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/gSpaceCounters.hpp" 29 #include "gc_implementation/shared/gcStats.hpp" 30 #include "gc_implementation/shared/generationCounters.hpp" 31 #include "memory/freeBlockDictionary.hpp" 32 #include "memory/generation.hpp" 33 #include "runtime/mutexLocker.hpp" 34 #include "runtime/virtualspace.hpp" 35 #include "services/memoryService.hpp" 36 #include "utilities/bitMap.inline.hpp" 37 #include "utilities/stack.inline.hpp" 38 #include "utilities/taskqueue.hpp" 39 #include "utilities/yieldingWorkgroup.hpp" 40 41 // ConcurrentMarkSweepGeneration is in support of a concurrent 42 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker 43 // style. We assume, for now, that this generation is always the 44 // seniormost generation and for simplicity 45 // in the first implementation, that this generation is a single compactible 46 // space. Neither of these restrictions appears essential, and will be 47 // relaxed in the future when more time is available to implement the 48 // greater generality (and there's a need for it). 49 // 50 // Concurrent mode failures are currently handled by 51 // means of a sliding mark-compact. 52 53 class CMSAdaptiveSizePolicy; 54 class CMSConcMarkingTask; 55 class CMSGCAdaptivePolicyCounters; 56 class ConcurrentMarkSweepGeneration; 57 class ConcurrentMarkSweepPolicy; 58 class ConcurrentMarkSweepThread; 59 class CompactibleFreeListSpace; 60 class FreeChunk; 61 class PromotionInfo; 62 class ScanMarkedObjectsAgainCarefullyClosure; 63 class TenuredGeneration; 64 65 // A generic CMS bit map. It's the basis for both the CMS marking bit map 66 // as well as for the mod union table (in each case only a subset of the 67 // methods are used). This is essentially a wrapper around the BitMap class, 68 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 69 // we have _shifter == 0. and for the mod union table we have 70 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 71 // XXX 64-bit issues in BitMap? 72 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 73 friend class VMStructs; 74 75 HeapWord* _bmStartWord; // base address of range covered by map 76 size_t _bmWordSize; // map size (in #HeapWords covered) 77 const int _shifter; // shifts to convert HeapWord to bit position 78 VirtualSpace _virtual_space; // underlying the bit map 79 BitMap _bm; // the bit map itself 80 public: 81 Mutex* const _lock; // mutex protecting _bm; 82 83 public: 84 // constructor 85 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 86 87 // allocates the actual storage for the map 88 bool allocate(MemRegion mr); 89 // field getter 90 Mutex* lock() const { return _lock; } 91 // locking verifier convenience function 92 void assert_locked() const PRODUCT_RETURN; 93 94 // inquiries 95 HeapWord* startWord() const { return _bmStartWord; } 96 size_t sizeInWords() const { return _bmWordSize; } 97 size_t sizeInBits() const { return _bm.size(); } 98 // the following is one past the last word in space 99 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 100 101 // reading marks 102 bool isMarked(HeapWord* addr) const; 103 bool par_isMarked(HeapWord* addr) const; // do not lock checks 104 bool isUnmarked(HeapWord* addr) const; 105 bool isAllClear() const; 106 107 // writing marks 108 void mark(HeapWord* addr); 109 // For marking by parallel GC threads; 110 // returns true if we did, false if another thread did 111 bool par_mark(HeapWord* addr); 112 113 void mark_range(MemRegion mr); 114 void par_mark_range(MemRegion mr); 115 void mark_large_range(MemRegion mr); 116 void par_mark_large_range(MemRegion mr); 117 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 118 void clear_range(MemRegion mr); 119 void par_clear_range(MemRegion mr); 120 void clear_large_range(MemRegion mr); 121 void par_clear_large_range(MemRegion mr); 122 void clear_all(); 123 void clear_all_incrementally(); // Not yet implemented!! 124 125 NOT_PRODUCT( 126 // checks the memory region for validity 127 void region_invariant(MemRegion mr); 128 ) 129 130 // iteration 131 void iterate(BitMapClosure* cl) { 132 _bm.iterate(cl); 133 } 134 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 135 void dirty_range_iterate_clear(MemRegionClosure* cl); 136 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 137 138 // auxiliary support for iteration 139 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 140 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 141 HeapWord* end_addr) const; 142 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 143 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 144 HeapWord* end_addr) const; 145 MemRegion getAndClearMarkedRegion(HeapWord* addr); 146 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 147 HeapWord* end_addr); 148 149 // conversion utilities 150 HeapWord* offsetToHeapWord(size_t offset) const; 151 size_t heapWordToOffset(HeapWord* addr) const; 152 size_t heapWordDiffToOffsetDiff(size_t diff) const; 153 154 void print_on_error(outputStream* st, const char* prefix) const; 155 156 // debugging 157 // is this address range covered by the bit-map? 158 NOT_PRODUCT( 159 bool covers(MemRegion mr) const; 160 bool covers(HeapWord* start, size_t size = 0) const; 161 ) 162 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 163 }; 164 165 // Represents a marking stack used by the CMS collector. 166 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 167 class CMSMarkStack: public CHeapObj<mtGC> { 168 // 169 friend class CMSCollector; // to get at expasion stats further below 170 // 171 172 VirtualSpace _virtual_space; // space for the stack 173 oop* _base; // bottom of stack 174 size_t _index; // one more than last occupied index 175 size_t _capacity; // max #elements 176 Mutex _par_lock; // an advisory lock used in case of parallel access 177 NOT_PRODUCT(size_t _max_depth;) // max depth plumbed during run 178 179 protected: 180 size_t _hit_limit; // we hit max stack size limit 181 size_t _failed_double; // we failed expansion before hitting limit 182 183 public: 184 CMSMarkStack(): 185 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true), 186 _hit_limit(0), 187 _failed_double(0) {} 188 189 bool allocate(size_t size); 190 191 size_t capacity() const { return _capacity; } 192 193 oop pop() { 194 if (!isEmpty()) { 195 return _base[--_index] ; 196 } 197 return NULL; 198 } 199 200 bool push(oop ptr) { 201 if (isFull()) { 202 return false; 203 } else { 204 _base[_index++] = ptr; 205 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 206 return true; 207 } 208 } 209 210 bool isEmpty() const { return _index == 0; } 211 bool isFull() const { 212 assert(_index <= _capacity, "buffer overflow"); 213 return _index == _capacity; 214 } 215 216 size_t length() { return _index; } 217 218 // "Parallel versions" of some of the above 219 oop par_pop() { 220 // lock and pop 221 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 222 return pop(); 223 } 224 225 bool par_push(oop ptr) { 226 // lock and push 227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 228 return push(ptr); 229 } 230 231 // Forcibly reset the stack, losing all of its contents. 232 void reset() { 233 _index = 0; 234 } 235 236 // Expand the stack, typically in response to an overflow condition 237 void expand(); 238 239 // Compute the least valued stack element. 240 oop least_value(HeapWord* low) { 241 oop least = (oop)low; 242 for (size_t i = 0; i < _index; i++) { 243 least = MIN2(least, _base[i]); 244 } 245 return least; 246 } 247 248 // Exposed here to allow stack expansion in || case 249 Mutex* par_lock() { return &_par_lock; } 250 }; 251 252 class CardTableRS; 253 class CMSParGCThreadState; 254 255 class ModUnionClosure: public MemRegionClosure { 256 protected: 257 CMSBitMap* _t; 258 public: 259 ModUnionClosure(CMSBitMap* t): _t(t) { } 260 void do_MemRegion(MemRegion mr); 261 }; 262 263 class ModUnionClosurePar: public ModUnionClosure { 264 public: 265 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 266 void do_MemRegion(MemRegion mr); 267 }; 268 269 // Survivor Chunk Array in support of parallelization of 270 // Survivor Space rescan. 271 class ChunkArray: public CHeapObj<mtGC> { 272 size_t _index; 273 size_t _capacity; 274 size_t _overflows; 275 HeapWord** _array; // storage for array 276 277 public: 278 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 279 ChunkArray(HeapWord** a, size_t c): 280 _index(0), _capacity(c), _overflows(0), _array(a) {} 281 282 HeapWord** array() { return _array; } 283 void set_array(HeapWord** a) { _array = a; } 284 285 size_t capacity() { return _capacity; } 286 void set_capacity(size_t c) { _capacity = c; } 287 288 size_t end() { 289 assert(_index <= capacity(), 290 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 291 _index, _capacity)); 292 return _index; 293 } // exclusive 294 295 HeapWord* nth(size_t n) { 296 assert(n < end(), "Out of bounds access"); 297 return _array[n]; 298 } 299 300 void reset() { 301 _index = 0; 302 if (_overflows > 0 && PrintCMSStatistics > 1) { 303 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", 304 _capacity, _overflows); 305 } 306 _overflows = 0; 307 } 308 309 void record_sample(HeapWord* p, size_t sz) { 310 // For now we do not do anything with the size 311 if (_index < _capacity) { 312 _array[_index++] = p; 313 } else { 314 ++_overflows; 315 assert(_index == _capacity, 316 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 317 "): out of bounds at overflow#" SIZE_FORMAT, 318 _index, _capacity, _overflows)); 319 } 320 } 321 }; 322 323 // 324 // Timing, allocation and promotion statistics for gc scheduling and incremental 325 // mode pacing. Most statistics are exponential averages. 326 // 327 class CMSStats VALUE_OBJ_CLASS_SPEC { 328 private: 329 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 330 331 // The following are exponential averages with factor alpha: 332 // avg = (100 - alpha) * avg + alpha * cur_sample 333 // 334 // The durations measure: end_time[n] - start_time[n] 335 // The periods measure: start_time[n] - start_time[n-1] 336 // 337 // The cms period and duration include only concurrent collections; time spent 338 // in foreground cms collections due to System.gc() or because of a failure to 339 // keep up are not included. 340 // 341 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 342 // real value, but is used only after the first period. A value of 100 is 343 // used for the first sample so it gets the entire weight. 344 unsigned int _saved_alpha; // 0-100 345 unsigned int _gc0_alpha; 346 unsigned int _cms_alpha; 347 348 double _gc0_duration; 349 double _gc0_period; 350 size_t _gc0_promoted; // bytes promoted per gc0 351 double _cms_duration; 352 double _cms_duration_pre_sweep; // time from initiation to start of sweep 353 double _cms_duration_per_mb; 354 double _cms_period; 355 size_t _cms_allocated; // bytes of direct allocation per gc0 period 356 357 // Timers. 358 elapsedTimer _cms_timer; 359 TimeStamp _gc0_begin_time; 360 TimeStamp _cms_begin_time; 361 TimeStamp _cms_end_time; 362 363 // Snapshots of the amount used in the CMS generation. 364 size_t _cms_used_at_gc0_begin; 365 size_t _cms_used_at_gc0_end; 366 size_t _cms_used_at_cms_begin; 367 368 // Used to prevent the duty cycle from being reduced in the middle of a cms 369 // cycle. 370 bool _allow_duty_cycle_reduction; 371 372 enum { 373 _GC0_VALID = 0x1, 374 _CMS_VALID = 0x2, 375 _ALL_VALID = _GC0_VALID | _CMS_VALID 376 }; 377 378 unsigned int _valid_bits; 379 380 unsigned int _icms_duty_cycle; // icms duty cycle (0-100). 381 382 protected: 383 384 // Return a duty cycle that avoids wild oscillations, by limiting the amount 385 // of change between old_duty_cycle and new_duty_cycle (the latter is treated 386 // as a recommended value). 387 static unsigned int icms_damped_duty_cycle(unsigned int old_duty_cycle, 388 unsigned int new_duty_cycle); 389 unsigned int icms_update_duty_cycle_impl(); 390 391 // In support of adjusting of cms trigger ratios based on history 392 // of concurrent mode failure. 393 double cms_free_adjustment_factor(size_t free) const; 394 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 395 396 public: 397 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 398 unsigned int alpha = CMSExpAvgFactor); 399 400 // Whether or not the statistics contain valid data; higher level statistics 401 // cannot be called until this returns true (they require at least one young 402 // gen and one cms cycle to have completed). 403 bool valid() const; 404 405 // Record statistics. 406 void record_gc0_begin(); 407 void record_gc0_end(size_t cms_gen_bytes_used); 408 void record_cms_begin(); 409 void record_cms_end(); 410 411 // Allow management of the cms timer, which must be stopped/started around 412 // yield points. 413 elapsedTimer& cms_timer() { return _cms_timer; } 414 void start_cms_timer() { _cms_timer.start(); } 415 void stop_cms_timer() { _cms_timer.stop(); } 416 417 // Basic statistics; units are seconds or bytes. 418 double gc0_period() const { return _gc0_period; } 419 double gc0_duration() const { return _gc0_duration; } 420 size_t gc0_promoted() const { return _gc0_promoted; } 421 double cms_period() const { return _cms_period; } 422 double cms_duration() const { return _cms_duration; } 423 double cms_duration_per_mb() const { return _cms_duration_per_mb; } 424 size_t cms_allocated() const { return _cms_allocated; } 425 426 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 427 428 // Seconds since the last background cms cycle began or ended. 429 double cms_time_since_begin() const; 430 double cms_time_since_end() const; 431 432 // Higher level statistics--caller must check that valid() returns true before 433 // calling. 434 435 // Returns bytes promoted per second of wall clock time. 436 double promotion_rate() const; 437 438 // Returns bytes directly allocated per second of wall clock time. 439 double cms_allocation_rate() const; 440 441 // Rate at which space in the cms generation is being consumed (sum of the 442 // above two). 443 double cms_consumption_rate() const; 444 445 // Returns an estimate of the number of seconds until the cms generation will 446 // fill up, assuming no collection work is done. 447 double time_until_cms_gen_full() const; 448 449 // Returns an estimate of the number of seconds remaining until 450 // the cms generation collection should start. 451 double time_until_cms_start() const; 452 453 // End of higher level statistics. 454 455 // Returns the cms incremental mode duty cycle, as a percentage (0-100). 456 unsigned int icms_duty_cycle() const { return _icms_duty_cycle; } 457 458 // Update the duty cycle and return the new value. 459 unsigned int icms_update_duty_cycle(); 460 461 // Debugging. 462 void print_on(outputStream* st) const PRODUCT_RETURN; 463 void print() const { print_on(gclog_or_tty); } 464 }; 465 466 // A closure related to weak references processing which 467 // we embed in the CMSCollector, since we need to pass 468 // it to the reference processor for secondary filtering 469 // of references based on reachability of referent; 470 // see role of _is_alive_non_header closure in the 471 // ReferenceProcessor class. 472 // For objects in the CMS generation, this closure checks 473 // if the object is "live" (reachable). Used in weak 474 // reference processing. 475 class CMSIsAliveClosure: public BoolObjectClosure { 476 const MemRegion _span; 477 const CMSBitMap* _bit_map; 478 479 friend class CMSCollector; 480 public: 481 CMSIsAliveClosure(MemRegion span, 482 CMSBitMap* bit_map): 483 _span(span), 484 _bit_map(bit_map) { 485 assert(!span.is_empty(), "Empty span could spell trouble"); 486 } 487 488 void do_object(oop obj) { 489 assert(false, "not to be invoked"); 490 } 491 492 bool do_object_b(oop obj); 493 }; 494 495 496 // Implements AbstractRefProcTaskExecutor for CMS. 497 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 498 public: 499 500 CMSRefProcTaskExecutor(CMSCollector& collector) 501 : _collector(collector) 502 { } 503 504 // Executes a task using worker threads. 505 virtual void execute(ProcessTask& task); 506 virtual void execute(EnqueueTask& task); 507 private: 508 CMSCollector& _collector; 509 }; 510 511 512 class CMSCollector: public CHeapObj<mtGC> { 513 friend class VMStructs; 514 friend class ConcurrentMarkSweepThread; 515 friend class ConcurrentMarkSweepGeneration; 516 friend class CompactibleFreeListSpace; 517 friend class CMSParMarkTask; 518 friend class CMSParInitialMarkTask; 519 friend class CMSParRemarkTask; 520 friend class CMSConcMarkingTask; 521 friend class CMSRefProcTaskProxy; 522 friend class CMSRefProcTaskExecutor; 523 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 524 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 525 friend class PushOrMarkClosure; // to access _restart_addr 526 friend class Par_PushOrMarkClosure; // to access _restart_addr 527 friend class MarkFromRootsClosure; // -- ditto -- 528 // ... and for clearing cards 529 friend class Par_MarkFromRootsClosure; // to access _restart_addr 530 // ... and for clearing cards 531 friend class Par_ConcMarkingClosure; // to access _restart_addr etc. 532 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 533 friend class PushAndMarkVerifyClosure; // -- ditto -- 534 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 535 friend class PushAndMarkClosure; // -- ditto -- 536 friend class Par_PushAndMarkClosure; // -- ditto -- 537 friend class CMSKeepAliveClosure; // -- ditto -- 538 friend class CMSDrainMarkingStackClosure; // -- ditto -- 539 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 540 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 541 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 542 friend class VM_CMS_Operation; 543 friend class VM_CMS_Initial_Mark; 544 friend class VM_CMS_Final_Remark; 545 friend class TraceCMSMemoryManagerStats; 546 547 private: 548 jlong _time_of_last_gc; 549 void update_time_of_last_gc(jlong now) { 550 _time_of_last_gc = now; 551 } 552 553 OopTaskQueueSet* _task_queues; 554 555 // Overflow list of grey objects, threaded through mark-word 556 // Manipulated with CAS in the parallel/multi-threaded case. 557 oop _overflow_list; 558 // The following array-pair keeps track of mark words 559 // displaced for accomodating overflow list above. 560 // This code will likely be revisited under RFE#4922830. 561 Stack<oop, mtGC> _preserved_oop_stack; 562 Stack<markOop, mtGC> _preserved_mark_stack; 563 564 int* _hash_seed; 565 566 // In support of multi-threaded concurrent phases 567 YieldingFlexibleWorkGang* _conc_workers; 568 569 // Performance Counters 570 CollectorCounters* _gc_counters; 571 572 // Initialization Errors 573 bool _completed_initialization; 574 575 // In support of ExplicitGCInvokesConcurrent 576 static bool _full_gc_requested; 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 protected: 619 ConcurrentMarkSweepGeneration* _cmsGen; // old gen (CMS) 620 MemRegion _span; // span covering above two 621 CardTableRS* _ct; // card table 622 623 // CMS marking support structures 624 CMSBitMap _markBitMap; 625 CMSBitMap _modUnionTable; 626 CMSMarkStack _markStack; 627 628 HeapWord* _restart_addr; // in support of marking stack overflow 629 void lower_restart_addr(HeapWord* low); 630 631 // Counters in support of marking stack / work queue overflow handling: 632 // a non-zero value indicates certain types of overflow events during 633 // the current CMS cycle and could lead to stack resizing efforts at 634 // an opportune future time. 635 size_t _ser_pmc_preclean_ovflw; 636 size_t _ser_pmc_remark_ovflw; 637 size_t _par_pmc_remark_ovflw; 638 size_t _ser_kac_preclean_ovflw; 639 size_t _ser_kac_ovflw; 640 size_t _par_kac_ovflw; 641 NOT_PRODUCT(ssize_t _num_par_pushes;) 642 643 // ("Weak") Reference processing support 644 ReferenceProcessor* _ref_processor; 645 CMSIsAliveClosure _is_alive_closure; 646 // keep this textually after _markBitMap and _span; c'tor dependency 647 648 ConcurrentMarkSweepThread* _cmsThread; // the thread doing the work 649 ModUnionClosure _modUnionClosure; 650 ModUnionClosurePar _modUnionClosurePar; 651 652 // CMS abstract state machine 653 // initial_state: Idling 654 // next_state(Idling) = {Marking} 655 // next_state(Marking) = {Precleaning, Sweeping} 656 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 657 // next_state(AbortablePreclean) = {FinalMarking} 658 // next_state(FinalMarking) = {Sweeping} 659 // next_state(Sweeping) = {Resizing} 660 // next_state(Resizing) = {Resetting} 661 // next_state(Resetting) = {Idling} 662 // The numeric values below are chosen so that: 663 // . _collectorState <= Idling == post-sweep && pre-mark 664 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 665 // precleaning || abortablePrecleanb 666 public: 667 enum CollectorState { 668 Resizing = 0, 669 Resetting = 1, 670 Idling = 2, 671 InitialMarking = 3, 672 Marking = 4, 673 Precleaning = 5, 674 AbortablePreclean = 6, 675 FinalMarking = 7, 676 Sweeping = 8 677 }; 678 protected: 679 static CollectorState _collectorState; 680 681 // State related to prologue/epilogue invocation for my generations 682 bool _between_prologue_and_epilogue; 683 684 // Signalling/State related to coordination between fore- and backgroud GC 685 // Note: When the baton has been passed from background GC to foreground GC, 686 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 687 static bool _foregroundGCIsActive; // true iff foreground collector is active or 688 // wants to go active 689 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 690 // yet passed the baton to the foreground GC 691 692 // Support for CMSScheduleRemark (abortable preclean) 693 bool _abort_preclean; 694 bool _start_sampling; 695 696 int _numYields; 697 size_t _numDirtyCards; 698 size_t _sweep_count; 699 // number of full gc's since the last concurrent gc. 700 uint _full_gcs_since_conc_gc; 701 702 // occupancy used for bootstrapping stats 703 double _bootstrap_occupancy; 704 705 // timer 706 elapsedTimer _timer; 707 708 // Timing, allocation and promotion statistics, used for scheduling. 709 CMSStats _stats; 710 711 // Allocation limits installed in the young gen, used only in 712 // CMSIncrementalMode. When an allocation in the young gen would cross one of 713 // these limits, the cms generation is notified and the cms thread is started 714 // or stopped, respectively. 715 HeapWord* _icms_start_limit; 716 HeapWord* _icms_stop_limit; 717 718 enum CMS_op_type { 719 CMS_op_checkpointRootsInitial, 720 CMS_op_checkpointRootsFinal 721 }; 722 723 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 724 bool stop_world_and_do(CMS_op_type op); 725 726 OopTaskQueueSet* task_queues() { return _task_queues; } 727 int* hash_seed(int i) { return &_hash_seed[i]; } 728 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 729 730 // Support for parallelizing Eden rescan in CMS remark phase 731 void sample_eden(); // ... sample Eden space top 732 733 private: 734 // Support for parallelizing young gen rescan in CMS remark phase 735 Generation* _young_gen; // the younger gen 736 HeapWord** _top_addr; // ... Top of Eden 737 HeapWord** _end_addr; // ... End of Eden 738 HeapWord** _eden_chunk_array; // ... Eden partitioning array 739 size_t _eden_chunk_index; // ... top (exclusive) of array 740 size_t _eden_chunk_capacity; // ... max entries in array 741 742 // Support for parallelizing survivor space rescan 743 HeapWord** _survivor_chunk_array; 744 size_t _survivor_chunk_index; 745 size_t _survivor_chunk_capacity; 746 size_t* _cursor; 747 ChunkArray* _survivor_plab_array; 748 749 // Support for marking stack overflow handling 750 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 751 bool par_take_from_overflow_list(size_t num, 752 OopTaskQueue* to_work_q, 753 int no_of_gc_threads); 754 void push_on_overflow_list(oop p); 755 void par_push_on_overflow_list(oop p); 756 // the following is, obviously, not, in general, "MT-stable" 757 bool overflow_list_is_empty() const; 758 759 void preserve_mark_if_necessary(oop p); 760 void par_preserve_mark_if_necessary(oop p); 761 void preserve_mark_work(oop p, markOop m); 762 void restore_preserved_marks_if_any(); 763 NOT_PRODUCT(bool no_preserved_marks() const;) 764 // in support of testing overflow code 765 NOT_PRODUCT(int _overflow_counter;) 766 NOT_PRODUCT(bool simulate_overflow();) // sequential 767 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 768 769 // CMS work methods 770 void checkpointRootsInitialWork(bool asynch); // initial checkpoint work 771 772 // a return value of false indicates failure due to stack overflow 773 bool markFromRootsWork(bool asynch); // concurrent marking work 774 775 public: // FIX ME!!! only for testing 776 bool do_marking_st(bool asynch); // single-threaded marking 777 bool do_marking_mt(bool asynch); // multi-threaded marking 778 779 private: 780 781 // concurrent precleaning work 782 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, 783 ScanMarkedObjectsAgainCarefullyClosure* cl); 784 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, 785 ScanMarkedObjectsAgainCarefullyClosure* cl); 786 // Does precleaning work, returning a quantity indicative of 787 // the amount of "useful work" done. 788 size_t preclean_work(bool clean_refs, bool clean_survivors); 789 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 790 void abortable_preclean(); // Preclean while looking for possible abort 791 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 792 // Helper function for above; merge-sorts the per-thread plab samples 793 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 794 // Resets (i.e. clears) the per-thread plab sample vectors 795 void reset_survivor_plab_arrays(); 796 797 // final (second) checkpoint work 798 void checkpointRootsFinalWork(bool asynch, bool clear_all_soft_refs, 799 bool init_mark_was_synchronous); 800 // work routine for parallel version of remark 801 void do_remark_parallel(); 802 // work routine for non-parallel version of remark 803 void do_remark_non_parallel(); 804 // reference processing work routine (during second checkpoint) 805 void refProcessingWork(bool asynch, bool clear_all_soft_refs); 806 807 // concurrent sweeping work 808 void sweepWork(ConcurrentMarkSweepGeneration* gen, bool asynch); 809 810 // (concurrent) resetting of support data structures 811 void reset(bool asynch); 812 813 // Clear _expansion_cause fields of constituent generations 814 void clear_expansion_cause(); 815 816 // An auxilliary method used to record the ends of 817 // used regions of each generation to limit the extent of sweep 818 void save_sweep_limits(); 819 820 // A work method used by foreground collection to determine 821 // what type of collection (compacting or not, continuing or fresh) 822 // it should do. 823 void decide_foreground_collection_type(bool clear_all_soft_refs, 824 bool* should_compact, bool* should_start_over); 825 826 // A work method used by the foreground collector to do 827 // a mark-sweep-compact. 828 void do_compaction_work(bool clear_all_soft_refs); 829 830 // A work method used by the foreground collector to do 831 // a mark-sweep, after taking over from a possibly on-going 832 // concurrent mark-sweep collection. 833 void do_mark_sweep_work(bool clear_all_soft_refs, 834 CollectorState first_state, bool should_start_over); 835 836 // If the backgrould GC is active, acquire control from the background 837 // GC and do the collection. 838 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 839 840 // For synchronizing passing of control from background to foreground 841 // GC. waitForForegroundGC() is called by the background 842 // collector. It if had to wait for a foreground collection, 843 // it returns true and the background collection should assume 844 // that the collection was finished by the foreground 845 // collector. 846 bool waitForForegroundGC(); 847 848 // Incremental mode triggering: recompute the icms duty cycle and set the 849 // allocation limits in the young gen. 850 void icms_update_allocation_limits(); 851 852 size_t block_size_using_printezis_bits(HeapWord* addr) const; 853 size_t block_size_if_printezis_bits(HeapWord* addr) const; 854 HeapWord* next_card_start_after_block(HeapWord* addr) const; 855 856 void setup_cms_unloading_and_verification_state(); 857 public: 858 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 859 CardTableRS* ct, 860 ConcurrentMarkSweepPolicy* cp); 861 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 862 863 ReferenceProcessor* ref_processor() { return _ref_processor; } 864 void ref_processor_init(); 865 866 Mutex* bitMapLock() const { return _markBitMap.lock(); } 867 static CollectorState abstract_state() { return _collectorState; } 868 869 bool should_abort_preclean() const; // Whether preclean should be aborted. 870 size_t get_eden_used() const; 871 size_t get_eden_capacity() const; 872 873 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 874 875 // locking checks 876 NOT_PRODUCT(static bool have_cms_token();) 877 878 // XXXPERM bool should_collect(bool full, size_t size, bool tlab); 879 bool shouldConcurrentCollect(); 880 881 void collect(bool full, 882 bool clear_all_soft_refs, 883 size_t size, 884 bool tlab); 885 void collect_in_background(bool clear_all_soft_refs); 886 void collect_in_foreground(bool clear_all_soft_refs); 887 888 // In support of ExplicitGCInvokesConcurrent 889 static void request_full_gc(unsigned int full_gc_count); 890 // Should we unload classes in a particular concurrent cycle? 891 bool should_unload_classes() const { 892 return _should_unload_classes; 893 } 894 void update_should_unload_classes(); 895 896 void direct_allocated(HeapWord* start, size_t size); 897 898 // Object is dead if not marked and current phase is sweeping. 899 bool is_dead_obj(oop obj) const; 900 901 // After a promotion (of "start"), do any necessary marking. 902 // If "par", then it's being done by a parallel GC thread. 903 // The last two args indicate if we need precise marking 904 // and if so the size of the object so it can be dirtied 905 // in its entirety. 906 void promoted(bool par, HeapWord* start, 907 bool is_obj_array, size_t obj_size); 908 909 HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 910 size_t word_size); 911 912 void getFreelistLocks() const; 913 void releaseFreelistLocks() const; 914 bool haveFreelistLocks() const; 915 916 // Adjust size of underlying generation 917 void compute_new_size(); 918 919 // GC prologue and epilogue 920 void gc_prologue(bool full); 921 void gc_epilogue(bool full); 922 923 jlong time_of_last_gc(jlong now) { 924 if (_collectorState <= Idling) { 925 // gc not in progress 926 return _time_of_last_gc; 927 } else { 928 // collection in progress 929 return now; 930 } 931 } 932 933 // Support for parallel remark of survivor space 934 void* get_data_recorder(int thr_num); 935 936 CMSBitMap* markBitMap() { return &_markBitMap; } 937 void directAllocated(HeapWord* start, size_t size); 938 939 // main CMS steps and related support 940 void checkpointRootsInitial(bool asynch); 941 bool markFromRoots(bool asynch); // a return value of false indicates failure 942 // due to stack overflow 943 void preclean(); 944 void checkpointRootsFinal(bool asynch, bool clear_all_soft_refs, 945 bool init_mark_was_synchronous); 946 void sweep(bool asynch); 947 948 // Check that the currently executing thread is the expected 949 // one (foreground collector or background collector). 950 static void check_correct_thread_executing() PRODUCT_RETURN; 951 // XXXPERM void print_statistics() PRODUCT_RETURN; 952 953 bool is_cms_reachable(HeapWord* addr); 954 955 // Performance Counter Support 956 CollectorCounters* counters() { return _gc_counters; } 957 958 // timer stuff 959 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 960 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 961 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 962 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } 963 964 int yields() { return _numYields; } 965 void resetYields() { _numYields = 0; } 966 void incrementYields() { _numYields++; } 967 void resetNumDirtyCards() { _numDirtyCards = 0; } 968 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 969 size_t numDirtyCards() { return _numDirtyCards; } 970 971 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 972 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 973 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 974 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 975 size_t sweep_count() const { return _sweep_count; } 976 void increment_sweep_count() { _sweep_count++; } 977 978 // Timers/stats for gc scheduling and incremental mode pacing. 979 CMSStats& stats() { return _stats; } 980 981 // Convenience methods that check whether CMSIncrementalMode is enabled and 982 // forward to the corresponding methods in ConcurrentMarkSweepThread. 983 static void start_icms(); 984 static void stop_icms(); // Called at the end of the cms cycle. 985 static void disable_icms(); // Called before a foreground collection. 986 static void enable_icms(); // Called after a foreground collection. 987 void icms_wait(); // Called at yield points. 988 989 // Adaptive size policy 990 CMSAdaptiveSizePolicy* size_policy(); 991 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters(); 992 993 static void print_on_error(outputStream* st); 994 995 // debugging 996 void verify(); 997 bool verify_after_remark(bool silent = VerifySilently); 998 void verify_ok_to_terminate() const PRODUCT_RETURN; 999 void verify_work_stacks_empty() const PRODUCT_RETURN; 1000 void verify_overflow_empty() const PRODUCT_RETURN; 1001 1002 // convenience methods in support of debugging 1003 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 1004 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 1005 1006 // accessors 1007 CMSMarkStack* verification_mark_stack() { return &_markStack; } 1008 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 1009 1010 // Initialization errors 1011 bool completed_initialization() { return _completed_initialization; } 1012 }; 1013 1014 class CMSExpansionCause : public AllStatic { 1015 public: 1016 enum Cause { 1017 _no_expansion, 1018 _satisfy_free_ratio, 1019 _satisfy_promotion, 1020 _satisfy_allocation, 1021 _allocate_par_lab, 1022 _allocate_par_spooling_space, 1023 _adaptive_size_policy 1024 }; 1025 // Return a string describing the cause of the expansion. 1026 static const char* to_string(CMSExpansionCause::Cause cause); 1027 }; 1028 1029 class ConcurrentMarkSweepGeneration: public CardGeneration { 1030 friend class VMStructs; 1031 friend class ConcurrentMarkSweepThread; 1032 friend class ConcurrentMarkSweep; 1033 friend class CMSCollector; 1034 protected: 1035 static CMSCollector* _collector; // the collector that collects us 1036 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1037 1038 // Performance Counters 1039 GenerationCounters* _gen_counters; 1040 GSpaceCounters* _space_counters; 1041 1042 // Words directly allocated, used by CMSStats. 1043 size_t _direct_allocated_words; 1044 1045 // Non-product stat counters 1046 NOT_PRODUCT( 1047 size_t _numObjectsPromoted; 1048 size_t _numWordsPromoted; 1049 size_t _numObjectsAllocated; 1050 size_t _numWordsAllocated; 1051 ) 1052 1053 // Used for sizing decisions 1054 bool _incremental_collection_failed; 1055 bool incremental_collection_failed() { 1056 return _incremental_collection_failed; 1057 } 1058 void set_incremental_collection_failed() { 1059 _incremental_collection_failed = true; 1060 } 1061 void clear_incremental_collection_failed() { 1062 _incremental_collection_failed = false; 1063 } 1064 1065 // accessors 1066 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1067 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1068 1069 private: 1070 // For parallel young-gen GC support. 1071 CMSParGCThreadState** _par_gc_thread_states; 1072 1073 // Reason generation was expanded 1074 CMSExpansionCause::Cause _expansion_cause; 1075 1076 // In support of MinChunkSize being larger than min object size 1077 const double _dilatation_factor; 1078 1079 enum CollectionTypes { 1080 Concurrent_collection_type = 0, 1081 MS_foreground_collection_type = 1, 1082 MSC_foreground_collection_type = 2, 1083 Unknown_collection_type = 3 1084 }; 1085 1086 CollectionTypes _debug_collection_type; 1087 1088 // True if a compactiing collection was done. 1089 bool _did_compact; 1090 bool did_compact() { return _did_compact; } 1091 1092 // Fraction of current occupancy at which to start a CMS collection which 1093 // will collect this generation (at least). 1094 double _initiating_occupancy; 1095 1096 protected: 1097 // Shrink generation by specified size (returns false if unable to shrink) 1098 void shrink_free_list_by(size_t bytes); 1099 1100 // Update statistics for GC 1101 virtual void update_gc_stats(int level, bool full); 1102 1103 // Maximum available space in the generation (including uncommitted) 1104 // space. 1105 size_t max_available() const; 1106 1107 // getter and initializer for _initiating_occupancy field. 1108 double initiating_occupancy() const { return _initiating_occupancy; } 1109 void init_initiating_occupancy(intx io, uintx tr); 1110 1111 public: 1112 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1113 int level, CardTableRS* ct, 1114 bool use_adaptive_freelists, 1115 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 1116 1117 // Accessors 1118 CMSCollector* collector() const { return _collector; } 1119 static void set_collector(CMSCollector* collector) { 1120 assert(_collector == NULL, "already set"); 1121 _collector = collector; 1122 } 1123 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1124 1125 Mutex* freelistLock() const; 1126 1127 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1128 1129 // Adaptive size policy 1130 CMSAdaptiveSizePolicy* size_policy(); 1131 1132 void set_did_compact(bool v) { _did_compact = v; } 1133 1134 bool refs_discovery_is_atomic() const { return false; } 1135 bool refs_discovery_is_mt() const { 1136 // Note: CMS does MT-discovery during the parallel-remark 1137 // phases. Use ReferenceProcessorMTMutator to make refs 1138 // discovery MT-safe during such phases or other parallel 1139 // discovery phases in the future. This may all go away 1140 // if/when we decide that refs discovery is sufficiently 1141 // rare that the cost of the CAS's involved is in the 1142 // noise. That's a measurement that should be done, and 1143 // the code simplified if that turns out to be the case. 1144 return ConcGCThreads > 1; 1145 } 1146 1147 // Override 1148 virtual void ref_processor_init(); 1149 1150 // Grow generation by specified size (returns false if unable to grow) 1151 bool grow_by(size_t bytes); 1152 // Grow generation to reserved size. 1153 bool grow_to_reserved(); 1154 1155 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1156 1157 // Space enquiries 1158 size_t capacity() const; 1159 size_t used() const; 1160 size_t free() const; 1161 double occupancy() const { return ((double)used())/((double)capacity()); } 1162 size_t contiguous_available() const; 1163 size_t unsafe_max_alloc_nogc() const; 1164 1165 // over-rides 1166 MemRegion used_region() const; 1167 MemRegion used_region_at_save_marks() const; 1168 1169 // Does a "full" (forced) collection invoked on this generation collect 1170 // all younger generations as well? Note that the second conjunct is a 1171 // hack to allow the collection of the younger gen first if the flag is 1172 // set. This is better than using th policy's should_collect_gen0_first() 1173 // since that causes us to do an extra unnecessary pair of restart-&-stop-world. 1174 virtual bool full_collects_younger_generations() const { 1175 return UseCMSCompactAtFullCollection && !CollectGen0First; 1176 } 1177 1178 void space_iterate(SpaceClosure* blk, bool usedOnly = false); 1179 1180 // Support for compaction 1181 CompactibleSpace* first_compaction_space() const; 1182 // Adjust quantites in the generation affected by 1183 // the compaction. 1184 void reset_after_compaction(); 1185 1186 // Allocation support 1187 HeapWord* allocate(size_t size, bool tlab); 1188 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1189 oop promote(oop obj, size_t obj_size); 1190 HeapWord* par_allocate(size_t size, bool tlab) { 1191 return allocate(size, tlab); 1192 } 1193 1194 // Incremental mode triggering. 1195 HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 1196 size_t word_size); 1197 1198 // Used by CMSStats to track direct allocation. The value is sampled and 1199 // reset after each young gen collection. 1200 size_t direct_allocated_words() const { return _direct_allocated_words; } 1201 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1202 1203 // Overrides for parallel promotion. 1204 virtual oop par_promote(int thread_num, 1205 oop obj, markOop m, size_t word_sz); 1206 // This one should not be called for CMS. 1207 virtual void par_promote_alloc_undo(int thread_num, 1208 HeapWord* obj, size_t word_sz); 1209 virtual void par_promote_alloc_done(int thread_num); 1210 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1211 1212 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1213 1214 // Inform this (non-young) generation that a promotion failure was 1215 // encountered during a collection of a younger generation that 1216 // promotes into this generation. 1217 virtual void promotion_failure_occurred(); 1218 1219 bool should_collect(bool full, size_t size, bool tlab); 1220 virtual bool should_concurrent_collect() const; 1221 virtual bool is_too_full() const; 1222 void collect(bool full, 1223 bool clear_all_soft_refs, 1224 size_t size, 1225 bool tlab); 1226 1227 HeapWord* expand_and_allocate(size_t word_size, 1228 bool tlab, 1229 bool parallel = false); 1230 1231 // GC prologue and epilogue 1232 void gc_prologue(bool full); 1233 void gc_prologue_work(bool full, bool registerClosure, 1234 ModUnionClosure* modUnionClosure); 1235 void gc_epilogue(bool full); 1236 void gc_epilogue_work(bool full); 1237 1238 // Time since last GC of this generation 1239 jlong time_of_last_gc(jlong now) { 1240 return collector()->time_of_last_gc(now); 1241 } 1242 void update_time_of_last_gc(jlong now) { 1243 collector()-> update_time_of_last_gc(now); 1244 } 1245 1246 // Allocation failure 1247 void expand(size_t bytes, size_t expand_bytes, 1248 CMSExpansionCause::Cause cause); 1249 virtual bool expand(size_t bytes, size_t expand_bytes); 1250 void shrink(size_t bytes); 1251 void shrink_by(size_t bytes); 1252 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1253 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1254 1255 // Iteration support and related enquiries 1256 void save_marks(); 1257 bool no_allocs_since_save_marks(); 1258 void object_iterate_since_last_GC(ObjectClosure* cl); 1259 void younger_refs_iterate(OopsInGenClosure* cl); 1260 1261 // Iteration support specific to CMS generations 1262 void save_sweep_limit(); 1263 1264 // More iteration support 1265 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); 1266 virtual void oop_iterate(ExtendedOopClosure* cl); 1267 virtual void safe_object_iterate(ObjectClosure* cl); 1268 virtual void object_iterate(ObjectClosure* cl); 1269 1270 // Need to declare the full complement of closures, whether we'll 1271 // override them or not, or get message from the compiler: 1272 // oop_since_save_marks_iterate_nv hides virtual function... 1273 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1274 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1275 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1276 1277 // Smart allocation XXX -- move to CFLSpace? 1278 void setNearLargestChunk(); 1279 bool isNearLargestChunk(HeapWord* addr); 1280 1281 // Get the chunk at the end of the space. Delagates to 1282 // the space. 1283 FreeChunk* find_chunk_at_end(); 1284 1285 void post_compact(); 1286 1287 // Debugging 1288 void prepare_for_verify(); 1289 void verify(); 1290 void print_statistics() PRODUCT_RETURN; 1291 1292 // Performance Counters support 1293 virtual void update_counters(); 1294 virtual void update_counters(size_t used); 1295 void initialize_performance_counters(); 1296 CollectorCounters* counters() { return collector()->counters(); } 1297 1298 // Support for parallel remark of survivor space 1299 void* get_data_recorder(int thr_num) { 1300 //Delegate to collector 1301 return collector()->get_data_recorder(thr_num); 1302 } 1303 1304 // Printing 1305 const char* name() const; 1306 virtual const char* short_name() const { return "CMS"; } 1307 void print() const; 1308 void printOccupancy(const char* s); 1309 bool must_be_youngest() const { return false; } 1310 bool must_be_oldest() const { return true; } 1311 1312 // Resize the generation after a compacting GC. The 1313 // generation can be treated as a contiguous space 1314 // after the compaction. 1315 virtual void compute_new_size(); 1316 // Resize the generation after a non-compacting 1317 // collection. 1318 void compute_new_size_free_list(); 1319 1320 CollectionTypes debug_collection_type() { return _debug_collection_type; } 1321 void rotate_debug_collection_type(); 1322 }; 1323 1324 class ASConcurrentMarkSweepGeneration : public ConcurrentMarkSweepGeneration { 1325 1326 // Return the size policy from the heap's collector 1327 // policy casted to CMSAdaptiveSizePolicy*. 1328 CMSAdaptiveSizePolicy* cms_size_policy() const; 1329 1330 // Resize the generation based on the adaptive size 1331 // policy. 1332 void resize(size_t cur_promo, size_t desired_promo); 1333 1334 // Return the GC counters from the collector policy 1335 CMSGCAdaptivePolicyCounters* gc_adaptive_policy_counters(); 1336 1337 virtual void shrink_by(size_t bytes); 1338 1339 public: 1340 ASConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1341 int level, CardTableRS* ct, 1342 bool use_adaptive_freelists, 1343 FreeBlockDictionary<FreeChunk>::DictionaryChoice 1344 dictionaryChoice) : 1345 ConcurrentMarkSweepGeneration(rs, initial_byte_size, level, ct, 1346 use_adaptive_freelists, dictionaryChoice) {} 1347 1348 virtual const char* short_name() const { return "ASCMS"; } 1349 virtual Generation::Name kind() { return Generation::ASConcurrentMarkSweep; } 1350 1351 virtual void update_counters(); 1352 virtual void update_counters(size_t used); 1353 }; 1354 1355 // 1356 // Closures of various sorts used by CMS to accomplish its work 1357 // 1358 1359 // This closure is used to check that a certain set of oops is empty. 1360 class FalseClosure: public OopClosure { 1361 public: 1362 void do_oop(oop* p) { guarantee(false, "Should be an empty set"); } 1363 void do_oop(narrowOop* p) { guarantee(false, "Should be an empty set"); } 1364 }; 1365 1366 // This closure is used to do concurrent marking from the roots 1367 // following the first checkpoint. 1368 class MarkFromRootsClosure: public BitMapClosure { 1369 CMSCollector* _collector; 1370 MemRegion _span; 1371 CMSBitMap* _bitMap; 1372 CMSBitMap* _mut; 1373 CMSMarkStack* _markStack; 1374 bool _yield; 1375 int _skipBits; 1376 HeapWord* _finger; 1377 HeapWord* _threshold; 1378 DEBUG_ONLY(bool _verifying;) 1379 1380 public: 1381 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1382 CMSBitMap* bitMap, 1383 CMSMarkStack* markStack, 1384 bool should_yield, bool verifying = false); 1385 bool do_bit(size_t offset); 1386 void reset(HeapWord* addr); 1387 inline void do_yield_check(); 1388 1389 private: 1390 void scanOopsInOop(HeapWord* ptr); 1391 void do_yield_work(); 1392 }; 1393 1394 // This closure is used to do concurrent multi-threaded 1395 // marking from the roots following the first checkpoint. 1396 // XXX This should really be a subclass of The serial version 1397 // above, but i have not had the time to refactor things cleanly. 1398 // That willbe done for Dolphin. 1399 class Par_MarkFromRootsClosure: public BitMapClosure { 1400 CMSCollector* _collector; 1401 MemRegion _whole_span; 1402 MemRegion _span; 1403 CMSBitMap* _bit_map; 1404 CMSBitMap* _mut; 1405 OopTaskQueue* _work_queue; 1406 CMSMarkStack* _overflow_stack; 1407 bool _yield; 1408 int _skip_bits; 1409 HeapWord* _finger; 1410 HeapWord* _threshold; 1411 CMSConcMarkingTask* _task; 1412 public: 1413 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1414 MemRegion span, 1415 CMSBitMap* bit_map, 1416 OopTaskQueue* work_queue, 1417 CMSMarkStack* overflow_stack, 1418 bool should_yield); 1419 bool do_bit(size_t offset); 1420 inline void do_yield_check(); 1421 1422 private: 1423 void scan_oops_in_oop(HeapWord* ptr); 1424 void do_yield_work(); 1425 bool get_work_from_overflow_stack(); 1426 }; 1427 1428 // The following closures are used to do certain kinds of verification of 1429 // CMS marking. 1430 class PushAndMarkVerifyClosure: public CMSOopClosure { 1431 CMSCollector* _collector; 1432 MemRegion _span; 1433 CMSBitMap* _verification_bm; 1434 CMSBitMap* _cms_bm; 1435 CMSMarkStack* _mark_stack; 1436 protected: 1437 void do_oop(oop p); 1438 template <class T> inline void do_oop_work(T *p) { 1439 oop obj = oopDesc::load_decode_heap_oop(p); 1440 do_oop(obj); 1441 } 1442 public: 1443 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1444 MemRegion span, 1445 CMSBitMap* verification_bm, 1446 CMSBitMap* cms_bm, 1447 CMSMarkStack* mark_stack); 1448 void do_oop(oop* p); 1449 void do_oop(narrowOop* p); 1450 1451 // Deal with a stack overflow condition 1452 void handle_stack_overflow(HeapWord* lost); 1453 }; 1454 1455 class MarkFromRootsVerifyClosure: public BitMapClosure { 1456 CMSCollector* _collector; 1457 MemRegion _span; 1458 CMSBitMap* _verification_bm; 1459 CMSBitMap* _cms_bm; 1460 CMSMarkStack* _mark_stack; 1461 HeapWord* _finger; 1462 PushAndMarkVerifyClosure _pam_verify_closure; 1463 public: 1464 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1465 CMSBitMap* verification_bm, 1466 CMSBitMap* cms_bm, 1467 CMSMarkStack* mark_stack); 1468 bool do_bit(size_t offset); 1469 void reset(HeapWord* addr); 1470 }; 1471 1472 1473 // This closure is used to check that a certain set of bits is 1474 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1475 class FalseBitMapClosure: public BitMapClosure { 1476 public: 1477 bool do_bit(size_t offset) { 1478 guarantee(false, "Should not have a 1 bit"); 1479 return true; 1480 } 1481 }; 1482 1483 // This closure is used during the second checkpointing phase 1484 // to rescan the marked objects on the dirty cards in the mod 1485 // union table and the card table proper. It's invoked via 1486 // MarkFromDirtyCardsClosure below. It uses either 1487 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1488 // declared in genOopClosures.hpp to accomplish some of its work. 1489 // In the parallel case the bitMap is shared, so access to 1490 // it needs to be suitably synchronized for updates by embedded 1491 // closures that update it; however, this closure itself only 1492 // reads the bit_map and because it is idempotent, is immune to 1493 // reading stale values. 1494 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1495 #ifdef ASSERT 1496 CMSCollector* _collector; 1497 MemRegion _span; 1498 union { 1499 CMSMarkStack* _mark_stack; 1500 OopTaskQueue* _work_queue; 1501 }; 1502 #endif // ASSERT 1503 bool _parallel; 1504 CMSBitMap* _bit_map; 1505 union { 1506 MarkRefsIntoAndScanClosure* _scan_closure; 1507 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1508 }; 1509 1510 public: 1511 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1512 MemRegion span, 1513 ReferenceProcessor* rp, 1514 CMSBitMap* bit_map, 1515 CMSMarkStack* mark_stack, 1516 MarkRefsIntoAndScanClosure* cl): 1517 #ifdef ASSERT 1518 _collector(collector), 1519 _span(span), 1520 _mark_stack(mark_stack), 1521 #endif // ASSERT 1522 _parallel(false), 1523 _bit_map(bit_map), 1524 _scan_closure(cl) { } 1525 1526 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1527 MemRegion span, 1528 ReferenceProcessor* rp, 1529 CMSBitMap* bit_map, 1530 OopTaskQueue* work_queue, 1531 Par_MarkRefsIntoAndScanClosure* cl): 1532 #ifdef ASSERT 1533 _collector(collector), 1534 _span(span), 1535 _work_queue(work_queue), 1536 #endif // ASSERT 1537 _parallel(true), 1538 _bit_map(bit_map), 1539 _par_scan_closure(cl) { } 1540 1541 void do_object(oop obj) { 1542 guarantee(false, "Call do_object_b(oop, MemRegion) instead"); 1543 } 1544 bool do_object_b(oop obj) { 1545 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1546 return false; 1547 } 1548 bool do_object_bm(oop p, MemRegion mr); 1549 }; 1550 1551 // This closure is used during the second checkpointing phase 1552 // to rescan the marked objects on the dirty cards in the mod 1553 // union table and the card table proper. It invokes 1554 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1555 // In the parallel case, the bit map is shared and requires 1556 // synchronized access. 1557 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1558 CompactibleFreeListSpace* _space; 1559 ScanMarkedObjectsAgainClosure _scan_cl; 1560 size_t _num_dirty_cards; 1561 1562 public: 1563 MarkFromDirtyCardsClosure(CMSCollector* collector, 1564 MemRegion span, 1565 CompactibleFreeListSpace* space, 1566 CMSBitMap* bit_map, 1567 CMSMarkStack* mark_stack, 1568 MarkRefsIntoAndScanClosure* cl): 1569 _space(space), 1570 _num_dirty_cards(0), 1571 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1572 mark_stack, cl) { } 1573 1574 MarkFromDirtyCardsClosure(CMSCollector* collector, 1575 MemRegion span, 1576 CompactibleFreeListSpace* space, 1577 CMSBitMap* bit_map, 1578 OopTaskQueue* work_queue, 1579 Par_MarkRefsIntoAndScanClosure* cl): 1580 _space(space), 1581 _num_dirty_cards(0), 1582 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1583 work_queue, cl) { } 1584 1585 void do_MemRegion(MemRegion mr); 1586 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1587 size_t num_dirty_cards() { return _num_dirty_cards; } 1588 }; 1589 1590 // This closure is used in the non-product build to check 1591 // that there are no MemRegions with a certain property. 1592 class FalseMemRegionClosure: public MemRegionClosure { 1593 void do_MemRegion(MemRegion mr) { 1594 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1595 guarantee(false, "Should never be here"); 1596 } 1597 }; 1598 1599 // This closure is used during the precleaning phase 1600 // to "carefully" rescan marked objects on dirty cards. 1601 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1602 // to accomplish some of its work. 1603 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1604 CMSCollector* _collector; 1605 MemRegion _span; 1606 bool _yield; 1607 Mutex* _freelistLock; 1608 CMSBitMap* _bitMap; 1609 CMSMarkStack* _markStack; 1610 MarkRefsIntoAndScanClosure* _scanningClosure; 1611 1612 public: 1613 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1614 MemRegion span, 1615 CMSBitMap* bitMap, 1616 CMSMarkStack* markStack, 1617 MarkRefsIntoAndScanClosure* cl, 1618 bool should_yield): 1619 _collector(collector), 1620 _span(span), 1621 _yield(should_yield), 1622 _bitMap(bitMap), 1623 _markStack(markStack), 1624 _scanningClosure(cl) { 1625 } 1626 1627 void do_object(oop p) { 1628 guarantee(false, "call do_object_careful instead"); 1629 } 1630 1631 size_t do_object_careful(oop p) { 1632 guarantee(false, "Unexpected caller"); 1633 return 0; 1634 } 1635 1636 size_t do_object_careful_m(oop p, MemRegion mr); 1637 1638 void setFreelistLock(Mutex* m) { 1639 _freelistLock = m; 1640 _scanningClosure->set_freelistLock(m); 1641 } 1642 1643 private: 1644 inline bool do_yield_check(); 1645 1646 void do_yield_work(); 1647 }; 1648 1649 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1650 CMSCollector* _collector; 1651 MemRegion _span; 1652 bool _yield; 1653 CMSBitMap* _bit_map; 1654 CMSMarkStack* _mark_stack; 1655 PushAndMarkClosure* _scanning_closure; 1656 unsigned int _before_count; 1657 1658 public: 1659 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1660 MemRegion span, 1661 CMSBitMap* bit_map, 1662 CMSMarkStack* mark_stack, 1663 PushAndMarkClosure* cl, 1664 unsigned int before_count, 1665 bool should_yield): 1666 _collector(collector), 1667 _span(span), 1668 _yield(should_yield), 1669 _bit_map(bit_map), 1670 _mark_stack(mark_stack), 1671 _scanning_closure(cl), 1672 _before_count(before_count) 1673 { } 1674 1675 void do_object(oop p) { 1676 guarantee(false, "call do_object_careful instead"); 1677 } 1678 1679 size_t do_object_careful(oop p); 1680 1681 size_t do_object_careful_m(oop p, MemRegion mr) { 1682 guarantee(false, "Unexpected caller"); 1683 return 0; 1684 } 1685 1686 private: 1687 inline void do_yield_check(); 1688 void do_yield_work(); 1689 }; 1690 1691 // This closure is used to accomplish the sweeping work 1692 // after the second checkpoint but before the concurrent reset 1693 // phase. 1694 // 1695 // Terminology 1696 // left hand chunk (LHC) - block of one or more chunks currently being 1697 // coalesced. The LHC is available for coalescing with a new chunk. 1698 // right hand chunk (RHC) - block that is currently being swept that is 1699 // free or garbage that can be coalesced with the LHC. 1700 // _inFreeRange is true if there is currently a LHC 1701 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1702 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1703 // _freeFinger is the address of the current LHC 1704 class SweepClosure: public BlkClosureCareful { 1705 CMSCollector* _collector; // collector doing the work 1706 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1707 CompactibleFreeListSpace* _sp; // Space being swept 1708 HeapWord* _limit;// the address at or above which the sweep should stop 1709 // because we do not expect newly garbage blocks 1710 // eligible for sweeping past that address. 1711 Mutex* _freelistLock; // Free list lock (in space) 1712 CMSBitMap* _bitMap; // Marking bit map (in 1713 // generation) 1714 bool _inFreeRange; // Indicates if we are in the 1715 // midst of a free run 1716 bool _freeRangeInFreeLists; 1717 // Often, we have just found 1718 // a free chunk and started 1719 // a new free range; we do not 1720 // eagerly remove this chunk from 1721 // the free lists unless there is 1722 // a possibility of coalescing. 1723 // When true, this flag indicates 1724 // that the _freeFinger below 1725 // points to a potentially free chunk 1726 // that may still be in the free lists 1727 bool _lastFreeRangeCoalesced; 1728 // free range contains chunks 1729 // coalesced 1730 bool _yield; 1731 // Whether sweeping should be 1732 // done with yields. For instance 1733 // when done by the foreground 1734 // collector we shouldn't yield. 1735 HeapWord* _freeFinger; // When _inFreeRange is set, the 1736 // pointer to the "left hand 1737 // chunk" 1738 size_t _freeRangeSize; 1739 // When _inFreeRange is set, this 1740 // indicates the accumulated size 1741 // of the "left hand chunk" 1742 NOT_PRODUCT( 1743 size_t _numObjectsFreed; 1744 size_t _numWordsFreed; 1745 size_t _numObjectsLive; 1746 size_t _numWordsLive; 1747 size_t _numObjectsAlreadyFree; 1748 size_t _numWordsAlreadyFree; 1749 FreeChunk* _last_fc; 1750 ) 1751 private: 1752 // Code that is common to a free chunk or garbage when 1753 // encountered during sweeping. 1754 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1755 // Process a free chunk during sweeping. 1756 void do_already_free_chunk(FreeChunk *fc); 1757 // Work method called when processing an already free or a 1758 // freshly garbage chunk to do a lookahead and possibly a 1759 // premptive flush if crossing over _limit. 1760 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1761 // Process a garbage chunk during sweeping. 1762 size_t do_garbage_chunk(FreeChunk *fc); 1763 // Process a live chunk during sweeping. 1764 size_t do_live_chunk(FreeChunk* fc); 1765 1766 // Accessors. 1767 HeapWord* freeFinger() const { return _freeFinger; } 1768 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1769 bool inFreeRange() const { return _inFreeRange; } 1770 void set_inFreeRange(bool v) { _inFreeRange = v; } 1771 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1772 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1773 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1774 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1775 1776 // Initialize a free range. 1777 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1778 // Return this chunk to the free lists. 1779 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1780 1781 // Check if we should yield and do so when necessary. 1782 inline void do_yield_check(HeapWord* addr); 1783 1784 // Yield 1785 void do_yield_work(HeapWord* addr); 1786 1787 // Debugging/Printing 1788 void print_free_block_coalesced(FreeChunk* fc) const; 1789 1790 public: 1791 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1792 CMSBitMap* bitMap, bool should_yield); 1793 ~SweepClosure() PRODUCT_RETURN; 1794 1795 size_t do_blk_careful(HeapWord* addr); 1796 void print() const { print_on(tty); } 1797 void print_on(outputStream *st) const; 1798 }; 1799 1800 // Closures related to weak references processing 1801 1802 // During CMS' weak reference processing, this is a 1803 // work-routine/closure used to complete transitive 1804 // marking of objects as live after a certain point 1805 // in which an initial set has been completely accumulated. 1806 // This closure is currently used both during the final 1807 // remark stop-world phase, as well as during the concurrent 1808 // precleaning of the discovered reference lists. 1809 class CMSDrainMarkingStackClosure: public VoidClosure { 1810 CMSCollector* _collector; 1811 MemRegion _span; 1812 CMSMarkStack* _mark_stack; 1813 CMSBitMap* _bit_map; 1814 CMSKeepAliveClosure* _keep_alive; 1815 bool _concurrent_precleaning; 1816 public: 1817 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1818 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1819 CMSKeepAliveClosure* keep_alive, 1820 bool cpc): 1821 _collector(collector), 1822 _span(span), 1823 _bit_map(bit_map), 1824 _mark_stack(mark_stack), 1825 _keep_alive(keep_alive), 1826 _concurrent_precleaning(cpc) { 1827 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1828 "Mismatch"); 1829 } 1830 1831 void do_void(); 1832 }; 1833 1834 // A parallel version of CMSDrainMarkingStackClosure above. 1835 class CMSParDrainMarkingStackClosure: public VoidClosure { 1836 CMSCollector* _collector; 1837 MemRegion _span; 1838 OopTaskQueue* _work_queue; 1839 CMSBitMap* _bit_map; 1840 CMSInnerParMarkAndPushClosure _mark_and_push; 1841 1842 public: 1843 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1844 MemRegion span, CMSBitMap* bit_map, 1845 OopTaskQueue* work_queue): 1846 _collector(collector), 1847 _span(span), 1848 _bit_map(bit_map), 1849 _work_queue(work_queue), 1850 _mark_and_push(collector, span, bit_map, work_queue) { } 1851 1852 public: 1853 void trim_queue(uint max); 1854 void do_void(); 1855 }; 1856 1857 // Allow yielding or short-circuiting of reference list 1858 // prelceaning work. 1859 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1860 CMSCollector* _collector; 1861 void do_yield_work(); 1862 public: 1863 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1864 _collector(collector) {} 1865 virtual bool should_return(); 1866 }; 1867 1868 1869 // Convenience class that locks free list locks for given CMS collector 1870 class FreelistLocker: public StackObj { 1871 private: 1872 CMSCollector* _collector; 1873 public: 1874 FreelistLocker(CMSCollector* collector): 1875 _collector(collector) { 1876 _collector->getFreelistLocks(); 1877 } 1878 1879 ~FreelistLocker() { 1880 _collector->releaseFreelistLocks(); 1881 } 1882 }; 1883 1884 // Mark all dead objects in a given space. 1885 class MarkDeadObjectsClosure: public BlkClosure { 1886 const CMSCollector* _collector; 1887 const CompactibleFreeListSpace* _sp; 1888 CMSBitMap* _live_bit_map; 1889 CMSBitMap* _dead_bit_map; 1890 public: 1891 MarkDeadObjectsClosure(const CMSCollector* collector, 1892 const CompactibleFreeListSpace* sp, 1893 CMSBitMap *live_bit_map, 1894 CMSBitMap *dead_bit_map) : 1895 _collector(collector), 1896 _sp(sp), 1897 _live_bit_map(live_bit_map), 1898 _dead_bit_map(dead_bit_map) {} 1899 size_t do_blk(HeapWord* addr); 1900 }; 1901 1902 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1903 1904 public: 1905 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1906 }; 1907 1908 1909 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP