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 // A bounded minimum size of PLABs, should not return too small values since 743 // this will affect the size of the data structures used for parallel young gen rescan 744 size_t plab_sample_minimum_size(); 745 746 // Support for marking stack overflow handling 747 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 748 bool par_take_from_overflow_list(size_t num, 749 OopTaskQueue* to_work_q, 750 int no_of_gc_threads); 751 void push_on_overflow_list(oop p); 752 void par_push_on_overflow_list(oop p); 753 // The following is, obviously, not, in general, "MT-stable" 754 bool overflow_list_is_empty() const; 755 756 void preserve_mark_if_necessary(oop p); 757 void par_preserve_mark_if_necessary(oop p); 758 void preserve_mark_work(oop p, markOop m); 759 void restore_preserved_marks_if_any(); 760 NOT_PRODUCT(bool no_preserved_marks() const;) 761 // In support of testing overflow code 762 NOT_PRODUCT(int _overflow_counter;) 763 NOT_PRODUCT(bool simulate_overflow();) // Sequential 764 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 765 766 // CMS work methods 767 void checkpointRootsInitialWork(); // Initial checkpoint work 768 769 // A return value of false indicates failure due to stack overflow 770 bool markFromRootsWork(); // Concurrent marking work 771 772 public: // FIX ME!!! only for testing 773 bool do_marking_st(); // Single-threaded marking 774 bool do_marking_mt(); // Multi-threaded marking 775 776 private: 777 778 // Concurrent precleaning work 779 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* gen, 780 ScanMarkedObjectsAgainCarefullyClosure* cl); 781 size_t preclean_card_table(ConcurrentMarkSweepGeneration* gen, 782 ScanMarkedObjectsAgainCarefullyClosure* cl); 783 // Does precleaning work, returning a quantity indicative of 784 // the amount of "useful work" done. 785 size_t preclean_work(bool clean_refs, bool clean_survivors); 786 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 787 void abortable_preclean(); // Preclean while looking for possible abort 788 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 789 // Helper function for above; merge-sorts the per-thread plab samples 790 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 791 // Resets (i.e. clears) the per-thread plab sample vectors 792 void reset_survivor_plab_arrays(); 793 794 // Final (second) checkpoint work 795 void checkpointRootsFinalWork(); 796 // Work routine for parallel version of remark 797 void do_remark_parallel(); 798 // Work routine for non-parallel version of remark 799 void do_remark_non_parallel(); 800 // Reference processing work routine (during second checkpoint) 801 void refProcessingWork(); 802 803 // Concurrent sweeping work 804 void sweepWork(ConcurrentMarkSweepGeneration* gen); 805 806 // (Concurrent) resetting of support data structures 807 void reset(bool concurrent); 808 809 // Clear _expansion_cause fields of constituent generations 810 void clear_expansion_cause(); 811 812 // An auxiliary method used to record the ends of 813 // used regions of each generation to limit the extent of sweep 814 void save_sweep_limits(); 815 816 // A work method used by the foreground collector to do 817 // a mark-sweep-compact. 818 void do_compaction_work(bool clear_all_soft_refs); 819 820 // Work methods for reporting concurrent mode interruption or failure 821 bool is_external_interruption(); 822 void report_concurrent_mode_interruption(); 823 824 // If the background GC is active, acquire control from the background 825 // GC and do the collection. 826 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 827 828 // For synchronizing passing of control from background to foreground 829 // GC. waitForForegroundGC() is called by the background 830 // collector. It if had to wait for a foreground collection, 831 // it returns true and the background collection should assume 832 // that the collection was finished by the foreground 833 // collector. 834 bool waitForForegroundGC(); 835 836 size_t block_size_using_printezis_bits(HeapWord* addr) const; 837 size_t block_size_if_printezis_bits(HeapWord* addr) const; 838 HeapWord* next_card_start_after_block(HeapWord* addr) const; 839 840 void setup_cms_unloading_and_verification_state(); 841 public: 842 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 843 CardTableRS* ct, 844 ConcurrentMarkSweepPolicy* cp); 845 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 846 847 ReferenceProcessor* ref_processor() { return _ref_processor; } 848 void ref_processor_init(); 849 850 Mutex* bitMapLock() const { return _markBitMap.lock(); } 851 static CollectorState abstract_state() { return _collectorState; } 852 853 bool should_abort_preclean() const; // Whether preclean should be aborted. 854 size_t get_eden_used() const; 855 size_t get_eden_capacity() const; 856 857 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 858 859 // Locking checks 860 NOT_PRODUCT(static bool have_cms_token();) 861 862 bool shouldConcurrentCollect(); 863 864 void collect(bool full, 865 bool clear_all_soft_refs, 866 size_t size, 867 bool tlab); 868 void collect_in_background(GCCause::Cause cause); 869 870 // In support of ExplicitGCInvokesConcurrent 871 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 872 // Should we unload classes in a particular concurrent cycle? 873 bool should_unload_classes() const { 874 return _should_unload_classes; 875 } 876 void update_should_unload_classes(); 877 878 void direct_allocated(HeapWord* start, size_t size); 879 880 // Object is dead if not marked and current phase is sweeping. 881 bool is_dead_obj(oop obj) const; 882 883 // After a promotion (of "start"), do any necessary marking. 884 // If "par", then it's being done by a parallel GC thread. 885 // The last two args indicate if we need precise marking 886 // and if so the size of the object so it can be dirtied 887 // in its entirety. 888 void promoted(bool par, HeapWord* start, 889 bool is_obj_array, size_t obj_size); 890 891 void getFreelistLocks() const; 892 void releaseFreelistLocks() const; 893 bool haveFreelistLocks() const; 894 895 // Adjust size of underlying generation 896 void compute_new_size(); 897 898 // GC prologue and epilogue 899 void gc_prologue(bool full); 900 void gc_epilogue(bool full); 901 902 jlong time_of_last_gc(jlong now) { 903 if (_collectorState <= Idling) { 904 // gc not in progress 905 return _time_of_last_gc; 906 } else { 907 // collection in progress 908 return now; 909 } 910 } 911 912 // Support for parallel remark of survivor space 913 void* get_data_recorder(int thr_num); 914 void sample_eden_chunk(); 915 916 CMSBitMap* markBitMap() { return &_markBitMap; } 917 void directAllocated(HeapWord* start, size_t size); 918 919 // Main CMS steps and related support 920 void checkpointRootsInitial(); 921 bool markFromRoots(); // a return value of false indicates failure 922 // due to stack overflow 923 void preclean(); 924 void checkpointRootsFinal(); 925 void sweep(); 926 927 // Check that the currently executing thread is the expected 928 // one (foreground collector or background collector). 929 static void check_correct_thread_executing() PRODUCT_RETURN; 930 931 bool is_cms_reachable(HeapWord* addr); 932 933 // Performance Counter Support 934 CollectorCounters* counters() { return _gc_counters; } 935 936 // Timer stuff 937 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 938 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 939 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 940 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } 941 942 int yields() { return _numYields; } 943 void resetYields() { _numYields = 0; } 944 void incrementYields() { _numYields++; } 945 void resetNumDirtyCards() { _numDirtyCards = 0; } 946 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 947 size_t numDirtyCards() { return _numDirtyCards; } 948 949 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 950 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 951 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 952 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 953 size_t sweep_count() const { return _sweep_count; } 954 void increment_sweep_count() { _sweep_count++; } 955 956 // Timers/stats for gc scheduling and incremental mode pacing. 957 CMSStats& stats() { return _stats; } 958 959 // Adaptive size policy 960 AdaptiveSizePolicy* size_policy(); 961 962 static void print_on_error(outputStream* st); 963 964 // Debugging 965 void verify(); 966 bool verify_after_remark(bool silent = VerifySilently); 967 void verify_ok_to_terminate() const PRODUCT_RETURN; 968 void verify_work_stacks_empty() const PRODUCT_RETURN; 969 void verify_overflow_empty() const PRODUCT_RETURN; 970 971 // Convenience methods in support of debugging 972 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 973 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 974 975 // Accessors 976 CMSMarkStack* verification_mark_stack() { return &_markStack; } 977 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 978 979 // Initialization errors 980 bool completed_initialization() { return _completed_initialization; } 981 982 void print_eden_and_survivor_chunk_arrays(); 983 }; 984 985 class CMSExpansionCause : public AllStatic { 986 public: 987 enum Cause { 988 _no_expansion, 989 _satisfy_free_ratio, 990 _satisfy_promotion, 991 _satisfy_allocation, 992 _allocate_par_lab, 993 _allocate_par_spooling_space, 994 _adaptive_size_policy 995 }; 996 // Return a string describing the cause of the expansion. 997 static const char* to_string(CMSExpansionCause::Cause cause); 998 }; 999 1000 class ConcurrentMarkSweepGeneration: public CardGeneration { 1001 friend class VMStructs; 1002 friend class ConcurrentMarkSweepThread; 1003 friend class ConcurrentMarkSweep; 1004 friend class CMSCollector; 1005 protected: 1006 static CMSCollector* _collector; // the collector that collects us 1007 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1008 1009 // Performance Counters 1010 GenerationCounters* _gen_counters; 1011 GSpaceCounters* _space_counters; 1012 1013 // Words directly allocated, used by CMSStats. 1014 size_t _direct_allocated_words; 1015 1016 // Non-product stat counters 1017 NOT_PRODUCT( 1018 size_t _numObjectsPromoted; 1019 size_t _numWordsPromoted; 1020 size_t _numObjectsAllocated; 1021 size_t _numWordsAllocated; 1022 ) 1023 1024 // Used for sizing decisions 1025 bool _incremental_collection_failed; 1026 bool incremental_collection_failed() { 1027 return _incremental_collection_failed; 1028 } 1029 void set_incremental_collection_failed() { 1030 _incremental_collection_failed = true; 1031 } 1032 void clear_incremental_collection_failed() { 1033 _incremental_collection_failed = false; 1034 } 1035 1036 // accessors 1037 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1038 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1039 1040 // Accessing spaces 1041 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } 1042 1043 private: 1044 // For parallel young-gen GC support. 1045 CMSParGCThreadState** _par_gc_thread_states; 1046 1047 // Reason generation was expanded 1048 CMSExpansionCause::Cause _expansion_cause; 1049 1050 // In support of MinChunkSize being larger than min object size 1051 const double _dilatation_factor; 1052 1053 // True if a compacting collection was done. 1054 bool _did_compact; 1055 bool did_compact() { return _did_compact; } 1056 1057 // Fraction of current occupancy at which to start a CMS collection which 1058 // will collect this generation (at least). 1059 double _initiating_occupancy; 1060 1061 protected: 1062 // Shrink generation by specified size (returns false if unable to shrink) 1063 void shrink_free_list_by(size_t bytes); 1064 1065 // Update statistics for GC 1066 virtual void update_gc_stats(int level, bool full); 1067 1068 // Maximum available space in the generation (including uncommitted) 1069 // space. 1070 size_t max_available() const; 1071 1072 // getter and initializer for _initiating_occupancy field. 1073 double initiating_occupancy() const { return _initiating_occupancy; } 1074 void init_initiating_occupancy(intx io, uintx tr); 1075 1076 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1077 1078 void assert_correct_size_change_locking(); 1079 1080 public: 1081 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1082 int level, CardTableRS* ct, 1083 bool use_adaptive_freelists, 1084 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 1085 1086 // Accessors 1087 CMSCollector* collector() const { return _collector; } 1088 static void set_collector(CMSCollector* collector) { 1089 assert(_collector == NULL, "already set"); 1090 _collector = collector; 1091 } 1092 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1093 1094 Mutex* freelistLock() const; 1095 1096 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1097 1098 void set_did_compact(bool v) { _did_compact = v; } 1099 1100 bool refs_discovery_is_atomic() const { return false; } 1101 bool refs_discovery_is_mt() const { 1102 // Note: CMS does MT-discovery during the parallel-remark 1103 // phases. Use ReferenceProcessorMTMutator to make refs 1104 // discovery MT-safe during such phases or other parallel 1105 // discovery phases in the future. This may all go away 1106 // if/when we decide that refs discovery is sufficiently 1107 // rare that the cost of the CAS's involved is in the 1108 // noise. That's a measurement that should be done, and 1109 // the code simplified if that turns out to be the case. 1110 return ConcGCThreads > 1; 1111 } 1112 1113 // Override 1114 virtual void ref_processor_init(); 1115 1116 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1117 1118 // Space enquiries 1119 double occupancy() const { return ((double)used())/((double)capacity()); } 1120 size_t contiguous_available() const; 1121 size_t unsafe_max_alloc_nogc() const; 1122 1123 // over-rides 1124 MemRegion used_region_at_save_marks() const; 1125 1126 // Does a "full" (forced) collection invoked on this generation collect 1127 // all younger generations as well? Note that the second conjunct is a 1128 // hack to allow the collection of the younger gen first if the flag is 1129 // set. 1130 virtual bool full_collects_younger_generations() const { 1131 return !ScavengeBeforeFullGC; 1132 } 1133 1134 // Adjust quantities in the generation affected by 1135 // the compaction. 1136 void reset_after_compaction(); 1137 1138 // Allocation support 1139 HeapWord* allocate(size_t size, bool tlab); 1140 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1141 oop promote(oop obj, size_t obj_size); 1142 HeapWord* par_allocate(size_t size, bool tlab) { 1143 return allocate(size, tlab); 1144 } 1145 1146 1147 // Used by CMSStats to track direct allocation. The value is sampled and 1148 // reset after each young gen collection. 1149 size_t direct_allocated_words() const { return _direct_allocated_words; } 1150 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1151 1152 // Overrides for parallel promotion. 1153 virtual oop par_promote(int thread_num, 1154 oop obj, markOop m, size_t word_sz); 1155 virtual void par_promote_alloc_done(int thread_num); 1156 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1157 1158 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1159 1160 // Inform this (non-young) generation that a promotion failure was 1161 // encountered during a collection of a younger generation that 1162 // promotes into this generation. 1163 virtual void promotion_failure_occurred(); 1164 1165 bool should_collect(bool full, size_t size, bool tlab); 1166 virtual bool should_concurrent_collect() const; 1167 virtual bool is_too_full() const; 1168 void collect(bool full, 1169 bool clear_all_soft_refs, 1170 size_t size, 1171 bool tlab); 1172 1173 HeapWord* expand_and_allocate(size_t word_size, 1174 bool tlab, 1175 bool parallel = false); 1176 1177 // GC prologue and epilogue 1178 void gc_prologue(bool full); 1179 void gc_prologue_work(bool full, bool registerClosure, 1180 ModUnionClosure* modUnionClosure); 1181 void gc_epilogue(bool full); 1182 void gc_epilogue_work(bool full); 1183 1184 // Time since last GC of this generation 1185 jlong time_of_last_gc(jlong now) { 1186 return collector()->time_of_last_gc(now); 1187 } 1188 void update_time_of_last_gc(jlong now) { 1189 collector()-> update_time_of_last_gc(now); 1190 } 1191 1192 // Allocation failure 1193 void shrink(size_t bytes); 1194 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1195 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1196 1197 // Iteration support and related enquiries 1198 void save_marks(); 1199 bool no_allocs_since_save_marks(); 1200 1201 // Iteration support specific to CMS generations 1202 void save_sweep_limit(); 1203 1204 // More iteration support 1205 virtual void oop_iterate(ExtendedOopClosure* cl); 1206 virtual void safe_object_iterate(ObjectClosure* cl); 1207 virtual void object_iterate(ObjectClosure* cl); 1208 1209 // Need to declare the full complement of closures, whether we'll 1210 // override them or not, or get message from the compiler: 1211 // oop_since_save_marks_iterate_nv hides virtual function... 1212 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1213 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1214 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1215 1216 // Smart allocation XXX -- move to CFLSpace? 1217 void setNearLargestChunk(); 1218 bool isNearLargestChunk(HeapWord* addr); 1219 1220 // Get the chunk at the end of the space. Delegates to 1221 // the space. 1222 FreeChunk* find_chunk_at_end(); 1223 1224 void post_compact(); 1225 1226 // Debugging 1227 void prepare_for_verify(); 1228 void verify(); 1229 void print_statistics() PRODUCT_RETURN; 1230 1231 // Performance Counters support 1232 virtual void update_counters(); 1233 virtual void update_counters(size_t used); 1234 void initialize_performance_counters(); 1235 CollectorCounters* counters() { return collector()->counters(); } 1236 1237 // Support for parallel remark of survivor space 1238 void* get_data_recorder(int thr_num) { 1239 //Delegate to collector 1240 return collector()->get_data_recorder(thr_num); 1241 } 1242 void sample_eden_chunk() { 1243 //Delegate to collector 1244 return collector()->sample_eden_chunk(); 1245 } 1246 1247 // Printing 1248 const char* name() const; 1249 virtual const char* short_name() const { return "CMS"; } 1250 void print() const; 1251 void printOccupancy(const char* s); 1252 1253 // Resize the generation after a compacting GC. The 1254 // generation can be treated as a contiguous space 1255 // after the compaction. 1256 virtual void compute_new_size(); 1257 // Resize the generation after a non-compacting 1258 // collection. 1259 void compute_new_size_free_list(); 1260 }; 1261 1262 // 1263 // Closures of various sorts used by CMS to accomplish its work 1264 // 1265 1266 // This closure is used to do concurrent marking from the roots 1267 // following the first checkpoint. 1268 class MarkFromRootsClosure: public BitMapClosure { 1269 CMSCollector* _collector; 1270 MemRegion _span; 1271 CMSBitMap* _bitMap; 1272 CMSBitMap* _mut; 1273 CMSMarkStack* _markStack; 1274 bool _yield; 1275 int _skipBits; 1276 HeapWord* _finger; 1277 HeapWord* _threshold; 1278 DEBUG_ONLY(bool _verifying;) 1279 1280 public: 1281 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1282 CMSBitMap* bitMap, 1283 CMSMarkStack* markStack, 1284 bool should_yield, bool verifying = false); 1285 bool do_bit(size_t offset); 1286 void reset(HeapWord* addr); 1287 inline void do_yield_check(); 1288 1289 private: 1290 void scanOopsInOop(HeapWord* ptr); 1291 void do_yield_work(); 1292 }; 1293 1294 // This closure is used to do concurrent multi-threaded 1295 // marking from the roots following the first checkpoint. 1296 // XXX This should really be a subclass of The serial version 1297 // above, but i have not had the time to refactor things cleanly. 1298 class Par_MarkFromRootsClosure: public BitMapClosure { 1299 CMSCollector* _collector; 1300 MemRegion _whole_span; 1301 MemRegion _span; 1302 CMSBitMap* _bit_map; 1303 CMSBitMap* _mut; 1304 OopTaskQueue* _work_queue; 1305 CMSMarkStack* _overflow_stack; 1306 int _skip_bits; 1307 HeapWord* _finger; 1308 HeapWord* _threshold; 1309 CMSConcMarkingTask* _task; 1310 public: 1311 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1312 MemRegion span, 1313 CMSBitMap* bit_map, 1314 OopTaskQueue* work_queue, 1315 CMSMarkStack* overflow_stack); 1316 bool do_bit(size_t offset); 1317 inline void do_yield_check(); 1318 1319 private: 1320 void scan_oops_in_oop(HeapWord* ptr); 1321 void do_yield_work(); 1322 bool get_work_from_overflow_stack(); 1323 }; 1324 1325 // The following closures are used to do certain kinds of verification of 1326 // CMS marking. 1327 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1328 CMSCollector* _collector; 1329 MemRegion _span; 1330 CMSBitMap* _verification_bm; 1331 CMSBitMap* _cms_bm; 1332 CMSMarkStack* _mark_stack; 1333 protected: 1334 void do_oop(oop p); 1335 template <class T> inline void do_oop_work(T *p) { 1336 oop obj = oopDesc::load_decode_heap_oop(p); 1337 do_oop(obj); 1338 } 1339 public: 1340 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1341 MemRegion span, 1342 CMSBitMap* verification_bm, 1343 CMSBitMap* cms_bm, 1344 CMSMarkStack* mark_stack); 1345 void do_oop(oop* p); 1346 void do_oop(narrowOop* p); 1347 1348 // Deal with a stack overflow condition 1349 void handle_stack_overflow(HeapWord* lost); 1350 }; 1351 1352 class MarkFromRootsVerifyClosure: public BitMapClosure { 1353 CMSCollector* _collector; 1354 MemRegion _span; 1355 CMSBitMap* _verification_bm; 1356 CMSBitMap* _cms_bm; 1357 CMSMarkStack* _mark_stack; 1358 HeapWord* _finger; 1359 PushAndMarkVerifyClosure _pam_verify_closure; 1360 public: 1361 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1362 CMSBitMap* verification_bm, 1363 CMSBitMap* cms_bm, 1364 CMSMarkStack* mark_stack); 1365 bool do_bit(size_t offset); 1366 void reset(HeapWord* addr); 1367 }; 1368 1369 1370 // This closure is used to check that a certain set of bits is 1371 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1372 class FalseBitMapClosure: public BitMapClosure { 1373 public: 1374 bool do_bit(size_t offset) { 1375 guarantee(false, "Should not have a 1 bit"); 1376 return true; 1377 } 1378 }; 1379 1380 // A version of ObjectClosure with "memory" (see _previous_address below) 1381 class UpwardsObjectClosure: public BoolObjectClosure { 1382 HeapWord* _previous_address; 1383 public: 1384 UpwardsObjectClosure() : _previous_address(NULL) { } 1385 void set_previous(HeapWord* addr) { _previous_address = addr; } 1386 HeapWord* previous() { return _previous_address; } 1387 // A return value of "true" can be used by the caller to decide 1388 // if this object's end should *NOT* be recorded in 1389 // _previous_address above. 1390 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1391 }; 1392 1393 // This closure is used during the second checkpointing phase 1394 // to rescan the marked objects on the dirty cards in the mod 1395 // union table and the card table proper. It's invoked via 1396 // MarkFromDirtyCardsClosure below. It uses either 1397 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1398 // declared in genOopClosures.hpp to accomplish some of its work. 1399 // In the parallel case the bitMap is shared, so access to 1400 // it needs to be suitably synchronized for updates by embedded 1401 // closures that update it; however, this closure itself only 1402 // reads the bit_map and because it is idempotent, is immune to 1403 // reading stale values. 1404 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1405 #ifdef ASSERT 1406 CMSCollector* _collector; 1407 MemRegion _span; 1408 union { 1409 CMSMarkStack* _mark_stack; 1410 OopTaskQueue* _work_queue; 1411 }; 1412 #endif // ASSERT 1413 bool _parallel; 1414 CMSBitMap* _bit_map; 1415 union { 1416 MarkRefsIntoAndScanClosure* _scan_closure; 1417 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1418 }; 1419 1420 public: 1421 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1422 MemRegion span, 1423 ReferenceProcessor* rp, 1424 CMSBitMap* bit_map, 1425 CMSMarkStack* mark_stack, 1426 MarkRefsIntoAndScanClosure* cl): 1427 #ifdef ASSERT 1428 _collector(collector), 1429 _span(span), 1430 _mark_stack(mark_stack), 1431 #endif // ASSERT 1432 _parallel(false), 1433 _bit_map(bit_map), 1434 _scan_closure(cl) { } 1435 1436 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1437 MemRegion span, 1438 ReferenceProcessor* rp, 1439 CMSBitMap* bit_map, 1440 OopTaskQueue* work_queue, 1441 Par_MarkRefsIntoAndScanClosure* cl): 1442 #ifdef ASSERT 1443 _collector(collector), 1444 _span(span), 1445 _work_queue(work_queue), 1446 #endif // ASSERT 1447 _parallel(true), 1448 _bit_map(bit_map), 1449 _par_scan_closure(cl) { } 1450 1451 bool do_object_b(oop obj) { 1452 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1453 return false; 1454 } 1455 bool do_object_bm(oop p, MemRegion mr); 1456 }; 1457 1458 // This closure is used during the second checkpointing phase 1459 // to rescan the marked objects on the dirty cards in the mod 1460 // union table and the card table proper. It invokes 1461 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1462 // In the parallel case, the bit map is shared and requires 1463 // synchronized access. 1464 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1465 CompactibleFreeListSpace* _space; 1466 ScanMarkedObjectsAgainClosure _scan_cl; 1467 size_t _num_dirty_cards; 1468 1469 public: 1470 MarkFromDirtyCardsClosure(CMSCollector* collector, 1471 MemRegion span, 1472 CompactibleFreeListSpace* space, 1473 CMSBitMap* bit_map, 1474 CMSMarkStack* mark_stack, 1475 MarkRefsIntoAndScanClosure* cl): 1476 _space(space), 1477 _num_dirty_cards(0), 1478 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1479 mark_stack, cl) { } 1480 1481 MarkFromDirtyCardsClosure(CMSCollector* collector, 1482 MemRegion span, 1483 CompactibleFreeListSpace* space, 1484 CMSBitMap* bit_map, 1485 OopTaskQueue* work_queue, 1486 Par_MarkRefsIntoAndScanClosure* cl): 1487 _space(space), 1488 _num_dirty_cards(0), 1489 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1490 work_queue, cl) { } 1491 1492 void do_MemRegion(MemRegion mr); 1493 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1494 size_t num_dirty_cards() { return _num_dirty_cards; } 1495 }; 1496 1497 // This closure is used in the non-product build to check 1498 // that there are no MemRegions with a certain property. 1499 class FalseMemRegionClosure: public MemRegionClosure { 1500 void do_MemRegion(MemRegion mr) { 1501 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1502 guarantee(false, "Should never be here"); 1503 } 1504 }; 1505 1506 // This closure is used during the precleaning phase 1507 // to "carefully" rescan marked objects on dirty cards. 1508 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1509 // to accomplish some of its work. 1510 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1511 CMSCollector* _collector; 1512 MemRegion _span; 1513 bool _yield; 1514 Mutex* _freelistLock; 1515 CMSBitMap* _bitMap; 1516 CMSMarkStack* _markStack; 1517 MarkRefsIntoAndScanClosure* _scanningClosure; 1518 1519 public: 1520 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1521 MemRegion span, 1522 CMSBitMap* bitMap, 1523 CMSMarkStack* markStack, 1524 MarkRefsIntoAndScanClosure* cl, 1525 bool should_yield): 1526 _collector(collector), 1527 _span(span), 1528 _yield(should_yield), 1529 _bitMap(bitMap), 1530 _markStack(markStack), 1531 _scanningClosure(cl) { 1532 } 1533 1534 void do_object(oop p) { 1535 guarantee(false, "call do_object_careful instead"); 1536 } 1537 1538 size_t do_object_careful(oop p) { 1539 guarantee(false, "Unexpected caller"); 1540 return 0; 1541 } 1542 1543 size_t do_object_careful_m(oop p, MemRegion mr); 1544 1545 void setFreelistLock(Mutex* m) { 1546 _freelistLock = m; 1547 _scanningClosure->set_freelistLock(m); 1548 } 1549 1550 private: 1551 inline bool do_yield_check(); 1552 1553 void do_yield_work(); 1554 }; 1555 1556 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1557 CMSCollector* _collector; 1558 MemRegion _span; 1559 bool _yield; 1560 CMSBitMap* _bit_map; 1561 CMSMarkStack* _mark_stack; 1562 PushAndMarkClosure* _scanning_closure; 1563 unsigned int _before_count; 1564 1565 public: 1566 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1567 MemRegion span, 1568 CMSBitMap* bit_map, 1569 CMSMarkStack* mark_stack, 1570 PushAndMarkClosure* cl, 1571 unsigned int before_count, 1572 bool should_yield): 1573 _collector(collector), 1574 _span(span), 1575 _yield(should_yield), 1576 _bit_map(bit_map), 1577 _mark_stack(mark_stack), 1578 _scanning_closure(cl), 1579 _before_count(before_count) 1580 { } 1581 1582 void do_object(oop p) { 1583 guarantee(false, "call do_object_careful instead"); 1584 } 1585 1586 size_t do_object_careful(oop p); 1587 1588 size_t do_object_careful_m(oop p, MemRegion mr) { 1589 guarantee(false, "Unexpected caller"); 1590 return 0; 1591 } 1592 1593 private: 1594 inline void do_yield_check(); 1595 void do_yield_work(); 1596 }; 1597 1598 // This closure is used to accomplish the sweeping work 1599 // after the second checkpoint but before the concurrent reset 1600 // phase. 1601 // 1602 // Terminology 1603 // left hand chunk (LHC) - block of one or more chunks currently being 1604 // coalesced. The LHC is available for coalescing with a new chunk. 1605 // right hand chunk (RHC) - block that is currently being swept that is 1606 // free or garbage that can be coalesced with the LHC. 1607 // _inFreeRange is true if there is currently a LHC 1608 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1609 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1610 // _freeFinger is the address of the current LHC 1611 class SweepClosure: public BlkClosureCareful { 1612 CMSCollector* _collector; // collector doing the work 1613 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1614 CompactibleFreeListSpace* _sp; // Space being swept 1615 HeapWord* _limit;// the address at or above which the sweep should stop 1616 // because we do not expect newly garbage blocks 1617 // eligible for sweeping past that address. 1618 Mutex* _freelistLock; // Free list lock (in space) 1619 CMSBitMap* _bitMap; // Marking bit map (in 1620 // generation) 1621 bool _inFreeRange; // Indicates if we are in the 1622 // midst of a free run 1623 bool _freeRangeInFreeLists; 1624 // Often, we have just found 1625 // a free chunk and started 1626 // a new free range; we do not 1627 // eagerly remove this chunk from 1628 // the free lists unless there is 1629 // a possibility of coalescing. 1630 // When true, this flag indicates 1631 // that the _freeFinger below 1632 // points to a potentially free chunk 1633 // that may still be in the free lists 1634 bool _lastFreeRangeCoalesced; 1635 // free range contains chunks 1636 // coalesced 1637 bool _yield; 1638 // Whether sweeping should be 1639 // done with yields. For instance 1640 // when done by the foreground 1641 // collector we shouldn't yield. 1642 HeapWord* _freeFinger; // When _inFreeRange is set, the 1643 // pointer to the "left hand 1644 // chunk" 1645 size_t _freeRangeSize; 1646 // When _inFreeRange is set, this 1647 // indicates the accumulated size 1648 // of the "left hand chunk" 1649 NOT_PRODUCT( 1650 size_t _numObjectsFreed; 1651 size_t _numWordsFreed; 1652 size_t _numObjectsLive; 1653 size_t _numWordsLive; 1654 size_t _numObjectsAlreadyFree; 1655 size_t _numWordsAlreadyFree; 1656 FreeChunk* _last_fc; 1657 ) 1658 private: 1659 // Code that is common to a free chunk or garbage when 1660 // encountered during sweeping. 1661 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1662 // Process a free chunk during sweeping. 1663 void do_already_free_chunk(FreeChunk *fc); 1664 // Work method called when processing an already free or a 1665 // freshly garbage chunk to do a lookahead and possibly a 1666 // preemptive flush if crossing over _limit. 1667 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1668 // Process a garbage chunk during sweeping. 1669 size_t do_garbage_chunk(FreeChunk *fc); 1670 // Process a live chunk during sweeping. 1671 size_t do_live_chunk(FreeChunk* fc); 1672 1673 // Accessors. 1674 HeapWord* freeFinger() const { return _freeFinger; } 1675 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1676 bool inFreeRange() const { return _inFreeRange; } 1677 void set_inFreeRange(bool v) { _inFreeRange = v; } 1678 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1679 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1680 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1681 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1682 1683 // Initialize a free range. 1684 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1685 // Return this chunk to the free lists. 1686 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1687 1688 // Check if we should yield and do so when necessary. 1689 inline void do_yield_check(HeapWord* addr); 1690 1691 // Yield 1692 void do_yield_work(HeapWord* addr); 1693 1694 // Debugging/Printing 1695 void print_free_block_coalesced(FreeChunk* fc) const; 1696 1697 public: 1698 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1699 CMSBitMap* bitMap, bool should_yield); 1700 ~SweepClosure() PRODUCT_RETURN; 1701 1702 size_t do_blk_careful(HeapWord* addr); 1703 void print() const { print_on(tty); } 1704 void print_on(outputStream *st) const; 1705 }; 1706 1707 // Closures related to weak references processing 1708 1709 // During CMS' weak reference processing, this is a 1710 // work-routine/closure used to complete transitive 1711 // marking of objects as live after a certain point 1712 // in which an initial set has been completely accumulated. 1713 // This closure is currently used both during the final 1714 // remark stop-world phase, as well as during the concurrent 1715 // precleaning of the discovered reference lists. 1716 class CMSDrainMarkingStackClosure: public VoidClosure { 1717 CMSCollector* _collector; 1718 MemRegion _span; 1719 CMSMarkStack* _mark_stack; 1720 CMSBitMap* _bit_map; 1721 CMSKeepAliveClosure* _keep_alive; 1722 bool _concurrent_precleaning; 1723 public: 1724 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1725 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1726 CMSKeepAliveClosure* keep_alive, 1727 bool cpc): 1728 _collector(collector), 1729 _span(span), 1730 _bit_map(bit_map), 1731 _mark_stack(mark_stack), 1732 _keep_alive(keep_alive), 1733 _concurrent_precleaning(cpc) { 1734 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1735 "Mismatch"); 1736 } 1737 1738 void do_void(); 1739 }; 1740 1741 // A parallel version of CMSDrainMarkingStackClosure above. 1742 class CMSParDrainMarkingStackClosure: public VoidClosure { 1743 CMSCollector* _collector; 1744 MemRegion _span; 1745 OopTaskQueue* _work_queue; 1746 CMSBitMap* _bit_map; 1747 CMSInnerParMarkAndPushClosure _mark_and_push; 1748 1749 public: 1750 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1751 MemRegion span, CMSBitMap* bit_map, 1752 OopTaskQueue* work_queue): 1753 _collector(collector), 1754 _span(span), 1755 _bit_map(bit_map), 1756 _work_queue(work_queue), 1757 _mark_and_push(collector, span, bit_map, work_queue) { } 1758 1759 public: 1760 void trim_queue(uint max); 1761 void do_void(); 1762 }; 1763 1764 // Allow yielding or short-circuiting of reference list 1765 // precleaning work. 1766 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1767 CMSCollector* _collector; 1768 void do_yield_work(); 1769 public: 1770 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1771 _collector(collector) {} 1772 virtual bool should_return(); 1773 }; 1774 1775 1776 // Convenience class that locks free list locks for given CMS collector 1777 class FreelistLocker: public StackObj { 1778 private: 1779 CMSCollector* _collector; 1780 public: 1781 FreelistLocker(CMSCollector* collector): 1782 _collector(collector) { 1783 _collector->getFreelistLocks(); 1784 } 1785 1786 ~FreelistLocker() { 1787 _collector->releaseFreelistLocks(); 1788 } 1789 }; 1790 1791 // Mark all dead objects in a given space. 1792 class MarkDeadObjectsClosure: public BlkClosure { 1793 const CMSCollector* _collector; 1794 const CompactibleFreeListSpace* _sp; 1795 CMSBitMap* _live_bit_map; 1796 CMSBitMap* _dead_bit_map; 1797 public: 1798 MarkDeadObjectsClosure(const CMSCollector* collector, 1799 const CompactibleFreeListSpace* sp, 1800 CMSBitMap *live_bit_map, 1801 CMSBitMap *dead_bit_map) : 1802 _collector(collector), 1803 _sp(sp), 1804 _live_bit_map(live_bit_map), 1805 _dead_bit_map(dead_bit_map) {} 1806 size_t do_blk(HeapWord* addr); 1807 }; 1808 1809 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1810 1811 public: 1812 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1813 }; 1814 1815 1816 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP