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_duration_per_mb;
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 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
420 size_t cms_allocated() const { return _cms_allocated; }
421
422 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
423
424 // Seconds since the last background cms cycle began or ended.
425 double cms_time_since_begin() const;
426 double cms_time_since_end() const;
427
428 // Higher level statistics--caller must check that valid() returns true before
429 // calling.
430
431 // Returns bytes promoted per second of wall clock time.
432 double promotion_rate() const;
433
434 // Returns bytes directly allocated per second of wall clock time.
435 double cms_allocation_rate() const;
436
437 // Rate at which space in the cms generation is being consumed (sum of the
438 // above two).
439 double cms_consumption_rate() const;
440
441 // Returns an estimate of the number of seconds until the cms generation will
442 // fill up, assuming no collection work is done.
443 double time_until_cms_gen_full() const;
444
445 // Returns an estimate of the number of seconds remaining until
446 // the cms generation collection should start.
447 double time_until_cms_start() const;
448
449 // End of higher level statistics.
450
451 // Debugging.
452 void print_on(outputStream* st) const PRODUCT_RETURN;
453 void print() const { print_on(gclog_or_tty); }
454 };
455
456 // A closure related to weak references processing which
457 // we embed in the CMSCollector, since we need to pass
458 // it to the reference processor for secondary filtering
459 // of references based on reachability of referent;
460 // see role of _is_alive_non_header closure in the
461 // ReferenceProcessor class.
462 // For objects in the CMS generation, this closure checks
463 // if the object is "live" (reachable). Used in weak
464 // reference processing.
465 class CMSIsAliveClosure: public BoolObjectClosure {
466 const MemRegion _span;
467 const CMSBitMap* _bit_map;
468
469 friend class CMSCollector;
470 public:
471 CMSIsAliveClosure(MemRegion span,
472 CMSBitMap* bit_map):
473 _span(span),
474 _bit_map(bit_map) {
475 assert(!span.is_empty(), "Empty span could spell trouble");
476 }
477
478 bool do_object_b(oop obj);
479 };
480
481
482 // Implements AbstractRefProcTaskExecutor for CMS.
483 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
484 public:
485
486 CMSRefProcTaskExecutor(CMSCollector& collector)
487 : _collector(collector)
488 { }
489
490 // Executes a task using worker threads.
491 virtual void execute(ProcessTask& task);
492 virtual void execute(EnqueueTask& task);
493 private:
494 CMSCollector& _collector;
495 };
496
497
498 class CMSCollector: public CHeapObj<mtGC> {
499 friend class VMStructs;
500 friend class ConcurrentMarkSweepThread;
501 friend class ConcurrentMarkSweepGeneration;
502 friend class CompactibleFreeListSpace;
503 friend class CMSParMarkTask;
504 friend class CMSParInitialMarkTask;
505 friend class CMSParRemarkTask;
506 friend class CMSConcMarkingTask;
507 friend class CMSRefProcTaskProxy;
508 friend class CMSRefProcTaskExecutor;
509 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
510 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
511 friend class PushOrMarkClosure; // to access _restart_addr
512 friend class Par_PushOrMarkClosure; // to access _restart_addr
513 friend class MarkFromRootsClosure; // -- ditto --
514 // ... and for clearing cards
515 friend class Par_MarkFromRootsClosure; // to access _restart_addr
516 // ... and for clearing cards
517 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
518 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
519 friend class PushAndMarkVerifyClosure; // -- ditto --
520 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
521 friend class PushAndMarkClosure; // -- ditto --
522 friend class Par_PushAndMarkClosure; // -- ditto --
523 friend class CMSKeepAliveClosure; // -- ditto --
524 friend class CMSDrainMarkingStackClosure; // -- ditto --
525 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
526 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
527 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
528 friend class VM_CMS_Operation;
529 friend class VM_CMS_Initial_Mark;
530 friend class VM_CMS_Final_Remark;
531 friend class TraceCMSMemoryManagerStats;
532
533 private:
534 jlong _time_of_last_gc;
535 void update_time_of_last_gc(jlong now) {
536 _time_of_last_gc = now;
537 }
538
539 OopTaskQueueSet* _task_queues;
540
541 // Overflow list of grey objects, threaded through mark-word
542 // Manipulated with CAS in the parallel/multi-threaded case.
543 oop _overflow_list;
544 // The following array-pair keeps track of mark words
545 // displaced for accommodating overflow list above.
546 // This code will likely be revisited under RFE#4922830.
547 Stack<oop, mtGC> _preserved_oop_stack;
548 Stack<markOop, mtGC> _preserved_mark_stack;
549
550 int* _hash_seed;
551
552 // In support of multi-threaded concurrent phases
553 YieldingFlexibleWorkGang* _conc_workers;
554
555 // Performance Counters
556 CollectorCounters* _gc_counters;
557
558 // Initialization Errors
559 bool _completed_initialization;
560
561 // In support of ExplicitGCInvokesConcurrent
562 static bool _full_gc_requested;
563 static GCCause::Cause _full_gc_cause;
564 unsigned int _collection_count_start;
565
566 // Should we unload classes this concurrent cycle?
567 bool _should_unload_classes;
568 unsigned int _concurrent_cycles_since_last_unload;
569 unsigned int concurrent_cycles_since_last_unload() const {
570 return _concurrent_cycles_since_last_unload;
571 }
572 // Did we (allow) unload classes in the previous concurrent cycle?
573 bool unloaded_classes_last_cycle() const {
574 return concurrent_cycles_since_last_unload() == 0;
575 }
576 // Root scanning options for perm gen
577 int _roots_scanning_options;
578 int roots_scanning_options() const { return _roots_scanning_options; }
579 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
580 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
581
582 // Verification support
583 CMSBitMap _verification_mark_bm;
584 void verify_after_remark_work_1();
585 void verify_after_remark_work_2();
586
587 // True if any verification flag is on.
588 bool _verifying;
589 bool verifying() const { return _verifying; }
590 void set_verifying(bool v) { _verifying = v; }
591
592 // Collector policy
593 ConcurrentMarkSweepPolicy* _collector_policy;
594 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
595
596 void set_did_compact(bool v);
597
598 // XXX Move these to CMSStats ??? FIX ME !!!
599 elapsedTimer _inter_sweep_timer; // Time between sweeps
600 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
601 // Padded decaying average estimates of the above
602 AdaptivePaddedAverage _inter_sweep_estimate;
603 AdaptivePaddedAverage _intra_sweep_estimate;
604
605 CMSTracer* _gc_tracer_cm;
606 ConcurrentGCTimer* _gc_timer_cm;
607
608 bool _cms_start_registered;
609
610 GCHeapSummary _last_heap_summary;
611 MetaspaceSummary _last_metaspace_summary;
612
613 void register_foreground_gc_start(GCCause::Cause cause);
614 void register_gc_start(GCCause::Cause cause);
615 void register_gc_end();
616 void save_heap_summary();
617 void report_heap_summary(GCWhen::Type when);
618
619 protected:
620 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
621 MemRegion _span; // Span covering above two
622 CardTableRS* _ct; // Card table
623
624 // CMS marking support structures
625 CMSBitMap _markBitMap;
626 CMSBitMap _modUnionTable;
627 CMSMarkStack _markStack;
628
629 HeapWord* _restart_addr; // In support of marking stack overflow
630 void lower_restart_addr(HeapWord* low);
631
632 // Counters in support of marking stack / work queue overflow handling:
633 // a non-zero value indicates certain types of overflow events during
634 // the current CMS cycle and could lead to stack resizing efforts at
635 // an opportune future time.
636 size_t _ser_pmc_preclean_ovflw;
637 size_t _ser_pmc_remark_ovflw;
638 size_t _par_pmc_remark_ovflw;
639 size_t _ser_kac_preclean_ovflw;
640 size_t _ser_kac_ovflw;
641 size_t _par_kac_ovflw;
642 NOT_PRODUCT(ssize_t _num_par_pushes;)
643
644 // ("Weak") Reference processing support.
645 ReferenceProcessor* _ref_processor;
646 CMSIsAliveClosure _is_alive_closure;
647 // Keep this textually after _markBitMap and _span; c'tor dependency.
648
649 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
650 ModUnionClosure _modUnionClosure;
651 ModUnionClosurePar _modUnionClosurePar;
652
653 // CMS abstract state machine
654 // initial_state: Idling
655 // next_state(Idling) = {Marking}
656 // next_state(Marking) = {Precleaning, Sweeping}
657 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
658 // next_state(AbortablePreclean) = {FinalMarking}
659 // next_state(FinalMarking) = {Sweeping}
660 // next_state(Sweeping) = {Resizing}
661 // next_state(Resizing) = {Resetting}
662 // next_state(Resetting) = {Idling}
663 // The numeric values below are chosen so that:
664 // . _collectorState <= Idling == post-sweep && pre-mark
665 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
666 // precleaning || abortablePrecleanb
667 public:
668 enum CollectorState {
669 Resizing = 0,
670 Resetting = 1,
671 Idling = 2,
672 InitialMarking = 3,
673 Marking = 4,
674 Precleaning = 5,
675 AbortablePreclean = 6,
676 FinalMarking = 7,
677 Sweeping = 8
678 };
679 protected:
680 static CollectorState _collectorState;
681
682 // State related to prologue/epilogue invocation for my generations
683 bool _between_prologue_and_epilogue;
684
685 // Signaling/State related to coordination between fore- and background GC
686 // Note: When the baton has been passed from background GC to foreground GC,
687 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
688 static bool _foregroundGCIsActive; // true iff foreground collector is active or
689 // wants to go active
690 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
691 // yet passed the baton to the foreground GC
692
693 // Support for CMSScheduleRemark (abortable preclean)
694 bool _abort_preclean;
695 bool _start_sampling;
696
697 int _numYields;
698 size_t _numDirtyCards;
699 size_t _sweep_count;
700 // Number of full gc's since the last concurrent gc.
701 uint _full_gcs_since_conc_gc;
702
703 // Occupancy used for bootstrapping stats
704 double _bootstrap_occupancy;
705
706 // Timer
707 elapsedTimer _timer;
708
709 // Timing, allocation and promotion statistics, used for scheduling.
710 CMSStats _stats;
711
712 enum CMS_op_type {
713 CMS_op_checkpointRootsInitial,
714 CMS_op_checkpointRootsFinal
715 };
716
717 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
718 bool stop_world_and_do(CMS_op_type op);
719
720 OopTaskQueueSet* task_queues() { return _task_queues; }
721 int* hash_seed(int i) { return &_hash_seed[i]; }
722 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
723
724 // Support for parallelizing Eden rescan in CMS remark phase
725 void sample_eden(); // ... sample Eden space top
726
727 private:
728 // Support for parallelizing young gen rescan in CMS remark phase
729 Generation* _young_gen; // the younger gen
730 HeapWord** _top_addr; // ... Top of Eden
731 HeapWord** _end_addr; // ... End of Eden
732 Mutex* _eden_chunk_lock;
733 HeapWord** _eden_chunk_array; // ... Eden partitioning array
734 size_t _eden_chunk_index; // ... top (exclusive) of array
735 size_t _eden_chunk_capacity; // ... max entries in array
736
737 // Support for parallelizing survivor space rescan
738 HeapWord** _survivor_chunk_array;
739 size_t _survivor_chunk_index;
740 size_t _survivor_chunk_capacity;
741 size_t* _cursor;
742 ChunkArray* _survivor_plab_array;
743
744 // Support for marking stack overflow handling
745 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
746 bool par_take_from_overflow_list(size_t num,
747 OopTaskQueue* to_work_q,
748 int no_of_gc_threads);
749 void push_on_overflow_list(oop p);
750 void par_push_on_overflow_list(oop p);
751 // The following is, obviously, not, in general, "MT-stable"
752 bool overflow_list_is_empty() const;
753
754 void preserve_mark_if_necessary(oop p);
755 void par_preserve_mark_if_necessary(oop p);
756 void preserve_mark_work(oop p, markOop m);
757 void restore_preserved_marks_if_any();
758 NOT_PRODUCT(bool no_preserved_marks() const;)
759 // In support of testing overflow code
760 NOT_PRODUCT(int _overflow_counter;)
761 NOT_PRODUCT(bool simulate_overflow();) // Sequential
762 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
763
764 // CMS work methods
765 void checkpointRootsInitialWork(bool asynch); // Initial checkpoint work
766
767 // A return value of false indicates failure due to stack overflow
768 bool markFromRootsWork(bool asynch); // Concurrent marking work
769
770 public: // FIX ME!!! only for testing
771 bool do_marking_st(bool asynch); // Single-threaded marking
772 bool do_marking_mt(bool asynch); // Multi-threaded marking
773
774 private:
775
776 // Concurrent precleaning work
777 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
778 ScanMarkedObjectsAgainCarefullyClosure* cl);
779 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
780 ScanMarkedObjectsAgainCarefullyClosure* cl);
781 // Does precleaning work, returning a quantity indicative of
782 // the amount of "useful work" done.
783 size_t preclean_work(bool clean_refs, bool clean_survivors);
784 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
785 void abortable_preclean(); // Preclean while looking for possible abort
786 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
787 // Helper function for above; merge-sorts the per-thread plab samples
788 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
789 // Resets (i.e. clears) the per-thread plab sample vectors
790 void reset_survivor_plab_arrays();
791
792 // Final (second) checkpoint work
793 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
794 bool init_mark_was_synchronous);
795 // Work routine for parallel version of remark
796 void do_remark_parallel();
797 // Work routine for non-parallel version of remark
798 void do_remark_non_parallel();
799 // Reference processing work routine (during second checkpoint)
800 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
801
802 // Concurrent sweeping work
803 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
804
805 // (Concurrent) resetting of support data structures
806 void reset(bool asynch);
807
808 // Clear _expansion_cause fields of constituent generations
809 void clear_expansion_cause();
810
811 // An auxiliary method used to record the ends of
812 // used regions of each generation to limit the extent of sweep
813 void save_sweep_limits();
814
815 // A work method used by foreground collection to determine
816 // what type of collection (compacting or not, continuing or fresh)
817 // it should do.
818 void decide_foreground_collection_type(bool clear_all_soft_refs,
819 bool* should_compact, bool* should_start_over);
820
821 // A work method used by the foreground collector to do
822 // a mark-sweep-compact.
823 void do_compaction_work(bool clear_all_soft_refs);
824
825 // A work method used by the foreground collector to do
826 // a mark-sweep, after taking over from a possibly on-going
827 // concurrent mark-sweep collection.
828 void do_mark_sweep_work(bool clear_all_soft_refs,
829 CollectorState first_state, bool should_start_over);
830
831 // Work methods for reporting concurrent mode interruption or failure
832 bool is_external_interruption();
833 void report_concurrent_mode_interruption();
834
835 // If the background GC is active, acquire control from the background
836 // GC and do the collection.
837 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
838
839 // For synchronizing passing of control from background to foreground
840 // GC. waitForForegroundGC() is called by the background
841 // collector. It if had to wait for a foreground collection,
842 // it returns true and the background collection should assume
843 // that the collection was finished by the foreground
844 // collector.
845 bool waitForForegroundGC();
846
847 size_t block_size_using_printezis_bits(HeapWord* addr) const;
848 size_t block_size_if_printezis_bits(HeapWord* addr) const;
849 HeapWord* next_card_start_after_block(HeapWord* addr) const;
850
851 void setup_cms_unloading_and_verification_state();
852 public:
853 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
854 CardTableRS* ct,
855 ConcurrentMarkSweepPolicy* cp);
856 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
857
858 ReferenceProcessor* ref_processor() { return _ref_processor; }
859 void ref_processor_init();
860
861 Mutex* bitMapLock() const { return _markBitMap.lock(); }
862 static CollectorState abstract_state() { return _collectorState; }
863
864 bool should_abort_preclean() const; // Whether preclean should be aborted.
865 size_t get_eden_used() const;
866 size_t get_eden_capacity() const;
867
868 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
869
870 // Locking checks
871 NOT_PRODUCT(static bool have_cms_token();)
872
873 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
874 bool shouldConcurrentCollect();
875
876 void collect(bool full,
877 bool clear_all_soft_refs,
878 size_t size,
879 bool tlab);
880 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
881 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
882
883 // In support of ExplicitGCInvokesConcurrent
884 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
885 // Should we unload classes in a particular concurrent cycle?
886 bool should_unload_classes() const {
887 return _should_unload_classes;
888 }
889 void update_should_unload_classes();
890
891 void direct_allocated(HeapWord* start, size_t size);
892
893 // Object is dead if not marked and current phase is sweeping.
894 bool is_dead_obj(oop obj) const;
895
896 // After a promotion (of "start"), do any necessary marking.
897 // If "par", then it's being done by a parallel GC thread.
898 // The last two args indicate if we need precise marking
899 // and if so the size of the object so it can be dirtied
900 // in its entirety.
901 void promoted(bool par, HeapWord* start,
902 bool is_obj_array, size_t obj_size);
903
904 void getFreelistLocks() const;
905 void releaseFreelistLocks() const;
906 bool haveFreelistLocks() const;
907
908 // Adjust size of underlying generation
909 void compute_new_size();
910
911 // GC prologue and epilogue
912 void gc_prologue(bool full);
913 void gc_epilogue(bool full);
914
915 jlong time_of_last_gc(jlong now) {
916 if (_collectorState <= Idling) {
917 // gc not in progress
918 return _time_of_last_gc;
919 } else {
920 // collection in progress
921 return now;
922 }
923 }
924
925 // Support for parallel remark of survivor space
926 void* get_data_recorder(int thr_num);
927 void sample_eden_chunk();
928
929 CMSBitMap* markBitMap() { return &_markBitMap; }
930 void directAllocated(HeapWord* start, size_t size);
931
932 // Main CMS steps and related support
933 void checkpointRootsInitial(bool asynch);
934 bool markFromRoots(bool asynch); // a return value of false indicates failure
935 // due to stack overflow
936 void preclean();
937 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
938 bool init_mark_was_synchronous);
939 void sweep(bool asynch);
940
941 // Check that the currently executing thread is the expected
942 // one (foreground collector or background collector).
943 static void check_correct_thread_executing() PRODUCT_RETURN;
944 // XXXPERM void print_statistics() PRODUCT_RETURN;
945
946 bool is_cms_reachable(HeapWord* addr);
947
948 // Performance Counter Support
949 CollectorCounters* counters() { return _gc_counters; }
950
951 // Timer stuff
952 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
953 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
954 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
955 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
956
957 int yields() { return _numYields; }
958 void resetYields() { _numYields = 0; }
959 void incrementYields() { _numYields++; }
960 void resetNumDirtyCards() { _numDirtyCards = 0; }
961 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
962 size_t numDirtyCards() { return _numDirtyCards; }
963
964 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
965 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
966 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
967 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
968 size_t sweep_count() const { return _sweep_count; }
969 void increment_sweep_count() { _sweep_count++; }
970
971 // Timers/stats for gc scheduling and incremental mode pacing.
972 CMSStats& stats() { return _stats; }
973
974 // Adaptive size policy
975 AdaptiveSizePolicy* size_policy();
976
977 static void print_on_error(outputStream* st);
978
979 // Debugging
980 void verify();
981 bool verify_after_remark(bool silent = VerifySilently);
982 void verify_ok_to_terminate() const PRODUCT_RETURN;
983 void verify_work_stacks_empty() const PRODUCT_RETURN;
984 void verify_overflow_empty() const PRODUCT_RETURN;
985
986 // Convenience methods in support of debugging
987 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
988 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
989
990 // Accessors
991 CMSMarkStack* verification_mark_stack() { return &_markStack; }
992 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
993
994 // Initialization errors
995 bool completed_initialization() { return _completed_initialization; }
996
997 void print_eden_and_survivor_chunk_arrays();
998 };
999
1000 class CMSExpansionCause : public AllStatic {
1001 public:
1002 enum Cause {
1003 _no_expansion,
1004 _satisfy_free_ratio,
1005 _satisfy_promotion,
1006 _satisfy_allocation,
1007 _allocate_par_lab,
1008 _allocate_par_spooling_space,
1009 _adaptive_size_policy
1010 };
1011 // Return a string describing the cause of the expansion.
1012 static const char* to_string(CMSExpansionCause::Cause cause);
1013 };
1014
1015 class ConcurrentMarkSweepGeneration: public CardGeneration {
1016 friend class VMStructs;
1017 friend class ConcurrentMarkSweepThread;
1018 friend class ConcurrentMarkSweep;
1019 friend class CMSCollector;
1020 protected:
1021 static CMSCollector* _collector; // the collector that collects us
1022 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1023
1024 // Performance Counters
1025 GenerationCounters* _gen_counters;
1026 GSpaceCounters* _space_counters;
1027
1028 // Words directly allocated, used by CMSStats.
1029 size_t _direct_allocated_words;
1030
1031 // Non-product stat counters
1032 NOT_PRODUCT(
1033 size_t _numObjectsPromoted;
1034 size_t _numWordsPromoted;
1035 size_t _numObjectsAllocated;
1036 size_t _numWordsAllocated;
1037 )
1038
1039 // Used for sizing decisions
1040 bool _incremental_collection_failed;
1041 bool incremental_collection_failed() {
1042 return _incremental_collection_failed;
1043 }
1044 void set_incremental_collection_failed() {
1045 _incremental_collection_failed = true;
1046 }
1047 void clear_incremental_collection_failed() {
1048 _incremental_collection_failed = false;
1049 }
1050
1051 // accessors
1052 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1053 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1054
1055 private:
1056 // For parallel young-gen GC support.
1057 CMSParGCThreadState** _par_gc_thread_states;
1058
1059 // Reason generation was expanded
1060 CMSExpansionCause::Cause _expansion_cause;
1061
1062 // In support of MinChunkSize being larger than min object size
1063 const double _dilatation_factor;
1064
1065 enum CollectionTypes {
1066 Concurrent_collection_type = 0,
1067 MS_foreground_collection_type = 1,
1068 MSC_foreground_collection_type = 2,
1069 Unknown_collection_type = 3
1070 };
1071
1072 CollectionTypes _debug_collection_type;
1073
1074 // True if a compacting collection was done.
1075 bool _did_compact;
1076 bool did_compact() { return _did_compact; }
1077
1078 // Fraction of current occupancy at which to start a CMS collection which
1079 // will collect this generation (at least).
1080 double _initiating_occupancy;
1081
1082 protected:
1083 // Shrink generation by specified size (returns false if unable to shrink)
1084 void shrink_free_list_by(size_t bytes);
1085
1086 // Update statistics for GC
1087 virtual void update_gc_stats(int level, bool full);
1088
1089 // Maximum available space in the generation (including uncommitted)
1090 // space.
1091 size_t max_available() const;
1092
1093 // getter and initializer for _initiating_occupancy field.
1094 double initiating_occupancy() const { return _initiating_occupancy; }
1095 void init_initiating_occupancy(intx io, uintx tr);
1096
1097 public:
1098 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1099 int level, CardTableRS* ct,
1100 bool use_adaptive_freelists,
1101 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1102
1103 // Accessors
1104 CMSCollector* collector() const { return _collector; }
1105 static void set_collector(CMSCollector* collector) {
1106 assert(_collector == NULL, "already set");
1107 _collector = collector;
1108 }
1109 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1110
1111 Mutex* freelistLock() const;
1112
1113 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1114
1115 void set_did_compact(bool v) { _did_compact = v; }
1116
1117 bool refs_discovery_is_atomic() const { return false; }
1118 bool refs_discovery_is_mt() const {
1119 // Note: CMS does MT-discovery during the parallel-remark
1120 // phases. Use ReferenceProcessorMTMutator to make refs
1121 // discovery MT-safe during such phases or other parallel
1122 // discovery phases in the future. This may all go away
1123 // if/when we decide that refs discovery is sufficiently
1124 // rare that the cost of the CAS's involved is in the
1125 // noise. That's a measurement that should be done, and
1126 // the code simplified if that turns out to be the case.
1127 return ConcGCThreads > 1;
1128 }
1129
1130 // Override
1131 virtual void ref_processor_init();
1132
1133 // Grow generation by specified size (returns false if unable to grow)
1134 bool grow_by(size_t bytes);
1135 // Grow generation to reserved size.
1136 bool grow_to_reserved();
1137
1138 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1139
1140 // Space enquiries
1141 size_t capacity() const;
1142 size_t used() const;
1143 size_t free() const;
1144 double occupancy() const { return ((double)used())/((double)capacity()); }
1145 size_t contiguous_available() const;
1146 size_t unsafe_max_alloc_nogc() const;
1147
1148 // over-rides
1149 MemRegion used_region() const;
1150 MemRegion used_region_at_save_marks() const;
1151
1152 // Does a "full" (forced) collection invoked on this generation collect
1153 // all younger generations as well? Note that the second conjunct is a
1154 // hack to allow the collection of the younger gen first if the flag is
1155 // set.
1156 virtual bool full_collects_younger_generations() const {
1157 return UseCMSCompactAtFullCollection && !ScavengeBeforeFullGC;
1158 }
1159
1160 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1161
1162 // Support for compaction
1163 CompactibleSpace* first_compaction_space() const;
1164 // Adjust quantities in the generation affected by
1165 // the compaction.
1166 void reset_after_compaction();
1167
1168 // Allocation support
1169 HeapWord* allocate(size_t size, bool tlab);
1170 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1171 oop promote(oop obj, size_t obj_size);
1172 HeapWord* par_allocate(size_t size, bool tlab) {
1173 return allocate(size, tlab);
1174 }
1175
1176
1177 // Used by CMSStats to track direct allocation. The value is sampled and
1178 // reset after each young gen collection.
1179 size_t direct_allocated_words() const { return _direct_allocated_words; }
1180 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1181
1182 // Overrides for parallel promotion.
1183 virtual oop par_promote(int thread_num,
1184 oop obj, markOop m, size_t word_sz);
1185 // This one should not be called for CMS.
1186 virtual void par_promote_alloc_undo(int thread_num,
1187 HeapWord* obj, size_t word_sz);
1188 virtual void par_promote_alloc_done(int thread_num);
1189 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1190
1191 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1192
1193 // Inform this (non-young) generation that a promotion failure was
1194 // encountered during a collection of a younger generation that
1195 // promotes into this generation.
1196 virtual void promotion_failure_occurred();
1197
1198 bool should_collect(bool full, size_t size, bool tlab);
1199 virtual bool should_concurrent_collect() const;
1200 virtual bool is_too_full() const;
1201 void collect(bool full,
1202 bool clear_all_soft_refs,
1203 size_t size,
1204 bool tlab);
1205
1206 HeapWord* expand_and_allocate(size_t word_size,
1207 bool tlab,
1208 bool parallel = false);
1209
1210 // GC prologue and epilogue
1211 void gc_prologue(bool full);
1212 void gc_prologue_work(bool full, bool registerClosure,
1213 ModUnionClosure* modUnionClosure);
1214 void gc_epilogue(bool full);
1215 void gc_epilogue_work(bool full);
1216
1217 // Time since last GC of this generation
1218 jlong time_of_last_gc(jlong now) {
1219 return collector()->time_of_last_gc(now);
1220 }
1221 void update_time_of_last_gc(jlong now) {
1222 collector()-> update_time_of_last_gc(now);
1223 }
1224
1225 // Allocation failure
1226 void expand(size_t bytes, size_t expand_bytes,
1227 CMSExpansionCause::Cause cause);
1228 virtual bool expand(size_t bytes, size_t expand_bytes);
1229 void shrink(size_t bytes);
1230 void shrink_by(size_t bytes);
1231 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1232 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1233
1234 // Iteration support and related enquiries
1235 void save_marks();
1236 bool no_allocs_since_save_marks();
1237 void younger_refs_iterate(OopsInGenClosure* cl);
1238
1239 // Iteration support specific to CMS generations
1240 void save_sweep_limit();
1241
1242 // More iteration support
1243 virtual void oop_iterate(ExtendedOopClosure* cl);
1244 virtual void safe_object_iterate(ObjectClosure* cl);
1245 virtual void object_iterate(ObjectClosure* cl);
1246
1247 // Need to declare the full complement of closures, whether we'll
1248 // override them or not, or get message from the compiler:
1249 // oop_since_save_marks_iterate_nv hides virtual function...
1250 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1251 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1252 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1253
1254 // Smart allocation XXX -- move to CFLSpace?
1255 void setNearLargestChunk();
1256 bool isNearLargestChunk(HeapWord* addr);
1257
1258 // Get the chunk at the end of the space. Delegates to
1259 // the space.
1260 FreeChunk* find_chunk_at_end();
1261
1262 void post_compact();
1263
1264 // Debugging
1265 void prepare_for_verify();
1266 void verify();
1267 void print_statistics() PRODUCT_RETURN;
1268
1269 // Performance Counters support
1270 virtual void update_counters();
1271 virtual void update_counters(size_t used);
1272 void initialize_performance_counters();
1273 CollectorCounters* counters() { return collector()->counters(); }
1274
1275 // Support for parallel remark of survivor space
1276 void* get_data_recorder(int thr_num) {
1277 //Delegate to collector
1278 return collector()->get_data_recorder(thr_num);
1279 }
1280 void sample_eden_chunk() {
1281 //Delegate to collector
1282 return collector()->sample_eden_chunk();
1283 }
1284
1285 // Printing
1286 const char* name() const;
1287 virtual const char* short_name() const { return "CMS"; }
1288 void print() const;
1289 void printOccupancy(const char* s);
1290 bool must_be_youngest() const { return false; }
1291 bool must_be_oldest() const { return true; }
1292
1293 // Resize the generation after a compacting GC. The
1294 // generation can be treated as a contiguous space
1295 // after the compaction.
1296 virtual void compute_new_size();
1297 // Resize the generation after a non-compacting
1298 // collection.
1299 void compute_new_size_free_list();
1300
1301 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1302 void rotate_debug_collection_type();
1303 };
1304
1305 //
1306 // Closures of various sorts used by CMS to accomplish its work
1307 //
1308
1309 // This closure is used to do concurrent marking from the roots
1310 // following the first checkpoint.
1311 class MarkFromRootsClosure: public BitMapClosure {
1312 CMSCollector* _collector;
1313 MemRegion _span;
1314 CMSBitMap* _bitMap;
1315 CMSBitMap* _mut;
1316 CMSMarkStack* _markStack;
1317 bool _yield;
1318 int _skipBits;
1319 HeapWord* _finger;
1320 HeapWord* _threshold;
1321 DEBUG_ONLY(bool _verifying;)
1322
1323 public:
1324 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1325 CMSBitMap* bitMap,
1326 CMSMarkStack* markStack,
1327 bool should_yield, bool verifying = false);
1328 bool do_bit(size_t offset);
1329 void reset(HeapWord* addr);
1330 inline void do_yield_check();
1331
1332 private:
1333 void scanOopsInOop(HeapWord* ptr);
1334 void do_yield_work();
1335 };
1336
1337 // This closure is used to do concurrent multi-threaded
1338 // marking from the roots following the first checkpoint.
1339 // XXX This should really be a subclass of The serial version
1340 // above, but i have not had the time to refactor things cleanly.
1341 class Par_MarkFromRootsClosure: public BitMapClosure {
1342 CMSCollector* _collector;
1343 MemRegion _whole_span;
1344 MemRegion _span;
1345 CMSBitMap* _bit_map;
1346 CMSBitMap* _mut;
1347 OopTaskQueue* _work_queue;
1348 CMSMarkStack* _overflow_stack;
1349 bool _yield;
1350 int _skip_bits;
1351 HeapWord* _finger;
1352 HeapWord* _threshold;
1353 CMSConcMarkingTask* _task;
1354 public:
1355 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1356 MemRegion span,
1357 CMSBitMap* bit_map,
1358 OopTaskQueue* work_queue,
1359 CMSMarkStack* overflow_stack,
1360 bool should_yield);
1361 bool do_bit(size_t offset);
1362 inline void do_yield_check();
1363
1364 private:
1365 void scan_oops_in_oop(HeapWord* ptr);
1366 void do_yield_work();
1367 bool get_work_from_overflow_stack();
1368 };
1369
1370 // The following closures are used to do certain kinds of verification of
1371 // CMS marking.
1372 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1373 CMSCollector* _collector;
1374 MemRegion _span;
1375 CMSBitMap* _verification_bm;
1376 CMSBitMap* _cms_bm;
1377 CMSMarkStack* _mark_stack;
1378 protected:
1379 void do_oop(oop p);
1380 template <class T> inline void do_oop_work(T *p) {
1381 oop obj = oopDesc::load_decode_heap_oop(p);
1382 do_oop(obj);
1383 }
1384 public:
1385 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1386 MemRegion span,
1387 CMSBitMap* verification_bm,
1388 CMSBitMap* cms_bm,
1389 CMSMarkStack* mark_stack);
1390 void do_oop(oop* p);
1391 void do_oop(narrowOop* p);
1392
1393 // Deal with a stack overflow condition
1394 void handle_stack_overflow(HeapWord* lost);
1395 };
1396
1397 class MarkFromRootsVerifyClosure: public BitMapClosure {
1398 CMSCollector* _collector;
1399 MemRegion _span;
1400 CMSBitMap* _verification_bm;
1401 CMSBitMap* _cms_bm;
1402 CMSMarkStack* _mark_stack;
1403 HeapWord* _finger;
1404 PushAndMarkVerifyClosure _pam_verify_closure;
1405 public:
1406 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1407 CMSBitMap* verification_bm,
1408 CMSBitMap* cms_bm,
1409 CMSMarkStack* mark_stack);
1410 bool do_bit(size_t offset);
1411 void reset(HeapWord* addr);
1412 };
1413
1414
1415 // This closure is used to check that a certain set of bits is
1416 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1417 class FalseBitMapClosure: public BitMapClosure {
1418 public:
1419 bool do_bit(size_t offset) {
1420 guarantee(false, "Should not have a 1 bit");
1421 return true;
1422 }
1423 };
1424
1425 // A version of ObjectClosure with "memory" (see _previous_address below)
1426 class UpwardsObjectClosure: public BoolObjectClosure {
1427 HeapWord* _previous_address;
1428 public:
1429 UpwardsObjectClosure() : _previous_address(NULL) { }
1430 void set_previous(HeapWord* addr) { _previous_address = addr; }
1431 HeapWord* previous() { return _previous_address; }
1432 // A return value of "true" can be used by the caller to decide
1433 // if this object's end should *NOT* be recorded in
1434 // _previous_address above.
1435 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1436 };
1437
1438 // This closure is used during the second checkpointing phase
1439 // to rescan the marked objects on the dirty cards in the mod
1440 // union table and the card table proper. It's invoked via
1441 // MarkFromDirtyCardsClosure below. It uses either
1442 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1443 // declared in genOopClosures.hpp to accomplish some of its work.
1444 // In the parallel case the bitMap is shared, so access to
1445 // it needs to be suitably synchronized for updates by embedded
1446 // closures that update it; however, this closure itself only
1447 // reads the bit_map and because it is idempotent, is immune to
1448 // reading stale values.
1449 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1450 #ifdef ASSERT
1451 CMSCollector* _collector;
1452 MemRegion _span;
1453 union {
1454 CMSMarkStack* _mark_stack;
1455 OopTaskQueue* _work_queue;
1456 };
1457 #endif // ASSERT
1458 bool _parallel;
1459 CMSBitMap* _bit_map;
1460 union {
1461 MarkRefsIntoAndScanClosure* _scan_closure;
1462 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1463 };
1464
1465 public:
1466 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1467 MemRegion span,
1468 ReferenceProcessor* rp,
1469 CMSBitMap* bit_map,
1470 CMSMarkStack* mark_stack,
1471 MarkRefsIntoAndScanClosure* cl):
1472 #ifdef ASSERT
1473 _collector(collector),
1474 _span(span),
1475 _mark_stack(mark_stack),
1476 #endif // ASSERT
1477 _parallel(false),
1478 _bit_map(bit_map),
1479 _scan_closure(cl) { }
1480
1481 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1482 MemRegion span,
1483 ReferenceProcessor* rp,
1484 CMSBitMap* bit_map,
1485 OopTaskQueue* work_queue,
1486 Par_MarkRefsIntoAndScanClosure* cl):
1487 #ifdef ASSERT
1488 _collector(collector),
1489 _span(span),
1490 _work_queue(work_queue),
1491 #endif // ASSERT
1492 _parallel(true),
1493 _bit_map(bit_map),
1494 _par_scan_closure(cl) { }
1495
1496 bool do_object_b(oop obj) {
1497 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1498 return false;
1499 }
1500 bool do_object_bm(oop p, MemRegion mr);
1501 };
1502
1503 // This closure is used during the second checkpointing phase
1504 // to rescan the marked objects on the dirty cards in the mod
1505 // union table and the card table proper. It invokes
1506 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1507 // In the parallel case, the bit map is shared and requires
1508 // synchronized access.
1509 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1510 CompactibleFreeListSpace* _space;
1511 ScanMarkedObjectsAgainClosure _scan_cl;
1512 size_t _num_dirty_cards;
1513
1514 public:
1515 MarkFromDirtyCardsClosure(CMSCollector* collector,
1516 MemRegion span,
1517 CompactibleFreeListSpace* space,
1518 CMSBitMap* bit_map,
1519 CMSMarkStack* mark_stack,
1520 MarkRefsIntoAndScanClosure* cl):
1521 _space(space),
1522 _num_dirty_cards(0),
1523 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1524 mark_stack, cl) { }
1525
1526 MarkFromDirtyCardsClosure(CMSCollector* collector,
1527 MemRegion span,
1528 CompactibleFreeListSpace* space,
1529 CMSBitMap* bit_map,
1530 OopTaskQueue* work_queue,
1531 Par_MarkRefsIntoAndScanClosure* cl):
1532 _space(space),
1533 _num_dirty_cards(0),
1534 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1535 work_queue, cl) { }
1536
1537 void do_MemRegion(MemRegion mr);
1538 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1539 size_t num_dirty_cards() { return _num_dirty_cards; }
1540 };
1541
1542 // This closure is used in the non-product build to check
1543 // that there are no MemRegions with a certain property.
1544 class FalseMemRegionClosure: public MemRegionClosure {
1545 void do_MemRegion(MemRegion mr) {
1546 guarantee(!mr.is_empty(), "Shouldn't be empty");
1547 guarantee(false, "Should never be here");
1548 }
1549 };
1550
1551 // This closure is used during the precleaning phase
1552 // to "carefully" rescan marked objects on dirty cards.
1553 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1554 // to accomplish some of its work.
1555 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1556 CMSCollector* _collector;
1557 MemRegion _span;
1558 bool _yield;
1559 Mutex* _freelistLock;
1560 CMSBitMap* _bitMap;
1561 CMSMarkStack* _markStack;
1562 MarkRefsIntoAndScanClosure* _scanningClosure;
1563
1564 public:
1565 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1566 MemRegion span,
1567 CMSBitMap* bitMap,
1568 CMSMarkStack* markStack,
1569 MarkRefsIntoAndScanClosure* cl,
1570 bool should_yield):
1571 _collector(collector),
1572 _span(span),
1573 _yield(should_yield),
1574 _bitMap(bitMap),
1575 _markStack(markStack),
1576 _scanningClosure(cl) {
1577 }
1578
1579 void do_object(oop p) {
1580 guarantee(false, "call do_object_careful instead");
1581 }
1582
1583 size_t do_object_careful(oop p) {
1584 guarantee(false, "Unexpected caller");
1585 return 0;
1586 }
1587
1588 size_t do_object_careful_m(oop p, MemRegion mr);
1589
1590 void setFreelistLock(Mutex* m) {
1591 _freelistLock = m;
1592 _scanningClosure->set_freelistLock(m);
1593 }
1594
1595 private:
1596 inline bool do_yield_check();
1597
1598 void do_yield_work();
1599 };
1600
1601 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1602 CMSCollector* _collector;
1603 MemRegion _span;
1604 bool _yield;
1605 CMSBitMap* _bit_map;
1606 CMSMarkStack* _mark_stack;
1607 PushAndMarkClosure* _scanning_closure;
1608 unsigned int _before_count;
1609
1610 public:
1611 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1612 MemRegion span,
1613 CMSBitMap* bit_map,
1614 CMSMarkStack* mark_stack,
1615 PushAndMarkClosure* cl,
1616 unsigned int before_count,
1617 bool should_yield):
1618 _collector(collector),
1619 _span(span),
1620 _yield(should_yield),
1621 _bit_map(bit_map),
1622 _mark_stack(mark_stack),
1623 _scanning_closure(cl),
1624 _before_count(before_count)
1625 { }
1626
1627 void do_object(oop p) {
1628 guarantee(false, "call do_object_careful instead");
1629 }
1630
1631 size_t do_object_careful(oop p);
1632
1633 size_t do_object_careful_m(oop p, MemRegion mr) {
1634 guarantee(false, "Unexpected caller");
1635 return 0;
1636 }
1637
1638 private:
1639 inline void do_yield_check();
1640 void do_yield_work();
1641 };
1642
1643 // This closure is used to accomplish the sweeping work
1644 // after the second checkpoint but before the concurrent reset
1645 // phase.
1646 //
1647 // Terminology
1648 // left hand chunk (LHC) - block of one or more chunks currently being
1649 // coalesced. The LHC is available for coalescing with a new chunk.
1650 // right hand chunk (RHC) - block that is currently being swept that is
1651 // free or garbage that can be coalesced with the LHC.
1652 // _inFreeRange is true if there is currently a LHC
1653 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1654 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1655 // _freeFinger is the address of the current LHC
1656 class SweepClosure: public BlkClosureCareful {
1657 CMSCollector* _collector; // collector doing the work
1658 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1659 CompactibleFreeListSpace* _sp; // Space being swept
1660 HeapWord* _limit;// the address at or above which the sweep should stop
1661 // because we do not expect newly garbage blocks
1662 // eligible for sweeping past that address.
1663 Mutex* _freelistLock; // Free list lock (in space)
1664 CMSBitMap* _bitMap; // Marking bit map (in
1665 // generation)
1666 bool _inFreeRange; // Indicates if we are in the
1667 // midst of a free run
1668 bool _freeRangeInFreeLists;
1669 // Often, we have just found
1670 // a free chunk and started
1671 // a new free range; we do not
1672 // eagerly remove this chunk from
1673 // the free lists unless there is
1674 // a possibility of coalescing.
1675 // When true, this flag indicates
1676 // that the _freeFinger below
1677 // points to a potentially free chunk
1678 // that may still be in the free lists
1679 bool _lastFreeRangeCoalesced;
1680 // free range contains chunks
1681 // coalesced
1682 bool _yield;
1683 // Whether sweeping should be
1684 // done with yields. For instance
1685 // when done by the foreground
1686 // collector we shouldn't yield.
1687 HeapWord* _freeFinger; // When _inFreeRange is set, the
1688 // pointer to the "left hand
1689 // chunk"
1690 size_t _freeRangeSize;
1691 // When _inFreeRange is set, this
1692 // indicates the accumulated size
1693 // of the "left hand chunk"
1694 NOT_PRODUCT(
1695 size_t _numObjectsFreed;
1696 size_t _numWordsFreed;
1697 size_t _numObjectsLive;
1698 size_t _numWordsLive;
1699 size_t _numObjectsAlreadyFree;
1700 size_t _numWordsAlreadyFree;
1701 FreeChunk* _last_fc;
1702 )
1703 private:
1704 // Code that is common to a free chunk or garbage when
1705 // encountered during sweeping.
1706 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1707 // Process a free chunk during sweeping.
1708 void do_already_free_chunk(FreeChunk *fc);
1709 // Work method called when processing an already free or a
1710 // freshly garbage chunk to do a lookahead and possibly a
1711 // preemptive flush if crossing over _limit.
1712 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1713 // Process a garbage chunk during sweeping.
1714 size_t do_garbage_chunk(FreeChunk *fc);
1715 // Process a live chunk during sweeping.
1716 size_t do_live_chunk(FreeChunk* fc);
1717
1718 // Accessors.
1719 HeapWord* freeFinger() const { return _freeFinger; }
1720 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1721 bool inFreeRange() const { return _inFreeRange; }
1722 void set_inFreeRange(bool v) { _inFreeRange = v; }
1723 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1724 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1725 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1726 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1727
1728 // Initialize a free range.
1729 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1730 // Return this chunk to the free lists.
1731 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1732
1733 // Check if we should yield and do so when necessary.
1734 inline void do_yield_check(HeapWord* addr);
1735
1736 // Yield
1737 void do_yield_work(HeapWord* addr);
1738
1739 // Debugging/Printing
1740 void print_free_block_coalesced(FreeChunk* fc) const;
1741
1742 public:
1743 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1744 CMSBitMap* bitMap, bool should_yield);
1745 ~SweepClosure() PRODUCT_RETURN;
1746
1747 size_t do_blk_careful(HeapWord* addr);
1748 void print() const { print_on(tty); }
1749 void print_on(outputStream *st) const;
1750 };
1751
1752 // Closures related to weak references processing
1753
1754 // During CMS' weak reference processing, this is a
1755 // work-routine/closure used to complete transitive
1756 // marking of objects as live after a certain point
1757 // in which an initial set has been completely accumulated.
1758 // This closure is currently used both during the final
1759 // remark stop-world phase, as well as during the concurrent
1760 // precleaning of the discovered reference lists.
1761 class CMSDrainMarkingStackClosure: public VoidClosure {
1762 CMSCollector* _collector;
1763 MemRegion _span;
1764 CMSMarkStack* _mark_stack;
1765 CMSBitMap* _bit_map;
1766 CMSKeepAliveClosure* _keep_alive;
1767 bool _concurrent_precleaning;
1768 public:
1769 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1770 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1771 CMSKeepAliveClosure* keep_alive,
1772 bool cpc):
1773 _collector(collector),
1774 _span(span),
1775 _bit_map(bit_map),
1776 _mark_stack(mark_stack),
1777 _keep_alive(keep_alive),
1778 _concurrent_precleaning(cpc) {
1779 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1780 "Mismatch");
1781 }
1782
1783 void do_void();
1784 };
1785
1786 // A parallel version of CMSDrainMarkingStackClosure above.
1787 class CMSParDrainMarkingStackClosure: public VoidClosure {
1788 CMSCollector* _collector;
1789 MemRegion _span;
1790 OopTaskQueue* _work_queue;
1791 CMSBitMap* _bit_map;
1792 CMSInnerParMarkAndPushClosure _mark_and_push;
1793
1794 public:
1795 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1796 MemRegion span, CMSBitMap* bit_map,
1797 OopTaskQueue* work_queue):
1798 _collector(collector),
1799 _span(span),
1800 _bit_map(bit_map),
1801 _work_queue(work_queue),
1802 _mark_and_push(collector, span, bit_map, work_queue) { }
1803
1804 public:
1805 void trim_queue(uint max);
1806 void do_void();
1807 };
1808
1809 // Allow yielding or short-circuiting of reference list
1810 // precleaning work.
1811 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1812 CMSCollector* _collector;
1813 void do_yield_work();
1814 public:
1815 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1816 _collector(collector) {}
1817 virtual bool should_return();
1818 };
1819
1820
1821 // Convenience class that locks free list locks for given CMS collector
1822 class FreelistLocker: public StackObj {
1823 private:
1824 CMSCollector* _collector;
1825 public:
1826 FreelistLocker(CMSCollector* collector):
1827 _collector(collector) {
1828 _collector->getFreelistLocks();
1829 }
1830
1831 ~FreelistLocker() {
1832 _collector->releaseFreelistLocks();
1833 }
1834 };
1835
1836 // Mark all dead objects in a given space.
1837 class MarkDeadObjectsClosure: public BlkClosure {
1838 const CMSCollector* _collector;
1839 const CompactibleFreeListSpace* _sp;
1840 CMSBitMap* _live_bit_map;
1841 CMSBitMap* _dead_bit_map;
1842 public:
1843 MarkDeadObjectsClosure(const CMSCollector* collector,
1844 const CompactibleFreeListSpace* sp,
1845 CMSBitMap *live_bit_map,
1846 CMSBitMap *dead_bit_map) :
1847 _collector(collector),
1848 _sp(sp),
1849 _live_bit_map(live_bit_map),
1850 _dead_bit_map(dead_bit_map) {}
1851 size_t do_blk(HeapWord* addr);
1852 };
1853
1854 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1855
1856 public:
1857 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1858 };
1859
1860
1861 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP