1 /* 2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP 27 28 #include "gc_implementation/shared/gcHeapSummary.hpp" 29 #include "gc_implementation/shared/gSpaceCounters.hpp" 30 #include "gc_implementation/shared/gcStats.hpp" 31 #include "gc_implementation/shared/gcWhen.hpp" 32 #include "gc_implementation/shared/generationCounters.hpp" 33 #include "memory/freeBlockDictionary.hpp" 34 #include "memory/generation.hpp" 35 #include "runtime/mutexLocker.hpp" 36 #include "runtime/virtualspace.hpp" 37 #include "services/memoryService.hpp" 38 #include "utilities/bitMap.inline.hpp" 39 #include "utilities/stack.inline.hpp" 40 #include "utilities/taskqueue.hpp" 41 #include "utilities/yieldingWorkgroup.hpp" 42 43 // ConcurrentMarkSweepGeneration is in support of a concurrent 44 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker 45 // style. We assume, for now, that this generation is always the 46 // seniormost generation and for simplicity 47 // in the first implementation, that this generation is a single compactible 48 // space. Neither of these restrictions appears essential, and will be 49 // relaxed in the future when more time is available to implement the 50 // greater generality (and there's a need for it). 51 // 52 // Concurrent mode failures are currently handled by 53 // means of a sliding mark-compact. 54 55 class CMSAdaptiveSizePolicy; 56 class CMSConcMarkingTask; 57 class CMSGCAdaptivePolicyCounters; 58 class CMSTracer; 59 class ConcurrentGCTimer; 60 class ConcurrentMarkSweepGeneration; 61 class ConcurrentMarkSweepPolicy; 62 class ConcurrentMarkSweepThread; 63 class CompactibleFreeListSpace; 64 class FreeChunk; 65 class PromotionInfo; 66 class ScanMarkedObjectsAgainCarefullyClosure; 67 class TenuredGeneration; 68 class SerialOldTracer; 69 70 // A generic CMS bit map. It's the basis for both the CMS marking bit map 71 // as well as for the mod union table (in each case only a subset of the 72 // methods are used). This is essentially a wrapper around the BitMap class, 73 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 74 // we have _shifter == 0. and for the mod union table we have 75 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 76 // XXX 64-bit issues in BitMap? 77 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 78 friend class VMStructs; 79 80 HeapWord* _bmStartWord; // base address of range covered by map 81 size_t _bmWordSize; // map size (in #HeapWords covered) 82 const int _shifter; // shifts to convert HeapWord to bit position 83 VirtualSpace _virtual_space; // underlying the bit map 84 BitMap _bm; // the bit map itself 85 public: 86 Mutex* const _lock; // mutex protecting _bm; 87 88 public: 89 // constructor 90 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 91 92 // allocates the actual storage for the map 93 bool allocate(MemRegion mr); 94 // field getter 95 Mutex* lock() const { return _lock; } 96 // locking verifier convenience function 97 void assert_locked() const PRODUCT_RETURN; 98 99 // inquiries 100 HeapWord* startWord() const { return _bmStartWord; } 101 size_t sizeInWords() const { return _bmWordSize; } 102 size_t sizeInBits() const { return _bm.size(); } 103 // the following is one past the last word in space 104 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 105 106 // reading marks 107 bool isMarked(HeapWord* addr) const; 108 bool par_isMarked(HeapWord* addr) const; // do not lock checks 109 bool isUnmarked(HeapWord* addr) const; 110 bool isAllClear() const; 111 112 // writing marks 113 void mark(HeapWord* addr); 114 // For marking by parallel GC threads; 115 // returns true if we did, false if another thread did 116 bool par_mark(HeapWord* addr); 117 118 void mark_range(MemRegion mr); 119 void par_mark_range(MemRegion mr); 120 void mark_large_range(MemRegion mr); 121 void par_mark_large_range(MemRegion mr); 122 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 123 void clear_range(MemRegion mr); 124 void par_clear_range(MemRegion mr); 125 void clear_large_range(MemRegion mr); 126 void par_clear_large_range(MemRegion mr); 127 void clear_all(); 128 void clear_all_incrementally(); // Not yet implemented!! 129 130 NOT_PRODUCT( 131 // checks the memory region for validity 132 void region_invariant(MemRegion mr); 133 ) 134 135 // iteration 136 void iterate(BitMapClosure* cl) { 137 _bm.iterate(cl); 138 } 139 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 140 void dirty_range_iterate_clear(MemRegionClosure* cl); 141 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 142 143 // auxiliary support for iteration 144 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 145 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 146 HeapWord* end_addr) const; 147 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 148 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 149 HeapWord* end_addr) const; 150 MemRegion getAndClearMarkedRegion(HeapWord* addr); 151 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 152 HeapWord* end_addr); 153 154 // conversion utilities 155 HeapWord* offsetToHeapWord(size_t offset) const; 156 size_t heapWordToOffset(HeapWord* addr) const; 157 size_t heapWordDiffToOffsetDiff(size_t diff) const; 158 159 void print_on_error(outputStream* st, const char* prefix) const; 160 161 // debugging 162 // is this address range covered by the bit-map? 163 NOT_PRODUCT( 164 bool covers(MemRegion mr) const; 165 bool covers(HeapWord* start, size_t size = 0) const; 166 ) 167 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 168 }; 169 170 // Represents a marking stack used by the CMS collector. 171 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 172 class CMSMarkStack: public CHeapObj<mtGC> { 173 // 174 friend class CMSCollector; // to get at expasion stats further below 175 // 176 177 VirtualSpace _virtual_space; // space for the stack 178 oop* _base; // bottom of stack 179 size_t _index; // one more than last occupied index 180 size_t _capacity; // max #elements 181 Mutex _par_lock; // an advisory lock used in case of parallel access 182 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run 183 184 protected: 185 size_t _hit_limit; // we hit max stack size limit 186 size_t _failed_double; // we failed expansion before hitting limit 187 188 public: 189 CMSMarkStack(): 190 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true), 191 _hit_limit(0), 192 _failed_double(0) {} 193 194 bool allocate(size_t size); 195 196 size_t capacity() const { return _capacity; } 197 198 oop pop() { 199 if (!isEmpty()) { 200 return _base[--_index] ; 201 } 202 return NULL; 203 } 204 205 bool push(oop ptr) { 206 if (isFull()) { 207 return false; 208 } else { 209 _base[_index++] = ptr; 210 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 211 return true; 212 } 213 } 214 215 bool isEmpty() const { return _index == 0; } 216 bool isFull() const { 217 assert(_index <= _capacity, "buffer overflow"); 218 return _index == _capacity; 219 } 220 221 size_t length() { return _index; } 222 223 // "Parallel versions" of some of the above 224 oop par_pop() { 225 // lock and pop 226 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 227 return pop(); 228 } 229 230 bool par_push(oop ptr) { 231 // lock and push 232 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 233 return push(ptr); 234 } 235 236 // Forcibly reset the stack, losing all of its contents. 237 void reset() { 238 _index = 0; 239 } 240 241 // Expand the stack, typically in response to an overflow condition 242 void expand(); 243 244 // Compute the least valued stack element. 245 oop least_value(HeapWord* low) { 246 oop least = (oop)low; 247 for (size_t i = 0; i < _index; i++) { 248 least = MIN2(least, _base[i]); 249 } 250 return least; 251 } 252 253 // Exposed here to allow stack expansion in || case 254 Mutex* par_lock() { return &_par_lock; } 255 }; 256 257 class CardTableRS; 258 class CMSParGCThreadState; 259 260 class ModUnionClosure: public MemRegionClosure { 261 protected: 262 CMSBitMap* _t; 263 public: 264 ModUnionClosure(CMSBitMap* t): _t(t) { } 265 void do_MemRegion(MemRegion mr); 266 }; 267 268 class ModUnionClosurePar: public ModUnionClosure { 269 public: 270 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 271 void do_MemRegion(MemRegion mr); 272 }; 273 274 // Survivor Chunk Array in support of parallelization of 275 // Survivor Space rescan. 276 class ChunkArray: public CHeapObj<mtGC> { 277 size_t _index; 278 size_t _capacity; 279 size_t _overflows; 280 HeapWord** _array; // storage for array 281 282 public: 283 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 284 ChunkArray(HeapWord** a, size_t c): 285 _index(0), _capacity(c), _overflows(0), _array(a) {} 286 287 HeapWord** array() { return _array; } 288 void set_array(HeapWord** a) { _array = a; } 289 290 size_t capacity() { return _capacity; } 291 void set_capacity(size_t c) { _capacity = c; } 292 293 size_t end() { 294 assert(_index <= capacity(), 295 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 296 _index, _capacity)); 297 return _index; 298 } // exclusive 299 300 HeapWord* nth(size_t n) { 301 assert(n < end(), "Out of bounds access"); 302 return _array[n]; 303 } 304 305 void reset() { 306 _index = 0; 307 if (_overflows > 0 && PrintCMSStatistics > 1) { 308 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", 309 _capacity, _overflows); 310 } 311 _overflows = 0; 312 } 313 314 void record_sample(HeapWord* p, size_t sz) { 315 // For now we do not do anything with the size 316 if (_index < _capacity) { 317 _array[_index++] = p; 318 } else { 319 ++_overflows; 320 assert(_index == _capacity, 321 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 322 "): out of bounds at overflow#" SIZE_FORMAT, 323 _index, _capacity, _overflows)); 324 } 325 } 326 }; 327 328 // 329 // Timing, allocation and promotion statistics for gc scheduling and incremental 330 // mode pacing. Most statistics are exponential averages. 331 // 332 class CMSStats VALUE_OBJ_CLASS_SPEC { 333 private: 334 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 335 336 // The following are exponential averages with factor alpha: 337 // avg = (100 - alpha) * avg + alpha * cur_sample 338 // 339 // The durations measure: end_time[n] - start_time[n] 340 // The periods measure: start_time[n] - start_time[n-1] 341 // 342 // The cms period and duration include only concurrent collections; time spent 343 // in foreground cms collections due to System.gc() or because of a failure to 344 // keep up are not included. 345 // 346 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 347 // real value, but is used only after the first period. A value of 100 is 348 // used for the first sample so it gets the entire weight. 349 unsigned int _saved_alpha; // 0-100 350 unsigned int _gc0_alpha; 351 unsigned int _cms_alpha; 352 353 double _gc0_duration; 354 double _gc0_period; 355 size_t _gc0_promoted; // bytes promoted per gc0 356 double _cms_duration; 357 double _cms_duration_pre_sweep; // time from initiation to start of sweep 358 double _cms_duration_per_mb; 359 double _cms_period; 360 size_t _cms_allocated; // bytes of direct allocation per gc0 period 361 362 // Timers. 363 elapsedTimer _cms_timer; 364 TimeStamp _gc0_begin_time; 365 TimeStamp _cms_begin_time; 366 TimeStamp _cms_end_time; 367 368 // Snapshots of the amount used in the CMS generation. 369 size_t _cms_used_at_gc0_begin; 370 size_t _cms_used_at_gc0_end; 371 size_t _cms_used_at_cms_begin; 372 373 // Used to prevent the duty cycle from being reduced in the middle of a cms 374 // cycle. 375 bool _allow_duty_cycle_reduction; 376 377 enum { 378 _GC0_VALID = 0x1, 379 _CMS_VALID = 0x2, 380 _ALL_VALID = _GC0_VALID | _CMS_VALID 381 }; 382 383 unsigned int _valid_bits; 384 385 unsigned int _icms_duty_cycle; // icms duty cycle (0-100). 386 387 protected: 388 389 // Return a duty cycle that avoids wild oscillations, by limiting the amount 390 // of change between old_duty_cycle and new_duty_cycle (the latter is treated 391 // as a recommended value). 392 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle, 393 unsigned int new_duty_cycle); 394 unsigned int icms_update_duty_cycle_impl(); 395 396 // In support of adjusting of cms trigger ratios based on history 397 // of concurrent mode failure. 398 double cms_free_adjustment_factor(size_t free) const; 399 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 400 401 public: 402 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 403 unsigned int alpha = CMSExpAvgFactor); 404 405 // Whether or not the statistics contain valid data; higher level statistics 406 // cannot be called until this returns true (they require at least one young 407 // gen and one cms cycle to have completed). 408 bool valid() const; 409 410 // Record statistics. 411 void record_gc0_begin(); 412 void record_gc0_end(size_t cms_gen_bytes_used); 413 void record_cms_begin(); 414 void record_cms_end(); 415 416 // Allow management of the cms timer, which must be stopped/started around 417 // yield points. 418 elapsedTimer& cms_timer() { return _cms_timer; } 419 void start_cms_timer() { _cms_timer.start(); } 420 void stop_cms_timer() { _cms_timer.stop(); } 421 422 // Basic statistics; units are seconds or bytes. 423 double gc0_period() const { return _gc0_period; } 424 double gc0_duration() const { return _gc0_duration; } 425 size_t gc0_promoted() const { return _gc0_promoted; } 426 double cms_period() const { return _cms_period; } 427 double cms_duration() const { return _cms_duration; } 428 double cms_duration_per_mb() const { return _cms_duration_per_mb; } 429 size_t cms_allocated() const { return _cms_allocated; } 430 431 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 432 433 // Seconds since the last background cms cycle began or ended. 434 double cms_time_since_begin() const; 435 double cms_time_since_end() const; 436 437 // Higher level statistics--caller must check that valid() returns true before 438 // calling. 439 440 // Returns bytes promoted per second of wall clock time. 441 double promotion_rate() const; 442 443 // Returns bytes directly allocated per second of wall clock time. 444 double cms_allocation_rate() const; 445 446 // Rate at which space in the cms generation is being consumed (sum of the 447 // above two). 448 double cms_consumption_rate() const; 449 450 // Returns an estimate of the number of seconds until the cms generation will 451 // fill up, assuming no collection work is done. 452 double time_until_cms_gen_full() const; 453 454 // Returns an estimate of the number of seconds remaining until 455 // the cms generation collection should start. 456 double time_until_cms_start() const; 457 458 // End of higher level statistics. 459 460 // Returns the cms incremental mode duty cycle, as a percentage (0-100). 461 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; } 462 463 // Update the duty cycle and return the new value. 464 unsigned int icms_update_duty_cycle(); 465 466 // Debugging. 467 void print_on(outputStream* st) const PRODUCT_RETURN; 468 void print() const { print_on(gclog_or_tty); } 469 }; 470 471 // A closure related to weak references processing which 472 // we embed in the CMSCollector, since we need to pass 473 // it to the reference processor for secondary filtering 474 // of references based on reachability of referent; 475 // see role of _is_alive_non_header closure in the 476 // ReferenceProcessor class. 477 // For objects in the CMS generation, this closure checks 478 // if the object is "live" (reachable). Used in weak 479 // reference processing. 480 class CMSIsAliveClosure: public BoolObjectClosure { 481 const MemRegion _span; 482 const CMSBitMap* _bit_map; 483 484 friend class CMSCollector; 485 public: 486 CMSIsAliveClosure(MemRegion span, 487 CMSBitMap* bit_map): 488 _span(span), 489 _bit_map(bit_map) { 490 assert(!span.is_empty(), "Empty span could spell trouble"); 491 } 492 493 bool do_object_b(oop obj); 494 }; 495 496 497 // Implements AbstractRefProcTaskExecutor for CMS. 498 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 499 public: 500 501 CMSRefProcTaskExecutor(CMSCollector& collector) 502 : _collector(collector) 503 { } 504 505 // Executes a task using worker threads. 506 virtual void execute(ProcessTask& task); 507 virtual void execute(EnqueueTask& task); 508 private: 509 CMSCollector& _collector; 510 }; 511 512 513 class CMSCollector: public CHeapObj<mtGC> { 514 friend class VMStructs; 515 friend class ConcurrentMarkSweepThread; 516 friend class ConcurrentMarkSweepGeneration; 517 friend class CompactibleFreeListSpace; 518 friend class CMSParRemarkTask; 519 friend class CMSConcMarkingTask; 520 friend class CMSRefProcTaskProxy; 521 friend class CMSRefProcTaskExecutor; 522 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 523 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 524 friend class PushOrMarkClosure; // to access _restart_addr 525 friend class Par_PushOrMarkClosure; // to access _restart_addr 526 friend class MarkFromRootsClosure; // -- ditto -- 527 // ... and for clearing cards 528 friend class Par_MarkFromRootsClosure; // to access _restart_addr 529 // ... and for clearing cards 530 friend class Par_ConcMarkingClosure; // to access _restart_addr etc. 531 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 532 friend class PushAndMarkVerifyClosure; // -- ditto -- 533 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 534 friend class PushAndMarkClosure; // -- ditto -- 535 friend class Par_PushAndMarkClosure; // -- ditto -- 536 friend class CMSKeepAliveClosure; // -- ditto -- 537 friend class CMSDrainMarkingStackClosure; // -- ditto -- 538 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 539 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 540 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 541 friend class VM_CMS_Operation; 542 friend class VM_CMS_Initial_Mark; 543 friend class VM_CMS_Final_Remark; 544 friend class TraceCMSMemoryManagerStats; 545 546 private: 547 jlong _time_of_last_gc; 548 void update_time_of_last_gc(jlong now) { 549 _time_of_last_gc = now; 550 } 551 552 OopTaskQueueSet* _task_queues; 553 554 // Overflow list of grey objects, threaded through mark-word 555 // Manipulated with CAS in the parallel/multi-threaded case. 556 oop _overflow_list; 557 // The following array-pair keeps track of mark words 558 // displaced for accomodating overflow list above. 559 // This code will likely be revisited under RFE#4922830. 560 Stack<oop, mtGC> _preserved_oop_stack; 561 Stack<markOop, mtGC> _preserved_mark_stack; 562 563 int* _hash_seed; 564 565 // In support of multi-threaded concurrent phases 566 YieldingFlexibleWorkGang* _conc_workers; 567 568 // Performance Counters 569 CollectorCounters* _gc_counters; 570 571 // Initialization Errors 572 bool _completed_initialization; 573 574 // In support of ExplicitGCInvokesConcurrent 575 static bool _full_gc_requested; 576 static GCCause::Cause _full_gc_cause; 577 unsigned int _collection_count_start; 578 579 // Should we unload classes this concurrent cycle? 580 bool _should_unload_classes; 581 unsigned int _concurrent_cycles_since_last_unload; 582 unsigned int concurrent_cycles_since_last_unload() const { 583 return _concurrent_cycles_since_last_unload; 584 } 585 // Did we (allow) unload classes in the previous concurrent cycle? 586 bool unloaded_classes_last_cycle() const { 587 return concurrent_cycles_since_last_unload() == 0; 588 } 589 // Root scanning options for perm gen 590 int _roots_scanning_options; 591 int roots_scanning_options() const { return _roots_scanning_options; } 592 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 593 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 594 595 // Verification support 596 CMSBitMap _verification_mark_bm; 597 void verify_after_remark_work_1(); 598 void verify_after_remark_work_2(); 599 600 // true if any verification flag is on. 601 bool _verifying; 602 bool verifying() const { return _verifying; } 603 void set_verifying(bool v) { _verifying = v; } 604 605 // Collector policy 606 ConcurrentMarkSweepPolicy* _collector_policy; 607 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 608 609 void set_did_compact(bool v); 610 611 // XXX Move these to CMSStats ??? FIX ME !!! 612 elapsedTimer _inter_sweep_timer; // time between sweeps 613 elapsedTimer _intra_sweep_timer; // time _in_ sweeps 614 // padded decaying average estimates of the above 615 AdaptivePaddedAverage _inter_sweep_estimate; 616 AdaptivePaddedAverage _intra_sweep_estimate; 617 618 CMSTracer* _gc_tracer_cm; 619 ConcurrentGCTimer* _gc_timer_cm; 620 621 bool _cms_start_registered; 622 623 GCHeapSummary _last_heap_summary; 624 MetaspaceSummary _last_metaspace_summary; 625 626 void register_foreground_gc_start(GCCause::Cause cause); 627 void register_gc_start(GCCause::Cause cause); 628 void register_gc_end(); 629 void save_heap_summary(); 630 void report_heap_summary(GCWhen::Type when); 631 632 protected: 633 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS) 634 MemRegion _span; // span covering above two 635 CardTableRS* _ct; // card table 636 637 // CMS marking support structures 638 CMSBitMap _markBitMap; 639 CMSBitMap _modUnionTable; 640 CMSMarkStack _markStack; 641 642 HeapWord* _restart_addr; // in support of marking stack overflow 643 void lower_restart_addr(HeapWord* low); 644 645 // Counters in support of marking stack / work queue overflow handling: 646 // a non-zero value indicates certain types of overflow events during 647 // the current CMS cycle and could lead to stack resizing efforts at 648 // an opportune future time. 649 size_t _ser_pmc_preclean_ovflw; 650 size_t _ser_pmc_remark_ovflw; 651 size_t _par_pmc_remark_ovflw; 652 size_t _ser_kac_preclean_ovflw; 653 size_t _ser_kac_ovflw; 654 size_t _par_kac_ovflw; 655 NOT_PRODUCT(ssize_t _num_par_pushes;) 656 657 // ("Weak") Reference processing support 658 ReferenceProcessor* _ref_processor; 659 CMSIsAliveClosure _is_alive_closure; 660 // keep this textually after _markBitMap and _span; c'tor dependency 661 662 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work 663 ModUnionClosure _modUnionClosure; 664 ModUnionClosurePar _modUnionClosurePar; 665 666 // CMS abstract state machine 667 // initial_state: Idling 668 // next_state(Idling) = {Marking} 669 // next_state(Marking) = {Precleaning, Sweeping} 670 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 671 // next_state(AbortablePreclean) = {FinalMarking} 672 // next_state(FinalMarking) = {Sweeping} 673 // next_state(Sweeping) = {Resizing} 674 // next_state(Resizing) = {Resetting} 675 // next_state(Resetting) = {Idling} 676 // The numeric values below are chosen so that: 677 // . _collectorState <= Idling == post-sweep && pre-mark 678 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 679 // precleaning || abortablePrecleanb 680 public: 681 enum CollectorState { 682 Resizing = 0, 683 Resetting = 1, 684 Idling = 2, 685 InitialMarking = 3, 686 Marking = 4, 687 Precleaning = 5, 688 AbortablePreclean = 6, 689 FinalMarking = 7, 690 Sweeping = 8 691 }; 692 protected: 693 static CollectorState _collectorState; 694 695 // State related to prologue/epilogue invocation for my generations 696 bool _between_prologue_and_epilogue; 697 698 // Signalling/State related to coordination between fore- and backgroud GC 699 // Note: When the baton has been passed from background GC to foreground GC, 700 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 701 static bool _foregroundGCIsActive; // true iff foreground collector is active or 702 // wants to go active 703 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 704 // yet passed the baton to the foreground GC 705 706 // Support for CMSScheduleRemark (abortable preclean) 707 bool _abort_preclean; 708 bool _start_sampling; 709 710 int _numYields; 711 size_t _numDirtyCards; 712 size_t _sweep_count; 713 // number of full gc's since the last concurrent gc. 714 uint _full_gcs_since_conc_gc; 715 716 // occupancy used for bootstrapping stats 717 double _bootstrap_occupancy; 718 719 // timer 720 elapsedTimer _timer; 721 722 // Timing, allocation and promotion statistics, used for scheduling. 723 CMSStats _stats; 724 725 // Allocation limits installed in the young gen, used only in 726 // CMSIncrementalMode. When an allocation in the young gen would cross one of 727 // these limits, the cms generation is notified and the cms thread is started 728 // or stopped, respectively. 729 HeapWord* _icms_start_limit; 730 HeapWord* _icms_stop_limit; 731 732 enum CMS_op_type { 733 CMS_op_checkpointRootsInitial, 734 CMS_op_checkpointRootsFinal 735 }; 736 737 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 738 bool stop_world_and_do(CMS_op_type op); 739 740 OopTaskQueueSet* task_queues() { return _task_queues; } 741 int* hash_seed(int i) { return &_hash_seed[i]; } 742 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 743 744 // Support for parallelizing Eden rescan in CMS remark phase 745 void sample_eden(); // ... sample Eden space top 746 747 private: 748 // Support for parallelizing young gen rescan in CMS remark phase 749 Generation* _young_gen; // the younger gen 750 HeapWord** _top_addr; // ... Top of Eden 751 HeapWord** _end_addr; // ... End of Eden 752 HeapWord** _eden_chunk_array; // ... Eden partitioning array 753 size_t _eden_chunk_index; // ... top (exclusive) of array 754 size_t _eden_chunk_capacity; // ... max entries in array 755 756 // Support for parallelizing survivor space rescan 757 HeapWord** _survivor_chunk_array; 758 size_t _survivor_chunk_index; 759 size_t _survivor_chunk_capacity; 760 size_t* _cursor; 761 ChunkArray* _survivor_plab_array; 762 763 // Support for marking stack overflow handling 764 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 765 bool par_take_from_overflow_list(size_t num, 766 OopTaskQueue* to_work_q, 767 int no_of_gc_threads); 768 void push_on_overflow_list(oop p); 769 void par_push_on_overflow_list(oop p); 770 // the following is, obviously, not, in general, "MT-stable" 771 bool overflow_list_is_empty() const; 772 773 void preserve_mark_if_necessary(oop p); 774 void par_preserve_mark_if_necessary(oop p); 775 void preserve_mark_work(oop p, markOop m); 776 void restore_preserved_marks_if_any(); 777 NOT_PRODUCT(bool no_preserved_marks() const;) 778 // in support of testing overflow code 779 NOT_PRODUCT(int _overflow_counter;) 780 NOT_PRODUCT(bool simulate_overflow();) // sequential 781 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 782 783 // CMS work methods 784 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work 785 786 // a return value of false indicates failure due to stack overflow 787 bool markFromRootsWork(bool asynch); // concurrent marking work 788 789 public: // FIX ME!!! only for testing 790 bool do_marking_st(bool asynch); // single-threaded marking 791 bool do_marking_mt(bool asynch); // multi-threaded marking 792 793 private: 794 795 // concurrent precleaning work 796 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, 797 ScanMarkedObjectsAgainCarefullyClosure* cl); 798 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, 799 ScanMarkedObjectsAgainCarefullyClosure* cl); 800 // Does precleaning work, returning a quantity indicative of 801 // the amount of "useful work" done. 802 size_t preclean_work(bool clean_refs, bool clean_survivors); 803 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 804 void abortable_preclean(); // Preclean while looking for possible abort 805 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 806 // Helper function for above; merge-sorts the per-thread plab samples 807 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 808 // Resets (i.e. clears) the per-thread plab sample vectors 809 void reset_survivor_plab_arrays(); 810 811 // final (second) checkpoint work 812 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs, 813 bool init_mark_was_synchronous); 814 // work routine for parallel version of remark 815 void do_remark_parallel(); 816 // work routine for non-parallel version of remark 817 void do_remark_non_parallel(); 818 // reference processing work routine (during second checkpoint) 819 void refProcessingWork(bool asynch, bool clear_all_soft_refs); 820 821 // concurrent sweeping work 822 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch); 823 824 // (concurrent) resetting of support data structures 825 void reset(bool asynch); 826 827 // Clear _expansion_cause fields of constituent generations 828 void clear_expansion_cause(); 829 830 // An auxilliary method used to record the ends of 831 // used regions of each generation to limit the extent of sweep 832 void save_sweep_limits(); 833 834 // A work method used by foreground collection to determine 835 // what type of collection (compacting or not, continuing or fresh) 836 // it should do. 837 void decide_foreground_collection_type(bool clear_all_soft_refs, 838 bool* should_compact, bool* should_start_over); 839 840 // A work method used by the foreground collector to do 841 // a mark-sweep-compact. 842 void do_compaction_work(bool clear_all_soft_refs); 843 844 // A work method used by the foreground collector to do 845 // a mark-sweep, after taking over from a possibly on-going 846 // concurrent mark-sweep collection. 847 void do_mark_sweep_work(bool clear_all_soft_refs, 848 CollectorState first_state, bool should_start_over); 849 850 // Work methods for reporting concurrent mode interruption or failure 851 bool is_external_interruption(); 852 void report_concurrent_mode_interruption(); 853 854 // If the backgrould GC is active, acquire control from the background 855 // GC and do the collection. 856 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 857 858 // For synchronizing passing of control from background to foreground 859 // GC. waitForForegroundGC() is called by the background 860 // collector. It if had to wait for a foreground collection, 861 // it returns true and the background collection should assume 862 // that the collection was finished by the foreground 863 // collector. 864 bool waitForForegroundGC(); 865 866 // Incremental mode triggering: recompute the icms duty cycle and set the 867 // allocation limits in the young gen. 868 void icms_update_allocation_limits(); 869 870 size_t block_size_using_printezis_bits(HeapWord* addr) const; 871 size_t block_size_if_printezis_bits(HeapWord* addr) const; 872 HeapWord* next_card_start_after_block(HeapWord* addr) const; 873 874 void setup_cms_unloading_and_verification_state(); 875 public: 876 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 877 CardTableRS* ct, 878 ConcurrentMarkSweepPolicy* cp); 879 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 880 881 ReferenceProcessor* ref_processor() { return _ref_processor; } 882 void ref_processor_init(); 883 884 Mutex* bitMapLock() const { return _markBitMap.lock(); } 885 static CollectorState abstract_state() { return _collectorState; } 886 887 bool should_abort_preclean() const; // Whether preclean should be aborted. 888 size_t get_eden_used() const; 889 size_t get_eden_capacity() const; 890 891 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 892 893 // locking checks 894 NOT_PRODUCT(static bool have_cms_token();) 895 896 // XXXPERM bool should_collect(bool full, size_t size, bool tlab); 897 bool shouldConcurrentCollect(); 898 899 void collect(bool full, 900 bool clear_all_soft_refs, 901 size_t size, 902 bool tlab); 903 void collect_in_background(bool clear_all_soft_refs, GCCause::Cause cause); 904 void collect_in_foreground(bool clear_all_soft_refs, GCCause::Cause cause); 905 906 // In support of ExplicitGCInvokesConcurrent 907 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 908 // Should we unload classes in a particular concurrent cycle? 909 bool should_unload_classes() const { 910 return _should_unload_classes; 911 } 912 void update_should_unload_classes(); 913 914 void direct_allocated(HeapWord* start, size_t size); 915 916 // Object is dead if not marked and current phase is sweeping. 917 bool is_dead_obj(oop obj) const; 918 919 // After a promotion (of "start"), do any necessary marking. 920 // If "par", then it's being done by a parallel GC thread. 921 // The last two args indicate if we need precise marking 922 // and if so the size of the object so it can be dirtied 923 // in its entirety. 924 void promoted(bool par, HeapWord* start, 925 bool is_obj_array, size_t obj_size); 926 927 HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 928 size_t word_size); 929 930 void getFreelistLocks() const; 931 void releaseFreelistLocks() const; 932 bool haveFreelistLocks() const; 933 934 // Adjust size of underlying generation 935 void compute_new_size(); 936 937 // GC prologue and epilogue 938 void gc_prologue(bool full); 939 void gc_epilogue(bool full); 940 941 jlong time_of_last_gc(jlong now) { 942 if (_collectorState <= Idling) { 943 // gc not in progress 944 return _time_of_last_gc; 945 } else { 946 // collection in progress 947 return now; 948 } 949 } 950 951 // Support for parallel remark of survivor space 952 void* get_data_recorder(int thr_num); 953 954 CMSBitMap* markBitMap() { return &_markBitMap; } 955 void directAllocated(HeapWord* start, size_t size); 956 957 // main CMS steps and related support 958 void checkpointRootsInitial(bool asynch); 959 bool markFromRoots(bool asynch); // a return value of false indicates failure 960 // due to stack overflow 961 void preclean(); 962 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs, 963 bool init_mark_was_synchronous); 964 void sweep(bool asynch); 965 966 // Check that the currently executing thread is the expected 967 // one (foreground collector or background collector). 968 static void check_correct_thread_executing() PRODUCT_RETURN; 969 // XXXPERM void print_statistics() PRODUCT_RETURN; 970 971 bool is_cms_reachable(HeapWord* addr); 972 973 // Performance Counter Support 974 CollectorCounters* counters() { return _gc_counters; } 975 976 // timer stuff 977 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 978 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 979 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 980 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } 981 982 int yields() { return _numYields; } 983 void resetYields() { _numYields = 0; } 984 void incrementYields() { _numYields++; } 985 void resetNumDirtyCards() { _numDirtyCards = 0; } 986 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 987 size_t numDirtyCards() { return _numDirtyCards; } 988 989 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 990 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 991 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 992 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 993 size_t sweep_count() const { return _sweep_count; } 994 void increment_sweep_count() { _sweep_count++; } 995 996 // Timers/stats for gc scheduling and incremental mode pacing. 997 CMSStats& stats() { return _stats; } 998 999 // Convenience methods that check whether CMSIncrementalMode is enabled and 1000 // forward to the corresponding methods in ConcurrentMarkSweepThread. 1001 static void start_icms(); 1002 static void stop_icms(); // Called at the end of the cms cycle. 1003 static void disable_icms(); // Called before a foreground collection. 1004 static void enable_icms(); // Called after a foreground collection. 1005 void icms_wait(); // Called at yield points. 1006 1007 // Adaptive size policy 1008 CMSAdaptiveSizePolicy* size_policy(); 1009 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters(); 1010 1011 static void print_on_error(outputStream* st); 1012 1013 // debugging 1014 void verify(); 1015 bool verify_after_remark(bool silent = VerifySilently); 1016 void verify_ok_to_terminate() const PRODUCT_RETURN; 1017 void verify_work_stacks_empty() const PRODUCT_RETURN; 1018 void verify_overflow_empty() const PRODUCT_RETURN; 1019 1020 // convenience methods in support of debugging 1021 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 1022 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 1023 1024 // accessors 1025 CMSMarkStack* verification_mark_stack() { return &_markStack; } 1026 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 1027 1028 // Initialization errors 1029 bool completed_initialization() { return _completed_initialization; } 1030 }; 1031 1032 class CMSExpansionCause : public AllStatic { 1033 public: 1034 enum Cause { 1035 _no_expansion, 1036 _satisfy_free_ratio, 1037 _satisfy_promotion, 1038 _satisfy_allocation, 1039 _allocate_par_lab, 1040 _allocate_par_spooling_space, 1041 _adaptive_size_policy 1042 }; 1043 // Return a string describing the cause of the expansion. 1044 static const char* to_string(CMSExpansionCause::Cause cause); 1045 }; 1046 1047 class ConcurrentMarkSweepGeneration: public CardGeneration { 1048 friend class VMStructs; 1049 friend class ConcurrentMarkSweepThread; 1050 friend class ConcurrentMarkSweep; 1051 friend class CMSCollector; 1052 protected: 1053 static CMSCollector* _collector; // the collector that collects us 1054 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1055 1056 // Performance Counters 1057 GenerationCounters* _gen_counters; 1058 GSpaceCounters* _space_counters; 1059 1060 // Words directly allocated, used by CMSStats. 1061 size_t _direct_allocated_words; 1062 1063 // Non-product stat counters 1064 NOT_PRODUCT( 1065 size_t _numObjectsPromoted; 1066 size_t _numWordsPromoted; 1067 size_t _numObjectsAllocated; 1068 size_t _numWordsAllocated; 1069 ) 1070 1071 // Used for sizing decisions 1072 bool _incremental_collection_failed; 1073 bool incremental_collection_failed() { 1074 return _incremental_collection_failed; 1075 } 1076 void set_incremental_collection_failed() { 1077 _incremental_collection_failed = true; 1078 } 1079 void clear_incremental_collection_failed() { 1080 _incremental_collection_failed = false; 1081 } 1082 1083 // accessors 1084 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1085 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1086 1087 private: 1088 // For parallel young-gen GC support. 1089 CMSParGCThreadState** _par_gc_thread_states; 1090 1091 // Reason generation was expanded 1092 CMSExpansionCause::Cause _expansion_cause; 1093 1094 // In support of MinChunkSize being larger than min object size 1095 const double _dilatation_factor; 1096 1097 enum CollectionTypes { 1098 Concurrent_collection_type = 0, 1099 MS_foreground_collection_type = 1, 1100 MSC_foreground_collection_type = 2, 1101 Unknown_collection_type = 3 1102 }; 1103 1104 CollectionTypes _debug_collection_type; 1105 1106 // True if a compactiing collection was done. 1107 bool _did_compact; 1108 bool did_compact() { return _did_compact; } 1109 1110 // Fraction of current occupancy at which to start a CMS collection which 1111 // will collect this generation (at least). 1112 double _initiating_occupancy; 1113 1114 protected: 1115 // Shrink generation by specified size (returns false if unable to shrink) 1116 void shrink_free_list_by(size_t bytes); 1117 1118 // Update statistics for GC 1119 virtual void update_gc_stats(int level, bool full); 1120 1121 // Maximum available space in the generation (including uncommitted) 1122 // space. 1123 size_t max_available() const; 1124 1125 // getter and initializer for _initiating_occupancy field. 1126 double initiating_occupancy() const { return _initiating_occupancy; } 1127 void init_initiating_occupancy(intx io, uintx tr); 1128 1129 public: 1130 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1131 int level, CardTableRS* ct, 1132 bool use_adaptive_freelists, 1133 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 1134 1135 // Accessors 1136 CMSCollector* collector() const { return _collector; } 1137 static void set_collector(CMSCollector* collector) { 1138 assert(_collector == NULL, "already set"); 1139 _collector = collector; 1140 } 1141 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1142 1143 Mutex* freelistLock() const; 1144 1145 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1146 1147 // Adaptive size policy 1148 CMSAdaptiveSizePolicy* size_policy(); 1149 1150 void set_did_compact(bool v) { _did_compact = v; } 1151 1152 bool refs_discovery_is_atomic() const { return false; } 1153 bool refs_discovery_is_mt() const { 1154 // Note: CMS does MT-discovery during the parallel-remark 1155 // phases. Use ReferenceProcessorMTMutator to make refs 1156 // discovery MT-safe during such phases or other parallel 1157 // discovery phases in the future. This may all go away 1158 // if/when we decide that refs discovery is sufficiently 1159 // rare that the cost of the CAS's involved is in the 1160 // noise. That's a measurement that should be done, and 1161 // the code simplified if that turns out to be the case. 1162 return ConcGCThreads > 1; 1163 } 1164 1165 // Override 1166 virtual void ref_processor_init(); 1167 1168 // Grow generation by specified size (returns false if unable to grow) 1169 bool grow_by(size_t bytes); 1170 // Grow generation to reserved size. 1171 bool grow_to_reserved(); 1172 1173 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1174 1175 // Space enquiries 1176 size_t capacity() const; 1177 size_t used() const; 1178 size_t free() const; 1179 double occupancy() const { return ((double)used())/((double)capacity()); } 1180 size_t contiguous_available() const; 1181 size_t unsafe_max_alloc_nogc() const; 1182 1183 // over-rides 1184 MemRegion used_region() const; 1185 MemRegion used_region_at_save_marks() const; 1186 1187 // Does a "full" (forced) collection invoked on this generation collect 1188 // all younger generations as well? Note that the second conjunct is a 1189 // hack to allow the collection of the younger gen first if the flag is 1190 // set. This is better than using th policy's should_collect_gen0_first() 1191 // since that causes us to do an extra unnecessary pair of restart-&-stop-world. 1192 virtual bool full_collects_younger_generations() const { 1193 return UseCMSCompactAtFullCollection && !CollectGen0First; 1194 } 1195 1196 void space_iterate(SpaceClosure* blk, bool usedOnly = false); 1197 1198 // Support for compaction 1199 CompactibleSpace* first_compaction_space() const; 1200 // Adjust quantites in the generation affected by 1201 // the compaction. 1202 void reset_after_compaction(); 1203 1204 // Allocation support 1205 HeapWord* allocate(size_t size, bool tlab); 1206 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1207 oop promote(oop obj, size_t obj_size); 1208 HeapWord* par_allocate(size_t size, bool tlab) { 1209 return allocate(size, tlab); 1210 } 1211 1212 // Incremental mode triggering. 1213 HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 1214 size_t word_size); 1215 1216 // Used by CMSStats to track direct allocation. The value is sampled and 1217 // reset after each young gen collection. 1218 size_t direct_allocated_words() const { return _direct_allocated_words; } 1219 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1220 1221 // Overrides for parallel promotion. 1222 virtual oop par_promote(int thread_num, 1223 oop obj, markOop m, size_t word_sz); 1224 // This one should not be called for CMS. 1225 virtual void par_promote_alloc_undo(int thread_num, 1226 HeapWord* obj, size_t word_sz); 1227 virtual void par_promote_alloc_done(int thread_num); 1228 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1229 1230 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1231 1232 // Inform this (non-young) generation that a promotion failure was 1233 // encountered during a collection of a younger generation that 1234 // promotes into this generation. 1235 virtual void promotion_failure_occurred(); 1236 1237 bool should_collect(bool full, size_t size, bool tlab); 1238 virtual bool should_concurrent_collect() const; 1239 virtual bool is_too_full() const; 1240 void collect(bool full, 1241 bool clear_all_soft_refs, 1242 size_t size, 1243 bool tlab); 1244 1245 HeapWord* expand_and_allocate(size_t word_size, 1246 bool tlab, 1247 bool parallel = false); 1248 1249 // GC prologue and epilogue 1250 void gc_prologue(bool full); 1251 void gc_prologue_work(bool full, bool registerClosure, 1252 ModUnionClosure* modUnionClosure); 1253 void gc_epilogue(bool full); 1254 void gc_epilogue_work(bool full); 1255 1256 // Time since last GC of this generation 1257 jlong time_of_last_gc(jlong now) { 1258 return collector()->time_of_last_gc(now); 1259 } 1260 void update_time_of_last_gc(jlong now) { 1261 collector()-> update_time_of_last_gc(now); 1262 } 1263 1264 // Allocation failure 1265 void expand(size_t bytes, size_t expand_bytes, 1266 CMSExpansionCause::Cause cause); 1267 virtual bool expand(size_t bytes, size_t expand_bytes); 1268 void shrink(size_t bytes); 1269 void shrink_by(size_t bytes); 1270 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1271 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1272 1273 // Iteration support and related enquiries 1274 void save_marks(); 1275 bool no_allocs_since_save_marks(); 1276 void object_iterate_since_last_GC(ObjectClosure* cl); 1277 void younger_refs_iterate(OopsInGenClosure* cl); 1278 1279 // Iteration support specific to CMS generations 1280 void save_sweep_limit(); 1281 1282 // More iteration support 1283 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); 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. Delagates 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 1322 // Printing 1323 const char* name() const; 1324 virtual const char* short_name() const { return "CMS"; } 1325 void print() const; 1326 void printOccupancy(const char* s); 1327 bool must_be_youngest() const { return false; } 1328 bool must_be_oldest() const { return true; } 1329 1330 // Resize the generation after a compacting GC. The 1331 // generation can be treated as a contiguous space 1332 // after the compaction. 1333 virtual void compute_new_size(); 1334 // Resize the generation after a non-compacting 1335 // collection. 1336 void compute_new_size_free_list(); 1337 1338 CollectionTypes debug_collection_type() { return _debug_collection_type; } 1339 void rotate_debug_collection_type(); 1340 }; 1341 1342 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration { 1343 1344 // Return the size policy from the heap's collector 1345 // policy casted to CMSAdaptiveSizePolicy*. 1346 CMSAdaptiveSizePolicy* cms_size_policy() const; 1347 1348 // Resize the generation based on the adaptive size 1349 // policy. 1350 void resize(size_t cur_promo, size_t desired_promo); 1351 1352 // Return the GC counters from the collector policy 1353 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters(); 1354 1355 virtual void shrink_by(size_t bytes); 1356 1357 public: 1358 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1359 int level, CardTableRS* ct, 1360 bool use_adaptive_freelists, 1361 FreeBlockDictionary<FreeChunk>::DictionaryChoice 1362 dictionaryChoice) : 1363 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct, 1364 use_adaptive_freelists, dictionaryChoice) {} 1365 1366 virtual const char* short_name() const { return "ASCMS"; } 1367 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; } 1368 1369 virtual void update_counters(); 1370 virtual void update_counters(size_t used); 1371 }; 1372 1373 // 1374 // Closures of various sorts used by CMS to accomplish its work 1375 // 1376 1377 // This closure is used to check that a certain set of oops is empty. 1378 class FalseClosure: public OopClosure { 1379 public: 1380 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); } 1381 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); } 1382 }; 1383 1384 // This closure is used to do concurrent marking from the roots 1385 // following the first checkpoint. 1386 class MarkFromRootsClosure: public BitMapClosure { 1387 CMSCollector* _collector; 1388 MemRegion _span; 1389 CMSBitMap* _bitMap; 1390 CMSBitMap* _mut; 1391 CMSMarkStack* _markStack; 1392 bool _yield; 1393 int _skipBits; 1394 HeapWord* _finger; 1395 HeapWord* _threshold; 1396 DEBUG_ONLY(bool _verifying;) 1397 1398 public: 1399 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1400 CMSBitMap* bitMap, 1401 CMSMarkStack* markStack, 1402 bool should_yield, bool verifying = false); 1403 bool do_bit(size_t offset); 1404 void reset(HeapWord* addr); 1405 inline void do_yield_check(); 1406 1407 private: 1408 void scanOopsInOop(HeapWord* ptr); 1409 void do_yield_work(); 1410 }; 1411 1412 // This closure is used to do concurrent multi-threaded 1413 // marking from the roots following the first checkpoint. 1414 // XXX This should really be a subclass of The serial version 1415 // above, but i have not had the time to refactor things cleanly. 1416 // That willbe done for Dolphin. 1417 class Par_MarkFromRootsClosure: public BitMapClosure { 1418 CMSCollector* _collector; 1419 MemRegion _whole_span; 1420 MemRegion _span; 1421 CMSBitMap* _bit_map; 1422 CMSBitMap* _mut; 1423 OopTaskQueue* _work_queue; 1424 CMSMarkStack* _overflow_stack; 1425 bool _yield; 1426 int _skip_bits; 1427 HeapWord* _finger; 1428 HeapWord* _threshold; 1429 CMSConcMarkingTask* _task; 1430 public: 1431 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1432 MemRegion span, 1433 CMSBitMap* bit_map, 1434 OopTaskQueue* work_queue, 1435 CMSMarkStack* overflow_stack, 1436 bool should_yield); 1437 bool do_bit(size_t offset); 1438 inline void do_yield_check(); 1439 1440 private: 1441 void scan_oops_in_oop(HeapWord* ptr); 1442 void do_yield_work(); 1443 bool get_work_from_overflow_stack(); 1444 }; 1445 1446 // The following closures are used to do certain kinds of verification of 1447 // CMS marking. 1448 class PushAndMarkVerifyClosure: public CMSOopClosure { 1449 CMSCollector* _collector; 1450 MemRegion _span; 1451 CMSBitMap* _verification_bm; 1452 CMSBitMap* _cms_bm; 1453 CMSMarkStack* _mark_stack; 1454 protected: 1455 void do_oop(oop p); 1456 template <class T> inline void do_oop_work(T *p) { 1457 oop obj = oopDesc::load_decode_heap_oop(p); 1458 do_oop(obj); 1459 } 1460 public: 1461 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1462 MemRegion span, 1463 CMSBitMap* verification_bm, 1464 CMSBitMap* cms_bm, 1465 CMSMarkStack* mark_stack); 1466 void do_oop(oop* p); 1467 void do_oop(narrowOop* p); 1468 1469 // Deal with a stack overflow condition 1470 void handle_stack_overflow(HeapWord* lost); 1471 }; 1472 1473 class MarkFromRootsVerifyClosure: public BitMapClosure { 1474 CMSCollector* _collector; 1475 MemRegion _span; 1476 CMSBitMap* _verification_bm; 1477 CMSBitMap* _cms_bm; 1478 CMSMarkStack* _mark_stack; 1479 HeapWord* _finger; 1480 PushAndMarkVerifyClosure _pam_verify_closure; 1481 public: 1482 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1483 CMSBitMap* verification_bm, 1484 CMSBitMap* cms_bm, 1485 CMSMarkStack* mark_stack); 1486 bool do_bit(size_t offset); 1487 void reset(HeapWord* addr); 1488 }; 1489 1490 1491 // This closure is used to check that a certain set of bits is 1492 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1493 class FalseBitMapClosure: public BitMapClosure { 1494 public: 1495 bool do_bit(size_t offset) { 1496 guarantee(false, "Should not have a 1 bit"); 1497 return true; 1498 } 1499 }; 1500 1501 // This closure is used during the second checkpointing phase 1502 // to rescan the marked objects on the dirty cards in the mod 1503 // union table and the card table proper. It's invoked via 1504 // MarkFromDirtyCardsClosure below. It uses either 1505 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1506 // declared in genOopClosures.hpp to accomplish some of its work. 1507 // In the parallel case the bitMap is shared, so access to 1508 // it needs to be suitably synchronized for updates by embedded 1509 // closures that update it; however, this closure itself only 1510 // reads the bit_map and because it is idempotent, is immune to 1511 // reading stale values. 1512 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1513 #ifdef ASSERT 1514 CMSCollector* _collector; 1515 MemRegion _span; 1516 union { 1517 CMSMarkStack* _mark_stack; 1518 OopTaskQueue* _work_queue; 1519 }; 1520 #endif // ASSERT 1521 bool _parallel; 1522 CMSBitMap* _bit_map; 1523 union { 1524 MarkRefsIntoAndScanClosure* _scan_closure; 1525 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1526 }; 1527 1528 public: 1529 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1530 MemRegion span, 1531 ReferenceProcessor* rp, 1532 CMSBitMap* bit_map, 1533 CMSMarkStack* mark_stack, 1534 MarkRefsIntoAndScanClosure* cl): 1535 #ifdef ASSERT 1536 _collector(collector), 1537 _span(span), 1538 _mark_stack(mark_stack), 1539 #endif // ASSERT 1540 _parallel(false), 1541 _bit_map(bit_map), 1542 _scan_closure(cl) { } 1543 1544 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1545 MemRegion span, 1546 ReferenceProcessor* rp, 1547 CMSBitMap* bit_map, 1548 OopTaskQueue* work_queue, 1549 Par_MarkRefsIntoAndScanClosure* cl): 1550 #ifdef ASSERT 1551 _collector(collector), 1552 _span(span), 1553 _work_queue(work_queue), 1554 #endif // ASSERT 1555 _parallel(true), 1556 _bit_map(bit_map), 1557 _par_scan_closure(cl) { } 1558 1559 bool do_object_b(oop obj) { 1560 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1561 return false; 1562 } 1563 bool do_object_bm(oop p, MemRegion mr); 1564 }; 1565 1566 // This closure is used during the second checkpointing phase 1567 // to rescan the marked objects on the dirty cards in the mod 1568 // union table and the card table proper. It invokes 1569 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1570 // In the parallel case, the bit map is shared and requires 1571 // synchronized access. 1572 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1573 CompactibleFreeListSpace* _space; 1574 ScanMarkedObjectsAgainClosure _scan_cl; 1575 size_t _num_dirty_cards; 1576 1577 public: 1578 MarkFromDirtyCardsClosure(CMSCollector* collector, 1579 MemRegion span, 1580 CompactibleFreeListSpace* space, 1581 CMSBitMap* bit_map, 1582 CMSMarkStack* mark_stack, 1583 MarkRefsIntoAndScanClosure* cl): 1584 _space(space), 1585 _num_dirty_cards(0), 1586 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1587 mark_stack, cl) { } 1588 1589 MarkFromDirtyCardsClosure(CMSCollector* collector, 1590 MemRegion span, 1591 CompactibleFreeListSpace* space, 1592 CMSBitMap* bit_map, 1593 OopTaskQueue* work_queue, 1594 Par_MarkRefsIntoAndScanClosure* cl): 1595 _space(space), 1596 _num_dirty_cards(0), 1597 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1598 work_queue, cl) { } 1599 1600 void do_MemRegion(MemRegion mr); 1601 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1602 size_t num_dirty_cards() { return _num_dirty_cards; } 1603 }; 1604 1605 // This closure is used in the non-product build to check 1606 // that there are no MemRegions with a certain property. 1607 class FalseMemRegionClosure: public MemRegionClosure { 1608 void do_MemRegion(MemRegion mr) { 1609 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1610 guarantee(false, "Should never be here"); 1611 } 1612 }; 1613 1614 // This closure is used during the precleaning phase 1615 // to "carefully" rescan marked objects on dirty cards. 1616 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1617 // to accomplish some of its work. 1618 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1619 CMSCollector* _collector; 1620 MemRegion _span; 1621 bool _yield; 1622 Mutex* _freelistLock; 1623 CMSBitMap* _bitMap; 1624 CMSMarkStack* _markStack; 1625 MarkRefsIntoAndScanClosure* _scanningClosure; 1626 1627 public: 1628 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1629 MemRegion span, 1630 CMSBitMap* bitMap, 1631 CMSMarkStack* markStack, 1632 MarkRefsIntoAndScanClosure* cl, 1633 bool should_yield): 1634 _collector(collector), 1635 _span(span), 1636 _yield(should_yield), 1637 _bitMap(bitMap), 1638 _markStack(markStack), 1639 _scanningClosure(cl) { 1640 } 1641 1642 void do_object(oop p) { 1643 guarantee(false, "call do_object_careful instead"); 1644 } 1645 1646 size_t do_object_careful(oop p) { 1647 guarantee(false, "Unexpected caller"); 1648 return 0; 1649 } 1650 1651 size_t do_object_careful_m(oop p, MemRegion mr); 1652 1653 void setFreelistLock(Mutex* m) { 1654 _freelistLock = m; 1655 _scanningClosure->set_freelistLock(m); 1656 } 1657 1658 private: 1659 inline bool do_yield_check(); 1660 1661 void do_yield_work(); 1662 }; 1663 1664 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1665 CMSCollector* _collector; 1666 MemRegion _span; 1667 bool _yield; 1668 CMSBitMap* _bit_map; 1669 CMSMarkStack* _mark_stack; 1670 PushAndMarkClosure* _scanning_closure; 1671 unsigned int _before_count; 1672 1673 public: 1674 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1675 MemRegion span, 1676 CMSBitMap* bit_map, 1677 CMSMarkStack* mark_stack, 1678 PushAndMarkClosure* cl, 1679 unsigned int before_count, 1680 bool should_yield): 1681 _collector(collector), 1682 _span(span), 1683 _yield(should_yield), 1684 _bit_map(bit_map), 1685 _mark_stack(mark_stack), 1686 _scanning_closure(cl), 1687 _before_count(before_count) 1688 { } 1689 1690 void do_object(oop p) { 1691 guarantee(false, "call do_object_careful instead"); 1692 } 1693 1694 size_t do_object_careful(oop p); 1695 1696 size_t do_object_careful_m(oop p, MemRegion mr) { 1697 guarantee(false, "Unexpected caller"); 1698 return 0; 1699 } 1700 1701 private: 1702 inline void do_yield_check(); 1703 void do_yield_work(); 1704 }; 1705 1706 // This closure is used to accomplish the sweeping work 1707 // after the second checkpoint but before the concurrent reset 1708 // phase. 1709 // 1710 // Terminology 1711 // left hand chunk (LHC) - block of one or more chunks currently being 1712 // coalesced. The LHC is available for coalescing with a new chunk. 1713 // right hand chunk (RHC) - block that is currently being swept that is 1714 // free or garbage that can be coalesced with the LHC. 1715 // _inFreeRange is true if there is currently a LHC 1716 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1717 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1718 // _freeFinger is the address of the current LHC 1719 class SweepClosure: public BlkClosureCareful { 1720 CMSCollector* _collector; // collector doing the work 1721 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1722 CompactibleFreeListSpace* _sp; // Space being swept 1723 HeapWord* _limit;// the address at or above which the sweep should stop 1724 // because we do not expect newly garbage blocks 1725 // eligible for sweeping past that address. 1726 Mutex* _freelistLock; // Free list lock (in space) 1727 CMSBitMap* _bitMap; // Marking bit map (in 1728 // generation) 1729 bool _inFreeRange; // Indicates if we are in the 1730 // midst of a free run 1731 bool _freeRangeInFreeLists; 1732 // Often, we have just found 1733 // a free chunk and started 1734 // a new free range; we do not 1735 // eagerly remove this chunk from 1736 // the free lists unless there is 1737 // a possibility of coalescing. 1738 // When true, this flag indicates 1739 // that the _freeFinger below 1740 // points to a potentially free chunk 1741 // that may still be in the free lists 1742 bool _lastFreeRangeCoalesced; 1743 // free range contains chunks 1744 // coalesced 1745 bool _yield; 1746 // Whether sweeping should be 1747 // done with yields. For instance 1748 // when done by the foreground 1749 // collector we shouldn't yield. 1750 HeapWord* _freeFinger; // When _inFreeRange is set, the 1751 // pointer to the "left hand 1752 // chunk" 1753 size_t _freeRangeSize; 1754 // When _inFreeRange is set, this 1755 // indicates the accumulated size 1756 // of the "left hand chunk" 1757 NOT_PRODUCT( 1758 size_t _numObjectsFreed; 1759 size_t _numWordsFreed; 1760 size_t _numObjectsLive; 1761 size_t _numWordsLive; 1762 size_t _numObjectsAlreadyFree; 1763 size_t _numWordsAlreadyFree; 1764 FreeChunk* _last_fc; 1765 ) 1766 private: 1767 // Code that is common to a free chunk or garbage when 1768 // encountered during sweeping. 1769 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1770 // Process a free chunk during sweeping. 1771 void do_already_free_chunk(FreeChunk *fc); 1772 // Work method called when processing an already free or a 1773 // freshly garbage chunk to do a lookahead and possibly a 1774 // premptive flush if crossing over _limit. 1775 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1776 // Process a garbage chunk during sweeping. 1777 size_t do_garbage_chunk(FreeChunk *fc); 1778 // Process a live chunk during sweeping. 1779 size_t do_live_chunk(FreeChunk* fc); 1780 1781 // Accessors. 1782 HeapWord* freeFinger() const { return _freeFinger; } 1783 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1784 bool inFreeRange() const { return _inFreeRange; } 1785 void set_inFreeRange(bool v) { _inFreeRange = v; } 1786 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1787 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1788 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1789 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1790 1791 // Initialize a free range. 1792 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1793 // Return this chunk to the free lists. 1794 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1795 1796 // Check if we should yield and do so when necessary. 1797 inline void do_yield_check(HeapWord* addr); 1798 1799 // Yield 1800 void do_yield_work(HeapWord* addr); 1801 1802 // Debugging/Printing 1803 void print_free_block_coalesced(FreeChunk* fc) const; 1804 1805 public: 1806 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1807 CMSBitMap* bitMap, bool should_yield); 1808 ~SweepClosure() PRODUCT_RETURN; 1809 1810 size_t do_blk_careful(HeapWord* addr); 1811 void print() const { print_on(tty); } 1812 void print_on(outputStream *st) const; 1813 }; 1814 1815 // Closures related to weak references processing 1816 1817 // During CMS' weak reference processing, this is a 1818 // work-routine/closure used to complete transitive 1819 // marking of objects as live after a certain point 1820 // in which an initial set has been completely accumulated. 1821 // This closure is currently used both during the final 1822 // remark stop-world phase, as well as during the concurrent 1823 // precleaning of the discovered reference lists. 1824 class CMSDrainMarkingStackClosure: public VoidClosure { 1825 CMSCollector* _collector; 1826 MemRegion _span; 1827 CMSMarkStack* _mark_stack; 1828 CMSBitMap* _bit_map; 1829 CMSKeepAliveClosure* _keep_alive; 1830 bool _concurrent_precleaning; 1831 public: 1832 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1833 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1834 CMSKeepAliveClosure* keep_alive, 1835 bool cpc): 1836 _collector(collector), 1837 _span(span), 1838 _bit_map(bit_map), 1839 _mark_stack(mark_stack), 1840 _keep_alive(keep_alive), 1841 _concurrent_precleaning(cpc) { 1842 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1843 "Mismatch"); 1844 } 1845 1846 void do_void(); 1847 }; 1848 1849 // A parallel version of CMSDrainMarkingStackClosure above. 1850 class CMSParDrainMarkingStackClosure: public VoidClosure { 1851 CMSCollector* _collector; 1852 MemRegion _span; 1853 OopTaskQueue* _work_queue; 1854 CMSBitMap* _bit_map; 1855 CMSInnerParMarkAndPushClosure _mark_and_push; 1856 1857 public: 1858 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1859 MemRegion span, CMSBitMap* bit_map, 1860 OopTaskQueue* work_queue): 1861 _collector(collector), 1862 _span(span), 1863 _bit_map(bit_map), 1864 _work_queue(work_queue), 1865 _mark_and_push(collector, span, bit_map, work_queue) { } 1866 1867 public: 1868 void trim_queue(uint max); 1869 void do_void(); 1870 }; 1871 1872 // Allow yielding or short-circuiting of reference list 1873 // prelceaning work. 1874 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1875 CMSCollector* _collector; 1876 void do_yield_work(); 1877 public: 1878 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1879 _collector(collector) {} 1880 virtual bool should_return(); 1881 }; 1882 1883 1884 // Convenience class that locks free list locks for given CMS collector 1885 class FreelistLocker: public StackObj { 1886 private: 1887 CMSCollector* _collector; 1888 public: 1889 FreelistLocker(CMSCollector* collector): 1890 _collector(collector) { 1891 _collector->getFreelistLocks(); 1892 } 1893 1894 ~FreelistLocker() { 1895 _collector->releaseFreelistLocks(); 1896 } 1897 }; 1898 1899 // Mark all dead objects in a given space. 1900 class MarkDeadObjectsClosure: public BlkClosure { 1901 const CMSCollector* _collector; 1902 const CompactibleFreeListSpace* _sp; 1903 CMSBitMap* _live_bit_map; 1904 CMSBitMap* _dead_bit_map; 1905 public: 1906 MarkDeadObjectsClosure(const CMSCollector* collector, 1907 const CompactibleFreeListSpace* sp, 1908 CMSBitMap *live_bit_map, 1909 CMSBitMap *dead_bit_map) : 1910 _collector(collector), 1911 _sp(sp), 1912 _live_bit_map(live_bit_map), 1913 _dead_bit_map(dead_bit_map) {} 1914 size_t do_blk(HeapWord* addr); 1915 }; 1916 1917 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1918 1919 public: 1920 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1921 }; 1922 1923 1924 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP