash_seed[i]; }
718 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
719
720 // Support for parallelizing Eden rescan in CMS remark phase
721 void sample_eden(); // ... sample Eden space top
722
723 private:
724 // Support for parallelizing young gen rescan in CMS remark phase
725 ParNewGeneration* _young_gen; // the younger gen
726
727 HeapWord** _top_addr; // ... Top of Eden
728 HeapWord** _end_addr; // ... End of Eden
729 Mutex* _eden_chunk_lock;
730 HeapWord** _eden_chunk_array; // ... Eden partitioning array
731 size_t _eden_chunk_index; // ... top (exclusive) of array
732 size_t _eden_chunk_capacity; // ... max entries in array
733
734 // Support for parallelizing survivor space rescan
735 HeapWord** _survivor_chunk_array;
736 size_t _survivor_chunk_index;
737 size_t _survivor_chunk_capacity;
738 size_t* _cursor;
739 ChunkArray* _survivor_plab_array;
740
741 // Support for marking stack overflow handling
742 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
743 bool par_take_from_overflow_list(size_t num,
744 OopTaskQueue* to_work_q,
745 int no_of_gc_threads);
746 void push_on_overflow_list(oop p);
747 void par_push_on_overflow_list(oop p);
748 // The following is, obviously, not, in general, "MT-stable"
749 bool overflow_list_is_empty() const;
750
751 void preserve_mark_if_necessary(oop p);
752 void par_preserve_mark_if_necessary(oop p);
753 void preserve_mark_work(oop p, markOop m);
754 void restore_preserved_marks_if_any();
755 NOT_PRODUCT(bool no_preserved_marks() const;)
756 // In support of testing overflow code
757 NOT_PRODUCT(int _overflow_counter;)
758 NOT_PRODUCT(bool simulate_overflow();) // Sequential
759 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
760
761 // CMS work methods
762 void checkpointRootsInitialWork(); // Initial checkpoint work
763
764 // A return value of false indicates failure due to stack overflow
765 bool markFromRootsWork(); // Concurrent marking work
766
767 public: // FIX ME!!! only for testing
768 bool do_marking_st(); // Single-threaded marking
769 bool do_marking_mt(); // Multi-threaded marking
770
771 private:
772
773 // Concurrent precleaning work
774 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
775 ScanMarkedObjectsAgainCarefullyClosure* cl);
776 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
777 ScanMarkedObjectsAgainCarefullyClosure* cl);
778 // Does precleaning work, returning a quantity indicative of
779 // the amount of "useful work" done.
780 size_t preclean_work(bool clean_refs, bool clean_survivors);
781 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
782 void abortable_preclean(); // Preclean while looking for possible abort
783 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
784 // Helper function for above; merge-sorts the per-thread plab samples
785 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
786 // Resets (i.e. clears) the per-thread plab sample vectors
787 void reset_survivor_plab_arrays();
788
789 // Final (second) checkpoint work
790 void checkpointRootsFinalWork();
791 // Work routine for parallel version of remark
792 void do_remark_parallel();
793 // Work routine for non-parallel version of remark
794 void do_remark_non_parallel();
795 // Reference processing work routine (during second checkpoint)
796 void refProcessingWork();
797
798 // Concurrent sweeping work
799 void sweepWork(ConcurrentMarkSweepGeneration* gen);
800
801 // (Concurrent) resetting of support data structures
802 void reset(bool concurrent);
803
804 // Clear _expansion_cause fields of constituent generations
805 void clear_expansion_cause();
806
807 // An auxiliary method used to record the ends of
808 // used regions of each generation to limit the extent of sweep
809 void save_sweep_limits();
810
811 // A work method used by the foreground collector to do
812 // a mark-sweep-compact.
813 void do_compaction_work(bool clear_all_soft_refs);
814
815 // Work methods for reporting concurrent mode interruption or failure
816 bool is_external_interruption();
817 void report_concurrent_mode_interruption();
818
819 // If the background GC is active, acquire control from the background
820 // GC and do the collection.
821 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
822
823 // For synchronizing passing of control from background to foreground
824 // GC. waitForForegroundGC() is called by the background
825 // collector. It if had to wait for a foreground collection,
826 // it returns true and the background collection should assume
827 // that the collection was finished by the foreground
828 // collector.
829 bool waitForForegroundGC();
830
831 size_t block_size_using_printezis_bits(HeapWord* addr) const;
832 size_t block_size_if_printezis_bits(HeapWord* addr) const;
833 HeapWord* next_card_start_after_block(HeapWord* addr) const;
834
835 void setup_cms_unloading_and_verification_state();
836 public:
837 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
838 CardTableRS* ct,
839 ConcurrentMarkSweepPolicy* cp);
840 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
841
842 ReferenceProcessor* ref_processor() { return _ref_processor; }
843 void ref_processor_init();
844
845 Mutex* bitMapLock() const { return _markBitMap.lock(); }
846 static CollectorState abstract_state() { return _collectorState; }
847
848 bool should_abort_preclean() const; // Whether preclean should be aborted.
849 size_t get_eden_used() const;
850 size_t get_eden_capacity() const;
851
852 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
853
854 // Locking checks
855 NOT_PRODUCT(static bool have_cms_token();)
856
857 bool shouldConcurrentCollect();
858
859 void collect(bool full,
860 bool clear_all_soft_refs,
861 size_t size,
862 bool tlab);
863 void collect_in_background(GCCause::Cause cause);
864
865 // In support of ExplicitGCInvokesConcurrent
866 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
867 // Should we unload classes in a particular concurrent cycle?
868 bool should_unload_classes() const {
869 return _should_unload_classes;
870 }
871 void update_should_unload_classes();
872
873 void direct_allocated(HeapWord* start, size_t size);
874
875 // Object is dead if not marked and current phase is sweeping.
876 bool is_dead_obj(oop obj) const;
877
878 // After a promotion (of "start"), do any necessary marking.
879 // If "par", then it's being done by a parallel GC thread.
880 // The last two args indicate if we need precise marking
881 // and if so the size of the object so it can be dirtied
882 // in its entirety.
883 void promoted(bool par, HeapWord* start,
884 bool is_obj_array, size_t obj_size);
885
886 void getFreelistLocks() const;
887 void releaseFreelistLocks() const;
888 bool haveFreelistLocks() const;
889
890 // Adjust size of underlying generation
891 void compute_new_size();
892
893 // GC prologue and epilogue
894 void gc_prologue(bool full);
895 void gc_epilogue(bool full);
896
897 jlong time_of_last_gc(jlong now) {
898 if (_collectorState <= Idling) {
899 // gc not in progress
900 return _time_of_last_gc;
901 } else {
902 // collection in progress
903 return now;
904 }
905 }
906
907 // Support for parallel remark of survivor space
908 void* get_data_recorder(int thr_num);
909 void sample_eden_chunk();
910
911 CMSBitMap* markBitMap() { return &_markBitMap; }
912 void directAllocated(HeapWord* start, size_t size);
913
914 // Main CMS steps and related support
915 void checkpointRootsInitial();
916 bool markFromRoots(); // a return value of false indicates failure
917 // due to stack overflow
918 void preclean();
919 void checkpointRootsFinal();
920 void sweep();
921
922 // Check that the currently executing thread is the expected
923 // one (foreground collector or background collector).
924 static void check_correct_thread_executing() PRODUCT_RETURN;
925
926 bool is_cms_reachable(HeapWord* addr);
927
928 // Performance Counter Support
929 CollectorCounters* counters() { return _gc_counters; }
930
931 // Timer stuff
932 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
933 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
934 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
935 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
936
937 int yields() { return _numYields; }
938 void resetYields() { _numYields = 0; }
939 void incrementYields() { _numYields++; }
940 void resetNumDirtyCards() { _numDirtyCards = 0; }
941 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
942 size_t numDirtyCards() { return _numDirtyCards; }
943
944 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
945 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
946 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
947 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
948 size_t sweep_count() const { return _sweep_count; }
949 void increment_sweep_count() { _sweep_count++; }
950
951 // Timers/stats for gc scheduling and incremental mode pacing.
952 CMSStats& stats() { return _stats; }
953
954 // Adaptive size policy
955 AdaptiveSizePolicy* size_policy();
956
957 static void print_on_error(outputStream* st);
958
959 // Debugging
960 void verify();
961 bool verify_after_remark(bool silent = VerifySilently);
962 void verify_ok_to_terminate() const PRODUCT_RETURN;
963 void verify_work_stacks_empty() const PRODUCT_RETURN;
964 void verify_overflow_empty() const PRODUCT_RETURN;
965
966 // Convenience methods in support of debugging
967 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
968 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
969
970 // Accessors
971 CMSMarkStack* verification_mark_stack() { return &_markStack; }
972 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
973
974 // Initialization errors
975 bool completed_initialization() { return _completed_initialization; }
976
977 void print_eden_and_survivor_chunk_arrays();
978 };
979
980 class CMSExpansionCause : public AllStatic {
981 public:
982 enum Cause {
983 _no_expansion,
984 _satisfy_free_ratio,
985 _satisfy_promotion,
986 _satisfy_allocation,
987 _allocate_par_lab,
988 _allocate_par_spooling_space,
989 _adaptive_size_policy
990 };
991 // Return a string describing the cause of the expansion.
992 static const char* to_string(CMSExpansionCause::Cause cause);
993 };
994
995 class ConcurrentMarkSweepGeneration: public CardGeneration {
996 friend class VMStructs;
997 friend class ConcurrentMarkSweepThread;
998 friend class ConcurrentMarkSweep;
999 friend class CMSCollector;
1000 protected:
1001 static CMSCollector* _collector; // the collector that collects us
1002 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1003
1004 // Performance Counters
1005 GenerationCounters* _gen_counters;
1006 GSpaceCounters* _space_counters;
1007
1008 // Words directly allocated, used by CMSStats.
1009 size_t _direct_allocated_words;
1010
1011 // Non-product stat counters
1012 NOT_PRODUCT(
1013 size_t _numObjectsPromoted;
1014 size_t _numWordsPromoted;
1015 size_t _numObjectsAllocated;
1016 size_t _numWordsAllocated;
1017 )
1018
1019 // Used for sizing decisions
1020 bool _incremental_collection_failed;
1021 bool incremental_collection_failed() {
1022 return _incremental_collection_failed;
1023 }
1024 void set_incremental_collection_failed() {
1025 _incremental_collection_failed = true;
1026 }
1027 void clear_incremental_collection_failed() {
1028 _incremental_collection_failed = false;
1029 }
1030
1031 // accessors
1032 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1033 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1034
1035 // Accessing spaces
1036 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; }
1037
1038 private:
1039 // For parallel young-gen GC support.
1040 CMSParGCThreadState** _par_gc_thread_states;
1041
1042 // Reason generation was expanded
1043 CMSExpansionCause::Cause _expansion_cause;
1044
1045 // In support of MinChunkSize being larger than min object size
1046 const double _dilatation_factor;
1047
1048 // True if a compacting collection was done.
1049 bool _did_compact;
1050 bool did_compact() { return _did_compact; }
1051
1052 // Fraction of current occupancy at which to start a CMS collection which
1053 // will collect this generation (at least).
1054 double _initiating_occupancy;
1055
1056 protected:
1057 // Shrink generation by specified size (returns false if unable to shrink)
1058 void shrink_free_list_by(size_t bytes);
1059
1060 // Update statistics for GC
1061 virtual void update_gc_stats(int level, bool full);
1062
1063 // Maximum available space in the generation (including uncommitted)
1064 // space.
1065 size_t max_available() const;
1066
1067 // getter and initializer for _initiating_occupancy field.
1068 double initiating_occupancy() const { return _initiating_occupancy; }
1069 void init_initiating_occupancy(intx io, uintx tr);
1070
1071 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause);
1072
1073 void assert_correct_size_change_locking();
1074
1075 public:
1076 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1077 int level, CardTableRS* ct,
1078 bool use_adaptive_freelists,
1079 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1080
1081 // Accessors
1082 CMSCollector* collector() const { return _collector; }
1083 static void set_collector(CMSCollector* collector) {
1084 assert(_collector == NULL, "already set");
1085 _collector = collector;
1086 }
1087 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1088
1089 Mutex* freelistLock() const;
1090
1091 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1092
1093 void set_did_compact(bool v) { _did_compact = v; }
1094
1095 bool refs_discovery_is_atomic() const { return false; }
1096 bool refs_discovery_is_mt() const {
1097 // Note: CMS does MT-discovery during the parallel-remark
1098 // phases. Use ReferenceProcessorMTMutator to make refs
1099 // discovery MT-safe during such phases or other parallel
1100 // discovery phases in the future. This may all go away
1101 // if/when we decide that refs discovery is sufficiently
1102 // rare that the cost of the CAS's involved is in the
1103 // noise. That's a measurement that should be done, and
1104 // the code simplified if that turns out to be the case.
1105 return ConcGCThreads > 1;
1106 }
1107
1108 // Override
1109 virtual void ref_processor_init();
1110
1111 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1112
1113 // Space enquiries
1114 double occupancy() const { return ((double)used())/((double)capacity()); }
1115 size_t contiguous_available() const;
1116 size_t unsafe_max_alloc_nogc() const;
1117
1118 // over-rides
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 // Adjust quantities in the generation affected by
1130 // the compaction.
1131 void reset_after_compaction();
1132
1133 // Allocation support
1134 HeapWord* allocate(size_t size, bool tlab);
1135 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1136 oop promote(oop obj, size_t obj_size);
1137 HeapWord* par_allocate(size_t size, bool tlab) {
1138 return allocate(size, tlab);
1139 }
1140
1141
1142 // Used by CMSStats to track direct allocation. The value is sampled and
1143 // reset after each young gen collection.
1144 size_t direct_allocated_words() const { return _direct_allocated_words; }
1145 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1146
1147 // Overrides for parallel promotion.
1148 virtual oop par_promote(int thread_num,
1149 oop obj, markOop m, size_t word_sz);
1150 virtual void par_promote_alloc_done(int thread_num);
1151 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1152
1153 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1154
1155 // Inform this (non-young) generation that a promotion failure was
1156 // encountered during a collection of a younger generation that
1157 // promotes into this generation.
1158 virtual void promotion_failure_occurred();
1159
1160 bool should_collect(bool full, size_t size, bool tlab);
1161 virtual bool should_concurrent_collect() const;
1162 virtual bool is_too_full() const;
1163 void collect(bool full,
1164 bool clear_all_soft_refs,
1165 size_t size,
1166 bool tlab);
1167
1168 HeapWord* expand_and_allocate(size_t word_size,
1169 bool tlab,
1170 bool parallel = false);
1171
1172 // GC prologue and epilogue
1173 void gc_prologue(bool full);
1174 void gc_prologue_work(bool full, bool registerClosure,
1175 ModUnionClosure* modUnionClosure);
1176 void gc_epilogue(bool full);
1177 void gc_epilogue_work(bool full);
1178
1179 // Time since last GC of this generation
1180 jlong time_of_last_gc(jlong now) {
1181 return collector()->time_of_last_gc(now);
1182 }
1183 void update_time_of_last_gc(jlong now) {
1184 collector()-> update_time_of_last_gc(now);
1185 }
1186
1187 // Allocation failure
1188 void shrink(size_t bytes);
1189 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1190 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1191
1192 // Iteration support and related enquiries
1193 void save_marks();
1194 bool no_allocs_since_save_marks();
1195
1196 // Iteration support specific to CMS generations
1197 void save_sweep_limit();
1198
1199 // More iteration support
1200 virtual void oop_iterate(ExtendedOopClosure* cl);
1201 virtual void safe_object_iterate(ObjectClosure* cl);
1202 virtual void object_iterate(ObjectClosure* cl);
1203
1204 // Need to declare the full complement of closures, whether we'll
1205 // override them or not, or get message from the compiler:
1206 // oop_since_save_marks_iterate_nv hides virtual function...
1207 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1208 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1209 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1210
1211 // Smart allocation XXX -- move to CFLSpace?
1212 void setNearLargestChunk();
1213 bool isNearLargestChunk(HeapWord* addr);
1214
1215 // Get the chunk at the end of the space. Delegates to
1216 // the space.
1217 FreeChunk* find_chunk_at_end();
1218
1219 void post_compact();
1220
1221 // Debugging
1222 void prepare_for_verify();
1223 void verify();
1224 void print_statistics() PRODUCT_RETURN;
1225
1226 // Performance Counters support
1227 virtual void update_counters();
1228 virtual void update_counters(size_t used);
1229 void initialize_performance_counters();
1230 CollectorCounters* counters() { return collector()->counters(); }
1231
1232 // Support for parallel remark of survivor space
1233 void* get_data_recorder(int thr_num) {
1234 //Delegate to collector
1235 return collector()->get_data_recorder(thr_num);
1236 }
1237 void sample_eden_chunk() {
1238 //Delegate to collector
1239 return collector()->sample_eden_chunk();
1240 }
1241
1242 // Printing
1243 const char* name() const;
1244 virtual const char* short_name() const { return "CMS"; }
1245 void print() const;
1246 void printOccupancy(const char* s);
1247
1248 // Resize the generation after a compacting GC. The
1249 // generation can be treated as a contiguous space
1250 // after the compaction.
1251 virtual void compute_new_size();
1252 // Resize the generation after a non-compacting
1253 // collection.
1254 void compute_new_size_free_list();
1255 };
1256
1257 //
1258 // Closures of various sorts used by CMS to accomplish its work
1259 //
1260
1261 // This closure is used to do concurrent marking from the roots
1262 // following the first checkpoint.
1263 class MarkFromRootsClosure: public BitMapClosure {
1264 CMSCollector* _collector;
1265 MemRegion _span;
1266 CMSBitMap* _bitMap;
1267 CMSBitMap* _mut;
1268 CMSMarkStack* _markStack;
1269 bool _yield;
1270 int _skipBits;
1271 HeapWord* _finger;
1272 HeapWord* _threshold;
1273 DEBUG_ONLY(bool _verifying;)
1274
1275 public:
1276 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1277 CMSBitMap* bitMap,
1278 CMSMarkStack* markStack,
1279 bool should_yield, bool verifying = false);
1280 bool do_bit(size_t offset);
1281 void reset(HeapWord* addr);
1282 inline void do_yield_check();
1283
1284 private:
1285 void scanOopsInOop(HeapWord* ptr);
1286 void do_yield_work();
1287 };
1288
1289 // This closure is used to do concurrent multi-threaded
1290 // marking from the roots following the first checkpoint.
1291 // XXX This should really be a subclass of The serial version
1292 // above, but i have not had the time to refactor things cleanly.
1293 class Par_MarkFromRootsClosure: public BitMapClosure {
1294 CMSCollector* _collector;
1295 MemRegion _whole_span;
1296 MemRegion _span;
1297 CMSBitMap* _bit_map;
1298 CMSBitMap* _mut;
1299 OopTaskQueue* _work_queue;
1300 CMSMarkStack* _overflow_stack;
1301 int _skip_bits;
1302 HeapWord* _finger;
1303 HeapWord* _threshold;
1304 CMSConcMarkingTask* _task;
1305 public:
1306 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1307 MemRegion span,
1308 CMSBitMap* bit_map,
1309 OopTaskQueue* work_queue,
1310 CMSMarkStack* overflow_stack);
1311 bool do_bit(size_t offset);
1312 inline void do_yield_check();
1313
1314 private:
1315 void scan_oops_in_oop(HeapWord* ptr);
1316 void do_yield_work();
1317 bool get_work_from_overflow_stack();
1318 };
1319
1320 // The following closures are used to do certain kinds of verification of
1321 // CMS marking.
1322 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1323 CMSCollector* _collector;
1324 MemRegion _span;
1325 CMSBitMap* _verification_bm;
1326 CMSBitMap* _cms_bm;
1327 CMSMarkStack* _mark_stack;
1328 protected:
1329 void do_oop(oop p);
1330 template <class T> inline void do_oop_work(T *p) {
1331 oop obj = oopDesc::load_decode_heap_oop(p);
1332 do_oop(obj);
1333 }
1334 public:
1335 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1336 MemRegion span,
1337 CMSBitMap* verification_bm,
1338 CMSBitMap* cms_bm,
1339 CMSMarkStack* mark_stack);
1340 void do_oop(oop* p);
1341 void do_oop(narrowOop* p);
1342
1343 // Deal with a stack overflow condition
1344 void handle_stack_overflow(HeapWord* lost);
1345 };
1346
1347 class MarkFromRootsVerifyClosure: public BitMapClosure {
1348 CMSCollector* _collector;
1349 MemRegion _span;
1350 CMSBitMap* _verification_bm;
1351 CMSBitMap* _cms_bm;
1352 CMSMarkStack* _mark_stack;
1353 HeapWord* _finger;
1354 PushAndMarkVerifyClosure _pam_verify_closure;
1355 public:
1356 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1357 CMSBitMap* verification_bm,
1358 CMSBitMap* cms_bm,
1359 CMSMarkStack* mark_stack);
1360 bool do_bit(size_t offset);
1361 void reset(HeapWord* addr);
1362 };
1363
1364
1365 // This closure is used to check that a certain set of bits is
1366 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1367 class FalseBitMapClosure: public BitMapClosure {
1368 public:
1369 bool do_bit(size_t offset) {
1370 guarantee(false, "Should not have a 1 bit");
1371 return true;
1372 }
1373 };
1374
1375 // A version of ObjectClosure with "memory" (see _previous_address below)
1376 class UpwardsObjectClosure: public BoolObjectClosure {
1377 HeapWord* _previous_address;
1378 public:
1379 UpwardsObjectClosure() : _previous_address(NULL) { }
1380 void set_previous(HeapWord* addr) { _previous_address = addr; }
1381 HeapWord* previous() { return _previous_address; }
1382 // A return value of "true" can be used by the caller to decide
1383 // if this object's end should *NOT* be recorded in
1384 // _previous_address above.
1385 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1386 };
1387
1388 // This closure is used during the second checkpointing phase
1389 // to rescan the marked objects on the dirty cards in the mod
1390 // union table and the card table proper. It's invoked via
1391 // MarkFromDirtyCardsClosure below. It uses either
1392 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1393 // declared in genOopClosures.hpp to accomplish some of its work.
1394 // In the parallel case the bitMap is shared, so access to
1395 // it needs to be suitably synchronized for updates by embedded
1396 // closures that update it; however, this closure itself only
1397 // reads the bit_map and because it is idempotent, is immune to
1398 // reading stale values.
1399 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1400 #ifdef ASSERT
1401 CMSCollector* _collector;
1402 MemRegion _span;
1403 union {
1404 CMSMarkStack* _mark_stack;
1405 OopTaskQueue* _work_queue;
1406 };
1407 #endif // ASSERT
1408 bool _parallel;
1409 CMSBitMap* _bit_map;
1410 union {
1411 MarkRefsIntoAndScanClosure* _scan_closure;
1412 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1413 };
1414
1415 public:
1416 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1417 MemRegion span,
1418 ReferenceProcessor* rp,
1419 CMSBitMap* bit_map,
1420 CMSMarkStack* mark_stack,
1421 MarkRefsIntoAndScanClosure* cl):
1422 #ifdef ASSERT
1423 _collector(collector),
1424 _span(span),
1425 _mark_stack(mark_stack),
1426 #endif // ASSERT
1427 _parallel(false),
1428 _bit_map(bit_map),
1429 _scan_closure(cl) { }
1430
1431 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1432 MemRegion span,
1433 ReferenceProcessor* rp,
1434 CMSBitMap* bit_map,
1435 OopTaskQueue* work_queue,
1436 Par_MarkRefsIntoAndScanClosure* cl):
1437 #ifdef ASSERT
1438 _collector(collector),
1439 _span(span),
1440 _work_queue(work_queue),
1441 #endif // ASSERT
1442 _parallel(true),
1443 _bit_map(bit_map),
1444 _par_scan_closure(cl) { }
1445
1446 bool do_object_b(oop obj) {
1447 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1448 return false;
1449 }
1450 bool do_object_bm(oop p, MemRegion mr);
1451 };
1452
1453 // This closure is used during the second checkpointing phase
1454 // to rescan the marked objects on the dirty cards in the mod
1455 // union table and the card table proper. It invokes
1456 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1457 // In the parallel case, the bit map is shared and requires
1458 // synchronized access.
1459 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1460 CompactibleFreeListSpace* _space;
1461 ScanMarkedObjectsAgainClosure _scan_cl;
1462 size_t _num_dirty_cards;
1463
1464 public:
1465 MarkFromDirtyCardsClosure(CMSCollector* collector,
1466 MemRegion span,
1467 CompactibleFreeListSpace* space,
1468 CMSBitMap* bit_map,
1469 CMSMarkStack* mark_stack,
1470 MarkRefsIntoAndScanClosure* cl):
1471 _space(space),
1472 _num_dirty_cards(0),
1473 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1474 mark_stack, cl) { }
1475
1476 MarkFromDirtyCardsClosure(CMSCollector* collector,
1477 MemRegion span,
1478 CompactibleFreeListSpace* space,
1479 CMSBitMap* bit_map,
1480 OopTaskQueue* work_queue,
1481 Par_MarkRefsIntoAndScanClosure* cl):
1482 _space(space),
1483 _num_dirty_cards(0),
1484 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1485 work_queue, cl) { }
1486
1487 void do_MemRegion(MemRegion mr);
1488 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1489 size_t num_dirty_cards() { return _num_dirty_cards; }
1490 };
1491
1492 // This closure is used in the non-product build to check
1493 // that there are no MemRegions with a certain property.
1494 class FalseMemRegionClosure: public MemRegionClosure {
1495 void do_MemRegion(MemRegion mr) {
1496 guarantee(!mr.is_empty(), "Shouldn't be empty");
1497 guarantee(false, "Should never be here");
1498 }
1499 };
1500
1501 // This closure is used during the precleaning phase
1502 // to "carefully" rescan marked objects on dirty cards.
1503 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1504 // to accomplish some of its work.
1505 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1506 CMSCollector* _collector;
1507 MemRegion _span;
1508 bool _yield;
1509 Mutex* _freelistLock;
1510 CMSBitMap* _bitMap;
1511 CMSMarkStack* _markStack;
1512 MarkRefsIntoAndScanClosure* _scanningClosure;
1513
1514 public:
1515 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1516 MemRegion span,
1517 CMSBitMap* bitMap,
1518 CMSMarkStack* markStack,
1519 MarkRefsIntoAndScanClosure* cl,
1520 bool should_yield):
1521 _collector(collector),
1522 _span(span),
1523 _yield(should_yield),
1524 _bitMap(bitMap),
1525 _markStack(markStack),
1526 _scanningClosure(cl) {
1527 }
1528
1529 void do_object(oop p) {
1530 guarantee(false, "call do_object_careful instead");
1531 }
1532
1533 size_t do_object_careful(oop p) {
1534 guarantee(false, "Unexpected caller");
1535 return 0;
1536 }
1537
1538 size_t do_object_careful_m(oop p, MemRegion mr);
1539
1540 void setFreelistLock(Mutex* m) {
1541 _freelistLock = m;
1542 _scanningClosure->set_freelistLock(m);
1543 }
1544
1545 private:
1546 inline bool do_yield_check();
1547
1548 void do_yield_work();
1549 };
1550
1551 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1552 CMSCollector* _collector;
1553 MemRegion _span;
1554 bool _yield;
1555 CMSBitMap* _bit_map;
1556 CMSMarkStack* _mark_stack;
1557 PushAndMarkClosure* _scanning_closure;
1558 unsigned int _before_count;
1559
1560 public:
1561 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1562 MemRegion span,
1563 CMSBitMap* bit_map,
1564 CMSMarkStack* mark_stack,
1565 PushAndMarkClosure* cl,
1566 unsigned int before_count,
1567 bool should_yield):
1568 _collector(collector),
1569 _span(span),
1570 _yield(should_yield),
1571 _bit_map(bit_map),
1572 _mark_stack(mark_stack),
1573 _scanning_closure(cl),
1574 _before_count(before_count)
1575 { }
1576
1577 void do_object(oop p) {
1578 guarantee(false, "call do_object_careful instead");
1579 }
1580
1581 size_t do_object_careful(oop p);
1582
1583 size_t do_object_careful_m(oop p, MemRegion mr) {
1584 guarantee(false, "Unexpected caller");
1585 return 0;
1586 }
1587
1588 private:
1589 inline void do_yield_check();
1590 void do_yield_work();
1591 };
1592
1593 // This closure is used to accomplish the sweeping work
1594 // after the second checkpoint but before the concurrent reset
1595 // phase.
1596 //
1597 // Terminology
1598 // left hand chunk (LHC) - block of one or more chunks currently being
1599 // coalesced. The LHC is available for coalescing with a new chunk.
1600 // right hand chunk (RHC) - block that is currently being swept that is
1601 // free or garbage that can be coalesced with the LHC.
1602 // _inFreeRange is true if there is currently a LHC
1603 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1604 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1605 // _freeFinger is the address of the current LHC
1606 class SweepClosure: public BlkClosureCareful {
1607 CMSCollector* _collector; // collector doing the work
1608 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1609 CompactibleFreeListSpace* _sp; // Space being swept
1610 HeapWord* _limit;// the address at or above which the sweep should stop
1611 // because we do not expect newly garbage blocks
1612 // eligible for sweeping past that address.
1613 Mutex* _freelistLock; // Free list lock (in space)
1614 CMSBitMap* _bitMap; // Marking bit map (in
1615 // generation)
1616 bool _inFreeRange; // Indicates if we are in the
1617 // midst of a free run
1618 bool _freeRangeInFreeLists;
1619 // Often, we have just found
1620 // a free chunk and started
1621 // a new free range; we do not
1622 // eagerly remove this chunk from
1623 // the free lists unless there is
1624 // a possibility of coalescing.
1625 // When true, this flag indicates
1626 // that the _freeFinger below
1627 // points to a potentially free chunk
1628 // that may still be in the free lists
1629 bool _lastFreeRangeCoalesced;
1630 // free range contains chunks
1631 // coalesced
1632 bool _yield;
1633 // Whether sweeping should be
1634 // done with yields. For instance
1635 // when done by the foreground
1636 // collector we shouldn't yield.
1637 HeapWord* _freeFinger; // When _inFreeRange is set, the
1638 // pointer to the "left hand
1639 // chunk"
1640 size_t _freeRangeSize;
1641 // When _inFreeRange is set, this
1642 // indicates the accumulated size
1643 // of the "left hand chunk"
1644 NOT_PRODUCT(
1645 size_t _numObjectsFreed;
1646 size_t _numWordsFreed;
1647 size_t _numObjectsLive;
1648 size_t _numWordsLive;
1649 size_t _numObjectsAlreadyFree;
1650 size_t _numWordsAlreadyFree;
1651 FreeChunk* _last_fc;
1652 )
1653 private:
1654 // Code that is common to a free chunk or garbage when
1655 // encountered during sweeping.
1656 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1657 // Process a free chunk during sweeping.
1658 void do_already_free_chunk(FreeChunk *fc);
1659 // Work method called when processing an already free or a
1660 // freshly garbage chunk to do a lookahead and possibly a
1661 // preemptive flush if crossing over _limit.
1662 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1663 // Process a garbage chunk during sweeping.
1664 size_t do_garbage_chunk(FreeChunk *fc);
1665 // Process a live chunk during sweeping.
1666 size_t do_live_chunk(FreeChunk* fc);
1667
1668 // Accessors.
1669 HeapWord* freeFinger() const { return _freeFinger; }
1670 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1671 bool inFreeRange() const { return _inFreeRange; }
1672 void set_inFreeRange(bool v) { _inFreeRange = v; }
1673 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1674 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1675 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1676 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1677
1678 // Initialize a free range.
1679 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1680 // Return this chunk to the free lists.
1681 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1682
1683 // Check if we should yield and do so when necessary.
1684 inline void do_yield_check(HeapWord* addr);
1685
1686 // Yield
1687 void do_yield_work(HeapWord* addr);
1688
1689 // Debugging/Printing
1690 void print_free_block_coalesced(FreeChunk* fc) const;
1691
1692 public:
1693 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1694 CMSBitMap* bitMap, bool should_yield);
1695 ~SweepClosure() PRODUCT_RETURN;
1696
1697 size_t do_blk_careful(HeapWord* addr);
1698 void print() const { print_on(tty); }
1699 void print_on(outputStream *st) const;
1700 };
1701
1702 // Closures related to weak references processing
1703
1704 // During CMS' weak reference processing, this is a
1705 // work-routine/closure used to complete transitive
1706 // marking of objects as live after a certain point
1707 // in which an initial set has been completely accumulated.
1708 // This closure is currently used both during the final
1709 // remark stop-world phase, as well as during the concurrent
1710 // precleaning of the discovered reference lists.
1711 class CMSDrainMarkingStackClosure: public VoidClosure {
1712 CMSCollector* _collector;
1713 MemRegion _span;
1714 CMSMarkStack* _mark_stack;
1715 CMSBitMap* _bit_map;
1716 CMSKeepAliveClosure* _keep_alive;
1717 bool _concurrent_precleaning;
1718 public:
1719 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1720 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1721 CMSKeepAliveClosure* keep_alive,
1722 bool cpc):
1723 _collector(collector),
1724 _span(span),
1725 _bit_map(bit_map),
1726 _mark_stack(mark_stack),
1727 _keep_alive(keep_alive),
1728 _concurrent_precleaning(cpc) {
1729 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1730 "Mismatch");
1731 }
1732
1733 void do_void();
1734 };
1735
1736 // A parallel version of CMSDrainMarkingStackClosure above.
1737 class CMSParDrainMarkingStackClosure: public VoidClosure {
1738 CMSCollector* _collector;
1739 MemRegion _span;
1740 OopTaskQueue* _work_queue;
1741 CMSBitMap* _bit_map;
1742 CMSInnerParMarkAndPushClosure _mark_and_push;
1743
1744 public:
1745 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1746 MemRegion span, CMSBitMap* bit_map,
1747 OopTaskQueue* work_queue):
1748 _collector(collector),
1749 _span(span),
1750 _bit_map(bit_map),
1751 _work_queue(work_queue),
1752 _mark_and_push(collector, span, bit_map, work_queue) { }
1753
1754 public:
1755 void trim_queue(uint max);
1756 void do_void();
1757 };
1758
1759 // Allow yielding or short-circuiting of reference list
1760 // precleaning work.
1761 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1762 CMSCollector* _collector;
1763 void do_yield_work();
1764 public:
1765 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1766 _collector(collector) {}
1767 virtual bool should_return();
1768 };
1769
1770
1771 // Convenience class that locks free list locks for given CMS collector
1772 class FreelistLocker: public StackObj {
1773 private:
1774 CMSCollector* _collector;
1775 public:
1776 FreelistLocker(CMSCollector* collector):
1777 _collector(collector) {
1778 _collector->getFreelistLocks();
1779 }
1780
1781 ~FreelistLocker() {
1782 _collector->releaseFreelistLocks();
1783 }
1784 };
1785
1786 // Mark all dead objects in a given space.
1787 class MarkDeadObjectsClosure: public BlkClosure {
1788 const CMSCollector* _collector;
1789 const CompactibleFreeListSpace* _sp;
1790 CMSBitMap* _live_bit_map;
1791 CMSBitMap* _dead_bit_map;
1792 public:
1793 MarkDeadObjectsClosure(const CMSCollector* collector,
1794 const CompactibleFreeListSpace* sp,
1795 CMSBitMap *live_bit_map,
1796 CMSBitMap *dead_bit_map) :
1797 _collector(collector),
1798 _sp(sp),
1799 _live_bit_map(live_bit_map),
1800 _dead_bit_map(dead_bit_map) {}
1801 size_t do_blk(HeapWord* addr);
1802 };
1803
1804 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1805
1806 public:
1807 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1808 };
1809
1810
1811 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP