1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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24
25 // ConcurrentMarkSweepGeneration is in support of a concurrent
26 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
27 // style. We assume, for now, that this generation is always the
28 // seniormost generation (modulo the PermGeneration), and for simplicity
29 // in the first implementation, that this generation is a single compactible
30 // space. Neither of these restrictions appears essential, and will be
31 // relaxed in the future when more time is available to implement the
32 // greater generality (and there's a need for it).
33 //
34 // Concurrent mode failures are currently handled by
35 // means of a sliding mark-compact.
36
37 class CMSAdaptiveSizePolicy;
38 class CMSConcMarkingTask;
39 class CMSGCAdaptivePolicyCounters;
40 class ConcurrentMarkSweepGeneration;
41 class ConcurrentMarkSweepPolicy;
42 class ConcurrentMarkSweepThread;
43 class CompactibleFreeListSpace;
44 class FreeChunk;
45 class PromotionInfo;
46 class ScanMarkedObjectsAgainCarefullyClosure;
47
48 // A generic CMS bit map. It's the basis for both the CMS marking bit map
49 // as well as for the mod union table (in each case only a subset of the
50 // methods are used). This is essentially a wrapper around the BitMap class,
51 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
52 // we have _shifter == 0. and for the mod union table we have
53 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
54 // XXX 64-bit issues in BitMap?
55 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
56 friend class VMStructs;
57
58 HeapWord* _bmStartWord; // base address of range covered by map
59 size_t _bmWordSize; // map size (in #HeapWords covered)
60 const int _shifter; // shifts to convert HeapWord to bit position
61 VirtualSpace _virtual_space; // underlying the bit map
62 BitMap _bm; // the bit map itself
63 public:
64 Mutex* const _lock; // mutex protecting _bm;
65
66 public:
67 // constructor
68 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
69
70 // allocates the actual storage for the map
71 bool allocate(MemRegion mr);
72 // field getter
73 Mutex* lock() const { return _lock; }
74 // locking verifier convenience function
75 void assert_locked() const PRODUCT_RETURN;
76
77 // inquiries
78 HeapWord* startWord() const { return _bmStartWord; }
79 size_t sizeInWords() const { return _bmWordSize; }
80 size_t sizeInBits() const { return _bm.size(); }
81 // the following is one past the last word in space
82 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
83
84 // reading marks
85 bool isMarked(HeapWord* addr) const;
86 bool par_isMarked(HeapWord* addr) const; // do not lock checks
87 bool isUnmarked(HeapWord* addr) const;
88 bool isAllClear() const;
89
90 // writing marks
91 void mark(HeapWord* addr);
92 // For marking by parallel GC threads;
93 // returns true if we did, false if another thread did
94 bool par_mark(HeapWord* addr);
95
96 void mark_range(MemRegion mr);
97 void par_mark_range(MemRegion mr);
98 void mark_large_range(MemRegion mr);
99 void par_mark_large_range(MemRegion mr);
100 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
101 void clear_range(MemRegion mr);
102 void par_clear_range(MemRegion mr);
103 void clear_large_range(MemRegion mr);
104 void par_clear_large_range(MemRegion mr);
105 void clear_all();
106 void clear_all_incrementally(); // Not yet implemented!!
107
108 NOT_PRODUCT(
109 // checks the memory region for validity
110 void region_invariant(MemRegion mr);
111 )
112
113 // iteration
114 void iterate(BitMapClosure* cl) {
115 _bm.iterate(cl);
116 }
117 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
118 void dirty_range_iterate_clear(MemRegionClosure* cl);
119 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
120
121 // auxiliary support for iteration
122 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
123 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
124 HeapWord* end_addr) const;
125 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
126 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
127 HeapWord* end_addr) const;
128 MemRegion getAndClearMarkedRegion(HeapWord* addr);
129 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
130 HeapWord* end_addr);
131
132 // conversion utilities
133 HeapWord* offsetToHeapWord(size_t offset) const;
134 size_t heapWordToOffset(HeapWord* addr) const;
135 size_t heapWordDiffToOffsetDiff(size_t diff) const;
136
137 // debugging
138 // is this address range covered by the bit-map?
139 NOT_PRODUCT(
140 bool covers(MemRegion mr) const;
141 bool covers(HeapWord* start, size_t size = 0) const;
142 )
143 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
144 };
145
146 // Represents a marking stack used by the CMS collector.
147 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
148 class CMSMarkStack: public CHeapObj {
149 //
150 friend class CMSCollector; // to get at expasion stats further below
151 //
152
153 VirtualSpace _virtual_space; // space for the stack
154 oop* _base; // bottom of stack
155 size_t _index; // one more than last occupied index
156 size_t _capacity; // max #elements
157 Mutex _par_lock; // an advisory lock used in case of parallel access
158 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run
159
160 protected:
161 size_t _hit_limit; // we hit max stack size limit
162 size_t _failed_double; // we failed expansion before hitting limit
163
164 public:
165 CMSMarkStack():
166 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
167 _hit_limit(0),
168 _failed_double(0) {}
169
170 bool allocate(size_t size);
171
172 size_t capacity() const { return _capacity; }
173
174 oop pop() {
175 if (!isEmpty()) {
176 return _base[--_index] ;
177 }
178 return NULL;
179 }
180
181 bool push(oop ptr) {
182 if (isFull()) {
183 return false;
184 } else {
185 _base[_index++] = ptr;
186 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
187 return true;
188 }
189 }
190
191 bool isEmpty() const { return _index == 0; }
192 bool isFull() const {
193 assert(_index <= _capacity, "buffer overflow");
194 return _index == _capacity;
195 }
196
197 size_t length() { return _index; }
198
199 // "Parallel versions" of some of the above
200 oop par_pop() {
201 // lock and pop
202 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
203 return pop();
204 }
205
206 bool par_push(oop ptr) {
207 // lock and push
208 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
209 return push(ptr);
210 }
211
212 // Forcibly reset the stack, losing all of its contents.
213 void reset() {
214 _index = 0;
215 }
216
217 // Expand the stack, typically in response to an overflow condition
218 void expand();
219
220 // Compute the least valued stack element.
221 oop least_value(HeapWord* low) {
222 oop least = (oop)low;
223 for (size_t i = 0; i < _index; i++) {
224 least = MIN2(least, _base[i]);
225 }
226 return least;
227 }
228
229 // Exposed here to allow stack expansion in || case
230 Mutex* par_lock() { return &_par_lock; }
231 };
232
233 class CardTableRS;
234 class CMSParGCThreadState;
235
236 class ModUnionClosure: public MemRegionClosure {
237 protected:
238 CMSBitMap* _t;
239 public:
240 ModUnionClosure(CMSBitMap* t): _t(t) { }
241 void do_MemRegion(MemRegion mr);
242 };
243
244 class ModUnionClosurePar: public ModUnionClosure {
245 public:
246 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
247 void do_MemRegion(MemRegion mr);
248 };
249
250 // Survivor Chunk Array in support of parallelization of
251 // Survivor Space rescan.
252 class ChunkArray: public CHeapObj {
253 size_t _index;
254 size_t _capacity;
255 HeapWord** _array; // storage for array
256
257 public:
258 ChunkArray() : _index(0), _capacity(0), _array(NULL) {}
259 ChunkArray(HeapWord** a, size_t c):
260 _index(0), _capacity(c), _array(a) {}
261
262 HeapWord** array() { return _array; }
263 void set_array(HeapWord** a) { _array = a; }
264
265 size_t capacity() { return _capacity; }
266 void set_capacity(size_t c) { _capacity = c; }
267
268 size_t end() {
269 assert(_index < capacity(), "_index out of bounds");
270 return _index;
271 } // exclusive
272
273 HeapWord* nth(size_t n) {
274 assert(n < end(), "Out of bounds access");
275 return _array[n];
276 }
277
278 void reset() {
279 _index = 0;
280 }
281
282 void record_sample(HeapWord* p, size_t sz) {
283 // For now we do not do anything with the size
284 if (_index < _capacity) {
285 _array[_index++] = p;
286 }
287 }
288 };
289
290 //
291 // Timing, allocation and promotion statistics for gc scheduling and incremental
292 // mode pacing. Most statistics are exponential averages.
293 //
294 class CMSStats VALUE_OBJ_CLASS_SPEC {
295 private:
296 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
297
298 // The following are exponential averages with factor alpha:
299 // avg = (100 - alpha) * avg + alpha * cur_sample
300 //
301 // The durations measure: end_time[n] - start_time[n]
302 // The periods measure: start_time[n] - start_time[n-1]
303 //
304 // The cms period and duration include only concurrent collections; time spent
305 // in foreground cms collections due to System.gc() or because of a failure to
306 // keep up are not included.
307 //
308 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
309 // real value, but is used only after the first period. A value of 100 is
310 // used for the first sample so it gets the entire weight.
311 unsigned int _saved_alpha; // 0-100
312 unsigned int _gc0_alpha;
313 unsigned int _cms_alpha;
314
315 double _gc0_duration;
316 double _gc0_period;
317 size_t _gc0_promoted; // bytes promoted per gc0
318 double _cms_duration;
319 double _cms_duration_pre_sweep; // time from initiation to start of sweep
320 double _cms_duration_per_mb;
321 double _cms_period;
322 size_t _cms_allocated; // bytes of direct allocation per gc0 period
323
324 // Timers.
325 elapsedTimer _cms_timer;
326 TimeStamp _gc0_begin_time;
327 TimeStamp _cms_begin_time;
328 TimeStamp _cms_end_time;
329
330 // Snapshots of the amount used in the CMS generation.
331 size_t _cms_used_at_gc0_begin;
332 size_t _cms_used_at_gc0_end;
333 size_t _cms_used_at_cms_begin;
334
335 // Used to prevent the duty cycle from being reduced in the middle of a cms
336 // cycle.
337 bool _allow_duty_cycle_reduction;
338
339 enum {
340 _GC0_VALID = 0x1,
341 _CMS_VALID = 0x2,
342 _ALL_VALID = _GC0_VALID | _CMS_VALID
343 };
344
345 unsigned int _valid_bits;
346
347 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
348
349 protected:
350
351 // Return a duty cycle that avoids wild oscillations, by limiting the amount
352 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
353 // as a recommended value).
354 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
355 unsigned int new_duty_cycle);
356 unsigned int icms_update_duty_cycle_impl();
357
358 // In support of adjusting of cms trigger ratios based on history
359 // of concurrent mode failure.
360 double cms_free_adjustment_factor(size_t free) const;
361 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
362
363 public:
364 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
365 unsigned int alpha = CMSExpAvgFactor);
366
367 // Whether or not the statistics contain valid data; higher level statistics
368 // cannot be called until this returns true (they require at least one young
369 // gen and one cms cycle to have completed).
370 bool valid() const;
371
372 // Record statistics.
373 void record_gc0_begin();
374 void record_gc0_end(size_t cms_gen_bytes_used);
375 void record_cms_begin();
376 void record_cms_end();
377
378 // Allow management of the cms timer, which must be stopped/started around
379 // yield points.
380 elapsedTimer& cms_timer() { return _cms_timer; }
381 void start_cms_timer() { _cms_timer.start(); }
382 void stop_cms_timer() { _cms_timer.stop(); }
383
384 // Basic statistics; units are seconds or bytes.
385 double gc0_period() const { return _gc0_period; }
386 double gc0_duration() const { return _gc0_duration; }
387 size_t gc0_promoted() const { return _gc0_promoted; }
388 double cms_period() const { return _cms_period; }
389 double cms_duration() const { return _cms_duration; }
390 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
391 size_t cms_allocated() const { return _cms_allocated; }
392
393 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
394
395 // Seconds since the last background cms cycle began or ended.
396 double cms_time_since_begin() const;
397 double cms_time_since_end() const;
398
399 // Higher level statistics--caller must check that valid() returns true before
400 // calling.
401
402 // Returns bytes promoted per second of wall clock time.
403 double promotion_rate() const;
404
405 // Returns bytes directly allocated per second of wall clock time.
406 double cms_allocation_rate() const;
407
408 // Rate at which space in the cms generation is being consumed (sum of the
409 // above two).
410 double cms_consumption_rate() const;
411
412 // Returns an estimate of the number of seconds until the cms generation will
413 // fill up, assuming no collection work is done.
414 double time_until_cms_gen_full() const;
415
416 // Returns an estimate of the number of seconds remaining until
417 // the cms generation collection should start.
418 double time_until_cms_start() const;
419
420 // End of higher level statistics.
421
422 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
423 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
424
425 // Update the duty cycle and return the new value.
426 unsigned int icms_update_duty_cycle();
427
428 // Debugging.
429 void print_on(outputStream* st) const PRODUCT_RETURN;
430 void print() const { print_on(gclog_or_tty); }
431 };
432
433 // A closure related to weak references processing which
434 // we embed in the CMSCollector, since we need to pass
435 // it to the reference processor for secondary filtering
436 // of references based on reachability of referent;
437 // see role of _is_alive_non_header closure in the
438 // ReferenceProcessor class.
439 // For objects in the CMS generation, this closure checks
440 // if the object is "live" (reachable). Used in weak
441 // reference processing.
442 class CMSIsAliveClosure: public BoolObjectClosure {
443 const MemRegion _span;
444 const CMSBitMap* _bit_map;
445
446 friend class CMSCollector;
447 public:
448 CMSIsAliveClosure(MemRegion span,
449 CMSBitMap* bit_map):
450 _span(span),
451 _bit_map(bit_map) {
452 assert(!span.is_empty(), "Empty span could spell trouble");
453 }
454
455 void do_object(oop obj) {
456 assert(false, "not to be invoked");
457 }
458
459 bool do_object_b(oop obj);
460 };
461
462
463 // Implements AbstractRefProcTaskExecutor for CMS.
464 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
465 public:
466
467 CMSRefProcTaskExecutor(CMSCollector& collector)
468 : _collector(collector)
469 { }
470
471 // Executes a task using worker threads.
472 virtual void execute(ProcessTask& task);
473 virtual void execute(EnqueueTask& task);
474 private:
475 CMSCollector& _collector;
476 };
477
478
479 class CMSCollector: public CHeapObj {
480 friend class VMStructs;
481 friend class ConcurrentMarkSweepThread;
482 friend class ConcurrentMarkSweepGeneration;
483 friend class CompactibleFreeListSpace;
484 friend class CMSParRemarkTask;
485 friend class CMSConcMarkingTask;
486 friend class CMSRefProcTaskProxy;
487 friend class CMSRefProcTaskExecutor;
488 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
489 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
490 friend class PushOrMarkClosure; // to access _restart_addr
491 friend class Par_PushOrMarkClosure; // to access _restart_addr
492 friend class MarkFromRootsClosure; // -- ditto --
493 // ... and for clearing cards
494 friend class Par_MarkFromRootsClosure; // to access _restart_addr
495 // ... and for clearing cards
496 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
497 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
498 friend class PushAndMarkVerifyClosure; // -- ditto --
499 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
500 friend class PushAndMarkClosure; // -- ditto --
501 friend class Par_PushAndMarkClosure; // -- ditto --
502 friend class CMSKeepAliveClosure; // -- ditto --
503 friend class CMSDrainMarkingStackClosure; // -- ditto --
504 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
505 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
506 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
507 friend class VM_CMS_Operation;
508 friend class VM_CMS_Initial_Mark;
509 friend class VM_CMS_Final_Remark;
510 friend class TraceCMSMemoryManagerStats;
511
512 private:
513 jlong _time_of_last_gc;
514 void update_time_of_last_gc(jlong now) {
515 _time_of_last_gc = now;
516 }
517
518 OopTaskQueueSet* _task_queues;
519
520 // Overflow list of grey objects, threaded through mark-word
521 // Manipulated with CAS in the parallel/multi-threaded case.
522 oop _overflow_list;
523 // The following array-pair keeps track of mark words
524 // displaced for accomodating overflow list above.
525 // This code will likely be revisited under RFE#4922830.
526 GrowableArray<oop>* _preserved_oop_stack;
527 GrowableArray<markOop>* _preserved_mark_stack;
528
529 int* _hash_seed;
530
531 // In support of multi-threaded concurrent phases
532 YieldingFlexibleWorkGang* _conc_workers;
533
534 // Performance Counters
535 CollectorCounters* _gc_counters;
536
537 // Initialization Errors
538 bool _completed_initialization;
539
540 // In support of ExplicitGCInvokesConcurrent
541 static bool _full_gc_requested;
542 unsigned int _collection_count_start;
543
544 // Should we unload classes this concurrent cycle?
545 bool _should_unload_classes;
546 unsigned int _concurrent_cycles_since_last_unload;
547 unsigned int concurrent_cycles_since_last_unload() const {
548 return _concurrent_cycles_since_last_unload;
549 }
550 // Did we (allow) unload classes in the previous concurrent cycle?
551 bool unloaded_classes_last_cycle() const {
552 return concurrent_cycles_since_last_unload() == 0;
553 }
554 // Root scanning options for perm gen
555 int _roots_scanning_options;
556 int roots_scanning_options() const { return _roots_scanning_options; }
557 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
558 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
559
560 // Verification support
561 CMSBitMap _verification_mark_bm;
562 void verify_after_remark_work_1();
563 void verify_after_remark_work_2();
564
565 // true if any verification flag is on.
566 bool _verifying;
567 bool verifying() const { return _verifying; }
568 void set_verifying(bool v) { _verifying = v; }
569
570 // Collector policy
571 ConcurrentMarkSweepPolicy* _collector_policy;
572 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
573
574 // XXX Move these to CMSStats ??? FIX ME !!!
575 elapsedTimer _inter_sweep_timer; // time between sweeps
576 elapsedTimer _intra_sweep_timer; // time _in_ sweeps
577 // padded decaying average estimates of the above
578 AdaptivePaddedAverage _inter_sweep_estimate;
579 AdaptivePaddedAverage _intra_sweep_estimate;
580
581 protected:
582 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
583 ConcurrentMarkSweepGeneration* _permGen; // perm gen
584 MemRegion _span; // span covering above two
585 CardTableRS* _ct; // card table
586
587 // CMS marking support structures
588 CMSBitMap _markBitMap;
589 CMSBitMap _modUnionTable;
590 CMSMarkStack _markStack;
591 CMSMarkStack _revisitStack; // used to keep track of klassKlass objects
592 // to revisit
593 CMSBitMap _perm_gen_verify_bit_map; // Mark bit map for perm gen verification support.
594
595 HeapWord* _restart_addr; // in support of marking stack overflow
596 void lower_restart_addr(HeapWord* low);
597
598 // Counters in support of marking stack / work queue overflow handling:
599 // a non-zero value indicates certain types of overflow events during
600 // the current CMS cycle and could lead to stack resizing efforts at
601 // an opportune future time.
602 size_t _ser_pmc_preclean_ovflw;
603 size_t _ser_pmc_remark_ovflw;
604 size_t _par_pmc_remark_ovflw;
605 size_t _ser_kac_preclean_ovflw;
606 size_t _ser_kac_ovflw;
607 size_t _par_kac_ovflw;
608 NOT_PRODUCT(ssize_t _num_par_pushes;)
609
610 // ("Weak") Reference processing support
611 ReferenceProcessor* _ref_processor;
612 CMSIsAliveClosure _is_alive_closure;
613 // keep this textually after _markBitMap and _span; c'tor dependency
614
615 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
616 ModUnionClosure _modUnionClosure;
617 ModUnionClosurePar _modUnionClosurePar;
618
619 // CMS abstract state machine
620 // initial_state: Idling
621 // next_state(Idling) = {Marking}
622 // next_state(Marking) = {Precleaning, Sweeping}
623 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
624 // next_state(AbortablePreclean) = {FinalMarking}
625 // next_state(FinalMarking) = {Sweeping}
626 // next_state(Sweeping) = {Resizing}
627 // next_state(Resizing) = {Resetting}
628 // next_state(Resetting) = {Idling}
629 // The numeric values below are chosen so that:
630 // . _collectorState <= Idling == post-sweep && pre-mark
631 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
632 // precleaning || abortablePrecleanb
633 public:
634 enum CollectorState {
635 Resizing = 0,
636 Resetting = 1,
637 Idling = 2,
638 InitialMarking = 3,
639 Marking = 4,
640 Precleaning = 5,
641 AbortablePreclean = 6,
642 FinalMarking = 7,
643 Sweeping = 8
644 };
645 protected:
646 static CollectorState _collectorState;
647
648 // State related to prologue/epilogue invocation for my generations
649 bool _between_prologue_and_epilogue;
650
651 // Signalling/State related to coordination between fore- and backgroud GC
652 // Note: When the baton has been passed from background GC to foreground GC,
653 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
654 static bool _foregroundGCIsActive; // true iff foreground collector is active or
655 // wants to go active
656 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
657 // yet passed the baton to the foreground GC
658
659 // Support for CMSScheduleRemark (abortable preclean)
660 bool _abort_preclean;
661 bool _start_sampling;
662
663 int _numYields;
664 size_t _numDirtyCards;
665 size_t _sweep_count;
666 // number of full gc's since the last concurrent gc.
667 uint _full_gcs_since_conc_gc;
668
669 // occupancy used for bootstrapping stats
670 double _bootstrap_occupancy;
671
672 // timer
673 elapsedTimer _timer;
674
675 // Timing, allocation and promotion statistics, used for scheduling.
676 CMSStats _stats;
677
678 // Allocation limits installed in the young gen, used only in
679 // CMSIncrementalMode. When an allocation in the young gen would cross one of
680 // these limits, the cms generation is notified and the cms thread is started
681 // or stopped, respectively.
682 HeapWord* _icms_start_limit;
683 HeapWord* _icms_stop_limit;
684
685 enum CMS_op_type {
686 CMS_op_checkpointRootsInitial,
687 CMS_op_checkpointRootsFinal
688 };
689
690 void do_CMS_operation(CMS_op_type op);
691 bool stop_world_and_do(CMS_op_type op);
692
693 OopTaskQueueSet* task_queues() { return _task_queues; }
694 int* hash_seed(int i) { return &_hash_seed[i]; }
695 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
696
697 // Support for parallelizing Eden rescan in CMS remark phase
698 void sample_eden(); // ... sample Eden space top
699
700 private:
701 // Support for parallelizing young gen rescan in CMS remark phase
702 Generation* _young_gen; // the younger gen
703 HeapWord** _top_addr; // ... Top of Eden
704 HeapWord** _end_addr; // ... End of Eden
705 HeapWord** _eden_chunk_array; // ... Eden partitioning array
706 size_t _eden_chunk_index; // ... top (exclusive) of array
707 size_t _eden_chunk_capacity; // ... max entries in array
708
709 // Support for parallelizing survivor space rescan
710 HeapWord** _survivor_chunk_array;
711 size_t _survivor_chunk_index;
712 size_t _survivor_chunk_capacity;
713 size_t* _cursor;
714 ChunkArray* _survivor_plab_array;
715
716 // Support for marking stack overflow handling
717 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
718 bool par_take_from_overflow_list(size_t num, OopTaskQueue* to_work_q);
719 void push_on_overflow_list(oop p);
720 void par_push_on_overflow_list(oop p);
721 // the following is, obviously, not, in general, "MT-stable"
722 bool overflow_list_is_empty() const;
723
724 void preserve_mark_if_necessary(oop p);
725 void par_preserve_mark_if_necessary(oop p);
726 void preserve_mark_work(oop p, markOop m);
727 void restore_preserved_marks_if_any();
728 NOT_PRODUCT(bool no_preserved_marks() const;)
729 // in support of testing overflow code
730 NOT_PRODUCT(int _overflow_counter;)
731 NOT_PRODUCT(bool simulate_overflow();) // sequential
732 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
733
734 // CMS work methods
735 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
736
737 // a return value of false indicates failure due to stack overflow
738 bool markFromRootsWork(bool asynch); // concurrent marking work
739
740 public: // FIX ME!!! only for testing
741 bool do_marking_st(bool asynch); // single-threaded marking
742 bool do_marking_mt(bool asynch); // multi-threaded marking
743
744 private:
745
746 // concurrent precleaning work
747 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
748 ScanMarkedObjectsAgainCarefullyClosure* cl);
749 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
750 ScanMarkedObjectsAgainCarefullyClosure* cl);
751 // Does precleaning work, returning a quantity indicative of
752 // the amount of "useful work" done.
753 size_t preclean_work(bool clean_refs, bool clean_survivors);
754 void abortable_preclean(); // Preclean while looking for possible abort
755 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
756 // Helper function for above; merge-sorts the per-thread plab samples
757 void merge_survivor_plab_arrays(ContiguousSpace* surv);
758 // Resets (i.e. clears) the per-thread plab sample vectors
759 void reset_survivor_plab_arrays();
760
761 // final (second) checkpoint work
762 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
763 bool init_mark_was_synchronous);
764 // work routine for parallel version of remark
765 void do_remark_parallel();
766 // work routine for non-parallel version of remark
767 void do_remark_non_parallel();
768 // reference processing work routine (during second checkpoint)
769 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
770
771 // concurrent sweeping work
772 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
773
774 // (concurrent) resetting of support data structures
775 void reset(bool asynch);
776
777 // Clear _expansion_cause fields of constituent generations
778 void clear_expansion_cause();
779
780 // An auxilliary method used to record the ends of
781 // used regions of each generation to limit the extent of sweep
782 void save_sweep_limits();
783
784 // Resize the generations included in the collector.
785 void compute_new_size();
786
787 // A work method used by foreground collection to determine
788 // what type of collection (compacting or not, continuing or fresh)
789 // it should do.
790 void decide_foreground_collection_type(bool clear_all_soft_refs,
791 bool* should_compact, bool* should_start_over);
792
793 // A work method used by the foreground collector to do
794 // a mark-sweep-compact.
795 void do_compaction_work(bool clear_all_soft_refs);
796
797 // A work method used by the foreground collector to do
798 // a mark-sweep, after taking over from a possibly on-going
799 // concurrent mark-sweep collection.
800 void do_mark_sweep_work(bool clear_all_soft_refs,
801 CollectorState first_state, bool should_start_over);
802
803 // If the backgrould GC is active, acquire control from the background
804 // GC and do the collection.
805 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
806
807 // For synchronizing passing of control from background to foreground
808 // GC. waitForForegroundGC() is called by the background
809 // collector. It if had to wait for a foreground collection,
810 // it returns true and the background collection should assume
811 // that the collection was finished by the foreground
812 // collector.
813 bool waitForForegroundGC();
814
815 // Incremental mode triggering: recompute the icms duty cycle and set the
816 // allocation limits in the young gen.
817 void icms_update_allocation_limits();
818
819 size_t block_size_using_printezis_bits(HeapWord* addr) const;
820 size_t block_size_if_printezis_bits(HeapWord* addr) const;
821 HeapWord* next_card_start_after_block(HeapWord* addr) const;
822
823 void setup_cms_unloading_and_verification_state();
824 public:
825 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
826 ConcurrentMarkSweepGeneration* permGen,
827 CardTableRS* ct,
828 ConcurrentMarkSweepPolicy* cp);
829 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
830
831 ReferenceProcessor* ref_processor() { return _ref_processor; }
832 void ref_processor_init();
833
834 Mutex* bitMapLock() const { return _markBitMap.lock(); }
835 static CollectorState abstract_state() { return _collectorState; }
836
837 bool should_abort_preclean() const; // Whether preclean should be aborted.
838 size_t get_eden_used() const;
839 size_t get_eden_capacity() const;
840
841 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
842
843 // locking checks
844 NOT_PRODUCT(static bool have_cms_token();)
845
846 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
847 bool shouldConcurrentCollect();
848
849 void collect(bool full,
850 bool clear_all_soft_refs,
851 size_t size,
852 bool tlab);
853 void collect_in_background(bool clear_all_soft_refs);
854 void collect_in_foreground(bool clear_all_soft_refs);
855
856 // In support of ExplicitGCInvokesConcurrent
857 static void request_full_gc(unsigned int full_gc_count);
858 // Should we unload classes in a particular concurrent cycle?
859 bool should_unload_classes() const {
860 return _should_unload_classes;
861 }
862 bool update_should_unload_classes();
863
864 void direct_allocated(HeapWord* start, size_t size);
865
866 // Object is dead if not marked and current phase is sweeping.
867 bool is_dead_obj(oop obj) const;
868
869 // After a promotion (of "start"), do any necessary marking.
870 // If "par", then it's being done by a parallel GC thread.
871 // The last two args indicate if we need precise marking
872 // and if so the size of the object so it can be dirtied
873 // in its entirety.
874 void promoted(bool par, HeapWord* start,
875 bool is_obj_array, size_t obj_size);
876
877 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
878 size_t word_size);
879
880 void getFreelistLocks() const;
881 void releaseFreelistLocks() const;
882 bool haveFreelistLocks() const;
883
884 // GC prologue and epilogue
885 void gc_prologue(bool full);
886 void gc_epilogue(bool full);
887
888 jlong time_of_last_gc(jlong now) {
889 if (_collectorState <= Idling) {
890 // gc not in progress
891 return _time_of_last_gc;
892 } else {
893 // collection in progress
894 return now;
895 }
896 }
897
898 // Support for parallel remark of survivor space
899 void* get_data_recorder(int thr_num);
900
901 CMSBitMap* markBitMap() { return &_markBitMap; }
902 void directAllocated(HeapWord* start, size_t size);
903
904 // main CMS steps and related support
905 void checkpointRootsInitial(bool asynch);
906 bool markFromRoots(bool asynch); // a return value of false indicates failure
907 // due to stack overflow
908 void preclean();
909 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
910 bool init_mark_was_synchronous);
911 void sweep(bool asynch);
912
913 // Check that the currently executing thread is the expected
914 // one (foreground collector or background collector).
915 static void check_correct_thread_executing() PRODUCT_RETURN;
916 // XXXPERM void print_statistics() PRODUCT_RETURN;
917
918 bool is_cms_reachable(HeapWord* addr);
919
920 // Performance Counter Support
921 CollectorCounters* counters() { return _gc_counters; }
922
923 // timer stuff
924 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
925 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
926 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
927 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
928
929 int yields() { return _numYields; }
930 void resetYields() { _numYields = 0; }
931 void incrementYields() { _numYields++; }
932 void resetNumDirtyCards() { _numDirtyCards = 0; }
933 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
934 size_t numDirtyCards() { return _numDirtyCards; }
935
936 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
937 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
938 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
939 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
940 size_t sweep_count() const { return _sweep_count; }
941 void increment_sweep_count() { _sweep_count++; }
942
943 // Timers/stats for gc scheduling and incremental mode pacing.
944 CMSStats& stats() { return _stats; }
945
946 // Convenience methods that check whether CMSIncrementalMode is enabled and
947 // forward to the corresponding methods in ConcurrentMarkSweepThread.
948 static void start_icms();
949 static void stop_icms(); // Called at the end of the cms cycle.
950 static void disable_icms(); // Called before a foreground collection.
951 static void enable_icms(); // Called after a foreground collection.
952 void icms_wait(); // Called at yield points.
953
954 // Adaptive size policy
955 CMSAdaptiveSizePolicy* size_policy();
956 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
957
958 // debugging
959 void verify(bool);
960 bool verify_after_remark();
961 void verify_ok_to_terminate() const PRODUCT_RETURN;
962 void verify_work_stacks_empty() const PRODUCT_RETURN;
963 void verify_overflow_empty() const PRODUCT_RETURN;
964
965 // convenience methods in support of debugging
966 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
967 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
968
969 // accessors
970 CMSMarkStack* verification_mark_stack() { return &_markStack; }
971 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
972
973 // Get the bit map with a perm gen "deadness" information.
974 CMSBitMap* perm_gen_verify_bit_map() { return &_perm_gen_verify_bit_map; }
975
976 // Initialization errors
977 bool completed_initialization() { return _completed_initialization; }
978 };
979
980 class CMSExpansionCause : public AllStatic {
981 public:
982 enum Cause {
983 _no_expansion,
984 _satisfy_free_ratio,
985 _satisfy_promotion,
986 _satisfy_allocation,
987 _allocate_par_lab,
988 _allocate_par_spooling_space,
989 _adaptive_size_policy
990 };
991 // Return a string describing the cause of the expansion.
992 static const char* to_string(CMSExpansionCause::Cause cause);
993 };
994
995 class ConcurrentMarkSweepGeneration: public CardGeneration {
996 friend class VMStructs;
997 friend class ConcurrentMarkSweepThread;
998 friend class ConcurrentMarkSweep;
999 friend class CMSCollector;
1000 protected:
1001 static CMSCollector* _collector; // the collector that collects us
1002 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1003
1004 // Performance Counters
1005 GenerationCounters* _gen_counters;
1006 GSpaceCounters* _space_counters;
1007
1008 // Words directly allocated, used by CMSStats.
1009 size_t _direct_allocated_words;
1010
1011 // Non-product stat counters
1012 NOT_PRODUCT(
1013 int _numObjectsPromoted;
1014 int _numWordsPromoted;
1015 int _numObjectsAllocated;
1016 int _numWordsAllocated;
1017 )
1018
1019 // Used for sizing decisions
1020 bool _incremental_collection_failed;
1021 bool incremental_collection_failed() {
1022 return _incremental_collection_failed;
1023 }
1024 void set_incremental_collection_failed() {
1025 _incremental_collection_failed = true;
1026 }
1027 void clear_incremental_collection_failed() {
1028 _incremental_collection_failed = false;
1029 }
1030
1031 // accessors
1032 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1033 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1034
1035 private:
1036 // For parallel young-gen GC support.
1037 CMSParGCThreadState** _par_gc_thread_states;
1038
1039 // Reason generation was expanded
1040 CMSExpansionCause::Cause _expansion_cause;
1041
1042 // In support of MinChunkSize being larger than min object size
1043 const double _dilatation_factor;
1044
1045 enum CollectionTypes {
1046 Concurrent_collection_type = 0,
1047 MS_foreground_collection_type = 1,
1048 MSC_foreground_collection_type = 2,
1049 Unknown_collection_type = 3
1050 };
1051
1052 CollectionTypes _debug_collection_type;
1053
1054 // Fraction of current occupancy at which to start a CMS collection which
1055 // will collect this generation (at least).
1056 double _initiating_occupancy;
1057
1058 protected:
1059 // Shrink generation by specified size (returns false if unable to shrink)
1060 virtual void shrink_by(size_t bytes);
1061
1062 // Update statistics for GC
1063 virtual void update_gc_stats(int level, bool full);
1064
1065 // Maximum available space in the generation (including uncommitted)
1066 // space.
1067 size_t max_available() const;
1068
1069 // getter and initializer for _initiating_occupancy field.
1070 double initiating_occupancy() const { return _initiating_occupancy; }
1071 void init_initiating_occupancy(intx io, intx tr);
1072
1073 public:
1074 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1075 int level, CardTableRS* ct,
1076 bool use_adaptive_freelists,
1077 FreeBlockDictionary::DictionaryChoice);
1078
1079 // Accessors
1080 CMSCollector* collector() const { return _collector; }
1081 static void set_collector(CMSCollector* collector) {
1082 assert(_collector == NULL, "already set");
1083 _collector = collector;
1084 }
1085 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1086
1087 Mutex* freelistLock() const;
1088
1089 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1090
1091 // Adaptive size policy
1092 CMSAdaptiveSizePolicy* size_policy();
1093
1094 bool refs_discovery_is_atomic() const { return false; }
1095 bool refs_discovery_is_mt() const {
1096 // Note: CMS does MT-discovery during the parallel-remark
1097 // phases. Use ReferenceProcessorMTMutator to make refs
1098 // discovery MT-safe during such phases or other parallel
1099 // discovery phases in the future. This may all go away
1100 // if/when we decide that refs discovery is sufficiently
1101 // rare that the cost of the CAS's involved is in the
1102 // noise. That's a measurement that should be done, and
1103 // the code simplified if that turns out to be the case.
1104 return false;
1105 }
1106
1107 // Override
1108 virtual void ref_processor_init();
1109
1110 // Grow generation by specified size (returns false if unable to grow)
1111 bool grow_by(size_t bytes);
1112 // Grow generation to reserved size.
1113 bool grow_to_reserved();
1114
1115 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1116
1117 // Space enquiries
1118 size_t capacity() const;
1119 size_t used() const;
1120 size_t free() const;
1121 double occupancy() const { return ((double)used())/((double)capacity()); }
1122 size_t contiguous_available() const;
1123 size_t unsafe_max_alloc_nogc() const;
1124
1125 // over-rides
1126 MemRegion used_region() const;
1127 MemRegion used_region_at_save_marks() const;
1128
1129 // Does a "full" (forced) collection invoked on this generation collect
1130 // all younger generations as well? Note that the second conjunct is a
1131 // hack to allow the collection of the younger gen first if the flag is
1132 // set. This is better than using th policy's should_collect_gen0_first()
1133 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1134 virtual bool full_collects_younger_generations() const {
1135 return UseCMSCompactAtFullCollection && !CollectGen0First;
1136 }
1137
1138 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1139
1140 // Support for compaction
1141 CompactibleSpace* first_compaction_space() const;
1142 // Adjust quantites in the generation affected by
1143 // the compaction.
1144 void reset_after_compaction();
1145
1146 // Allocation support
1147 HeapWord* allocate(size_t size, bool tlab);
1148 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1149 oop promote(oop obj, size_t obj_size);
1150 HeapWord* par_allocate(size_t size, bool tlab) {
1151 return allocate(size, tlab);
1152 }
1153
1154 // Incremental mode triggering.
1155 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1156 size_t word_size);
1157
1158 // Used by CMSStats to track direct allocation. The value is sampled and
1159 // reset after each young gen collection.
1160 size_t direct_allocated_words() const { return _direct_allocated_words; }
1161 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1162
1163 // Overrides for parallel promotion.
1164 virtual oop par_promote(int thread_num,
1165 oop obj, markOop m, size_t word_sz);
1166 // This one should not be called for CMS.
1167 virtual void par_promote_alloc_undo(int thread_num,
1168 HeapWord* obj, size_t word_sz);
1169 virtual void par_promote_alloc_done(int thread_num);
1170 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1171
1172 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes,
1173 bool younger_handles_promotion_failure) const;
1174
1175 // Inform this (non-young) generation that a promotion failure was
1176 // encountered during a collection of a younger generation that
1177 // promotes into this generation.
1178 virtual void promotion_failure_occurred();
1179
1180 bool should_collect(bool full, size_t size, bool tlab);
1181 virtual bool should_concurrent_collect() const;
1182 virtual bool is_too_full() const;
1183 void collect(bool full,
1184 bool clear_all_soft_refs,
1185 size_t size,
1186 bool tlab);
1187
1188 HeapWord* expand_and_allocate(size_t word_size,
1189 bool tlab,
1190 bool parallel = false);
1191
1192 // GC prologue and epilogue
1193 void gc_prologue(bool full);
1194 void gc_prologue_work(bool full, bool registerClosure,
1195 ModUnionClosure* modUnionClosure);
1196 void gc_epilogue(bool full);
1197 void gc_epilogue_work(bool full);
1198
1199 // Time since last GC of this generation
1200 jlong time_of_last_gc(jlong now) {
1201 return collector()->time_of_last_gc(now);
1202 }
1203 void update_time_of_last_gc(jlong now) {
1204 collector()-> update_time_of_last_gc(now);
1205 }
1206
1207 // Allocation failure
1208 void expand(size_t bytes, size_t expand_bytes,
1209 CMSExpansionCause::Cause cause);
1210 virtual bool expand(size_t bytes, size_t expand_bytes);
1211 void shrink(size_t bytes);
1212 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1213 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1214
1215 // Iteration support and related enquiries
1216 void save_marks();
1217 bool no_allocs_since_save_marks();
1218 void object_iterate_since_last_GC(ObjectClosure* cl);
1219 void younger_refs_iterate(OopsInGenClosure* cl);
1220
1221 // Iteration support specific to CMS generations
1222 void save_sweep_limit();
1223
1224 // More iteration support
1225 virtual void oop_iterate(MemRegion mr, OopClosure* cl);
1226 virtual void oop_iterate(OopClosure* cl);
1227 virtual void safe_object_iterate(ObjectClosure* cl);
1228 virtual void object_iterate(ObjectClosure* cl);
1229
1230 // Need to declare the full complement of closures, whether we'll
1231 // override them or not, or get message from the compiler:
1232 // oop_since_save_marks_iterate_nv hides virtual function...
1233 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1234 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1235 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1236
1237 // Smart allocation XXX -- move to CFLSpace?
1238 void setNearLargestChunk();
1239 bool isNearLargestChunk(HeapWord* addr);
1240
1241 // Get the chunk at the end of the space. Delagates to
1242 // the space.
1243 FreeChunk* find_chunk_at_end();
1244
1245 // Overriding of unused functionality (sharing not yet supported with CMS)
1246 void pre_adjust_pointers();
1247 void post_compact();
1248
1249 // Debugging
1250 void prepare_for_verify();
1251 void verify(bool allow_dirty);
1252 void print_statistics() PRODUCT_RETURN;
1253
1254 // Performance Counters support
1255 virtual void update_counters();
1256 virtual void update_counters(size_t used);
1257 void initialize_performance_counters();
1258 CollectorCounters* counters() { return collector()->counters(); }
1259
1260 // Support for parallel remark of survivor space
1261 void* get_data_recorder(int thr_num) {
1262 //Delegate to collector
1263 return collector()->get_data_recorder(thr_num);
1264 }
1265
1266 // Printing
1267 const char* name() const;
1268 virtual const char* short_name() const { return "CMS"; }
1269 void print() const;
1270 void printOccupancy(const char* s);
1271 bool must_be_youngest() const { return false; }
1272 bool must_be_oldest() const { return true; }
1273
1274 void compute_new_size();
1275
1276 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1277 void rotate_debug_collection_type();
1278 };
1279
1280 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1281
1282 // Return the size policy from the heap's collector
1283 // policy casted to CMSAdaptiveSizePolicy*.
1284 CMSAdaptiveSizePolicy* cms_size_policy() const;
1285
1286 // Resize the generation based on the adaptive size
1287 // policy.
1288 void resize(size_t cur_promo, size_t desired_promo);
1289
1290 // Return the GC counters from the collector policy
1291 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1292
1293 virtual void shrink_by(size_t bytes);
1294
1295 public:
1296 virtual void compute_new_size();
1297 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1298 int level, CardTableRS* ct,
1299 bool use_adaptive_freelists,
1300 FreeBlockDictionary::DictionaryChoice
1301 dictionaryChoice) :
1302 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1303 use_adaptive_freelists, dictionaryChoice) {}
1304
1305 virtual const char* short_name() const { return "ASCMS"; }
1306 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1307
1308 virtual void update_counters();
1309 virtual void update_counters(size_t used);
1310 };
1311
1312 //
1313 // Closures of various sorts used by CMS to accomplish its work
1314 //
1315
1316 // This closure is used to check that a certain set of oops is empty.
1317 class FalseClosure: public OopClosure {
1318 public:
1319 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1320 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1321 };
1322
1323 // This closure is used to do concurrent marking from the roots
1324 // following the first checkpoint.
1325 class MarkFromRootsClosure: public BitMapClosure {
1326 CMSCollector* _collector;
1327 MemRegion _span;
1328 CMSBitMap* _bitMap;
1329 CMSBitMap* _mut;
1330 CMSMarkStack* _markStack;
1331 CMSMarkStack* _revisitStack;
1332 bool _yield;
1333 int _skipBits;
1334 HeapWord* _finger;
1335 HeapWord* _threshold;
1336 DEBUG_ONLY(bool _verifying;)
1337
1338 public:
1339 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1340 CMSBitMap* bitMap,
1341 CMSMarkStack* markStack,
1342 CMSMarkStack* revisitStack,
1343 bool should_yield, bool verifying = false);
1344 bool do_bit(size_t offset);
1345 void reset(HeapWord* addr);
1346 inline void do_yield_check();
1347
1348 private:
1349 void scanOopsInOop(HeapWord* ptr);
1350 void do_yield_work();
1351 };
1352
1353 // This closure is used to do concurrent multi-threaded
1354 // marking from the roots following the first checkpoint.
1355 // XXX This should really be a subclass of The serial version
1356 // above, but i have not had the time to refactor things cleanly.
1357 // That willbe done for Dolphin.
1358 class Par_MarkFromRootsClosure: public BitMapClosure {
1359 CMSCollector* _collector;
1360 MemRegion _whole_span;
1361 MemRegion _span;
1362 CMSBitMap* _bit_map;
1363 CMSBitMap* _mut;
1364 OopTaskQueue* _work_queue;
1365 CMSMarkStack* _overflow_stack;
1366 CMSMarkStack* _revisit_stack;
1367 bool _yield;
1368 int _skip_bits;
1369 HeapWord* _finger;
1370 HeapWord* _threshold;
1371 CMSConcMarkingTask* _task;
1372 public:
1373 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1374 MemRegion span,
1375 CMSBitMap* bit_map,
1376 OopTaskQueue* work_queue,
1377 CMSMarkStack* overflow_stack,
1378 CMSMarkStack* revisit_stack,
1379 bool should_yield);
1380 bool do_bit(size_t offset);
1381 inline void do_yield_check();
1382
1383 private:
1384 void scan_oops_in_oop(HeapWord* ptr);
1385 void do_yield_work();
1386 bool get_work_from_overflow_stack();
1387 };
1388
1389 // The following closures are used to do certain kinds of verification of
1390 // CMS marking.
1391 class PushAndMarkVerifyClosure: public OopClosure {
1392 CMSCollector* _collector;
1393 MemRegion _span;
1394 CMSBitMap* _verification_bm;
1395 CMSBitMap* _cms_bm;
1396 CMSMarkStack* _mark_stack;
1397 protected:
1398 void do_oop(oop p);
1399 template <class T> inline void do_oop_work(T *p) {
1400 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
1401 do_oop(obj);
1402 }
1403 public:
1404 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1405 MemRegion span,
1406 CMSBitMap* verification_bm,
1407 CMSBitMap* cms_bm,
1408 CMSMarkStack* mark_stack);
1409 void do_oop(oop* p);
1410 void do_oop(narrowOop* p);
1411 // Deal with a stack overflow condition
1412 void handle_stack_overflow(HeapWord* lost);
1413 };
1414
1415 class MarkFromRootsVerifyClosure: public BitMapClosure {
1416 CMSCollector* _collector;
1417 MemRegion _span;
1418 CMSBitMap* _verification_bm;
1419 CMSBitMap* _cms_bm;
1420 CMSMarkStack* _mark_stack;
1421 HeapWord* _finger;
1422 PushAndMarkVerifyClosure _pam_verify_closure;
1423 public:
1424 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1425 CMSBitMap* verification_bm,
1426 CMSBitMap* cms_bm,
1427 CMSMarkStack* mark_stack);
1428 bool do_bit(size_t offset);
1429 void reset(HeapWord* addr);
1430 };
1431
1432
1433 // This closure is used to check that a certain set of bits is
1434 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1435 class FalseBitMapClosure: public BitMapClosure {
1436 public:
1437 bool do_bit(size_t offset) {
1438 guarantee(false, "Should not have a 1 bit");
1439 return true;
1440 }
1441 };
1442
1443 // This closure is used during the second checkpointing phase
1444 // to rescan the marked objects on the dirty cards in the mod
1445 // union table and the card table proper. It's invoked via
1446 // MarkFromDirtyCardsClosure below. It uses either
1447 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1448 // declared in genOopClosures.hpp to accomplish some of its work.
1449 // In the parallel case the bitMap is shared, so access to
1450 // it needs to be suitably synchronized for updates by embedded
1451 // closures that update it; however, this closure itself only
1452 // reads the bit_map and because it is idempotent, is immune to
1453 // reading stale values.
1454 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1455 #ifdef ASSERT
1456 CMSCollector* _collector;
1457 MemRegion _span;
1458 union {
1459 CMSMarkStack* _mark_stack;
1460 OopTaskQueue* _work_queue;
1461 };
1462 #endif // ASSERT
1463 bool _parallel;
1464 CMSBitMap* _bit_map;
1465 union {
1466 MarkRefsIntoAndScanClosure* _scan_closure;
1467 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1468 };
1469
1470 public:
1471 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1472 MemRegion span,
1473 ReferenceProcessor* rp,
1474 CMSBitMap* bit_map,
1475 CMSMarkStack* mark_stack,
1476 CMSMarkStack* revisit_stack,
1477 MarkRefsIntoAndScanClosure* cl):
1478 #ifdef ASSERT
1479 _collector(collector),
1480 _span(span),
1481 _mark_stack(mark_stack),
1482 #endif // ASSERT
1483 _parallel(false),
1484 _bit_map(bit_map),
1485 _scan_closure(cl) { }
1486
1487 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1488 MemRegion span,
1489 ReferenceProcessor* rp,
1490 CMSBitMap* bit_map,
1491 OopTaskQueue* work_queue,
1492 CMSMarkStack* revisit_stack,
1493 Par_MarkRefsIntoAndScanClosure* cl):
1494 #ifdef ASSERT
1495 _collector(collector),
1496 _span(span),
1497 _work_queue(work_queue),
1498 #endif // ASSERT
1499 _parallel(true),
1500 _bit_map(bit_map),
1501 _par_scan_closure(cl) { }
1502
1503 void do_object(oop obj) {
1504 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1505 }
1506 bool do_object_b(oop obj) {
1507 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1508 return false;
1509 }
1510 bool do_object_bm(oop p, MemRegion mr);
1511 };
1512
1513 // This closure is used during the second checkpointing phase
1514 // to rescan the marked objects on the dirty cards in the mod
1515 // union table and the card table proper. It invokes
1516 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1517 // In the parallel case, the bit map is shared and requires
1518 // synchronized access.
1519 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1520 CompactibleFreeListSpace* _space;
1521 ScanMarkedObjectsAgainClosure _scan_cl;
1522 size_t _num_dirty_cards;
1523
1524 public:
1525 MarkFromDirtyCardsClosure(CMSCollector* collector,
1526 MemRegion span,
1527 CompactibleFreeListSpace* space,
1528 CMSBitMap* bit_map,
1529 CMSMarkStack* mark_stack,
1530 CMSMarkStack* revisit_stack,
1531 MarkRefsIntoAndScanClosure* cl):
1532 _space(space),
1533 _num_dirty_cards(0),
1534 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1535 mark_stack, revisit_stack, cl) { }
1536
1537 MarkFromDirtyCardsClosure(CMSCollector* collector,
1538 MemRegion span,
1539 CompactibleFreeListSpace* space,
1540 CMSBitMap* bit_map,
1541 OopTaskQueue* work_queue,
1542 CMSMarkStack* revisit_stack,
1543 Par_MarkRefsIntoAndScanClosure* cl):
1544 _space(space),
1545 _num_dirty_cards(0),
1546 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1547 work_queue, revisit_stack, cl) { }
1548
1549 void do_MemRegion(MemRegion mr);
1550 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1551 size_t num_dirty_cards() { return _num_dirty_cards; }
1552 };
1553
1554 // This closure is used in the non-product build to check
1555 // that there are no MemRegions with a certain property.
1556 class FalseMemRegionClosure: public MemRegionClosure {
1557 void do_MemRegion(MemRegion mr) {
1558 guarantee(!mr.is_empty(), "Shouldn't be empty");
1559 guarantee(false, "Should never be here");
1560 }
1561 };
1562
1563 // This closure is used during the precleaning phase
1564 // to "carefully" rescan marked objects on dirty cards.
1565 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1566 // to accomplish some of its work.
1567 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1568 CMSCollector* _collector;
1569 MemRegion _span;
1570 bool _yield;
1571 Mutex* _freelistLock;
1572 CMSBitMap* _bitMap;
1573 CMSMarkStack* _markStack;
1574 MarkRefsIntoAndScanClosure* _scanningClosure;
1575
1576 public:
1577 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1578 MemRegion span,
1579 CMSBitMap* bitMap,
1580 CMSMarkStack* markStack,
1581 CMSMarkStack* revisitStack,
1582 MarkRefsIntoAndScanClosure* cl,
1583 bool should_yield):
1584 _collector(collector),
1585 _span(span),
1586 _yield(should_yield),
1587 _bitMap(bitMap),
1588 _markStack(markStack),
1589 _scanningClosure(cl) {
1590 }
1591
1592 void do_object(oop p) {
1593 guarantee(false, "call do_object_careful instead");
1594 }
1595
1596 size_t do_object_careful(oop p) {
1597 guarantee(false, "Unexpected caller");
1598 return 0;
1599 }
1600
1601 size_t do_object_careful_m(oop p, MemRegion mr);
1602
1603 void setFreelistLock(Mutex* m) {
1604 _freelistLock = m;
1605 _scanningClosure->set_freelistLock(m);
1606 }
1607
1608 private:
1609 inline bool do_yield_check();
1610
1611 void do_yield_work();
1612 };
1613
1614 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1615 CMSCollector* _collector;
1616 MemRegion _span;
1617 bool _yield;
1618 CMSBitMap* _bit_map;
1619 CMSMarkStack* _mark_stack;
1620 PushAndMarkClosure* _scanning_closure;
1621 unsigned int _before_count;
1622
1623 public:
1624 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1625 MemRegion span,
1626 CMSBitMap* bit_map,
1627 CMSMarkStack* mark_stack,
1628 PushAndMarkClosure* cl,
1629 unsigned int before_count,
1630 bool should_yield):
1631 _collector(collector),
1632 _span(span),
1633 _yield(should_yield),
1634 _bit_map(bit_map),
1635 _mark_stack(mark_stack),
1636 _scanning_closure(cl),
1637 _before_count(before_count)
1638 { }
1639
1640 void do_object(oop p) {
1641 guarantee(false, "call do_object_careful instead");
1642 }
1643
1644 size_t do_object_careful(oop p);
1645
1646 size_t do_object_careful_m(oop p, MemRegion mr) {
1647 guarantee(false, "Unexpected caller");
1648 return 0;
1649 }
1650
1651 private:
1652 inline void do_yield_check();
1653 void do_yield_work();
1654 };
1655
1656 // This closure is used to accomplish the sweeping work
1657 // after the second checkpoint but before the concurrent reset
1658 // phase.
1659 //
1660 // Terminology
1661 // left hand chunk (LHC) - block of one or more chunks currently being
1662 // coalesced. The LHC is available for coalescing with a new chunk.
1663 // right hand chunk (RHC) - block that is currently being swept that is
1664 // free or garbage that can be coalesced with the LHC.
1665 // _inFreeRange is true if there is currently a LHC
1666 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1667 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1668 // _freeFinger is the address of the current LHC
1669 class SweepClosure: public BlkClosureCareful {
1670 CMSCollector* _collector; // collector doing the work
1671 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1672 CompactibleFreeListSpace* _sp; // Space being swept
1673 HeapWord* _limit;
1674 Mutex* _freelistLock; // Free list lock (in space)
1675 CMSBitMap* _bitMap; // Marking bit map (in
1676 // generation)
1677 bool _inFreeRange; // Indicates if we are in the
1678 // midst of a free run
1679 bool _freeRangeInFreeLists;
1680 // Often, we have just found
1681 // a free chunk and started
1682 // a new free range; we do not
1683 // eagerly remove this chunk from
1684 // the free lists unless there is
1685 // a possibility of coalescing.
1686 // When true, this flag indicates
1687 // that the _freeFinger below
1688 // points to a potentially free chunk
1689 // that may still be in the free lists
1690 bool _lastFreeRangeCoalesced;
1691 // free range contains chunks
1692 // coalesced
1693 bool _yield;
1694 // Whether sweeping should be
1695 // done with yields. For instance
1696 // when done by the foreground
1697 // collector we shouldn't yield.
1698 HeapWord* _freeFinger; // When _inFreeRange is set, the
1699 // pointer to the "left hand
1700 // chunk"
1701 size_t _freeRangeSize;
1702 // When _inFreeRange is set, this
1703 // indicates the accumulated size
1704 // of the "left hand chunk"
1705 NOT_PRODUCT(
1706 size_t _numObjectsFreed;
1707 size_t _numWordsFreed;
1708 size_t _numObjectsLive;
1709 size_t _numWordsLive;
1710 size_t _numObjectsAlreadyFree;
1711 size_t _numWordsAlreadyFree;
1712 FreeChunk* _last_fc;
1713 )
1714 private:
1715 // Code that is common to a free chunk or garbage when
1716 // encountered during sweeping.
1717 void doPostIsFreeOrGarbageChunk(FreeChunk *fc,
1718 size_t chunkSize);
1719 // Process a free chunk during sweeping.
1720 void doAlreadyFreeChunk(FreeChunk *fc);
1721 // Process a garbage chunk during sweeping.
1722 size_t doGarbageChunk(FreeChunk *fc);
1723 // Process a live chunk during sweeping.
1724 size_t doLiveChunk(FreeChunk* fc);
1725
1726 // Accessors.
1727 HeapWord* freeFinger() const { return _freeFinger; }
1728 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1729 size_t freeRangeSize() const { return _freeRangeSize; }
1730 void set_freeRangeSize(size_t v) { _freeRangeSize = v; }
1731 bool inFreeRange() const { return _inFreeRange; }
1732 void set_inFreeRange(bool v) { _inFreeRange = v; }
1733 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1734 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1735 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1736 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1737
1738 // Initialize a free range.
1739 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1740 // Return this chunk to the free lists.
1741 void flushCurFreeChunk(HeapWord* chunk, size_t size);
1742
1743 // Check if we should yield and do so when necessary.
1744 inline void do_yield_check(HeapWord* addr);
1745
1746 // Yield
1747 void do_yield_work(HeapWord* addr);
1748
1749 // Debugging/Printing
1750 void record_free_block_coalesced(FreeChunk* fc) const PRODUCT_RETURN;
1751
1752 public:
1753 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1754 CMSBitMap* bitMap, bool should_yield);
1755 ~SweepClosure();
1756
1757 size_t do_blk_careful(HeapWord* addr);
1758 };
1759
1760 // Closures related to weak references processing
1761
1762 // During CMS' weak reference processing, this is a
1763 // work-routine/closure used to complete transitive
1764 // marking of objects as live after a certain point
1765 // in which an initial set has been completely accumulated.
1766 // This closure is currently used both during the final
1767 // remark stop-world phase, as well as during the concurrent
1768 // precleaning of the discovered reference lists.
1769 class CMSDrainMarkingStackClosure: public VoidClosure {
1770 CMSCollector* _collector;
1771 MemRegion _span;
1772 CMSMarkStack* _mark_stack;
1773 CMSBitMap* _bit_map;
1774 CMSKeepAliveClosure* _keep_alive;
1775 bool _concurrent_precleaning;
1776 public:
1777 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1778 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1779 CMSKeepAliveClosure* keep_alive,
1780 bool cpc):
1781 _collector(collector),
1782 _span(span),
1783 _bit_map(bit_map),
1784 _mark_stack(mark_stack),
1785 _keep_alive(keep_alive),
1786 _concurrent_precleaning(cpc) {
1787 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1788 "Mismatch");
1789 }
1790
1791 void do_void();
1792 };
1793
1794 // A parallel version of CMSDrainMarkingStackClosure above.
1795 class CMSParDrainMarkingStackClosure: public VoidClosure {
1796 CMSCollector* _collector;
1797 MemRegion _span;
1798 OopTaskQueue* _work_queue;
1799 CMSBitMap* _bit_map;
1800 CMSInnerParMarkAndPushClosure _mark_and_push;
1801
1802 public:
1803 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1804 MemRegion span, CMSBitMap* bit_map,
1805 CMSMarkStack* revisit_stack,
1806 OopTaskQueue* work_queue):
1807 _collector(collector),
1808 _span(span),
1809 _bit_map(bit_map),
1810 _work_queue(work_queue),
1811 _mark_and_push(collector, span, bit_map, revisit_stack, work_queue) { }
1812
1813 public:
1814 void trim_queue(uint max);
1815 void do_void();
1816 };
1817
1818 // Allow yielding or short-circuiting of reference list
1819 // prelceaning work.
1820 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1821 CMSCollector* _collector;
1822 void do_yield_work();
1823 public:
1824 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1825 _collector(collector) {}
1826 virtual bool should_return();
1827 };
1828
1829
1830 // Convenience class that locks free list locks for given CMS collector
1831 class FreelistLocker: public StackObj {
1832 private:
1833 CMSCollector* _collector;
1834 public:
1835 FreelistLocker(CMSCollector* collector):
1836 _collector(collector) {
1837 _collector->getFreelistLocks();
1838 }
1839
1840 ~FreelistLocker() {
1841 _collector->releaseFreelistLocks();
1842 }
1843 };
1844
1845 // Mark all dead objects in a given space.
1846 class MarkDeadObjectsClosure: public BlkClosure {
1847 const CMSCollector* _collector;
1848 const CompactibleFreeListSpace* _sp;
1849 CMSBitMap* _live_bit_map;
1850 CMSBitMap* _dead_bit_map;
1851 public:
1852 MarkDeadObjectsClosure(const CMSCollector* collector,
1853 const CompactibleFreeListSpace* sp,
1854 CMSBitMap *live_bit_map,
1855 CMSBitMap *dead_bit_map) :
1856 _collector(collector),
1857 _sp(sp),
1858 _live_bit_map(live_bit_map),
1859 _dead_bit_map(dead_bit_map) {}
1860 size_t do_blk(HeapWord* addr);
1861 };
1862
1863 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1864
1865 public:
1866 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase);
1867 TraceCMSMemoryManagerStats();
1868 };
1869