Wed, 10 Apr 2013 14:26:49 +0200
8011872: Include Bit Map addresses in the hs_err files
Reviewed-by: brutisso, jmasa
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;
63 class TenuredGeneration;
65 // A generic CMS bit map. It's the basis for both the CMS marking bit map
66 // as well as for the mod union table (in each case only a subset of the
67 // methods are used). This is essentially a wrapper around the BitMap class,
68 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
69 // we have _shifter == 0. and for the mod union table we have
70 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
71 // XXX 64-bit issues in BitMap?
72 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
73 friend class VMStructs;
75 HeapWord* _bmStartWord; // base address of range covered by map
76 size_t _bmWordSize; // map size (in #HeapWords covered)
77 const int _shifter; // shifts to convert HeapWord to bit position
78 VirtualSpace _virtual_space; // underlying the bit map
79 BitMap _bm; // the bit map itself
80 public:
81 Mutex* const _lock; // mutex protecting _bm;
83 public:
84 // constructor
85 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
87 // allocates the actual storage for the map
88 bool allocate(MemRegion mr);
89 // field getter
90 Mutex* lock() const { return _lock; }
91 // locking verifier convenience function
92 void assert_locked() const PRODUCT_RETURN;
94 // inquiries
95 HeapWord* startWord() const { return _bmStartWord; }
96 size_t sizeInWords() const { return _bmWordSize; }
97 size_t sizeInBits() const { return _bm.size(); }
98 // the following is one past the last word in space
99 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
101 // reading marks
102 bool isMarked(HeapWord* addr) const;
103 bool par_isMarked(HeapWord* addr) const; // do not lock checks
104 bool isUnmarked(HeapWord* addr) const;
105 bool isAllClear() const;
107 // writing marks
108 void mark(HeapWord* addr);
109 // For marking by parallel GC threads;
110 // returns true if we did, false if another thread did
111 bool par_mark(HeapWord* addr);
113 void mark_range(MemRegion mr);
114 void par_mark_range(MemRegion mr);
115 void mark_large_range(MemRegion mr);
116 void par_mark_large_range(MemRegion mr);
117 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
118 void clear_range(MemRegion mr);
119 void par_clear_range(MemRegion mr);
120 void clear_large_range(MemRegion mr);
121 void par_clear_large_range(MemRegion mr);
122 void clear_all();
123 void clear_all_incrementally(); // Not yet implemented!!
125 NOT_PRODUCT(
126 // checks the memory region for validity
127 void region_invariant(MemRegion mr);
128 )
130 // iteration
131 void iterate(BitMapClosure* cl) {
132 _bm.iterate(cl);
133 }
134 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
135 void dirty_range_iterate_clear(MemRegionClosure* cl);
136 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
138 // auxiliary support for iteration
139 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
140 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
141 HeapWord* end_addr) const;
142 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
143 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
144 HeapWord* end_addr) const;
145 MemRegion getAndClearMarkedRegion(HeapWord* addr);
146 MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
147 HeapWord* end_addr);
149 // conversion utilities
150 HeapWord* offsetToHeapWord(size_t offset) const;
151 size_t heapWordToOffset(HeapWord* addr) const;
152 size_t heapWordDiffToOffsetDiff(size_t diff) const;
154 void print_on_error(outputStream* st, const char* prefix) const;
156 // debugging
157 // is this address range covered by the bit-map?
158 NOT_PRODUCT(
159 bool covers(MemRegion mr) const;
160 bool covers(HeapWord* start, size_t size = 0) const;
161 )
162 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
163 };
165 // Represents a marking stack used by the CMS collector.
166 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
167 class CMSMarkStack: public CHeapObj<mtGC> {
168 //
169 friend class CMSCollector; // to get at expasion stats further below
170 //
172 VirtualSpace _virtual_space; // space for the stack
173 oop* _base; // bottom of stack
174 size_t _index; // one more than last occupied index
175 size_t _capacity; // max #elements
176 Mutex _par_lock; // an advisory lock used in case of parallel access
177 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run
179 protected:
180 size_t _hit_limit; // we hit max stack size limit
181 size_t _failed_double; // we failed expansion before hitting limit
183 public:
184 CMSMarkStack():
185 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true),
186 _hit_limit(0),
187 _failed_double(0) {}
189 bool allocate(size_t size);
191 size_t capacity() const { return _capacity; }
193 oop pop() {
194 if (!isEmpty()) {
195 return _base[--_index] ;
196 }
197 return NULL;
198 }
200 bool push(oop ptr) {
201 if (isFull()) {
202 return false;
203 } else {
204 _base[_index++] = ptr;
205 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
206 return true;
207 }
208 }
210 bool isEmpty() const { return _index == 0; }
211 bool isFull() const {
212 assert(_index <= _capacity, "buffer overflow");
213 return _index == _capacity;
214 }
216 size_t length() { return _index; }
218 // "Parallel versions" of some of the above
219 oop par_pop() {
220 // lock and pop
221 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
222 return pop();
223 }
225 bool par_push(oop ptr) {
226 // lock and push
227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
228 return push(ptr);
229 }
231 // Forcibly reset the stack, losing all of its contents.
232 void reset() {
233 _index = 0;
234 }
236 // Expand the stack, typically in response to an overflow condition
237 void expand();
239 // Compute the least valued stack element.
240 oop least_value(HeapWord* low) {
241 oop least = (oop)low;
242 for (size_t i = 0; i < _index; i++) {
243 least = MIN2(least, _base[i]);
244 }
245 return least;
246 }
248 // Exposed here to allow stack expansion in || case
249 Mutex* par_lock() { return &_par_lock; }
250 };
252 class CardTableRS;
253 class CMSParGCThreadState;
255 class ModUnionClosure: public MemRegionClosure {
256 protected:
257 CMSBitMap* _t;
258 public:
259 ModUnionClosure(CMSBitMap* t): _t(t) { }
260 void do_MemRegion(MemRegion mr);
261 };
263 class ModUnionClosurePar: public ModUnionClosure {
264 public:
265 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
266 void do_MemRegion(MemRegion mr);
267 };
269 // Survivor Chunk Array in support of parallelization of
270 // Survivor Space rescan.
271 class ChunkArray: public CHeapObj<mtGC> {
272 size_t _index;
273 size_t _capacity;
274 size_t _overflows;
275 HeapWord** _array; // storage for array
277 public:
278 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
279 ChunkArray(HeapWord** a, size_t c):
280 _index(0), _capacity(c), _overflows(0), _array(a) {}
282 HeapWord** array() { return _array; }
283 void set_array(HeapWord** a) { _array = a; }
285 size_t capacity() { return _capacity; }
286 void set_capacity(size_t c) { _capacity = c; }
288 size_t end() {
289 assert(_index <= capacity(),
290 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
291 _index, _capacity));
292 return _index;
293 } // exclusive
295 HeapWord* nth(size_t n) {
296 assert(n < end(), "Out of bounds access");
297 return _array[n];
298 }
300 void reset() {
301 _index = 0;
302 if (_overflows > 0 && PrintCMSStatistics > 1) {
303 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
304 _capacity, _overflows);
305 }
306 _overflows = 0;
307 }
309 void record_sample(HeapWord* p, size_t sz) {
310 // For now we do not do anything with the size
311 if (_index < _capacity) {
312 _array[_index++] = p;
313 } else {
314 ++_overflows;
315 assert(_index == _capacity,
316 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
317 "): out of bounds at overflow#" SIZE_FORMAT,
318 _index, _capacity, _overflows));
319 }
320 }
321 };
323 //
324 // Timing, allocation and promotion statistics for gc scheduling and incremental
325 // mode pacing. Most statistics are exponential averages.
326 //
327 class CMSStats VALUE_OBJ_CLASS_SPEC {
328 private:
329 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
331 // The following are exponential averages with factor alpha:
332 // avg = (100 - alpha) * avg + alpha * cur_sample
333 //
334 // The durations measure: end_time[n] - start_time[n]
335 // The periods measure: start_time[n] - start_time[n-1]
336 //
337 // The cms period and duration include only concurrent collections; time spent
338 // in foreground cms collections due to System.gc() or because of a failure to
339 // keep up are not included.
340 //
341 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
342 // real value, but is used only after the first period. A value of 100 is
343 // used for the first sample so it gets the entire weight.
344 unsigned int _saved_alpha; // 0-100
345 unsigned int _gc0_alpha;
346 unsigned int _cms_alpha;
348 double _gc0_duration;
349 double _gc0_period;
350 size_t _gc0_promoted; // bytes promoted per gc0
351 double _cms_duration;
352 double _cms_duration_pre_sweep; // time from initiation to start of sweep
353 double _cms_duration_per_mb;
354 double _cms_period;
355 size_t _cms_allocated; // bytes of direct allocation per gc0 period
357 // Timers.
358 elapsedTimer _cms_timer;
359 TimeStamp _gc0_begin_time;
360 TimeStamp _cms_begin_time;
361 TimeStamp _cms_end_time;
363 // Snapshots of the amount used in the CMS generation.
364 size_t _cms_used_at_gc0_begin;
365 size_t _cms_used_at_gc0_end;
366 size_t _cms_used_at_cms_begin;
368 // Used to prevent the duty cycle from being reduced in the middle of a cms
369 // cycle.
370 bool _allow_duty_cycle_reduction;
372 enum {
373 _GC0_VALID = 0x1,
374 _CMS_VALID = 0x2,
375 _ALL_VALID = _GC0_VALID | _CMS_VALID
376 };
378 unsigned int _valid_bits;
380 unsigned int _icms_duty_cycle; // icms duty cycle (0-100).
382 protected:
384 // Return a duty cycle that avoids wild oscillations, by limiting the amount
385 // of change between old_duty_cycle and new_duty_cycle (the latter is treated
386 // as a recommended value).
387 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle,
388 unsigned int new_duty_cycle);
389 unsigned int icms_update_duty_cycle_impl();
391 // In support of adjusting of cms trigger ratios based on history
392 // of concurrent mode failure.
393 double cms_free_adjustment_factor(size_t free) const;
394 void adjust_cms_free_adjustment_factor(bool fail, size_t free);
396 public:
397 CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
398 unsigned int alpha = CMSExpAvgFactor);
400 // Whether or not the statistics contain valid data; higher level statistics
401 // cannot be called until this returns true (they require at least one young
402 // gen and one cms cycle to have completed).
403 bool valid() const;
405 // Record statistics.
406 void record_gc0_begin();
407 void record_gc0_end(size_t cms_gen_bytes_used);
408 void record_cms_begin();
409 void record_cms_end();
411 // Allow management of the cms timer, which must be stopped/started around
412 // yield points.
413 elapsedTimer& cms_timer() { return _cms_timer; }
414 void start_cms_timer() { _cms_timer.start(); }
415 void stop_cms_timer() { _cms_timer.stop(); }
417 // Basic statistics; units are seconds or bytes.
418 double gc0_period() const { return _gc0_period; }
419 double gc0_duration() const { return _gc0_duration; }
420 size_t gc0_promoted() const { return _gc0_promoted; }
421 double cms_period() const { return _cms_period; }
422 double cms_duration() const { return _cms_duration; }
423 double cms_duration_per_mb() const { return _cms_duration_per_mb; }
424 size_t cms_allocated() const { return _cms_allocated; }
426 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
428 // Seconds since the last background cms cycle began or ended.
429 double cms_time_since_begin() const;
430 double cms_time_since_end() const;
432 // Higher level statistics--caller must check that valid() returns true before
433 // calling.
435 // Returns bytes promoted per second of wall clock time.
436 double promotion_rate() const;
438 // Returns bytes directly allocated per second of wall clock time.
439 double cms_allocation_rate() const;
441 // Rate at which space in the cms generation is being consumed (sum of the
442 // above two).
443 double cms_consumption_rate() const;
445 // Returns an estimate of the number of seconds until the cms generation will
446 // fill up, assuming no collection work is done.
447 double time_until_cms_gen_full() const;
449 // Returns an estimate of the number of seconds remaining until
450 // the cms generation collection should start.
451 double time_until_cms_start() const;
453 // End of higher level statistics.
455 // Returns the cms incremental mode duty cycle, as a percentage (0-100).
456 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; }
458 // Update the duty cycle and return the new value.
459 unsigned int icms_update_duty_cycle();
461 // Debugging.
462 void print_on(outputStream* st) const PRODUCT_RETURN;
463 void print() const { print_on(gclog_or_tty); }
464 };
466 // A closure related to weak references processing which
467 // we embed in the CMSCollector, since we need to pass
468 // it to the reference processor for secondary filtering
469 // of references based on reachability of referent;
470 // see role of _is_alive_non_header closure in the
471 // ReferenceProcessor class.
472 // For objects in the CMS generation, this closure checks
473 // if the object is "live" (reachable). Used in weak
474 // reference processing.
475 class CMSIsAliveClosure: public BoolObjectClosure {
476 const MemRegion _span;
477 const CMSBitMap* _bit_map;
479 friend class CMSCollector;
480 public:
481 CMSIsAliveClosure(MemRegion span,
482 CMSBitMap* bit_map):
483 _span(span),
484 _bit_map(bit_map) {
485 assert(!span.is_empty(), "Empty span could spell trouble");
486 }
488 void do_object(oop obj) {
489 assert(false, "not to be invoked");
490 }
492 bool do_object_b(oop obj);
493 };
496 // Implements AbstractRefProcTaskExecutor for CMS.
497 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
498 public:
500 CMSRefProcTaskExecutor(CMSCollector& collector)
501 : _collector(collector)
502 { }
504 // Executes a task using worker threads.
505 virtual void execute(ProcessTask& task);
506 virtual void execute(EnqueueTask& task);
507 private:
508 CMSCollector& _collector;
509 };
512 class CMSCollector: public CHeapObj<mtGC> {
513 friend class VMStructs;
514 friend class ConcurrentMarkSweepThread;
515 friend class ConcurrentMarkSweepGeneration;
516 friend class CompactibleFreeListSpace;
517 friend class CMSParRemarkTask;
518 friend class CMSConcMarkingTask;
519 friend class CMSRefProcTaskProxy;
520 friend class CMSRefProcTaskExecutor;
521 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
522 friend class SurvivorSpacePrecleanClosure; // --- ditto -------
523 friend class PushOrMarkClosure; // to access _restart_addr
524 friend class Par_PushOrMarkClosure; // to access _restart_addr
525 friend class MarkFromRootsClosure; // -- ditto --
526 // ... and for clearing cards
527 friend class Par_MarkFromRootsClosure; // to access _restart_addr
528 // ... and for clearing cards
529 friend class Par_ConcMarkingClosure; // to access _restart_addr etc.
530 friend class MarkFromRootsVerifyClosure; // to access _restart_addr
531 friend class PushAndMarkVerifyClosure; // -- ditto --
532 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
533 friend class PushAndMarkClosure; // -- ditto --
534 friend class Par_PushAndMarkClosure; // -- ditto --
535 friend class CMSKeepAliveClosure; // -- ditto --
536 friend class CMSDrainMarkingStackClosure; // -- ditto --
537 friend class CMSInnerParMarkAndPushClosure; // -- ditto --
538 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
539 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
540 friend class VM_CMS_Operation;
541 friend class VM_CMS_Initial_Mark;
542 friend class VM_CMS_Final_Remark;
543 friend class TraceCMSMemoryManagerStats;
545 private:
546 jlong _time_of_last_gc;
547 void update_time_of_last_gc(jlong now) {
548 _time_of_last_gc = now;
549 }
551 OopTaskQueueSet* _task_queues;
553 // Overflow list of grey objects, threaded through mark-word
554 // Manipulated with CAS in the parallel/multi-threaded case.
555 oop _overflow_list;
556 // The following array-pair keeps track of mark words
557 // displaced for accomodating overflow list above.
558 // This code will likely be revisited under RFE#4922830.
559 Stack<oop, mtGC> _preserved_oop_stack;
560 Stack<markOop, mtGC> _preserved_mark_stack;
562 int* _hash_seed;
564 // In support of multi-threaded concurrent phases
565 YieldingFlexibleWorkGang* _conc_workers;
567 // Performance Counters
568 CollectorCounters* _gc_counters;
570 // Initialization Errors
571 bool _completed_initialization;
573 // In support of ExplicitGCInvokesConcurrent
574 static bool _full_gc_requested;
575 unsigned int _collection_count_start;
577 // Should we unload classes this concurrent cycle?
578 bool _should_unload_classes;
579 unsigned int _concurrent_cycles_since_last_unload;
580 unsigned int concurrent_cycles_since_last_unload() const {
581 return _concurrent_cycles_since_last_unload;
582 }
583 // Did we (allow) unload classes in the previous concurrent cycle?
584 bool unloaded_classes_last_cycle() const {
585 return concurrent_cycles_since_last_unload() == 0;
586 }
587 // Root scanning options for perm gen
588 int _roots_scanning_options;
589 int roots_scanning_options() const { return _roots_scanning_options; }
590 void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
591 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
593 // Verification support
594 CMSBitMap _verification_mark_bm;
595 void verify_after_remark_work_1();
596 void verify_after_remark_work_2();
598 // true if any verification flag is on.
599 bool _verifying;
600 bool verifying() const { return _verifying; }
601 void set_verifying(bool v) { _verifying = v; }
603 // Collector policy
604 ConcurrentMarkSweepPolicy* _collector_policy;
605 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
607 // XXX Move these to CMSStats ??? FIX ME !!!
608 elapsedTimer _inter_sweep_timer; // time between sweeps
609 elapsedTimer _intra_sweep_timer; // time _in_ sweeps
610 // padded decaying average estimates of the above
611 AdaptivePaddedAverage _inter_sweep_estimate;
612 AdaptivePaddedAverage _intra_sweep_estimate;
614 protected:
615 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS)
616 MemRegion _span; // span covering above two
617 CardTableRS* _ct; // card table
619 // CMS marking support structures
620 CMSBitMap _markBitMap;
621 CMSBitMap _modUnionTable;
622 CMSMarkStack _markStack;
624 HeapWord* _restart_addr; // in support of marking stack overflow
625 void lower_restart_addr(HeapWord* low);
627 // Counters in support of marking stack / work queue overflow handling:
628 // a non-zero value indicates certain types of overflow events during
629 // the current CMS cycle and could lead to stack resizing efforts at
630 // an opportune future time.
631 size_t _ser_pmc_preclean_ovflw;
632 size_t _ser_pmc_remark_ovflw;
633 size_t _par_pmc_remark_ovflw;
634 size_t _ser_kac_preclean_ovflw;
635 size_t _ser_kac_ovflw;
636 size_t _par_kac_ovflw;
637 NOT_PRODUCT(ssize_t _num_par_pushes;)
639 // ("Weak") Reference processing support
640 ReferenceProcessor* _ref_processor;
641 CMSIsAliveClosure _is_alive_closure;
642 // keep this textually after _markBitMap and _span; c'tor dependency
644 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work
645 ModUnionClosure _modUnionClosure;
646 ModUnionClosurePar _modUnionClosurePar;
648 // CMS abstract state machine
649 // initial_state: Idling
650 // next_state(Idling) = {Marking}
651 // next_state(Marking) = {Precleaning, Sweeping}
652 // next_state(Precleaning) = {AbortablePreclean, FinalMarking}
653 // next_state(AbortablePreclean) = {FinalMarking}
654 // next_state(FinalMarking) = {Sweeping}
655 // next_state(Sweeping) = {Resizing}
656 // next_state(Resizing) = {Resetting}
657 // next_state(Resetting) = {Idling}
658 // The numeric values below are chosen so that:
659 // . _collectorState <= Idling == post-sweep && pre-mark
660 // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
661 // precleaning || abortablePrecleanb
662 public:
663 enum CollectorState {
664 Resizing = 0,
665 Resetting = 1,
666 Idling = 2,
667 InitialMarking = 3,
668 Marking = 4,
669 Precleaning = 5,
670 AbortablePreclean = 6,
671 FinalMarking = 7,
672 Sweeping = 8
673 };
674 protected:
675 static CollectorState _collectorState;
677 // State related to prologue/epilogue invocation for my generations
678 bool _between_prologue_and_epilogue;
680 // Signalling/State related to coordination between fore- and backgroud GC
681 // Note: When the baton has been passed from background GC to foreground GC,
682 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
683 static bool _foregroundGCIsActive; // true iff foreground collector is active or
684 // wants to go active
685 static bool _foregroundGCShouldWait; // true iff background GC is active and has not
686 // yet passed the baton to the foreground GC
688 // Support for CMSScheduleRemark (abortable preclean)
689 bool _abort_preclean;
690 bool _start_sampling;
692 int _numYields;
693 size_t _numDirtyCards;
694 size_t _sweep_count;
695 // number of full gc's since the last concurrent gc.
696 uint _full_gcs_since_conc_gc;
698 // occupancy used for bootstrapping stats
699 double _bootstrap_occupancy;
701 // timer
702 elapsedTimer _timer;
704 // Timing, allocation and promotion statistics, used for scheduling.
705 CMSStats _stats;
707 // Allocation limits installed in the young gen, used only in
708 // CMSIncrementalMode. When an allocation in the young gen would cross one of
709 // these limits, the cms generation is notified and the cms thread is started
710 // or stopped, respectively.
711 HeapWord* _icms_start_limit;
712 HeapWord* _icms_stop_limit;
714 enum CMS_op_type {
715 CMS_op_checkpointRootsInitial,
716 CMS_op_checkpointRootsFinal
717 };
719 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
720 bool stop_world_and_do(CMS_op_type op);
722 OopTaskQueueSet* task_queues() { return _task_queues; }
723 int* hash_seed(int i) { return &_hash_seed[i]; }
724 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
726 // Support for parallelizing Eden rescan in CMS remark phase
727 void sample_eden(); // ... sample Eden space top
729 private:
730 // Support for parallelizing young gen rescan in CMS remark phase
731 Generation* _young_gen; // the younger gen
732 HeapWord** _top_addr; // ... Top of Eden
733 HeapWord** _end_addr; // ... End of Eden
734 HeapWord** _eden_chunk_array; // ... Eden partitioning array
735 size_t _eden_chunk_index; // ... top (exclusive) of array
736 size_t _eden_chunk_capacity; // ... max entries in array
738 // Support for parallelizing survivor space rescan
739 HeapWord** _survivor_chunk_array;
740 size_t _survivor_chunk_index;
741 size_t _survivor_chunk_capacity;
742 size_t* _cursor;
743 ChunkArray* _survivor_plab_array;
745 // Support for marking stack overflow handling
746 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
747 bool par_take_from_overflow_list(size_t num,
748 OopTaskQueue* to_work_q,
749 int no_of_gc_threads);
750 void push_on_overflow_list(oop p);
751 void par_push_on_overflow_list(oop p);
752 // the following is, obviously, not, in general, "MT-stable"
753 bool overflow_list_is_empty() const;
755 void preserve_mark_if_necessary(oop p);
756 void par_preserve_mark_if_necessary(oop p);
757 void preserve_mark_work(oop p, markOop m);
758 void restore_preserved_marks_if_any();
759 NOT_PRODUCT(bool no_preserved_marks() const;)
760 // in support of testing overflow code
761 NOT_PRODUCT(int _overflow_counter;)
762 NOT_PRODUCT(bool simulate_overflow();) // sequential
763 NOT_PRODUCT(bool par_simulate_overflow();) // MT version
765 // CMS work methods
766 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work
768 // a return value of false indicates failure due to stack overflow
769 bool markFromRootsWork(bool asynch); // concurrent marking work
771 public: // FIX ME!!! only for testing
772 bool do_marking_st(bool asynch); // single-threaded marking
773 bool do_marking_mt(bool asynch); // multi-threaded marking
775 private:
777 // concurrent precleaning work
778 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen,
779 ScanMarkedObjectsAgainCarefullyClosure* cl);
780 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen,
781 ScanMarkedObjectsAgainCarefullyClosure* cl);
782 // Does precleaning work, returning a quantity indicative of
783 // the amount of "useful work" done.
784 size_t preclean_work(bool clean_refs, bool clean_survivors);
785 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
786 void abortable_preclean(); // Preclean while looking for possible abort
787 void initialize_sequential_subtasks_for_young_gen_rescan(int i);
788 // Helper function for above; merge-sorts the per-thread plab samples
789 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
790 // Resets (i.e. clears) the per-thread plab sample vectors
791 void reset_survivor_plab_arrays();
793 // final (second) checkpoint work
794 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs,
795 bool init_mark_was_synchronous);
796 // work routine for parallel version of remark
797 void do_remark_parallel();
798 // work routine for non-parallel version of remark
799 void do_remark_non_parallel();
800 // reference processing work routine (during second checkpoint)
801 void refProcessingWork(bool asynch, bool clear_all_soft_refs);
803 // concurrent sweeping work
804 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch);
806 // (concurrent) resetting of support data structures
807 void reset(bool asynch);
809 // Clear _expansion_cause fields of constituent generations
810 void clear_expansion_cause();
812 // An auxilliary method used to record the ends of
813 // used regions of each generation to limit the extent of sweep
814 void save_sweep_limits();
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 // Adjust size of underlying generation
913 void compute_new_size();
915 // GC prologue and epilogue
916 void gc_prologue(bool full);
917 void gc_epilogue(bool full);
919 jlong time_of_last_gc(jlong now) {
920 if (_collectorState <= Idling) {
921 // gc not in progress
922 return _time_of_last_gc;
923 } else {
924 // collection in progress
925 return now;
926 }
927 }
929 // Support for parallel remark of survivor space
930 void* get_data_recorder(int thr_num);
932 CMSBitMap* markBitMap() { return &_markBitMap; }
933 void directAllocated(HeapWord* start, size_t size);
935 // main CMS steps and related support
936 void checkpointRootsInitial(bool asynch);
937 bool markFromRoots(bool asynch); // a return value of false indicates failure
938 // due to stack overflow
939 void preclean();
940 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs,
941 bool init_mark_was_synchronous);
942 void sweep(bool asynch);
944 // Check that the currently executing thread is the expected
945 // one (foreground collector or background collector).
946 static void check_correct_thread_executing() PRODUCT_RETURN;
947 // XXXPERM void print_statistics() PRODUCT_RETURN;
949 bool is_cms_reachable(HeapWord* addr);
951 // Performance Counter Support
952 CollectorCounters* counters() { return _gc_counters; }
954 // timer stuff
955 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
956 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
957 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
958 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
960 int yields() { return _numYields; }
961 void resetYields() { _numYields = 0; }
962 void incrementYields() { _numYields++; }
963 void resetNumDirtyCards() { _numDirtyCards = 0; }
964 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
965 size_t numDirtyCards() { return _numDirtyCards; }
967 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
968 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
969 static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
970 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
971 size_t sweep_count() const { return _sweep_count; }
972 void increment_sweep_count() { _sweep_count++; }
974 // Timers/stats for gc scheduling and incremental mode pacing.
975 CMSStats& stats() { return _stats; }
977 // Convenience methods that check whether CMSIncrementalMode is enabled and
978 // forward to the corresponding methods in ConcurrentMarkSweepThread.
979 static void start_icms();
980 static void stop_icms(); // Called at the end of the cms cycle.
981 static void disable_icms(); // Called before a foreground collection.
982 static void enable_icms(); // Called after a foreground collection.
983 void icms_wait(); // Called at yield points.
985 // Adaptive size policy
986 CMSAdaptiveSizePolicy* size_policy();
987 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
989 static void print_on_error(outputStream* st);
991 // debugging
992 void verify();
993 bool verify_after_remark();
994 void verify_ok_to_terminate() const PRODUCT_RETURN;
995 void verify_work_stacks_empty() const PRODUCT_RETURN;
996 void verify_overflow_empty() const PRODUCT_RETURN;
998 // convenience methods in support of debugging
999 static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
1000 HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
1002 // accessors
1003 CMSMarkStack* verification_mark_stack() { return &_markStack; }
1004 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
1006 // Initialization errors
1007 bool completed_initialization() { return _completed_initialization; }
1008 };
1010 class CMSExpansionCause : public AllStatic {
1011 public:
1012 enum Cause {
1013 _no_expansion,
1014 _satisfy_free_ratio,
1015 _satisfy_promotion,
1016 _satisfy_allocation,
1017 _allocate_par_lab,
1018 _allocate_par_spooling_space,
1019 _adaptive_size_policy
1020 };
1021 // Return a string describing the cause of the expansion.
1022 static const char* to_string(CMSExpansionCause::Cause cause);
1023 };
1025 class ConcurrentMarkSweepGeneration: public CardGeneration {
1026 friend class VMStructs;
1027 friend class ConcurrentMarkSweepThread;
1028 friend class ConcurrentMarkSweep;
1029 friend class CMSCollector;
1030 protected:
1031 static CMSCollector* _collector; // the collector that collects us
1032 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
1034 // Performance Counters
1035 GenerationCounters* _gen_counters;
1036 GSpaceCounters* _space_counters;
1038 // Words directly allocated, used by CMSStats.
1039 size_t _direct_allocated_words;
1041 // Non-product stat counters
1042 NOT_PRODUCT(
1043 size_t _numObjectsPromoted;
1044 size_t _numWordsPromoted;
1045 size_t _numObjectsAllocated;
1046 size_t _numWordsAllocated;
1047 )
1049 // Used for sizing decisions
1050 bool _incremental_collection_failed;
1051 bool incremental_collection_failed() {
1052 return _incremental_collection_failed;
1053 }
1054 void set_incremental_collection_failed() {
1055 _incremental_collection_failed = true;
1056 }
1057 void clear_incremental_collection_failed() {
1058 _incremental_collection_failed = false;
1059 }
1061 // accessors
1062 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1063 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1065 private:
1066 // For parallel young-gen GC support.
1067 CMSParGCThreadState** _par_gc_thread_states;
1069 // Reason generation was expanded
1070 CMSExpansionCause::Cause _expansion_cause;
1072 // In support of MinChunkSize being larger than min object size
1073 const double _dilatation_factor;
1075 enum CollectionTypes {
1076 Concurrent_collection_type = 0,
1077 MS_foreground_collection_type = 1,
1078 MSC_foreground_collection_type = 2,
1079 Unknown_collection_type = 3
1080 };
1082 CollectionTypes _debug_collection_type;
1084 // Fraction of current occupancy at which to start a CMS collection which
1085 // will collect this generation (at least).
1086 double _initiating_occupancy;
1088 protected:
1089 // Shrink generation by specified size (returns false if unable to shrink)
1090 void shrink_free_list_by(size_t bytes);
1092 // Update statistics for GC
1093 virtual void update_gc_stats(int level, bool full);
1095 // Maximum available space in the generation (including uncommitted)
1096 // space.
1097 size_t max_available() const;
1099 // getter and initializer for _initiating_occupancy field.
1100 double initiating_occupancy() const { return _initiating_occupancy; }
1101 void init_initiating_occupancy(intx io, uintx tr);
1103 public:
1104 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1105 int level, CardTableRS* ct,
1106 bool use_adaptive_freelists,
1107 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1109 // Accessors
1110 CMSCollector* collector() const { return _collector; }
1111 static void set_collector(CMSCollector* collector) {
1112 assert(_collector == NULL, "already set");
1113 _collector = collector;
1114 }
1115 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
1117 Mutex* freelistLock() const;
1119 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1121 // Adaptive size policy
1122 CMSAdaptiveSizePolicy* size_policy();
1124 bool refs_discovery_is_atomic() const { return false; }
1125 bool refs_discovery_is_mt() const {
1126 // Note: CMS does MT-discovery during the parallel-remark
1127 // phases. Use ReferenceProcessorMTMutator to make refs
1128 // discovery MT-safe during such phases or other parallel
1129 // discovery phases in the future. This may all go away
1130 // if/when we decide that refs discovery is sufficiently
1131 // rare that the cost of the CAS's involved is in the
1132 // noise. That's a measurement that should be done, and
1133 // the code simplified if that turns out to be the case.
1134 return ConcGCThreads > 1;
1135 }
1137 // Override
1138 virtual void ref_processor_init();
1140 // Grow generation by specified size (returns false if unable to grow)
1141 bool grow_by(size_t bytes);
1142 // Grow generation to reserved size.
1143 bool grow_to_reserved();
1145 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1147 // Space enquiries
1148 size_t capacity() const;
1149 size_t used() const;
1150 size_t free() const;
1151 double occupancy() const { return ((double)used())/((double)capacity()); }
1152 size_t contiguous_available() const;
1153 size_t unsafe_max_alloc_nogc() const;
1155 // over-rides
1156 MemRegion used_region() const;
1157 MemRegion used_region_at_save_marks() const;
1159 // Does a "full" (forced) collection invoked on this generation collect
1160 // all younger generations as well? Note that the second conjunct is a
1161 // hack to allow the collection of the younger gen first if the flag is
1162 // set. This is better than using th policy's should_collect_gen0_first()
1163 // since that causes us to do an extra unnecessary pair of restart-&-stop-world.
1164 virtual bool full_collects_younger_generations() const {
1165 return UseCMSCompactAtFullCollection && !CollectGen0First;
1166 }
1168 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
1170 // Support for compaction
1171 CompactibleSpace* first_compaction_space() const;
1172 // Adjust quantites in the generation affected by
1173 // the compaction.
1174 void reset_after_compaction();
1176 // Allocation support
1177 HeapWord* allocate(size_t size, bool tlab);
1178 HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1179 oop promote(oop obj, size_t obj_size);
1180 HeapWord* par_allocate(size_t size, bool tlab) {
1181 return allocate(size, tlab);
1182 }
1184 // Incremental mode triggering.
1185 HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
1186 size_t word_size);
1188 // Used by CMSStats to track direct allocation. The value is sampled and
1189 // reset after each young gen collection.
1190 size_t direct_allocated_words() const { return _direct_allocated_words; }
1191 void reset_direct_allocated_words() { _direct_allocated_words = 0; }
1193 // Overrides for parallel promotion.
1194 virtual oop par_promote(int thread_num,
1195 oop obj, markOop m, size_t word_sz);
1196 // This one should not be called for CMS.
1197 virtual void par_promote_alloc_undo(int thread_num,
1198 HeapWord* obj, size_t word_sz);
1199 virtual void par_promote_alloc_done(int thread_num);
1200 virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1202 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1204 // Inform this (non-young) generation that a promotion failure was
1205 // encountered during a collection of a younger generation that
1206 // promotes into this generation.
1207 virtual void promotion_failure_occurred();
1209 bool should_collect(bool full, size_t size, bool tlab);
1210 virtual bool should_concurrent_collect() const;
1211 virtual bool is_too_full() const;
1212 void collect(bool full,
1213 bool clear_all_soft_refs,
1214 size_t size,
1215 bool tlab);
1217 HeapWord* expand_and_allocate(size_t word_size,
1218 bool tlab,
1219 bool parallel = false);
1221 // GC prologue and epilogue
1222 void gc_prologue(bool full);
1223 void gc_prologue_work(bool full, bool registerClosure,
1224 ModUnionClosure* modUnionClosure);
1225 void gc_epilogue(bool full);
1226 void gc_epilogue_work(bool full);
1228 // Time since last GC of this generation
1229 jlong time_of_last_gc(jlong now) {
1230 return collector()->time_of_last_gc(now);
1231 }
1232 void update_time_of_last_gc(jlong now) {
1233 collector()-> update_time_of_last_gc(now);
1234 }
1236 // Allocation failure
1237 void expand(size_t bytes, size_t expand_bytes,
1238 CMSExpansionCause::Cause cause);
1239 virtual bool expand(size_t bytes, size_t expand_bytes);
1240 void shrink(size_t bytes);
1241 void shrink_by(size_t bytes);
1242 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1243 bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1245 // Iteration support and related enquiries
1246 void save_marks();
1247 bool no_allocs_since_save_marks();
1248 void object_iterate_since_last_GC(ObjectClosure* cl);
1249 void younger_refs_iterate(OopsInGenClosure* cl);
1251 // Iteration support specific to CMS generations
1252 void save_sweep_limit();
1254 // More iteration support
1255 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1256 virtual void oop_iterate(ExtendedOopClosure* cl);
1257 virtual void safe_object_iterate(ObjectClosure* cl);
1258 virtual void object_iterate(ObjectClosure* cl);
1260 // Need to declare the full complement of closures, whether we'll
1261 // override them or not, or get message from the compiler:
1262 // oop_since_save_marks_iterate_nv hides virtual function...
1263 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1264 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1265 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1267 // Smart allocation XXX -- move to CFLSpace?
1268 void setNearLargestChunk();
1269 bool isNearLargestChunk(HeapWord* addr);
1271 // Get the chunk at the end of the space. Delagates to
1272 // the space.
1273 FreeChunk* find_chunk_at_end();
1275 void post_compact();
1277 // Debugging
1278 void prepare_for_verify();
1279 void verify();
1280 void print_statistics() PRODUCT_RETURN;
1282 // Performance Counters support
1283 virtual void update_counters();
1284 virtual void update_counters(size_t used);
1285 void initialize_performance_counters();
1286 CollectorCounters* counters() { return collector()->counters(); }
1288 // Support for parallel remark of survivor space
1289 void* get_data_recorder(int thr_num) {
1290 //Delegate to collector
1291 return collector()->get_data_recorder(thr_num);
1292 }
1294 // Printing
1295 const char* name() const;
1296 virtual const char* short_name() const { return "CMS"; }
1297 void print() const;
1298 void printOccupancy(const char* s);
1299 bool must_be_youngest() const { return false; }
1300 bool must_be_oldest() const { return true; }
1302 // Resize the generation after a compacting GC. The
1303 // generation can be treated as a contiguous space
1304 // after the compaction.
1305 virtual void compute_new_size();
1306 // Resize the generation after a non-compacting
1307 // collection.
1308 void compute_new_size_free_list();
1310 CollectionTypes debug_collection_type() { return _debug_collection_type; }
1311 void rotate_debug_collection_type();
1312 };
1314 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration {
1316 // Return the size policy from the heap's collector
1317 // policy casted to CMSAdaptiveSizePolicy*.
1318 CMSAdaptiveSizePolicy* cms_size_policy() const;
1320 // Resize the generation based on the adaptive size
1321 // policy.
1322 void resize(size_t cur_promo, size_t desired_promo);
1324 // Return the GC counters from the collector policy
1325 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters();
1327 virtual void shrink_by(size_t bytes);
1329 public:
1330 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1331 int level, CardTableRS* ct,
1332 bool use_adaptive_freelists,
1333 FreeBlockDictionary<FreeChunk>::DictionaryChoice
1334 dictionaryChoice) :
1335 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct,
1336 use_adaptive_freelists, dictionaryChoice) {}
1338 virtual const char* short_name() const { return "ASCMS"; }
1339 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; }
1341 virtual void update_counters();
1342 virtual void update_counters(size_t used);
1343 };
1345 //
1346 // Closures of various sorts used by CMS to accomplish its work
1347 //
1349 // This closure is used to check that a certain set of oops is empty.
1350 class FalseClosure: public OopClosure {
1351 public:
1352 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); }
1353 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); }
1354 };
1356 // This closure is used to do concurrent marking from the roots
1357 // following the first checkpoint.
1358 class MarkFromRootsClosure: public BitMapClosure {
1359 CMSCollector* _collector;
1360 MemRegion _span;
1361 CMSBitMap* _bitMap;
1362 CMSBitMap* _mut;
1363 CMSMarkStack* _markStack;
1364 bool _yield;
1365 int _skipBits;
1366 HeapWord* _finger;
1367 HeapWord* _threshold;
1368 DEBUG_ONLY(bool _verifying;)
1370 public:
1371 MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1372 CMSBitMap* bitMap,
1373 CMSMarkStack* markStack,
1374 bool should_yield, bool verifying = false);
1375 bool do_bit(size_t offset);
1376 void reset(HeapWord* addr);
1377 inline void do_yield_check();
1379 private:
1380 void scanOopsInOop(HeapWord* ptr);
1381 void do_yield_work();
1382 };
1384 // This closure is used to do concurrent multi-threaded
1385 // marking from the roots following the first checkpoint.
1386 // XXX This should really be a subclass of The serial version
1387 // above, but i have not had the time to refactor things cleanly.
1388 // That willbe done for Dolphin.
1389 class Par_MarkFromRootsClosure: public BitMapClosure {
1390 CMSCollector* _collector;
1391 MemRegion _whole_span;
1392 MemRegion _span;
1393 CMSBitMap* _bit_map;
1394 CMSBitMap* _mut;
1395 OopTaskQueue* _work_queue;
1396 CMSMarkStack* _overflow_stack;
1397 bool _yield;
1398 int _skip_bits;
1399 HeapWord* _finger;
1400 HeapWord* _threshold;
1401 CMSConcMarkingTask* _task;
1402 public:
1403 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1404 MemRegion span,
1405 CMSBitMap* bit_map,
1406 OopTaskQueue* work_queue,
1407 CMSMarkStack* overflow_stack,
1408 bool should_yield);
1409 bool do_bit(size_t offset);
1410 inline void do_yield_check();
1412 private:
1413 void scan_oops_in_oop(HeapWord* ptr);
1414 void do_yield_work();
1415 bool get_work_from_overflow_stack();
1416 };
1418 // The following closures are used to do certain kinds of verification of
1419 // CMS marking.
1420 class PushAndMarkVerifyClosure: public CMSOopClosure {
1421 CMSCollector* _collector;
1422 MemRegion _span;
1423 CMSBitMap* _verification_bm;
1424 CMSBitMap* _cms_bm;
1425 CMSMarkStack* _mark_stack;
1426 protected:
1427 void do_oop(oop p);
1428 template <class T> inline void do_oop_work(T *p) {
1429 oop obj = oopDesc::load_decode_heap_oop(p);
1430 do_oop(obj);
1431 }
1432 public:
1433 PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1434 MemRegion span,
1435 CMSBitMap* verification_bm,
1436 CMSBitMap* cms_bm,
1437 CMSMarkStack* mark_stack);
1438 void do_oop(oop* p);
1439 void do_oop(narrowOop* p);
1441 // Deal with a stack overflow condition
1442 void handle_stack_overflow(HeapWord* lost);
1443 };
1445 class MarkFromRootsVerifyClosure: public BitMapClosure {
1446 CMSCollector* _collector;
1447 MemRegion _span;
1448 CMSBitMap* _verification_bm;
1449 CMSBitMap* _cms_bm;
1450 CMSMarkStack* _mark_stack;
1451 HeapWord* _finger;
1452 PushAndMarkVerifyClosure _pam_verify_closure;
1453 public:
1454 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1455 CMSBitMap* verification_bm,
1456 CMSBitMap* cms_bm,
1457 CMSMarkStack* mark_stack);
1458 bool do_bit(size_t offset);
1459 void reset(HeapWord* addr);
1460 };
1463 // This closure is used to check that a certain set of bits is
1464 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1465 class FalseBitMapClosure: public BitMapClosure {
1466 public:
1467 bool do_bit(size_t offset) {
1468 guarantee(false, "Should not have a 1 bit");
1469 return true;
1470 }
1471 };
1473 // This closure is used during the second checkpointing phase
1474 // to rescan the marked objects on the dirty cards in the mod
1475 // union table and the card table proper. It's invoked via
1476 // MarkFromDirtyCardsClosure below. It uses either
1477 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1478 // declared in genOopClosures.hpp to accomplish some of its work.
1479 // In the parallel case the bitMap is shared, so access to
1480 // it needs to be suitably synchronized for updates by embedded
1481 // closures that update it; however, this closure itself only
1482 // reads the bit_map and because it is idempotent, is immune to
1483 // reading stale values.
1484 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1485 #ifdef ASSERT
1486 CMSCollector* _collector;
1487 MemRegion _span;
1488 union {
1489 CMSMarkStack* _mark_stack;
1490 OopTaskQueue* _work_queue;
1491 };
1492 #endif // ASSERT
1493 bool _parallel;
1494 CMSBitMap* _bit_map;
1495 union {
1496 MarkRefsIntoAndScanClosure* _scan_closure;
1497 Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1498 };
1500 public:
1501 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1502 MemRegion span,
1503 ReferenceProcessor* rp,
1504 CMSBitMap* bit_map,
1505 CMSMarkStack* mark_stack,
1506 MarkRefsIntoAndScanClosure* cl):
1507 #ifdef ASSERT
1508 _collector(collector),
1509 _span(span),
1510 _mark_stack(mark_stack),
1511 #endif // ASSERT
1512 _parallel(false),
1513 _bit_map(bit_map),
1514 _scan_closure(cl) { }
1516 ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1517 MemRegion span,
1518 ReferenceProcessor* rp,
1519 CMSBitMap* bit_map,
1520 OopTaskQueue* work_queue,
1521 Par_MarkRefsIntoAndScanClosure* cl):
1522 #ifdef ASSERT
1523 _collector(collector),
1524 _span(span),
1525 _work_queue(work_queue),
1526 #endif // ASSERT
1527 _parallel(true),
1528 _bit_map(bit_map),
1529 _par_scan_closure(cl) { }
1531 void do_object(oop obj) {
1532 guarantee(false, "Call do_object_b(oop, MemRegion) instead");
1533 }
1534 bool do_object_b(oop obj) {
1535 guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1536 return false;
1537 }
1538 bool do_object_bm(oop p, MemRegion mr);
1539 };
1541 // This closure is used during the second checkpointing phase
1542 // to rescan the marked objects on the dirty cards in the mod
1543 // union table and the card table proper. It invokes
1544 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1545 // In the parallel case, the bit map is shared and requires
1546 // synchronized access.
1547 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1548 CompactibleFreeListSpace* _space;
1549 ScanMarkedObjectsAgainClosure _scan_cl;
1550 size_t _num_dirty_cards;
1552 public:
1553 MarkFromDirtyCardsClosure(CMSCollector* collector,
1554 MemRegion span,
1555 CompactibleFreeListSpace* space,
1556 CMSBitMap* bit_map,
1557 CMSMarkStack* mark_stack,
1558 MarkRefsIntoAndScanClosure* cl):
1559 _space(space),
1560 _num_dirty_cards(0),
1561 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1562 mark_stack, cl) { }
1564 MarkFromDirtyCardsClosure(CMSCollector* collector,
1565 MemRegion span,
1566 CompactibleFreeListSpace* space,
1567 CMSBitMap* bit_map,
1568 OopTaskQueue* work_queue,
1569 Par_MarkRefsIntoAndScanClosure* cl):
1570 _space(space),
1571 _num_dirty_cards(0),
1572 _scan_cl(collector, span, collector->ref_processor(), bit_map,
1573 work_queue, cl) { }
1575 void do_MemRegion(MemRegion mr);
1576 void set_space(CompactibleFreeListSpace* space) { _space = space; }
1577 size_t num_dirty_cards() { return _num_dirty_cards; }
1578 };
1580 // This closure is used in the non-product build to check
1581 // that there are no MemRegions with a certain property.
1582 class FalseMemRegionClosure: public MemRegionClosure {
1583 void do_MemRegion(MemRegion mr) {
1584 guarantee(!mr.is_empty(), "Shouldn't be empty");
1585 guarantee(false, "Should never be here");
1586 }
1587 };
1589 // This closure is used during the precleaning phase
1590 // to "carefully" rescan marked objects on dirty cards.
1591 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1592 // to accomplish some of its work.
1593 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1594 CMSCollector* _collector;
1595 MemRegion _span;
1596 bool _yield;
1597 Mutex* _freelistLock;
1598 CMSBitMap* _bitMap;
1599 CMSMarkStack* _markStack;
1600 MarkRefsIntoAndScanClosure* _scanningClosure;
1602 public:
1603 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1604 MemRegion span,
1605 CMSBitMap* bitMap,
1606 CMSMarkStack* markStack,
1607 MarkRefsIntoAndScanClosure* cl,
1608 bool should_yield):
1609 _collector(collector),
1610 _span(span),
1611 _yield(should_yield),
1612 _bitMap(bitMap),
1613 _markStack(markStack),
1614 _scanningClosure(cl) {
1615 }
1617 void do_object(oop p) {
1618 guarantee(false, "call do_object_careful instead");
1619 }
1621 size_t do_object_careful(oop p) {
1622 guarantee(false, "Unexpected caller");
1623 return 0;
1624 }
1626 size_t do_object_careful_m(oop p, MemRegion mr);
1628 void setFreelistLock(Mutex* m) {
1629 _freelistLock = m;
1630 _scanningClosure->set_freelistLock(m);
1631 }
1633 private:
1634 inline bool do_yield_check();
1636 void do_yield_work();
1637 };
1639 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1640 CMSCollector* _collector;
1641 MemRegion _span;
1642 bool _yield;
1643 CMSBitMap* _bit_map;
1644 CMSMarkStack* _mark_stack;
1645 PushAndMarkClosure* _scanning_closure;
1646 unsigned int _before_count;
1648 public:
1649 SurvivorSpacePrecleanClosure(CMSCollector* collector,
1650 MemRegion span,
1651 CMSBitMap* bit_map,
1652 CMSMarkStack* mark_stack,
1653 PushAndMarkClosure* cl,
1654 unsigned int before_count,
1655 bool should_yield):
1656 _collector(collector),
1657 _span(span),
1658 _yield(should_yield),
1659 _bit_map(bit_map),
1660 _mark_stack(mark_stack),
1661 _scanning_closure(cl),
1662 _before_count(before_count)
1663 { }
1665 void do_object(oop p) {
1666 guarantee(false, "call do_object_careful instead");
1667 }
1669 size_t do_object_careful(oop p);
1671 size_t do_object_careful_m(oop p, MemRegion mr) {
1672 guarantee(false, "Unexpected caller");
1673 return 0;
1674 }
1676 private:
1677 inline void do_yield_check();
1678 void do_yield_work();
1679 };
1681 // This closure is used to accomplish the sweeping work
1682 // after the second checkpoint but before the concurrent reset
1683 // phase.
1684 //
1685 // Terminology
1686 // left hand chunk (LHC) - block of one or more chunks currently being
1687 // coalesced. The LHC is available for coalescing with a new chunk.
1688 // right hand chunk (RHC) - block that is currently being swept that is
1689 // free or garbage that can be coalesced with the LHC.
1690 // _inFreeRange is true if there is currently a LHC
1691 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1692 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1693 // _freeFinger is the address of the current LHC
1694 class SweepClosure: public BlkClosureCareful {
1695 CMSCollector* _collector; // collector doing the work
1696 ConcurrentMarkSweepGeneration* _g; // Generation being swept
1697 CompactibleFreeListSpace* _sp; // Space being swept
1698 HeapWord* _limit;// the address at or above which the sweep should stop
1699 // because we do not expect newly garbage blocks
1700 // eligible for sweeping past that address.
1701 Mutex* _freelistLock; // Free list lock (in space)
1702 CMSBitMap* _bitMap; // Marking bit map (in
1703 // generation)
1704 bool _inFreeRange; // Indicates if we are in the
1705 // midst of a free run
1706 bool _freeRangeInFreeLists;
1707 // Often, we have just found
1708 // a free chunk and started
1709 // a new free range; we do not
1710 // eagerly remove this chunk from
1711 // the free lists unless there is
1712 // a possibility of coalescing.
1713 // When true, this flag indicates
1714 // that the _freeFinger below
1715 // points to a potentially free chunk
1716 // that may still be in the free lists
1717 bool _lastFreeRangeCoalesced;
1718 // free range contains chunks
1719 // coalesced
1720 bool _yield;
1721 // Whether sweeping should be
1722 // done with yields. For instance
1723 // when done by the foreground
1724 // collector we shouldn't yield.
1725 HeapWord* _freeFinger; // When _inFreeRange is set, the
1726 // pointer to the "left hand
1727 // chunk"
1728 size_t _freeRangeSize;
1729 // When _inFreeRange is set, this
1730 // indicates the accumulated size
1731 // of the "left hand chunk"
1732 NOT_PRODUCT(
1733 size_t _numObjectsFreed;
1734 size_t _numWordsFreed;
1735 size_t _numObjectsLive;
1736 size_t _numWordsLive;
1737 size_t _numObjectsAlreadyFree;
1738 size_t _numWordsAlreadyFree;
1739 FreeChunk* _last_fc;
1740 )
1741 private:
1742 // Code that is common to a free chunk or garbage when
1743 // encountered during sweeping.
1744 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1745 // Process a free chunk during sweeping.
1746 void do_already_free_chunk(FreeChunk *fc);
1747 // Work method called when processing an already free or a
1748 // freshly garbage chunk to do a lookahead and possibly a
1749 // premptive flush if crossing over _limit.
1750 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1751 // Process a garbage chunk during sweeping.
1752 size_t do_garbage_chunk(FreeChunk *fc);
1753 // Process a live chunk during sweeping.
1754 size_t do_live_chunk(FreeChunk* fc);
1756 // Accessors.
1757 HeapWord* freeFinger() const { return _freeFinger; }
1758 void set_freeFinger(HeapWord* v) { _freeFinger = v; }
1759 bool inFreeRange() const { return _inFreeRange; }
1760 void set_inFreeRange(bool v) { _inFreeRange = v; }
1761 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
1762 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1763 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
1764 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1766 // Initialize a free range.
1767 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1768 // Return this chunk to the free lists.
1769 void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1771 // Check if we should yield and do so when necessary.
1772 inline void do_yield_check(HeapWord* addr);
1774 // Yield
1775 void do_yield_work(HeapWord* addr);
1777 // Debugging/Printing
1778 void print_free_block_coalesced(FreeChunk* fc) const;
1780 public:
1781 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1782 CMSBitMap* bitMap, bool should_yield);
1783 ~SweepClosure() PRODUCT_RETURN;
1785 size_t do_blk_careful(HeapWord* addr);
1786 void print() const { print_on(tty); }
1787 void print_on(outputStream *st) const;
1788 };
1790 // Closures related to weak references processing
1792 // During CMS' weak reference processing, this is a
1793 // work-routine/closure used to complete transitive
1794 // marking of objects as live after a certain point
1795 // in which an initial set has been completely accumulated.
1796 // This closure is currently used both during the final
1797 // remark stop-world phase, as well as during the concurrent
1798 // precleaning of the discovered reference lists.
1799 class CMSDrainMarkingStackClosure: public VoidClosure {
1800 CMSCollector* _collector;
1801 MemRegion _span;
1802 CMSMarkStack* _mark_stack;
1803 CMSBitMap* _bit_map;
1804 CMSKeepAliveClosure* _keep_alive;
1805 bool _concurrent_precleaning;
1806 public:
1807 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1808 CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1809 CMSKeepAliveClosure* keep_alive,
1810 bool cpc):
1811 _collector(collector),
1812 _span(span),
1813 _bit_map(bit_map),
1814 _mark_stack(mark_stack),
1815 _keep_alive(keep_alive),
1816 _concurrent_precleaning(cpc) {
1817 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1818 "Mismatch");
1819 }
1821 void do_void();
1822 };
1824 // A parallel version of CMSDrainMarkingStackClosure above.
1825 class CMSParDrainMarkingStackClosure: public VoidClosure {
1826 CMSCollector* _collector;
1827 MemRegion _span;
1828 OopTaskQueue* _work_queue;
1829 CMSBitMap* _bit_map;
1830 CMSInnerParMarkAndPushClosure _mark_and_push;
1832 public:
1833 CMSParDrainMarkingStackClosure(CMSCollector* collector,
1834 MemRegion span, CMSBitMap* bit_map,
1835 OopTaskQueue* work_queue):
1836 _collector(collector),
1837 _span(span),
1838 _bit_map(bit_map),
1839 _work_queue(work_queue),
1840 _mark_and_push(collector, span, bit_map, work_queue) { }
1842 public:
1843 void trim_queue(uint max);
1844 void do_void();
1845 };
1847 // Allow yielding or short-circuiting of reference list
1848 // prelceaning work.
1849 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1850 CMSCollector* _collector;
1851 void do_yield_work();
1852 public:
1853 CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1854 _collector(collector) {}
1855 virtual bool should_return();
1856 };
1859 // Convenience class that locks free list locks for given CMS collector
1860 class FreelistLocker: public StackObj {
1861 private:
1862 CMSCollector* _collector;
1863 public:
1864 FreelistLocker(CMSCollector* collector):
1865 _collector(collector) {
1866 _collector->getFreelistLocks();
1867 }
1869 ~FreelistLocker() {
1870 _collector->releaseFreelistLocks();
1871 }
1872 };
1874 // Mark all dead objects in a given space.
1875 class MarkDeadObjectsClosure: public BlkClosure {
1876 const CMSCollector* _collector;
1877 const CompactibleFreeListSpace* _sp;
1878 CMSBitMap* _live_bit_map;
1879 CMSBitMap* _dead_bit_map;
1880 public:
1881 MarkDeadObjectsClosure(const CMSCollector* collector,
1882 const CompactibleFreeListSpace* sp,
1883 CMSBitMap *live_bit_map,
1884 CMSBitMap *dead_bit_map) :
1885 _collector(collector),
1886 _sp(sp),
1887 _live_bit_map(live_bit_map),
1888 _dead_bit_map(dead_bit_map) {}
1889 size_t do_blk(HeapWord* addr);
1890 };
1892 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1894 public:
1895 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1896 };
1899 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP