1 /* 2 * Copyright (c) 2001, 2015, 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/concurrentMarkSweep/cmsOopClosures.hpp" 29 #include "gc_implementation/shared/gcHeapSummary.hpp" 30 #include "gc_implementation/shared/gSpaceCounters.hpp" 31 #include "gc_implementation/shared/gcStats.hpp" 32 #include "gc_implementation/shared/gcWhen.hpp" 33 #include "gc_implementation/shared/generationCounters.hpp" 34 #include "memory/cardGeneration.hpp" 35 #include "memory/freeBlockDictionary.hpp" 36 #include "memory/iterator.hpp" 37 #include "memory/space.hpp" 38 #include "memory/virtualspace.hpp" 39 #include "runtime/mutexLocker.hpp" 40 #include "services/memoryService.hpp" 41 #include "utilities/bitMap.hpp" 42 #include "utilities/stack.hpp" 43 #include "utilities/taskqueue.hpp" 44 #include "utilities/yieldingWorkgroup.hpp" 45 46 // ConcurrentMarkSweepGeneration is in support of a concurrent 47 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker 48 // style. We assume, for now, that this generation is always the 49 // seniormost generation and for simplicity 50 // in the first implementation, that this generation is a single compactible 51 // space. Neither of these restrictions appears essential, and will be 52 // relaxed in the future when more time is available to implement the 53 // greater generality (and there's a need for it). 54 // 55 // Concurrent mode failures are currently handled by 56 // means of a sliding mark-compact. 57 58 class AdaptiveSizePolicy; 59 class CMSCollector; 60 class CMSConcMarkingTask; 61 class CMSGCAdaptivePolicyCounters; 62 class CMSTracer; 63 class ConcurrentGCTimer; 64 class ConcurrentMarkSweepGeneration; 65 class ConcurrentMarkSweepPolicy; 66 class ConcurrentMarkSweepThread; 67 class CompactibleFreeListSpace; 68 class FreeChunk; 69 class ParNewGeneration; 70 class PromotionInfo; 71 class ScanMarkedObjectsAgainCarefullyClosure; 72 class TenuredGeneration; 73 class SerialOldTracer; 74 75 // A generic CMS bit map. It's the basis for both the CMS marking bit map 76 // as well as for the mod union table (in each case only a subset of the 77 // methods are used). This is essentially a wrapper around the BitMap class, 78 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 79 // we have _shifter == 0. and for the mod union table we have 80 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 81 // XXX 64-bit issues in BitMap? 82 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 83 friend class VMStructs; 84 85 HeapWord* _bmStartWord; // base address of range covered by map 86 size_t _bmWordSize; // map size (in #HeapWords covered) 87 const int _shifter; // shifts to convert HeapWord to bit position 88 VirtualSpace _virtual_space; // underlying the bit map 89 BitMap _bm; // the bit map itself 90 public: 91 Mutex* const _lock; // mutex protecting _bm; 92 93 public: 94 // constructor 95 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 96 97 // allocates the actual storage for the map 98 bool allocate(MemRegion mr); 99 // field getter 100 Mutex* lock() const { return _lock; } 101 // locking verifier convenience function 102 void assert_locked() const PRODUCT_RETURN; 103 104 // inquiries 105 HeapWord* startWord() const { return _bmStartWord; } 106 size_t sizeInWords() const { return _bmWordSize; } 107 size_t sizeInBits() const { return _bm.size(); } 108 // the following is one past the last word in space 109 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 110 111 // reading marks 112 bool isMarked(HeapWord* addr) const; 113 bool par_isMarked(HeapWord* addr) const; // do not lock checks 114 bool isUnmarked(HeapWord* addr) const; 115 bool isAllClear() const; 116 117 // writing marks 118 void mark(HeapWord* addr); 119 // For marking by parallel GC threads; 120 // returns true if we did, false if another thread did 121 bool par_mark(HeapWord* addr); 122 123 void mark_range(MemRegion mr); 124 void par_mark_range(MemRegion mr); 125 void mark_large_range(MemRegion mr); 126 void par_mark_large_range(MemRegion mr); 127 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 128 void clear_range(MemRegion mr); 129 void par_clear_range(MemRegion mr); 130 void clear_large_range(MemRegion mr); 131 void par_clear_large_range(MemRegion mr); 132 void clear_all(); 133 void clear_all_incrementally(); // Not yet implemented!! 134 135 NOT_PRODUCT( 136 // checks the memory region for validity 137 void region_invariant(MemRegion mr); 138 ) 139 140 // iteration 141 void iterate(BitMapClosure* cl) { 142 _bm.iterate(cl); 143 } 144 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 145 void dirty_range_iterate_clear(MemRegionClosure* cl); 146 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 147 148 // auxiliary support for iteration 149 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 150 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 151 HeapWord* end_addr) const; 152 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 153 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 154 HeapWord* end_addr) const; 155 MemRegion getAndClearMarkedRegion(HeapWord* addr); 156 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 157 HeapWord* end_addr); 158 159 // conversion utilities 160 HeapWord* offsetToHeapWord(size_t offset) const; 161 size_t heapWordToOffset(HeapWord* addr) const; 162 size_t heapWordDiffToOffsetDiff(size_t diff) const; 163 164 void print_on_error(outputStream* st, const char* prefix) const; 165 166 // debugging 167 // is this address range covered by the bit-map? 168 NOT_PRODUCT( 169 bool covers(MemRegion mr) const; 170 bool covers(HeapWord* start, size_t size = 0) const; 171 ) 172 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 173 }; 174 175 // Represents a marking stack used by the CMS collector. 176 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 177 class CMSMarkStack: public CHeapObj<mtGC> { 178 friend class CMSCollector; // To get at expansion stats further below. 179 180 VirtualSpace _virtual_space; // Space for the stack 181 oop* _base; // Bottom of stack 182 size_t _index; // One more than last occupied index 183 size_t _capacity; // Max #elements 184 Mutex _par_lock; // An advisory lock used in case of parallel access 185 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run 186 187 protected: 188 size_t _hit_limit; // We hit max stack size limit 189 size_t _failed_double; // We failed expansion before hitting limit 190 191 public: 192 CMSMarkStack(): 193 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true, 194 Monitor::_safepoint_check_never), 195 _hit_limit(0), 196 _failed_double(0) {} 197 198 bool allocate(size_t size); 199 200 size_t capacity() const { return _capacity; } 201 202 oop pop() { 203 if (!isEmpty()) { 204 return _base[--_index] ; 205 } 206 return NULL; 207 } 208 209 bool push(oop ptr) { 210 if (isFull()) { 211 return false; 212 } else { 213 _base[_index++] = ptr; 214 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 215 return true; 216 } 217 } 218 219 bool isEmpty() const { return _index == 0; } 220 bool isFull() const { 221 assert(_index <= _capacity, "buffer overflow"); 222 return _index == _capacity; 223 } 224 225 size_t length() { return _index; } 226 227 // "Parallel versions" of some of the above 228 oop par_pop() { 229 // lock and pop 230 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 231 return pop(); 232 } 233 234 bool par_push(oop ptr) { 235 // lock and push 236 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 237 return push(ptr); 238 } 239 240 // Forcibly reset the stack, losing all of its contents. 241 void reset() { 242 _index = 0; 243 } 244 245 // Expand the stack, typically in response to an overflow condition. 246 void expand(); 247 248 // Compute the least valued stack element. 249 oop least_value(HeapWord* low) { 250 oop least = (oop)low; 251 for (size_t i = 0; i < _index; i++) { 252 least = MIN2(least, _base[i]); 253 } 254 return least; 255 } 256 257 // Exposed here to allow stack expansion in || case. 258 Mutex* par_lock() { return &_par_lock; } 259 }; 260 261 class CardTableRS; 262 class CMSParGCThreadState; 263 264 class ModUnionClosure: public MemRegionClosure { 265 protected: 266 CMSBitMap* _t; 267 public: 268 ModUnionClosure(CMSBitMap* t): _t(t) { } 269 void do_MemRegion(MemRegion mr); 270 }; 271 272 class ModUnionClosurePar: public ModUnionClosure { 273 public: 274 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 275 void do_MemRegion(MemRegion mr); 276 }; 277 278 // Survivor Chunk Array in support of parallelization of 279 // Survivor Space rescan. 280 class ChunkArray: public CHeapObj<mtGC> { 281 size_t _index; 282 size_t _capacity; 283 size_t _overflows; 284 HeapWord** _array; // storage for array 285 286 public: 287 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 288 ChunkArray(HeapWord** a, size_t c): 289 _index(0), _capacity(c), _overflows(0), _array(a) {} 290 291 HeapWord** array() { return _array; } 292 void set_array(HeapWord** a) { _array = a; } 293 294 size_t capacity() { return _capacity; } 295 void set_capacity(size_t c) { _capacity = c; } 296 297 size_t end() { 298 assert(_index <= capacity(), 299 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 300 _index, _capacity)); 301 return _index; 302 } // exclusive 303 304 HeapWord* nth(size_t n) { 305 assert(n < end(), "Out of bounds access"); 306 return _array[n]; 307 } 308 309 void reset() { 310 _index = 0; 311 if (_overflows > 0 && PrintCMSStatistics > 1) { 312 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", 313 _capacity, _overflows); 314 } 315 _overflows = 0; 316 } 317 318 void record_sample(HeapWord* p, size_t sz) { 319 // For now we do not do anything with the size 320 if (_index < _capacity) { 321 _array[_index++] = p; 322 } else { 323 ++_overflows; 324 assert(_index == _capacity, 325 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 326 "): out of bounds at overflow#" SIZE_FORMAT, 327 _index, _capacity, _overflows)); 328 } 329 } 330 }; 331 332 // 333 // Timing, allocation and promotion statistics for gc scheduling and incremental 334 // mode pacing. Most statistics are exponential averages. 335 // 336 class CMSStats VALUE_OBJ_CLASS_SPEC { 337 private: 338 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 339 340 // The following are exponential averages with factor alpha: 341 // avg = (100 - alpha) * avg + alpha * cur_sample 342 // 343 // The durations measure: end_time[n] - start_time[n] 344 // The periods measure: start_time[n] - start_time[n-1] 345 // 346 // The cms period and duration include only concurrent collections; time spent 347 // in foreground cms collections due to System.gc() or because of a failure to 348 // keep up are not included. 349 // 350 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 351 // real value, but is used only after the first period. A value of 100 is 352 // used for the first sample so it gets the entire weight. 353 unsigned int _saved_alpha; // 0-100 354 unsigned int _gc0_alpha; 355 unsigned int _cms_alpha; 356 357 double _gc0_duration; 358 double _gc0_period; 359 size_t _gc0_promoted; // bytes promoted per gc0 360 double _cms_duration; 361 double _cms_duration_pre_sweep; // time from initiation to start of sweep 362 double _cms_period; 363 size_t _cms_allocated; // bytes of direct allocation per gc0 period 364 365 // Timers. 366 elapsedTimer _cms_timer; 367 TimeStamp _gc0_begin_time; 368 TimeStamp _cms_begin_time; 369 TimeStamp _cms_end_time; 370 371 // Snapshots of the amount used in the CMS generation. 372 size_t _cms_used_at_gc0_begin; 373 size_t _cms_used_at_gc0_end; 374 size_t _cms_used_at_cms_begin; 375 376 // Used to prevent the duty cycle from being reduced in the middle of a cms 377 // cycle. 378 bool _allow_duty_cycle_reduction; 379 380 enum { 381 _GC0_VALID = 0x1, 382 _CMS_VALID = 0x2, 383 _ALL_VALID = _GC0_VALID | _CMS_VALID 384 }; 385 386 unsigned int _valid_bits; 387 388 protected: 389 // In support of adjusting of cms trigger ratios based on history 390 // of concurrent mode failure. 391 double cms_free_adjustment_factor(size_t free) const; 392 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 393 394 public: 395 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 396 unsigned int alpha = CMSExpAvgFactor); 397 398 // Whether or not the statistics contain valid data; higher level statistics 399 // cannot be called until this returns true (they require at least one young 400 // gen and one cms cycle to have completed). 401 bool valid() const; 402 403 // Record statistics. 404 void record_gc0_begin(); 405 void record_gc0_end(size_t cms_gen_bytes_used); 406 void record_cms_begin(); 407 void record_cms_end(); 408 409 // Allow management of the cms timer, which must be stopped/started around 410 // yield points. 411 elapsedTimer& cms_timer() { return _cms_timer; } 412 void start_cms_timer() { _cms_timer.start(); } 413 void stop_cms_timer() { _cms_timer.stop(); } 414 415 // Basic statistics; units are seconds or bytes. 416 double gc0_period() const { return _gc0_period; } 417 double gc0_duration() const { return _gc0_duration; } 418 size_t gc0_promoted() const { return _gc0_promoted; } 419 double cms_period() const { return _cms_period; } 420 double cms_duration() const { return _cms_duration; } 421 size_t cms_allocated() const { return _cms_allocated; } 422 423 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 424 425 // Seconds since the last background cms cycle began or ended. 426 double cms_time_since_begin() const; 427 double cms_time_since_end() const; 428 429 // Higher level statistics--caller must check that valid() returns true before 430 // calling. 431 432 // Returns bytes promoted per second of wall clock time. 433 double promotion_rate() const; 434 435 // Returns bytes directly allocated per second of wall clock time. 436 double cms_allocation_rate() const; 437 438 // Rate at which space in the cms generation is being consumed (sum of the 439 // above two). 440 double cms_consumption_rate() const; 441 442 // Returns an estimate of the number of seconds until the cms generation will 443 // fill up, assuming no collection work is done. 444 double time_until_cms_gen_full() const; 445 446 // Returns an estimate of the number of seconds remaining until 447 // the cms generation collection should start. 448 double time_until_cms_start() const; 449 450 // End of higher level statistics. 451 452 // Debugging. 453 void print_on(outputStream* st) const PRODUCT_RETURN; 454 void print() const { print_on(gclog_or_tty); } 455 }; 456 457 // A closure related to weak references processing which 458 // we embed in the CMSCollector, since we need to pass 459 // it to the reference processor for secondary filtering 460 // of references based on reachability of referent; 461 // see role of _is_alive_non_header closure in the 462 // ReferenceProcessor class. 463 // For objects in the CMS generation, this closure checks 464 // if the object is "live" (reachable). Used in weak 465 // reference processing. 466 class CMSIsAliveClosure: public BoolObjectClosure { 467 const MemRegion _span; 468 const CMSBitMap* _bit_map; 469 470 friend class CMSCollector; 471 public: 472 CMSIsAliveClosure(MemRegion span, 473 CMSBitMap* bit_map): 474 _span(span), 475 _bit_map(bit_map) { 476 assert(!span.is_empty(), "Empty span could spell trouble"); 477 } 478 479 bool do_object_b(oop obj); 480 }; 481 482 483 // Implements AbstractRefProcTaskExecutor for CMS. 484 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 485 public: 486 487 CMSRefProcTaskExecutor(CMSCollector& collector) 488 : _collector(collector) 489 { } 490 491 // Executes a task using worker threads. 492 virtual void execute(ProcessTask& task); 493 virtual void execute(EnqueueTask& task); 494 private: 495 CMSCollector& _collector; 496 }; 497 498 499 class CMSCollector: public CHeapObj<mtGC> { 500 friend class VMStructs; 501 friend class ConcurrentMarkSweepThread; 502 friend class ConcurrentMarkSweepGeneration; 503 friend class CompactibleFreeListSpace; 504 friend class CMSParMarkTask; 505 friend class CMSParInitialMarkTask; 506 friend class CMSParRemarkTask; 507 friend class CMSConcMarkingTask; 508 friend class CMSRefProcTaskProxy; 509 friend class CMSRefProcTaskExecutor; 510 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 511 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 512 friend class PushOrMarkClosure; // to access _restart_addr 513 friend class Par_PushOrMarkClosure; // to access _restart_addr 514 friend class MarkFromRootsClosure; // -- ditto -- 515 // ... and for clearing cards 516 friend class Par_MarkFromRootsClosure; // to access _restart_addr 517 // ... and for clearing cards 518 friend class Par_ConcMarkingClosure; // to access _restart_addr etc. 519 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 520 friend class PushAndMarkVerifyClosure; // -- ditto -- 521 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 522 friend class PushAndMarkClosure; // -- ditto -- 523 friend class Par_PushAndMarkClosure; // -- ditto -- 524 friend class CMSKeepAliveClosure; // -- ditto -- 525 friend class CMSDrainMarkingStackClosure; // -- ditto -- 526 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 527 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 528 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 529 friend class VM_CMS_Operation; 530 friend class VM_CMS_Initial_Mark; 531 friend class VM_CMS_Final_Remark; 532 friend class TraceCMSMemoryManagerStats; 533 534 private: 535 jlong _time_of_last_gc; 536 void update_time_of_last_gc(jlong now) { 537 _time_of_last_gc = now; 538 } 539 540 OopTaskQueueSet* _task_queues; 541 542 // Overflow list of grey objects, threaded through mark-word 543 // Manipulated with CAS in the parallel/multi-threaded case. 544 oop _overflow_list; 545 // The following array-pair keeps track of mark words 546 // displaced for accommodating overflow list above. 547 // This code will likely be revisited under RFE#4922830. 548 Stack<oop, mtGC> _preserved_oop_stack; 549 Stack<markOop, mtGC> _preserved_mark_stack; 550 551 int* _hash_seed; 552 553 // In support of multi-threaded concurrent phases 554 YieldingFlexibleWorkGang* _conc_workers; 555 556 // Performance Counters 557 CollectorCounters* _gc_counters; 558 559 // Initialization Errors 560 bool _completed_initialization; 561 562 // In support of ExplicitGCInvokesConcurrent 563 static bool _full_gc_requested; 564 static GCCause::Cause _full_gc_cause; 565 unsigned int _collection_count_start; 566 567 // Should we unload classes this concurrent cycle? 568 bool _should_unload_classes; 569 unsigned int _concurrent_cycles_since_last_unload; 570 unsigned int concurrent_cycles_since_last_unload() const { 571 return _concurrent_cycles_since_last_unload; 572 } 573 // Did we (allow) unload classes in the previous concurrent cycle? 574 bool unloaded_classes_last_cycle() const { 575 return concurrent_cycles_since_last_unload() == 0; 576 } 577 // Root scanning options for perm gen 578 int _roots_scanning_options; 579 int roots_scanning_options() const { return _roots_scanning_options; } 580 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 581 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 582 583 // Verification support 584 CMSBitMap _verification_mark_bm; 585 void verify_after_remark_work_1(); 586 void verify_after_remark_work_2(); 587 588 // True if any verification flag is on. 589 bool _verifying; 590 bool verifying() const { return _verifying; } 591 void set_verifying(bool v) { _verifying = v; } 592 593 // Collector policy 594 ConcurrentMarkSweepPolicy* _collector_policy; 595 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 596 597 void set_did_compact(bool v); 598 599 // XXX Move these to CMSStats ??? FIX ME !!! 600 elapsedTimer _inter_sweep_timer; // Time between sweeps 601 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 602 // Padded decaying average estimates of the above 603 AdaptivePaddedAverage _inter_sweep_estimate; 604 AdaptivePaddedAverage _intra_sweep_estimate; 605 606 CMSTracer* _gc_tracer_cm; 607 ConcurrentGCTimer* _gc_timer_cm; 608 609 bool _cms_start_registered; 610 611 GCHeapSummary _last_heap_summary; 612 MetaspaceSummary _last_metaspace_summary; 613 614 void register_gc_start(GCCause::Cause cause); 615 void register_gc_end(); 616 void save_heap_summary(); 617 void report_heap_summary(GCWhen::Type when); 618 619 protected: 620 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 621 MemRegion _span; // Span covering above two 622 CardTableRS* _ct; // Card table 623 624 // CMS marking support structures 625 CMSBitMap _markBitMap; 626 CMSBitMap _modUnionTable; 627 CMSMarkStack _markStack; 628 629 HeapWord* _restart_addr; // In support of marking stack overflow 630 void lower_restart_addr(HeapWord* low); 631 632 // Counters in support of marking stack / work queue overflow handling: 633 // a non-zero value indicates certain types of overflow events during 634 // the current CMS cycle and could lead to stack resizing efforts at 635 // an opportune future time. 636 size_t _ser_pmc_preclean_ovflw; 637 size_t _ser_pmc_remark_ovflw; 638 size_t _par_pmc_remark_ovflw; 639 size_t _ser_kac_preclean_ovflw; 640 size_t _ser_kac_ovflw; 641 size_t _par_kac_ovflw; 642 NOT_PRODUCT(ssize_t _num_par_pushes;) 643 644 // ("Weak") Reference processing support. 645 ReferenceProcessor* _ref_processor; 646 CMSIsAliveClosure _is_alive_closure; 647 // Keep this textually after _markBitMap and _span; c'tor dependency. 648 649 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 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 // Signaling/State related to coordination between fore- and background 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; 699 700 // Occupancy used for bootstrapping stats 701 double _bootstrap_occupancy; 702 703 // Timer 704 elapsedTimer _timer; 705 706 // Timing, allocation and promotion statistics, used for scheduling. 707 CMSStats _stats; 708 709 enum CMS_op_type { 710 CMS_op_checkpointRootsInitial, 711 CMS_op_checkpointRootsFinal 712 }; 713 714 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 715 bool stop_world_and_do(CMS_op_type op); 716 717 OopTaskQueueSet* task_queues() { return _task_queues; } 718 int* hash_seed(int i) { return &_hash_seed[i]; } 719 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 720 721 // Support for parallelizing Eden rescan in CMS remark phase 722 void sample_eden(); // ... sample Eden space top 723 724 private: 725 // Support for parallelizing young gen rescan in CMS remark phase 726 ParNewGeneration* _young_gen; // the younger gen 727 728 HeapWord** _top_addr; // ... Top of Eden 729 HeapWord** _end_addr; // ... End of Eden 730 Mutex* _eden_chunk_lock; 731 HeapWord** _eden_chunk_array; // ... Eden partitioning array 732 size_t _eden_chunk_index; // ... top (exclusive) of array 733 size_t _eden_chunk_capacity; // ... max entries in array 734 735 // Support for parallelizing survivor space rescan 736 HeapWord** _survivor_chunk_array; 737 size_t _survivor_chunk_index; 738 size_t _survivor_chunk_capacity; 739 size_t* _cursor; 740 ChunkArray* _survivor_plab_array; 741 742 // Support for marking stack overflow handling 743 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 744 bool par_take_from_overflow_list(size_t num, 745 OopTaskQueue* to_work_q, 746 int no_of_gc_threads); 747 void push_on_overflow_list(oop p); 748 void par_push_on_overflow_list(oop p); 749 // The following is, obviously, not, in general, "MT-stable" 750 bool overflow_list_is_empty() const; 751 752 void preserve_mark_if_necessary(oop p); 753 void par_preserve_mark_if_necessary(oop p); 754 void preserve_mark_work(oop p, markOop m); 755 void restore_preserved_marks_if_any(); 756 NOT_PRODUCT(bool no_preserved_marks() const;) 757 // In support of testing overflow code 758 NOT_PRODUCT(int _overflow_counter;) 759 NOT_PRODUCT(bool simulate_overflow();) // Sequential 760 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 761 762 // CMS work methods 763 void checkpointRootsInitialWork(); // Initial checkpoint work 764 765 // A return value of false indicates failure due to stack overflow 766 bool markFromRootsWork(); // Concurrent marking work 767 768 public: // FIX ME!!! only for testing 769 bool do_marking_st(); // Single-threaded marking 770 bool do_marking_mt(); // Multi-threaded marking 771 772 private: 773 774 // Concurrent precleaning work 775 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, 776 ScanMarkedObjectsAgainCarefullyClosure* cl); 777 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, 778 ScanMarkedObjectsAgainCarefullyClosure* cl); 779 // Does precleaning work, returning a quantity indicative of 780 // the amount of "useful work" done. 781 size_t preclean_work(bool clean_refs, bool clean_survivors); 782 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 783 void abortable_preclean(); // Preclean while looking for possible abort 784 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 785 // Helper function for above; merge-sorts the per-thread plab samples 786 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 787 // Resets (i.e. clears) the per-thread plab sample vectors 788 void reset_survivor_plab_arrays(); 789 790 // Final (second) checkpoint work 791 void checkpointRootsFinalWork(); 792 // Work routine for parallel version of remark 793 void do_remark_parallel(); 794 // Work routine for non-parallel version of remark 795 void do_remark_non_parallel(); 796 // Reference processing work routine (during second checkpoint) 797 void refProcessingWork(); 798 799 // Concurrent sweeping work 800 void sweepWork(ConcurrentMarkSweepGeneration* gen); 801 802 // (Concurrent) resetting of support data structures 803 void reset(bool concurrent); 804 805 // Clear _expansion_cause fields of constituent generations 806 void clear_expansion_cause(); 807 808 // An auxiliary method used to record the ends of 809 // used regions of each generation to limit the extent of sweep 810 void save_sweep_limits(); 811 812 // A work method used by the foreground collector to do 813 // a mark-sweep-compact. 814 void do_compaction_work(bool clear_all_soft_refs); 815 816 // Work methods for reporting concurrent mode interruption or failure 817 bool is_external_interruption(); 818 void report_concurrent_mode_interruption(); 819 820 // If the background GC is active, acquire control from the background 821 // GC and do the collection. 822 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 823 824 // For synchronizing passing of control from background to foreground 825 // GC. waitForForegroundGC() is called by the background 826 // collector. It if had to wait for a foreground collection, 827 // it returns true and the background collection should assume 828 // that the collection was finished by the foreground 829 // collector. 830 bool waitForForegroundGC(); 831 832 size_t block_size_using_printezis_bits(HeapWord* addr) const; 833 size_t block_size_if_printezis_bits(HeapWord* addr) const; 834 HeapWord* next_card_start_after_block(HeapWord* addr) const; 835 836 void setup_cms_unloading_and_verification_state(); 837 public: 838 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 839 CardTableRS* ct, 840 ConcurrentMarkSweepPolicy* cp); 841 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 842 843 ReferenceProcessor* ref_processor() { return _ref_processor; } 844 void ref_processor_init(); 845 846 Mutex* bitMapLock() const { return _markBitMap.lock(); } 847 static CollectorState abstract_state() { return _collectorState; } 848 849 bool should_abort_preclean() const; // Whether preclean should be aborted. 850 size_t get_eden_used() const; 851 size_t get_eden_capacity() const; 852 853 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 854 855 // Locking checks 856 NOT_PRODUCT(static bool have_cms_token();) 857 858 bool shouldConcurrentCollect(); 859 860 void collect(bool full, 861 bool clear_all_soft_refs, 862 size_t size, 863 bool tlab); 864 void collect_in_background(GCCause::Cause cause); 865 866 // In support of ExplicitGCInvokesConcurrent 867 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 868 // Should we unload classes in a particular concurrent cycle? 869 bool should_unload_classes() const { 870 return _should_unload_classes; 871 } 872 void update_should_unload_classes(); 873 874 void direct_allocated(HeapWord* start, size_t size); 875 876 // Object is dead if not marked and current phase is sweeping. 877 bool is_dead_obj(oop obj) const; 878 879 // After a promotion (of "start"), do any necessary marking. 880 // If "par", then it's being done by a parallel GC thread. 881 // The last two args indicate if we need precise marking 882 // and if so the size of the object so it can be dirtied 883 // in its entirety. 884 void promoted(bool par, HeapWord* start, 885 bool is_obj_array, size_t obj_size); 886 887 void getFreelistLocks() const; 888 void releaseFreelistLocks() const; 889 bool haveFreelistLocks() const; 890 891 // Adjust size of underlying generation 892 void compute_new_size(); 893 894 // GC prologue and epilogue 895 void gc_prologue(bool full); 896 void gc_epilogue(bool full); 897 898 jlong time_of_last_gc(jlong now) { 899 if (_collectorState <= Idling) { 900 // gc not in progress 901 return _time_of_last_gc; 902 } else { 903 // collection in progress 904 return now; 905 } 906 } 907 908 // Support for parallel remark of survivor space 909 void* get_data_recorder(int thr_num); 910 void sample_eden_chunk(); 911 912 CMSBitMap* markBitMap() { return &_markBitMap; } 913 void directAllocated(HeapWord* start, size_t size); 914 915 // Main CMS steps and related support 916 void checkpointRootsInitial(); 917 bool markFromRoots(); // a return value of false indicates failure 918 // due to stack overflow 919 void preclean(); 920 void checkpointRootsFinal(); 921 void sweep(); 922 923 // Check that the currently executing thread is the expected 924 // one (foreground collector or background collector). 925 static void check_correct_thread_executing() PRODUCT_RETURN; 926 927 bool is_cms_reachable(HeapWord* addr); 928 929 // Performance Counter Support 930 CollectorCounters* counters() { return _gc_counters; } 931 932 // Timer stuff 933 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 934 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 935 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 936 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } 937 938 int yields() { return _numYields; } 939 void resetYields() { _numYields = 0; } 940 void incrementYields() { _numYields++; } 941 void resetNumDirtyCards() { _numDirtyCards = 0; } 942 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 943 size_t numDirtyCards() { return _numDirtyCards; } 944 945 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 946 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 947 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 948 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 949 size_t sweep_count() const { return _sweep_count; } 950 void increment_sweep_count() { _sweep_count++; } 951 952 // Timers/stats for gc scheduling and incremental mode pacing. 953 CMSStats& stats() { return _stats; } 954 955 // Adaptive size policy 956 AdaptiveSizePolicy* size_policy(); 957 958 static void print_on_error(outputStream* st); 959 960 // Debugging 961 void verify(); 962 bool verify_after_remark(bool silent = VerifySilently); 963 void verify_ok_to_terminate() const PRODUCT_RETURN; 964 void verify_work_stacks_empty() const PRODUCT_RETURN; 965 void verify_overflow_empty() const PRODUCT_RETURN; 966 967 // Convenience methods in support of debugging 968 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 969 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 970 971 // Accessors 972 CMSMarkStack* verification_mark_stack() { return &_markStack; } 973 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 974 975 // Initialization errors 976 bool completed_initialization() { return _completed_initialization; } 977 978 void print_eden_and_survivor_chunk_arrays(); 979 }; 980 981 class CMSExpansionCause : public AllStatic { 982 public: 983 enum Cause { 984 _no_expansion, 985 _satisfy_free_ratio, 986 _satisfy_promotion, 987 _satisfy_allocation, 988 _allocate_par_lab, 989 _allocate_par_spooling_space, 990 _adaptive_size_policy 991 }; 992 // Return a string describing the cause of the expansion. 993 static const char* to_string(CMSExpansionCause::Cause cause); 994 }; 995 996 class ConcurrentMarkSweepGeneration: public CardGeneration { 997 friend class VMStructs; 998 friend class ConcurrentMarkSweepThread; 999 friend class ConcurrentMarkSweep; 1000 friend class CMSCollector; 1001 protected: 1002 static CMSCollector* _collector; // the collector that collects us 1003 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1004 1005 // Performance Counters 1006 GenerationCounters* _gen_counters; 1007 GSpaceCounters* _space_counters; 1008 1009 // Words directly allocated, used by CMSStats. 1010 size_t _direct_allocated_words; 1011 1012 // Non-product stat counters 1013 NOT_PRODUCT( 1014 size_t _numObjectsPromoted; 1015 size_t _numWordsPromoted; 1016 size_t _numObjectsAllocated; 1017 size_t _numWordsAllocated; 1018 ) 1019 1020 // Used for sizing decisions 1021 bool _incremental_collection_failed; 1022 bool incremental_collection_failed() { 1023 return _incremental_collection_failed; 1024 } 1025 void set_incremental_collection_failed() { 1026 _incremental_collection_failed = true; 1027 } 1028 void clear_incremental_collection_failed() { 1029 _incremental_collection_failed = false; 1030 } 1031 1032 // accessors 1033 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1034 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1035 1036 // Accessing spaces 1037 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } 1038 1039 private: 1040 // For parallel young-gen GC support. 1041 CMSParGCThreadState** _par_gc_thread_states; 1042 1043 // Reason generation was expanded 1044 CMSExpansionCause::Cause _expansion_cause; 1045 1046 // In support of MinChunkSize being larger than min object size 1047 const double _dilatation_factor; 1048 1049 // True if a compacting collection was done. 1050 bool _did_compact; 1051 bool did_compact() { return _did_compact; } 1052 1053 // Fraction of current occupancy at which to start a CMS collection which 1054 // will collect this generation (at least). 1055 double _initiating_occupancy; 1056 1057 protected: 1058 // Shrink generation by specified size (returns false if unable to shrink) 1059 void shrink_free_list_by(size_t bytes); 1060 1061 // Update statistics for GC 1062 virtual void update_gc_stats(int level, bool full); 1063 1064 // Maximum available space in the generation (including uncommitted) 1065 // space. 1066 size_t max_available() const; 1067 1068 // getter and initializer for _initiating_occupancy field. 1069 double initiating_occupancy() const { return _initiating_occupancy; } 1070 void init_initiating_occupancy(intx io, uintx tr); 1071 1072 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1073 1074 void assert_correct_size_change_locking(); 1075 1076 public: 1077 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1078 int level, CardTableRS* ct, 1079 bool use_adaptive_freelists, 1080 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 1081 1082 // Accessors 1083 CMSCollector* collector() const { return _collector; } 1084 static void set_collector(CMSCollector* collector) { 1085 assert(_collector == NULL, "already set"); 1086 _collector = collector; 1087 } 1088 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1089 1090 Mutex* freelistLock() const; 1091 1092 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1093 1094 void set_did_compact(bool v) { _did_compact = v; } 1095 1096 bool refs_discovery_is_atomic() const { return false; } 1097 bool refs_discovery_is_mt() const { 1098 // Note: CMS does MT-discovery during the parallel-remark 1099 // phases. Use ReferenceProcessorMTMutator to make refs 1100 // discovery MT-safe during such phases or other parallel 1101 // discovery phases in the future. This may all go away 1102 // if/when we decide that refs discovery is sufficiently 1103 // rare that the cost of the CAS's involved is in the 1104 // noise. That's a measurement that should be done, and 1105 // the code simplified if that turns out to be the case. 1106 return ConcGCThreads > 1; 1107 } 1108 1109 // Override 1110 virtual void ref_processor_init(); 1111 1112 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1113 1114 // Space enquiries 1115 double occupancy() const { return ((double)used())/((double)capacity()); } 1116 size_t contiguous_available() const; 1117 size_t unsafe_max_alloc_nogc() const; 1118 1119 // over-rides 1120 MemRegion used_region_at_save_marks() const; 1121 1122 // Does a "full" (forced) collection invoked on this generation collect 1123 // all younger generations as well? Note that the second conjunct is a 1124 // hack to allow the collection of the younger gen first if the flag is 1125 // set. 1126 virtual bool full_collects_younger_generations() const { 1127 return !ScavengeBeforeFullGC; 1128 } 1129 1130 // Adjust quantities in the generation affected by 1131 // the compaction. 1132 void reset_after_compaction(); 1133 1134 // Allocation support 1135 HeapWord* allocate(size_t size, bool tlab); 1136 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1137 oop promote(oop obj, size_t obj_size); 1138 HeapWord* par_allocate(size_t size, bool tlab) { 1139 return allocate(size, tlab); 1140 } 1141 1142 1143 // Used by CMSStats to track direct allocation. The value is sampled and 1144 // reset after each young gen collection. 1145 size_t direct_allocated_words() const { return _direct_allocated_words; } 1146 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1147 1148 // Overrides for parallel promotion. 1149 virtual oop par_promote(int thread_num, 1150 oop obj, markOop m, size_t word_sz); 1151 virtual void par_promote_alloc_done(int thread_num); 1152 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1153 1154 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1155 1156 // Inform this (non-young) generation that a promotion failure was 1157 // encountered during a collection of a younger generation that 1158 // promotes into this generation. 1159 virtual void promotion_failure_occurred(); 1160 1161 bool should_collect(bool full, size_t size, bool tlab); 1162 virtual bool should_concurrent_collect() const; 1163 virtual bool is_too_full() const; 1164 void collect(bool full, 1165 bool clear_all_soft_refs, 1166 size_t size, 1167 bool tlab); 1168 1169 HeapWord* expand_and_allocate(size_t word_size, 1170 bool tlab, 1171 bool parallel = false); 1172 1173 // GC prologue and epilogue 1174 void gc_prologue(bool full); 1175 void gc_prologue_work(bool full, bool registerClosure, 1176 ModUnionClosure* modUnionClosure); 1177 void gc_epilogue(bool full); 1178 void gc_epilogue_work(bool full); 1179 1180 // Time since last GC of this generation 1181 jlong time_of_last_gc(jlong now) { 1182 return collector()->time_of_last_gc(now); 1183 } 1184 void update_time_of_last_gc(jlong now) { 1185 collector()-> update_time_of_last_gc(now); 1186 } 1187 1188 // Allocation failure 1189 void shrink(size_t bytes); 1190 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1191 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1192 1193 // Iteration support and related enquiries 1194 void save_marks(); 1195 bool no_allocs_since_save_marks(); 1196 1197 // Iteration support specific to CMS generations 1198 void save_sweep_limit(); 1199 1200 // More iteration support 1201 virtual void oop_iterate(ExtendedOopClosure* cl); 1202 virtual void safe_object_iterate(ObjectClosure* cl); 1203 virtual void object_iterate(ObjectClosure* cl); 1204 1205 // Need to declare the full complement of closures, whether we'll 1206 // override them or not, or get message from the compiler: 1207 // oop_since_save_marks_iterate_nv hides virtual function... 1208 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1209 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1210 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1211 1212 // Smart allocation XXX -- move to CFLSpace? 1213 void setNearLargestChunk(); 1214 bool isNearLargestChunk(HeapWord* addr); 1215 1216 // Get the chunk at the end of the space. Delegates to 1217 // the space. 1218 FreeChunk* find_chunk_at_end(); 1219 1220 void post_compact(); 1221 1222 // Debugging 1223 void prepare_for_verify(); 1224 void verify(); 1225 void print_statistics() PRODUCT_RETURN; 1226 1227 // Performance Counters support 1228 virtual void update_counters(); 1229 virtual void update_counters(size_t used); 1230 void initialize_performance_counters(); 1231 CollectorCounters* counters() { return collector()->counters(); } 1232 1233 // Support for parallel remark of survivor space 1234 void* get_data_recorder(int thr_num) { 1235 //Delegate to collector 1236 return collector()->get_data_recorder(thr_num); 1237 } 1238 void sample_eden_chunk() { 1239 //Delegate to collector 1240 return collector()->sample_eden_chunk(); 1241 } 1242 1243 // Printing 1244 const char* name() const; 1245 virtual const char* short_name() const { return "CMS"; } 1246 void print() const; 1247 void printOccupancy(const char* s); 1248 1249 // Resize the generation after a compacting GC. The 1250 // generation can be treated as a contiguous space 1251 // after the compaction. 1252 virtual void compute_new_size(); 1253 // Resize the generation after a non-compacting 1254 // collection. 1255 void compute_new_size_free_list(); 1256 }; 1257 1258 // 1259 // Closures of various sorts used by CMS to accomplish its work 1260 // 1261 1262 // This closure is used to do concurrent marking from the roots 1263 // following the first checkpoint. 1264 class MarkFromRootsClosure: public BitMapClosure { 1265 CMSCollector* _collector; 1266 MemRegion _span; 1267 CMSBitMap* _bitMap; 1268 CMSBitMap* _mut; 1269 CMSMarkStack* _markStack; 1270 bool _yield; 1271 int _skipBits; 1272 HeapWord* _finger; 1273 HeapWord* _threshold; 1274 DEBUG_ONLY(bool _verifying;) 1275 1276 public: 1277 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1278 CMSBitMap* bitMap, 1279 CMSMarkStack* markStack, 1280 bool should_yield, bool verifying = false); 1281 bool do_bit(size_t offset); 1282 void reset(HeapWord* addr); 1283 inline void do_yield_check(); 1284 1285 private: 1286 void scanOopsInOop(HeapWord* ptr); 1287 void do_yield_work(); 1288 }; 1289 1290 // This closure is used to do concurrent multi-threaded 1291 // marking from the roots following the first checkpoint. 1292 // XXX This should really be a subclass of The serial version 1293 // above, but i have not had the time to refactor things cleanly. 1294 class Par_MarkFromRootsClosure: public BitMapClosure { 1295 CMSCollector* _collector; 1296 MemRegion _whole_span; 1297 MemRegion _span; 1298 CMSBitMap* _bit_map; 1299 CMSBitMap* _mut; 1300 OopTaskQueue* _work_queue; 1301 CMSMarkStack* _overflow_stack; 1302 int _skip_bits; 1303 HeapWord* _finger; 1304 HeapWord* _threshold; 1305 CMSConcMarkingTask* _task; 1306 public: 1307 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1308 MemRegion span, 1309 CMSBitMap* bit_map, 1310 OopTaskQueue* work_queue, 1311 CMSMarkStack* overflow_stack); 1312 bool do_bit(size_t offset); 1313 inline void do_yield_check(); 1314 1315 private: 1316 void scan_oops_in_oop(HeapWord* ptr); 1317 void do_yield_work(); 1318 bool get_work_from_overflow_stack(); 1319 }; 1320 1321 // The following closures are used to do certain kinds of verification of 1322 // CMS marking. 1323 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1324 CMSCollector* _collector; 1325 MemRegion _span; 1326 CMSBitMap* _verification_bm; 1327 CMSBitMap* _cms_bm; 1328 CMSMarkStack* _mark_stack; 1329 protected: 1330 void do_oop(oop p); 1331 template <class T> inline void do_oop_work(T *p) { 1332 oop obj = oopDesc::load_decode_heap_oop(p); 1333 do_oop(obj); 1334 } 1335 public: 1336 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1337 MemRegion span, 1338 CMSBitMap* verification_bm, 1339 CMSBitMap* cms_bm, 1340 CMSMarkStack* mark_stack); 1341 void do_oop(oop* p); 1342 void do_oop(narrowOop* p); 1343 1344 // Deal with a stack overflow condition 1345 void handle_stack_overflow(HeapWord* lost); 1346 }; 1347 1348 class MarkFromRootsVerifyClosure: public BitMapClosure { 1349 CMSCollector* _collector; 1350 MemRegion _span; 1351 CMSBitMap* _verification_bm; 1352 CMSBitMap* _cms_bm; 1353 CMSMarkStack* _mark_stack; 1354 HeapWord* _finger; 1355 PushAndMarkVerifyClosure _pam_verify_closure; 1356 public: 1357 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1358 CMSBitMap* verification_bm, 1359 CMSBitMap* cms_bm, 1360 CMSMarkStack* mark_stack); 1361 bool do_bit(size_t offset); 1362 void reset(HeapWord* addr); 1363 }; 1364 1365 1366 // This closure is used to check that a certain set of bits is 1367 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1368 class FalseBitMapClosure: public BitMapClosure { 1369 public: 1370 bool do_bit(size_t offset) { 1371 guarantee(false, "Should not have a 1 bit"); 1372 return true; 1373 } 1374 }; 1375 1376 // A version of ObjectClosure with "memory" (see _previous_address below) 1377 class UpwardsObjectClosure: public BoolObjectClosure { 1378 HeapWord* _previous_address; 1379 public: 1380 UpwardsObjectClosure() : _previous_address(NULL) { } 1381 void set_previous(HeapWord* addr) { _previous_address = addr; } 1382 HeapWord* previous() { return _previous_address; } 1383 // A return value of "true" can be used by the caller to decide 1384 // if this object's end should *NOT* be recorded in 1385 // _previous_address above. 1386 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1387 }; 1388 1389 // This closure is used during the second checkpointing phase 1390 // to rescan the marked objects on the dirty cards in the mod 1391 // union table and the card table proper. It's invoked via 1392 // MarkFromDirtyCardsClosure below. It uses either 1393 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1394 // declared in genOopClosures.hpp to accomplish some of its work. 1395 // In the parallel case the bitMap is shared, so access to 1396 // it needs to be suitably synchronized for updates by embedded 1397 // closures that update it; however, this closure itself only 1398 // reads the bit_map and because it is idempotent, is immune to 1399 // reading stale values. 1400 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1401 #ifdef ASSERT 1402 CMSCollector* _collector; 1403 MemRegion _span; 1404 union { 1405 CMSMarkStack* _mark_stack; 1406 OopTaskQueue* _work_queue; 1407 }; 1408 #endif // ASSERT 1409 bool _parallel; 1410 CMSBitMap* _bit_map; 1411 union { 1412 MarkRefsIntoAndScanClosure* _scan_closure; 1413 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1414 }; 1415 1416 public: 1417 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1418 MemRegion span, 1419 ReferenceProcessor* rp, 1420 CMSBitMap* bit_map, 1421 CMSMarkStack* mark_stack, 1422 MarkRefsIntoAndScanClosure* cl): 1423 #ifdef ASSERT 1424 _collector(collector), 1425 _span(span), 1426 _mark_stack(mark_stack), 1427 #endif // ASSERT 1428 _parallel(false), 1429 _bit_map(bit_map), 1430 _scan_closure(cl) { } 1431 1432 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1433 MemRegion span, 1434 ReferenceProcessor* rp, 1435 CMSBitMap* bit_map, 1436 OopTaskQueue* work_queue, 1437 Par_MarkRefsIntoAndScanClosure* cl): 1438 #ifdef ASSERT 1439 _collector(collector), 1440 _span(span), 1441 _work_queue(work_queue), 1442 #endif // ASSERT 1443 _parallel(true), 1444 _bit_map(bit_map), 1445 _par_scan_closure(cl) { } 1446 1447 bool do_object_b(oop obj) { 1448 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1449 return false; 1450 } 1451 bool do_object_bm(oop p, MemRegion mr); 1452 }; 1453 1454 // This closure is used during the second checkpointing phase 1455 // to rescan the marked objects on the dirty cards in the mod 1456 // union table and the card table proper. It invokes 1457 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1458 // In the parallel case, the bit map is shared and requires 1459 // synchronized access. 1460 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1461 CompactibleFreeListSpace* _space; 1462 ScanMarkedObjectsAgainClosure _scan_cl; 1463 size_t _num_dirty_cards; 1464 1465 public: 1466 MarkFromDirtyCardsClosure(CMSCollector* collector, 1467 MemRegion span, 1468 CompactibleFreeListSpace* space, 1469 CMSBitMap* bit_map, 1470 CMSMarkStack* mark_stack, 1471 MarkRefsIntoAndScanClosure* cl): 1472 _space(space), 1473 _num_dirty_cards(0), 1474 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1475 mark_stack, cl) { } 1476 1477 MarkFromDirtyCardsClosure(CMSCollector* collector, 1478 MemRegion span, 1479 CompactibleFreeListSpace* space, 1480 CMSBitMap* bit_map, 1481 OopTaskQueue* work_queue, 1482 Par_MarkRefsIntoAndScanClosure* cl): 1483 _space(space), 1484 _num_dirty_cards(0), 1485 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1486 work_queue, cl) { } 1487 1488 void do_MemRegion(MemRegion mr); 1489 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1490 size_t num_dirty_cards() { return _num_dirty_cards; } 1491 }; 1492 1493 // This closure is used in the non-product build to check 1494 // that there are no MemRegions with a certain property. 1495 class FalseMemRegionClosure: public MemRegionClosure { 1496 void do_MemRegion(MemRegion mr) { 1497 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1498 guarantee(false, "Should never be here"); 1499 } 1500 }; 1501 1502 // This closure is used during the precleaning phase 1503 // to "carefully" rescan marked objects on dirty cards. 1504 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1505 // to accomplish some of its work. 1506 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1507 CMSCollector* _collector; 1508 MemRegion _span; 1509 bool _yield; 1510 Mutex* _freelistLock; 1511 CMSBitMap* _bitMap; 1512 CMSMarkStack* _markStack; 1513 MarkRefsIntoAndScanClosure* _scanningClosure; 1514 1515 public: 1516 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1517 MemRegion span, 1518 CMSBitMap* bitMap, 1519 CMSMarkStack* markStack, 1520 MarkRefsIntoAndScanClosure* cl, 1521 bool should_yield): 1522 _collector(collector), 1523 _span(span), 1524 _yield(should_yield), 1525 _bitMap(bitMap), 1526 _markStack(markStack), 1527 _scanningClosure(cl) { 1528 } 1529 1530 void do_object(oop p) { 1531 guarantee(false, "call do_object_careful instead"); 1532 } 1533 1534 size_t do_object_careful(oop p) { 1535 guarantee(false, "Unexpected caller"); 1536 return 0; 1537 } 1538 1539 size_t do_object_careful_m(oop p, MemRegion mr); 1540 1541 void setFreelistLock(Mutex* m) { 1542 _freelistLock = m; 1543 _scanningClosure->set_freelistLock(m); 1544 } 1545 1546 private: 1547 inline bool do_yield_check(); 1548 1549 void do_yield_work(); 1550 }; 1551 1552 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1553 CMSCollector* _collector; 1554 MemRegion _span; 1555 bool _yield; 1556 CMSBitMap* _bit_map; 1557 CMSMarkStack* _mark_stack; 1558 PushAndMarkClosure* _scanning_closure; 1559 unsigned int _before_count; 1560 1561 public: 1562 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1563 MemRegion span, 1564 CMSBitMap* bit_map, 1565 CMSMarkStack* mark_stack, 1566 PushAndMarkClosure* cl, 1567 unsigned int before_count, 1568 bool should_yield): 1569 _collector(collector), 1570 _span(span), 1571 _yield(should_yield), 1572 _bit_map(bit_map), 1573 _mark_stack(mark_stack), 1574 _scanning_closure(cl), 1575 _before_count(before_count) 1576 { } 1577 1578 void do_object(oop p) { 1579 guarantee(false, "call do_object_careful instead"); 1580 } 1581 1582 size_t do_object_careful(oop p); 1583 1584 size_t do_object_careful_m(oop p, MemRegion mr) { 1585 guarantee(false, "Unexpected caller"); 1586 return 0; 1587 } 1588 1589 private: 1590 inline void do_yield_check(); 1591 void do_yield_work(); 1592 }; 1593 1594 // This closure is used to accomplish the sweeping work 1595 // after the second checkpoint but before the concurrent reset 1596 // phase. 1597 // 1598 // Terminology 1599 // left hand chunk (LHC) - block of one or more chunks currently being 1600 // coalesced. The LHC is available for coalescing with a new chunk. 1601 // right hand chunk (RHC) - block that is currently being swept that is 1602 // free or garbage that can be coalesced with the LHC. 1603 // _inFreeRange is true if there is currently a LHC 1604 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1605 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1606 // _freeFinger is the address of the current LHC 1607 class SweepClosure: public BlkClosureCareful { 1608 CMSCollector* _collector; // collector doing the work 1609 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1610 CompactibleFreeListSpace* _sp; // Space being swept 1611 HeapWord* _limit;// the address at or above which the sweep should stop 1612 // because we do not expect newly garbage blocks 1613 // eligible for sweeping past that address. 1614 Mutex* _freelistLock; // Free list lock (in space) 1615 CMSBitMap* _bitMap; // Marking bit map (in 1616 // generation) 1617 bool _inFreeRange; // Indicates if we are in the 1618 // midst of a free run 1619 bool _freeRangeInFreeLists; 1620 // Often, we have just found 1621 // a free chunk and started 1622 // a new free range; we do not 1623 // eagerly remove this chunk from 1624 // the free lists unless there is 1625 // a possibility of coalescing. 1626 // When true, this flag indicates 1627 // that the _freeFinger below 1628 // points to a potentially free chunk 1629 // that may still be in the free lists 1630 bool _lastFreeRangeCoalesced; 1631 // free range contains chunks 1632 // coalesced 1633 bool _yield; 1634 // Whether sweeping should be 1635 // done with yields. For instance 1636 // when done by the foreground 1637 // collector we shouldn't yield. 1638 HeapWord* _freeFinger; // When _inFreeRange is set, the 1639 // pointer to the "left hand 1640 // chunk" 1641 size_t _freeRangeSize; 1642 // When _inFreeRange is set, this 1643 // indicates the accumulated size 1644 // of the "left hand chunk" 1645 NOT_PRODUCT( 1646 size_t _numObjectsFreed; 1647 size_t _numWordsFreed; 1648 size_t _numObjectsLive; 1649 size_t _numWordsLive; 1650 size_t _numObjectsAlreadyFree; 1651 size_t _numWordsAlreadyFree; 1652 FreeChunk* _last_fc; 1653 ) 1654 private: 1655 // Code that is common to a free chunk or garbage when 1656 // encountered during sweeping. 1657 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1658 // Process a free chunk during sweeping. 1659 void do_already_free_chunk(FreeChunk *fc); 1660 // Work method called when processing an already free or a 1661 // freshly garbage chunk to do a lookahead and possibly a 1662 // preemptive flush if crossing over _limit. 1663 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1664 // Process a garbage chunk during sweeping. 1665 size_t do_garbage_chunk(FreeChunk *fc); 1666 // Process a live chunk during sweeping. 1667 size_t do_live_chunk(FreeChunk* fc); 1668 1669 // Accessors. 1670 HeapWord* freeFinger() const { return _freeFinger; } 1671 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1672 bool inFreeRange() const { return _inFreeRange; } 1673 void set_inFreeRange(bool v) { _inFreeRange = v; } 1674 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1675 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1676 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1677 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1678 1679 // Initialize a free range. 1680 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1681 // Return this chunk to the free lists. 1682 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1683 1684 // Check if we should yield and do so when necessary. 1685 inline void do_yield_check(HeapWord* addr); 1686 1687 // Yield 1688 void do_yield_work(HeapWord* addr); 1689 1690 // Debugging/Printing 1691 void print_free_block_coalesced(FreeChunk* fc) const; 1692 1693 public: 1694 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1695 CMSBitMap* bitMap, bool should_yield); 1696 ~SweepClosure() PRODUCT_RETURN; 1697 1698 size_t do_blk_careful(HeapWord* addr); 1699 void print() const { print_on(tty); } 1700 void print_on(outputStream *st) const; 1701 }; 1702 1703 // Closures related to weak references processing 1704 1705 // During CMS' weak reference processing, this is a 1706 // work-routine/closure used to complete transitive 1707 // marking of objects as live after a certain point 1708 // in which an initial set has been completely accumulated. 1709 // This closure is currently used both during the final 1710 // remark stop-world phase, as well as during the concurrent 1711 // precleaning of the discovered reference lists. 1712 class CMSDrainMarkingStackClosure: public VoidClosure { 1713 CMSCollector* _collector; 1714 MemRegion _span; 1715 CMSMarkStack* _mark_stack; 1716 CMSBitMap* _bit_map; 1717 CMSKeepAliveClosure* _keep_alive; 1718 bool _concurrent_precleaning; 1719 public: 1720 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1721 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1722 CMSKeepAliveClosure* keep_alive, 1723 bool cpc): 1724 _collector(collector), 1725 _span(span), 1726 _bit_map(bit_map), 1727 _mark_stack(mark_stack), 1728 _keep_alive(keep_alive), 1729 _concurrent_precleaning(cpc) { 1730 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1731 "Mismatch"); 1732 } 1733 1734 void do_void(); 1735 }; 1736 1737 // A parallel version of CMSDrainMarkingStackClosure above. 1738 class CMSParDrainMarkingStackClosure: public VoidClosure { 1739 CMSCollector* _collector; 1740 MemRegion _span; 1741 OopTaskQueue* _work_queue; 1742 CMSBitMap* _bit_map; 1743 CMSInnerParMarkAndPushClosure _mark_and_push; 1744 1745 public: 1746 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1747 MemRegion span, CMSBitMap* bit_map, 1748 OopTaskQueue* work_queue): 1749 _collector(collector), 1750 _span(span), 1751 _bit_map(bit_map), 1752 _work_queue(work_queue), 1753 _mark_and_push(collector, span, bit_map, work_queue) { } 1754 1755 public: 1756 void trim_queue(uint max); 1757 void do_void(); 1758 }; 1759 1760 // Allow yielding or short-circuiting of reference list 1761 // precleaning work. 1762 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1763 CMSCollector* _collector; 1764 void do_yield_work(); 1765 public: 1766 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1767 _collector(collector) {} 1768 virtual bool should_return(); 1769 }; 1770 1771 1772 // Convenience class that locks free list locks for given CMS collector 1773 class FreelistLocker: public StackObj { 1774 private: 1775 CMSCollector* _collector; 1776 public: 1777 FreelistLocker(CMSCollector* collector): 1778 _collector(collector) { 1779 _collector->getFreelistLocks(); 1780 } 1781 1782 ~FreelistLocker() { 1783 _collector->releaseFreelistLocks(); 1784 } 1785 }; 1786 1787 // Mark all dead objects in a given space. 1788 class MarkDeadObjectsClosure: public BlkClosure { 1789 const CMSCollector* _collector; 1790 const CompactibleFreeListSpace* _sp; 1791 CMSBitMap* _live_bit_map; 1792 CMSBitMap* _dead_bit_map; 1793 public: 1794 MarkDeadObjectsClosure(const CMSCollector* collector, 1795 const CompactibleFreeListSpace* sp, 1796 CMSBitMap *live_bit_map, 1797 CMSBitMap *dead_bit_map) : 1798 _collector(collector), 1799 _sp(sp), 1800 _live_bit_map(live_bit_map), 1801 _dead_bit_map(dead_bit_map) {} 1802 size_t do_blk(HeapWord* addr); 1803 }; 1804 1805 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1806 1807 public: 1808 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1809 }; 1810 1811 1812 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP