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.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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 "runtime/mutexLocker.hpp"
36 #include "runtime/virtualspace.hpp"
37 #include "services/memoryService.hpp"
38 #include "utilities/bitMap.inline.hpp"
39 #include "utilities/stack.inline.hpp"
40 #include "utilities/taskqueue.hpp"
41 #include "utilities/yieldingWorkgroup.hpp"
42
43 // ConcurrentMarkSweepGeneration is in support of a concurrent
44 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
45 // style. We assume, for now, that this generation is always the
46 // seniormost generation and for simplicity
47 // in the first implementation, that this generation is a single compactible
48 // space. Neither of these restrictions appears essential, and will be
49 // relaxed in the future when more time is available to implement the
50 // greater generality (and there's a need for it).
51 //
52 // Concurrent mode failures are currently handled by
53 // means of a sliding mark-compact.
54
55 class CMSAdaptiveSizePolicy;
56 class CMSConcMarkingTask;
57 class CMSGCAdaptivePolicyCounters;
58 class CMSTracer;
59 class ConcurrentGCTimer;
60 class ConcurrentMarkSweepGeneration;
61 class ConcurrentMarkSweepPolicy;
62 class ConcurrentMarkSweepThread;
63 class CompactibleFreeListSpace;
64 class FreeChunk;
65 class PromotionInfo;
66 class ScanMarkedObjectsAgainCarefullyClosure;
67 class TenuredGeneration;
68 class SerialOldTracer;
69
70 // A generic CMS bit map. It's the basis for both the CMS marking bit map
71 // as well as for the mod union table (in each case only a subset of the
72 // methods are used). This is essentially a wrapper around the BitMap class,
73 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
74 // we have _shifter == 0. and for the mod union table we have
75 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
76 // XXX 64-bit issues in BitMap?
77 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
78 friend class VMStructs;
79
80 HeapWord* _bmStartWord; // base address of range covered by map
81 size_t _bmWordSize; // map size (in #HeapWords covered)
82 const int _shifter; // shifts to convert HeapWord to bit position
83 VirtualSpace _virtual_space; // underlying the bit map
84 BitMap _bm; // the bit map itself
85 public:
86 Mutex* const _lock; // mutex protecting _bm;
87
88 public:
89 // constructor
90 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
91
92 // allocates the actual storage for the map
93 bool allocate(MemRegion mr);
94 // field getter
95 Mutex* lock() const { return _lock; }
96 // locking verifier convenience function
97 void assert_locked() const PRODUCT_RETURN;
98
99 // inquiries
100 HeapWord* startWord() const { return _bmStartWord; }
101 size_t sizeInWords() const { return _bmWordSize; }
102 size_t sizeInBits() const { return _bm.size(); }
103 // the following is one past the last word in space
104 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
105
106 // reading marks
107 bool isMarked(HeapWord* addr) const;
108 bool par_isMarked(HeapWord* addr) const; // do not lock checks
109 bool isUnmarked(HeapWord* addr) const;
110 bool isAllClear() const;
111
112 // writing marks
113 void mark(HeapWord* addr);
114 // For marking by parallel GC threads;
115 // returns true if we did, false if another thread did
116 bool par_mark(HeapWord* addr);
117
118 void mark_range(MemRegion mr);
119 void par_mark_range(MemRegion mr);
120 void mark_large_range(MemRegion mr);
121 void par_mark_large_range(MemRegion mr);
122 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
123 void clear_range(MemRegion mr);
124 void par_clear_range(MemRegion mr);
125 void clear_large_range(MemRegion mr);
126 void par_clear_large_range(MemRegion mr);
127 void clear_all();
128 void clear_all_incrementally(); // Not yet implemented!!
129
130 NOT_PRODUCT(
131 // checks the memory region for validity
132 void region_invariant(MemRegion mr);
133 )
134
135 // iteration
136 void iterate(BitMapClosure* cl) {
137 _bm.iterate(cl);
138 }
139 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
140 void dirty_range_iterate_clear(MemRegionClosure* cl);
141 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
142
143 // auxiliary support for iteration
144 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
145 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
146 HeapWord* end_addr) const;
147 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
148 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
149 HeapWord* end_addr) const;
150 MemRegion getAndClearMarkedRegion(HeapWord* addr);
151 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
152 HeapWord* end_addr);
153
154 // conversion utilities
155 HeapWord* offsetToHeapWord(size_t offset) const;
156 size_t heapWordToOffset(HeapWord* addr) const;
157 size_t heapWordDiffToOffsetDiff(size_t diff) const;
158
159 void print_on_error(outputStream* st, const char* prefix) const;
160
161 // debugging
162 // is this address range covered by the bit-map?
163 NOT_PRODUCT(
164 bool covers(MemRegion mr) const;
165 bool covers(HeapWord* start, size_t size = 0) const;
166 )
167 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
168 };
169
170 // Represents a marking stack used by the CMS collector.
171 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
172 class CMSMarkStack: public CHeapObj<mtGC> {
173 //
174 friend class CMSCollector; // To get at expansion stats further below.
175 //
176
177 VirtualSpace _virtual_space; // Space for the stack
178 oop* _base; // Bottom of stack
179 size_t _index; // One more than last occupied index
180 size_t _capacity; // Max #elements
181 Mutex _par_lock; // An advisory lock used in case of parallel access
182 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run
183
184 protected:
185 size_t _hit_limit; // We hit max stack size limit
186 size_t _failed_double; // We failed expansion before hitting limit
187
188 public:
189 CMSMarkStack():
190 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
191 _hit_limit(0),
192 _failed_double(0) {}
193
194 bool allocate(size_t size);
195
196 size_t capacity() const { return _capacity; }
197
198 oop pop() {
199 if (!isEmpty()) {
200 return _base[--_index] ;
201 }
202 return NULL;
203 }
204
205 bool push(oop ptr) {
206 if (isFull()) {
207 return false;
208 } else {
209 _base[_index++] = ptr;
210 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
211 return true;
212 }
213 }
214
215 bool isEmpty() const { return _index == 0; }
216 bool isFull() const {
217 assert(_index <= _capacity, "buffer overflow");
218 return _index == _capacity;
219 }
220
221 size_t length() { return _index; }
222
223 // "Parallel versions" of some of the above
224 oop par_pop() {
225 // lock and pop
226 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
227 return pop();
228 }
229
230 bool par_push(oop ptr) {
231 // lock and push
232 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
233 return push(ptr);
234 }
235
236 // Forcibly reset the stack, losing all of its contents.
237 void reset() {
238 _index = 0;
239 }
240
241 // Expand the stack, typically in response to an overflow condition.
242 void expand();
243
244 // Compute the least valued stack element.
245 oop least_value(HeapWord* low) {
246 oop least = (oop)low;
247 for (size_t i = 0; i < _index; i++) {
248 least = MIN2(least, _base[i]);
249 }
250 return least;
251 }
252
253 // Exposed here to allow stack expansion in || case.
254 Mutex* par_lock() { return &_par_lock; }
255 };
256
257 class CardTableRS;
258 class CMSParGCThreadState;
259
260 class ModUnionClosure: public MemRegionClosure {
261 protected:
262 CMSBitMap* _t;
263 public:
264 ModUnionClosure(CMSBitMap* t): _t(t) { }
265 void do_MemRegion(MemRegion mr);
266 };
267
268 class ModUnionClosurePar: public ModUnionClosure {
269 public:
270 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
271 void do_MemRegion(MemRegion mr);
272 };
273
274 // Survivor Chunk Array in support of parallelization of
275 // Survivor Space rescan.
276 class ChunkArray: public CHeapObj<mtGC> {
277 size_t _index;
278 size_t _capacity;
279 size_t _overflows;
280 HeapWord** _array; // storage for array
281
282 public:
283 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
284 ChunkArray(HeapWord** a, size_t c):
285 _index(0), _capacity(c), _overflows(0), _array(a) {}
286
287 HeapWord** array() { return _array; }
288 void set_array(HeapWord** a) { _array = a; }
289
290 size_t capacity() { return _capacity; }
291 void set_capacity(size_t c) { _capacity = c; }
292
293 size_t end() {
294 assert(_index <= capacity(),
295 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
296 _index, _capacity));
297 return _index;
298 } // exclusive
299
300 HeapWord* nth(size_t n) {
301 assert(n < end(), "Out of bounds access");
302 return _array[n];
303 }
304
305 void reset() {
306 _index = 0;
307 if (_overflows > 0 && PrintCMSStatistics > 1) {
308 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
309 _capacity, _overflows);
310 }
311 _overflows = 0;
312 }
313
314 void record_sample(HeapWord* p, size_t sz) {
315 // For now we do not do anything with the size
316 if (_index < _capacity) {
317 _array[_index++] = p;
318 } else {
319 ++_overflows;
320 assert(_index == _capacity,
321 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
322 "): out of bounds at overflow#" SIZE_FORMAT,
323 _index, _capacity, _overflows));
324 }
325 }
326 };
327
328 //
329 // Timing, allocation and promotion statistics for gc scheduling and incremental
330 // mode pacing. Most statistics are exponential averages.
331 //
332 class CMSStats VALUE_OBJ_CLASS_SPEC {
333 private:
334 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
335
336 // The following are exponential averages with factor alpha:
337 // avg = (100 - alpha) * avg + alpha * cur_sample
338 //
339 // The durations measure: end_time[n] - start_time[n]
340 // The periods measure: start_time[n] - start_time[n-1]
341 //
342 // The cms period and duration include only concurrent collections; time spent
343 // in foreground cms collections due to System.gc() or because of a failure to
344 // keep up are not included.
345 //
346 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
347 // real value, but is used only after the first period. A value of 100 is
348 // used for the first sample so it gets the entire weight.
349 unsigned int _saved_alpha; // 0-100
350 unsigned int _gc0_alpha;
351 unsigned int _cms_alpha;
352
353 double _gc0_duration;
354 double _gc0_period;
355 size_t _gc0_promoted; // bytes promoted per gc0
356 double _cms_duration;
357 double _cms_duration_pre_sweep; // time from initiation to start of sweep
358 double _cms_duration_per_mb;
359 double _cms_period;
360 size_t _cms_allocated; // bytes of direct allocation per gc0 period
361
362 // Timers.
363 elapsedTimer _cms_timer;
364 TimeStamp _gc0_begin_time;
365 TimeStamp _cms_begin_time;
366 TimeStamp _cms_end_time;
367
368 // Snapshots of the amount used in the CMS generation.
369 size_t _cms_used_at_gc0_begin;
370 size_t _cms_used_at_gc0_end;
371 size_t _cms_used_at_cms_begin;
372
373 // Used to prevent the duty cycle from being reduced in the middle of a cms
374 // cycle.
375 bool _allow_duty_cycle_reduction;
376
377 enum {
378 _GC0_VALID = 0x1,
379 _CMS_VALID = 0x2,
380 _ALL_VALID = _GC0_VALID | _CMS_VALID
381 };
382
383 unsigned int _valid_bits;
384
385 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
386
387 protected:
388
389 // Return a duty cycle that avoids wild oscillations, by limiting the amount
390 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
391 // as a recommended value).
392 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
393 unsigned int new_duty_cycle);
394 unsigned int icms_update_duty_cycle_impl();
395
396 // In support of adjusting of cms trigger ratios based on history
397 // of concurrent mode failure.
398 double cms_free_adjustment_factor(size_t free) const;
399 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
400
401 public:
402 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
403 unsigned int alpha = CMSExpAvgFactor);
404
405 // Whether or not the statistics contain valid data; higher level statistics
406 // cannot be called until this returns true (they require at least one young
407 // gen and one cms cycle to have completed).
408 bool valid() const;
409
410 // Record statistics.
411 void record_gc0_begin();
412 void record_gc0_end(size_t cms_gen_bytes_used);
413 void record_cms_begin();
414 void record_cms_end();
415
416 // Allow management of the cms timer, which must be stopped/started around
417 // yield points.
418 elapsedTimer& cms_timer() { return _cms_timer; }
419 void start_cms_timer() { _cms_timer.start(); }
420 void stop_cms_timer() { _cms_timer.stop(); }
421
422 // Basic statistics; units are seconds or bytes.
423 double gc0_period() const { return _gc0_period; }
424 double gc0_duration() const { return _gc0_duration; }
425 size_t gc0_promoted() const { return _gc0_promoted; }
426 double cms_period() const { return _cms_period; }
427 double cms_duration() const { return _cms_duration; }
428 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
429 size_t cms_allocated() const { return _cms_allocated; }
430
431 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
432
433 // Seconds since the last background cms cycle began or ended.
434 double cms_time_since_begin() const;
435 double cms_time_since_end() const;
436
437 // Higher level statistics--caller must check that valid() returns true before
438 // calling.
439
440 // Returns bytes promoted per second of wall clock time.
441 double promotion_rate() const;
442
443 // Returns bytes directly allocated per second of wall clock time.
444 double cms_allocation_rate() const;
445
446 // Rate at which space in the cms generation is being consumed (sum of the
447 // above two).
448 double cms_consumption_rate() const;
449
450 // Returns an estimate of the number of seconds until the cms generation will
451 // fill up, assuming no collection work is done.
452 double time_until_cms_gen_full() const;
453
454 // Returns an estimate of the number of seconds remaining until
455 // the cms generation collection should start.
456 double time_until_cms_start() const;
457
458 // End of higher level statistics.
459
460 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
461 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
462
463 // Update the duty cycle and return the new value.
464 unsigned int icms_update_duty_cycle();
465
466 // Debugging.
467 void print_on(outputStream* st) const PRODUCT_RETURN;
468 void print() const { print_on(gclog_or_tty); }
469 };
470
471 // A closure related to weak references processing which
472 // we embed in the CMSCollector, since we need to pass
473 // it to the reference processor for secondary filtering
474 // of references based on reachability of referent;
475 // see role of _is_alive_non_header closure in the
476 // ReferenceProcessor class.
477 // For objects in the CMS generation, this closure checks
478 // if the object is "live" (reachable). Used in weak
479 // reference processing.
480 class CMSIsAliveClosure: public BoolObjectClosure {
481 const MemRegion _span;
482 const CMSBitMap* _bit_map;
483
484 friend class CMSCollector;
485 public:
486 CMSIsAliveClosure(MemRegion span,
487 CMSBitMap* bit_map):
488 _span(span),
489 _bit_map(bit_map) {
490 assert(!span.is_empty(), "Empty span could spell trouble");
491 }
492
493 bool do_object_b(oop obj);
494 };
495
496
497 // Implements AbstractRefProcTaskExecutor for CMS.
498 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
499 public:
500
501 CMSRefProcTaskExecutor(CMSCollector& collector)
502 : _collector(collector)
503 { }
504
505 // Executes a task using worker threads.
506 virtual void execute(ProcessTask& task);
507 virtual void execute(EnqueueTask& task);
508 private:
509 CMSCollector& _collector;
510 };
511
512
513 class CMSCollector: public CHeapObj<mtGC> {
514 friend class VMStructs;
515 friend class ConcurrentMarkSweepThread;
516 friend class ConcurrentMarkSweepGeneration;
517 friend class CompactibleFreeListSpace;
518 friend class CMSParMarkTask;
519 friend class CMSParInitialMarkTask;
520 friend class CMSParRemarkTask;
521 friend class CMSConcMarkingTask;
522 friend class CMSRefProcTaskProxy;
523 friend class CMSRefProcTaskExecutor;
524 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
525 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
526 friend class PushOrMarkClosure; // to access _restart_addr
527 friend class Par_PushOrMarkClosure; // to access _restart_addr
528 friend class MarkFromRootsClosure; // -- ditto --
529 // ... and for clearing cards
530 friend class Par_MarkFromRootsClosure; // to access _restart_addr
531 // ... and for clearing cards
532 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
533 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
534 friend class PushAndMarkVerifyClosure; // -- ditto --
535 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
536 friend class PushAndMarkClosure; // -- ditto --
537 friend class Par_PushAndMarkClosure; // -- ditto --
538 friend class CMSKeepAliveClosure; // -- ditto --
539 friend class CMSDrainMarkingStackClosure; // -- ditto --
540 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
541 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
542 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
543 friend class VM_CMS_Operation;
544 friend class VM_CMS_Initial_Mark;
545 friend class VM_CMS_Final_Remark;
546 friend class TraceCMSMemoryManagerStats;
547
548 private:
549 jlong _time_of_last_gc;
550 void update_time_of_last_gc(jlong now) {
551 _time_of_last_gc = now;
552 }
553
554 OopTaskQueueSet* _task_queues;
555
556 // Overflow list of grey objects, threaded through mark-word
557 // Manipulated with CAS in the parallel/multi-threaded case.
558 oop _overflow_list;
559 // The following array-pair keeps track of mark words
560 // displaced for accommodating overflow list above.
561 // This code will likely be revisited under RFE#4922830.
562 Stack<oop, mtGC> _preserved_oop_stack;
563 Stack<markOop, mtGC> _preserved_mark_stack;
564
565 int* _hash_seed;
566
567 // In support of multi-threaded concurrent phases
568 YieldingFlexibleWorkGang* _conc_workers;
569
570 // Performance Counters
571 CollectorCounters* _gc_counters;
572
573 // Initialization Errors
574 bool _completed_initialization;
575
576 // In support of ExplicitGCInvokesConcurrent
577 static bool _full_gc_requested;
578 static GCCause::Cause _full_gc_cause;
579 unsigned int _collection_count_start;
580
581 // Should we unload classes this concurrent cycle?
582 bool _should_unload_classes;
583 unsigned int _concurrent_cycles_since_last_unload;
584 unsigned int concurrent_cycles_since_last_unload() const {
585 return _concurrent_cycles_since_last_unload;
586 }
587 // Did we (allow) unload classes in the previous concurrent cycle?
588 bool unloaded_classes_last_cycle() const {
589 return concurrent_cycles_since_last_unload() == 0;
590 }
591 // Root scanning options for perm gen
592 int _roots_scanning_options;
593 int roots_scanning_options() const { return _roots_scanning_options; }
594 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
595 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
596
597 // Verification support
598 CMSBitMap _verification_mark_bm;
599 void verify_after_remark_work_1();
600 void verify_after_remark_work_2();
601
602 // True if any verification flag is on.
603 bool _verifying;
604 bool verifying() const { return _verifying; }
605 void set_verifying(bool v) { _verifying = v; }
606
607 // Collector policy
608 ConcurrentMarkSweepPolicy* _collector_policy;
609 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
610
611 void set_did_compact(bool v);
612
613 // XXX Move these to CMSStats ??? FIX ME !!!
614 elapsedTimer _inter_sweep_timer; // Time between sweeps
615 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
616 // Padded decaying average estimates of the above
617 AdaptivePaddedAverage _inter_sweep_estimate;
618 AdaptivePaddedAverage _intra_sweep_estimate;
619
620 CMSTracer* _gc_tracer_cm;
621 ConcurrentGCTimer* _gc_timer_cm;
622
623 bool _cms_start_registered;
624
625 GCHeapSummary _last_heap_summary;
626 MetaspaceSummary _last_metaspace_summary;
627
628 MetaspaceChunkFreeListSummary _last_metaspace_free_list_summaries[Metaspace::MetadataTypeCount];
629
630 void register_foreground_gc_start(GCCause::Cause cause);
631 void register_gc_start(GCCause::Cause cause);
632 void register_gc_end();
633 void save_heap_summary();
634 void report_heap_summary(GCWhen::Type when);
635
636 protected:
637 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
638 MemRegion _span; // Span covering above two
639 CardTableRS* _ct; // Card table
640
641 // CMS marking support structures
642 CMSBitMap _markBitMap;
643 CMSBitMap _modUnionTable;
644 CMSMarkStack _markStack;
645
646 HeapWord* _restart_addr; // In support of marking stack overflow
647 void lower_restart_addr(HeapWord* low);
648
649 // Counters in support of marking stack / work queue overflow handling:
650 // a non-zero value indicates certain types of overflow events during
651 // the current CMS cycle and could lead to stack resizing efforts at
652 // an opportune future time.
653 size_t _ser_pmc_preclean_ovflw;
654 size_t _ser_pmc_remark_ovflw;
655 size_t _par_pmc_remark_ovflw;
656 size_t _ser_kac_preclean_ovflw;
657 size_t _ser_kac_ovflw;
658 size_t _par_kac_ovflw;
659 NOT_PRODUCT(ssize_t _num_par_pushes;)
660
661 // ("Weak") Reference processing support.
662 ReferenceProcessor* _ref_processor;
663 CMSIsAliveClosure _is_alive_closure;
664 // Keep this textually after _markBitMap and _span; c'tor dependency.
665
666 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
667 ModUnionClosure _modUnionClosure;
668 ModUnionClosurePar _modUnionClosurePar;
669
670 // CMS abstract state machine
671 // initial_state: Idling
672 // next_state(Idling) = {Marking}
673 // next_state(Marking) = {Precleaning, Sweeping}
674 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
675 // next_state(AbortablePreclean) = {FinalMarking}
676 // next_state(FinalMarking) = {Sweeping}
677 // next_state(Sweeping) = {Resizing}
678 // next_state(Resizing) = {Resetting}
679 // next_state(Resetting) = {Idling}
680 // The numeric values below are chosen so that:
681 // . _collectorState <= Idling == post-sweep && pre-mark
682 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
683 // precleaning || abortablePrecleanb
684 public:
685 enum CollectorState {
686 Resizing = 0,
687 Resetting = 1,
688 Idling = 2,
689 InitialMarking = 3,
690 Marking = 4,
691 Precleaning = 5,
692 AbortablePreclean = 6,
693 FinalMarking = 7,
694 Sweeping = 8
695 };
696 protected:
697 static CollectorState _collectorState;
698
699 // State related to prologue/epilogue invocation for my generations
700 bool _between_prologue_and_epilogue;
701
702 // Signaling/State related to coordination between fore- and background GC
703 // Note: When the baton has been passed from background GC to foreground GC,
704 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
705 static bool _foregroundGCIsActive; // true iff foreground collector is active or
706 // wants to go active
707 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
708 // yet passed the baton to the foreground GC
709
710 // Support for CMSScheduleRemark (abortable preclean)
711 bool _abort_preclean;
712 bool _start_sampling;
713
714 int _numYields;
715 size_t _numDirtyCards;
716 size_t _sweep_count;
717 // Number of full gc's since the last concurrent gc.
718 uint _full_gcs_since_conc_gc;
719
720 // Occupancy used for bootstrapping stats
721 double _bootstrap_occupancy;
722
723 // Timer
724 elapsedTimer _timer;
725
726 // Timing, allocation and promotion statistics, used for scheduling.
727 CMSStats _stats;
728
729 // Allocation limits installed in the young gen, used only in
730 // CMSIncrementalMode. When an allocation in the young gen would cross one of
731 // these limits, the cms generation is notified and the cms thread is started
732 // or stopped, respectively.
733 HeapWord* _icms_start_limit;
734 HeapWord* _icms_stop_limit;
735
736 enum CMS_op_type {
737 CMS_op_checkpointRootsInitial,
738 CMS_op_checkpointRootsFinal
739 };
740
741 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
742 bool stop_world_and_do(CMS_op_type op);
743
744 OopTaskQueueSet* task_queues() { return _task_queues; }
745 int* hash_seed(int i) { return &_hash_seed[i]; }
746 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
747
748 // Support for parallelizing Eden rescan in CMS remark phase
749 void sample_eden(); // ... sample Eden space top
750
751 private:
752 // Support for parallelizing young gen rescan in CMS remark phase
753 Generation* _young_gen; // the younger gen
754 HeapWord** _top_addr; // ... Top of Eden
755 HeapWord** _end_addr; // ... End of Eden
756 Mutex* _eden_chunk_lock;
757 HeapWord** _eden_chunk_array; // ... Eden partitioning array
758 size_t _eden_chunk_index; // ... top (exclusive) of array
759 size_t _eden_chunk_capacity; // ... max entries in array
760
761 // Support for parallelizing survivor space rescan
762 HeapWord** _survivor_chunk_array;
763 size_t _survivor_chunk_index;
764 size_t _survivor_chunk_capacity;
765 size_t* _cursor;
766 ChunkArray* _survivor_plab_array;
767
768 // Support for marking stack overflow handling
769 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
770 bool par_take_from_overflow_list(size_t num,
771 OopTaskQueue* to_work_q,
772 int no_of_gc_threads);
773 void push_on_overflow_list(oop p);
774 void par_push_on_overflow_list(oop p);
775 // The following is, obviously, not, in general, "MT-stable"
776 bool overflow_list_is_empty() const;
777
778 void preserve_mark_if_necessary(oop p);
779 void par_preserve_mark_if_necessary(oop p);
780 void preserve_mark_work(oop p, markOop m);
781 void restore_preserved_marks_if_any();
782 NOT_PRODUCT(bool no_preserved_marks() const;)
783 // In support of testing overflow code
784 NOT_PRODUCT(int _overflow_counter;)
785 NOT_PRODUCT(bool simulate_overflow();) // Sequential
786 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
787
788 // CMS work methods
789 void checkpointRootsInitialWork(bool asynch); // Initial checkpoint work
790
791 // A return value of false indicates failure due to stack overflow
792 bool markFromRootsWork(bool asynch); // Concurrent marking work
793
794 public: // FIX ME!!! only for testing
795 bool do_marking_st(bool asynch); // Single-threaded marking
796 bool do_marking_mt(bool asynch); // Multi-threaded marking
797
798 private:
799
800 // Concurrent precleaning work
801 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
802 ScanMarkedObjectsAgainCarefullyClosure* cl);
803 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
804 ScanMarkedObjectsAgainCarefullyClosure* cl);
805 // Does precleaning work, returning a quantity indicative of
806 // the amount of "useful work" done.
807 size_t preclean_work(bool clean_refs, bool clean_survivors);
808 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
809 void abortable_preclean(); // Preclean while looking for possible abort
810 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
811 // Helper function for above; merge-sorts the per-thread plab samples
812 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
813 // Resets (i.e. clears) the per-thread plab sample vectors
814 void reset_survivor_plab_arrays();
815
816 // Final (second) checkpoint work
817 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
818 bool init_mark_was_synchronous);
819 // Work routine for parallel version of remark
820 void do_remark_parallel();
821 // Work routine for non-parallel version of remark
822 void do_remark_non_parallel();
823 // Reference processing work routine (during second checkpoint)
824 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
825
826 // Concurrent sweeping work
827 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
828
829 // (Concurrent) resetting of support data structures
830 void reset(bool asynch);
831
832 // Clear _expansion_cause fields of constituent generations
833 void clear_expansion_cause();
834
835 // An auxiliary method used to record the ends of
836 // used regions of each generation to limit the extent of sweep
837 void save_sweep_limits();
838
839 // A work method used by foreground collection to determine
840 // what type of collection (compacting or not, continuing or fresh)
841 // it should do.
842 void decide_foreground_collection_type(bool clear_all_soft_refs,
843 bool* should_compact, bool* should_start_over);
844
845 // A work method used by the foreground collector to do
846 // a mark-sweep-compact.
847 void do_compaction_work(bool clear_all_soft_refs);
848
849 // A work method used by the foreground collector to do
850 // a mark-sweep, after taking over from a possibly on-going
851 // concurrent mark-sweep collection.
852 void do_mark_sweep_work(bool clear_all_soft_refs,
853 CollectorState first_state, bool should_start_over);
854
855 // Work methods for reporting concurrent mode interruption or failure
856 bool is_external_interruption();
857 void report_concurrent_mode_interruption();
858
859 // If the background GC is active, acquire control from the background
860 // GC and do the collection.
861 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
862
863 // For synchronizing passing of control from background to foreground
864 // GC. waitForForegroundGC() is called by the background
865 // collector. It if had to wait for a foreground collection,
866 // it returns true and the background collection should assume
867 // that the collection was finished by the foreground
868 // collector.
869 bool waitForForegroundGC();
870
871 // Incremental mode triggering: recompute the icms duty cycle and set the
872 // allocation limits in the young gen.
873 void icms_update_allocation_limits();
874
875 size_t block_size_using_printezis_bits(HeapWord* addr) const;
876 size_t block_size_if_printezis_bits(HeapWord* addr) const;
877 HeapWord* next_card_start_after_block(HeapWord* addr) const;
878
879 void setup_cms_unloading_and_verification_state();
880 public:
881 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
882 CardTableRS* ct,
883 ConcurrentMarkSweepPolicy* cp);
884 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
885
886 ReferenceProcessor* ref_processor() { return _ref_processor; }
887 void ref_processor_init();
888
889 Mutex* bitMapLock() const { return _markBitMap.lock(); }
890 static CollectorState abstract_state() { return _collectorState; }
891
892 bool should_abort_preclean() const; // Whether preclean should be aborted.
893 size_t get_eden_used() const;
894 size_t get_eden_capacity() const;
895
896 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
897
898 // Locking checks
899 NOT_PRODUCT(static bool have_cms_token();)
900
901 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
902 bool shouldConcurrentCollect();
903
904 void collect(bool full,
905 bool clear_all_soft_refs,
906 size_t size,
907 bool tlab);
908 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause);
909 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause);
910
911 // In support of ExplicitGCInvokesConcurrent
912 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
913 // Should we unload classes in a particular concurrent cycle?
914 bool should_unload_classes() const {
915 return _should_unload_classes;
916 }
917 void update_should_unload_classes();
918
919 void direct_allocated(HeapWord* start, size_t size);
920
921 // Object is dead if not marked and current phase is sweeping.
922 bool is_dead_obj(oop obj) const;
923
924 // After a promotion (of "start"), do any necessary marking.
925 // If "par", then it's being done by a parallel GC thread.
926 // The last two args indicate if we need precise marking
927 // and if so the size of the object so it can be dirtied
928 // in its entirety.
929 void promoted(bool par, HeapWord* start,
930 bool is_obj_array, size_t obj_size);
931
932 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
933 size_t word_size);
934
935 void getFreelistLocks() const;
936 void releaseFreelistLocks() const;
937 bool haveFreelistLocks() const;
938
939 // Adjust size of underlying generation
940 void compute_new_size();
941
942 // GC prologue and epilogue
943 void gc_prologue(bool full);
944 void gc_epilogue(bool full);
945
946 jlong time_of_last_gc(jlong now) {
947 if (_collectorState <= Idling) {
948 // gc not in progress
949 return _time_of_last_gc;
950 } else {
951 // collection in progress
952 return now;
953 }
954 }
955
956 // Support for parallel remark of survivor space
957 void* get_data_recorder(int thr_num);
958 void sample_eden_chunk();
959
960 CMSBitMap* markBitMap() { return &_markBitMap; }
961 void directAllocated(HeapWord* start, size_t size);
962
963 // Main CMS steps and related support
964 void checkpointRootsInitial(bool asynch);
965 bool markFromRoots(bool asynch); // a return value of false indicates failure
966 // due to stack overflow
967 void preclean();
968 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
969 bool init_mark_was_synchronous);
970 void sweep(bool asynch);
971
972 // Check that the currently executing thread is the expected
973 // one (foreground collector or background collector).
974 static void check_correct_thread_executing() PRODUCT_RETURN;
975 // XXXPERM void print_statistics() PRODUCT_RETURN;
976
977 bool is_cms_reachable(HeapWord* addr);
978
979 // Performance Counter Support
980 CollectorCounters* counters() { return _gc_counters; }
981
982 // Timer stuff
983 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
984 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
985 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
986 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
987
988 int yields() { return _numYields; }
989 void resetYields() { _numYields = 0; }
990 void incrementYields() { _numYields++; }
991 void resetNumDirtyCards() { _numDirtyCards = 0; }
992 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
993 size_t numDirtyCards() { return _numDirtyCards; }
994
995 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
996 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
997 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
998 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
999 size_t sweep_count() const { return _sweep_count; }
1000 void increment_sweep_count() { _sweep_count++; }
1001
1002 // Timers/stats for gc scheduling and incremental mode pacing.
1003 CMSStats& stats() { return _stats; }
1004
1005 // Convenience methods that check whether CMSIncrementalMode is enabled and
1006 // forward to the corresponding methods in ConcurrentMarkSweepThread.
1007 static void start_icms();
1008 static void stop_icms(); // Called at the end of the cms cycle.
1009 static void disable_icms(); // Called before a foreground collection.
1010 static void enable_icms(); // Called after a foreground collection.
1011 void icms_wait(); // Called at yield points.
1012
1013 // Adaptive size policy
1014 CMSAdaptiveSizePolicy* size_policy();
1015 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1016
1017 static void print_on_error(outputStream* st);
1018
1019 // Debugging
1020 void verify();
1021 bool verify_after_remark(bool silent = VerifySilently);
1022 void verify_ok_to_terminate() const PRODUCT_RETURN;
1023 void verify_work_stacks_empty() const PRODUCT_RETURN;
1024 void verify_overflow_empty() const PRODUCT_RETURN;
1025
1026 // Convenience methods in support of debugging
1027 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1028 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1029
1030 // Accessors
1031 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1032 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1033
1034 // Initialization errors
1035 bool completed_initialization() { return _completed_initialization; }
1036
1037 void print_eden_and_survivor_chunk_arrays();
1038 };
1039
1040 class CMSExpansionCause : public AllStatic {
1041 public:
1042 enum Cause {
1043 _no_expansion,
1044 _satisfy_free_ratio,
1045 _satisfy_promotion,
1046 _satisfy_allocation,
1047 _allocate_par_lab,
1048 _allocate_par_spooling_space,
1049 _adaptive_size_policy
1050 };
1051 // Return a string describing the cause of the expansion.
1052 static const char* to_string(CMSExpansionCause::Cause cause);
1053 };
1054
1055 class ConcurrentMarkSweepGeneration: public CardGeneration {
1056 friend class VMStructs;
1057 friend class ConcurrentMarkSweepThread;
1058 friend class ConcurrentMarkSweep;
1059 friend class CMSCollector;
1060 protected:
1061 static CMSCollector* _collector; // the collector that collects us
1062 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1063
1064 // Performance Counters
1065 GenerationCounters* _gen_counters;
1066 GSpaceCounters* _space_counters;
1067
1068 // Words directly allocated, used by CMSStats.
1069 size_t _direct_allocated_words;
1070
1071 // Non-product stat counters
1072 NOT_PRODUCT(
1073 size_t _numObjectsPromoted;
1074 size_t _numWordsPromoted;
1075 size_t _numObjectsAllocated;
1076 size_t _numWordsAllocated;
1077 )
1078
1079 // Used for sizing decisions
1080 bool _incremental_collection_failed;
1081 bool incremental_collection_failed() {
1082 return _incremental_collection_failed;
1083 }
1084 void set_incremental_collection_failed() {
1085 _incremental_collection_failed = true;
1086 }
1087 void clear_incremental_collection_failed() {
1088 _incremental_collection_failed = false;
1089 }
1090
1091 // accessors
1092 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1093 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1094
1095 private:
1096 // For parallel young-gen GC support.
1097 CMSParGCThreadState** _par_gc_thread_states;
1098
1099 // Reason generation was expanded
1100 CMSExpansionCause::Cause _expansion_cause;
1101
1102 // In support of MinChunkSize being larger than min object size
1103 const double _dilatation_factor;
1104
1105 enum CollectionTypes {
1106 Concurrent_collection_type = 0,
1107 MS_foreground_collection_type = 1,
1108 MSC_foreground_collection_type = 2,
1109 Unknown_collection_type = 3
1110 };
1111
1112 CollectionTypes _debug_collection_type;
1113
1114 // True if a compacting collection was done.
1115 bool _did_compact;
1116 bool did_compact() { return _did_compact; }
1117
1118 // Fraction of current occupancy at which to start a CMS collection which
1119 // will collect this generation (at least).
1120 double _initiating_occupancy;
1121
1122 protected:
1123 // Shrink generation by specified size (returns false if unable to shrink)
1124 void shrink_free_list_by(size_t bytes);
1125
1126 // Update statistics for GC
1127 virtual void update_gc_stats(int level, bool full);
1128
1129 // Maximum available space in the generation (including uncommitted)
1130 // space.
1131 size_t max_available() const;
1132
1133 // getter and initializer for _initiating_occupancy field.
1134 double initiating_occupancy() const { return _initiating_occupancy; }
1135 void init_initiating_occupancy(intx io, uintx tr);
1136
1137 public:
1138 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1139 int level, CardTableRS* ct,
1140 bool use_adaptive_freelists,
1141 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1142
1143 // Accessors
1144 CMSCollector* collector() const { return _collector; }
1145 static void set_collector(CMSCollector* collector) {
1146 assert(_collector == NULL, "already set");
1147 _collector = collector;
1148 }
1149 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1150
1151 Mutex* freelistLock() const;
1152
1153 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1154
1155 // Adaptive size policy
1156 CMSAdaptiveSizePolicy* size_policy();
1157
1158 void set_did_compact(bool v) { _did_compact = v; }
1159
1160 bool refs_discovery_is_atomic() const { return false; }
1161 bool refs_discovery_is_mt() const {
1162 // Note: CMS does MT-discovery during the parallel-remark
1163 // phases. Use ReferenceProcessorMTMutator to make refs
1164 // discovery MT-safe during such phases or other parallel
1165 // discovery phases in the future. This may all go away
1166 // if/when we decide that refs discovery is sufficiently
1167 // rare that the cost of the CAS's involved is in the
1168 // noise. That's a measurement that should be done, and
1169 // the code simplified if that turns out to be the case.
1170 return ConcGCThreads > 1;
1171 }
1172
1173 // Override
1174 virtual void ref_processor_init();
1175
1176 // Grow generation by specified size (returns false if unable to grow)
1177 bool grow_by(size_t bytes);
1178 // Grow generation to reserved size.
1179 bool grow_to_reserved();
1180
1181 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1182
1183 // Space enquiries
1184 size_t capacity() const;
1185 size_t used() const;
1186 size_t free() const;
1187 double occupancy() const { return ((double)used())/((double)capacity()); }
1188 size_t contiguous_available() const;
1189 size_t unsafe_max_alloc_nogc() const;
1190
1191 // over-rides
1192 MemRegion used_region() const;
1193 MemRegion used_region_at_save_marks() const;
1194
1195 // Does a "full" (forced) collection invoked on this generation collect
1196 // all younger generations as well? Note that the second conjunct is a
1197 // hack to allow the collection of the younger gen first if the flag is
1198 // set. This is better than using th policy's should_collect_gen0_first()
1199 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1200 virtual bool full_collects_younger_generations() const {
1201 return UseCMSCompactAtFullCollection && !CollectGen0First;
1202 }
1203
1204 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1205
1206 // Support for compaction
1207 CompactibleSpace* first_compaction_space() const;
1208 // Adjust quantities in the generation affected by
1209 // the compaction.
1210 void reset_after_compaction();
1211
1212 // Allocation support
1213 HeapWord* allocate(size_t size, bool tlab);
1214 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1215 oop promote(oop obj, size_t obj_size);
1216 HeapWord* par_allocate(size_t size, bool tlab) {
1217 return allocate(size, tlab);
1218 }
1219
1220 // Incremental mode triggering.
1221 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1222 size_t word_size);
1223
1224 // Used by CMSStats to track direct allocation. The value is sampled and
1225 // reset after each young gen collection.
1226 size_t direct_allocated_words() const { return _direct_allocated_words; }
1227 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1228
1229 // Overrides for parallel promotion.
1230 virtual oop par_promote(int thread_num,
1231 oop obj, markOop m, size_t word_sz);
1232 // This one should not be called for CMS.
1233 virtual void par_promote_alloc_undo(int thread_num,
1234 HeapWord* obj, size_t word_sz);
1235 virtual void par_promote_alloc_done(int thread_num);
1236 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1237
1238 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1239
1240 // Inform this (non-young) generation that a promotion failure was
1241 // encountered during a collection of a younger generation that
1242 // promotes into this generation.
1243 virtual void promotion_failure_occurred();
1244
1245 bool should_collect(bool full, size_t size, bool tlab);
1246 virtual bool should_concurrent_collect() const;
1247 virtual bool is_too_full() const;
1248 void collect(bool full,
1249 bool clear_all_soft_refs,
1250 size_t size,
1251 bool tlab);
1252
1253 HeapWord* expand_and_allocate(size_t word_size,
1254 bool tlab,
1255 bool parallel = false);
1256
1257 // GC prologue and epilogue
1258 void gc_prologue(bool full);
1259 void gc_prologue_work(bool full, bool registerClosure,
1260 ModUnionClosure* modUnionClosure);
1261 void gc_epilogue(bool full);
1262 void gc_epilogue_work(bool full);
1263
1264 // Time since last GC of this generation
1265 jlong time_of_last_gc(jlong now) {
1266 return collector()->time_of_last_gc(now);
1267 }
1268 void update_time_of_last_gc(jlong now) {
1269 collector()-> update_time_of_last_gc(now);
1270 }
1271
1272 // Allocation failure
1273 void expand(size_t bytes, size_t expand_bytes,
1274 CMSExpansionCause::Cause cause);
1275 virtual bool expand(size_t bytes, size_t expand_bytes);
1276 void shrink(size_t bytes);
1277 void shrink_by(size_t bytes);
1278 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1279 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1280
1281 // Iteration support and related enquiries
1282 void save_marks();
1283 bool no_allocs_since_save_marks();
1284 void younger_refs_iterate(OopsInGenClosure* cl);
1285
1286 // Iteration support specific to CMS generations
1287 void save_sweep_limit();
1288
1289 // More iteration support
1290 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1291 virtual void oop_iterate(ExtendedOopClosure* cl);
1292 virtual void safe_object_iterate(ObjectClosure* cl);
1293 virtual void object_iterate(ObjectClosure* cl);
1294
1295 // Need to declare the full complement of closures, whether we'll
1296 // override them or not, or get message from the compiler:
1297 // oop_since_save_marks_iterate_nv hides virtual function...
1298 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1299 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1300 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1301
1302 // Smart allocation XXX -- move to CFLSpace?
1303 void setNearLargestChunk();
1304 bool isNearLargestChunk(HeapWord* addr);
1305
1306 // Get the chunk at the end of the space. Delegates to
1307 // the space.
1308 FreeChunk* find_chunk_at_end();
1309
1310 void post_compact();
1311
1312 // Debugging
1313 void prepare_for_verify();
1314 void verify();
1315 void print_statistics() PRODUCT_RETURN;
1316
1317 // Performance Counters support
1318 virtual void update_counters();
1319 virtual void update_counters(size_t used);
1320 void initialize_performance_counters();
1321 CollectorCounters* counters() { return collector()->counters(); }
1322
1323 // Support for parallel remark of survivor space
1324 void* get_data_recorder(int thr_num) {
1325 //Delegate to collector
1326 return collector()->get_data_recorder(thr_num);
1327 }
1328 void sample_eden_chunk() {
1329 //Delegate to collector
1330 return collector()->sample_eden_chunk();
1331 }
1332
1333 // Printing
1334 const char* name() const;
1335 virtual const char* short_name() const { return "CMS"; }
1336 void print() const;
1337 void printOccupancy(const char* s);
1338 bool must_be_youngest() const { return false; }
1339 bool must_be_oldest() const { return true; }
1340
1341 // Resize the generation after a compacting GC. The
1342 // generation can be treated as a contiguous space
1343 // after the compaction.
1344 virtual void compute_new_size();
1345 // Resize the generation after a non-compacting
1346 // collection.
1347 void compute_new_size_free_list();
1348
1349 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1350 void rotate_debug_collection_type();
1351 };
1352
1353 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1354
1355 // Return the size policy from the heap's collector
1356 // policy casted to CMSAdaptiveSizePolicy*.
1357 CMSAdaptiveSizePolicy* cms_size_policy() const;
1358
1359 // Resize the generation based on the adaptive size
1360 // policy.
1361 void resize(size_t cur_promo, size_t desired_promo);
1362
1363 // Return the GC counters from the collector policy
1364 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1365
1366 virtual void shrink_by(size_t bytes);
1367
1368 public:
1369 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1370 int level, CardTableRS* ct,
1371 bool use_adaptive_freelists,
1372 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1373 dictionaryChoice) :
1374 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1375 use_adaptive_freelists, dictionaryChoice) {}
1376
1377 virtual const char* short_name() const { return "ASCMS"; }
1378 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1379
1380 virtual void update_counters();
1381 virtual void update_counters(size_t used);
1382 };
1383
1384 //
1385 // Closures of various sorts used by CMS to accomplish its work
1386 //
1387
1388 // This closure is used to do concurrent marking from the roots
1389 // following the first checkpoint.
1390 class MarkFromRootsClosure: public BitMapClosure {
1391 CMSCollector* _collector;
1392 MemRegion _span;
1393 CMSBitMap* _bitMap;
1394 CMSBitMap* _mut;
1395 CMSMarkStack* _markStack;
1396 bool _yield;
1397 int _skipBits;
1398 HeapWord* _finger;
1399 HeapWord* _threshold;
1400 DEBUG_ONLY(bool _verifying;)
1401
1402 public:
1403 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1404 CMSBitMap* bitMap,
1405 CMSMarkStack* markStack,
1406 bool should_yield, bool verifying = false);
1407 bool do_bit(size_t offset);
1408 void reset(HeapWord* addr);
1409 inline void do_yield_check();
1410
1411 private:
1412 void scanOopsInOop(HeapWord* ptr);
1413 void do_yield_work();
1414 };
1415
1416 // This closure is used to do concurrent multi-threaded
1417 // marking from the roots following the first checkpoint.
1418 // XXX This should really be a subclass of The serial version
1419 // above, but i have not had the time to refactor things cleanly.
1420 class Par_MarkFromRootsClosure: public BitMapClosure {
1421 CMSCollector* _collector;
1422 MemRegion _whole_span;
1423 MemRegion _span;
1424 CMSBitMap* _bit_map;
1425 CMSBitMap* _mut;
1426 OopTaskQueue* _work_queue;
1427 CMSMarkStack* _overflow_stack;
1428 bool _yield;
1429 int _skip_bits;
1430 HeapWord* _finger;
1431 HeapWord* _threshold;
1432 CMSConcMarkingTask* _task;
1433 public:
1434 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1435 MemRegion span,
1436 CMSBitMap* bit_map,
1437 OopTaskQueue* work_queue,
1438 CMSMarkStack* overflow_stack,
1439 bool should_yield);
1440 bool do_bit(size_t offset);
1441 inline void do_yield_check();
1442
1443 private:
1444 void scan_oops_in_oop(HeapWord* ptr);
1445 void do_yield_work();
1446 bool get_work_from_overflow_stack();
1447 };
1448
1449 // The following closures are used to do certain kinds of verification of
1450 // CMS marking.
1451 class PushAndMarkVerifyClosure: public CMSOopClosure {
1452 CMSCollector* _collector;
1453 MemRegion _span;
1454 CMSBitMap* _verification_bm;
1455 CMSBitMap* _cms_bm;
1456 CMSMarkStack* _mark_stack;
1457 protected:
1458 void do_oop(oop p);
1459 template <class T> inline void do_oop_work(T *p) {
1460 oop obj = oopDesc::load_decode_heap_oop(p);
1461 do_oop(obj);
1462 }
1463 public:
1464 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1465 MemRegion span,
1466 CMSBitMap* verification_bm,
1467 CMSBitMap* cms_bm,
1468 CMSMarkStack* mark_stack);
1469 void do_oop(oop* p);
1470 void do_oop(narrowOop* p);
1471
1472 // Deal with a stack overflow condition
1473 void handle_stack_overflow(HeapWord* lost);
1474 };
1475
1476 class MarkFromRootsVerifyClosure: public BitMapClosure {
1477 CMSCollector* _collector;
1478 MemRegion _span;
1479 CMSBitMap* _verification_bm;
1480 CMSBitMap* _cms_bm;
1481 CMSMarkStack* _mark_stack;
1482 HeapWord* _finger;
1483 PushAndMarkVerifyClosure _pam_verify_closure;
1484 public:
1485 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1486 CMSBitMap* verification_bm,
1487 CMSBitMap* cms_bm,
1488 CMSMarkStack* mark_stack);
1489 bool do_bit(size_t offset);
1490 void reset(HeapWord* addr);
1491 };
1492
1493
1494 // This closure is used to check that a certain set of bits is
1495 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1496 class FalseBitMapClosure: public BitMapClosure {
1497 public:
1498 bool do_bit(size_t offset) {
1499 guarantee(false, "Should not have a 1 bit");
1500 return true;
1501 }
1502 };
1503
1504 // This closure is used during the second checkpointing phase
1505 // to rescan the marked objects on the dirty cards in the mod
1506 // union table and the card table proper. It's invoked via
1507 // MarkFromDirtyCardsClosure below. It uses either
1508 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1509 // declared in genOopClosures.hpp to accomplish some of its work.
1510 // In the parallel case the bitMap is shared, so access to
1511 // it needs to be suitably synchronized for updates by embedded
1512 // closures that update it; however, this closure itself only
1513 // reads the bit_map and because it is idempotent, is immune to
1514 // reading stale values.
1515 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1516 #ifdef ASSERT
1517 CMSCollector* _collector;
1518 MemRegion _span;
1519 union {
1520 CMSMarkStack* _mark_stack;
1521 OopTaskQueue* _work_queue;
1522 };
1523 #endif // ASSERT
1524 bool _parallel;
1525 CMSBitMap* _bit_map;
1526 union {
1527 MarkRefsIntoAndScanClosure* _scan_closure;
1528 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1529 };
1530
1531 public:
1532 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1533 MemRegion span,
1534 ReferenceProcessor* rp,
1535 CMSBitMap* bit_map,
1536 CMSMarkStack* mark_stack,
1537 MarkRefsIntoAndScanClosure* cl):
1538 #ifdef ASSERT
1539 _collector(collector),
1540 _span(span),
1541 _mark_stack(mark_stack),
1542 #endif // ASSERT
1543 _parallel(false),
1544 _bit_map(bit_map),
1545 _scan_closure(cl) { }
1546
1547 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1548 MemRegion span,
1549 ReferenceProcessor* rp,
1550 CMSBitMap* bit_map,
1551 OopTaskQueue* work_queue,
1552 Par_MarkRefsIntoAndScanClosure* cl):
1553 #ifdef ASSERT
1554 _collector(collector),
1555 _span(span),
1556 _work_queue(work_queue),
1557 #endif // ASSERT
1558 _parallel(true),
1559 _bit_map(bit_map),
1560 _par_scan_closure(cl) { }
1561
1562 bool do_object_b(oop obj) {
1563 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1564 return false;
1565 }
1566 bool do_object_bm(oop p, MemRegion mr);
1567 };
1568
1569 // This closure is used during the second checkpointing phase
1570 // to rescan the marked objects on the dirty cards in the mod
1571 // union table and the card table proper. It invokes
1572 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1573 // In the parallel case, the bit map is shared and requires
1574 // synchronized access.
1575 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1576 CompactibleFreeListSpace* _space;
1577 ScanMarkedObjectsAgainClosure _scan_cl;
1578 size_t _num_dirty_cards;
1579
1580 public:
1581 MarkFromDirtyCardsClosure(CMSCollector* collector,
1582 MemRegion span,
1583 CompactibleFreeListSpace* space,
1584 CMSBitMap* bit_map,
1585 CMSMarkStack* mark_stack,
1586 MarkRefsIntoAndScanClosure* cl):
1587 _space(space),
1588 _num_dirty_cards(0),
1589 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1590 mark_stack, cl) { }
1591
1592 MarkFromDirtyCardsClosure(CMSCollector* collector,
1593 MemRegion span,
1594 CompactibleFreeListSpace* space,
1595 CMSBitMap* bit_map,
1596 OopTaskQueue* work_queue,
1597 Par_MarkRefsIntoAndScanClosure* cl):
1598 _space(space),
1599 _num_dirty_cards(0),
1600 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1601 work_queue, cl) { }
1602
1603 void do_MemRegion(MemRegion mr);
1604 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1605 size_t num_dirty_cards() { return _num_dirty_cards; }
1606 };
1607
1608 // This closure is used in the non-product build to check
1609 // that there are no MemRegions with a certain property.
1610 class FalseMemRegionClosure: public MemRegionClosure {
1611 void do_MemRegion(MemRegion mr) {
1612 guarantee(!mr.is_empty(), "Shouldn't be empty");
1613 guarantee(false, "Should never be here");
1614 }
1615 };
1616
1617 // This closure is used during the precleaning phase
1618 // to "carefully" rescan marked objects on dirty cards.
1619 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1620 // to accomplish some of its work.
1621 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1622 CMSCollector* _collector;
1623 MemRegion _span;
1624 bool _yield;
1625 Mutex* _freelistLock;
1626 CMSBitMap* _bitMap;
1627 CMSMarkStack* _markStack;
1628 MarkRefsIntoAndScanClosure* _scanningClosure;
1629
1630 public:
1631 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1632 MemRegion span,
1633 CMSBitMap* bitMap,
1634 CMSMarkStack* markStack,
1635 MarkRefsIntoAndScanClosure* cl,
1636 bool should_yield):
1637 _collector(collector),
1638 _span(span),
1639 _yield(should_yield),
1640 _bitMap(bitMap),
1641 _markStack(markStack),
1642 _scanningClosure(cl) {
1643 }
1644
1645 void do_object(oop p) {
1646 guarantee(false, "call do_object_careful instead");
1647 }
1648
1649 size_t do_object_careful(oop p) {
1650 guarantee(false, "Unexpected caller");
1651 return 0;
1652 }
1653
1654 size_t do_object_careful_m(oop p, MemRegion mr);
1655
1656 void setFreelistLock(Mutex* m) {
1657 _freelistLock = m;
1658 _scanningClosure->set_freelistLock(m);
1659 }
1660
1661 private:
1662 inline bool do_yield_check();
1663
1664 void do_yield_work();
1665 };
1666
1667 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1668 CMSCollector* _collector;
1669 MemRegion _span;
1670 bool _yield;
1671 CMSBitMap* _bit_map;
1672 CMSMarkStack* _mark_stack;
1673 PushAndMarkClosure* _scanning_closure;
1674 unsigned int _before_count;
1675
1676 public:
1677 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1678 MemRegion span,
1679 CMSBitMap* bit_map,
1680 CMSMarkStack* mark_stack,
1681 PushAndMarkClosure* cl,
1682 unsigned int before_count,
1683 bool should_yield):
1684 _collector(collector),
1685 _span(span),
1686 _yield(should_yield),
1687 _bit_map(bit_map),
1688 _mark_stack(mark_stack),
1689 _scanning_closure(cl),
1690 _before_count(before_count)
1691 { }
1692
1693 void do_object(oop p) {
1694 guarantee(false, "call do_object_careful instead");
1695 }
1696
1697 size_t do_object_careful(oop p);
1698
1699 size_t do_object_careful_m(oop p, MemRegion mr) {
1700 guarantee(false, "Unexpected caller");
1701 return 0;
1702 }
1703
1704 private:
1705 inline void do_yield_check();
1706 void do_yield_work();
1707 };
1708
1709 // This closure is used to accomplish the sweeping work
1710 // after the second checkpoint but before the concurrent reset
1711 // phase.
1712 //
1713 // Terminology
1714 // left hand chunk (LHC) - block of one or more chunks currently being
1715 // coalesced. The LHC is available for coalescing with a new chunk.
1716 // right hand chunk (RHC) - block that is currently being swept that is
1717 // free or garbage that can be coalesced with the LHC.
1718 // _inFreeRange is true if there is currently a LHC
1719 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1720 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1721 // _freeFinger is the address of the current LHC
1722 class SweepClosure: public BlkClosureCareful {
1723 CMSCollector* _collector; // collector doing the work
1724 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1725 CompactibleFreeListSpace* _sp; // Space being swept
1726 HeapWord* _limit;// the address at or above which the sweep should stop
1727 // because we do not expect newly garbage blocks
1728 // eligible for sweeping past that address.
1729 Mutex* _freelistLock; // Free list lock (in space)
1730 CMSBitMap* _bitMap; // Marking bit map (in
1731 // generation)
1732 bool _inFreeRange; // Indicates if we are in the
1733 // midst of a free run
1734 bool _freeRangeInFreeLists;
1735 // Often, we have just found
1736 // a free chunk and started
1737 // a new free range; we do not
1738 // eagerly remove this chunk from
1739 // the free lists unless there is
1740 // a possibility of coalescing.
1741 // When true, this flag indicates
1742 // that the _freeFinger below
1743 // points to a potentially free chunk
1744 // that may still be in the free lists
1745 bool _lastFreeRangeCoalesced;
1746 // free range contains chunks
1747 // coalesced
1748 bool _yield;
1749 // Whether sweeping should be
1750 // done with yields. For instance
1751 // when done by the foreground
1752 // collector we shouldn't yield.
1753 HeapWord* _freeFinger; // When _inFreeRange is set, the
1754 // pointer to the "left hand
1755 // chunk"
1756 size_t _freeRangeSize;
1757 // When _inFreeRange is set, this
1758 // indicates the accumulated size
1759 // of the "left hand chunk"
1760 NOT_PRODUCT(
1761 size_t _numObjectsFreed;
1762 size_t _numWordsFreed;
1763 size_t _numObjectsLive;
1764 size_t _numWordsLive;
1765 size_t _numObjectsAlreadyFree;
1766 size_t _numWordsAlreadyFree;
1767 FreeChunk* _last_fc;
1768 )
1769 private:
1770 // Code that is common to a free chunk or garbage when
1771 // encountered during sweeping.
1772 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1773 // Process a free chunk during sweeping.
1774 void do_already_free_chunk(FreeChunk *fc);
1775 // Work method called when processing an already free or a
1776 // freshly garbage chunk to do a lookahead and possibly a
1777 // preemptive flush if crossing over _limit.
1778 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1779 // Process a garbage chunk during sweeping.
1780 size_t do_garbage_chunk(FreeChunk *fc);
1781 // Process a live chunk during sweeping.
1782 size_t do_live_chunk(FreeChunk* fc);
1783
1784 // Accessors.
1785 HeapWord* freeFinger() const { return _freeFinger; }
1786 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1787 bool inFreeRange() const { return _inFreeRange; }
1788 void set_inFreeRange(bool v) { _inFreeRange = v; }
1789 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1790 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1791 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1792 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1793
1794 // Initialize a free range.
1795 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1796 // Return this chunk to the free lists.
1797 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1798
1799 // Check if we should yield and do so when necessary.
1800 inline void do_yield_check(HeapWord* addr);
1801
1802 // Yield
1803 void do_yield_work(HeapWord* addr);
1804
1805 // Debugging/Printing
1806 void print_free_block_coalesced(FreeChunk* fc) const;
1807
1808 public:
1809 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1810 CMSBitMap* bitMap, bool should_yield);
1811 ~SweepClosure() PRODUCT_RETURN;
1812
1813 size_t do_blk_careful(HeapWord* addr);
1814 void print() const { print_on(tty); }
1815 void print_on(outputStream *st) const;
1816 };
1817
1818 // Closures related to weak references processing
1819
1820 // During CMS' weak reference processing, this is a
1821 // work-routine/closure used to complete transitive
1822 // marking of objects as live after a certain point
1823 // in which an initial set has been completely accumulated.
1824 // This closure is currently used both during the final
1825 // remark stop-world phase, as well as during the concurrent
1826 // precleaning of the discovered reference lists.
1827 class CMSDrainMarkingStackClosure: public VoidClosure {
1828 CMSCollector* _collector;
1829 MemRegion _span;
1830 CMSMarkStack* _mark_stack;
1831 CMSBitMap* _bit_map;
1832 CMSKeepAliveClosure* _keep_alive;
1833 bool _concurrent_precleaning;
1834 public:
1835 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1836 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1837 CMSKeepAliveClosure* keep_alive,
1838 bool cpc):
1839 _collector(collector),
1840 _span(span),
1841 _bit_map(bit_map),
1842 _mark_stack(mark_stack),
1843 _keep_alive(keep_alive),
1844 _concurrent_precleaning(cpc) {
1845 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1846 "Mismatch");
1847 }
1848
1849 void do_void();
1850 };
1851
1852 // A parallel version of CMSDrainMarkingStackClosure above.
1853 class CMSParDrainMarkingStackClosure: public VoidClosure {
1854 CMSCollector* _collector;
1855 MemRegion _span;
1856 OopTaskQueue* _work_queue;
1857 CMSBitMap* _bit_map;
1858 CMSInnerParMarkAndPushClosure _mark_and_push;
1859
1860 public:
1861 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1862 MemRegion span, CMSBitMap* bit_map,
1863 OopTaskQueue* work_queue):
1864 _collector(collector),
1865 _span(span),
1866 _bit_map(bit_map),
1867 _work_queue(work_queue),
1868 _mark_and_push(collector, span, bit_map, work_queue) { }
1869
1870 public:
1871 void trim_queue(uint max);
1872 void do_void();
1873 };
1874
1875 // Allow yielding or short-circuiting of reference list
1876 // precleaning work.
1877 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1878 CMSCollector* _collector;
1879 void do_yield_work();
1880 public:
1881 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1882 _collector(collector) {}
1883 virtual bool should_return();
1884 };
1885
1886
1887 // Convenience class that locks free list locks for given CMS collector
1888 class FreelistLocker: public StackObj {
1889 private:
1890 CMSCollector* _collector;
1891 public:
1892 FreelistLocker(CMSCollector* collector):
1893 _collector(collector) {
1894 _collector->getFreelistLocks();
1895 }
1896
1897 ~FreelistLocker() {
1898 _collector->releaseFreelistLocks();
1899 }
1900 };
1901
1902 // Mark all dead objects in a given space.
1903 class MarkDeadObjectsClosure: public BlkClosure {
1904 const CMSCollector* _collector;
1905 const CompactibleFreeListSpace* _sp;
1906 CMSBitMap* _live_bit_map;
1907 CMSBitMap* _dead_bit_map;
1908 public:
1909 MarkDeadObjectsClosure(const CMSCollector* collector,
1910 const CompactibleFreeListSpace* sp,
1911 CMSBitMap *live_bit_map,
1912 CMSBitMap *dead_bit_map) :
1913 _collector(collector),
1914 _sp(sp),
1915 _live_bit_map(live_bit_map),
1916 _dead_bit_map(dead_bit_map) {}
1917 size_t do_blk(HeapWord* addr);
1918 };
1919
1920 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1921
1922 public:
1923 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1924 };
1925
1926
1927 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP