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_foreground_gc_start(GCCause::Cause cause);
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 // Number of full gc's since the last concurrent gc.
699 uint _full_gcs_since_conc_gc;
700
701 // Occupancy used for bootstrapping stats
702 double _bootstrap_occupancy;
703
704 // Timer
705 elapsedTimer _timer;
706
707 // Timing, allocation and promotion statistics, used for scheduling.
708 CMSStats _stats;
709
710 enum CMS_op_type {
711 CMS_op_checkpointRootsInitial,
712 CMS_op_checkpointRootsFinal
713 };
714
715 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
716 bool stop_world_and_do(CMS_op_type op);
717
718 OopTaskQueueSet* task_queues() { return _task_queues; }
719 int* hash_seed(int i) { return &_hash_seed[i]; }
720 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
721
722 // Support for parallelizing Eden rescan in CMS remark phase
723 void sample_eden(); // ... sample Eden space top
724
725 private:
726 // Support for parallelizing young gen rescan in CMS remark phase
727 Generation* _young_gen; // the younger gen
728 HeapWord** _top_addr; // ... Top of Eden
729 HeapWord** _end_addr; // ... End of Eden
730 Mutex* _eden_chunk_lock;
731 HeapWord** _eden_chunk_array; // ... Eden partitioning array
732 size_t _eden_chunk_index; // ... top (exclusive) of array
733 size_t _eden_chunk_capacity; // ... max entries in array
734
735 // Support for parallelizing survivor space rescan
736 HeapWord** _survivor_chunk_array;
737 size_t _survivor_chunk_index;
738 size_t _survivor_chunk_capacity;
739 size_t* _cursor;
740 ChunkArray* _survivor_plab_array;
741
742 // Support for marking stack overflow handling
743 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
744 bool par_take_from_overflow_list(size_t num,
745 OopTaskQueue* to_work_q,
746 int no_of_gc_threads);
747 void push_on_overflow_list(oop p);
748 void par_push_on_overflow_list(oop p);
749 // The following is, obviously, not, in general, "MT-stable"
750 bool overflow_list_is_empty() const;
751
752 void preserve_mark_if_necessary(oop p);
753 void par_preserve_mark_if_necessary(oop p);
754 void preserve_mark_work(oop p, markOop m);
755 void restore_preserved_marks_if_any();
756 NOT_PRODUCT(bool no_preserved_marks() const;)
757 // In support of testing overflow code
758 NOT_PRODUCT(int _overflow_counter;)
759 NOT_PRODUCT(bool simulate_overflow();) // Sequential
760 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
761
762 // CMS work methods
763 void checkpointRootsInitialWork(bool asynch); // Initial checkpoint work
764
765 // A return value of false indicates failure due to stack overflow
766 bool markFromRootsWork(bool asynch); // Concurrent marking work
767
768 public: // FIX ME!!! only for testing
769 bool do_marking_st(bool asynch); // Single-threaded marking
770 bool do_marking_mt(bool asynch); // Multi-threaded marking
771
772 private:
773
774 // Concurrent precleaning work
775 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
776 ScanMarkedObjectsAgainCarefullyClosure* cl);
777 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
778 ScanMarkedObjectsAgainCarefullyClosure* cl);
779 // Does precleaning work, returning a quantity indicative of
780 // the amount of "useful work" done.
781 size_t preclean_work(bool clean_refs, bool clean_survivors);
782 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
783 void abortable_preclean(); // Preclean while looking for possible abort
784 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
785 // Helper function for above; merge-sorts the per-thread plab samples
786 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
787 // Resets (i.e. clears) the per-thread plab sample vectors
788 void reset_survivor_plab_arrays();
789
790 // Final (second) checkpoint work
791 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
792 bool init_mark_was_synchronous);
793 // Work routine for parallel version of remark
794 void do_remark_parallel();
795 // Work routine for non-parallel version of remark
796 void do_remark_non_parallel();
797 // Reference processing work routine (during second checkpoint)
798 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
799
800 // Concurrent sweeping work
801 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
802
803 // (Concurrent) resetting of support data structures
804 void reset(bool asynch);
805
806 // Clear _expansion_cause fields of constituent generations
807 void clear_expansion_cause();
808
809 // An auxiliary method used to record the ends of
810 // used regions of each generation to limit the extent of sweep
811 void save_sweep_limits();
812
813 // A work method used by foreground collection to determine
814 // what type of collection (compacting or not, continuing or fresh)
815 // it should do.
816 void decide_foreground_collection_type(bool clear_all_soft_refs,
817 bool* should_compact, bool* should_start_over);
818
819 // A work method used by the foreground collector to do
820 // a mark-sweep-compact.
821 void do_compaction_work(bool clear_all_soft_refs);
822
823 // A work method used by the foreground collector to do
824 // a mark-sweep, after taking over from a possibly on-going
825 // concurrent mark-sweep collection.
826 void do_mark_sweep_work(bool clear_all_soft_refs,
827 CollectorState first_state, bool should_start_over);
828
829 // Work methods for reporting concurrent mode interruption or failure
830 bool is_external_interruption();
831 void report_concurrent_mode_interruption();
832
833 // If the background GC is active, acquire control from the background
834 // GC and do the collection.
835 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
836
837 // For synchronizing passing of control from background to foreground
838 // GC. waitForForegroundGC() is called by the background
839 // collector. It if had to wait for a foreground collection,
840 // it returns true and the background collection should assume
841 // that the collection was finished by the foreground
842 // collector.
843 bool waitForForegroundGC();
844
845 size_t block_size_using_printezis_bits(HeapWord* addr) const;
846 size_t block_size_if_printezis_bits(HeapWord* addr) const;
847 HeapWord* next_card_start_after_block(HeapWord* addr) const;
848
849 void setup_cms_unloading_and_verification_state();
850 public:
851 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
852 CardTableRS* ct,
853 ConcurrentMarkSweepPolicy* cp);
854 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
855
856 ReferenceProcessor* ref_processor() { return _ref_processor; }
857 void ref_processor_init();
858
859 Mutex* bitMapLock() const { return _markBitMap.lock(); }
860 static CollectorState abstract_state() { return _collectorState; }
861
862 bool should_abort_preclean() const; // Whether preclean should be aborted.
863 size_t get_eden_used() const;
864 size_t get_eden_capacity() const;
865
866 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
867
868 // Locking checks
869 NOT_PRODUCT(static bool have_cms_token();)
870
871 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
872 bool shouldConcurrentCollect();
873
874 void collect(bool full,
875 bool clear_all_soft_refs,
876 size_t size,
877 bool tlab);
878 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
879 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
880
881 // In support of ExplicitGCInvokesConcurrent
882 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
883 // Should we unload classes in a particular concurrent cycle?
884 bool should_unload_classes() const {
885 return _should_unload_classes;
886 }
887 void update_should_unload_classes();
888
889 void direct_allocated(HeapWord* start, size_t size);
890
891 // Object is dead if not marked and current phase is sweeping.
892 bool is_dead_obj(oop obj) const;
893
894 // After a promotion (of "start"), do any necessary marking.
895 // If "par", then it's being done by a parallel GC thread.
896 // The last two args indicate if we need precise marking
897 // and if so the size of the object so it can be dirtied
898 // in its entirety.
899 void promoted(bool par, HeapWord* start,
900 bool is_obj_array, size_t obj_size);
901
902 void getFreelistLocks() const;
903 void releaseFreelistLocks() const;
904 bool haveFreelistLocks() const;
905
906 // Adjust size of underlying generation
907 void compute_new_size();
908
909 // GC prologue and epilogue
910 void gc_prologue(bool full);
911 void gc_epilogue(bool full);
912
913 jlong time_of_last_gc(jlong now) {
914 if (_collectorState <= Idling) {
915 // gc not in progress
916 return _time_of_last_gc;
917 } else {
918 // collection in progress
919 return now;
920 }
921 }
922
923 // Support for parallel remark of survivor space
924 void* get_data_recorder(int thr_num);
925 void sample_eden_chunk();
926
927 CMSBitMap* markBitMap() { return &_markBitMap; }
928 void directAllocated(HeapWord* start, size_t size);
929
930 // Main CMS steps and related support
931 void checkpointRootsInitial(bool asynch);
932 bool markFromRoots(bool asynch); // a return value of false indicates failure
933 // due to stack overflow
934 void preclean();
935 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
936 bool init_mark_was_synchronous);
937 void sweep(bool asynch);
938
939 // Check that the currently executing thread is the expected
940 // one (foreground collector or background collector).
941 static void check_correct_thread_executing() PRODUCT_RETURN;
942 // XXXPERM void print_statistics() PRODUCT_RETURN;
943
944 bool is_cms_reachable(HeapWord* addr);
945
946 // Performance Counter Support
947 CollectorCounters* counters() { return _gc_counters; }
948
949 // Timer stuff
950 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
951 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
952 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
953 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
954
955 int yields() { return _numYields; }
956 void resetYields() { _numYields = 0; }
957 void incrementYields() { _numYields++; }
958 void resetNumDirtyCards() { _numDirtyCards = 0; }
959 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
960 size_t numDirtyCards() { return _numDirtyCards; }
961
962 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
963 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
964 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
965 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
966 size_t sweep_count() const { return _sweep_count; }
967 void increment_sweep_count() { _sweep_count++; }
968
969 // Timers/stats for gc scheduling and incremental mode pacing.
970 CMSStats& stats() { return _stats; }
971
972 // Adaptive size policy
973 AdaptiveSizePolicy* size_policy();
974
975 static void print_on_error(outputStream* st);
976
977 // Debugging
978 void verify();
979 bool verify_after_remark(bool silent = VerifySilently);
980 void verify_ok_to_terminate() const PRODUCT_RETURN;
981 void verify_work_stacks_empty() const PRODUCT_RETURN;
982 void verify_overflow_empty() const PRODUCT_RETURN;
983
984 // Convenience methods in support of debugging
985 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
986 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
987
988 // Accessors
989 CMSMarkStack* verification_mark_stack() { return &_markStack; }
990 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
991
992 // Initialization errors
993 bool completed_initialization() { return _completed_initialization; }
994
995 void print_eden_and_survivor_chunk_arrays();
996 };
997
998 class CMSExpansionCause : public AllStatic {
999 public:
1000 enum Cause {
1001 _no_expansion,
1002 _satisfy_free_ratio,
1003 _satisfy_promotion,
1004 _satisfy_allocation,
1005 _allocate_par_lab,
1006 _allocate_par_spooling_space,
1007 _adaptive_size_policy
1008 };
1009 // Return a string describing the cause of the expansion.
1010 static const char* to_string(CMSExpansionCause::Cause cause);
1011 };
1012
1013 class ConcurrentMarkSweepGeneration: public CardGeneration {
1014 friend class VMStructs;
1015 friend class ConcurrentMarkSweepThread;
1016 friend class ConcurrentMarkSweep;
1017 friend class CMSCollector;
1018 protected:
1019 static CMSCollector* _collector; // the collector that collects us
1020 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1021
1022 // Performance Counters
1023 GenerationCounters* _gen_counters;
1024 GSpaceCounters* _space_counters;
1025
1026 // Words directly allocated, used by CMSStats.
1027 size_t _direct_allocated_words;
1028
1029 // Non-product stat counters
1030 NOT_PRODUCT(
1031 size_t _numObjectsPromoted;
1032 size_t _numWordsPromoted;
1033 size_t _numObjectsAllocated;
1034 size_t _numWordsAllocated;
1035 )
1036
1037 // Used for sizing decisions
1038 bool _incremental_collection_failed;
1039 bool incremental_collection_failed() {
1040 return _incremental_collection_failed;
1041 }
1042 void set_incremental_collection_failed() {
1043 _incremental_collection_failed = true;
1044 }
1045 void clear_incremental_collection_failed() {
1046 _incremental_collection_failed = false;
1047 }
1048
1049 // accessors
1050 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1051 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1052
1053 private:
1054 // For parallel young-gen GC support.
1055 CMSParGCThreadState** _par_gc_thread_states;
1056
1057 // Reason generation was expanded
1058 CMSExpansionCause::Cause _expansion_cause;
1059
1060 // In support of MinChunkSize being larger than min object size
1061 const double _dilatation_factor;
1062
1063 enum CollectionTypes {
1064 Concurrent_collection_type = 0,
1065 MS_foreground_collection_type = 1,
1066 MSC_foreground_collection_type = 2,
1067 Unknown_collection_type = 3
1068 };
1069
1070 CollectionTypes _debug_collection_type;
1071
1072 // True if a compacting collection was done.
1073 bool _did_compact;
1074 bool did_compact() { return _did_compact; }
1075
1076 // Fraction of current occupancy at which to start a CMS collection which
1077 // will collect this generation (at least).
1078 double _initiating_occupancy;
1079
1080 protected:
1081 // Shrink generation by specified size (returns false if unable to shrink)
1082 void shrink_free_list_by(size_t bytes);
1083
1084 // Update statistics for GC
1085 virtual void update_gc_stats(int level, bool full);
1086
1087 // Maximum available space in the generation (including uncommitted)
1088 // space.
1089 size_t max_available() const;
1090
1091 // getter and initializer for _initiating_occupancy field.
1092 double initiating_occupancy() const { return _initiating_occupancy; }
1093 void init_initiating_occupancy(intx io, uintx tr);
1094
1095 public:
1096 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1097 int level, CardTableRS* ct,
1098 bool use_adaptive_freelists,
1099 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1100
1101 // Accessors
1102 CMSCollector* collector() const { return _collector; }
1103 static void set_collector(CMSCollector* collector) {
1104 assert(_collector == NULL, "already set");
1105 _collector = collector;
1106 }
1107 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1108
1109 Mutex* freelistLock() const;
1110
1111 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1112
1113 void set_did_compact(bool v) { _did_compact = v; }
1114
1115 bool refs_discovery_is_atomic() const { return false; }
1116 bool refs_discovery_is_mt() const {
1117 // Note: CMS does MT-discovery during the parallel-remark
1118 // phases. Use ReferenceProcessorMTMutator to make refs
1119 // discovery MT-safe during such phases or other parallel
1120 // discovery phases in the future. This may all go away
1121 // if/when we decide that refs discovery is sufficiently
1122 // rare that the cost of the CAS's involved is in the
1123 // noise. That's a measurement that should be done, and
1124 // the code simplified if that turns out to be the case.
1125 return ConcGCThreads > 1;
1126 }
1127
1128 // Override
1129 virtual void ref_processor_init();
1130
1131 // Grow generation by specified size (returns false if unable to grow)
1132 bool grow_by(size_t bytes);
1133 // Grow generation to reserved size.
1134 bool grow_to_reserved();
1135
1136 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1137
1138 // Space enquiries
1139 size_t capacity() const;
1140 size_t used() const;
1141 size_t free() const;
1142 double occupancy() const { return ((double)used())/((double)capacity()); }
1143 size_t contiguous_available() const;
1144 size_t unsafe_max_alloc_nogc() const;
1145
1146 // over-rides
1147 MemRegion used_region() const;
1148 MemRegion used_region_at_save_marks() const;
1149
1150 // Does a "full" (forced) collection invoked on this generation collect
1151 // all younger generations as well? Note that the second conjunct is a
1152 // hack to allow the collection of the younger gen first if the flag is
1153 // set.
1154 virtual bool full_collects_younger_generations() const {
1155 return UseCMSCompactAtFullCollection && !ScavengeBeforeFullGC;
1156 }
1157
1158 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1159
1160 // Support for compaction
1161 CompactibleSpace* first_compaction_space() const;
1162 // Adjust quantities in the generation affected by
1163 // the compaction.
1164 void reset_after_compaction();
1165
1166 // Allocation support
1167 HeapWord* allocate(size_t size, bool tlab);
1168 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1169 oop promote(oop obj, size_t obj_size);
1170 HeapWord* par_allocate(size_t size, bool tlab) {
1171 return allocate(size, tlab);
1172 }
1173
1174
1175 // Used by CMSStats to track direct allocation. The value is sampled and
1176 // reset after each young gen collection.
1177 size_t direct_allocated_words() const { return _direct_allocated_words; }
1178 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1179
1180 // Overrides for parallel promotion.
1181 virtual oop par_promote(int thread_num,
1182 oop obj, markOop m, size_t word_sz);
1183 // This one should not be called for CMS.
1184 virtual void par_promote_alloc_undo(int thread_num,
1185 HeapWord* obj, size_t word_sz);
1186 virtual void par_promote_alloc_done(int thread_num);
1187 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1188
1189 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1190
1191 // Inform this (non-young) generation that a promotion failure was
1192 // encountered during a collection of a younger generation that
1193 // promotes into this generation.
1194 virtual void promotion_failure_occurred();
1195
1196 bool should_collect(bool full, size_t size, bool tlab);
1197 virtual bool should_concurrent_collect() const;
1198 virtual bool is_too_full() const;
1199 void collect(bool full,
1200 bool clear_all_soft_refs,
1201 size_t size,
1202 bool tlab);
1203
1204 HeapWord* expand_and_allocate(size_t word_size,
1205 bool tlab,
1206 bool parallel = false);
1207
1208 // GC prologue and epilogue
1209 void gc_prologue(bool full);
1210 void gc_prologue_work(bool full, bool registerClosure,
1211 ModUnionClosure* modUnionClosure);
1212 void gc_epilogue(bool full);
1213 void gc_epilogue_work(bool full);
1214
1215 // Time since last GC of this generation
1216 jlong time_of_last_gc(jlong now) {
1217 return collector()->time_of_last_gc(now);
1218 }
1219 void update_time_of_last_gc(jlong now) {
1220 collector()-> update_time_of_last_gc(now);
1221 }
1222
1223 // Allocation failure
1224 void expand(size_t bytes, size_t expand_bytes,
1225 CMSExpansionCause::Cause cause);
1226 virtual bool expand(size_t bytes, size_t expand_bytes);
1227 void shrink(size_t bytes);
1228 void shrink_by(size_t bytes);
1229 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1230 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1231
1232 // Iteration support and related enquiries
1233 void save_marks();
1234 bool no_allocs_since_save_marks();
1235 void younger_refs_iterate(OopsInGenClosure* cl);
1236
1237 // Iteration support specific to CMS generations
1238 void save_sweep_limit();
1239
1240 // More iteration support
1241 virtual void oop_iterate(ExtendedOopClosure* cl);
1242 virtual void safe_object_iterate(ObjectClosure* cl);
1243 virtual void object_iterate(ObjectClosure* cl);
1244
1245 // Need to declare the full complement of closures, whether we'll
1246 // override them or not, or get message from the compiler:
1247 // oop_since_save_marks_iterate_nv hides virtual function...
1248 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1249 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1250 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1251
1252 // Smart allocation XXX -- move to CFLSpace?
1253 void setNearLargestChunk();
1254 bool isNearLargestChunk(HeapWord* addr);
1255
1256 // Get the chunk at the end of the space. Delegates to
1257 // the space.
1258 FreeChunk* find_chunk_at_end();
1259
1260 void post_compact();
1261
1262 // Debugging
1263 void prepare_for_verify();
1264 void verify();
1265 void print_statistics() PRODUCT_RETURN;
1266
1267 // Performance Counters support
1268 virtual void update_counters();
1269 virtual void update_counters(size_t used);
1270 void initialize_performance_counters();
1271 CollectorCounters* counters() { return collector()->counters(); }
1272
1273 // Support for parallel remark of survivor space
1274 void* get_data_recorder(int thr_num) {
1275 //Delegate to collector
1276 return collector()->get_data_recorder(thr_num);
1277 }
1278 void sample_eden_chunk() {
1279 //Delegate to collector
1280 return collector()->sample_eden_chunk();
1281 }
1282
1283 // Printing
1284 const char* name() const;
1285 virtual const char* short_name() const { return "CMS"; }
1286 void print() const;
1287 void printOccupancy(const char* s);
1288 bool must_be_youngest() const { return false; }
1289 bool must_be_oldest() const { return true; }
1290
1291 // Resize the generation after a compacting GC. The
1292 // generation can be treated as a contiguous space
1293 // after the compaction.
1294 virtual void compute_new_size();
1295 // Resize the generation after a non-compacting
1296 // collection.
1297 void compute_new_size_free_list();
1298
1299 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1300 void rotate_debug_collection_type();
1301 };
1302
1303 //
1304 // Closures of various sorts used by CMS to accomplish its work
1305 //
1306
1307 // This closure is used to do concurrent marking from the roots
1308 // following the first checkpoint.
1309 class MarkFromRootsClosure: public BitMapClosure {
1310 CMSCollector* _collector;
1311 MemRegion _span;
1312 CMSBitMap* _bitMap;
1313 CMSBitMap* _mut;
1314 CMSMarkStack* _markStack;
1315 bool _yield;
1316 int _skipBits;
1317 HeapWord* _finger;
1318 HeapWord* _threshold;
1319 DEBUG_ONLY(bool _verifying;)
1320
1321 public:
1322 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1323 CMSBitMap* bitMap,
1324 CMSMarkStack* markStack,
1325 bool should_yield, bool verifying = false);
1326 bool do_bit(size_t offset);
1327 void reset(HeapWord* addr);
1328 inline void do_yield_check();
1329
1330 private:
1331 void scanOopsInOop(HeapWord* ptr);
1332 void do_yield_work();
1333 };
1334
1335 // This closure is used to do concurrent multi-threaded
1336 // marking from the roots following the first checkpoint.
1337 // XXX This should really be a subclass of The serial version
1338 // above, but i have not had the time to refactor things cleanly.
1339 class Par_MarkFromRootsClosure: public BitMapClosure {
1340 CMSCollector* _collector;
1341 MemRegion _whole_span;
1342 MemRegion _span;
1343 CMSBitMap* _bit_map;
1344 CMSBitMap* _mut;
1345 OopTaskQueue* _work_queue;
1346 CMSMarkStack* _overflow_stack;
1347 bool _yield;
1348 int _skip_bits;
1349 HeapWord* _finger;
1350 HeapWord* _threshold;
1351 CMSConcMarkingTask* _task;
1352 public:
1353 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1354 MemRegion span,
1355 CMSBitMap* bit_map,
1356 OopTaskQueue* work_queue,
1357 CMSMarkStack* overflow_stack,
1358 bool should_yield);
1359 bool do_bit(size_t offset);
1360 inline void do_yield_check();
1361
1362 private:
1363 void scan_oops_in_oop(HeapWord* ptr);
1364 void do_yield_work();
1365 bool get_work_from_overflow_stack();
1366 };
1367
1368 // The following closures are used to do certain kinds of verification of
1369 // CMS marking.
1370 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1371 CMSCollector* _collector;
1372 MemRegion _span;
1373 CMSBitMap* _verification_bm;
1374 CMSBitMap* _cms_bm;
1375 CMSMarkStack* _mark_stack;
1376 protected:
1377 void do_oop(oop p);
1378 template <class T> inline void do_oop_work(T *p) {
1379 oop obj = oopDesc::load_decode_heap_oop(p);
1380 do_oop(obj);
1381 }
1382 public:
1383 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1384 MemRegion span,
1385 CMSBitMap* verification_bm,
1386 CMSBitMap* cms_bm,
1387 CMSMarkStack* mark_stack);
1388 void do_oop(oop* p);
1389 void do_oop(narrowOop* p);
1390
1391 // Deal with a stack overflow condition
1392 void handle_stack_overflow(HeapWord* lost);
1393 };
1394
1395 class MarkFromRootsVerifyClosure: public BitMapClosure {
1396 CMSCollector* _collector;
1397 MemRegion _span;
1398 CMSBitMap* _verification_bm;
1399 CMSBitMap* _cms_bm;
1400 CMSMarkStack* _mark_stack;
1401 HeapWord* _finger;
1402 PushAndMarkVerifyClosure _pam_verify_closure;
1403 public:
1404 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1405 CMSBitMap* verification_bm,
1406 CMSBitMap* cms_bm,
1407 CMSMarkStack* mark_stack);
1408 bool do_bit(size_t offset);
1409 void reset(HeapWord* addr);
1410 };
1411
1412
1413 // This closure is used to check that a certain set of bits is
1414 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1415 class FalseBitMapClosure: public BitMapClosure {
1416 public:
1417 bool do_bit(size_t offset) {
1418 guarantee(false, "Should not have a 1 bit");
1419 return true;
1420 }
1421 };
1422
1423 // A version of ObjectClosure with "memory" (see _previous_address below)
1424 class UpwardsObjectClosure: public BoolObjectClosure {
1425 HeapWord* _previous_address;
1426 public:
1427 UpwardsObjectClosure() : _previous_address(NULL) { }
1428 void set_previous(HeapWord* addr) { _previous_address = addr; }
1429 HeapWord* previous() { return _previous_address; }
1430 // A return value of "true" can be used by the caller to decide
1431 // if this object's end should *NOT* be recorded in
1432 // _previous_address above.
1433 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1434 };
1435
1436 // This closure is used during the second checkpointing phase
1437 // to rescan the marked objects on the dirty cards in the mod
1438 // union table and the card table proper. It's invoked via
1439 // MarkFromDirtyCardsClosure below. It uses either
1440 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1441 // declared in genOopClosures.hpp to accomplish some of its work.
1442 // In the parallel case the bitMap is shared, so access to
1443 // it needs to be suitably synchronized for updates by embedded
1444 // closures that update it; however, this closure itself only
1445 // reads the bit_map and because it is idempotent, is immune to
1446 // reading stale values.
1447 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1448 #ifdef ASSERT
1449 CMSCollector* _collector;
1450 MemRegion _span;
1451 union {
1452 CMSMarkStack* _mark_stack;
1453 OopTaskQueue* _work_queue;
1454 };
1455 #endif // ASSERT
1456 bool _parallel;
1457 CMSBitMap* _bit_map;
1458 union {
1459 MarkRefsIntoAndScanClosure* _scan_closure;
1460 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1461 };
1462
1463 public:
1464 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1465 MemRegion span,
1466 ReferenceProcessor* rp,
1467 CMSBitMap* bit_map,
1468 CMSMarkStack* mark_stack,
1469 MarkRefsIntoAndScanClosure* cl):
1470 #ifdef ASSERT
1471 _collector(collector),
1472 _span(span),
1473 _mark_stack(mark_stack),
1474 #endif // ASSERT
1475 _parallel(false),
1476 _bit_map(bit_map),
1477 _scan_closure(cl) { }
1478
1479 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1480 MemRegion span,
1481 ReferenceProcessor* rp,
1482 CMSBitMap* bit_map,
1483 OopTaskQueue* work_queue,
1484 Par_MarkRefsIntoAndScanClosure* cl):
1485 #ifdef ASSERT
1486 _collector(collector),
1487 _span(span),
1488 _work_queue(work_queue),
1489 #endif // ASSERT
1490 _parallel(true),
1491 _bit_map(bit_map),
1492 _par_scan_closure(cl) { }
1493
1494 bool do_object_b(oop obj) {
1495 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1496 return false;
1497 }
1498 bool do_object_bm(oop p, MemRegion mr);
1499 };
1500
1501 // This closure is used during the second checkpointing phase
1502 // to rescan the marked objects on the dirty cards in the mod
1503 // union table and the card table proper. It invokes
1504 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1505 // In the parallel case, the bit map is shared and requires
1506 // synchronized access.
1507 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1508 CompactibleFreeListSpace* _space;
1509 ScanMarkedObjectsAgainClosure _scan_cl;
1510 size_t _num_dirty_cards;
1511
1512 public:
1513 MarkFromDirtyCardsClosure(CMSCollector* collector,
1514 MemRegion span,
1515 CompactibleFreeListSpace* space,
1516 CMSBitMap* bit_map,
1517 CMSMarkStack* mark_stack,
1518 MarkRefsIntoAndScanClosure* cl):
1519 _space(space),
1520 _num_dirty_cards(0),
1521 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1522 mark_stack, cl) { }
1523
1524 MarkFromDirtyCardsClosure(CMSCollector* collector,
1525 MemRegion span,
1526 CompactibleFreeListSpace* space,
1527 CMSBitMap* bit_map,
1528 OopTaskQueue* work_queue,
1529 Par_MarkRefsIntoAndScanClosure* cl):
1530 _space(space),
1531 _num_dirty_cards(0),
1532 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1533 work_queue, cl) { }
1534
1535 void do_MemRegion(MemRegion mr);
1536 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1537 size_t num_dirty_cards() { return _num_dirty_cards; }
1538 };
1539
1540 // This closure is used in the non-product build to check
1541 // that there are no MemRegions with a certain property.
1542 class FalseMemRegionClosure: public MemRegionClosure {
1543 void do_MemRegion(MemRegion mr) {
1544 guarantee(!mr.is_empty(), "Shouldn't be empty");
1545 guarantee(false, "Should never be here");
1546 }
1547 };
1548
1549 // This closure is used during the precleaning phase
1550 // to "carefully" rescan marked objects on dirty cards.
1551 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1552 // to accomplish some of its work.
1553 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1554 CMSCollector* _collector;
1555 MemRegion _span;
1556 bool _yield;
1557 Mutex* _freelistLock;
1558 CMSBitMap* _bitMap;
1559 CMSMarkStack* _markStack;
1560 MarkRefsIntoAndScanClosure* _scanningClosure;
1561
1562 public:
1563 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1564 MemRegion span,
1565 CMSBitMap* bitMap,
1566 CMSMarkStack* markStack,
1567 MarkRefsIntoAndScanClosure* cl,
1568 bool should_yield):
1569 _collector(collector),
1570 _span(span),
1571 _yield(should_yield),
1572 _bitMap(bitMap),
1573 _markStack(markStack),
1574 _scanningClosure(cl) {
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 guarantee(false, "Unexpected caller");
1583 return 0;
1584 }
1585
1586 size_t do_object_careful_m(oop p, MemRegion mr);
1587
1588 void setFreelistLock(Mutex* m) {
1589 _freelistLock = m;
1590 _scanningClosure->set_freelistLock(m);
1591 }
1592
1593 private:
1594 inline bool do_yield_check();
1595
1596 void do_yield_work();
1597 };
1598
1599 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1600 CMSCollector* _collector;
1601 MemRegion _span;
1602 bool _yield;
1603 CMSBitMap* _bit_map;
1604 CMSMarkStack* _mark_stack;
1605 PushAndMarkClosure* _scanning_closure;
1606 unsigned int _before_count;
1607
1608 public:
1609 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1610 MemRegion span,
1611 CMSBitMap* bit_map,
1612 CMSMarkStack* mark_stack,
1613 PushAndMarkClosure* cl,
1614 unsigned int before_count,
1615 bool should_yield):
1616 _collector(collector),
1617 _span(span),
1618 _yield(should_yield),
1619 _bit_map(bit_map),
1620 _mark_stack(mark_stack),
1621 _scanning_closure(cl),
1622 _before_count(before_count)
1623 { }
1624
1625 void do_object(oop p) {
1626 guarantee(false, "call do_object_careful instead");
1627 }
1628
1629 size_t do_object_careful(oop p);
1630
1631 size_t do_object_careful_m(oop p, MemRegion mr) {
1632 guarantee(false, "Unexpected caller");
1633 return 0;
1634 }
1635
1636 private:
1637 inline void do_yield_check();
1638 void do_yield_work();
1639 };
1640
1641 // This closure is used to accomplish the sweeping work
1642 // after the second checkpoint but before the concurrent reset
1643 // phase.
1644 //
1645 // Terminology
1646 // left hand chunk (LHC) - block of one or more chunks currently being
1647 // coalesced. The LHC is available for coalescing with a new chunk.
1648 // right hand chunk (RHC) - block that is currently being swept that is
1649 // free or garbage that can be coalesced with the LHC.
1650 // _inFreeRange is true if there is currently a LHC
1651 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1652 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1653 // _freeFinger is the address of the current LHC
1654 class SweepClosure: public BlkClosureCareful {
1655 CMSCollector* _collector; // collector doing the work
1656 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1657 CompactibleFreeListSpace* _sp; // Space being swept
1658 HeapWord* _limit;// the address at or above which the sweep should stop
1659 // because we do not expect newly garbage blocks
1660 // eligible for sweeping past that address.
1661 Mutex* _freelistLock; // Free list lock (in space)
1662 CMSBitMap* _bitMap; // Marking bit map (in
1663 // generation)
1664 bool _inFreeRange; // Indicates if we are in the
1665 // midst of a free run
1666 bool _freeRangeInFreeLists;
1667 // Often, we have just found
1668 // a free chunk and started
1669 // a new free range; we do not
1670 // eagerly remove this chunk from
1671 // the free lists unless there is
1672 // a possibility of coalescing.
1673 // When true, this flag indicates
1674 // that the _freeFinger below
1675 // points to a potentially free chunk
1676 // that may still be in the free lists
1677 bool _lastFreeRangeCoalesced;
1678 // free range contains chunks
1679 // coalesced
1680 bool _yield;
1681 // Whether sweeping should be
1682 // done with yields. For instance
1683 // when done by the foreground
1684 // collector we shouldn't yield.
1685 HeapWord* _freeFinger; // When _inFreeRange is set, the
1686 // pointer to the "left hand
1687 // chunk"
1688 size_t _freeRangeSize;
1689 // When _inFreeRange is set, this
1690 // indicates the accumulated size
1691 // of the "left hand chunk"
1692 NOT_PRODUCT(
1693 size_t _numObjectsFreed;
1694 size_t _numWordsFreed;
1695 size_t _numObjectsLive;
1696 size_t _numWordsLive;
1697 size_t _numObjectsAlreadyFree;
1698 size_t _numWordsAlreadyFree;
1699 FreeChunk* _last_fc;
1700 )
1701 private:
1702 // Code that is common to a free chunk or garbage when
1703 // encountered during sweeping.
1704 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1705 // Process a free chunk during sweeping.
1706 void do_already_free_chunk(FreeChunk *fc);
1707 // Work method called when processing an already free or a
1708 // freshly garbage chunk to do a lookahead and possibly a
1709 // preemptive flush if crossing over _limit.
1710 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1711 // Process a garbage chunk during sweeping.
1712 size_t do_garbage_chunk(FreeChunk *fc);
1713 // Process a live chunk during sweeping.
1714 size_t do_live_chunk(FreeChunk* fc);
1715
1716 // Accessors.
1717 HeapWord* freeFinger() const { return _freeFinger; }
1718 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1719 bool inFreeRange() const { return _inFreeRange; }
1720 void set_inFreeRange(bool v) { _inFreeRange = v; }
1721 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1722 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1723 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1724 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1725
1726 // Initialize a free range.
1727 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1728 // Return this chunk to the free lists.
1729 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1730
1731 // Check if we should yield and do so when necessary.
1732 inline void do_yield_check(HeapWord* addr);
1733
1734 // Yield
1735 void do_yield_work(HeapWord* addr);
1736
1737 // Debugging/Printing
1738 void print_free_block_coalesced(FreeChunk* fc) const;
1739
1740 public:
1741 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1742 CMSBitMap* bitMap, bool should_yield);
1743 ~SweepClosure() PRODUCT_RETURN;
1744
1745 size_t do_blk_careful(HeapWord* addr);
1746 void print() const { print_on(tty); }
1747 void print_on(outputStream *st) const;
1748 };
1749
1750 // Closures related to weak references processing
1751
1752 // During CMS' weak reference processing, this is a
1753 // work-routine/closure used to complete transitive
1754 // marking of objects as live after a certain point
1755 // in which an initial set has been completely accumulated.
1756 // This closure is currently used both during the final
1757 // remark stop-world phase, as well as during the concurrent
1758 // precleaning of the discovered reference lists.
1759 class CMSDrainMarkingStackClosure: public VoidClosure {
1760 CMSCollector* _collector;
1761 MemRegion _span;
1762 CMSMarkStack* _mark_stack;
1763 CMSBitMap* _bit_map;
1764 CMSKeepAliveClosure* _keep_alive;
1765 bool _concurrent_precleaning;
1766 public:
1767 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1768 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1769 CMSKeepAliveClosure* keep_alive,
1770 bool cpc):
1771 _collector(collector),
1772 _span(span),
1773 _bit_map(bit_map),
1774 _mark_stack(mark_stack),
1775 _keep_alive(keep_alive),
1776 _concurrent_precleaning(cpc) {
1777 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1778 "Mismatch");
1779 }
1780
1781 void do_void();
1782 };
1783
1784 // A parallel version of CMSDrainMarkingStackClosure above.
1785 class CMSParDrainMarkingStackClosure: public VoidClosure {
1786 CMSCollector* _collector;
1787 MemRegion _span;
1788 OopTaskQueue* _work_queue;
1789 CMSBitMap* _bit_map;
1790 CMSInnerParMarkAndPushClosure _mark_and_push;
1791
1792 public:
1793 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1794 MemRegion span, CMSBitMap* bit_map,
1795 OopTaskQueue* work_queue):
1796 _collector(collector),
1797 _span(span),
1798 _bit_map(bit_map),
1799 _work_queue(work_queue),
1800 _mark_and_push(collector, span, bit_map, work_queue) { }
1801
1802 public:
1803 void trim_queue(uint max);
1804 void do_void();
1805 };
1806
1807 // Allow yielding or short-circuiting of reference list
1808 // precleaning work.
1809 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1810 CMSCollector* _collector;
1811 void do_yield_work();
1812 public:
1813 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1814 _collector(collector) {}
1815 virtual bool should_return();
1816 };
1817
1818
1819 // Convenience class that locks free list locks for given CMS collector
1820 class FreelistLocker: public StackObj {
1821 private:
1822 CMSCollector* _collector;
1823 public:
1824 FreelistLocker(CMSCollector* collector):
1825 _collector(collector) {
1826 _collector->getFreelistLocks();
1827 }
1828
1829 ~FreelistLocker() {
1830 _collector->releaseFreelistLocks();
1831 }
1832 };
1833
1834 // Mark all dead objects in a given space.
1835 class MarkDeadObjectsClosure: public BlkClosure {
1836 const CMSCollector* _collector;
1837 const CompactibleFreeListSpace* _sp;
1838 CMSBitMap* _live_bit_map;
1839 CMSBitMap* _dead_bit_map;
1840 public:
1841 MarkDeadObjectsClosure(const CMSCollector* collector,
1842 const CompactibleFreeListSpace* sp,
1843 CMSBitMap *live_bit_map,
1844 CMSBitMap *dead_bit_map) :
1845 _collector(collector),
1846 _sp(sp),
1847 _live_bit_map(live_bit_map),
1848 _dead_bit_map(dead_bit_map) {}
1849 size_t do_blk(HeapWord* addr);
1850 };
1851
1852 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1853
1854 public:
1855 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1856 };
1857
1858
1859 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP