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/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 Monitor::_safepoint_check_never),
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_foreground_gc_start(GCCause::Cause cause);
613 void register_gc_start(GCCause::Cause cause);
614 void register_gc_end();
615 void save_heap_summary();
616 void report_heap_summary(GCWhen::Type when);
617
618 protected:
619 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
620 MemRegion _span; // Span covering above two
621 CardTableRS* _ct; // Card table
622
623 // CMS marking support structures
624 CMSBitMap _markBitMap;
625 CMSBitMap _modUnionTable;
626 CMSMarkStack _markStack;
627
628 HeapWord* _restart_addr; // In support of marking stack overflow
629 void lower_restart_addr(HeapWord* low);
630
631 // Counters in support of marking stack / work queue overflow handling:
632 // a non-zero value indicates certain types of overflow events during
633 // the current CMS cycle and could lead to stack resizing efforts at
634 // an opportune future time.
635 size_t _ser_pmc_preclean_ovflw;
636 size_t _ser_pmc_remark_ovflw;
637 size_t _par_pmc_remark_ovflw;
638 size_t _ser_kac_preclean_ovflw;
639 size_t _ser_kac_ovflw;
640 size_t _par_kac_ovflw;
641 NOT_PRODUCT(ssize_t _num_par_pushes;)
642
643 // ("Weak") Reference processing support.
644 ReferenceProcessor* _ref_processor;
645 CMSIsAliveClosure _is_alive_closure;
646 // Keep this textually after _markBitMap and _span; c'tor dependency.
647
648 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
649 ModUnionClosure _modUnionClosure;
650 ModUnionClosurePar _modUnionClosurePar;
651
652 // CMS abstract state machine
653 // initial_state: Idling
654 // next_state(Idling) = {Marking}
655 // next_state(Marking) = {Precleaning, Sweeping}
656 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
657 // next_state(AbortablePreclean) = {FinalMarking}
658 // next_state(FinalMarking) = {Sweeping}
659 // next_state(Sweeping) = {Resizing}
660 // next_state(Resizing) = {Resetting}
661 // next_state(Resetting) = {Idling}
662 // The numeric values below are chosen so that:
663 // . _collectorState <= Idling == post-sweep && pre-mark
664 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
665 // precleaning || abortablePrecleanb
666 public:
667 enum CollectorState {
668 Resizing = 0,
669 Resetting = 1,
670 Idling = 2,
671 InitialMarking = 3,
672 Marking = 4,
673 Precleaning = 5,
674 AbortablePreclean = 6,
675 FinalMarking = 7,
676 Sweeping = 8
677 };
678 protected:
679 static CollectorState _collectorState;
680
681 // State related to prologue/epilogue invocation for my generations
682 bool _between_prologue_and_epilogue;
683
684 // Signaling/State related to coordination between fore- and background GC
685 // Note: When the baton has been passed from background GC to foreground GC,
686 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
687 static bool _foregroundGCIsActive; // true iff foreground collector is active or
688 // wants to go active
689 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
690 // yet passed the baton to the foreground GC
691
692 // Support for CMSScheduleRemark (abortable preclean)
693 bool _abort_preclean;
694 bool _start_sampling;
695
696 int _numYields;
697 size_t _numDirtyCards;
698 size_t _sweep_count;
699 // Number of full gc's since the last concurrent gc.
700 uint _full_gcs_since_conc_gc;
701
702 // Occupancy used for bootstrapping stats
703 double _bootstrap_occupancy;
704
705 // Timer
706 elapsedTimer _timer;
707
708 // Timing, allocation and promotion statistics, used for scheduling.
709 CMSStats _stats;
710
711 enum CMS_op_type {
712 CMS_op_checkpointRootsInitial,
713 CMS_op_checkpointRootsFinal
714 };
715
716 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
717 bool stop_world_and_do(CMS_op_type op);
718
719 OopTaskQueueSet* task_queues() { return _task_queues; }
720 int* hash_seed(int i) { return &_hash_seed[i]; }
721 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
722
723 // Support for parallelizing Eden rescan in CMS remark phase
724 void sample_eden(); // ... sample Eden space top
725
726 private:
727 // Support for parallelizing young gen rescan in CMS remark phase
728 Generation* _young_gen; // the younger gen
729 HeapWord** _top_addr; // ... Top of Eden
730 HeapWord** _end_addr; // ... End of Eden
731 Mutex* _eden_chunk_lock;
732 HeapWord** _eden_chunk_array; // ... Eden partitioning array
733 size_t _eden_chunk_index; // ... top (exclusive) of array
734 size_t _eden_chunk_capacity; // ... max entries in array
735
736 // Support for parallelizing survivor space rescan
737 HeapWord** _survivor_chunk_array;
738 size_t _survivor_chunk_index;
739 size_t _survivor_chunk_capacity;
740 size_t* _cursor;
741 ChunkArray* _survivor_plab_array;
742
743 // Support for marking stack overflow handling
744 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
745 bool par_take_from_overflow_list(size_t num,
746 OopTaskQueue* to_work_q,
747 int no_of_gc_threads);
748 void push_on_overflow_list(oop p);
749 void par_push_on_overflow_list(oop p);
750 // The following is, obviously, not, in general, "MT-stable"
751 bool overflow_list_is_empty() const;
752
753 void preserve_mark_if_necessary(oop p);
754 void par_preserve_mark_if_necessary(oop p);
755 void preserve_mark_work(oop p, markOop m);
756 void restore_preserved_marks_if_any();
757 NOT_PRODUCT(bool no_preserved_marks() const;)
758 // In support of testing overflow code
759 NOT_PRODUCT(int _overflow_counter;)
760 NOT_PRODUCT(bool simulate_overflow();) // Sequential
761 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
762
763 // CMS work methods
764 void checkpointRootsInitialWork(bool asynch); // Initial checkpoint work
765
766 // A return value of false indicates failure due to stack overflow
767 bool markFromRootsWork(bool asynch); // Concurrent marking work
768
769 public: // FIX ME!!! only for testing
770 bool do_marking_st(bool asynch); // Single-threaded marking
771 bool do_marking_mt(bool asynch); // Multi-threaded marking
772
773 private:
774
775 // Concurrent precleaning work
776 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
777 ScanMarkedObjectsAgainCarefullyClosure* cl);
778 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
779 ScanMarkedObjectsAgainCarefullyClosure* cl);
780 // Does precleaning work, returning a quantity indicative of
781 // the amount of "useful work" done.
782 size_t preclean_work(bool clean_refs, bool clean_survivors);
783 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
784 void abortable_preclean(); // Preclean while looking for possible abort
785 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
786 // Helper function for above; merge-sorts the per-thread plab samples
787 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
788 // Resets (i.e. clears) the per-thread plab sample vectors
789 void reset_survivor_plab_arrays();
790
791 // Final (second) checkpoint work
792 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
793 bool init_mark_was_synchronous);
794 // Work routine for parallel version of remark
795 void do_remark_parallel();
796 // Work routine for non-parallel version of remark
797 void do_remark_non_parallel();
798 // Reference processing work routine (during second checkpoint)
799 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
800
801 // Concurrent sweeping work
802 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
803
804 // (Concurrent) resetting of support data structures
805 void reset(bool asynch);
806
807 // Clear _expansion_cause fields of constituent generations
808 void clear_expansion_cause();
809
810 // An auxiliary method used to record the ends of
811 // used regions of each generation to limit the extent of sweep
812 void save_sweep_limits();
813
814 // A work method used by foreground collection to determine
815 // what type of collection (compacting or not, continuing or fresh)
816 // it should do.
817 void decide_foreground_collection_type(bool clear_all_soft_refs,
818 bool* should_compact, bool* should_start_over);
819
820 // A work method used by the foreground collector to do
821 // a mark-sweep-compact.
822 void do_compaction_work(bool clear_all_soft_refs);
823
824 // A work method used by the foreground collector to do
825 // a mark-sweep, after taking over from a possibly on-going
826 // concurrent mark-sweep collection.
827 void do_mark_sweep_work(bool clear_all_soft_refs,
828 CollectorState first_state, bool should_start_over);
829
830 // Work methods for reporting concurrent mode interruption or failure
831 bool is_external_interruption();
832 void report_concurrent_mode_interruption();
833
834 // If the background GC is active, acquire control from the background
835 // GC and do the collection.
836 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
837
838 // For synchronizing passing of control from background to foreground
839 // GC. waitForForegroundGC() is called by the background
840 // collector. It if had to wait for a foreground collection,
841 // it returns true and the background collection should assume
842 // that the collection was finished by the foreground
843 // collector.
844 bool waitForForegroundGC();
845
846 size_t block_size_using_printezis_bits(HeapWord* addr) const;
847 size_t block_size_if_printezis_bits(HeapWord* addr) const;
848 HeapWord* next_card_start_after_block(HeapWord* addr) const;
849
850 void setup_cms_unloading_and_verification_state();
851 public:
852 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
853 CardTableRS* ct,
854 ConcurrentMarkSweepPolicy* cp);
855 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
856
857 ReferenceProcessor* ref_processor() { return _ref_processor; }
858 void ref_processor_init();
859
860 Mutex* bitMapLock() const { return _markBitMap.lock(); }
861 static CollectorState abstract_state() { return _collectorState; }
862
863 bool should_abort_preclean() const; // Whether preclean should be aborted.
864 size_t get_eden_used() const;
865 size_t get_eden_capacity() const;
866
867 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
868
869 // Locking checks
870 NOT_PRODUCT(static bool have_cms_token();)
871
872 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
873 bool shouldConcurrentCollect();
874
875 void collect(bool full,
876 bool clear_all_soft_refs,
877 size_t size,
878 bool tlab);
879 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
880 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
881
882 // In support of ExplicitGCInvokesConcurrent
883 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
884 // Should we unload classes in a particular concurrent cycle?
885 bool should_unload_classes() const {
886 return _should_unload_classes;
887 }
888 void update_should_unload_classes();
889
890 void direct_allocated(HeapWord* start, size_t size);
891
892 // Object is dead if not marked and current phase is sweeping.
893 bool is_dead_obj(oop obj) const;
894
895 // After a promotion (of "start"), do any necessary marking.
896 // If "par", then it's being done by a parallel GC thread.
897 // The last two args indicate if we need precise marking
898 // and if so the size of the object so it can be dirtied
899 // in its entirety.
900 void promoted(bool par, HeapWord* start,
901 bool is_obj_array, size_t obj_size);
902
903 void getFreelistLocks() const;
904 void releaseFreelistLocks() const;
905 bool haveFreelistLocks() const;
906
907 // Adjust size of underlying generation
908 void compute_new_size();
909
910 // GC prologue and epilogue
911 void gc_prologue(bool full);
912 void gc_epilogue(bool full);
913
914 jlong time_of_last_gc(jlong now) {
915 if (_collectorState <= Idling) {
916 // gc not in progress
917 return _time_of_last_gc;
918 } else {
919 // collection in progress
920 return now;
921 }
922 }
923
924 // Support for parallel remark of survivor space
925 void* get_data_recorder(int thr_num);
926 void sample_eden_chunk();
927
928 CMSBitMap* markBitMap() { return &_markBitMap; }
929 void directAllocated(HeapWord* start, size_t size);
930
931 // Main CMS steps and related support
932 void checkpointRootsInitial(bool asynch);
933 bool markFromRoots(bool asynch); // a return value of false indicates failure
934 // due to stack overflow
935 void preclean();
936 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
937 bool init_mark_was_synchronous);
938 void sweep(bool asynch);
939
940 // Check that the currently executing thread is the expected
941 // one (foreground collector or background collector).
942 static void check_correct_thread_executing() PRODUCT_RETURN;
943 // XXXPERM void print_statistics() PRODUCT_RETURN;
944
945 bool is_cms_reachable(HeapWord* addr);
946
947 // Performance Counter Support
948 CollectorCounters* counters() { return _gc_counters; }
949
950 // Timer stuff
951 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
952 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
953 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
954 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
955
956 int yields() { return _numYields; }
957 void resetYields() { _numYields = 0; }
958 void incrementYields() { _numYields++; }
959 void resetNumDirtyCards() { _numDirtyCards = 0; }
960 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
961 size_t numDirtyCards() { return _numDirtyCards; }
962
963 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
964 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
965 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
966 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
967 size_t sweep_count() const { return _sweep_count; }
968 void increment_sweep_count() { _sweep_count++; }
969
970 // Timers/stats for gc scheduling and incremental mode pacing.
971 CMSStats& stats() { return _stats; }
972
973 // Adaptive size policy
974 AdaptiveSizePolicy* size_policy();
975
976 static void print_on_error(outputStream* st);
977
978 // Debugging
979 void verify();
980 bool verify_after_remark(bool silent = VerifySilently);
981 void verify_ok_to_terminate() const PRODUCT_RETURN;
982 void verify_work_stacks_empty() const PRODUCT_RETURN;
983 void verify_overflow_empty() const PRODUCT_RETURN;
984
985 // Convenience methods in support of debugging
986 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
987 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
988
989 // Accessors
990 CMSMarkStack* verification_mark_stack() { return &_markStack; }
991 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
992
993 // Initialization errors
994 bool completed_initialization() { return _completed_initialization; }
995
996 void print_eden_and_survivor_chunk_arrays();
997 };
998
999 class CMSExpansionCause : public AllStatic {
1000 public:
1001 enum Cause {
1002 _no_expansion,
1003 _satisfy_free_ratio,
1004 _satisfy_promotion,
1005 _satisfy_allocation,
1006 _allocate_par_lab,
1007 _allocate_par_spooling_space,
1008 _adaptive_size_policy
1009 };
1010 // Return a string describing the cause of the expansion.
1011 static const char* to_string(CMSExpansionCause::Cause cause);
1012 };
1013
1014 class ConcurrentMarkSweepGeneration: public CardGeneration {
1015 friend class VMStructs;
1016 friend class ConcurrentMarkSweepThread;
1017 friend class ConcurrentMarkSweep;
1018 friend class CMSCollector;
1019 protected:
1020 static CMSCollector* _collector; // the collector that collects us
1021 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1022
1023 // Performance Counters
1024 GenerationCounters* _gen_counters;
1025 GSpaceCounters* _space_counters;
1026
1027 // Words directly allocated, used by CMSStats.
1028 size_t _direct_allocated_words;
1029
1030 // Non-product stat counters
1031 NOT_PRODUCT(
1032 size_t _numObjectsPromoted;
1033 size_t _numWordsPromoted;
1034 size_t _numObjectsAllocated;
1035 size_t _numWordsAllocated;
1036 )
1037
1038 // Used for sizing decisions
1039 bool _incremental_collection_failed;
1040 bool incremental_collection_failed() {
1041 return _incremental_collection_failed;
1042 }
1043 void set_incremental_collection_failed() {
1044 _incremental_collection_failed = true;
1045 }
1046 void clear_incremental_collection_failed() {
1047 _incremental_collection_failed = false;
1048 }
1049
1050 // accessors
1051 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1052 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1053
1054 private:
1055 // For parallel young-gen GC support.
1056 CMSParGCThreadState** _par_gc_thread_states;
1057
1058 // Reason generation was expanded
1059 CMSExpansionCause::Cause _expansion_cause;
1060
1061 // In support of MinChunkSize being larger than min object size
1062 const double _dilatation_factor;
1063
1064 enum CollectionTypes {
1065 Concurrent_collection_type = 0,
1066 MS_foreground_collection_type = 1,
1067 MSC_foreground_collection_type = 2,
1068 Unknown_collection_type = 3
1069 };
1070
1071 CollectionTypes _debug_collection_type;
1072
1073 // True if a compacting collection was done.
1074 bool _did_compact;
1075 bool did_compact() { return _did_compact; }
1076
1077 // Fraction of current occupancy at which to start a CMS collection which
1078 // will collect this generation (at least).
1079 double _initiating_occupancy;
1080
1081 protected:
1082 // Shrink generation by specified size (returns false if unable to shrink)
1083 void shrink_free_list_by(size_t bytes);
1084
1085 // Update statistics for GC
1086 virtual void update_gc_stats(int level, bool full);
1087
1088 // Maximum available space in the generation (including uncommitted)
1089 // space.
1090 size_t max_available() const;
1091
1092 // getter and initializer for _initiating_occupancy field.
1093 double initiating_occupancy() const { return _initiating_occupancy; }
1094 void init_initiating_occupancy(intx io, uintx tr);
1095
1096 public:
1097 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1098 int level, CardTableRS* ct,
1099 bool use_adaptive_freelists,
1100 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1101
1102 // Accessors
1103 CMSCollector* collector() const { return _collector; }
1104 static void set_collector(CMSCollector* collector) {
1105 assert(_collector == NULL, "already set");
1106 _collector = collector;
1107 }
1108 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1109
1110 Mutex* freelistLock() const;
1111
1112 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1113
1114 void set_did_compact(bool v) { _did_compact = v; }
1115
1116 bool refs_discovery_is_atomic() const { return false; }
1117 bool refs_discovery_is_mt() const {
1118 // Note: CMS does MT-discovery during the parallel-remark
1119 // phases. Use ReferenceProcessorMTMutator to make refs
1120 // discovery MT-safe during such phases or other parallel
1121 // discovery phases in the future. This may all go away
1122 // if/when we decide that refs discovery is sufficiently
1123 // rare that the cost of the CAS's involved is in the
1124 // noise. That's a measurement that should be done, and
1125 // the code simplified if that turns out to be the case.
1126 return ConcGCThreads > 1;
1127 }
1128
1129 // Override
1130 virtual void ref_processor_init();
1131
1132 // Grow generation by specified size (returns false if unable to grow)
1133 bool grow_by(size_t bytes);
1134 // Grow generation to reserved size.
1135 bool grow_to_reserved();
1136
1137 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1138
1139 // Space enquiries
1140 size_t capacity() const;
1141 size_t used() const;
1142 size_t free() const;
1143 double occupancy() const { return ((double)used())/((double)capacity()); }
1144 size_t contiguous_available() const;
1145 size_t unsafe_max_alloc_nogc() const;
1146
1147 // over-rides
1148 MemRegion used_region() const;
1149 MemRegion used_region_at_save_marks() const;
1150
1151 // Does a "full" (forced) collection invoked on this generation collect
1152 // all younger generations as well? Note that the second conjunct is a
1153 // hack to allow the collection of the younger gen first if the flag is
1154 // set.
1155 virtual bool full_collects_younger_generations() const {
1156 return UseCMSCompactAtFullCollection && !ScavengeBeforeFullGC;
1157 }
1158
1159 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1160
1161 // Support for compaction
1162 CompactibleSpace* first_compaction_space() const;
1163 // Adjust quantities in the generation affected by
1164 // the compaction.
1165 void reset_after_compaction();
1166
1167 // Allocation support
1168 HeapWord* allocate(size_t size, bool tlab);
1169 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1170 oop promote(oop obj, size_t obj_size);
1171 HeapWord* par_allocate(size_t size, bool tlab) {
1172 return allocate(size, tlab);
1173 }
1174
1175
1176 // Used by CMSStats to track direct allocation. The value is sampled and
1177 // reset after each young gen collection.
1178 size_t direct_allocated_words() const { return _direct_allocated_words; }
1179 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1180
1181 // Overrides for parallel promotion.
1182 virtual oop par_promote(int thread_num,
1183 oop obj, markOop m, size_t word_sz);
1184 // This one should not be called for CMS.
1185 virtual void par_promote_alloc_undo(int thread_num,
1186 HeapWord* obj, size_t word_sz);
1187 virtual void par_promote_alloc_done(int thread_num);
1188 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1189
1190 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1191
1192 // Inform this (non-young) generation that a promotion failure was
1193 // encountered during a collection of a younger generation that
1194 // promotes into this generation.
1195 virtual void promotion_failure_occurred();
1196
1197 bool should_collect(bool full, size_t size, bool tlab);
1198 virtual bool should_concurrent_collect() const;
1199 virtual bool is_too_full() const;
1200 void collect(bool full,
1201 bool clear_all_soft_refs,
1202 size_t size,
1203 bool tlab);
1204
1205 HeapWord* expand_and_allocate(size_t word_size,
1206 bool tlab,
1207 bool parallel = false);
1208
1209 // GC prologue and epilogue
1210 void gc_prologue(bool full);
1211 void gc_prologue_work(bool full, bool registerClosure,
1212 ModUnionClosure* modUnionClosure);
1213 void gc_epilogue(bool full);
1214 void gc_epilogue_work(bool full);
1215
1216 // Time since last GC of this generation
1217 jlong time_of_last_gc(jlong now) {
1218 return collector()->time_of_last_gc(now);
1219 }
1220 void update_time_of_last_gc(jlong now) {
1221 collector()-> update_time_of_last_gc(now);
1222 }
1223
1224 // Allocation failure
1225 void expand(size_t bytes, size_t expand_bytes,
1226 CMSExpansionCause::Cause cause);
1227 virtual bool expand(size_t bytes, size_t expand_bytes);
1228 void shrink(size_t bytes);
1229 void shrink_by(size_t bytes);
1230 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1231 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1232
1233 // Iteration support and related enquiries
1234 void save_marks();
1235 bool no_allocs_since_save_marks();
1236 void younger_refs_iterate(OopsInGenClosure* cl);
1237
1238 // Iteration support specific to CMS generations
1239 void save_sweep_limit();
1240
1241 // More iteration support
1242 virtual void oop_iterate(ExtendedOopClosure* cl);
1243 virtual void safe_object_iterate(ObjectClosure* cl);
1244 virtual void object_iterate(ObjectClosure* cl);
1245
1246 // Need to declare the full complement of closures, whether we'll
1247 // override them or not, or get message from the compiler:
1248 // oop_since_save_marks_iterate_nv hides virtual function...
1249 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1250 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1251 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1252
1253 // Smart allocation XXX -- move to CFLSpace?
1254 void setNearLargestChunk();
1255 bool isNearLargestChunk(HeapWord* addr);
1256
1257 // Get the chunk at the end of the space. Delegates to
1258 // the space.
1259 FreeChunk* find_chunk_at_end();
1260
1261 void post_compact();
1262
1263 // Debugging
1264 void prepare_for_verify();
1265 void verify();
1266 void print_statistics() PRODUCT_RETURN;
1267
1268 // Performance Counters support
1269 virtual void update_counters();
1270 virtual void update_counters(size_t used);
1271 void initialize_performance_counters();
1272 CollectorCounters* counters() { return collector()->counters(); }
1273
1274 // Support for parallel remark of survivor space
1275 void* get_data_recorder(int thr_num) {
1276 //Delegate to collector
1277 return collector()->get_data_recorder(thr_num);
1278 }
1279 void sample_eden_chunk() {
1280 //Delegate to collector
1281 return collector()->sample_eden_chunk();
1282 }
1283
1284 // Printing
1285 const char* name() const;
1286 virtual const char* short_name() const { return "CMS"; }
1287 void print() const;
1288 void printOccupancy(const char* s);
1289 bool must_be_youngest() const { return false; }
1290 bool must_be_oldest() const { return true; }
1291
1292 // Resize the generation after a compacting GC. The
1293 // generation can be treated as a contiguous space
1294 // after the compaction.
1295 virtual void compute_new_size();
1296 // Resize the generation after a non-compacting
1297 // collection.
1298 void compute_new_size_free_list();
1299
1300 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1301 void rotate_debug_collection_type();
1302 };
1303
1304 //
1305 // Closures of various sorts used by CMS to accomplish its work
1306 //
1307
1308 // This closure is used to do concurrent marking from the roots
1309 // following the first checkpoint.
1310 class MarkFromRootsClosure: public BitMapClosure {
1311 CMSCollector* _collector;
1312 MemRegion _span;
1313 CMSBitMap* _bitMap;
1314 CMSBitMap* _mut;
1315 CMSMarkStack* _markStack;
1316 bool _yield;
1317 int _skipBits;
1318 HeapWord* _finger;
1319 HeapWord* _threshold;
1320 DEBUG_ONLY(bool _verifying;)
1321
1322 public:
1323 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1324 CMSBitMap* bitMap,
1325 CMSMarkStack* markStack,
1326 bool should_yield, bool verifying = false);
1327 bool do_bit(size_t offset);
1328 void reset(HeapWord* addr);
1329 inline void do_yield_check();
1330
1331 private:
1332 void scanOopsInOop(HeapWord* ptr);
1333 void do_yield_work();
1334 };
1335
1336 // This closure is used to do concurrent multi-threaded
1337 // marking from the roots following the first checkpoint.
1338 // XXX This should really be a subclass of The serial version
1339 // above, but i have not had the time to refactor things cleanly.
1340 class Par_MarkFromRootsClosure: public BitMapClosure {
1341 CMSCollector* _collector;
1342 MemRegion _whole_span;
1343 MemRegion _span;
1344 CMSBitMap* _bit_map;
1345 CMSBitMap* _mut;
1346 OopTaskQueue* _work_queue;
1347 CMSMarkStack* _overflow_stack;
1348 bool _yield;
1349 int _skip_bits;
1350 HeapWord* _finger;
1351 HeapWord* _threshold;
1352 CMSConcMarkingTask* _task;
1353 public:
1354 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1355 MemRegion span,
1356 CMSBitMap* bit_map,
1357 OopTaskQueue* work_queue,
1358 CMSMarkStack* overflow_stack,
1359 bool should_yield);
1360 bool do_bit(size_t offset);
1361 inline void do_yield_check();
1362
1363 private:
1364 void scan_oops_in_oop(HeapWord* ptr);
1365 void do_yield_work();
1366 bool get_work_from_overflow_stack();
1367 };
1368
1369 // The following closures are used to do certain kinds of verification of
1370 // CMS marking.
1371 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1372 CMSCollector* _collector;
1373 MemRegion _span;
1374 CMSBitMap* _verification_bm;
1375 CMSBitMap* _cms_bm;
1376 CMSMarkStack* _mark_stack;
1377 protected:
1378 void do_oop(oop p);
1379 template <class T> inline void do_oop_work(T *p) {
1380 oop obj = oopDesc::load_decode_heap_oop(p);
1381 do_oop(obj);
1382 }
1383 public:
1384 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1385 MemRegion span,
1386 CMSBitMap* verification_bm,
1387 CMSBitMap* cms_bm,
1388 CMSMarkStack* mark_stack);
1389 void do_oop(oop* p);
1390 void do_oop(narrowOop* p);
1391
1392 // Deal with a stack overflow condition
1393 void handle_stack_overflow(HeapWord* lost);
1394 };
1395
1396 class MarkFromRootsVerifyClosure: public BitMapClosure {
1397 CMSCollector* _collector;
1398 MemRegion _span;
1399 CMSBitMap* _verification_bm;
1400 CMSBitMap* _cms_bm;
1401 CMSMarkStack* _mark_stack;
1402 HeapWord* _finger;
1403 PushAndMarkVerifyClosure _pam_verify_closure;
1404 public:
1405 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1406 CMSBitMap* verification_bm,
1407 CMSBitMap* cms_bm,
1408 CMSMarkStack* mark_stack);
1409 bool do_bit(size_t offset);
1410 void reset(HeapWord* addr);
1411 };
1412
1413
1414 // This closure is used to check that a certain set of bits is
1415 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1416 class FalseBitMapClosure: public BitMapClosure {
1417 public:
1418 bool do_bit(size_t offset) {
1419 guarantee(false, "Should not have a 1 bit");
1420 return true;
1421 }
1422 };
1423
1424 // A version of ObjectClosure with "memory" (see _previous_address below)
1425 class UpwardsObjectClosure: public BoolObjectClosure {
1426 HeapWord* _previous_address;
1427 public:
1428 UpwardsObjectClosure() : _previous_address(NULL) { }
1429 void set_previous(HeapWord* addr) { _previous_address = addr; }
1430 HeapWord* previous() { return _previous_address; }
1431 // A return value of "true" can be used by the caller to decide
1432 // if this object's end should *NOT* be recorded in
1433 // _previous_address above.
1434 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1435 };
1436
1437 // This closure is used during the second checkpointing phase
1438 // to rescan the marked objects on the dirty cards in the mod
1439 // union table and the card table proper. It's invoked via
1440 // MarkFromDirtyCardsClosure below. It uses either
1441 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1442 // declared in genOopClosures.hpp to accomplish some of its work.
1443 // In the parallel case the bitMap is shared, so access to
1444 // it needs to be suitably synchronized for updates by embedded
1445 // closures that update it; however, this closure itself only
1446 // reads the bit_map and because it is idempotent, is immune to
1447 // reading stale values.
1448 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1449 #ifdef ASSERT
1450 CMSCollector* _collector;
1451 MemRegion _span;
1452 union {
1453 CMSMarkStack* _mark_stack;
1454 OopTaskQueue* _work_queue;
1455 };
1456 #endif // ASSERT
1457 bool _parallel;
1458 CMSBitMap* _bit_map;
1459 union {
1460 MarkRefsIntoAndScanClosure* _scan_closure;
1461 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1462 };
1463
1464 public:
1465 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1466 MemRegion span,
1467 ReferenceProcessor* rp,
1468 CMSBitMap* bit_map,
1469 CMSMarkStack* mark_stack,
1470 MarkRefsIntoAndScanClosure* cl):
1471 #ifdef ASSERT
1472 _collector(collector),
1473 _span(span),
1474 _mark_stack(mark_stack),
1475 #endif // ASSERT
1476 _parallel(false),
1477 _bit_map(bit_map),
1478 _scan_closure(cl) { }
1479
1480 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1481 MemRegion span,
1482 ReferenceProcessor* rp,
1483 CMSBitMap* bit_map,
1484 OopTaskQueue* work_queue,
1485 Par_MarkRefsIntoAndScanClosure* cl):
1486 #ifdef ASSERT
1487 _collector(collector),
1488 _span(span),
1489 _work_queue(work_queue),
1490 #endif // ASSERT
1491 _parallel(true),
1492 _bit_map(bit_map),
1493 _par_scan_closure(cl) { }
1494
1495 bool do_object_b(oop obj) {
1496 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1497 return false;
1498 }
1499 bool do_object_bm(oop p, MemRegion mr);
1500 };
1501
1502 // This closure is used during the second checkpointing phase
1503 // to rescan the marked objects on the dirty cards in the mod
1504 // union table and the card table proper. It invokes
1505 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1506 // In the parallel case, the bit map is shared and requires
1507 // synchronized access.
1508 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1509 CompactibleFreeListSpace* _space;
1510 ScanMarkedObjectsAgainClosure _scan_cl;
1511 size_t _num_dirty_cards;
1512
1513 public:
1514 MarkFromDirtyCardsClosure(CMSCollector* collector,
1515 MemRegion span,
1516 CompactibleFreeListSpace* space,
1517 CMSBitMap* bit_map,
1518 CMSMarkStack* mark_stack,
1519 MarkRefsIntoAndScanClosure* cl):
1520 _space(space),
1521 _num_dirty_cards(0),
1522 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1523 mark_stack, cl) { }
1524
1525 MarkFromDirtyCardsClosure(CMSCollector* collector,
1526 MemRegion span,
1527 CompactibleFreeListSpace* space,
1528 CMSBitMap* bit_map,
1529 OopTaskQueue* work_queue,
1530 Par_MarkRefsIntoAndScanClosure* cl):
1531 _space(space),
1532 _num_dirty_cards(0),
1533 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1534 work_queue, cl) { }
1535
1536 void do_MemRegion(MemRegion mr);
1537 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1538 size_t num_dirty_cards() { return _num_dirty_cards; }
1539 };
1540
1541 // This closure is used in the non-product build to check
1542 // that there are no MemRegions with a certain property.
1543 class FalseMemRegionClosure: public MemRegionClosure {
1544 void do_MemRegion(MemRegion mr) {
1545 guarantee(!mr.is_empty(), "Shouldn't be empty");
1546 guarantee(false, "Should never be here");
1547 }
1548 };
1549
1550 // This closure is used during the precleaning phase
1551 // to "carefully" rescan marked objects on dirty cards.
1552 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1553 // to accomplish some of its work.
1554 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1555 CMSCollector* _collector;
1556 MemRegion _span;
1557 bool _yield;
1558 Mutex* _freelistLock;
1559 CMSBitMap* _bitMap;
1560 CMSMarkStack* _markStack;
1561 MarkRefsIntoAndScanClosure* _scanningClosure;
1562
1563 public:
1564 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1565 MemRegion span,
1566 CMSBitMap* bitMap,
1567 CMSMarkStack* markStack,
1568 MarkRefsIntoAndScanClosure* cl,
1569 bool should_yield):
1570 _collector(collector),
1571 _span(span),
1572 _yield(should_yield),
1573 _bitMap(bitMap),
1574 _markStack(markStack),
1575 _scanningClosure(cl) {
1576 }
1577
1578 void do_object(oop p) {
1579 guarantee(false, "call do_object_careful instead");
1580 }
1581
1582 size_t do_object_careful(oop p) {
1583 guarantee(false, "Unexpected caller");
1584 return 0;
1585 }
1586
1587 size_t do_object_careful_m(oop p, MemRegion mr);
1588
1589 void setFreelistLock(Mutex* m) {
1590 _freelistLock = m;
1591 _scanningClosure->set_freelistLock(m);
1592 }
1593
1594 private:
1595 inline bool do_yield_check();
1596
1597 void do_yield_work();
1598 };
1599
1600 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1601 CMSCollector* _collector;
1602 MemRegion _span;
1603 bool _yield;
1604 CMSBitMap* _bit_map;
1605 CMSMarkStack* _mark_stack;
1606 PushAndMarkClosure* _scanning_closure;
1607 unsigned int _before_count;
1608
1609 public:
1610 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1611 MemRegion span,
1612 CMSBitMap* bit_map,
1613 CMSMarkStack* mark_stack,
1614 PushAndMarkClosure* cl,
1615 unsigned int before_count,
1616 bool should_yield):
1617 _collector(collector),
1618 _span(span),
1619 _yield(should_yield),
1620 _bit_map(bit_map),
1621 _mark_stack(mark_stack),
1622 _scanning_closure(cl),
1623 _before_count(before_count)
1624 { }
1625
1626 void do_object(oop p) {
1627 guarantee(false, "call do_object_careful instead");
1628 }
1629
1630 size_t do_object_careful(oop p);
1631
1632 size_t do_object_careful_m(oop p, MemRegion mr) {
1633 guarantee(false, "Unexpected caller");
1634 return 0;
1635 }
1636
1637 private:
1638 inline void do_yield_check();
1639 void do_yield_work();
1640 };
1641
1642 // This closure is used to accomplish the sweeping work
1643 // after the second checkpoint but before the concurrent reset
1644 // phase.
1645 //
1646 // Terminology
1647 // left hand chunk (LHC) - block of one or more chunks currently being
1648 // coalesced. The LHC is available for coalescing with a new chunk.
1649 // right hand chunk (RHC) - block that is currently being swept that is
1650 // free or garbage that can be coalesced with the LHC.
1651 // _inFreeRange is true if there is currently a LHC
1652 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1653 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1654 // _freeFinger is the address of the current LHC
1655 class SweepClosure: public BlkClosureCareful {
1656 CMSCollector* _collector; // collector doing the work
1657 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1658 CompactibleFreeListSpace* _sp; // Space being swept
1659 HeapWord* _limit;// the address at or above which the sweep should stop
1660 // because we do not expect newly garbage blocks
1661 // eligible for sweeping past that address.
1662 Mutex* _freelistLock; // Free list lock (in space)
1663 CMSBitMap* _bitMap; // Marking bit map (in
1664 // generation)
1665 bool _inFreeRange; // Indicates if we are in the
1666 // midst of a free run
1667 bool _freeRangeInFreeLists;
1668 // Often, we have just found
1669 // a free chunk and started
1670 // a new free range; we do not
1671 // eagerly remove this chunk from
1672 // the free lists unless there is
1673 // a possibility of coalescing.
1674 // When true, this flag indicates
1675 // that the _freeFinger below
1676 // points to a potentially free chunk
1677 // that may still be in the free lists
1678 bool _lastFreeRangeCoalesced;
1679 // free range contains chunks
1680 // coalesced
1681 bool _yield;
1682 // Whether sweeping should be
1683 // done with yields. For instance
1684 // when done by the foreground
1685 // collector we shouldn't yield.
1686 HeapWord* _freeFinger; // When _inFreeRange is set, the
1687 // pointer to the "left hand
1688 // chunk"
1689 size_t _freeRangeSize;
1690 // When _inFreeRange is set, this
1691 // indicates the accumulated size
1692 // of the "left hand chunk"
1693 NOT_PRODUCT(
1694 size_t _numObjectsFreed;
1695 size_t _numWordsFreed;
1696 size_t _numObjectsLive;
1697 size_t _numWordsLive;
1698 size_t _numObjectsAlreadyFree;
1699 size_t _numWordsAlreadyFree;
1700 FreeChunk* _last_fc;
1701 )
1702 private:
1703 // Code that is common to a free chunk or garbage when
1704 // encountered during sweeping.
1705 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1706 // Process a free chunk during sweeping.
1707 void do_already_free_chunk(FreeChunk *fc);
1708 // Work method called when processing an already free or a
1709 // freshly garbage chunk to do a lookahead and possibly a
1710 // preemptive flush if crossing over _limit.
1711 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1712 // Process a garbage chunk during sweeping.
1713 size_t do_garbage_chunk(FreeChunk *fc);
1714 // Process a live chunk during sweeping.
1715 size_t do_live_chunk(FreeChunk* fc);
1716
1717 // Accessors.
1718 HeapWord* freeFinger() const { return _freeFinger; }
1719 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1720 bool inFreeRange() const { return _inFreeRange; }
1721 void set_inFreeRange(bool v) { _inFreeRange = v; }
1722 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1723 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1724 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1725 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1726
1727 // Initialize a free range.
1728 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1729 // Return this chunk to the free lists.
1730 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1731
1732 // Check if we should yield and do so when necessary.
1733 inline void do_yield_check(HeapWord* addr);
1734
1735 // Yield
1736 void do_yield_work(HeapWord* addr);
1737
1738 // Debugging/Printing
1739 void print_free_block_coalesced(FreeChunk* fc) const;
1740
1741 public:
1742 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1743 CMSBitMap* bitMap, bool should_yield);
1744 ~SweepClosure() PRODUCT_RETURN;
1745
1746 size_t do_blk_careful(HeapWord* addr);
1747 void print() const { print_on(tty); }
1748 void print_on(outputStream *st) const;
1749 };
1750
1751 // Closures related to weak references processing
1752
1753 // During CMS' weak reference processing, this is a
1754 // work-routine/closure used to complete transitive
1755 // marking of objects as live after a certain point
1756 // in which an initial set has been completely accumulated.
1757 // This closure is currently used both during the final
1758 // remark stop-world phase, as well as during the concurrent
1759 // precleaning of the discovered reference lists.
1760 class CMSDrainMarkingStackClosure: public VoidClosure {
1761 CMSCollector* _collector;
1762 MemRegion _span;
1763 CMSMarkStack* _mark_stack;
1764 CMSBitMap* _bit_map;
1765 CMSKeepAliveClosure* _keep_alive;
1766 bool _concurrent_precleaning;
1767 public:
1768 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1769 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1770 CMSKeepAliveClosure* keep_alive,
1771 bool cpc):
1772 _collector(collector),
1773 _span(span),
1774 _bit_map(bit_map),
1775 _mark_stack(mark_stack),
1776 _keep_alive(keep_alive),
1777 _concurrent_precleaning(cpc) {
1778 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1779 "Mismatch");
1780 }
1781
1782 void do_void();
1783 };
1784
1785 // A parallel version of CMSDrainMarkingStackClosure above.
1786 class CMSParDrainMarkingStackClosure: public VoidClosure {
1787 CMSCollector* _collector;
1788 MemRegion _span;
1789 OopTaskQueue* _work_queue;
1790 CMSBitMap* _bit_map;
1791 CMSInnerParMarkAndPushClosure _mark_and_push;
1792
1793 public:
1794 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1795 MemRegion span, CMSBitMap* bit_map,
1796 OopTaskQueue* work_queue):
1797 _collector(collector),
1798 _span(span),
1799 _bit_map(bit_map),
1800 _work_queue(work_queue),
1801 _mark_and_push(collector, span, bit_map, work_queue) { }
1802
1803 public:
1804 void trim_queue(uint max);
1805 void do_void();
1806 };
1807
1808 // Allow yielding or short-circuiting of reference list
1809 // precleaning work.
1810 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1811 CMSCollector* _collector;
1812 void do_yield_work();
1813 public:
1814 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1815 _collector(collector) {}
1816 virtual bool should_return();
1817 };
1818
1819
1820 // Convenience class that locks free list locks for given CMS collector
1821 class FreelistLocker: public StackObj {
1822 private:
1823 CMSCollector* _collector;
1824 public:
1825 FreelistLocker(CMSCollector* collector):
1826 _collector(collector) {
1827 _collector->getFreelistLocks();
1828 }
1829
1830 ~FreelistLocker() {
1831 _collector->releaseFreelistLocks();
1832 }
1833 };
1834
1835 // Mark all dead objects in a given space.
1836 class MarkDeadObjectsClosure: public BlkClosure {
1837 const CMSCollector* _collector;
1838 const CompactibleFreeListSpace* _sp;
1839 CMSBitMap* _live_bit_map;
1840 CMSBitMap* _dead_bit_map;
1841 public:
1842 MarkDeadObjectsClosure(const CMSCollector* collector,
1843 const CompactibleFreeListSpace* sp,
1844 CMSBitMap *live_bit_map,
1845 CMSBitMap *dead_bit_map) :
1846 _collector(collector),
1847 _sp(sp),
1848 _live_bit_map(live_bit_map),
1849 _dead_bit_map(dead_bit_map) {}
1850 size_t do_blk(HeapWord* addr);
1851 };
1852
1853 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1854
1855 public:
1856 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1857 };
1858
1859
1860 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP