Tue, 27 Nov 2012 07:57:57 -0800
8003879: Duplicate definitions in vmStructs
Summary: Removed duplicate entries
Reviewed-by: dholmes, sspitsyn
1 /*
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP
28 #include "gc_implementation/shared/gSpaceCounters.hpp"
29 #include "gc_implementation/shared/gcStats.hpp"
30 #include "gc_implementation/shared/generationCounters.hpp"
31 #include "memory/freeBlockDictionary.hpp"
32 #include "memory/generation.hpp"
33 #include "runtime/mutexLocker.hpp"
34 #include "runtime/virtualspace.hpp"
35 #include "services/memoryService.hpp"
36 #include "utilities/bitMap.inline.hpp"
37 #include "utilities/stack.inline.hpp"
38 #include "utilities/taskqueue.hpp"
39 #include "utilities/yieldingWorkgroup.hpp"
41 // ConcurrentMarkSweepGeneration is in support of a concurrent
42 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
43 // style. We assume, for now, that this generation is always the
44 // seniormost generation and for simplicity
45 // in the first implementation, that this generation is a single compactible
46 // space. Neither of these restrictions appears essential, and will be
47 // relaxed in the future when more time is available to implement the
48 // greater generality (and there's a need for it).
49 //
50 // Concurrent mode failures are currently handled by
51 // means of a sliding mark-compact.
53 class CMSAdaptiveSizePolicy;
54 class CMSConcMarkingTask;
55 class CMSGCAdaptivePolicyCounters;
56 class ConcurrentMarkSweepGeneration;
57 class ConcurrentMarkSweepPolicy;
58 class ConcurrentMarkSweepThread;
59 class CompactibleFreeListSpace;
60 class FreeChunk;
61 class PromotionInfo;
62 class ScanMarkedObjectsAgainCarefullyClosure;
64 // A generic CMS bit map. It's the basis for both the CMS marking bit map
65 // as well as for the mod union table (in each case only a subset of the
66 // methods are used). This is essentially a wrapper around the BitMap class,
67 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
68 // we have _shifter == 0. and for the mod union table we have
69 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
70 // XXX 64-bit issues in BitMap?
71 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
72 friend class VMStructs;
74 HeapWord* _bmStartWord; // base address of range covered by map
75 size_t _bmWordSize; // map size (in #HeapWords covered)
76 const int _shifter; // shifts to convert HeapWord to bit position
77 VirtualSpace _virtual_space; // underlying the bit map
78 BitMap _bm; // the bit map itself
79 public:
80 Mutex* const _lock; // mutex protecting _bm;
82 public:
83 // constructor
84 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
86 // allocates the actual storage for the map
87 bool allocate(MemRegion mr);
88 // field getter
89 Mutex* lock() const { return _lock; }
90 // locking verifier convenience function
91 void assert_locked() const PRODUCT_RETURN;
93 // inquiries
94 HeapWord* startWord() const { return _bmStartWord; }
95 size_t sizeInWords() const { return _bmWordSize; }
96 size_t sizeInBits() const { return _bm.size(); }
97 // the following is one past the last word in space
98 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
100 // reading marks
101 bool isMarked(HeapWord* addr) const;
102 bool par_isMarked(HeapWord* addr) const; // do not lock checks
103 bool isUnmarked(HeapWord* addr) const;
104 bool isAllClear() const;
106 // writing marks
107 void mark(HeapWord* addr);
108 // For marking by parallel GC threads;
109 // returns true if we did, false if another thread did
110 bool par_mark(HeapWord* addr);
112 void mark_range(MemRegion mr);
113 void par_mark_range(MemRegion mr);
114 void mark_large_range(MemRegion mr);
115 void par_mark_large_range(MemRegion mr);
116 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
117 void clear_range(MemRegion mr);
118 void par_clear_range(MemRegion mr);
119 void clear_large_range(MemRegion mr);
120 void par_clear_large_range(MemRegion mr);
121 void clear_all();
122 void clear_all_incrementally(); // Not yet implemented!!
124 NOT_PRODUCT(
125 // checks the memory region for validity
126 void region_invariant(MemRegion mr);
127 )
129 // iteration
130 void iterate(BitMapClosure* cl) {
131 _bm.iterate(cl);
132 }
133 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
134 void dirty_range_iterate_clear(MemRegionClosure* cl);
135 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
137 // auxiliary support for iteration
138 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
139 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
140 HeapWord* end_addr) const;
141 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
142 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
143 HeapWord* end_addr) const;
144 MemRegion getAndClearMarkedRegion(HeapWord* addr);
145 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
146 HeapWord* end_addr);
148 // conversion utilities
149 HeapWord* offsetToHeapWord(size_t offset) const;
150 size_t heapWordToOffset(HeapWord* addr) const;
151 size_t heapWordDiffToOffsetDiff(size_t diff) const;
153 // debugging
154 // is this address range covered by the bit-map?
155 NOT_PRODUCT(
156 bool covers(MemRegion mr) const;
157 bool covers(HeapWord* start, size_t size = 0) const;
158 )
159 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
160 };
162 // Represents a marking stack used by the CMS collector.
163 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
164 class CMSMarkStack: public CHeapObj<mtGC> {
165 //
166 friend class CMSCollector; // to get at expasion stats further below
167 //
169 VirtualSpace _virtual_space; // space for the stack
170 oop* _base; // bottom of stack
171 size_t _index; // one more than last occupied index
172 size_t _capacity; // max #elements
173 Mutex _par_lock; // an advisory lock used in case of parallel access
174 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run
176 protected:
177 size_t _hit_limit; // we hit max stack size limit
178 size_t _failed_double; // we failed expansion before hitting limit
180 public:
181 CMSMarkStack():
182 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
183 _hit_limit(0),
184 _failed_double(0) {}
186 bool allocate(size_t size);
188 size_t capacity() const { return _capacity; }
190 oop pop() {
191 if (!isEmpty()) {
192 return _base[--_index] ;
193 }
194 return NULL;
195 }
197 bool push(oop ptr) {
198 if (isFull()) {
199 return false;
200 } else {
201 _base[_index++] = ptr;
202 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
203 return true;
204 }
205 }
207 bool isEmpty() const { return _index == 0; }
208 bool isFull() const {
209 assert(_index <= _capacity, "buffer overflow");
210 return _index == _capacity;
211 }
213 size_t length() { return _index; }
215 // "Parallel versions" of some of the above
216 oop par_pop() {
217 // lock and pop
218 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
219 return pop();
220 }
222 bool par_push(oop ptr) {
223 // lock and push
224 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
225 return push(ptr);
226 }
228 // Forcibly reset the stack, losing all of its contents.
229 void reset() {
230 _index = 0;
231 }
233 // Expand the stack, typically in response to an overflow condition
234 void expand();
236 // Compute the least valued stack element.
237 oop least_value(HeapWord* low) {
238 oop least = (oop)low;
239 for (size_t i = 0; i < _index; i++) {
240 least = MIN2(least, _base[i]);
241 }
242 return least;
243 }
245 // Exposed here to allow stack expansion in || case
246 Mutex* par_lock() { return &_par_lock; }
247 };
249 class CardTableRS;
250 class CMSParGCThreadState;
252 class ModUnionClosure: public MemRegionClosure {
253 protected:
254 CMSBitMap* _t;
255 public:
256 ModUnionClosure(CMSBitMap* t): _t(t) { }
257 void do_MemRegion(MemRegion mr);
258 };
260 class ModUnionClosurePar: public ModUnionClosure {
261 public:
262 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
263 void do_MemRegion(MemRegion mr);
264 };
266 // Survivor Chunk Array in support of parallelization of
267 // Survivor Space rescan.
268 class ChunkArray: public CHeapObj<mtGC> {
269 size_t _index;
270 size_t _capacity;
271 size_t _overflows;
272 HeapWord** _array; // storage for array
274 public:
275 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
276 ChunkArray(HeapWord** a, size_t c):
277 _index(0), _capacity(c), _overflows(0), _array(a) {}
279 HeapWord** array() { return _array; }
280 void set_array(HeapWord** a) { _array = a; }
282 size_t capacity() { return _capacity; }
283 void set_capacity(size_t c) { _capacity = c; }
285 size_t end() {
286 assert(_index <= capacity(),
287 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
288 _index, _capacity));
289 return _index;
290 } // exclusive
292 HeapWord* nth(size_t n) {
293 assert(n < end(), "Out of bounds access");
294 return _array[n];
295 }
297 void reset() {
298 _index = 0;
299 if (_overflows > 0 && PrintCMSStatistics > 1) {
300 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
301 _capacity, _overflows);
302 }
303 _overflows = 0;
304 }
306 void record_sample(HeapWord* p, size_t sz) {
307 // For now we do not do anything with the size
308 if (_index < _capacity) {
309 _array[_index++] = p;
310 } else {
311 ++_overflows;
312 assert(_index == _capacity,
313 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
314 "): out of bounds at overflow#" SIZE_FORMAT,
315 _index, _capacity, _overflows));
316 }
317 }
318 };
320 //
321 // Timing, allocation and promotion statistics for gc scheduling and incremental
322 // mode pacing. Most statistics are exponential averages.
323 //
324 class CMSStats VALUE_OBJ_CLASS_SPEC {
325 private:
326 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
328 // The following are exponential averages with factor alpha:
329 // avg = (100 - alpha) * avg + alpha * cur_sample
330 //
331 // The durations measure: end_time[n] - start_time[n]
332 // The periods measure: start_time[n] - start_time[n-1]
333 //
334 // The cms period and duration include only concurrent collections; time spent
335 // in foreground cms collections due to System.gc() or because of a failure to
336 // keep up are not included.
337 //
338 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
339 // real value, but is used only after the first period. A value of 100 is
340 // used for the first sample so it gets the entire weight.
341 unsigned int _saved_alpha; // 0-100
342 unsigned int _gc0_alpha;
343 unsigned int _cms_alpha;
345 double _gc0_duration;
346 double _gc0_period;
347 size_t _gc0_promoted; // bytes promoted per gc0
348 double _cms_duration;
349 double _cms_duration_pre_sweep; // time from initiation to start of sweep
350 double _cms_duration_per_mb;
351 double _cms_period;
352 size_t _cms_allocated; // bytes of direct allocation per gc0 period
354 // Timers.
355 elapsedTimer _cms_timer;
356 TimeStamp _gc0_begin_time;
357 TimeStamp _cms_begin_time;
358 TimeStamp _cms_end_time;
360 // Snapshots of the amount used in the CMS generation.
361 size_t _cms_used_at_gc0_begin;
362 size_t _cms_used_at_gc0_end;
363 size_t _cms_used_at_cms_begin;
365 // Used to prevent the duty cycle from being reduced in the middle of a cms
366 // cycle.
367 bool _allow_duty_cycle_reduction;
369 enum {
370 _GC0_VALID = 0x1,
371 _CMS_VALID = 0x2,
372 _ALL_VALID = _GC0_VALID | _CMS_VALID
373 };
375 unsigned int _valid_bits;
377 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
379 protected:
381 // Return a duty cycle that avoids wild oscillations, by limiting the amount
382 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
383 // as a recommended value).
384 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
385 unsigned int new_duty_cycle);
386 unsigned int icms_update_duty_cycle_impl();
388 // In support of adjusting of cms trigger ratios based on history
389 // of concurrent mode failure.
390 double cms_free_adjustment_factor(size_t free) const;
391 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
393 public:
394 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
395 unsigned int alpha = CMSExpAvgFactor);
397 // Whether or not the statistics contain valid data; higher level statistics
398 // cannot be called until this returns true (they require at least one young
399 // gen and one cms cycle to have completed).
400 bool valid() const;
402 // Record statistics.
403 void record_gc0_begin();
404 void record_gc0_end(size_t cms_gen_bytes_used);
405 void record_cms_begin();
406 void record_cms_end();
408 // Allow management of the cms timer, which must be stopped/started around
409 // yield points.
410 elapsedTimer& cms_timer() { return _cms_timer; }
411 void start_cms_timer() { _cms_timer.start(); }
412 void stop_cms_timer() { _cms_timer.stop(); }
414 // Basic statistics; units are seconds or bytes.
415 double gc0_period() const { return _gc0_period; }
416 double gc0_duration() const { return _gc0_duration; }
417 size_t gc0_promoted() const { return _gc0_promoted; }
418 double cms_period() const { return _cms_period; }
419 double cms_duration() const { return _cms_duration; }
420 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
421 size_t cms_allocated() const { return _cms_allocated; }
423 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
425 // Seconds since the last background cms cycle began or ended.
426 double cms_time_since_begin() const;
427 double cms_time_since_end() const;
429 // Higher level statistics--caller must check that valid() returns true before
430 // calling.
432 // Returns bytes promoted per second of wall clock time.
433 double promotion_rate() const;
435 // Returns bytes directly allocated per second of wall clock time.
436 double cms_allocation_rate() const;
438 // Rate at which space in the cms generation is being consumed (sum of the
439 // above two).
440 double cms_consumption_rate() const;
442 // Returns an estimate of the number of seconds until the cms generation will
443 // fill up, assuming no collection work is done.
444 double time_until_cms_gen_full() const;
446 // Returns an estimate of the number of seconds remaining until
447 // the cms generation collection should start.
448 double time_until_cms_start() const;
450 // End of higher level statistics.
452 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
453 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
455 // Update the duty cycle and return the new value.
456 unsigned int icms_update_duty_cycle();
458 // Debugging.
459 void print_on(outputStream* st) const PRODUCT_RETURN;
460 void print() const { print_on(gclog_or_tty); }
461 };
463 // A closure related to weak references processing which
464 // we embed in the CMSCollector, since we need to pass
465 // it to the reference processor for secondary filtering
466 // of references based on reachability of referent;
467 // see role of _is_alive_non_header closure in the
468 // ReferenceProcessor class.
469 // For objects in the CMS generation, this closure checks
470 // if the object is "live" (reachable). Used in weak
471 // reference processing.
472 class CMSIsAliveClosure: public BoolObjectClosure {
473 const MemRegion _span;
474 const CMSBitMap* _bit_map;
476 friend class CMSCollector;
477 public:
478 CMSIsAliveClosure(MemRegion span,
479 CMSBitMap* bit_map):
480 _span(span),
481 _bit_map(bit_map) {
482 assert(!span.is_empty(), "Empty span could spell trouble");
483 }
485 void do_object(oop obj) {
486 assert(false, "not to be invoked");
487 }
489 bool do_object_b(oop obj);
490 };
493 // Implements AbstractRefProcTaskExecutor for CMS.
494 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
495 public:
497 CMSRefProcTaskExecutor(CMSCollector& collector)
498 : _collector(collector)
499 { }
501 // Executes a task using worker threads.
502 virtual void execute(ProcessTask& task);
503 virtual void execute(EnqueueTask& task);
504 private:
505 CMSCollector& _collector;
506 };
509 class CMSCollector: public CHeapObj<mtGC> {
510 friend class VMStructs;
511 friend class ConcurrentMarkSweepThread;
512 friend class ConcurrentMarkSweepGeneration;
513 friend class CompactibleFreeListSpace;
514 friend class CMSParRemarkTask;
515 friend class CMSConcMarkingTask;
516 friend class CMSRefProcTaskProxy;
517 friend class CMSRefProcTaskExecutor;
518 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
519 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
520 friend class PushOrMarkClosure; // to access _restart_addr
521 friend class Par_PushOrMarkClosure; // to access _restart_addr
522 friend class MarkFromRootsClosure; // -- ditto --
523 // ... and for clearing cards
524 friend class Par_MarkFromRootsClosure; // to access _restart_addr
525 // ... and for clearing cards
526 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
527 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
528 friend class PushAndMarkVerifyClosure; // -- ditto --
529 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
530 friend class PushAndMarkClosure; // -- ditto --
531 friend class Par_PushAndMarkClosure; // -- ditto --
532 friend class CMSKeepAliveClosure; // -- ditto --
533 friend class CMSDrainMarkingStackClosure; // -- ditto --
534 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
535 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
536 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
537 friend class VM_CMS_Operation;
538 friend class VM_CMS_Initial_Mark;
539 friend class VM_CMS_Final_Remark;
540 friend class TraceCMSMemoryManagerStats;
542 private:
543 jlong _time_of_last_gc;
544 void update_time_of_last_gc(jlong now) {
545 _time_of_last_gc = now;
546 }
548 OopTaskQueueSet* _task_queues;
550 // Overflow list of grey objects, threaded through mark-word
551 // Manipulated with CAS in the parallel/multi-threaded case.
552 oop _overflow_list;
553 // The following array-pair keeps track of mark words
554 // displaced for accomodating overflow list above.
555 // This code will likely be revisited under RFE#4922830.
556 Stack<oop, mtGC> _preserved_oop_stack;
557 Stack<markOop, mtGC> _preserved_mark_stack;
559 int* _hash_seed;
561 // In support of multi-threaded concurrent phases
562 YieldingFlexibleWorkGang* _conc_workers;
564 // Performance Counters
565 CollectorCounters* _gc_counters;
567 // Initialization Errors
568 bool _completed_initialization;
570 // In support of ExplicitGCInvokesConcurrent
571 static bool _full_gc_requested;
572 unsigned int _collection_count_start;
574 // Should we unload classes this concurrent cycle?
575 bool _should_unload_classes;
576 unsigned int _concurrent_cycles_since_last_unload;
577 unsigned int concurrent_cycles_since_last_unload() const {
578 return _concurrent_cycles_since_last_unload;
579 }
580 // Did we (allow) unload classes in the previous concurrent cycle?
581 bool unloaded_classes_last_cycle() const {
582 return concurrent_cycles_since_last_unload() == 0;
583 }
584 // Root scanning options for perm gen
585 int _roots_scanning_options;
586 int roots_scanning_options() const { return _roots_scanning_options; }
587 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
588 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
590 // Verification support
591 CMSBitMap _verification_mark_bm;
592 void verify_after_remark_work_1();
593 void verify_after_remark_work_2();
595 // true if any verification flag is on.
596 bool _verifying;
597 bool verifying() const { return _verifying; }
598 void set_verifying(bool v) { _verifying = v; }
600 // Collector policy
601 ConcurrentMarkSweepPolicy* _collector_policy;
602 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
604 // XXX Move these to CMSStats ??? FIX ME !!!
605 elapsedTimer _inter_sweep_timer; // time between sweeps
606 elapsedTimer _intra_sweep_timer; // time _in_ sweeps
607 // padded decaying average estimates of the above
608 AdaptivePaddedAverage _inter_sweep_estimate;
609 AdaptivePaddedAverage _intra_sweep_estimate;
611 protected:
612 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
613 MemRegion _span; // span covering above two
614 CardTableRS* _ct; // card table
616 // CMS marking support structures
617 CMSBitMap _markBitMap;
618 CMSBitMap _modUnionTable;
619 CMSMarkStack _markStack;
621 HeapWord* _restart_addr; // in support of marking stack overflow
622 void lower_restart_addr(HeapWord* low);
624 // Counters in support of marking stack / work queue overflow handling:
625 // a non-zero value indicates certain types of overflow events during
626 // the current CMS cycle and could lead to stack resizing efforts at
627 // an opportune future time.
628 size_t _ser_pmc_preclean_ovflw;
629 size_t _ser_pmc_remark_ovflw;
630 size_t _par_pmc_remark_ovflw;
631 size_t _ser_kac_preclean_ovflw;
632 size_t _ser_kac_ovflw;
633 size_t _par_kac_ovflw;
634 NOT_PRODUCT(ssize_t _num_par_pushes;)
636 // ("Weak") Reference processing support
637 ReferenceProcessor* _ref_processor;
638 CMSIsAliveClosure _is_alive_closure;
639 // keep this textually after _markBitMap and _span; c'tor dependency
641 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
642 ModUnionClosure _modUnionClosure;
643 ModUnionClosurePar _modUnionClosurePar;
645 // CMS abstract state machine
646 // initial_state: Idling
647 // next_state(Idling) = {Marking}
648 // next_state(Marking) = {Precleaning, Sweeping}
649 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
650 // next_state(AbortablePreclean) = {FinalMarking}
651 // next_state(FinalMarking) = {Sweeping}
652 // next_state(Sweeping) = {Resizing}
653 // next_state(Resizing) = {Resetting}
654 // next_state(Resetting) = {Idling}
655 // The numeric values below are chosen so that:
656 // . _collectorState <= Idling == post-sweep && pre-mark
657 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
658 // precleaning || abortablePrecleanb
659 public:
660 enum CollectorState {
661 Resizing = 0,
662 Resetting = 1,
663 Idling = 2,
664 InitialMarking = 3,
665 Marking = 4,
666 Precleaning = 5,
667 AbortablePreclean = 6,
668 FinalMarking = 7,
669 Sweeping = 8
670 };
671 protected:
672 static CollectorState _collectorState;
674 // State related to prologue/epilogue invocation for my generations
675 bool _between_prologue_and_epilogue;
677 // Signalling/State related to coordination between fore- and backgroud GC
678 // Note: When the baton has been passed from background GC to foreground GC,
679 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
680 static bool _foregroundGCIsActive; // true iff foreground collector is active or
681 // wants to go active
682 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
683 // yet passed the baton to the foreground GC
685 // Support for CMSScheduleRemark (abortable preclean)
686 bool _abort_preclean;
687 bool _start_sampling;
689 int _numYields;
690 size_t _numDirtyCards;
691 size_t _sweep_count;
692 // number of full gc's since the last concurrent gc.
693 uint _full_gcs_since_conc_gc;
695 // occupancy used for bootstrapping stats
696 double _bootstrap_occupancy;
698 // timer
699 elapsedTimer _timer;
701 // Timing, allocation and promotion statistics, used for scheduling.
702 CMSStats _stats;
704 // Allocation limits installed in the young gen, used only in
705 // CMSIncrementalMode. When an allocation in the young gen would cross one of
706 // these limits, the cms generation is notified and the cms thread is started
707 // or stopped, respectively.
708 HeapWord* _icms_start_limit;
709 HeapWord* _icms_stop_limit;
711 enum CMS_op_type {
712 CMS_op_checkpointRootsInitial,
713 CMS_op_checkpointRootsFinal
714 };
716 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
717 bool stop_world_and_do(CMS_op_type op);
719 OopTaskQueueSet* task_queues() { return _task_queues; }
720 int* hash_seed(int i) { return &_hash_seed[i]; }
721 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
723 // Support for parallelizing Eden rescan in CMS remark phase
724 void sample_eden(); // ... sample Eden space top
726 private:
727 // Support for parallelizing young gen rescan in CMS remark phase
728 Generation* _young_gen; // the younger gen
729 HeapWord** _top_addr; // ... Top of Eden
730 HeapWord** _end_addr; // ... End of Eden
731 HeapWord** _eden_chunk_array; // ... Eden partitioning array
732 size_t _eden_chunk_index; // ... top (exclusive) of array
733 size_t _eden_chunk_capacity; // ... max entries in array
735 // Support for parallelizing survivor space rescan
736 HeapWord** _survivor_chunk_array;
737 size_t _survivor_chunk_index;
738 size_t _survivor_chunk_capacity;
739 size_t* _cursor;
740 ChunkArray* _survivor_plab_array;
742 // Support for marking stack overflow handling
743 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
744 bool par_take_from_overflow_list(size_t num,
745 OopTaskQueue* to_work_q,
746 int no_of_gc_threads);
747 void push_on_overflow_list(oop p);
748 void par_push_on_overflow_list(oop p);
749 // the following is, obviously, not, in general, "MT-stable"
750 bool overflow_list_is_empty() const;
752 void preserve_mark_if_necessary(oop p);
753 void par_preserve_mark_if_necessary(oop p);
754 void preserve_mark_work(oop p, markOop m);
755 void restore_preserved_marks_if_any();
756 NOT_PRODUCT(bool no_preserved_marks() const;)
757 // in support of testing overflow code
758 NOT_PRODUCT(int _overflow_counter;)
759 NOT_PRODUCT(bool simulate_overflow();) // sequential
760 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
762 // CMS work methods
763 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
765 // a return value of false indicates failure due to stack overflow
766 bool markFromRootsWork(bool asynch); // concurrent marking work
768 public: // FIX ME!!! only for testing
769 bool do_marking_st(bool asynch); // single-threaded marking
770 bool do_marking_mt(bool asynch); // multi-threaded marking
772 private:
774 // concurrent precleaning work
775 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
776 ScanMarkedObjectsAgainCarefullyClosure* cl);
777 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
778 ScanMarkedObjectsAgainCarefullyClosure* cl);
779 // Does precleaning work, returning a quantity indicative of
780 // the amount of "useful work" done.
781 size_t preclean_work(bool clean_refs, bool clean_survivors);
782 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
783 void abortable_preclean(); // Preclean while looking for possible abort
784 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
785 // Helper function for above; merge-sorts the per-thread plab samples
786 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
787 // Resets (i.e. clears) the per-thread plab sample vectors
788 void reset_survivor_plab_arrays();
790 // final (second) checkpoint work
791 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
792 bool init_mark_was_synchronous);
793 // work routine for parallel version of remark
794 void do_remark_parallel();
795 // work routine for non-parallel version of remark
796 void do_remark_non_parallel();
797 // reference processing work routine (during second checkpoint)
798 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
800 // concurrent sweeping work
801 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
803 // (concurrent) resetting of support data structures
804 void reset(bool asynch);
806 // Clear _expansion_cause fields of constituent generations
807 void clear_expansion_cause();
809 // An auxilliary method used to record the ends of
810 // used regions of each generation to limit the extent of sweep
811 void save_sweep_limits();
813 // Resize the generations included in the collector.
814 void compute_new_size();
816 // A work method used by foreground collection to determine
817 // what type of collection (compacting or not, continuing or fresh)
818 // it should do.
819 void decide_foreground_collection_type(bool clear_all_soft_refs,
820 bool* should_compact, bool* should_start_over);
822 // A work method used by the foreground collector to do
823 // a mark-sweep-compact.
824 void do_compaction_work(bool clear_all_soft_refs);
826 // A work method used by the foreground collector to do
827 // a mark-sweep, after taking over from a possibly on-going
828 // concurrent mark-sweep collection.
829 void do_mark_sweep_work(bool clear_all_soft_refs,
830 CollectorState first_state, bool should_start_over);
832 // If the backgrould GC is active, acquire control from the background
833 // GC and do the collection.
834 void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
836 // For synchronizing passing of control from background to foreground
837 // GC. waitForForegroundGC() is called by the background
838 // collector. It if had to wait for a foreground collection,
839 // it returns true and the background collection should assume
840 // that the collection was finished by the foreground
841 // collector.
842 bool waitForForegroundGC();
844 // Incremental mode triggering: recompute the icms duty cycle and set the
845 // allocation limits in the young gen.
846 void icms_update_allocation_limits();
848 size_t block_size_using_printezis_bits(HeapWord* addr) const;
849 size_t block_size_if_printezis_bits(HeapWord* addr) const;
850 HeapWord* next_card_start_after_block(HeapWord* addr) const;
852 void setup_cms_unloading_and_verification_state();
853 public:
854 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
855 CardTableRS* ct,
856 ConcurrentMarkSweepPolicy* cp);
857 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
859 ReferenceProcessor* ref_processor() { return _ref_processor; }
860 void ref_processor_init();
862 Mutex* bitMapLock() const { return _markBitMap.lock(); }
863 static CollectorState abstract_state() { return _collectorState; }
865 bool should_abort_preclean() const; // Whether preclean should be aborted.
866 size_t get_eden_used() const;
867 size_t get_eden_capacity() const;
869 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
871 // locking checks
872 NOT_PRODUCT(static bool have_cms_token();)
874 // XXXPERM bool should_collect(bool full, size_t size, bool tlab);
875 bool shouldConcurrentCollect();
877 void collect(bool full,
878 bool clear_all_soft_refs,
879 size_t size,
880 bool tlab);
881 void collect_in_background(bool clear_all_soft_refs);
882 void collect_in_foreground(bool clear_all_soft_refs);
884 // In support of ExplicitGCInvokesConcurrent
885 static void request_full_gc(unsigned int full_gc_count);
886 // Should we unload classes in a particular concurrent cycle?
887 bool should_unload_classes() const {
888 return _should_unload_classes;
889 }
890 void update_should_unload_classes();
892 void direct_allocated(HeapWord* start, size_t size);
894 // Object is dead if not marked and current phase is sweeping.
895 bool is_dead_obj(oop obj) const;
897 // After a promotion (of "start"), do any necessary marking.
898 // If "par", then it's being done by a parallel GC thread.
899 // The last two args indicate if we need precise marking
900 // and if so the size of the object so it can be dirtied
901 // in its entirety.
902 void promoted(bool par, HeapWord* start,
903 bool is_obj_array, size_t obj_size);
905 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
906 size_t word_size);
908 void getFreelistLocks() const;
909 void releaseFreelistLocks() const;
910 bool haveFreelistLocks() const;
912 // GC prologue and epilogue
913 void gc_prologue(bool full);
914 void gc_epilogue(bool full);
916 jlong time_of_last_gc(jlong now) {
917 if (_collectorState <= Idling) {
918 // gc not in progress
919 return _time_of_last_gc;
920 } else {
921 // collection in progress
922 return now;
923 }
924 }
926 // Support for parallel remark of survivor space
927 void* get_data_recorder(int thr_num);
929 CMSBitMap* markBitMap() { return &_markBitMap; }
930 void directAllocated(HeapWord* start, size_t size);
932 // main CMS steps and related support
933 void checkpointRootsInitial(bool asynch);
934 bool markFromRoots(bool asynch); // a return value of false indicates failure
935 // due to stack overflow
936 void preclean();
937 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
938 bool init_mark_was_synchronous);
939 void sweep(bool asynch);
941 // Check that the currently executing thread is the expected
942 // one (foreground collector or background collector).
943 static void check_correct_thread_executing() PRODUCT_RETURN;
944 // XXXPERM void print_statistics() PRODUCT_RETURN;
946 bool is_cms_reachable(HeapWord* addr);
948 // Performance Counter Support
949 CollectorCounters* counters() { return _gc_counters; }
951 // timer stuff
952 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
953 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
954 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
955 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
957 int yields() { return _numYields; }
958 void resetYields() { _numYields = 0; }
959 void incrementYields() { _numYields++; }
960 void resetNumDirtyCards() { _numDirtyCards = 0; }
961 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
962 size_t numDirtyCards() { return _numDirtyCards; }
964 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
965 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
966 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
967 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
968 size_t sweep_count() const { return _sweep_count; }
969 void increment_sweep_count() { _sweep_count++; }
971 // Timers/stats for gc scheduling and incremental mode pacing.
972 CMSStats& stats() { return _stats; }
974 // Convenience methods that check whether CMSIncrementalMode is enabled and
975 // forward to the corresponding methods in ConcurrentMarkSweepThread.
976 static void start_icms();
977 static void stop_icms(); // Called at the end of the cms cycle.
978 static void disable_icms(); // Called before a foreground collection.
979 static void enable_icms(); // Called after a foreground collection.
980 void icms_wait(); // Called at yield points.
982 // Adaptive size policy
983 CMSAdaptiveSizePolicy* size_policy();
984 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
986 // debugging
987 void verify();
988 bool verify_after_remark();
989 void verify_ok_to_terminate() const PRODUCT_RETURN;
990 void verify_work_stacks_empty() const PRODUCT_RETURN;
991 void verify_overflow_empty() const PRODUCT_RETURN;
993 // convenience methods in support of debugging
994 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
995 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
997 // accessors
998 CMSMarkStack* verification_mark_stack() { return &_markStack; }
999 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1001 // Initialization errors
1002 bool completed_initialization() { return _completed_initialization; }
1003 };
1005 class CMSExpansionCause : public AllStatic {
1006 public:
1007 enum Cause {
1008 _no_expansion,
1009 _satisfy_free_ratio,
1010 _satisfy_promotion,
1011 _satisfy_allocation,
1012 _allocate_par_lab,
1013 _allocate_par_spooling_space,
1014 _adaptive_size_policy
1015 };
1016 // Return a string describing the cause of the expansion.
1017 static const char* to_string(CMSExpansionCause::Cause cause);
1018 };
1020 class ConcurrentMarkSweepGeneration: public CardGeneration {
1021 friend class VMStructs;
1022 friend class ConcurrentMarkSweepThread;
1023 friend class ConcurrentMarkSweep;
1024 friend class CMSCollector;
1025 protected:
1026 static CMSCollector* _collector; // the collector that collects us
1027 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1029 // Performance Counters
1030 GenerationCounters* _gen_counters;
1031 GSpaceCounters* _space_counters;
1033 // Words directly allocated, used by CMSStats.
1034 size_t _direct_allocated_words;
1036 // Non-product stat counters
1037 NOT_PRODUCT(
1038 size_t _numObjectsPromoted;
1039 size_t _numWordsPromoted;
1040 size_t _numObjectsAllocated;
1041 size_t _numWordsAllocated;
1042 )
1044 // Used for sizing decisions
1045 bool _incremental_collection_failed;
1046 bool incremental_collection_failed() {
1047 return _incremental_collection_failed;
1048 }
1049 void set_incremental_collection_failed() {
1050 _incremental_collection_failed = true;
1051 }
1052 void clear_incremental_collection_failed() {
1053 _incremental_collection_failed = false;
1054 }
1056 // accessors
1057 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1058 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1060 private:
1061 // For parallel young-gen GC support.
1062 CMSParGCThreadState** _par_gc_thread_states;
1064 // Reason generation was expanded
1065 CMSExpansionCause::Cause _expansion_cause;
1067 // In support of MinChunkSize being larger than min object size
1068 const double _dilatation_factor;
1070 enum CollectionTypes {
1071 Concurrent_collection_type = 0,
1072 MS_foreground_collection_type = 1,
1073 MSC_foreground_collection_type = 2,
1074 Unknown_collection_type = 3
1075 };
1077 CollectionTypes _debug_collection_type;
1079 // Fraction of current occupancy at which to start a CMS collection which
1080 // will collect this generation (at least).
1081 double _initiating_occupancy;
1083 protected:
1084 // Shrink generation by specified size (returns false if unable to shrink)
1085 virtual void shrink_by(size_t bytes);
1087 // Update statistics for GC
1088 virtual void update_gc_stats(int level, bool full);
1090 // Maximum available space in the generation (including uncommitted)
1091 // space.
1092 size_t max_available() const;
1094 // getter and initializer for _initiating_occupancy field.
1095 double initiating_occupancy() const { return _initiating_occupancy; }
1096 void init_initiating_occupancy(intx io, intx tr);
1098 public:
1099 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1100 int level, CardTableRS* ct,
1101 bool use_adaptive_freelists,
1102 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1104 // Accessors
1105 CMSCollector* collector() const { return _collector; }
1106 static void set_collector(CMSCollector* collector) {
1107 assert(_collector == NULL, "already set");
1108 _collector = collector;
1109 }
1110 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1112 Mutex* freelistLock() const;
1114 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1116 // Adaptive size policy
1117 CMSAdaptiveSizePolicy* size_policy();
1119 bool refs_discovery_is_atomic() const { return false; }
1120 bool refs_discovery_is_mt() const {
1121 // Note: CMS does MT-discovery during the parallel-remark
1122 // phases. Use ReferenceProcessorMTMutator to make refs
1123 // discovery MT-safe during such phases or other parallel
1124 // discovery phases in the future. This may all go away
1125 // if/when we decide that refs discovery is sufficiently
1126 // rare that the cost of the CAS's involved is in the
1127 // noise. That's a measurement that should be done, and
1128 // the code simplified if that turns out to be the case.
1129 return ConcGCThreads > 1;
1130 }
1132 // Override
1133 virtual void ref_processor_init();
1135 // Grow generation by specified size (returns false if unable to grow)
1136 bool grow_by(size_t bytes);
1137 // Grow generation to reserved size.
1138 bool grow_to_reserved();
1140 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1142 // Space enquiries
1143 size_t capacity() const;
1144 size_t used() const;
1145 size_t free() const;
1146 double occupancy() const { return ((double)used())/((double)capacity()); }
1147 size_t contiguous_available() const;
1148 size_t unsafe_max_alloc_nogc() const;
1150 // over-rides
1151 MemRegion used_region() const;
1152 MemRegion used_region_at_save_marks() const;
1154 // Does a "full" (forced) collection invoked on this generation collect
1155 // all younger generations as well? Note that the second conjunct is a
1156 // hack to allow the collection of the younger gen first if the flag is
1157 // set. This is better than using th policy's should_collect_gen0_first()
1158 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1159 virtual bool full_collects_younger_generations() const {
1160 return UseCMSCompactAtFullCollection && !CollectGen0First;
1161 }
1163 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1165 // Support for compaction
1166 CompactibleSpace* first_compaction_space() const;
1167 // Adjust quantites in the generation affected by
1168 // the compaction.
1169 void reset_after_compaction();
1171 // Allocation support
1172 HeapWord* allocate(size_t size, bool tlab);
1173 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1174 oop promote(oop obj, size_t obj_size);
1175 HeapWord* par_allocate(size_t size, bool tlab) {
1176 return allocate(size, tlab);
1177 }
1179 // Incremental mode triggering.
1180 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1181 size_t word_size);
1183 // Used by CMSStats to track direct allocation. The value is sampled and
1184 // reset after each young gen collection.
1185 size_t direct_allocated_words() const { return _direct_allocated_words; }
1186 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1188 // Overrides for parallel promotion.
1189 virtual oop par_promote(int thread_num,
1190 oop obj, markOop m, size_t word_sz);
1191 // This one should not be called for CMS.
1192 virtual void par_promote_alloc_undo(int thread_num,
1193 HeapWord* obj, size_t word_sz);
1194 virtual void par_promote_alloc_done(int thread_num);
1195 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1197 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1199 // Inform this (non-young) generation that a promotion failure was
1200 // encountered during a collection of a younger generation that
1201 // promotes into this generation.
1202 virtual void promotion_failure_occurred();
1204 bool should_collect(bool full, size_t size, bool tlab);
1205 virtual bool should_concurrent_collect() const;
1206 virtual bool is_too_full() const;
1207 void collect(bool full,
1208 bool clear_all_soft_refs,
1209 size_t size,
1210 bool tlab);
1212 HeapWord* expand_and_allocate(size_t word_size,
1213 bool tlab,
1214 bool parallel = false);
1216 // GC prologue and epilogue
1217 void gc_prologue(bool full);
1218 void gc_prologue_work(bool full, bool registerClosure,
1219 ModUnionClosure* modUnionClosure);
1220 void gc_epilogue(bool full);
1221 void gc_epilogue_work(bool full);
1223 // Time since last GC of this generation
1224 jlong time_of_last_gc(jlong now) {
1225 return collector()->time_of_last_gc(now);
1226 }
1227 void update_time_of_last_gc(jlong now) {
1228 collector()-> update_time_of_last_gc(now);
1229 }
1231 // Allocation failure
1232 void expand(size_t bytes, size_t expand_bytes,
1233 CMSExpansionCause::Cause cause);
1234 virtual bool expand(size_t bytes, size_t expand_bytes);
1235 void shrink(size_t bytes);
1236 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1237 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1239 // Iteration support and related enquiries
1240 void save_marks();
1241 bool no_allocs_since_save_marks();
1242 void object_iterate_since_last_GC(ObjectClosure* cl);
1243 void younger_refs_iterate(OopsInGenClosure* cl);
1245 // Iteration support specific to CMS generations
1246 void save_sweep_limit();
1248 // More iteration support
1249 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1250 virtual void oop_iterate(ExtendedOopClosure* cl);
1251 virtual void safe_object_iterate(ObjectClosure* cl);
1252 virtual void object_iterate(ObjectClosure* cl);
1254 // Need to declare the full complement of closures, whether we'll
1255 // override them or not, or get message from the compiler:
1256 // oop_since_save_marks_iterate_nv hides virtual function...
1257 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1258 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1259 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1261 // Smart allocation XXX -- move to CFLSpace?
1262 void setNearLargestChunk();
1263 bool isNearLargestChunk(HeapWord* addr);
1265 // Get the chunk at the end of the space. Delagates to
1266 // the space.
1267 FreeChunk* find_chunk_at_end();
1269 void post_compact();
1271 // Debugging
1272 void prepare_for_verify();
1273 void verify();
1274 void print_statistics() PRODUCT_RETURN;
1276 // Performance Counters support
1277 virtual void update_counters();
1278 virtual void update_counters(size_t used);
1279 void initialize_performance_counters();
1280 CollectorCounters* counters() { return collector()->counters(); }
1282 // Support for parallel remark of survivor space
1283 void* get_data_recorder(int thr_num) {
1284 //Delegate to collector
1285 return collector()->get_data_recorder(thr_num);
1286 }
1288 // Printing
1289 const char* name() const;
1290 virtual const char* short_name() const { return "CMS"; }
1291 void print() const;
1292 void printOccupancy(const char* s);
1293 bool must_be_youngest() const { return false; }
1294 bool must_be_oldest() const { return true; }
1296 void compute_new_size();
1298 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1299 void rotate_debug_collection_type();
1300 };
1302 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1304 // Return the size policy from the heap's collector
1305 // policy casted to CMSAdaptiveSizePolicy*.
1306 CMSAdaptiveSizePolicy* cms_size_policy() const;
1308 // Resize the generation based on the adaptive size
1309 // policy.
1310 void resize(size_t cur_promo, size_t desired_promo);
1312 // Return the GC counters from the collector policy
1313 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1315 virtual void shrink_by(size_t bytes);
1317 public:
1318 virtual void compute_new_size();
1319 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1320 int level, CardTableRS* ct,
1321 bool use_adaptive_freelists,
1322 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1323 dictionaryChoice) :
1324 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1325 use_adaptive_freelists, dictionaryChoice) {}
1327 virtual const char* short_name() const { return "ASCMS"; }
1328 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1330 virtual void update_counters();
1331 virtual void update_counters(size_t used);
1332 };
1334 //
1335 // Closures of various sorts used by CMS to accomplish its work
1336 //
1338 // This closure is used to check that a certain set of oops is empty.
1339 class FalseClosure: public OopClosure {
1340 public:
1341 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1342 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1343 };
1345 // This closure is used to do concurrent marking from the roots
1346 // following the first checkpoint.
1347 class MarkFromRootsClosure: public BitMapClosure {
1348 CMSCollector* _collector;
1349 MemRegion _span;
1350 CMSBitMap* _bitMap;
1351 CMSBitMap* _mut;
1352 CMSMarkStack* _markStack;
1353 bool _yield;
1354 int _skipBits;
1355 HeapWord* _finger;
1356 HeapWord* _threshold;
1357 DEBUG_ONLY(bool _verifying;)
1359 public:
1360 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1361 CMSBitMap* bitMap,
1362 CMSMarkStack* markStack,
1363 bool should_yield, bool verifying = false);
1364 bool do_bit(size_t offset);
1365 void reset(HeapWord* addr);
1366 inline void do_yield_check();
1368 private:
1369 void scanOopsInOop(HeapWord* ptr);
1370 void do_yield_work();
1371 };
1373 // This closure is used to do concurrent multi-threaded
1374 // marking from the roots following the first checkpoint.
1375 // XXX This should really be a subclass of The serial version
1376 // above, but i have not had the time to refactor things cleanly.
1377 // That willbe done for Dolphin.
1378 class Par_MarkFromRootsClosure: public BitMapClosure {
1379 CMSCollector* _collector;
1380 MemRegion _whole_span;
1381 MemRegion _span;
1382 CMSBitMap* _bit_map;
1383 CMSBitMap* _mut;
1384 OopTaskQueue* _work_queue;
1385 CMSMarkStack* _overflow_stack;
1386 bool _yield;
1387 int _skip_bits;
1388 HeapWord* _finger;
1389 HeapWord* _threshold;
1390 CMSConcMarkingTask* _task;
1391 public:
1392 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1393 MemRegion span,
1394 CMSBitMap* bit_map,
1395 OopTaskQueue* work_queue,
1396 CMSMarkStack* overflow_stack,
1397 bool should_yield);
1398 bool do_bit(size_t offset);
1399 inline void do_yield_check();
1401 private:
1402 void scan_oops_in_oop(HeapWord* ptr);
1403 void do_yield_work();
1404 bool get_work_from_overflow_stack();
1405 };
1407 // The following closures are used to do certain kinds of verification of
1408 // CMS marking.
1409 class PushAndMarkVerifyClosure: public CMSOopClosure {
1410 CMSCollector* _collector;
1411 MemRegion _span;
1412 CMSBitMap* _verification_bm;
1413 CMSBitMap* _cms_bm;
1414 CMSMarkStack* _mark_stack;
1415 protected:
1416 void do_oop(oop p);
1417 template <class T> inline void do_oop_work(T *p) {
1418 oop obj = oopDesc::load_decode_heap_oop(p);
1419 do_oop(obj);
1420 }
1421 public:
1422 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1423 MemRegion span,
1424 CMSBitMap* verification_bm,
1425 CMSBitMap* cms_bm,
1426 CMSMarkStack* mark_stack);
1427 void do_oop(oop* p);
1428 void do_oop(narrowOop* p);
1430 // Deal with a stack overflow condition
1431 void handle_stack_overflow(HeapWord* lost);
1432 };
1434 class MarkFromRootsVerifyClosure: public BitMapClosure {
1435 CMSCollector* _collector;
1436 MemRegion _span;
1437 CMSBitMap* _verification_bm;
1438 CMSBitMap* _cms_bm;
1439 CMSMarkStack* _mark_stack;
1440 HeapWord* _finger;
1441 PushAndMarkVerifyClosure _pam_verify_closure;
1442 public:
1443 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1444 CMSBitMap* verification_bm,
1445 CMSBitMap* cms_bm,
1446 CMSMarkStack* mark_stack);
1447 bool do_bit(size_t offset);
1448 void reset(HeapWord* addr);
1449 };
1452 // This closure is used to check that a certain set of bits is
1453 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1454 class FalseBitMapClosure: public BitMapClosure {
1455 public:
1456 bool do_bit(size_t offset) {
1457 guarantee(false, "Should not have a 1 bit");
1458 return true;
1459 }
1460 };
1462 // This closure is used during the second checkpointing phase
1463 // to rescan the marked objects on the dirty cards in the mod
1464 // union table and the card table proper. It's invoked via
1465 // MarkFromDirtyCardsClosure below. It uses either
1466 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1467 // declared in genOopClosures.hpp to accomplish some of its work.
1468 // In the parallel case the bitMap is shared, so access to
1469 // it needs to be suitably synchronized for updates by embedded
1470 // closures that update it; however, this closure itself only
1471 // reads the bit_map and because it is idempotent, is immune to
1472 // reading stale values.
1473 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1474 #ifdef ASSERT
1475 CMSCollector* _collector;
1476 MemRegion _span;
1477 union {
1478 CMSMarkStack* _mark_stack;
1479 OopTaskQueue* _work_queue;
1480 };
1481 #endif // ASSERT
1482 bool _parallel;
1483 CMSBitMap* _bit_map;
1484 union {
1485 MarkRefsIntoAndScanClosure* _scan_closure;
1486 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1487 };
1489 public:
1490 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1491 MemRegion span,
1492 ReferenceProcessor* rp,
1493 CMSBitMap* bit_map,
1494 CMSMarkStack* mark_stack,
1495 MarkRefsIntoAndScanClosure* cl):
1496 #ifdef ASSERT
1497 _collector(collector),
1498 _span(span),
1499 _mark_stack(mark_stack),
1500 #endif // ASSERT
1501 _parallel(false),
1502 _bit_map(bit_map),
1503 _scan_closure(cl) { }
1505 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1506 MemRegion span,
1507 ReferenceProcessor* rp,
1508 CMSBitMap* bit_map,
1509 OopTaskQueue* work_queue,
1510 Par_MarkRefsIntoAndScanClosure* cl):
1511 #ifdef ASSERT
1512 _collector(collector),
1513 _span(span),
1514 _work_queue(work_queue),
1515 #endif // ASSERT
1516 _parallel(true),
1517 _bit_map(bit_map),
1518 _par_scan_closure(cl) { }
1520 void do_object(oop obj) {
1521 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1522 }
1523 bool do_object_b(oop obj) {
1524 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1525 return false;
1526 }
1527 bool do_object_bm(oop p, MemRegion mr);
1528 };
1530 // This closure is used during the second checkpointing phase
1531 // to rescan the marked objects on the dirty cards in the mod
1532 // union table and the card table proper. It invokes
1533 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1534 // In the parallel case, the bit map is shared and requires
1535 // synchronized access.
1536 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1537 CompactibleFreeListSpace* _space;
1538 ScanMarkedObjectsAgainClosure _scan_cl;
1539 size_t _num_dirty_cards;
1541 public:
1542 MarkFromDirtyCardsClosure(CMSCollector* collector,
1543 MemRegion span,
1544 CompactibleFreeListSpace* space,
1545 CMSBitMap* bit_map,
1546 CMSMarkStack* mark_stack,
1547 MarkRefsIntoAndScanClosure* cl):
1548 _space(space),
1549 _num_dirty_cards(0),
1550 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1551 mark_stack, cl) { }
1553 MarkFromDirtyCardsClosure(CMSCollector* collector,
1554 MemRegion span,
1555 CompactibleFreeListSpace* space,
1556 CMSBitMap* bit_map,
1557 OopTaskQueue* work_queue,
1558 Par_MarkRefsIntoAndScanClosure* cl):
1559 _space(space),
1560 _num_dirty_cards(0),
1561 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1562 work_queue, cl) { }
1564 void do_MemRegion(MemRegion mr);
1565 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1566 size_t num_dirty_cards() { return _num_dirty_cards; }
1567 };
1569 // This closure is used in the non-product build to check
1570 // that there are no MemRegions with a certain property.
1571 class FalseMemRegionClosure: public MemRegionClosure {
1572 void do_MemRegion(MemRegion mr) {
1573 guarantee(!mr.is_empty(), "Shouldn't be empty");
1574 guarantee(false, "Should never be here");
1575 }
1576 };
1578 // This closure is used during the precleaning phase
1579 // to "carefully" rescan marked objects on dirty cards.
1580 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1581 // to accomplish some of its work.
1582 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1583 CMSCollector* _collector;
1584 MemRegion _span;
1585 bool _yield;
1586 Mutex* _freelistLock;
1587 CMSBitMap* _bitMap;
1588 CMSMarkStack* _markStack;
1589 MarkRefsIntoAndScanClosure* _scanningClosure;
1591 public:
1592 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1593 MemRegion span,
1594 CMSBitMap* bitMap,
1595 CMSMarkStack* markStack,
1596 MarkRefsIntoAndScanClosure* cl,
1597 bool should_yield):
1598 _collector(collector),
1599 _span(span),
1600 _yield(should_yield),
1601 _bitMap(bitMap),
1602 _markStack(markStack),
1603 _scanningClosure(cl) {
1604 }
1606 void do_object(oop p) {
1607 guarantee(false, "call do_object_careful instead");
1608 }
1610 size_t do_object_careful(oop p) {
1611 guarantee(false, "Unexpected caller");
1612 return 0;
1613 }
1615 size_t do_object_careful_m(oop p, MemRegion mr);
1617 void setFreelistLock(Mutex* m) {
1618 _freelistLock = m;
1619 _scanningClosure->set_freelistLock(m);
1620 }
1622 private:
1623 inline bool do_yield_check();
1625 void do_yield_work();
1626 };
1628 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1629 CMSCollector* _collector;
1630 MemRegion _span;
1631 bool _yield;
1632 CMSBitMap* _bit_map;
1633 CMSMarkStack* _mark_stack;
1634 PushAndMarkClosure* _scanning_closure;
1635 unsigned int _before_count;
1637 public:
1638 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1639 MemRegion span,
1640 CMSBitMap* bit_map,
1641 CMSMarkStack* mark_stack,
1642 PushAndMarkClosure* cl,
1643 unsigned int before_count,
1644 bool should_yield):
1645 _collector(collector),
1646 _span(span),
1647 _yield(should_yield),
1648 _bit_map(bit_map),
1649 _mark_stack(mark_stack),
1650 _scanning_closure(cl),
1651 _before_count(before_count)
1652 { }
1654 void do_object(oop p) {
1655 guarantee(false, "call do_object_careful instead");
1656 }
1658 size_t do_object_careful(oop p);
1660 size_t do_object_careful_m(oop p, MemRegion mr) {
1661 guarantee(false, "Unexpected caller");
1662 return 0;
1663 }
1665 private:
1666 inline void do_yield_check();
1667 void do_yield_work();
1668 };
1670 // This closure is used to accomplish the sweeping work
1671 // after the second checkpoint but before the concurrent reset
1672 // phase.
1673 //
1674 // Terminology
1675 // left hand chunk (LHC) - block of one or more chunks currently being
1676 // coalesced. The LHC is available for coalescing with a new chunk.
1677 // right hand chunk (RHC) - block that is currently being swept that is
1678 // free or garbage that can be coalesced with the LHC.
1679 // _inFreeRange is true if there is currently a LHC
1680 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1681 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1682 // _freeFinger is the address of the current LHC
1683 class SweepClosure: public BlkClosureCareful {
1684 CMSCollector* _collector; // collector doing the work
1685 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1686 CompactibleFreeListSpace* _sp; // Space being swept
1687 HeapWord* _limit;// the address at or above which the sweep should stop
1688 // because we do not expect newly garbage blocks
1689 // eligible for sweeping past that address.
1690 Mutex* _freelistLock; // Free list lock (in space)
1691 CMSBitMap* _bitMap; // Marking bit map (in
1692 // generation)
1693 bool _inFreeRange; // Indicates if we are in the
1694 // midst of a free run
1695 bool _freeRangeInFreeLists;
1696 // Often, we have just found
1697 // a free chunk and started
1698 // a new free range; we do not
1699 // eagerly remove this chunk from
1700 // the free lists unless there is
1701 // a possibility of coalescing.
1702 // When true, this flag indicates
1703 // that the _freeFinger below
1704 // points to a potentially free chunk
1705 // that may still be in the free lists
1706 bool _lastFreeRangeCoalesced;
1707 // free range contains chunks
1708 // coalesced
1709 bool _yield;
1710 // Whether sweeping should be
1711 // done with yields. For instance
1712 // when done by the foreground
1713 // collector we shouldn't yield.
1714 HeapWord* _freeFinger; // When _inFreeRange is set, the
1715 // pointer to the "left hand
1716 // chunk"
1717 size_t _freeRangeSize;
1718 // When _inFreeRange is set, this
1719 // indicates the accumulated size
1720 // of the "left hand chunk"
1721 NOT_PRODUCT(
1722 size_t _numObjectsFreed;
1723 size_t _numWordsFreed;
1724 size_t _numObjectsLive;
1725 size_t _numWordsLive;
1726 size_t _numObjectsAlreadyFree;
1727 size_t _numWordsAlreadyFree;
1728 FreeChunk* _last_fc;
1729 )
1730 private:
1731 // Code that is common to a free chunk or garbage when
1732 // encountered during sweeping.
1733 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1734 // Process a free chunk during sweeping.
1735 void do_already_free_chunk(FreeChunk *fc);
1736 // Work method called when processing an already free or a
1737 // freshly garbage chunk to do a lookahead and possibly a
1738 // premptive flush if crossing over _limit.
1739 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1740 // Process a garbage chunk during sweeping.
1741 size_t do_garbage_chunk(FreeChunk *fc);
1742 // Process a live chunk during sweeping.
1743 size_t do_live_chunk(FreeChunk* fc);
1745 // Accessors.
1746 HeapWord* freeFinger() const { return _freeFinger; }
1747 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1748 bool inFreeRange() const { return _inFreeRange; }
1749 void set_inFreeRange(bool v) { _inFreeRange = v; }
1750 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1751 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1752 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1753 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1755 // Initialize a free range.
1756 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1757 // Return this chunk to the free lists.
1758 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1760 // Check if we should yield and do so when necessary.
1761 inline void do_yield_check(HeapWord* addr);
1763 // Yield
1764 void do_yield_work(HeapWord* addr);
1766 // Debugging/Printing
1767 void print_free_block_coalesced(FreeChunk* fc) const;
1769 public:
1770 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1771 CMSBitMap* bitMap, bool should_yield);
1772 ~SweepClosure() PRODUCT_RETURN;
1774 size_t do_blk_careful(HeapWord* addr);
1775 void print() const { print_on(tty); }
1776 void print_on(outputStream *st) const;
1777 };
1779 // Closures related to weak references processing
1781 // During CMS' weak reference processing, this is a
1782 // work-routine/closure used to complete transitive
1783 // marking of objects as live after a certain point
1784 // in which an initial set has been completely accumulated.
1785 // This closure is currently used both during the final
1786 // remark stop-world phase, as well as during the concurrent
1787 // precleaning of the discovered reference lists.
1788 class CMSDrainMarkingStackClosure: public VoidClosure {
1789 CMSCollector* _collector;
1790 MemRegion _span;
1791 CMSMarkStack* _mark_stack;
1792 CMSBitMap* _bit_map;
1793 CMSKeepAliveClosure* _keep_alive;
1794 bool _concurrent_precleaning;
1795 public:
1796 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1797 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1798 CMSKeepAliveClosure* keep_alive,
1799 bool cpc):
1800 _collector(collector),
1801 _span(span),
1802 _bit_map(bit_map),
1803 _mark_stack(mark_stack),
1804 _keep_alive(keep_alive),
1805 _concurrent_precleaning(cpc) {
1806 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1807 "Mismatch");
1808 }
1810 void do_void();
1811 };
1813 // A parallel version of CMSDrainMarkingStackClosure above.
1814 class CMSParDrainMarkingStackClosure: public VoidClosure {
1815 CMSCollector* _collector;
1816 MemRegion _span;
1817 OopTaskQueue* _work_queue;
1818 CMSBitMap* _bit_map;
1819 CMSInnerParMarkAndPushClosure _mark_and_push;
1821 public:
1822 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1823 MemRegion span, CMSBitMap* bit_map,
1824 OopTaskQueue* work_queue):
1825 _collector(collector),
1826 _span(span),
1827 _bit_map(bit_map),
1828 _work_queue(work_queue),
1829 _mark_and_push(collector, span, bit_map, work_queue) { }
1831 public:
1832 void trim_queue(uint max);
1833 void do_void();
1834 };
1836 // Allow yielding or short-circuiting of reference list
1837 // prelceaning work.
1838 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1839 CMSCollector* _collector;
1840 void do_yield_work();
1841 public:
1842 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1843 _collector(collector) {}
1844 virtual bool should_return();
1845 };
1848 // Convenience class that locks free list locks for given CMS collector
1849 class FreelistLocker: public StackObj {
1850 private:
1851 CMSCollector* _collector;
1852 public:
1853 FreelistLocker(CMSCollector* collector):
1854 _collector(collector) {
1855 _collector->getFreelistLocks();
1856 }
1858 ~FreelistLocker() {
1859 _collector->releaseFreelistLocks();
1860 }
1861 };
1863 // Mark all dead objects in a given space.
1864 class MarkDeadObjectsClosure: public BlkClosure {
1865 const CMSCollector* _collector;
1866 const CompactibleFreeListSpace* _sp;
1867 CMSBitMap* _live_bit_map;
1868 CMSBitMap* _dead_bit_map;
1869 public:
1870 MarkDeadObjectsClosure(const CMSCollector* collector,
1871 const CompactibleFreeListSpace* sp,
1872 CMSBitMap *live_bit_map,
1873 CMSBitMap *dead_bit_map) :
1874 _collector(collector),
1875 _sp(sp),
1876 _live_bit_map(live_bit_map),
1877 _dead_bit_map(dead_bit_map) {}
1878 size_t do_blk(HeapWord* addr);
1879 };
1881 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1883 public:
1884 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1885 };
1888 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP