1 /* 2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP 27 28 #include "gc_implementation/shared/gcHeapSummary.hpp" 29 #include "gc_implementation/shared/gSpaceCounters.hpp" 30 #include "gc_implementation/shared/gcStats.hpp" 31 #include "gc_implementation/shared/gcWhen.hpp" 32 #include "gc_implementation/shared/generationCounters.hpp" 33 #include "memory/freeBlockDictionary.hpp" 34 #include "memory/generation.hpp" 35 #include "memory/iterator.hpp" 36 #include "runtime/mutexLocker.hpp" 37 #include "runtime/virtualspace.hpp" 38 #include "services/memoryService.hpp" 39 #include "utilities/bitMap.inline.hpp" 40 #include "utilities/stack.inline.hpp" 41 #include "utilities/taskqueue.hpp" 42 #include "utilities/yieldingWorkgroup.hpp" 43 44 // ConcurrentMarkSweepGeneration is in support of a concurrent 45 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker 46 // style. We assume, for now, that this generation is always the 47 // seniormost generation and for simplicity 48 // in the first implementation, that this generation is a single compactible 49 // space. Neither of these restrictions appears essential, and will be 50 // relaxed in the future when more time is available to implement the 51 // greater generality (and there's a need for it). 52 // 53 // Concurrent mode failures are currently handled by 54 // means of a sliding mark-compact. 55 56 class AdaptiveSizePolicy; 57 class CMSConcMarkingTask; 58 class CMSGCAdaptivePolicyCounters; 59 class CMSTracer; 60 class ConcurrentGCTimer; 61 class ConcurrentMarkSweepGeneration; 62 class ConcurrentMarkSweepPolicy; 63 class ConcurrentMarkSweepThread; 64 class CompactibleFreeListSpace; 65 class FreeChunk; 66 class PromotionInfo; 67 class ScanMarkedObjectsAgainCarefullyClosure; 68 class TenuredGeneration; 69 class SerialOldTracer; 70 71 // A generic CMS bit map. It's the basis for both the CMS marking bit map 72 // as well as for the mod union table (in each case only a subset of the 73 // methods are used). This is essentially a wrapper around the BitMap class, 74 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 75 // we have _shifter == 0. and for the mod union table we have 76 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 77 // XXX 64-bit issues in BitMap? 78 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 79 friend class VMStructs; 80 81 HeapWord* _bmStartWord; // base address of range covered by map 82 size_t _bmWordSize; // map size (in #HeapWords covered) 83 const int _shifter; // shifts to convert HeapWord to bit position 84 VirtualSpace _virtual_space; // underlying the bit map 85 BitMap _bm; // the bit map itself 86 public: 87 Mutex* const _lock; // mutex protecting _bm; 88 89 public: 90 // constructor 91 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 92 93 // allocates the actual storage for the map 94 bool allocate(MemRegion mr); 95 // field getter 96 Mutex* lock() const { return _lock; } 97 // locking verifier convenience function 98 void assert_locked() const PRODUCT_RETURN; 99 100 // inquiries 101 HeapWord* startWord() const { return _bmStartWord; } 102 size_t sizeInWords() const { return _bmWordSize; } 103 size_t sizeInBits() const { return _bm.size(); } 104 // the following is one past the last word in space 105 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 106 107 // reading marks 108 bool isMarked(HeapWord* addr) const; 109 bool par_isMarked(HeapWord* addr) const; // do not lock checks 110 bool isUnmarked(HeapWord* addr) const; 111 bool isAllClear() const; 112 113 // writing marks 114 void mark(HeapWord* addr); 115 // For marking by parallel GC threads; 116 // returns true if we did, false if another thread did 117 bool par_mark(HeapWord* addr); 118 119 void mark_range(MemRegion mr); 120 void par_mark_range(MemRegion mr); 121 void mark_large_range(MemRegion mr); 122 void par_mark_large_range(MemRegion mr); 123 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 124 void clear_range(MemRegion mr); 125 void par_clear_range(MemRegion mr); 126 void clear_large_range(MemRegion mr); 127 void par_clear_large_range(MemRegion mr); 128 void clear_all(); 129 void clear_all_incrementally(); // Not yet implemented!! 130 131 NOT_PRODUCT( 132 // checks the memory region for validity 133 void region_invariant(MemRegion mr); 134 ) 135 136 // iteration 137 void iterate(BitMapClosure* cl) { 138 _bm.iterate(cl); 139 } 140 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 141 void dirty_range_iterate_clear(MemRegionClosure* cl); 142 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 143 144 // auxiliary support for iteration 145 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 146 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 147 HeapWord* end_addr) const; 148 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 149 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 150 HeapWord* end_addr) const; 151 MemRegion getAndClearMarkedRegion(HeapWord* addr); 152 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 153 HeapWord* end_addr); 154 155 // conversion utilities 156 HeapWord* offsetToHeapWord(size_t offset) const; 157 size_t heapWordToOffset(HeapWord* addr) const; 158 size_t heapWordDiffToOffsetDiff(size_t diff) const; 159 160 void print_on_error(outputStream* st, const char* prefix) const; 161 162 // debugging 163 // is this address range covered by the bit-map? 164 NOT_PRODUCT( 165 bool covers(MemRegion mr) const; 166 bool covers(HeapWord* start, size_t size = 0) const; 167 ) 168 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 169 }; 170 171 // Represents a marking stack used by the CMS collector. 172 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 173 class CMSMarkStack: public CHeapObj<mtGC> { 174 // 175 friend class CMSCollector; // To get at expansion stats further below. 176 // 177 178 VirtualSpace _virtual_space; // Space for the stack 179 oop* _base; // Bottom of stack 180 size_t _index; // One more than last occupied index 181 size_t _capacity; // Max #elements 182 Mutex _par_lock; // An advisory lock used in case of parallel access 183 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run 184 185 protected: 186 size_t _hit_limit; // We hit max stack size limit 187 size_t _failed_double; // We failed expansion before hitting limit 188 189 public: 190 CMSMarkStack(): 191 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true), 192 _hit_limit(0), 193 _failed_double(0) {} 194 195 bool allocate(size_t size); 196 197 size_t capacity() const { return _capacity; } 198 199 oop pop() { 200 if (!isEmpty()) { 201 return _base[--_index] ; 202 } 203 return NULL; 204 } 205 206 bool push(oop ptr) { 207 if (isFull()) { 208 return false; 209 } else { 210 _base[_index++] = ptr; 211 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 212 return true; 213 } 214 } 215 216 bool isEmpty() const { return _index == 0; } 217 bool isFull() const { 218 assert(_index <= _capacity, "buffer overflow"); 219 return _index == _capacity; 220 } 221 222 size_t length() { return _index; } 223 224 // "Parallel versions" of some of the above 225 oop par_pop() { 226 // lock and pop 227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 228 return pop(); 229 } 230 231 bool par_push(oop ptr) { 232 // lock and push 233 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 234 return push(ptr); 235 } 236 237 // Forcibly reset the stack, losing all of its contents. 238 void reset() { 239 _index = 0; 240 } 241 242 // Expand the stack, typically in response to an overflow condition. 243 void expand(); 244 245 // Compute the least valued stack element. 246 oop least_value(HeapWord* low) { 247 oop least = (oop)low; 248 for (size_t i = 0; i < _index; i++) { 249 least = MIN2(least, _base[i]); 250 } 251 return least; 252 } 253 254 // Exposed here to allow stack expansion in || case. 255 Mutex* par_lock() { return &_par_lock; } 256 }; 257 258 class CardTableRS; 259 class CMSParGCThreadState; 260 261 class ModUnionClosure: public MemRegionClosure { 262 protected: 263 CMSBitMap* _t; 264 public: 265 ModUnionClosure(CMSBitMap* t): _t(t) { } 266 void do_MemRegion(MemRegion mr); 267 }; 268 269 class ModUnionClosurePar: public ModUnionClosure { 270 public: 271 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 272 void do_MemRegion(MemRegion mr); 273 }; 274 275 // Survivor Chunk Array in support of parallelization of 276 // Survivor Space rescan. 277 class ChunkArray: public CHeapObj<mtGC> { 278 size_t _index; 279 size_t _capacity; 280 size_t _overflows; 281 HeapWord** _array; // storage for array 282 283 public: 284 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 285 ChunkArray(HeapWord** a, size_t c): 286 _index(0), _capacity(c), _overflows(0), _array(a) {} 287 288 HeapWord** array() { return _array; } 289 void set_array(HeapWord** a) { _array = a; } 290 291 size_t capacity() { return _capacity; } 292 void set_capacity(size_t c) { _capacity = c; } 293 294 size_t end() { 295 assert(_index <= capacity(), 296 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 297 _index, _capacity)); 298 return _index; 299 } // exclusive 300 301 HeapWord* nth(size_t n) { 302 assert(n < end(), "Out of bounds access"); 303 return _array[n]; 304 } 305 306 void reset() { 307 _index = 0; 308 if (_overflows > 0 && PrintCMSStatistics > 1) { 309 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", 310 _capacity, _overflows); 311 } 312 _overflows = 0; 313 } 314 315 void record_sample(HeapWord* p, size_t sz) { 316 // For now we do not do anything with the size 317 if (_index < _capacity) { 318 _array[_index++] = p; 319 } else { 320 ++_overflows; 321 assert(_index == _capacity, 322 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 323 "): out of bounds at overflow#" SIZE_FORMAT, 324 _index, _capacity, _overflows)); 325 } 326 } 327 }; 328 329 // 330 // Timing, allocation and promotion statistics for gc scheduling and incremental 331 // mode pacing. Most statistics are exponential averages. 332 // 333 class CMSStats VALUE_OBJ_CLASS_SPEC { 334 private: 335 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 336 337 // The following are exponential averages with factor alpha: 338 // avg = (100 - alpha) * avg + alpha * cur_sample 339 // 340 // The durations measure: end_time[n] - start_time[n] 341 // The periods measure: start_time[n] - start_time[n-1] 342 // 343 // The cms period and duration include only concurrent collections; time spent 344 // in foreground cms collections due to System.gc() or because of a failure to 345 // keep up are not included. 346 // 347 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 348 // real value, but is used only after the first period. A value of 100 is 349 // used for the first sample so it gets the entire weight. 350 unsigned int _saved_alpha; // 0-100 351 unsigned int _gc0_alpha; 352 unsigned int _cms_alpha; 353 354 double _gc0_duration; 355 double _gc0_period; 356 size_t _gc0_promoted; // bytes promoted per gc0 357 double _cms_duration; 358 double _cms_duration_pre_sweep; // time from initiation to start of sweep 359 double _cms_duration_per_mb; 360 double _cms_period; 361 size_t _cms_allocated; // bytes of direct allocation per gc0 period 362 363 // Timers. 364 elapsedTimer _cms_timer; 365 TimeStamp _gc0_begin_time; 366 TimeStamp _cms_begin_time; 367 TimeStamp _cms_end_time; 368 369 // Snapshots of the amount used in the CMS generation. 370 size_t _cms_used_at_gc0_begin; 371 size_t _cms_used_at_gc0_end; 372 size_t _cms_used_at_cms_begin; 373 374 // Used to prevent the duty cycle from being reduced in the middle of a cms 375 // cycle. 376 bool _allow_duty_cycle_reduction; 377 378 enum { 379 _GC0_VALID = 0x1, 380 _CMS_VALID = 0x2, 381 _ALL_VALID = _GC0_VALID | _CMS_VALID 382 }; 383 384 unsigned int _valid_bits; 385 386 unsigned int _icms_duty_cycle; // icms duty cycle (0-100). 387 388 protected: 389 390 // Return a duty cycle that avoids wild oscillations, by limiting the amount 391 // of change between old_duty_cycle and new_duty_cycle (the latter is treated 392 // as a recommended value). 393 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle, 394 unsigned int new_duty_cycle); 395 unsigned int icms_update_duty_cycle_impl(); 396 397 // In support of adjusting of cms trigger ratios based on history 398 // of concurrent mode failure. 399 double cms_free_adjustment_factor(size_t free) const; 400 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 401 402 public: 403 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 404 unsigned int alpha = CMSExpAvgFactor); 405 406 // Whether or not the statistics contain valid data; higher level statistics 407 // cannot be called until this returns true (they require at least one young 408 // gen and one cms cycle to have completed). 409 bool valid() const; 410 411 // Record statistics. 412 void record_gc0_begin(); 413 void record_gc0_end(size_t cms_gen_bytes_used); 414 void record_cms_begin(); 415 void record_cms_end(); 416 417 // Allow management of the cms timer, which must be stopped/started around 418 // yield points. 419 elapsedTimer& cms_timer() { return _cms_timer; } 420 void start_cms_timer() { _cms_timer.start(); } 421 void stop_cms_timer() { _cms_timer.stop(); } 422 423 // Basic statistics; units are seconds or bytes. 424 double gc0_period() const { return _gc0_period; } 425 double gc0_duration() const { return _gc0_duration; } 426 size_t gc0_promoted() const { return _gc0_promoted; } 427 double cms_period() const { return _cms_period; } 428 double cms_duration() const { return _cms_duration; } 429 double cms_duration_per_mb() const { return _cms_duration_per_mb; } 430 size_t cms_allocated() const { return _cms_allocated; } 431 432 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 433 434 // Seconds since the last background cms cycle began or ended. 435 double cms_time_since_begin() const; 436 double cms_time_since_end() const; 437 438 // Higher level statistics--caller must check that valid() returns true before 439 // calling. 440 441 // Returns bytes promoted per second of wall clock time. 442 double promotion_rate() const; 443 444 // Returns bytes directly allocated per second of wall clock time. 445 double cms_allocation_rate() const; 446 447 // Rate at which space in the cms generation is being consumed (sum of the 448 // above two). 449 double cms_consumption_rate() const; 450 451 // Returns an estimate of the number of seconds until the cms generation will 452 // fill up, assuming no collection work is done. 453 double time_until_cms_gen_full() const; 454 455 // Returns an estimate of the number of seconds remaining until 456 // the cms generation collection should start. 457 double time_until_cms_start() const; 458 459 // End of higher level statistics. 460 461 // Returns the cms incremental mode duty cycle, as a percentage (0-100). 462 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; } 463 464 // Update the duty cycle and return the new value. 465 unsigned int icms_update_duty_cycle(); 466 467 // Debugging. 468 void print_on(outputStream* st) const PRODUCT_RETURN; 469 void print() const { print_on(gclog_or_tty); } 470 }; 471 472 // A closure related to weak references processing which 473 // we embed in the CMSCollector, since we need to pass 474 // it to the reference processor for secondary filtering 475 // of references based on reachability of referent; 476 // see role of _is_alive_non_header closure in the 477 // ReferenceProcessor class. 478 // For objects in the CMS generation, this closure checks 479 // if the object is "live" (reachable). Used in weak 480 // reference processing. 481 class CMSIsAliveClosure: public BoolObjectClosure { 482 const MemRegion _span; 483 const CMSBitMap* _bit_map; 484 485 friend class CMSCollector; 486 public: 487 CMSIsAliveClosure(MemRegion span, 488 CMSBitMap* bit_map): 489 _span(span), 490 _bit_map(bit_map) { 491 assert(!span.is_empty(), "Empty span could spell trouble"); 492 } 493 494 bool do_object_b(oop obj); 495 }; 496 497 498 // Implements AbstractRefProcTaskExecutor for CMS. 499 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 500 public: 501 502 CMSRefProcTaskExecutor(CMSCollector& collector) 503 : _collector(collector) 504 { } 505 506 // Executes a task using worker threads. 507 virtual void execute(ProcessTask& task); 508 virtual void execute(EnqueueTask& task); 509 private: 510 CMSCollector& _collector; 511 }; 512 513 514 class CMSCollector: public CHeapObj<mtGC> { 515 friend class VMStructs; 516 friend class ConcurrentMarkSweepThread; 517 friend class ConcurrentMarkSweepGeneration; 518 friend class CompactibleFreeListSpace; 519 friend class CMSParMarkTask; 520 friend class CMSParInitialMarkTask; 521 friend class CMSParRemarkTask; 522 friend class CMSConcMarkingTask; 523 friend class CMSRefProcTaskProxy; 524 friend class CMSRefProcTaskExecutor; 525 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 526 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 527 friend class PushOrMarkClosure; // to access _restart_addr 528 friend class Par_PushOrMarkClosure; // to access _restart_addr 529 friend class MarkFromRootsClosure; // -- ditto -- 530 // ... and for clearing cards 531 friend class Par_MarkFromRootsClosure; // to access _restart_addr 532 // ... and for clearing cards 533 friend class Par_ConcMarkingClosure; // to access _restart_addr etc. 534 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 535 friend class PushAndMarkVerifyClosure; // -- ditto -- 536 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 537 friend class PushAndMarkClosure; // -- ditto -- 538 friend class Par_PushAndMarkClosure; // -- ditto -- 539 friend class CMSKeepAliveClosure; // -- ditto -- 540 friend class CMSDrainMarkingStackClosure; // -- ditto -- 541 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 542 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 543 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 544 friend class VM_CMS_Operation; 545 friend class VM_CMS_Initial_Mark; 546 friend class VM_CMS_Final_Remark; 547 friend class TraceCMSMemoryManagerStats; 548 549 private: 550 jlong _time_of_last_gc; 551 void update_time_of_last_gc(jlong now) { 552 _time_of_last_gc = now; 553 } 554 555 OopTaskQueueSet* _task_queues; 556 557 // Overflow list of grey objects, threaded through mark-word 558 // Manipulated with CAS in the parallel/multi-threaded case. 559 oop _overflow_list; 560 // The following array-pair keeps track of mark words 561 // displaced for accommodating overflow list above. 562 // This code will likely be revisited under RFE#4922830. 563 Stack<oop, mtGC> _preserved_oop_stack; 564 Stack<markOop, mtGC> _preserved_mark_stack; 565 566 int* _hash_seed; 567 568 // In support of multi-threaded concurrent phases 569 YieldingFlexibleWorkGang* _conc_workers; 570 571 // Performance Counters 572 CollectorCounters* _gc_counters; 573 574 // Initialization Errors 575 bool _completed_initialization; 576 577 // In support of ExplicitGCInvokesConcurrent 578 static bool _full_gc_requested; 579 static GCCause::Cause _full_gc_cause; 580 unsigned int _collection_count_start; 581 582 // Should we unload classes this concurrent cycle? 583 bool _should_unload_classes; 584 unsigned int _concurrent_cycles_since_last_unload; 585 unsigned int concurrent_cycles_since_last_unload() const { 586 return _concurrent_cycles_since_last_unload; 587 } 588 // Did we (allow) unload classes in the previous concurrent cycle? 589 bool unloaded_classes_last_cycle() const { 590 return concurrent_cycles_since_last_unload() == 0; 591 } 592 // Root scanning options for perm gen 593 int _roots_scanning_options; 594 int roots_scanning_options() const { return _roots_scanning_options; } 595 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 596 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 597 598 // Verification support 599 CMSBitMap _verification_mark_bm; 600 void verify_after_remark_work_1(); 601 void verify_after_remark_work_2(); 602 603 // True if any verification flag is on. 604 bool _verifying; 605 bool verifying() const { return _verifying; } 606 void set_verifying(bool v) { _verifying = v; } 607 608 // Collector policy 609 ConcurrentMarkSweepPolicy* _collector_policy; 610 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 611 612 void set_did_compact(bool v); 613 614 // XXX Move these to CMSStats ??? FIX ME !!! 615 elapsedTimer _inter_sweep_timer; // Time between sweeps 616 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 617 // Padded decaying average estimates of the above 618 AdaptivePaddedAverage _inter_sweep_estimate; 619 AdaptivePaddedAverage _intra_sweep_estimate; 620 621 CMSTracer* _gc_tracer_cm; 622 ConcurrentGCTimer* _gc_timer_cm; 623 624 bool _cms_start_registered; 625 626 GCHeapSummary _last_heap_summary; 627 MetaspaceSummary _last_metaspace_summary; 628 629 void register_foreground_gc_start(GCCause::Cause cause); 630 void register_gc_start(GCCause::Cause cause); 631 void register_gc_end(); 632 void save_heap_summary(); 633 void report_heap_summary(GCWhen::Type when); 634 635 protected: 636 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 637 MemRegion _span; // Span covering above two 638 CardTableRS* _ct; // Card table 639 640 // CMS marking support structures 641 CMSBitMap _markBitMap; 642 CMSBitMap _modUnionTable; 643 CMSMarkStack _markStack; 644 645 HeapWord* _restart_addr; // In support of marking stack overflow 646 void lower_restart_addr(HeapWord* low); 647 648 // Counters in support of marking stack / work queue overflow handling: 649 // a non-zero value indicates certain types of overflow events during 650 // the current CMS cycle and could lead to stack resizing efforts at 651 // an opportune future time. 652 size_t _ser_pmc_preclean_ovflw; 653 size_t _ser_pmc_remark_ovflw; 654 size_t _par_pmc_remark_ovflw; 655 size_t _ser_kac_preclean_ovflw; 656 size_t _ser_kac_ovflw; 657 size_t _par_kac_ovflw; 658 NOT_PRODUCT(ssize_t _num_par_pushes;) 659 660 // ("Weak") Reference processing support. 661 ReferenceProcessor* _ref_processor; 662 CMSIsAliveClosure _is_alive_closure; 663 // Keep this textually after _markBitMap and _span; c'tor dependency. 664 665 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 666 ModUnionClosure _modUnionClosure; 667 ModUnionClosurePar _modUnionClosurePar; 668 669 // CMS abstract state machine 670 // initial_state: Idling 671 // next_state(Idling) = {Marking} 672 // next_state(Marking) = {Precleaning, Sweeping} 673 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 674 // next_state(AbortablePreclean) = {FinalMarking} 675 // next_state(FinalMarking) = {Sweeping} 676 // next_state(Sweeping) = {Resizing} 677 // next_state(Resizing) = {Resetting} 678 // next_state(Resetting) = {Idling} 679 // The numeric values below are chosen so that: 680 // . _collectorState <= Idling == post-sweep && pre-mark 681 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 682 // precleaning || abortablePrecleanb 683 public: 684 enum CollectorState { 685 Resizing = 0, 686 Resetting = 1, 687 Idling = 2, 688 InitialMarking = 3, 689 Marking = 4, 690 Precleaning = 5, 691 AbortablePreclean = 6, 692 FinalMarking = 7, 693 Sweeping = 8 694 }; 695 protected: 696 static CollectorState _collectorState; 697 698 // State related to prologue/epilogue invocation for my generations 699 bool _between_prologue_and_epilogue; 700 701 // Signaling/State related to coordination between fore- and background GC 702 // Note: When the baton has been passed from background GC to foreground GC, 703 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 704 static bool _foregroundGCIsActive; // true iff foreground collector is active or 705 // wants to go active 706 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 707 // yet passed the baton to the foreground GC 708 709 // Support for CMSScheduleRemark (abortable preclean) 710 bool _abort_preclean; 711 bool _start_sampling; 712 713 int _numYields; 714 size_t _numDirtyCards; 715 size_t _sweep_count; 716 // Number of full gc's since the last concurrent gc. 717 uint _full_gcs_since_conc_gc; 718 719 // Occupancy used for bootstrapping stats 720 double _bootstrap_occupancy; 721 722 // Timer 723 elapsedTimer _timer; 724 725 // Timing, allocation and promotion statistics, used for scheduling. 726 CMSStats _stats; 727 728 // Allocation limits installed in the young gen, used only in 729 // CMSIncrementalMode. When an allocation in the young gen would cross one of 730 // these limits, the cms generation is notified and the cms thread is started 731 // or stopped, respectively. 732 HeapWord* _icms_start_limit; 733 HeapWord* _icms_stop_limit; 734 735 enum CMS_op_type { 736 CMS_op_checkpointRootsInitial, 737 CMS_op_checkpointRootsFinal 738 }; 739 740 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 741 bool stop_world_and_do(CMS_op_type op); 742 743 OopTaskQueueSet* task_queues() { return _task_queues; } 744 int* hash_seed(int i) { return &_hash_seed[i]; } 745 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 746 747 // Support for parallelizing Eden rescan in CMS remark phase 748 void sample_eden(); // ... sample Eden space top 749 750 private: 751 // Support for parallelizing young gen rescan in CMS remark phase 752 Generation* _young_gen; // the younger gen 753 HeapWord** _top_addr; // ... Top of Eden 754 HeapWord** _end_addr; // ... End of Eden 755 Mutex* _eden_chunk_lock; 756 HeapWord** _eden_chunk_array; // ... Eden partitioning array 757 size_t _eden_chunk_index; // ... top (exclusive) of array 758 size_t _eden_chunk_capacity; // ... max entries in array 759 760 // Support for parallelizing survivor space rescan 761 HeapWord** _survivor_chunk_array; 762 size_t _survivor_chunk_index; 763 size_t _survivor_chunk_capacity; 764 size_t* _cursor; 765 ChunkArray* _survivor_plab_array; 766 767 // Support for marking stack overflow handling 768 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 769 bool par_take_from_overflow_list(size_t num, 770 OopTaskQueue* to_work_q, 771 int no_of_gc_threads); 772 void push_on_overflow_list(oop p); 773 void par_push_on_overflow_list(oop p); 774 // The following is, obviously, not, in general, "MT-stable" 775 bool overflow_list_is_empty() const; 776 777 void preserve_mark_if_necessary(oop p); 778 void par_preserve_mark_if_necessary(oop p); 779 void preserve_mark_work(oop p, markOop m); 780 void restore_preserved_marks_if_any(); 781 NOT_PRODUCT(bool no_preserved_marks() const;) 782 // In support of testing overflow code 783 NOT_PRODUCT(int _overflow_counter;) 784 NOT_PRODUCT(bool simulate_overflow();) // Sequential 785 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 786 787 // CMS work methods 788 void checkpointRootsInitialWork(bool asynch); // Initial checkpoint work 789 790 // A return value of false indicates failure due to stack overflow 791 bool markFromRootsWork(bool asynch); // Concurrent marking work 792 793 public: // FIX ME!!! only for testing 794 bool do_marking_st(bool asynch); // Single-threaded marking 795 bool do_marking_mt(bool asynch); // Multi-threaded marking 796 797 private: 798 799 // Concurrent precleaning work 800 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, 801 ScanMarkedObjectsAgainCarefullyClosure* cl); 802 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, 803 ScanMarkedObjectsAgainCarefullyClosure* cl); 804 // Does precleaning work, returning a quantity indicative of 805 // the amount of "useful work" done. 806 size_t preclean_work(bool clean_refs, bool clean_survivors); 807 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 808 void abortable_preclean(); // Preclean while looking for possible abort 809 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 810 // Helper function for above; merge-sorts the per-thread plab samples 811 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 812 // Resets (i.e. clears) the per-thread plab sample vectors 813 void reset_survivor_plab_arrays(); 814 815 // Final (second) checkpoint work 816 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs, 817 bool init_mark_was_synchronous); 818 // Work routine for parallel version of remark 819 void do_remark_parallel(); 820 // Work routine for non-parallel version of remark 821 void do_remark_non_parallel(); 822 // Reference processing work routine (during second checkpoint) 823 void refProcessingWork(bool asynch, bool clear_all_soft_refs); 824 825 // Concurrent sweeping work 826 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch); 827 828 // (Concurrent) resetting of support data structures 829 void reset(bool asynch); 830 831 // Clear _expansion_cause fields of constituent generations 832 void clear_expansion_cause(); 833 834 // An auxiliary method used to record the ends of 835 // used regions of each generation to limit the extent of sweep 836 void save_sweep_limits(); 837 838 // A work method used by foreground collection to determine 839 // what type of collection (compacting or not, continuing or fresh) 840 // it should do. 841 void decide_foreground_collection_type(bool clear_all_soft_refs, 842 bool* should_compact, bool* should_start_over); 843 844 // A work method used by the foreground collector to do 845 // a mark-sweep-compact. 846 void do_compaction_work(bool clear_all_soft_refs); 847 848 // A work method used by the foreground collector to do 849 // a mark-sweep, after taking over from a possibly on-going 850 // concurrent mark-sweep collection. 851 void do_mark_sweep_work(bool clear_all_soft_refs, 852 CollectorState first_state, bool should_start_over); 853 854 // Work methods for reporting concurrent mode interruption or failure 855 bool is_external_interruption(); 856 void report_concurrent_mode_interruption(); 857 858 // If the background GC is active, acquire control from the background 859 // GC and do the collection. 860 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 861 862 // For synchronizing passing of control from background to foreground 863 // GC. waitForForegroundGC() is called by the background 864 // collector. It if had to wait for a foreground collection, 865 // it returns true and the background collection should assume 866 // that the collection was finished by the foreground 867 // collector. 868 bool waitForForegroundGC(); 869 870 // Incremental mode triggering: recompute the icms duty cycle and set the 871 // allocation limits in the young gen. 872 void icms_update_allocation_limits(); 873 874 size_t block_size_using_printezis_bits(HeapWord* addr) const; 875 size_t block_size_if_printezis_bits(HeapWord* addr) const; 876 HeapWord* next_card_start_after_block(HeapWord* addr) const; 877 878 void setup_cms_unloading_and_verification_state(); 879 public: 880 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 881 CardTableRS* ct, 882 ConcurrentMarkSweepPolicy* cp); 883 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 884 885 ReferenceProcessor* ref_processor() { return _ref_processor; } 886 void ref_processor_init(); 887 888 Mutex* bitMapLock() const { return _markBitMap.lock(); } 889 static CollectorState abstract_state() { return _collectorState; } 890 891 bool should_abort_preclean() const; // Whether preclean should be aborted. 892 size_t get_eden_used() const; 893 size_t get_eden_capacity() const; 894 895 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 896 897 // Locking checks 898 NOT_PRODUCT(static bool have_cms_token();) 899 900 // XXXPERM bool should_collect(bool full, size_t size, bool tlab); 901 bool shouldConcurrentCollect(); 902 903 void collect(bool full, 904 bool clear_all_soft_refs, 905 size_t size, 906 bool tlab); 907 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause); 908 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause); 909 910 // In support of ExplicitGCInvokesConcurrent 911 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 912 // Should we unload classes in a particular concurrent cycle? 913 bool should_unload_classes() const { 914 return _should_unload_classes; 915 } 916 void update_should_unload_classes(); 917 918 void direct_allocated(HeapWord* start, size_t size); 919 920 // Object is dead if not marked and current phase is sweeping. 921 bool is_dead_obj(oop obj) const; 922 923 // After a promotion (of "start"), do any necessary marking. 924 // If "par", then it's being done by a parallel GC thread. 925 // The last two args indicate if we need precise marking 926 // and if so the size of the object so it can be dirtied 927 // in its entirety. 928 void promoted(bool par, HeapWord* start, 929 bool is_obj_array, size_t obj_size); 930 931 HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 932 size_t word_size); 933 934 void getFreelistLocks() const; 935 void releaseFreelistLocks() const; 936 bool haveFreelistLocks() const; 937 938 // Adjust size of underlying generation 939 void compute_new_size(); 940 941 // GC prologue and epilogue 942 void gc_prologue(bool full); 943 void gc_epilogue(bool full); 944 945 jlong time_of_last_gc(jlong now) { 946 if (_collectorState <= Idling) { 947 // gc not in progress 948 return _time_of_last_gc; 949 } else { 950 // collection in progress 951 return now; 952 } 953 } 954 955 // Support for parallel remark of survivor space 956 void* get_data_recorder(int thr_num); 957 void sample_eden_chunk(); 958 959 CMSBitMap* markBitMap() { return &_markBitMap; } 960 void directAllocated(HeapWord* start, size_t size); 961 962 // Main CMS steps and related support 963 void checkpointRootsInitial(bool asynch); 964 bool markFromRoots(bool asynch); // a return value of false indicates failure 965 // due to stack overflow 966 void preclean(); 967 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs, 968 bool init_mark_was_synchronous); 969 void sweep(bool asynch); 970 971 // Check that the currently executing thread is the expected 972 // one (foreground collector or background collector). 973 static void check_correct_thread_executing() PRODUCT_RETURN; 974 // XXXPERM void print_statistics() PRODUCT_RETURN; 975 976 bool is_cms_reachable(HeapWord* addr); 977 978 // Performance Counter Support 979 CollectorCounters* counters() { return _gc_counters; } 980 981 // Timer stuff 982 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 983 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 984 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 985 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } 986 987 int yields() { return _numYields; } 988 void resetYields() { _numYields = 0; } 989 void incrementYields() { _numYields++; } 990 void resetNumDirtyCards() { _numDirtyCards = 0; } 991 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 992 size_t numDirtyCards() { return _numDirtyCards; } 993 994 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 995 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 996 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 997 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 998 size_t sweep_count() const { return _sweep_count; } 999 void increment_sweep_count() { _sweep_count++; } 1000 1001 // Timers/stats for gc scheduling and incremental mode pacing. 1002 CMSStats& stats() { return _stats; } 1003 1004 // Convenience methods that check whether CMSIncrementalMode is enabled and 1005 // forward to the corresponding methods in ConcurrentMarkSweepThread. 1006 static void start_icms(); 1007 static void stop_icms(); // Called at the end of the cms cycle. 1008 static void disable_icms(); // Called before a foreground collection. 1009 static void enable_icms(); // Called after a foreground collection. 1010 void icms_wait(); // Called at yield points. 1011 1012 // Adaptive size policy 1013 AdaptiveSizePolicy* size_policy(); 1014 1015 static void print_on_error(outputStream* st); 1016 1017 // Debugging 1018 void verify(); 1019 bool verify_after_remark(bool silent = VerifySilently); 1020 void verify_ok_to_terminate() const PRODUCT_RETURN; 1021 void verify_work_stacks_empty() const PRODUCT_RETURN; 1022 void verify_overflow_empty() const PRODUCT_RETURN; 1023 1024 // Convenience methods in support of debugging 1025 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 1026 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 1027 1028 // Accessors 1029 CMSMarkStack* verification_mark_stack() { return &_markStack; } 1030 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 1031 1032 // Initialization errors 1033 bool completed_initialization() { return _completed_initialization; } 1034 1035 void print_eden_and_survivor_chunk_arrays(); 1036 }; 1037 1038 class CMSExpansionCause : public AllStatic { 1039 public: 1040 enum Cause { 1041 _no_expansion, 1042 _satisfy_free_ratio, 1043 _satisfy_promotion, 1044 _satisfy_allocation, 1045 _allocate_par_lab, 1046 _allocate_par_spooling_space, 1047 _adaptive_size_policy 1048 }; 1049 // Return a string describing the cause of the expansion. 1050 static const char* to_string(CMSExpansionCause::Cause cause); 1051 }; 1052 1053 class ConcurrentMarkSweepGeneration: public CardGeneration { 1054 friend class VMStructs; 1055 friend class ConcurrentMarkSweepThread; 1056 friend class ConcurrentMarkSweep; 1057 friend class CMSCollector; 1058 protected: 1059 static CMSCollector* _collector; // the collector that collects us 1060 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1061 1062 // Performance Counters 1063 GenerationCounters* _gen_counters; 1064 GSpaceCounters* _space_counters; 1065 1066 // Words directly allocated, used by CMSStats. 1067 size_t _direct_allocated_words; 1068 1069 // Non-product stat counters 1070 NOT_PRODUCT( 1071 size_t _numObjectsPromoted; 1072 size_t _numWordsPromoted; 1073 size_t _numObjectsAllocated; 1074 size_t _numWordsAllocated; 1075 ) 1076 1077 // Used for sizing decisions 1078 bool _incremental_collection_failed; 1079 bool incremental_collection_failed() { 1080 return _incremental_collection_failed; 1081 } 1082 void set_incremental_collection_failed() { 1083 _incremental_collection_failed = true; 1084 } 1085 void clear_incremental_collection_failed() { 1086 _incremental_collection_failed = false; 1087 } 1088 1089 // accessors 1090 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1091 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1092 1093 private: 1094 // For parallel young-gen GC support. 1095 CMSParGCThreadState** _par_gc_thread_states; 1096 1097 // Reason generation was expanded 1098 CMSExpansionCause::Cause _expansion_cause; 1099 1100 // In support of MinChunkSize being larger than min object size 1101 const double _dilatation_factor; 1102 1103 enum CollectionTypes { 1104 Concurrent_collection_type = 0, 1105 MS_foreground_collection_type = 1, 1106 MSC_foreground_collection_type = 2, 1107 Unknown_collection_type = 3 1108 }; 1109 1110 CollectionTypes _debug_collection_type; 1111 1112 // True if a compacting collection was done. 1113 bool _did_compact; 1114 bool did_compact() { return _did_compact; } 1115 1116 // Fraction of current occupancy at which to start a CMS collection which 1117 // will collect this generation (at least). 1118 double _initiating_occupancy; 1119 1120 protected: 1121 // Shrink generation by specified size (returns false if unable to shrink) 1122 void shrink_free_list_by(size_t bytes); 1123 1124 // Update statistics for GC 1125 virtual void update_gc_stats(int level, bool full); 1126 1127 // Maximum available space in the generation (including uncommitted) 1128 // space. 1129 size_t max_available() const; 1130 1131 // getter and initializer for _initiating_occupancy field. 1132 double initiating_occupancy() const { return _initiating_occupancy; } 1133 void init_initiating_occupancy(intx io, uintx tr); 1134 1135 public: 1136 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1137 int level, CardTableRS* ct, 1138 bool use_adaptive_freelists, 1139 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 1140 1141 // Accessors 1142 CMSCollector* collector() const { return _collector; } 1143 static void set_collector(CMSCollector* collector) { 1144 assert(_collector == NULL, "already set"); 1145 _collector = collector; 1146 } 1147 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1148 1149 Mutex* freelistLock() const; 1150 1151 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1152 1153 void set_did_compact(bool v) { _did_compact = v; } 1154 1155 bool refs_discovery_is_atomic() const { return false; } 1156 bool refs_discovery_is_mt() const { 1157 // Note: CMS does MT-discovery during the parallel-remark 1158 // phases. Use ReferenceProcessorMTMutator to make refs 1159 // discovery MT-safe during such phases or other parallel 1160 // discovery phases in the future. This may all go away 1161 // if/when we decide that refs discovery is sufficiently 1162 // rare that the cost of the CAS's involved is in the 1163 // noise. That's a measurement that should be done, and 1164 // the code simplified if that turns out to be the case. 1165 return ConcGCThreads > 1; 1166 } 1167 1168 // Override 1169 virtual void ref_processor_init(); 1170 1171 // Grow generation by specified size (returns false if unable to grow) 1172 bool grow_by(size_t bytes); 1173 // Grow generation to reserved size. 1174 bool grow_to_reserved(); 1175 1176 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1177 1178 // Space enquiries 1179 size_t capacity() const; 1180 size_t used() const; 1181 size_t free() const; 1182 double occupancy() const { return ((double)used())/((double)capacity()); } 1183 size_t contiguous_available() const; 1184 size_t unsafe_max_alloc_nogc() const; 1185 1186 // over-rides 1187 MemRegion used_region() const; 1188 MemRegion used_region_at_save_marks() const; 1189 1190 // Does a "full" (forced) collection invoked on this generation collect 1191 // all younger generations as well? Note that the second conjunct is a 1192 // hack to allow the collection of the younger gen first if the flag is 1193 // set. 1194 virtual bool full_collects_younger_generations() const { 1195 return UseCMSCompactAtFullCollection && !ScavengeBeforeFullGC; 1196 } 1197 1198 void space_iterate(SpaceClosure* blk, bool usedOnly = false); 1199 1200 // Support for compaction 1201 CompactibleSpace* first_compaction_space() const; 1202 // Adjust quantities in the generation affected by 1203 // the compaction. 1204 void reset_after_compaction(); 1205 1206 // Allocation support 1207 HeapWord* allocate(size_t size, bool tlab); 1208 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1209 oop promote(oop obj, size_t obj_size); 1210 HeapWord* par_allocate(size_t size, bool tlab) { 1211 return allocate(size, tlab); 1212 } 1213 1214 // Incremental mode triggering. 1215 HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 1216 size_t word_size); 1217 1218 // Used by CMSStats to track direct allocation. The value is sampled and 1219 // reset after each young gen collection. 1220 size_t direct_allocated_words() const { return _direct_allocated_words; } 1221 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1222 1223 // Overrides for parallel promotion. 1224 virtual oop par_promote(int thread_num, 1225 oop obj, markOop m, size_t word_sz); 1226 // This one should not be called for CMS. 1227 virtual void par_promote_alloc_undo(int thread_num, 1228 HeapWord* obj, size_t word_sz); 1229 virtual void par_promote_alloc_done(int thread_num); 1230 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1231 1232 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1233 1234 // Inform this (non-young) generation that a promotion failure was 1235 // encountered during a collection of a younger generation that 1236 // promotes into this generation. 1237 virtual void promotion_failure_occurred(); 1238 1239 bool should_collect(bool full, size_t size, bool tlab); 1240 virtual bool should_concurrent_collect() const; 1241 virtual bool is_too_full() const; 1242 void collect(bool full, 1243 bool clear_all_soft_refs, 1244 size_t size, 1245 bool tlab); 1246 1247 HeapWord* expand_and_allocate(size_t word_size, 1248 bool tlab, 1249 bool parallel = false); 1250 1251 // GC prologue and epilogue 1252 void gc_prologue(bool full); 1253 void gc_prologue_work(bool full, bool registerClosure, 1254 ModUnionClosure* modUnionClosure); 1255 void gc_epilogue(bool full); 1256 void gc_epilogue_work(bool full); 1257 1258 // Time since last GC of this generation 1259 jlong time_of_last_gc(jlong now) { 1260 return collector()->time_of_last_gc(now); 1261 } 1262 void update_time_of_last_gc(jlong now) { 1263 collector()-> update_time_of_last_gc(now); 1264 } 1265 1266 // Allocation failure 1267 void expand(size_t bytes, size_t expand_bytes, 1268 CMSExpansionCause::Cause cause); 1269 virtual bool expand(size_t bytes, size_t expand_bytes); 1270 void shrink(size_t bytes); 1271 void shrink_by(size_t bytes); 1272 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1273 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1274 1275 // Iteration support and related enquiries 1276 void save_marks(); 1277 bool no_allocs_since_save_marks(); 1278 void younger_refs_iterate(OopsInGenClosure* cl); 1279 1280 // Iteration support specific to CMS generations 1281 void save_sweep_limit(); 1282 1283 // More iteration support 1284 virtual void oop_iterate(ExtendedOopClosure* cl); 1285 virtual void safe_object_iterate(ObjectClosure* cl); 1286 virtual void object_iterate(ObjectClosure* cl); 1287 1288 // Need to declare the full complement of closures, whether we'll 1289 // override them or not, or get message from the compiler: 1290 // oop_since_save_marks_iterate_nv hides virtual function... 1291 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1292 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1293 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1294 1295 // Smart allocation XXX -- move to CFLSpace? 1296 void setNearLargestChunk(); 1297 bool isNearLargestChunk(HeapWord* addr); 1298 1299 // Get the chunk at the end of the space. Delegates to 1300 // the space. 1301 FreeChunk* find_chunk_at_end(); 1302 1303 void post_compact(); 1304 1305 // Debugging 1306 void prepare_for_verify(); 1307 void verify(); 1308 void print_statistics() PRODUCT_RETURN; 1309 1310 // Performance Counters support 1311 virtual void update_counters(); 1312 virtual void update_counters(size_t used); 1313 void initialize_performance_counters(); 1314 CollectorCounters* counters() { return collector()->counters(); } 1315 1316 // Support for parallel remark of survivor space 1317 void* get_data_recorder(int thr_num) { 1318 //Delegate to collector 1319 return collector()->get_data_recorder(thr_num); 1320 } 1321 void sample_eden_chunk() { 1322 //Delegate to collector 1323 return collector()->sample_eden_chunk(); 1324 } 1325 1326 // Printing 1327 const char* name() const; 1328 virtual const char* short_name() const { return "CMS"; } 1329 void print() const; 1330 void printOccupancy(const char* s); 1331 bool must_be_youngest() const { return false; } 1332 bool must_be_oldest() const { return true; } 1333 1334 // Resize the generation after a compacting GC. The 1335 // generation can be treated as a contiguous space 1336 // after the compaction. 1337 virtual void compute_new_size(); 1338 // Resize the generation after a non-compacting 1339 // collection. 1340 void compute_new_size_free_list(); 1341 1342 CollectionTypes debug_collection_type() { return _debug_collection_type; } 1343 void rotate_debug_collection_type(); 1344 }; 1345 1346 // 1347 // Closures of various sorts used by CMS to accomplish its work 1348 // 1349 1350 // This closure is used to do concurrent marking from the roots 1351 // following the first checkpoint. 1352 class MarkFromRootsClosure: public BitMapClosure { 1353 CMSCollector* _collector; 1354 MemRegion _span; 1355 CMSBitMap* _bitMap; 1356 CMSBitMap* _mut; 1357 CMSMarkStack* _markStack; 1358 bool _yield; 1359 int _skipBits; 1360 HeapWord* _finger; 1361 HeapWord* _threshold; 1362 DEBUG_ONLY(bool _verifying;) 1363 1364 public: 1365 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1366 CMSBitMap* bitMap, 1367 CMSMarkStack* markStack, 1368 bool should_yield, bool verifying = false); 1369 bool do_bit(size_t offset); 1370 void reset(HeapWord* addr); 1371 inline void do_yield_check(); 1372 1373 private: 1374 void scanOopsInOop(HeapWord* ptr); 1375 void do_yield_work(); 1376 }; 1377 1378 // This closure is used to do concurrent multi-threaded 1379 // marking from the roots following the first checkpoint. 1380 // XXX This should really be a subclass of The serial version 1381 // above, but i have not had the time to refactor things cleanly. 1382 class Par_MarkFromRootsClosure: public BitMapClosure { 1383 CMSCollector* _collector; 1384 MemRegion _whole_span; 1385 MemRegion _span; 1386 CMSBitMap* _bit_map; 1387 CMSBitMap* _mut; 1388 OopTaskQueue* _work_queue; 1389 CMSMarkStack* _overflow_stack; 1390 bool _yield; 1391 int _skip_bits; 1392 HeapWord* _finger; 1393 HeapWord* _threshold; 1394 CMSConcMarkingTask* _task; 1395 public: 1396 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1397 MemRegion span, 1398 CMSBitMap* bit_map, 1399 OopTaskQueue* work_queue, 1400 CMSMarkStack* overflow_stack, 1401 bool should_yield); 1402 bool do_bit(size_t offset); 1403 inline void do_yield_check(); 1404 1405 private: 1406 void scan_oops_in_oop(HeapWord* ptr); 1407 void do_yield_work(); 1408 bool get_work_from_overflow_stack(); 1409 }; 1410 1411 // The following closures are used to do certain kinds of verification of 1412 // CMS marking. 1413 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1414 CMSCollector* _collector; 1415 MemRegion _span; 1416 CMSBitMap* _verification_bm; 1417 CMSBitMap* _cms_bm; 1418 CMSMarkStack* _mark_stack; 1419 protected: 1420 void do_oop(oop p); 1421 template <class T> inline void do_oop_work(T *p) { 1422 oop obj = oopDesc::load_decode_heap_oop(p); 1423 do_oop(obj); 1424 } 1425 public: 1426 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1427 MemRegion span, 1428 CMSBitMap* verification_bm, 1429 CMSBitMap* cms_bm, 1430 CMSMarkStack* mark_stack); 1431 void do_oop(oop* p); 1432 void do_oop(narrowOop* p); 1433 1434 // Deal with a stack overflow condition 1435 void handle_stack_overflow(HeapWord* lost); 1436 }; 1437 1438 class MarkFromRootsVerifyClosure: public BitMapClosure { 1439 CMSCollector* _collector; 1440 MemRegion _span; 1441 CMSBitMap* _verification_bm; 1442 CMSBitMap* _cms_bm; 1443 CMSMarkStack* _mark_stack; 1444 HeapWord* _finger; 1445 PushAndMarkVerifyClosure _pam_verify_closure; 1446 public: 1447 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1448 CMSBitMap* verification_bm, 1449 CMSBitMap* cms_bm, 1450 CMSMarkStack* mark_stack); 1451 bool do_bit(size_t offset); 1452 void reset(HeapWord* addr); 1453 }; 1454 1455 1456 // This closure is used to check that a certain set of bits is 1457 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1458 class FalseBitMapClosure: public BitMapClosure { 1459 public: 1460 bool do_bit(size_t offset) { 1461 guarantee(false, "Should not have a 1 bit"); 1462 return true; 1463 } 1464 }; 1465 1466 // A version of ObjectClosure with "memory" (see _previous_address below) 1467 class UpwardsObjectClosure: public BoolObjectClosure { 1468 HeapWord* _previous_address; 1469 public: 1470 UpwardsObjectClosure() : _previous_address(NULL) { } 1471 void set_previous(HeapWord* addr) { _previous_address = addr; } 1472 HeapWord* previous() { return _previous_address; } 1473 // A return value of "true" can be used by the caller to decide 1474 // if this object's end should *NOT* be recorded in 1475 // _previous_address above. 1476 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1477 }; 1478 1479 // This closure is used during the second checkpointing phase 1480 // to rescan the marked objects on the dirty cards in the mod 1481 // union table and the card table proper. It's invoked via 1482 // MarkFromDirtyCardsClosure below. It uses either 1483 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1484 // declared in genOopClosures.hpp to accomplish some of its work. 1485 // In the parallel case the bitMap is shared, so access to 1486 // it needs to be suitably synchronized for updates by embedded 1487 // closures that update it; however, this closure itself only 1488 // reads the bit_map and because it is idempotent, is immune to 1489 // reading stale values. 1490 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1491 #ifdef ASSERT 1492 CMSCollector* _collector; 1493 MemRegion _span; 1494 union { 1495 CMSMarkStack* _mark_stack; 1496 OopTaskQueue* _work_queue; 1497 }; 1498 #endif // ASSERT 1499 bool _parallel; 1500 CMSBitMap* _bit_map; 1501 union { 1502 MarkRefsIntoAndScanClosure* _scan_closure; 1503 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1504 }; 1505 1506 public: 1507 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1508 MemRegion span, 1509 ReferenceProcessor* rp, 1510 CMSBitMap* bit_map, 1511 CMSMarkStack* mark_stack, 1512 MarkRefsIntoAndScanClosure* cl): 1513 #ifdef ASSERT 1514 _collector(collector), 1515 _span(span), 1516 _mark_stack(mark_stack), 1517 #endif // ASSERT 1518 _parallel(false), 1519 _bit_map(bit_map), 1520 _scan_closure(cl) { } 1521 1522 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1523 MemRegion span, 1524 ReferenceProcessor* rp, 1525 CMSBitMap* bit_map, 1526 OopTaskQueue* work_queue, 1527 Par_MarkRefsIntoAndScanClosure* cl): 1528 #ifdef ASSERT 1529 _collector(collector), 1530 _span(span), 1531 _work_queue(work_queue), 1532 #endif // ASSERT 1533 _parallel(true), 1534 _bit_map(bit_map), 1535 _par_scan_closure(cl) { } 1536 1537 bool do_object_b(oop obj) { 1538 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1539 return false; 1540 } 1541 bool do_object_bm(oop p, MemRegion mr); 1542 }; 1543 1544 // This closure is used during the second checkpointing phase 1545 // to rescan the marked objects on the dirty cards in the mod 1546 // union table and the card table proper. It invokes 1547 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1548 // In the parallel case, the bit map is shared and requires 1549 // synchronized access. 1550 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1551 CompactibleFreeListSpace* _space; 1552 ScanMarkedObjectsAgainClosure _scan_cl; 1553 size_t _num_dirty_cards; 1554 1555 public: 1556 MarkFromDirtyCardsClosure(CMSCollector* collector, 1557 MemRegion span, 1558 CompactibleFreeListSpace* space, 1559 CMSBitMap* bit_map, 1560 CMSMarkStack* mark_stack, 1561 MarkRefsIntoAndScanClosure* cl): 1562 _space(space), 1563 _num_dirty_cards(0), 1564 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1565 mark_stack, cl) { } 1566 1567 MarkFromDirtyCardsClosure(CMSCollector* collector, 1568 MemRegion span, 1569 CompactibleFreeListSpace* space, 1570 CMSBitMap* bit_map, 1571 OopTaskQueue* work_queue, 1572 Par_MarkRefsIntoAndScanClosure* cl): 1573 _space(space), 1574 _num_dirty_cards(0), 1575 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1576 work_queue, cl) { } 1577 1578 void do_MemRegion(MemRegion mr); 1579 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1580 size_t num_dirty_cards() { return _num_dirty_cards; } 1581 }; 1582 1583 // This closure is used in the non-product build to check 1584 // that there are no MemRegions with a certain property. 1585 class FalseMemRegionClosure: public MemRegionClosure { 1586 void do_MemRegion(MemRegion mr) { 1587 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1588 guarantee(false, "Should never be here"); 1589 } 1590 }; 1591 1592 // This closure is used during the precleaning phase 1593 // to "carefully" rescan marked objects on dirty cards. 1594 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1595 // to accomplish some of its work. 1596 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1597 CMSCollector* _collector; 1598 MemRegion _span; 1599 bool _yield; 1600 Mutex* _freelistLock; 1601 CMSBitMap* _bitMap; 1602 CMSMarkStack* _markStack; 1603 MarkRefsIntoAndScanClosure* _scanningClosure; 1604 1605 public: 1606 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1607 MemRegion span, 1608 CMSBitMap* bitMap, 1609 CMSMarkStack* markStack, 1610 MarkRefsIntoAndScanClosure* cl, 1611 bool should_yield): 1612 _collector(collector), 1613 _span(span), 1614 _yield(should_yield), 1615 _bitMap(bitMap), 1616 _markStack(markStack), 1617 _scanningClosure(cl) { 1618 } 1619 1620 void do_object(oop p) { 1621 guarantee(false, "call do_object_careful instead"); 1622 } 1623 1624 size_t do_object_careful(oop p) { 1625 guarantee(false, "Unexpected caller"); 1626 return 0; 1627 } 1628 1629 size_t do_object_careful_m(oop p, MemRegion mr); 1630 1631 void setFreelistLock(Mutex* m) { 1632 _freelistLock = m; 1633 _scanningClosure->set_freelistLock(m); 1634 } 1635 1636 private: 1637 inline bool do_yield_check(); 1638 1639 void do_yield_work(); 1640 }; 1641 1642 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1643 CMSCollector* _collector; 1644 MemRegion _span; 1645 bool _yield; 1646 CMSBitMap* _bit_map; 1647 CMSMarkStack* _mark_stack; 1648 PushAndMarkClosure* _scanning_closure; 1649 unsigned int _before_count; 1650 1651 public: 1652 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1653 MemRegion span, 1654 CMSBitMap* bit_map, 1655 CMSMarkStack* mark_stack, 1656 PushAndMarkClosure* cl, 1657 unsigned int before_count, 1658 bool should_yield): 1659 _collector(collector), 1660 _span(span), 1661 _yield(should_yield), 1662 _bit_map(bit_map), 1663 _mark_stack(mark_stack), 1664 _scanning_closure(cl), 1665 _before_count(before_count) 1666 { } 1667 1668 void do_object(oop p) { 1669 guarantee(false, "call do_object_careful instead"); 1670 } 1671 1672 size_t do_object_careful(oop p); 1673 1674 size_t do_object_careful_m(oop p, MemRegion mr) { 1675 guarantee(false, "Unexpected caller"); 1676 return 0; 1677 } 1678 1679 private: 1680 inline void do_yield_check(); 1681 void do_yield_work(); 1682 }; 1683 1684 // This closure is used to accomplish the sweeping work 1685 // after the second checkpoint but before the concurrent reset 1686 // phase. 1687 // 1688 // Terminology 1689 // left hand chunk (LHC) - block of one or more chunks currently being 1690 // coalesced. The LHC is available for coalescing with a new chunk. 1691 // right hand chunk (RHC) - block that is currently being swept that is 1692 // free or garbage that can be coalesced with the LHC. 1693 // _inFreeRange is true if there is currently a LHC 1694 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1695 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1696 // _freeFinger is the address of the current LHC 1697 class SweepClosure: public BlkClosureCareful { 1698 CMSCollector* _collector; // collector doing the work 1699 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1700 CompactibleFreeListSpace* _sp; // Space being swept 1701 HeapWord* _limit;// the address at or above which the sweep should stop 1702 // because we do not expect newly garbage blocks 1703 // eligible for sweeping past that address. 1704 Mutex* _freelistLock; // Free list lock (in space) 1705 CMSBitMap* _bitMap; // Marking bit map (in 1706 // generation) 1707 bool _inFreeRange; // Indicates if we are in the 1708 // midst of a free run 1709 bool _freeRangeInFreeLists; 1710 // Often, we have just found 1711 // a free chunk and started 1712 // a new free range; we do not 1713 // eagerly remove this chunk from 1714 // the free lists unless there is 1715 // a possibility of coalescing. 1716 // When true, this flag indicates 1717 // that the _freeFinger below 1718 // points to a potentially free chunk 1719 // that may still be in the free lists 1720 bool _lastFreeRangeCoalesced; 1721 // free range contains chunks 1722 // coalesced 1723 bool _yield; 1724 // Whether sweeping should be 1725 // done with yields. For instance 1726 // when done by the foreground 1727 // collector we shouldn't yield. 1728 HeapWord* _freeFinger; // When _inFreeRange is set, the 1729 // pointer to the "left hand 1730 // chunk" 1731 size_t _freeRangeSize; 1732 // When _inFreeRange is set, this 1733 // indicates the accumulated size 1734 // of the "left hand chunk" 1735 NOT_PRODUCT( 1736 size_t _numObjectsFreed; 1737 size_t _numWordsFreed; 1738 size_t _numObjectsLive; 1739 size_t _numWordsLive; 1740 size_t _numObjectsAlreadyFree; 1741 size_t _numWordsAlreadyFree; 1742 FreeChunk* _last_fc; 1743 ) 1744 private: 1745 // Code that is common to a free chunk or garbage when 1746 // encountered during sweeping. 1747 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1748 // Process a free chunk during sweeping. 1749 void do_already_free_chunk(FreeChunk *fc); 1750 // Work method called when processing an already free or a 1751 // freshly garbage chunk to do a lookahead and possibly a 1752 // preemptive flush if crossing over _limit. 1753 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1754 // Process a garbage chunk during sweeping. 1755 size_t do_garbage_chunk(FreeChunk *fc); 1756 // Process a live chunk during sweeping. 1757 size_t do_live_chunk(FreeChunk* fc); 1758 1759 // Accessors. 1760 HeapWord* freeFinger() const { return _freeFinger; } 1761 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1762 bool inFreeRange() const { return _inFreeRange; } 1763 void set_inFreeRange(bool v) { _inFreeRange = v; } 1764 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1765 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1766 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1767 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1768 1769 // Initialize a free range. 1770 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1771 // Return this chunk to the free lists. 1772 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1773 1774 // Check if we should yield and do so when necessary. 1775 inline void do_yield_check(HeapWord* addr); 1776 1777 // Yield 1778 void do_yield_work(HeapWord* addr); 1779 1780 // Debugging/Printing 1781 void print_free_block_coalesced(FreeChunk* fc) const; 1782 1783 public: 1784 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1785 CMSBitMap* bitMap, bool should_yield); 1786 ~SweepClosure() PRODUCT_RETURN; 1787 1788 size_t do_blk_careful(HeapWord* addr); 1789 void print() const { print_on(tty); } 1790 void print_on(outputStream *st) const; 1791 }; 1792 1793 // Closures related to weak references processing 1794 1795 // During CMS' weak reference processing, this is a 1796 // work-routine/closure used to complete transitive 1797 // marking of objects as live after a certain point 1798 // in which an initial set has been completely accumulated. 1799 // This closure is currently used both during the final 1800 // remark stop-world phase, as well as during the concurrent 1801 // precleaning of the discovered reference lists. 1802 class CMSDrainMarkingStackClosure: public VoidClosure { 1803 CMSCollector* _collector; 1804 MemRegion _span; 1805 CMSMarkStack* _mark_stack; 1806 CMSBitMap* _bit_map; 1807 CMSKeepAliveClosure* _keep_alive; 1808 bool _concurrent_precleaning; 1809 public: 1810 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1811 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1812 CMSKeepAliveClosure* keep_alive, 1813 bool cpc): 1814 _collector(collector), 1815 _span(span), 1816 _bit_map(bit_map), 1817 _mark_stack(mark_stack), 1818 _keep_alive(keep_alive), 1819 _concurrent_precleaning(cpc) { 1820 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1821 "Mismatch"); 1822 } 1823 1824 void do_void(); 1825 }; 1826 1827 // A parallel version of CMSDrainMarkingStackClosure above. 1828 class CMSParDrainMarkingStackClosure: public VoidClosure { 1829 CMSCollector* _collector; 1830 MemRegion _span; 1831 OopTaskQueue* _work_queue; 1832 CMSBitMap* _bit_map; 1833 CMSInnerParMarkAndPushClosure _mark_and_push; 1834 1835 public: 1836 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1837 MemRegion span, CMSBitMap* bit_map, 1838 OopTaskQueue* work_queue): 1839 _collector(collector), 1840 _span(span), 1841 _bit_map(bit_map), 1842 _work_queue(work_queue), 1843 _mark_and_push(collector, span, bit_map, work_queue) { } 1844 1845 public: 1846 void trim_queue(uint max); 1847 void do_void(); 1848 }; 1849 1850 // Allow yielding or short-circuiting of reference list 1851 // precleaning work. 1852 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1853 CMSCollector* _collector; 1854 void do_yield_work(); 1855 public: 1856 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1857 _collector(collector) {} 1858 virtual bool should_return(); 1859 }; 1860 1861 1862 // Convenience class that locks free list locks for given CMS collector 1863 class FreelistLocker: public StackObj { 1864 private: 1865 CMSCollector* _collector; 1866 public: 1867 FreelistLocker(CMSCollector* collector): 1868 _collector(collector) { 1869 _collector->getFreelistLocks(); 1870 } 1871 1872 ~FreelistLocker() { 1873 _collector->releaseFreelistLocks(); 1874 } 1875 }; 1876 1877 // Mark all dead objects in a given space. 1878 class MarkDeadObjectsClosure: public BlkClosure { 1879 const CMSCollector* _collector; 1880 const CompactibleFreeListSpace* _sp; 1881 CMSBitMap* _live_bit_map; 1882 CMSBitMap* _dead_bit_map; 1883 public: 1884 MarkDeadObjectsClosure(const CMSCollector* collector, 1885 const CompactibleFreeListSpace* sp, 1886 CMSBitMap *live_bit_map, 1887 CMSBitMap *dead_bit_map) : 1888 _collector(collector), 1889 _sp(sp), 1890 _live_bit_map(live_bit_map), 1891 _dead_bit_map(dead_bit_map) {} 1892 size_t do_blk(HeapWord* addr); 1893 }; 1894 1895 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1896 1897 public: 1898 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1899 }; 1900 1901 1902 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP