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comparison: src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp

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1 /*
2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
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 public:
359 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
360 unsigned int alpha = CMSExpAvgFactor);
361
362 // Whether or not the statistics contain valid data; higher level statistics
363 // cannot be called until this returns true (they require at least one young
364 // gen and one cms cycle to have completed).
365 bool valid() const;
366
367 // Record statistics.
368 void record_gc0_begin();
369 void record_gc0_end(size_t cms_gen_bytes_used);
370 void record_cms_begin();
371 void record_cms_end();
372
373 // Allow management of the cms timer, which must be stopped/started around
374 // yield points.
375 elapsedTimer& cms_timer() { return _cms_timer; }
376 void start_cms_timer() { _cms_timer.start(); }
377 void stop_cms_timer() { _cms_timer.stop(); }
378
379 // Basic statistics; units are seconds or bytes.
380 double gc0_period() const { return _gc0_period; }
381 double gc0_duration() const { return _gc0_duration; }
382 size_t gc0_promoted() const { return _gc0_promoted; }
383 double cms_period() const { return _cms_period; }
384 double cms_duration() const { return _cms_duration; }
385 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
386 size_t cms_allocated() const { return _cms_allocated; }
387
388 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
389
390 // Seconds since the last background cms cycle began or ended.
391 double cms_time_since_begin() const;
392 double cms_time_since_end() const;
393
394 // Higher level statistics--caller must check that valid() returns true before
395 // calling.
396
397 // Returns bytes promoted per second of wall clock time.
398 double promotion_rate() const;
399
400 // Returns bytes directly allocated per second of wall clock time.
401 double cms_allocation_rate() const;
402
403 // Rate at which space in the cms generation is being consumed (sum of the
404 // above two).
405 double cms_consumption_rate() const;
406
407 // Returns an estimate of the number of seconds until the cms generation will
408 // fill up, assuming no collection work is done.
409 double time_until_cms_gen_full() const;
410
411 // Returns an estimate of the number of seconds remaining until
412 // the cms generation collection should start.
413 double time_until_cms_start() const;
414
415 // End of higher level statistics.
416
417 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
418 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
419
420 // Update the duty cycle and return the new value.
421 unsigned int icms_update_duty_cycle();
422
423 // Debugging.
424 void print_on(outputStream* st) const PRODUCT_RETURN;
425 void print() const { print_on(gclog_or_tty); }
426 };
427
428 // A closure related to weak references processing which
429 // we embed in the CMSCollector, since we need to pass
430 // it to the reference processor for secondary filtering
431 // of references based on reachability of referent;
432 // see role of _is_alive_non_header closure in the
433 // ReferenceProcessor class.
434 // For objects in the CMS generation, this closure checks
435 // if the object is "live" (reachable). Used in weak
436 // reference processing.
437 class CMSIsAliveClosure: public BoolObjectClosure {
438 MemRegion _span;
439 const CMSBitMap* _bit_map;
440
441 friend class CMSCollector;
442 protected:
443 void set_span(MemRegion span) { _span = span; }
444 public:
445 CMSIsAliveClosure(CMSBitMap* bit_map):
446 _bit_map(bit_map) { }
447
448 CMSIsAliveClosure(MemRegion span,
449 CMSBitMap* bit_map):
450 _span(span),
451 _bit_map(bit_map) { }
452 void do_object(oop obj) {
453 assert(false, "not to be invoked");
454 }
455 bool do_object_b(oop obj);
456 };
457
458
459 // Implements AbstractRefProcTaskExecutor for CMS.
460 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
461 public:
462
463 CMSRefProcTaskExecutor(CMSCollector& collector)
464 : _collector(collector)
465 { }
466
467 // Executes a task using worker threads.
468 virtual void execute(ProcessTask& task);
469 virtual void execute(EnqueueTask& task);
470 private:
471 CMSCollector& _collector;
472 };
473
474
475 class CMSCollector: public CHeapObj {
476 friend class VMStructs;
477 friend class ConcurrentMarkSweepThread;
478 friend class ConcurrentMarkSweepGeneration;
479 friend class CompactibleFreeListSpace;
480 friend class CMSParRemarkTask;
481 friend class CMSConcMarkingTask;
482 friend class CMSRefProcTaskProxy;
483 friend class CMSRefProcTaskExecutor;
484 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
485 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
486 friend class PushOrMarkClosure; // to access _restart_addr
487 friend class Par_PushOrMarkClosure; // to access _restart_addr
488 friend class MarkFromRootsClosure; // -- ditto --
489 // ... and for clearing cards
490 friend class Par_MarkFromRootsClosure; // to access _restart_addr
491 // ... and for clearing cards
492 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
493 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
494 friend class PushAndMarkVerifyClosure; // -- ditto --
495 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
496 friend class PushAndMarkClosure; // -- ditto --
497 friend class Par_PushAndMarkClosure; // -- ditto --
498 friend class CMSKeepAliveClosure; // -- ditto --
499 friend class CMSDrainMarkingStackClosure; // -- ditto --
500 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
501 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
502 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
503 friend class VM_CMS_Operation;
504 friend class VM_CMS_Initial_Mark;
505 friend class VM_CMS_Final_Remark;
506
507 private:
508 jlong _time_of_last_gc;
509 void update_time_of_last_gc(jlong now) {
510 _time_of_last_gc = now;
511 }
512
513 OopTaskQueueSet* _task_queues;
514
515 // Overflow list of grey objects, threaded through mark-word
516 // Manipulated with CAS in the parallel/multi-threaded case.
517 oop _overflow_list;
518 // The following array-pair keeps track of mark words
519 // displaced for accomodating overflow list above.
520 // This code will likely be revisited under RFE#4922830.
521 GrowableArray<oop>* _preserved_oop_stack;
522 GrowableArray<markOop>* _preserved_mark_stack;
523
524 int* _hash_seed;
525
526 // In support of multi-threaded concurrent phases
527 YieldingFlexibleWorkGang* _conc_workers;
528
529 // Performance Counters
530 CollectorCounters* _gc_counters;
531
532 // Initialization Errors
533 bool _completed_initialization;
534
535 // In support of ExplicitGCInvokesConcurrent
536 static bool _full_gc_requested;
537 unsigned int _collection_count_start;
538 // Should we unload classes this concurrent cycle?
539 // Set in response to a concurrent full gc request.
540 bool _unload_classes;
541 bool _unloaded_classes_last_cycle;
542 // Did we (allow) unload classes in the previous concurrent cycle?
543 bool cms_unloaded_classes_last_cycle() const {
544 return _unloaded_classes_last_cycle || CMSClassUnloadingEnabled;
545 }
546
547 // Verification support
548 CMSBitMap _verification_mark_bm;
549 void verify_after_remark_work_1();
550 void verify_after_remark_work_2();
551
552 // true if any verification flag is on.
553 bool _verifying;
554 bool verifying() const { return _verifying; }
555 void set_verifying(bool v) { _verifying = v; }
556
557 // Collector policy
558 ConcurrentMarkSweepPolicy* _collector_policy;
559 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
560
561 // Check whether the gc time limit has been
562 // exceeded and set the size policy flag
563 // appropriately.
564 void check_gc_time_limit();
565 // XXX Move these to CMSStats ??? FIX ME !!!
566 elapsedTimer _sweep_timer;
567 AdaptivePaddedAverage _sweep_estimate;
568
569 protected:
570 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
571 ConcurrentMarkSweepGeneration* _permGen; // perm gen
572 MemRegion _span; // span covering above two
573 CardTableRS* _ct; // card table
574
575 // CMS marking support structures
576 CMSBitMap _markBitMap;
577 CMSBitMap _modUnionTable;
578 CMSMarkStack _markStack;
579 CMSMarkStack _revisitStack; // used to keep track of klassKlass objects
580 // to revisit
581 CMSBitMap _perm_gen_verify_bit_map; // Mark bit map for perm gen verification support.
582
583 HeapWord* _restart_addr; // in support of marking stack overflow
584 void lower_restart_addr(HeapWord* low);
585
586 // Counters in support of marking stack / work queue overflow handling:
587 // a non-zero value indicates certain types of overflow events during
588 // the current CMS cycle and could lead to stack resizing efforts at
589 // an opportune future time.
590 size_t _ser_pmc_preclean_ovflw;
591 size_t _ser_pmc_remark_ovflw;
592 size_t _par_pmc_remark_ovflw;
593 size_t _ser_kac_ovflw;
594 size_t _par_kac_ovflw;
595 NOT_PRODUCT(size_t _num_par_pushes;)
596
597 // ("Weak") Reference processing support
598 ReferenceProcessor* _ref_processor;
599 CMSIsAliveClosure _is_alive_closure;
600 // keep this textually after _markBitMap; c'tor dependency
601
602 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
603 ModUnionClosure _modUnionClosure;
604 ModUnionClosurePar _modUnionClosurePar;
605
606 // CMS abstract state machine
607 // initial_state: Idling
608 // next_state(Idling) = {Marking}
609 // next_state(Marking) = {Precleaning, Sweeping}
610 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
611 // next_state(AbortablePreclean) = {FinalMarking}
612 // next_state(FinalMarking) = {Sweeping}
613 // next_state(Sweeping) = {Resizing}
614 // next_state(Resizing) = {Resetting}
615 // next_state(Resetting) = {Idling}
616 // The numeric values below are chosen so that:
617 // . _collectorState <= Idling == post-sweep && pre-mark
618 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
619 // precleaning || abortablePrecleanb
620 enum CollectorState {
621 Resizing = 0,
622 Resetting = 1,
623 Idling = 2,
624 InitialMarking = 3,
625 Marking = 4,
626 Precleaning = 5,
627 AbortablePreclean = 6,
628 FinalMarking = 7,
629 Sweeping = 8
630 };
631 static CollectorState _collectorState;
632
633 // State related to prologue/epilogue invocation for my generations
634 bool _between_prologue_and_epilogue;
635
636 // Signalling/State related to coordination between fore- and backgroud GC
637 // Note: When the baton has been passed from background GC to foreground GC,
638 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
639 static bool _foregroundGCIsActive; // true iff foreground collector is active or
640 // wants to go active
641 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
642 // yet passed the baton to the foreground GC
643
644 // Support for CMSScheduleRemark (abortable preclean)
645 bool _abort_preclean;
646 bool _start_sampling;
647
648 int _numYields;
649 size_t _numDirtyCards;
650 uint _sweepCount;
651 // number of full gc's since the last concurrent gc.
652 uint _full_gcs_since_conc_gc;
653
654 // if occupancy exceeds this, start a new gc cycle
655 double _initiatingOccupancy;
656 // occupancy used for bootstrapping stats
657 double _bootstrap_occupancy;
658
659 // timer
660 elapsedTimer _timer;
661
662 // Timing, allocation and promotion statistics, used for scheduling.
663 CMSStats _stats;
664
665 // Allocation limits installed in the young gen, used only in
666 // CMSIncrementalMode. When an allocation in the young gen would cross one of
667 // these limits, the cms generation is notified and the cms thread is started
668 // or stopped, respectively.
669 HeapWord* _icms_start_limit;
670 HeapWord* _icms_stop_limit;
671
672 enum CMS_op_type {
673 CMS_op_checkpointRootsInitial,
674 CMS_op_checkpointRootsFinal
675 };
676
677 void do_CMS_operation(CMS_op_type op);
678 bool stop_world_and_do(CMS_op_type op);
679
680 OopTaskQueueSet* task_queues() { return _task_queues; }
681 int* hash_seed(int i) { return &_hash_seed[i]; }
682 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
683
684 // Support for parallelizing Eden rescan in CMS remark phase
685 void sample_eden(); // ... sample Eden space top
686
687 private:
688 // Support for parallelizing young gen rescan in CMS remark phase
689 Generation* _young_gen; // the younger gen
690 HeapWord** _top_addr; // ... Top of Eden
691 HeapWord** _end_addr; // ... End of Eden
692 HeapWord** _eden_chunk_array; // ... Eden partitioning array
693 size_t _eden_chunk_index; // ... top (exclusive) of array
694 size_t _eden_chunk_capacity; // ... max entries in array
695
696 // Support for parallelizing survivor space rescan
697 HeapWord** _survivor_chunk_array;
698 size_t _survivor_chunk_index;
699 size_t _survivor_chunk_capacity;
700 size_t* _cursor;
701 ChunkArray* _survivor_plab_array;
702
703 // Support for marking stack overflow handling
704 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
705 bool par_take_from_overflow_list(size_t num, OopTaskQueue* to_work_q);
706 void push_on_overflow_list(oop p);
707 void par_push_on_overflow_list(oop p);
708 // the following is, obviously, not, in general, "MT-stable"
709 bool overflow_list_is_empty() const;
710
711 void preserve_mark_if_necessary(oop p);
712 void par_preserve_mark_if_necessary(oop p);
713 void preserve_mark_work(oop p, markOop m);
714 void restore_preserved_marks_if_any();
715 NOT_PRODUCT(bool no_preserved_marks() const;)
716 // in support of testing overflow code
717 NOT_PRODUCT(int _overflow_counter;)
718 NOT_PRODUCT(bool simulate_overflow();) // sequential
719 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
720
721 int _roots_scanning_options;
722 int roots_scanning_options() const { return _roots_scanning_options; }
723 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
724 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
725
726 // CMS work methods
727 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
728
729 // a return value of false indicates failure due to stack overflow
730 bool markFromRootsWork(bool asynch); // concurrent marking work
731
732 public: // FIX ME!!! only for testing
733 bool do_marking_st(bool asynch); // single-threaded marking
734 bool do_marking_mt(bool asynch); // multi-threaded marking
735
736 private:
737
738 // concurrent precleaning work
739 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
740 ScanMarkedObjectsAgainCarefullyClosure* cl);
741 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
742 ScanMarkedObjectsAgainCarefullyClosure* cl);
743 // Does precleaning work, returning a quantity indicative of
744 // the amount of "useful work" done.
745 size_t preclean_work(bool clean_refs, bool clean_survivors);
746 void abortable_preclean(); // Preclean while looking for possible abort
747 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
748 // Helper function for above; merge-sorts the per-thread plab samples
749 void merge_survivor_plab_arrays(ContiguousSpace* surv);
750 // Resets (i.e. clears) the per-thread plab sample vectors
751 void reset_survivor_plab_arrays();
752
753 // final (second) checkpoint work
754 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
755 bool init_mark_was_synchronous);
756 // work routine for parallel version of remark
757 void do_remark_parallel();
758 // work routine for non-parallel version of remark
759 void do_remark_non_parallel();
760 // reference processing work routine (during second checkpoint)
761 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
762
763 // concurrent sweeping work
764 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
765
766 // (concurrent) resetting of support data structures
767 void reset(bool asynch);
768
769 // Clear _expansion_cause fields of constituent generations
770 void clear_expansion_cause();
771
772 // An auxilliary method used to record the ends of
773 // used regions of each generation to limit the extent of sweep
774 void save_sweep_limits();
775
776 // Resize the generations included in the collector.
777 void compute_new_size();
778
779 // A work method used by foreground collection to determine
780 // what type of collection (compacting or not, continuing or fresh)
781 // it should do.
782 void decide_foreground_collection_type(bool clear_all_soft_refs,
783 bool* should_compact, bool* should_start_over);
784
785 // A work method used by the foreground collector to do
786 // a mark-sweep-compact.
787 void do_compaction_work(bool clear_all_soft_refs);
788
789 // A work method used by the foreground collector to do
790 // a mark-sweep, after taking over from a possibly on-going
791 // concurrent mark-sweep collection.
792 void do_mark_sweep_work(bool clear_all_soft_refs,
793 CollectorState first_state, bool should_start_over);
794
795 // If the backgrould GC is active, acquire control from the background
796 // GC and do the collection.
797 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
798
799 // For synchronizing passing of control from background to foreground
800 // GC. waitForForegroundGC() is called by the background
801 // collector. It if had to wait for a foreground collection,
802 // it returns true and the background collection should assume
803 // that the collection was finished by the foreground
804 // collector.
805 bool waitForForegroundGC();
806
807 // Incremental mode triggering: recompute the icms duty cycle and set the
808 // allocation limits in the young gen.
809 void icms_update_allocation_limits();
810
811 size_t block_size_using_printezis_bits(HeapWord* addr) const;
812 size_t block_size_if_printezis_bits(HeapWord* addr) const;
813 HeapWord* next_card_start_after_block(HeapWord* addr) const;
814
815 void setup_cms_unloading_and_verification_state();
816 public:
817 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
818 ConcurrentMarkSweepGeneration* permGen,
819 CardTableRS* ct,
820 ConcurrentMarkSweepPolicy* cp);
821 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
822
823 ReferenceProcessor* ref_processor() { return _ref_processor; }
824 void ref_processor_init();
825
826 Mutex* bitMapLock() const { return _markBitMap.lock(); }
827 static CollectorState abstract_state() { return _collectorState; }
828 double initiatingOccupancy() const { return _initiatingOccupancy; }
829
830 bool should_abort_preclean() const; // Whether preclean should be aborted.
831 size_t get_eden_used() const;
832 size_t get_eden_capacity() const;
833
834 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
835
836 // locking checks
837 NOT_PRODUCT(static bool have_cms_token();)
838
839 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
840 bool shouldConcurrentCollect();
841
842 void collect(bool full,
843 bool clear_all_soft_refs,
844 size_t size,
845 bool tlab);
846 void collect_in_background(bool clear_all_soft_refs);
847 void collect_in_foreground(bool clear_all_soft_refs);
848
849 // In support of ExplicitGCInvokesConcurrent
850 static void request_full_gc(unsigned int full_gc_count);
851 // Should we unload classes in a particular concurrent cycle?
852 bool cms_should_unload_classes() const {
853 assert(!_unload_classes || ExplicitGCInvokesConcurrentAndUnloadsClasses,
854 "Inconsistency; see CR 6541037");
855 return _unload_classes || CMSClassUnloadingEnabled;
856 }
857
858 void direct_allocated(HeapWord* start, size_t size);
859
860 // Object is dead if not marked and current phase is sweeping.
861 bool is_dead_obj(oop obj) const;
862
863 // After a promotion (of "start"), do any necessary marking.
864 // If "par", then it's being done by a parallel GC thread.
865 // The last two args indicate if we need precise marking
866 // and if so the size of the object so it can be dirtied
867 // in its entirety.
868 void promoted(bool par, HeapWord* start,
869 bool is_obj_array, size_t obj_size);
870
871 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
872 size_t word_size);
873
874 void getFreelistLocks() const;
875 void releaseFreelistLocks() const;
876 bool haveFreelistLocks() const;
877
878 // GC prologue and epilogue
879 void gc_prologue(bool full);
880 void gc_epilogue(bool full);
881
882 jlong time_of_last_gc(jlong now) {
883 if (_collectorState <= Idling) {
884 // gc not in progress
885 return _time_of_last_gc;
886 } else {
887 // collection in progress
888 return now;
889 }
890 }
891
892 // Support for parallel remark of survivor space
893 void* get_data_recorder(int thr_num);
894
895 CMSBitMap* markBitMap() { return &_markBitMap; }
896 void directAllocated(HeapWord* start, size_t size);
897
898 // main CMS steps and related support
899 void checkpointRootsInitial(bool asynch);
900 bool markFromRoots(bool asynch); // a return value of false indicates failure
901 // due to stack overflow
902 void preclean();
903 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
904 bool init_mark_was_synchronous);
905 void sweep(bool asynch);
906
907 // Check that the currently executing thread is the expected
908 // one (foreground collector or background collector).
909 void check_correct_thread_executing() PRODUCT_RETURN;
910 // XXXPERM void print_statistics() PRODUCT_RETURN;
911
912 bool is_cms_reachable(HeapWord* addr);
913
914 // Performance Counter Support
915 CollectorCounters* counters() { return _gc_counters; }
916
917 // timer stuff
918 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
919 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
920 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
921 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
922
923 int yields() { return _numYields; }
924 void resetYields() { _numYields = 0; }
925 void incrementYields() { _numYields++; }
926 void resetNumDirtyCards() { _numDirtyCards = 0; }
927 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
928 size_t numDirtyCards() { return _numDirtyCards; }
929
930 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
931 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
932 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
933 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
934 uint sweepCount() const { return _sweepCount; }
935 void incrementSweepCount() { _sweepCount++; }
936
937 // Timers/stats for gc scheduling and incremental mode pacing.
938 CMSStats& stats() { return _stats; }
939
940 // Convenience methods that check whether CMSIncrementalMode is enabled and
941 // forward to the corresponding methods in ConcurrentMarkSweepThread.
942 static void start_icms();
943 static void stop_icms(); // Called at the end of the cms cycle.
944 static void disable_icms(); // Called before a foreground collection.
945 static void enable_icms(); // Called after a foreground collection.
946 void icms_wait(); // Called at yield points.
947
948 // Adaptive size policy
949 CMSAdaptiveSizePolicy* size_policy();
950 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
951
952 // debugging
953 void verify(bool);
954 bool verify_after_remark();
955 void verify_ok_to_terminate() const PRODUCT_RETURN;
956 void verify_work_stacks_empty() const PRODUCT_RETURN;
957 void verify_overflow_empty() const PRODUCT_RETURN;
958
959 // convenience methods in support of debugging
960 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
961 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
962
963 // accessors
964 CMSMarkStack* verification_mark_stack() { return &_markStack; }
965 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
966
967 // Get the bit map with a perm gen "deadness" information.
968 CMSBitMap* perm_gen_verify_bit_map() { return &_perm_gen_verify_bit_map; }
969
970 // Initialization errors
971 bool completed_initialization() { return _completed_initialization; }
972 };
973
974 class CMSExpansionCause : public AllStatic {
975 public:
976 enum Cause {
977 _no_expansion,
978 _satisfy_free_ratio,
979 _satisfy_promotion,
980 _satisfy_allocation,
981 _allocate_par_lab,
982 _allocate_par_spooling_space,
983 _adaptive_size_policy
984 };
985 // Return a string describing the cause of the expansion.
986 static const char* to_string(CMSExpansionCause::Cause cause);
987 };
988
989 class ConcurrentMarkSweepGeneration: public CardGeneration {
990 friend class VMStructs;
991 friend class ConcurrentMarkSweepThread;
992 friend class ConcurrentMarkSweep;
993 friend class CMSCollector;
994 protected:
995 static CMSCollector* _collector; // the collector that collects us
996 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
997
998 // Performance Counters
999 GenerationCounters* _gen_counters;
1000 GSpaceCounters* _space_counters;
1001
1002 // Words directly allocated, used by CMSStats.
1003 size_t _direct_allocated_words;
1004
1005 // Non-product stat counters
1006 NOT_PRODUCT(
1007 int _numObjectsPromoted;
1008 int _numWordsPromoted;
1009 int _numObjectsAllocated;
1010 int _numWordsAllocated;
1011 )
1012
1013 // Used for sizing decisions
1014 bool _incremental_collection_failed;
1015 bool incremental_collection_failed() {
1016 return _incremental_collection_failed;
1017 }
1018 void set_incremental_collection_failed() {
1019 _incremental_collection_failed = true;
1020 }
1021 void clear_incremental_collection_failed() {
1022 _incremental_collection_failed = false;
1023 }
1024
1025 private:
1026 // For parallel young-gen GC support.
1027 CMSParGCThreadState** _par_gc_thread_states;
1028
1029 // Reason generation was expanded
1030 CMSExpansionCause::Cause _expansion_cause;
1031
1032 // accessors
1033 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1034 CMSExpansionCause::Cause expansion_cause() { return _expansion_cause; }
1035
1036 // In support of MinChunkSize being larger than min object size
1037 const double _dilatation_factor;
1038
1039 enum CollectionTypes {
1040 Concurrent_collection_type = 0,
1041 MS_foreground_collection_type = 1,
1042 MSC_foreground_collection_type = 2,
1043 Unknown_collection_type = 3
1044 };
1045
1046 CollectionTypes _debug_collection_type;
1047
1048 protected:
1049 // Grow generation by specified size (returns false if unable to grow)
1050 bool grow_by(size_t bytes);
1051 // Grow generation to reserved size.
1052 bool grow_to_reserved();
1053 // Shrink generation by specified size (returns false if unable to shrink)
1054 virtual void shrink_by(size_t bytes);
1055
1056 // Update statistics for GC
1057 virtual void update_gc_stats(int level, bool full);
1058
1059 // Maximum available space in the generation (including uncommitted)
1060 // space.
1061 size_t max_available() const;
1062
1063 public:
1064 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1065 int level, CardTableRS* ct,
1066 bool use_adaptive_freelists,
1067 FreeBlockDictionary::DictionaryChoice);
1068
1069 // Accessors
1070 CMSCollector* collector() const { return _collector; }
1071 static void set_collector(CMSCollector* collector) {
1072 assert(_collector == NULL, "already set");
1073 _collector = collector;
1074 }
1075 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1076
1077 Mutex* freelistLock() const;
1078
1079 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1080
1081 // Adaptive size policy
1082 CMSAdaptiveSizePolicy* size_policy();
1083
1084 bool refs_discovery_is_atomic() const { return false; }
1085 bool refs_discovery_is_mt() const {
1086 // Note: CMS does MT-discovery during the parallel-remark
1087 // phases. Use ReferenceProcessorMTMutator to make refs
1088 // discovery MT-safe during such phases or other parallel
1089 // discovery phases in the future. This may all go away
1090 // if/when we decide that refs discovery is sufficiently
1091 // rare that the cost of the CAS's involved is in the
1092 // noise. That's a measurement that should be done, and
1093 // the code simplified if that turns out to be the case.
1094 return false;
1095 }
1096
1097 // Override
1098 virtual void ref_processor_init();
1099
1100 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1101
1102 // Space enquiries
1103 size_t capacity() const;
1104 size_t used() const;
1105 size_t free() const;
1106 double occupancy() { return ((double)used())/((double)capacity()); }
1107 size_t contiguous_available() const;
1108 size_t unsafe_max_alloc_nogc() const;
1109
1110 // over-rides
1111 MemRegion used_region() const;
1112 MemRegion used_region_at_save_marks() const;
1113
1114 // Does a "full" (forced) collection invoked on this generation collect
1115 // all younger generations as well? Note that the second conjunct is a
1116 // hack to allow the collection of the younger gen first if the flag is
1117 // set. This is better than using th policy's should_collect_gen0_first()
1118 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1119 virtual bool full_collects_younger_generations() const {
1120 return UseCMSCompactAtFullCollection && !CollectGen0First;
1121 }
1122
1123 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1124
1125 // Support for compaction
1126 CompactibleSpace* first_compaction_space() const;
1127 // Adjust quantites in the generation affected by
1128 // the compaction.
1129 void reset_after_compaction();
1130
1131 // Allocation support
1132 HeapWord* allocate(size_t size, bool tlab);
1133 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1134 oop promote(oop obj, size_t obj_size, oop* ref);
1135 HeapWord* par_allocate(size_t size, bool tlab) {
1136 return allocate(size, tlab);
1137 }
1138
1139 // Incremental mode triggering.
1140 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1141 size_t word_size);
1142
1143 // Used by CMSStats to track direct allocation. The value is sampled and
1144 // reset after each young gen collection.
1145 size_t direct_allocated_words() const { return _direct_allocated_words; }
1146 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1147
1148 // Overrides for parallel promotion.
1149 virtual oop par_promote(int thread_num,
1150 oop obj, markOop m, size_t word_sz);
1151 // This one should not be called for CMS.
1152 virtual void par_promote_alloc_undo(int thread_num,
1153 HeapWord* obj, size_t word_sz);
1154 virtual void par_promote_alloc_done(int thread_num);
1155 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1156
1157 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes,
1158 bool younger_handles_promotion_failure) const;
1159
1160 bool should_collect(bool full, size_t size, bool tlab);
1161 // XXXPERM
1162 bool shouldConcurrentCollect(double initiatingOccupancy); // XXXPERM
1163 void collect(bool full,
1164 bool clear_all_soft_refs,
1165 size_t size,
1166 bool tlab);
1167
1168 HeapWord* expand_and_allocate(size_t word_size,
1169 bool tlab,
1170 bool parallel = false);
1171
1172 // GC prologue and epilogue
1173 void gc_prologue(bool full);
1174 void gc_prologue_work(bool full, bool registerClosure,
1175 ModUnionClosure* modUnionClosure);
1176 void gc_epilogue(bool full);
1177 void gc_epilogue_work(bool full);
1178
1179 // Time since last GC of this generation
1180 jlong time_of_last_gc(jlong now) {
1181 return collector()->time_of_last_gc(now);
1182 }
1183 void update_time_of_last_gc(jlong now) {
1184 collector()-> update_time_of_last_gc(now);
1185 }
1186
1187 // Allocation failure
1188 void expand(size_t bytes, size_t expand_bytes,
1189 CMSExpansionCause::Cause cause);
1190 void shrink(size_t bytes);
1191 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1192 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1193
1194 // Iteration support and related enquiries
1195 void save_marks();
1196 bool no_allocs_since_save_marks();
1197 void object_iterate_since_last_GC(ObjectClosure* cl);
1198 void younger_refs_iterate(OopsInGenClosure* cl);
1199
1200 // Iteration support specific to CMS generations
1201 void save_sweep_limit();
1202
1203 // More iteration support
1204 virtual void oop_iterate(MemRegion mr, OopClosure* cl);
1205 virtual void oop_iterate(OopClosure* cl);
1206 virtual void object_iterate(ObjectClosure* cl);
1207
1208 // Need to declare the full complement of closures, whether we'll
1209 // override them or not, or get message from the compiler:
1210 // oop_since_save_marks_iterate_nv hides virtual function...
1211 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1212 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1213 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1214
1215 // Smart allocation XXX -- move to CFLSpace?
1216 void setNearLargestChunk();
1217 bool isNearLargestChunk(HeapWord* addr);
1218
1219 // Get the chunk at the end of the space. Delagates to
1220 // the space.
1221 FreeChunk* find_chunk_at_end();
1222
1223 // Overriding of unused functionality (sharing not yet supported with CMS)
1224 void pre_adjust_pointers();
1225 void post_compact();
1226
1227 // Debugging
1228 void prepare_for_verify();
1229 void verify(bool allow_dirty);
1230 void print_statistics() PRODUCT_RETURN;
1231
1232 // Performance Counters support
1233 virtual void update_counters();
1234 virtual void update_counters(size_t used);
1235 void initialize_performance_counters();
1236 CollectorCounters* counters() { return collector()->counters(); }
1237
1238 // Support for parallel remark of survivor space
1239 void* get_data_recorder(int thr_num) {
1240 //Delegate to collector
1241 return collector()->get_data_recorder(thr_num);
1242 }
1243
1244 // Printing
1245 const char* name() const;
1246 virtual const char* short_name() const { return "CMS"; }
1247 void print() const;
1248 void printOccupancy(const char* s);
1249 bool must_be_youngest() const { return false; }
1250 bool must_be_oldest() const { return true; }
1251
1252 void compute_new_size();
1253
1254 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1255 void rotate_debug_collection_type();
1256 };
1257
1258 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1259
1260 // Return the size policy from the heap's collector
1261 // policy casted to CMSAdaptiveSizePolicy*.
1262 CMSAdaptiveSizePolicy* cms_size_policy() const;
1263
1264 // Resize the generation based on the adaptive size
1265 // policy.
1266 void resize(size_t cur_promo, size_t desired_promo);
1267
1268 // Return the GC counters from the collector policy
1269 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1270
1271 virtual void shrink_by(size_t bytes);
1272
1273 public:
1274 virtual void compute_new_size();
1275 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1276 int level, CardTableRS* ct,
1277 bool use_adaptive_freelists,
1278 FreeBlockDictionary::DictionaryChoice
1279 dictionaryChoice) :
1280 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1281 use_adaptive_freelists, dictionaryChoice) {}
1282
1283 virtual const char* short_name() const { return "ASCMS"; }
1284 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1285
1286 virtual void update_counters();
1287 virtual void update_counters(size_t used);
1288 };
1289
1290 //
1291 // Closures of various sorts used by CMS to accomplish its work
1292 //
1293
1294 // This closure is used to check that a certain set of oops is empty.
1295 class FalseClosure: public OopClosure {
1296 public:
1297 void do_oop(oop* p) {
1298 guarantee(false, "Should be an empty set");
1299 }
1300 };
1301
1302 // This closure is used to do concurrent marking from the roots
1303 // following the first checkpoint.
1304 class MarkFromRootsClosure: public BitMapClosure {
1305 CMSCollector* _collector;
1306 MemRegion _span;
1307 CMSBitMap* _bitMap;
1308 CMSBitMap* _mut;
1309 CMSMarkStack* _markStack;
1310 CMSMarkStack* _revisitStack;
1311 bool _yield;
1312 int _skipBits;
1313 HeapWord* _finger;
1314 HeapWord* _threshold;
1315 DEBUG_ONLY(bool _verifying;)
1316
1317 public:
1318 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1319 CMSBitMap* bitMap,
1320 CMSMarkStack* markStack,
1321 CMSMarkStack* revisitStack,
1322 bool should_yield, bool verifying = false);
1323 void do_bit(size_t offset);
1324 void reset(HeapWord* addr);
1325 inline void do_yield_check();
1326
1327 private:
1328 void scanOopsInOop(HeapWord* ptr);
1329 void do_yield_work();
1330 };
1331
1332 // This closure is used to do concurrent multi-threaded
1333 // marking from the roots following the first checkpoint.
1334 // XXX This should really be a subclass of The serial version
1335 // above, but i have not had the time to refactor things cleanly.
1336 // That willbe done for Dolphin.
1337 class Par_MarkFromRootsClosure: public BitMapClosure {
1338 CMSCollector* _collector;
1339 MemRegion _whole_span;
1340 MemRegion _span;
1341 CMSBitMap* _bit_map;
1342 CMSBitMap* _mut;
1343 OopTaskQueue* _work_queue;
1344 CMSMarkStack* _overflow_stack;
1345 CMSMarkStack* _revisit_stack;
1346 bool _yield;
1347 int _skip_bits;
1348 HeapWord* _finger;
1349 HeapWord* _threshold;
1350 CMSConcMarkingTask* _task;
1351 public:
1352 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1353 MemRegion span,
1354 CMSBitMap* bit_map,
1355 OopTaskQueue* work_queue,
1356 CMSMarkStack* overflow_stack,
1357 CMSMarkStack* revisit_stack,
1358 bool should_yield);
1359 void do_bit(size_t offset);
1360 inline void do_yield_check();
1361
1362 private:
1363 void scan_oops_in_oop(HeapWord* ptr);
1364 void do_yield_work();
1365 bool get_work_from_overflow_stack();
1366 };
1367
1368 // The following closures are used to do certain kinds of verification of
1369 // CMS marking.
1370 class PushAndMarkVerifyClosure: public OopClosure {
1371 CMSCollector* _collector;
1372 MemRegion _span;
1373 CMSBitMap* _verification_bm;
1374 CMSBitMap* _cms_bm;
1375 CMSMarkStack* _mark_stack;
1376 public:
1377 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1378 MemRegion span,
1379 CMSBitMap* verification_bm,
1380 CMSBitMap* cms_bm,
1381 CMSMarkStack* mark_stack);
1382 void do_oop(oop* p);
1383 // Deal with a stack overflow condition
1384 void handle_stack_overflow(HeapWord* lost);
1385 };
1386
1387 class MarkFromRootsVerifyClosure: public BitMapClosure {
1388 CMSCollector* _collector;
1389 MemRegion _span;
1390 CMSBitMap* _verification_bm;
1391 CMSBitMap* _cms_bm;
1392 CMSMarkStack* _mark_stack;
1393 HeapWord* _finger;
1394 PushAndMarkVerifyClosure _pam_verify_closure;
1395 public:
1396 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1397 CMSBitMap* verification_bm,
1398 CMSBitMap* cms_bm,
1399 CMSMarkStack* mark_stack);
1400 void do_bit(size_t offset);
1401 void reset(HeapWord* addr);
1402 };
1403
1404
1405 // This closure is used to check that a certain set of bits is
1406 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1407 class FalseBitMapClosure: public BitMapClosure {
1408 public:
1409 void do_bit(size_t offset) {
1410 guarantee(false, "Should not have a 1 bit");
1411 }
1412 };
1413
1414 // This closure is used during the second checkpointing phase
1415 // to rescan the marked objects on the dirty cards in the mod
1416 // union table and the card table proper. It's invoked via
1417 // MarkFromDirtyCardsClosure below. It uses either
1418 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1419 // declared in genOopClosures.hpp to accomplish some of its work.
1420 // In the parallel case the bitMap is shared, so access to
1421 // it needs to be suitably synchronized for updates by embedded
1422 // closures that update it; however, this closure itself only
1423 // reads the bit_map and because it is idempotent, is immune to
1424 // reading stale values.
1425 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1426 #ifdef ASSERT
1427 CMSCollector* _collector;
1428 MemRegion _span;
1429 union {
1430 CMSMarkStack* _mark_stack;
1431 OopTaskQueue* _work_queue;
1432 };
1433 #endif // ASSERT
1434 bool _parallel;
1435 CMSBitMap* _bit_map;
1436 union {
1437 MarkRefsIntoAndScanClosure* _scan_closure;
1438 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1439 };
1440
1441 public:
1442 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1443 MemRegion span,
1444 ReferenceProcessor* rp,
1445 CMSBitMap* bit_map,
1446 CMSMarkStack* mark_stack,
1447 CMSMarkStack* revisit_stack,
1448 MarkRefsIntoAndScanClosure* cl):
1449 #ifdef ASSERT
1450 _collector(collector),
1451 _span(span),
1452 _mark_stack(mark_stack),
1453 #endif // ASSERT
1454 _parallel(false),
1455 _bit_map(bit_map),
1456 _scan_closure(cl) { }
1457
1458 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1459 MemRegion span,
1460 ReferenceProcessor* rp,
1461 CMSBitMap* bit_map,
1462 OopTaskQueue* work_queue,
1463 CMSMarkStack* revisit_stack,
1464 Par_MarkRefsIntoAndScanClosure* cl):
1465 #ifdef ASSERT
1466 _collector(collector),
1467 _span(span),
1468 _work_queue(work_queue),
1469 #endif // ASSERT
1470 _parallel(true),
1471 _bit_map(bit_map),
1472 _par_scan_closure(cl) { }
1473
1474 void do_object(oop obj) {
1475 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1476 }
1477 bool do_object_b(oop obj) {
1478 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1479 return false;
1480 }
1481 bool do_object_bm(oop p, MemRegion mr);
1482 };
1483
1484 // This closure is used during the second checkpointing phase
1485 // to rescan the marked objects on the dirty cards in the mod
1486 // union table and the card table proper. It invokes
1487 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1488 // In the parallel case, the bit map is shared and requires
1489 // synchronized access.
1490 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1491 CompactibleFreeListSpace* _space;
1492 ScanMarkedObjectsAgainClosure _scan_cl;
1493 size_t _num_dirty_cards;
1494
1495 public:
1496 MarkFromDirtyCardsClosure(CMSCollector* collector,
1497 MemRegion span,
1498 CompactibleFreeListSpace* space,
1499 CMSBitMap* bit_map,
1500 CMSMarkStack* mark_stack,
1501 CMSMarkStack* revisit_stack,
1502 MarkRefsIntoAndScanClosure* cl):
1503 _space(space),
1504 _num_dirty_cards(0),
1505 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1506 mark_stack, revisit_stack, cl) { }
1507
1508 MarkFromDirtyCardsClosure(CMSCollector* collector,
1509 MemRegion span,
1510 CompactibleFreeListSpace* space,
1511 CMSBitMap* bit_map,
1512 OopTaskQueue* work_queue,
1513 CMSMarkStack* revisit_stack,
1514 Par_MarkRefsIntoAndScanClosure* cl):
1515 _space(space),
1516 _num_dirty_cards(0),
1517 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1518 work_queue, revisit_stack, cl) { }
1519
1520 void do_MemRegion(MemRegion mr);
1521 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1522 size_t num_dirty_cards() { return _num_dirty_cards; }
1523 };
1524
1525 // This closure is used in the non-product build to check
1526 // that there are no MemRegions with a certain property.
1527 class FalseMemRegionClosure: public MemRegionClosure {
1528 void do_MemRegion(MemRegion mr) {
1529 guarantee(!mr.is_empty(), "Shouldn't be empty");
1530 guarantee(false, "Should never be here");
1531 }
1532 };
1533
1534 // This closure is used during the precleaning phase
1535 // to "carefully" rescan marked objects on dirty cards.
1536 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1537 // to accomplish some of its work.
1538 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1539 CMSCollector* _collector;
1540 MemRegion _span;
1541 bool _yield;
1542 Mutex* _freelistLock;
1543 CMSBitMap* _bitMap;
1544 CMSMarkStack* _markStack;
1545 MarkRefsIntoAndScanClosure* _scanningClosure;
1546
1547 public:
1548 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1549 MemRegion span,
1550 CMSBitMap* bitMap,
1551 CMSMarkStack* markStack,
1552 CMSMarkStack* revisitStack,
1553 MarkRefsIntoAndScanClosure* cl,
1554 bool should_yield):
1555 _collector(collector),
1556 _span(span),
1557 _yield(should_yield),
1558 _bitMap(bitMap),
1559 _markStack(markStack),
1560 _scanningClosure(cl) {
1561 }
1562
1563 void do_object(oop p) {
1564 guarantee(false, "call do_object_careful instead");
1565 }
1566
1567 size_t do_object_careful(oop p) {
1568 guarantee(false, "Unexpected caller");
1569 return 0;
1570 }
1571
1572 size_t do_object_careful_m(oop p, MemRegion mr);
1573
1574 void setFreelistLock(Mutex* m) {
1575 _freelistLock = m;
1576 _scanningClosure->set_freelistLock(m);
1577 }
1578
1579 private:
1580 inline bool do_yield_check();
1581
1582 void do_yield_work();
1583 };
1584
1585 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1586 CMSCollector* _collector;
1587 MemRegion _span;
1588 bool _yield;
1589 CMSBitMap* _bit_map;
1590 CMSMarkStack* _mark_stack;
1591 PushAndMarkClosure* _scanning_closure;
1592 unsigned int _before_count;
1593
1594 public:
1595 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1596 MemRegion span,
1597 CMSBitMap* bit_map,
1598 CMSMarkStack* mark_stack,
1599 PushAndMarkClosure* cl,
1600 unsigned int before_count,
1601 bool should_yield):
1602 _collector(collector),
1603 _span(span),
1604 _yield(should_yield),
1605 _bit_map(bit_map),
1606 _mark_stack(mark_stack),
1607 _scanning_closure(cl),
1608 _before_count(before_count)
1609 { }
1610
1611 void do_object(oop p) {
1612 guarantee(false, "call do_object_careful instead");
1613 }
1614
1615 size_t do_object_careful(oop p);
1616
1617 size_t do_object_careful_m(oop p, MemRegion mr) {
1618 guarantee(false, "Unexpected caller");
1619 return 0;
1620 }
1621
1622 private:
1623 inline void do_yield_check();
1624 void do_yield_work();
1625 };
1626
1627 // This closure is used to accomplish the sweeping work
1628 // after the second checkpoint but before the concurrent reset
1629 // phase.
1630 //
1631 // Terminology
1632 // left hand chunk (LHC) - block of one or more chunks currently being
1633 // coalesced. The LHC is available for coalescing with a new chunk.
1634 // right hand chunk (RHC) - block that is currently being swept that is
1635 // free or garbage that can be coalesced with the LHC.
1636 // _inFreeRange is true if there is currently a LHC
1637 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1638 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1639 // _freeFinger is the address of the current LHC
1640 class SweepClosure: public BlkClosureCareful {
1641 CMSCollector* _collector; // collector doing the work
1642 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1643 CompactibleFreeListSpace* _sp; // Space being swept
1644 HeapWord* _limit;
1645 Mutex* _freelistLock; // Free list lock (in space)
1646 CMSBitMap* _bitMap; // Marking bit map (in
1647 // generation)
1648 bool _inFreeRange; // Indicates if we are in the
1649 // midst of a free run
1650 bool _freeRangeInFreeLists;
1651 // Often, we have just found
1652 // a free chunk and started
1653 // a new free range; we do not
1654 // eagerly remove this chunk from
1655 // the free lists unless there is
1656 // a possibility of coalescing.
1657 // When true, this flag indicates
1658 // that the _freeFinger below
1659 // points to a potentially free chunk
1660 // that may still be in the free lists
1661 bool _lastFreeRangeCoalesced;
1662 // free range contains chunks
1663 // coalesced
1664 bool _yield;
1665 // Whether sweeping should be
1666 // done with yields. For instance
1667 // when done by the foreground
1668 // collector we shouldn't yield.
1669 HeapWord* _freeFinger; // When _inFreeRange is set, the
1670 // pointer to the "left hand
1671 // chunk"
1672 size_t _freeRangeSize;
1673 // When _inFreeRange is set, this
1674 // indicates the accumulated size
1675 // of the "left hand chunk"
1676 NOT_PRODUCT(
1677 size_t _numObjectsFreed;
1678 size_t _numWordsFreed;
1679 size_t _numObjectsLive;
1680 size_t _numWordsLive;
1681 size_t _numObjectsAlreadyFree;
1682 size_t _numWordsAlreadyFree;
1683 FreeChunk* _last_fc;
1684 )
1685 private:
1686 // Code that is common to a free chunk or garbage when
1687 // encountered during sweeping.
1688 void doPostIsFreeOrGarbageChunk(FreeChunk *fc,
1689 size_t chunkSize);
1690 // Process a free chunk during sweeping.
1691 void doAlreadyFreeChunk(FreeChunk *fc);
1692 // Process a garbage chunk during sweeping.
1693 size_t doGarbageChunk(FreeChunk *fc);
1694 // Process a live chunk during sweeping.
1695 size_t doLiveChunk(FreeChunk* fc);
1696
1697 // Accessors.
1698 HeapWord* freeFinger() const { return _freeFinger; }
1699 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1700 size_t freeRangeSize() const { return _freeRangeSize; }
1701 void set_freeRangeSize(size_t v) { _freeRangeSize = v; }
1702 bool inFreeRange() const { return _inFreeRange; }
1703 void set_inFreeRange(bool v) { _inFreeRange = v; }
1704 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1705 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1706 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1707 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1708
1709 // Initialize a free range.
1710 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1711 // Return this chunk to the free lists.
1712 void flushCurFreeChunk(HeapWord* chunk, size_t size);
1713
1714 // Check if we should yield and do so when necessary.
1715 inline void do_yield_check(HeapWord* addr);
1716
1717 // Yield
1718 void do_yield_work(HeapWord* addr);
1719
1720 // Debugging/Printing
1721 void record_free_block_coalesced(FreeChunk* fc) const PRODUCT_RETURN;
1722
1723 public:
1724 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1725 CMSBitMap* bitMap, bool should_yield);
1726 ~SweepClosure();
1727
1728 size_t do_blk_careful(HeapWord* addr);
1729 };
1730
1731 // Closures related to weak references processing
1732
1733 // During CMS' weak reference processing, this is a
1734 // work-routine/closure used to complete transitive
1735 // marking of objects as live after a certain point
1736 // in which an initial set has been completely accumulated.
1737 class CMSDrainMarkingStackClosure: public VoidClosure {
1738 CMSCollector* _collector;
1739 MemRegion _span;
1740 CMSMarkStack* _mark_stack;
1741 CMSBitMap* _bit_map;
1742 CMSKeepAliveClosure* _keep_alive;
1743 public:
1744 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1745 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1746 CMSKeepAliveClosure* keep_alive):
1747 _collector(collector),
1748 _span(span),
1749 _bit_map(bit_map),
1750 _mark_stack(mark_stack),
1751 _keep_alive(keep_alive) { }
1752
1753 void do_void();
1754 };
1755
1756 // A parallel version of CMSDrainMarkingStackClosure above.
1757 class CMSParDrainMarkingStackClosure: public VoidClosure {
1758 CMSCollector* _collector;
1759 MemRegion _span;
1760 OopTaskQueue* _work_queue;
1761 CMSBitMap* _bit_map;
1762 CMSInnerParMarkAndPushClosure _mark_and_push;
1763
1764 public:
1765 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1766 MemRegion span, CMSBitMap* bit_map,
1767 OopTaskQueue* work_queue):
1768 _collector(collector),
1769 _span(span),
1770 _bit_map(bit_map),
1771 _work_queue(work_queue),
1772 _mark_and_push(collector, span, bit_map, work_queue) { }
1773
1774 public:
1775 void trim_queue(uint max);
1776 void do_void();
1777 };
1778
1779 // Allow yielding or short-circuiting of reference list
1780 // prelceaning work.
1781 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1782 CMSCollector* _collector;
1783 void do_yield_work();
1784 public:
1785 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1786 _collector(collector) {}
1787 virtual bool should_return();
1788 };
1789
1790
1791 // Convenience class that locks free list locks for given CMS collector
1792 class FreelistLocker: public StackObj {
1793 private:
1794 CMSCollector* _collector;
1795 public:
1796 FreelistLocker(CMSCollector* collector):
1797 _collector(collector) {
1798 _collector->getFreelistLocks();
1799 }
1800
1801 ~FreelistLocker() {
1802 _collector->releaseFreelistLocks();
1803 }
1804 };
1805
1806 // Mark all dead objects in a given space.
1807 class MarkDeadObjectsClosure: public BlkClosure {
1808 const CMSCollector* _collector;
1809 const CompactibleFreeListSpace* _sp;
1810 CMSBitMap* _live_bit_map;
1811 CMSBitMap* _dead_bit_map;
1812 public:
1813 MarkDeadObjectsClosure(const CMSCollector* collector,
1814 const CompactibleFreeListSpace* sp,
1815 CMSBitMap *live_bit_map,
1816 CMSBitMap *dead_bit_map) :
1817 _collector(collector),
1818 _sp(sp),
1819 _live_bit_map(live_bit_map),
1820 _dead_bit_map(dead_bit_map) {}
1821 size_t do_blk(HeapWord* addr);
1822 };

Mercurial Repository: jdk8-mips64-public/hotspot

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