1 /* 2 * Copyright (c) 2001, 2018, 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_CMS_CONCURRENTMARKSWEEPGENERATION_HPP 26 #define SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP 27 28 #include "gc/cms/cmsOopClosures.hpp" 29 #include "gc/cms/gSpaceCounters.hpp" 30 #include "gc/cms/yieldingWorkgroup.hpp" 31 #include "gc/shared/cardGeneration.hpp" 32 #include "gc/shared/gcHeapSummary.hpp" 33 #include "gc/shared/gcStats.hpp" 34 #include "gc/shared/gcWhen.hpp" 35 #include "gc/shared/generationCounters.hpp" 36 #include "gc/shared/space.hpp" 37 #include "gc/shared/taskqueue.hpp" 38 #include "logging/log.hpp" 39 #include "memory/iterator.hpp" 40 #include "memory/virtualspace.hpp" 41 #include "runtime/mutexLocker.hpp" 42 #include "services/memoryService.hpp" 43 #include "utilities/bitMap.hpp" 44 #include "utilities/stack.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 ConcurrentMarkSweepThread; 66 class CompactibleFreeListSpace; 67 class FreeChunk; 68 class ParNewGeneration; 69 class PromotionInfo; 70 class ScanMarkedObjectsAgainCarefullyClosure; 71 class TenuredGeneration; 72 class SerialOldTracer; 73 74 // A generic CMS bit map. It's the basis for both the CMS marking bit map 75 // as well as for the mod union table (in each case only a subset of the 76 // methods are used). This is essentially a wrapper around the BitMap class, 77 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 78 // we have _shifter == 0. and for the mod union table we have 79 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 80 // XXX 64-bit issues in BitMap? 81 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 82 friend class VMStructs; 83 84 HeapWord* _bmStartWord; // base address of range covered by map 85 size_t _bmWordSize; // map size (in #HeapWords covered) 86 const int _shifter; // shifts to convert HeapWord to bit position 87 VirtualSpace _virtual_space; // underlying the bit map 88 BitMapView _bm; // the bit map itself 89 Mutex* const _lock; // mutex protecting _bm; 90 91 public: 92 // constructor 93 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 94 95 // allocates the actual storage for the map 96 bool allocate(MemRegion mr); 97 // field getter 98 Mutex* lock() const { return _lock; } 99 // locking verifier convenience function 100 void assert_locked() const PRODUCT_RETURN; 101 102 // inquiries 103 HeapWord* startWord() const { return _bmStartWord; } 104 size_t sizeInWords() const { return _bmWordSize; } 105 size_t sizeInBits() const { return _bm.size(); } 106 // the following is one past the last word in space 107 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 108 109 // reading marks 110 bool isMarked(HeapWord* addr) const; 111 bool par_isMarked(HeapWord* addr) const; // do not lock checks 112 bool isUnmarked(HeapWord* addr) const; 113 bool isAllClear() const; 114 115 // writing marks 116 void mark(HeapWord* addr); 117 // For marking by parallel GC threads; 118 // returns true if we did, false if another thread did 119 bool par_mark(HeapWord* addr); 120 121 void mark_range(MemRegion mr); 122 void par_mark_range(MemRegion mr); 123 void mark_large_range(MemRegion mr); 124 void par_mark_large_range(MemRegion mr); 125 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 126 void clear_range(MemRegion mr); 127 void par_clear_range(MemRegion mr); 128 void clear_large_range(MemRegion mr); 129 void par_clear_large_range(MemRegion mr); 130 void clear_all(); 131 void clear_all_incrementally(); // Not yet implemented!! 132 133 NOT_PRODUCT( 134 // checks the memory region for validity 135 void region_invariant(MemRegion mr); 136 ) 137 138 // iteration 139 void iterate(BitMapClosure* cl) { 140 _bm.iterate(cl); 141 } 142 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 143 void dirty_range_iterate_clear(MemRegionClosure* cl); 144 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 145 146 // auxiliary support for iteration 147 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 148 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 149 HeapWord* end_addr) const; 150 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 151 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 152 HeapWord* end_addr) const; 153 MemRegion getAndClearMarkedRegion(HeapWord* addr); 154 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 155 HeapWord* end_addr); 156 157 // conversion utilities 158 HeapWord* offsetToHeapWord(size_t offset) const; 159 size_t heapWordToOffset(HeapWord* addr) const; 160 size_t heapWordDiffToOffsetDiff(size_t diff) const; 161 162 void print_on_error(outputStream* st, const char* prefix) const; 163 164 // debugging 165 // is this address range covered by the bit-map? 166 NOT_PRODUCT( 167 bool covers(MemRegion mr) const; 168 bool covers(HeapWord* start, size_t size = 0) const; 169 ) 170 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 171 }; 172 173 // Represents a marking stack used by the CMS collector. 174 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 175 class CMSMarkStack: public CHeapObj<mtGC> { 176 friend class CMSCollector; // To get at expansion stats further below. 177 178 VirtualSpace _virtual_space; // Space for the stack 179 oop* _base; // Bottom of stack 180 size_t _index; // One more than last occupied index 181 size_t _capacity; // Max #elements 182 Mutex _par_lock; // An advisory lock used in case of parallel access 183 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run 184 185 protected: 186 size_t _hit_limit; // We hit max stack size limit 187 size_t _failed_double; // We failed expansion before hitting limit 188 189 public: 190 CMSMarkStack(): 191 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true, 192 Monitor::_safepoint_check_never), 193 _hit_limit(0), 194 _failed_double(0) {} 195 196 bool allocate(size_t size); 197 198 size_t capacity() const { return _capacity; } 199 200 oop pop() { 201 if (!isEmpty()) { 202 return _base[--_index] ; 203 } 204 return NULL; 205 } 206 207 bool push(oop ptr) { 208 if (isFull()) { 209 return false; 210 } else { 211 _base[_index++] = ptr; 212 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 213 return true; 214 } 215 } 216 217 bool isEmpty() const { return _index == 0; } 218 bool isFull() const { 219 assert(_index <= _capacity, "buffer overflow"); 220 return _index == _capacity; 221 } 222 223 size_t length() { return _index; } 224 225 // "Parallel versions" of some of the above 226 oop par_pop() { 227 // lock and pop 228 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 229 return pop(); 230 } 231 232 bool par_push(oop ptr) { 233 // lock and push 234 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 235 return push(ptr); 236 } 237 238 // Forcibly reset the stack, losing all of its contents. 239 void reset() { 240 _index = 0; 241 } 242 243 // Expand the stack, typically in response to an overflow condition. 244 void expand(); 245 246 // Compute the least valued stack element. 247 oop least_value(HeapWord* low) { 248 HeapWord* least = low; 249 for (size_t i = 0; i < _index; i++) { 250 least = MIN2(least, (HeapWord*)_base[i]); 251 } 252 return (oop)least; 253 } 254 255 // Exposed here to allow stack expansion in || case. 256 Mutex* par_lock() { return &_par_lock; } 257 }; 258 259 class CardTableRS; 260 class CMSParGCThreadState; 261 262 class ModUnionClosure: public MemRegionClosure { 263 protected: 264 CMSBitMap* _t; 265 public: 266 ModUnionClosure(CMSBitMap* t): _t(t) { } 267 void do_MemRegion(MemRegion mr); 268 }; 269 270 class ModUnionClosurePar: public ModUnionClosure { 271 public: 272 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 273 void do_MemRegion(MemRegion mr); 274 }; 275 276 // Survivor Chunk Array in support of parallelization of 277 // Survivor Space rescan. 278 class ChunkArray: public CHeapObj<mtGC> { 279 size_t _index; 280 size_t _capacity; 281 size_t _overflows; 282 HeapWord** _array; // storage for array 283 284 public: 285 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 286 ChunkArray(HeapWord** a, size_t c): 287 _index(0), _capacity(c), _overflows(0), _array(a) {} 288 289 HeapWord** array() { return _array; } 290 void set_array(HeapWord** a) { _array = a; } 291 292 size_t capacity() { return _capacity; } 293 void set_capacity(size_t c) { _capacity = c; } 294 295 size_t end() { 296 assert(_index <= capacity(), 297 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 298 _index, _capacity); 299 return _index; 300 } // exclusive 301 302 HeapWord* nth(size_t n) { 303 assert(n < end(), "Out of bounds access"); 304 return _array[n]; 305 } 306 307 void reset() { 308 _index = 0; 309 if (_overflows > 0) { 310 log_trace(gc)("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", _capacity, _overflows); 311 } 312 _overflows = 0; 313 } 314 315 void record_sample(HeapWord* p, size_t sz) { 316 // For now we do not do anything with the size 317 if (_index < _capacity) { 318 _array[_index++] = p; 319 } else { 320 ++_overflows; 321 assert(_index == _capacity, 322 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 323 "): out of bounds at overflow#" SIZE_FORMAT, 324 _index, _capacity, _overflows); 325 } 326 } 327 }; 328 329 // 330 // Timing, allocation and promotion statistics for gc scheduling and incremental 331 // mode pacing. Most statistics are exponential averages. 332 // 333 class CMSStats VALUE_OBJ_CLASS_SPEC { 334 private: 335 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 336 337 // The following are exponential averages with factor alpha: 338 // avg = (100 - alpha) * avg + alpha * cur_sample 339 // 340 // The durations measure: end_time[n] - start_time[n] 341 // The periods measure: start_time[n] - start_time[n-1] 342 // 343 // The cms period and duration include only concurrent collections; time spent 344 // in foreground cms collections due to System.gc() or because of a failure to 345 // keep up are not included. 346 // 347 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 348 // real value, but is used only after the first period. A value of 100 is 349 // used for the first sample so it gets the entire weight. 350 unsigned int _saved_alpha; // 0-100 351 unsigned int _gc0_alpha; 352 unsigned int _cms_alpha; 353 354 double _gc0_duration; 355 double _gc0_period; 356 size_t _gc0_promoted; // bytes promoted per gc0 357 double _cms_duration; 358 double _cms_duration_pre_sweep; // time from initiation to start of sweep 359 double _cms_period; 360 size_t _cms_allocated; // bytes of direct allocation per gc0 period 361 362 // Timers. 363 elapsedTimer _cms_timer; 364 TimeStamp _gc0_begin_time; 365 TimeStamp _cms_begin_time; 366 TimeStamp _cms_end_time; 367 368 // Snapshots of the amount used in the CMS generation. 369 size_t _cms_used_at_gc0_begin; 370 size_t _cms_used_at_gc0_end; 371 size_t _cms_used_at_cms_begin; 372 373 // Used to prevent the duty cycle from being reduced in the middle of a cms 374 // cycle. 375 bool _allow_duty_cycle_reduction; 376 377 enum { 378 _GC0_VALID = 0x1, 379 _CMS_VALID = 0x2, 380 _ALL_VALID = _GC0_VALID | _CMS_VALID 381 }; 382 383 unsigned int _valid_bits; 384 385 protected: 386 // In support of adjusting of cms trigger ratios based on history 387 // of concurrent mode failure. 388 double cms_free_adjustment_factor(size_t free) const; 389 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 390 391 public: 392 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 393 unsigned int alpha = CMSExpAvgFactor); 394 395 // Whether or not the statistics contain valid data; higher level statistics 396 // cannot be called until this returns true (they require at least one young 397 // gen and one cms cycle to have completed). 398 bool valid() const; 399 400 // Record statistics. 401 void record_gc0_begin(); 402 void record_gc0_end(size_t cms_gen_bytes_used); 403 void record_cms_begin(); 404 void record_cms_end(); 405 406 // Allow management of the cms timer, which must be stopped/started around 407 // yield points. 408 elapsedTimer& cms_timer() { return _cms_timer; } 409 void start_cms_timer() { _cms_timer.start(); } 410 void stop_cms_timer() { _cms_timer.stop(); } 411 412 // Basic statistics; units are seconds or bytes. 413 double gc0_period() const { return _gc0_period; } 414 double gc0_duration() const { return _gc0_duration; } 415 size_t gc0_promoted() const { return _gc0_promoted; } 416 double cms_period() const { return _cms_period; } 417 double cms_duration() const { return _cms_duration; } 418 size_t cms_allocated() const { return _cms_allocated; } 419 420 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 421 422 // Seconds since the last background cms cycle began or ended. 423 double cms_time_since_begin() const; 424 double cms_time_since_end() const; 425 426 // Higher level statistics--caller must check that valid() returns true before 427 // calling. 428 429 // Returns bytes promoted per second of wall clock time. 430 double promotion_rate() const; 431 432 // Returns bytes directly allocated per second of wall clock time. 433 double cms_allocation_rate() const; 434 435 // Rate at which space in the cms generation is being consumed (sum of the 436 // above two). 437 double cms_consumption_rate() const; 438 439 // Returns an estimate of the number of seconds until the cms generation will 440 // fill up, assuming no collection work is done. 441 double time_until_cms_gen_full() const; 442 443 // Returns an estimate of the number of seconds remaining until 444 // the cms generation collection should start. 445 double time_until_cms_start() const; 446 447 // End of higher level statistics. 448 449 // Debugging. 450 void print_on(outputStream* st) const PRODUCT_RETURN; 451 void print() const { print_on(tty); } 452 }; 453 454 // A closure related to weak references processing which 455 // we embed in the CMSCollector, since we need to pass 456 // it to the reference processor for secondary filtering 457 // of references based on reachability of referent; 458 // see role of _is_alive_non_header closure in the 459 // ReferenceProcessor class. 460 // For objects in the CMS generation, this closure checks 461 // if the object is "live" (reachable). Used in weak 462 // reference processing. 463 class CMSIsAliveClosure: public BoolObjectClosure { 464 const MemRegion _span; 465 const CMSBitMap* _bit_map; 466 467 friend class CMSCollector; 468 public: 469 CMSIsAliveClosure(MemRegion span, 470 CMSBitMap* bit_map): 471 _span(span), 472 _bit_map(bit_map) { 473 assert(!span.is_empty(), "Empty span could spell trouble"); 474 } 475 476 bool do_object_b(oop obj); 477 }; 478 479 480 // Implements AbstractRefProcTaskExecutor for CMS. 481 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 482 public: 483 484 CMSRefProcTaskExecutor(CMSCollector& collector) 485 : _collector(collector) 486 { } 487 488 // Executes a task using worker threads. 489 virtual void execute(ProcessTask& task); 490 virtual void execute(EnqueueTask& task); 491 private: 492 CMSCollector& _collector; 493 }; 494 495 496 class CMSCollector: public CHeapObj<mtGC> { 497 friend class VMStructs; 498 friend class ConcurrentMarkSweepThread; 499 friend class ConcurrentMarkSweepGeneration; 500 friend class CompactibleFreeListSpace; 501 friend class CMSParMarkTask; 502 friend class CMSParInitialMarkTask; 503 friend class CMSParRemarkTask; 504 friend class CMSConcMarkingTask; 505 friend class CMSRefProcTaskProxy; 506 friend class CMSRefProcTaskExecutor; 507 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 508 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 509 friend class PushOrMarkClosure; // to access _restart_addr 510 friend class ParPushOrMarkClosure; // to access _restart_addr 511 friend class MarkFromRootsClosure; // -- ditto -- 512 // ... and for clearing cards 513 friend class ParMarkFromRootsClosure; // to access _restart_addr 514 // ... and for clearing cards 515 friend class ParConcMarkingClosure; // to access _restart_addr etc. 516 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 517 friend class PushAndMarkVerifyClosure; // -- ditto -- 518 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 519 friend class PushAndMarkClosure; // -- ditto -- 520 friend class ParPushAndMarkClosure; // -- ditto -- 521 friend class CMSKeepAliveClosure; // -- ditto -- 522 friend class CMSDrainMarkingStackClosure; // -- ditto -- 523 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 524 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 525 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 526 friend class VM_CMS_Operation; 527 friend class VM_CMS_Initial_Mark; 528 friend class VM_CMS_Final_Remark; 529 friend class TraceCMSMemoryManagerStats; 530 531 private: 532 jlong _time_of_last_gc; 533 void update_time_of_last_gc(jlong now) { 534 _time_of_last_gc = now; 535 } 536 537 OopTaskQueueSet* _task_queues; 538 539 // Overflow list of grey objects, threaded through mark-word 540 // Manipulated with CAS in the parallel/multi-threaded case. 541 oopDesc* volatile _overflow_list; 542 // The following array-pair keeps track of mark words 543 // displaced for accommodating overflow list above. 544 // This code will likely be revisited under RFE#4922830. 545 Stack<oop, mtGC> _preserved_oop_stack; 546 Stack<markOop, mtGC> _preserved_mark_stack; 547 548 int* _hash_seed; 549 550 // In support of multi-threaded concurrent phases 551 YieldingFlexibleWorkGang* _conc_workers; 552 553 // Performance Counters 554 CollectorCounters* _gc_counters; 555 556 // Initialization Errors 557 bool _completed_initialization; 558 559 // In support of ExplicitGCInvokesConcurrent 560 static bool _full_gc_requested; 561 static GCCause::Cause _full_gc_cause; 562 unsigned int _collection_count_start; 563 564 // Should we unload classes this concurrent cycle? 565 bool _should_unload_classes; 566 unsigned int _concurrent_cycles_since_last_unload; 567 unsigned int concurrent_cycles_since_last_unload() const { 568 return _concurrent_cycles_since_last_unload; 569 } 570 // Did we (allow) unload classes in the previous concurrent cycle? 571 bool unloaded_classes_last_cycle() const { 572 return concurrent_cycles_since_last_unload() == 0; 573 } 574 // Root scanning options for perm gen 575 int _roots_scanning_options; 576 int roots_scanning_options() const { return _roots_scanning_options; } 577 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 578 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 579 580 // Verification support 581 CMSBitMap _verification_mark_bm; 582 void verify_after_remark_work_1(); 583 void verify_after_remark_work_2(); 584 585 // True if any verification flag is on. 586 bool _verifying; 587 bool verifying() const { return _verifying; } 588 void set_verifying(bool v) { _verifying = v; } 589 590 void set_did_compact(bool v); 591 592 // XXX Move these to CMSStats ??? FIX ME !!! 593 elapsedTimer _inter_sweep_timer; // Time between sweeps 594 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 595 // Padded decaying average estimates of the above 596 AdaptivePaddedAverage _inter_sweep_estimate; 597 AdaptivePaddedAverage _intra_sweep_estimate; 598 599 CMSTracer* _gc_tracer_cm; 600 ConcurrentGCTimer* _gc_timer_cm; 601 602 bool _cms_start_registered; 603 604 GCHeapSummary _last_heap_summary; 605 MetaspaceSummary _last_metaspace_summary; 606 607 void register_gc_start(GCCause::Cause cause); 608 void register_gc_end(); 609 void save_heap_summary(); 610 void report_heap_summary(GCWhen::Type when); 611 612 protected: 613 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 614 MemRegion _span; // Span covering above two 615 CardTableRS* _ct; // Card table 616 617 // CMS marking support structures 618 CMSBitMap _markBitMap; 619 CMSBitMap _modUnionTable; 620 CMSMarkStack _markStack; 621 622 HeapWord* _restart_addr; // In support of marking stack overflow 623 void lower_restart_addr(HeapWord* low); 624 625 // Counters in support of marking stack / work queue overflow handling: 626 // a non-zero value indicates certain types of overflow events during 627 // the current CMS cycle and could lead to stack resizing efforts at 628 // an opportune future time. 629 size_t _ser_pmc_preclean_ovflw; 630 size_t _ser_pmc_remark_ovflw; 631 size_t _par_pmc_remark_ovflw; 632 size_t _ser_kac_preclean_ovflw; 633 size_t _ser_kac_ovflw; 634 size_t _par_kac_ovflw; 635 NOT_PRODUCT(ssize_t _num_par_pushes;) 636 637 // ("Weak") Reference processing support. 638 ReferenceProcessor* _ref_processor; 639 CMSIsAliveClosure _is_alive_closure; 640 // Keep this textually after _markBitMap and _span; c'tor dependency. 641 642 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 643 ModUnionClosurePar _modUnionClosurePar; 644 645 // CMS abstract state machine 646 // initial_state: Idling 647 // next_state(Idling) = {Marking} 648 // next_state(Marking) = {Precleaning, Sweeping} 649 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 650 // next_state(AbortablePreclean) = {FinalMarking} 651 // next_state(FinalMarking) = {Sweeping} 652 // next_state(Sweeping) = {Resizing} 653 // next_state(Resizing) = {Resetting} 654 // next_state(Resetting) = {Idling} 655 // The numeric values below are chosen so that: 656 // . _collectorState <= Idling == post-sweep && pre-mark 657 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 658 // precleaning || abortablePrecleanb 659 public: 660 enum CollectorState { 661 Resizing = 0, 662 Resetting = 1, 663 Idling = 2, 664 InitialMarking = 3, 665 Marking = 4, 666 Precleaning = 5, 667 AbortablePreclean = 6, 668 FinalMarking = 7, 669 Sweeping = 8 670 }; 671 protected: 672 static CollectorState _collectorState; 673 674 // State related to prologue/epilogue invocation for my generations 675 bool _between_prologue_and_epilogue; 676 677 // Signaling/State related to coordination between fore- and background GC 678 // Note: When the baton has been passed from background GC to foreground GC, 679 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 680 static bool _foregroundGCIsActive; // true iff foreground collector is active or 681 // wants to go active 682 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 683 // yet passed the baton to the foreground GC 684 685 // Support for CMSScheduleRemark (abortable preclean) 686 bool _abort_preclean; 687 bool _start_sampling; 688 689 int _numYields; 690 size_t _numDirtyCards; 691 size_t _sweep_count; 692 693 // Occupancy used for bootstrapping stats 694 double _bootstrap_occupancy; 695 696 // Timer 697 elapsedTimer _timer; 698 699 // Timing, allocation and promotion statistics, used for scheduling. 700 CMSStats _stats; 701 702 enum CMS_op_type { 703 CMS_op_checkpointRootsInitial, 704 CMS_op_checkpointRootsFinal 705 }; 706 707 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 708 bool stop_world_and_do(CMS_op_type op); 709 710 OopTaskQueueSet* task_queues() { return _task_queues; } 711 int* hash_seed(int i) { return &_hash_seed[i]; } 712 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 713 714 // Support for parallelizing Eden rescan in CMS remark phase 715 void sample_eden(); // ... sample Eden space top 716 717 private: 718 // Support for parallelizing young gen rescan in CMS remark phase 719 ParNewGeneration* _young_gen; 720 721 HeapWord* volatile* _top_addr; // ... Top of Eden 722 HeapWord** _end_addr; // ... End of Eden 723 Mutex* _eden_chunk_lock; 724 HeapWord** _eden_chunk_array; // ... Eden partitioning array 725 size_t _eden_chunk_index; // ... top (exclusive) of array 726 size_t _eden_chunk_capacity; // ... max entries in array 727 728 // Support for parallelizing survivor space rescan 729 HeapWord** _survivor_chunk_array; 730 size_t _survivor_chunk_index; 731 size_t _survivor_chunk_capacity; 732 size_t* _cursor; 733 ChunkArray* _survivor_plab_array; 734 735 // Support for marking stack overflow handling 736 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 737 bool par_take_from_overflow_list(size_t num, 738 OopTaskQueue* to_work_q, 739 int no_of_gc_threads); 740 void push_on_overflow_list(oop p); 741 void par_push_on_overflow_list(oop p); 742 // The following is, obviously, not, in general, "MT-stable" 743 bool overflow_list_is_empty() const; 744 745 void preserve_mark_if_necessary(oop p); 746 void par_preserve_mark_if_necessary(oop p); 747 void preserve_mark_work(oop p, markOop m); 748 void restore_preserved_marks_if_any(); 749 NOT_PRODUCT(bool no_preserved_marks() const;) 750 // In support of testing overflow code 751 NOT_PRODUCT(int _overflow_counter;) 752 NOT_PRODUCT(bool simulate_overflow();) // Sequential 753 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 754 755 // CMS work methods 756 void checkpointRootsInitialWork(); // Initial checkpoint work 757 758 // A return value of false indicates failure due to stack overflow 759 bool markFromRootsWork(); // Concurrent marking work 760 761 public: // FIX ME!!! only for testing 762 bool do_marking_st(); // Single-threaded marking 763 bool do_marking_mt(); // Multi-threaded marking 764 765 private: 766 767 // Concurrent precleaning work 768 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen, 769 ScanMarkedObjectsAgainCarefullyClosure* cl); 770 size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen, 771 ScanMarkedObjectsAgainCarefullyClosure* cl); 772 // Does precleaning work, returning a quantity indicative of 773 // the amount of "useful work" done. 774 size_t preclean_work(bool clean_refs, bool clean_survivors); 775 void preclean_cld(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 776 void abortable_preclean(); // Preclean while looking for possible abort 777 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 778 // Helper function for above; merge-sorts the per-thread plab samples 779 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 780 // Resets (i.e. clears) the per-thread plab sample vectors 781 void reset_survivor_plab_arrays(); 782 783 // Final (second) checkpoint work 784 void checkpointRootsFinalWork(); 785 // Work routine for parallel version of remark 786 void do_remark_parallel(); 787 // Work routine for non-parallel version of remark 788 void do_remark_non_parallel(); 789 // Reference processing work routine (during second checkpoint) 790 void refProcessingWork(); 791 792 // Concurrent sweeping work 793 void sweepWork(ConcurrentMarkSweepGeneration* old_gen); 794 795 // Concurrent resetting of support data structures 796 void reset_concurrent(); 797 // Resetting of support data structures from a STW full GC 798 void reset_stw(); 799 800 // Clear _expansion_cause fields of constituent generations 801 void clear_expansion_cause(); 802 803 // An auxiliary method used to record the ends of 804 // used regions of each generation to limit the extent of sweep 805 void save_sweep_limits(); 806 807 // A work method used by the foreground collector to do 808 // a mark-sweep-compact. 809 void do_compaction_work(bool clear_all_soft_refs); 810 811 // Work methods for reporting concurrent mode interruption or failure 812 bool is_external_interruption(); 813 void report_concurrent_mode_interruption(); 814 815 // If the background GC is active, acquire control from the background 816 // GC and do the collection. 817 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 818 819 // For synchronizing passing of control from background to foreground 820 // GC. waitForForegroundGC() is called by the background 821 // collector. It if had to wait for a foreground collection, 822 // it returns true and the background collection should assume 823 // that the collection was finished by the foreground 824 // collector. 825 bool waitForForegroundGC(); 826 827 size_t block_size_using_printezis_bits(HeapWord* addr) const; 828 size_t block_size_if_printezis_bits(HeapWord* addr) const; 829 HeapWord* next_card_start_after_block(HeapWord* addr) const; 830 831 void setup_cms_unloading_and_verification_state(); 832 public: 833 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 834 CardTableRS* ct); 835 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 836 837 ReferenceProcessor* ref_processor() { return _ref_processor; } 838 void ref_processor_init(); 839 840 Mutex* bitMapLock() const { return _markBitMap.lock(); } 841 static CollectorState abstract_state() { return _collectorState; } 842 843 bool should_abort_preclean() const; // Whether preclean should be aborted. 844 size_t get_eden_used() const; 845 size_t get_eden_capacity() const; 846 847 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 848 849 // Locking checks 850 NOT_PRODUCT(static bool have_cms_token();) 851 852 bool shouldConcurrentCollect(); 853 854 void collect(bool full, 855 bool clear_all_soft_refs, 856 size_t size, 857 bool tlab); 858 void collect_in_background(GCCause::Cause cause); 859 860 // In support of ExplicitGCInvokesConcurrent 861 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 862 // Should we unload classes in a particular concurrent cycle? 863 bool should_unload_classes() const { 864 return _should_unload_classes; 865 } 866 void update_should_unload_classes(); 867 868 void direct_allocated(HeapWord* start, size_t size); 869 870 // Object is dead if not marked and current phase is sweeping. 871 bool is_dead_obj(oop obj) const; 872 873 // After a promotion (of "start"), do any necessary marking. 874 // If "par", then it's being done by a parallel GC thread. 875 // The last two args indicate if we need precise marking 876 // and if so the size of the object so it can be dirtied 877 // in its entirety. 878 void promoted(bool par, HeapWord* start, 879 bool is_obj_array, size_t obj_size); 880 881 void getFreelistLocks() const; 882 void releaseFreelistLocks() const; 883 bool haveFreelistLocks() const; 884 885 // Adjust size of underlying generation 886 void compute_new_size(); 887 888 // GC prologue and epilogue 889 void gc_prologue(bool full); 890 void gc_epilogue(bool full); 891 892 jlong time_of_last_gc(jlong now) { 893 if (_collectorState <= Idling) { 894 // gc not in progress 895 return _time_of_last_gc; 896 } else { 897 // collection in progress 898 return now; 899 } 900 } 901 902 // Support for parallel remark of survivor space 903 void* get_data_recorder(int thr_num); 904 void sample_eden_chunk(); 905 906 CMSBitMap* markBitMap() { return &_markBitMap; } 907 void directAllocated(HeapWord* start, size_t size); 908 909 // Main CMS steps and related support 910 void checkpointRootsInitial(); 911 bool markFromRoots(); // a return value of false indicates failure 912 // due to stack overflow 913 void preclean(); 914 void checkpointRootsFinal(); 915 void sweep(); 916 917 // Check that the currently executing thread is the expected 918 // one (foreground collector or background collector). 919 static void check_correct_thread_executing() PRODUCT_RETURN; 920 921 NOT_PRODUCT(bool is_cms_reachable(HeapWord* addr);) 922 923 // Performance Counter Support 924 CollectorCounters* counters() { return _gc_counters; } 925 926 // Timer stuff 927 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 928 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 929 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 930 jlong timerTicks() { assert(!_timer.is_active(), "Error"); return _timer.ticks(); } 931 932 int yields() { return _numYields; } 933 void resetYields() { _numYields = 0; } 934 void incrementYields() { _numYields++; } 935 void resetNumDirtyCards() { _numDirtyCards = 0; } 936 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 937 size_t numDirtyCards() { return _numDirtyCards; } 938 939 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 940 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 941 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 942 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 943 size_t sweep_count() const { return _sweep_count; } 944 void increment_sweep_count() { _sweep_count++; } 945 946 // Timers/stats for gc scheduling and incremental mode pacing. 947 CMSStats& stats() { return _stats; } 948 949 // Adaptive size policy 950 AdaptiveSizePolicy* size_policy(); 951 952 static void print_on_error(outputStream* st); 953 954 // Debugging 955 void verify(); 956 bool verify_after_remark(); 957 void verify_ok_to_terminate() const PRODUCT_RETURN; 958 void verify_work_stacks_empty() const PRODUCT_RETURN; 959 void verify_overflow_empty() const PRODUCT_RETURN; 960 961 // Convenience methods in support of debugging 962 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 963 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 964 965 // Accessors 966 CMSMarkStack* verification_mark_stack() { return &_markStack; } 967 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 968 969 // Initialization errors 970 bool completed_initialization() { return _completed_initialization; } 971 972 void print_eden_and_survivor_chunk_arrays(); 973 974 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 975 }; 976 977 class CMSExpansionCause : public AllStatic { 978 public: 979 enum Cause { 980 _no_expansion, 981 _satisfy_free_ratio, 982 _satisfy_promotion, 983 _satisfy_allocation, 984 _allocate_par_lab, 985 _allocate_par_spooling_space, 986 _adaptive_size_policy 987 }; 988 // Return a string describing the cause of the expansion. 989 static const char* to_string(CMSExpansionCause::Cause cause); 990 }; 991 992 class ConcurrentMarkSweepGeneration: public CardGeneration { 993 friend class VMStructs; 994 friend class ConcurrentMarkSweepThread; 995 friend class ConcurrentMarkSweep; 996 friend class CMSCollector; 997 protected: 998 static CMSCollector* _collector; // the collector that collects us 999 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1000 1001 // Performance Counters 1002 GenerationCounters* _gen_counters; 1003 GSpaceCounters* _space_counters; 1004 1005 // Words directly allocated, used by CMSStats. 1006 size_t _direct_allocated_words; 1007 1008 // Non-product stat counters 1009 NOT_PRODUCT( 1010 size_t _numObjectsPromoted; 1011 size_t _numWordsPromoted; 1012 size_t _numObjectsAllocated; 1013 size_t _numWordsAllocated; 1014 ) 1015 1016 // Used for sizing decisions 1017 bool _incremental_collection_failed; 1018 bool incremental_collection_failed() { 1019 return _incremental_collection_failed; 1020 } 1021 void set_incremental_collection_failed() { 1022 _incremental_collection_failed = true; 1023 } 1024 void clear_incremental_collection_failed() { 1025 _incremental_collection_failed = false; 1026 } 1027 1028 // accessors 1029 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1030 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1031 1032 // Accessing spaces 1033 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } 1034 1035 private: 1036 // For parallel young-gen GC support. 1037 CMSParGCThreadState** _par_gc_thread_states; 1038 1039 // Reason generation was expanded 1040 CMSExpansionCause::Cause _expansion_cause; 1041 1042 // In support of MinChunkSize being larger than min object size 1043 const double _dilatation_factor; 1044 1045 // True if a compacting collection was done. 1046 bool _did_compact; 1047 bool did_compact() { return _did_compact; } 1048 1049 // Fraction of current occupancy at which to start a CMS collection which 1050 // will collect this generation (at least). 1051 double _initiating_occupancy; 1052 1053 protected: 1054 // Shrink generation by specified size (returns false if unable to shrink) 1055 void shrink_free_list_by(size_t bytes); 1056 1057 // Update statistics for GC 1058 virtual void update_gc_stats(Generation* current_generation, bool full); 1059 1060 // Maximum available space in the generation (including uncommitted) 1061 // space. 1062 size_t max_available() const; 1063 1064 // getter and initializer for _initiating_occupancy field. 1065 double initiating_occupancy() const { return _initiating_occupancy; } 1066 void init_initiating_occupancy(intx io, uintx tr); 1067 1068 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1069 1070 void assert_correct_size_change_locking(); 1071 1072 public: 1073 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, size_t min_byte_size, size_t max_byte_size, CardTableRS* ct); 1074 1075 // Accessors 1076 CMSCollector* collector() const { return _collector; } 1077 static void set_collector(CMSCollector* collector) { 1078 assert(_collector == NULL, "already set"); 1079 _collector = collector; 1080 } 1081 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1082 1083 Mutex* freelistLock() const; 1084 1085 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1086 1087 void set_did_compact(bool v) { _did_compact = v; } 1088 1089 bool refs_discovery_is_atomic() const { return false; } 1090 bool refs_discovery_is_mt() const { 1091 // Note: CMS does MT-discovery during the parallel-remark 1092 // phases. Use ReferenceProcessorMTMutator to make refs 1093 // discovery MT-safe during such phases or other parallel 1094 // discovery phases in the future. This may all go away 1095 // if/when we decide that refs discovery is sufficiently 1096 // rare that the cost of the CAS's involved is in the 1097 // noise. That's a measurement that should be done, and 1098 // the code simplified if that turns out to be the case. 1099 return ConcGCThreads > 1; 1100 } 1101 1102 // Override 1103 virtual void ref_processor_init(); 1104 1105 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1106 1107 // Space enquiries 1108 double occupancy() const { return ((double)used())/((double)capacity()); } 1109 size_t contiguous_available() const; 1110 size_t unsafe_max_alloc_nogc() const; 1111 1112 // over-rides 1113 MemRegion used_region_at_save_marks() const; 1114 1115 // Adjust quantities in the generation affected by 1116 // the compaction. 1117 void reset_after_compaction(); 1118 1119 // Allocation support 1120 HeapWord* allocate(size_t size, bool tlab); 1121 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1122 oop promote(oop obj, size_t obj_size); 1123 HeapWord* par_allocate(size_t size, bool tlab) { 1124 return allocate(size, tlab); 1125 } 1126 1127 1128 // Used by CMSStats to track direct allocation. The value is sampled and 1129 // reset after each young gen collection. 1130 size_t direct_allocated_words() const { return _direct_allocated_words; } 1131 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1132 1133 // Overrides for parallel promotion. 1134 virtual oop par_promote(int thread_num, 1135 oop obj, markOop m, size_t word_sz); 1136 virtual void par_promote_alloc_done(int thread_num); 1137 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1138 1139 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1140 1141 // Inform this (old) generation that a promotion failure was 1142 // encountered during a collection of the young generation. 1143 virtual void promotion_failure_occurred(); 1144 1145 bool should_collect(bool full, size_t size, bool tlab); 1146 virtual bool should_concurrent_collect() const; 1147 virtual bool is_too_full() const; 1148 void collect(bool full, 1149 bool clear_all_soft_refs, 1150 size_t size, 1151 bool tlab); 1152 1153 HeapWord* expand_and_allocate(size_t word_size, 1154 bool tlab, 1155 bool parallel = false); 1156 1157 // GC prologue and epilogue 1158 void gc_prologue(bool full); 1159 void gc_prologue_work(bool full, bool registerClosure, 1160 ModUnionClosure* modUnionClosure); 1161 void gc_epilogue(bool full); 1162 void gc_epilogue_work(bool full); 1163 1164 // Time since last GC of this generation 1165 jlong time_of_last_gc(jlong now) { 1166 return collector()->time_of_last_gc(now); 1167 } 1168 void update_time_of_last_gc(jlong now) { 1169 collector()-> update_time_of_last_gc(now); 1170 } 1171 1172 // Allocation failure 1173 void shrink(size_t bytes); 1174 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1175 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1176 1177 // Iteration support and related enquiries 1178 void save_marks(); 1179 bool no_allocs_since_save_marks(); 1180 1181 // Iteration support specific to CMS generations 1182 void save_sweep_limit(); 1183 1184 // More iteration support 1185 virtual void oop_iterate(ExtendedOopClosure* cl); 1186 virtual void safe_object_iterate(ObjectClosure* cl); 1187 virtual void object_iterate(ObjectClosure* cl); 1188 1189 // Need to declare the full complement of closures, whether we'll 1190 // override them or not, or get message from the compiler: 1191 // oop_since_save_marks_iterate_nv hides virtual function... 1192 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1193 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1194 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1195 1196 // Smart allocation XXX -- move to CFLSpace? 1197 void setNearLargestChunk(); 1198 bool isNearLargestChunk(HeapWord* addr); 1199 1200 // Get the chunk at the end of the space. Delegates to 1201 // the space. 1202 FreeChunk* find_chunk_at_end(); 1203 1204 void post_compact(); 1205 1206 // Debugging 1207 void prepare_for_verify(); 1208 void verify(); 1209 void print_statistics() PRODUCT_RETURN; 1210 1211 // Performance Counters support 1212 virtual void update_counters(); 1213 virtual void update_counters(size_t used); 1214 void initialize_performance_counters(size_t min_byte_size, size_t max_byte_size); 1215 CollectorCounters* counters() { return collector()->counters(); } 1216 1217 // Support for parallel remark of survivor space 1218 void* get_data_recorder(int thr_num) { 1219 //Delegate to collector 1220 return collector()->get_data_recorder(thr_num); 1221 } 1222 void sample_eden_chunk() { 1223 //Delegate to collector 1224 return collector()->sample_eden_chunk(); 1225 } 1226 1227 // Printing 1228 const char* name() const; 1229 virtual const char* short_name() const { return "CMS"; } 1230 void print() const; 1231 1232 // Resize the generation after a compacting GC. The 1233 // generation can be treated as a contiguous space 1234 // after the compaction. 1235 virtual void compute_new_size(); 1236 // Resize the generation after a non-compacting 1237 // collection. 1238 void compute_new_size_free_list(); 1239 }; 1240 1241 // 1242 // Closures of various sorts used by CMS to accomplish its work 1243 // 1244 1245 // This closure is used to do concurrent marking from the roots 1246 // following the first checkpoint. 1247 class MarkFromRootsClosure: public BitMapClosure { 1248 CMSCollector* _collector; 1249 MemRegion _span; 1250 CMSBitMap* _bitMap; 1251 CMSBitMap* _mut; 1252 CMSMarkStack* _markStack; 1253 bool _yield; 1254 int _skipBits; 1255 HeapWord* _finger; 1256 HeapWord* _threshold; 1257 DEBUG_ONLY(bool _verifying;) 1258 1259 public: 1260 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1261 CMSBitMap* bitMap, 1262 CMSMarkStack* markStack, 1263 bool should_yield, bool verifying = false); 1264 bool do_bit(size_t offset); 1265 void reset(HeapWord* addr); 1266 inline void do_yield_check(); 1267 1268 private: 1269 void scanOopsInOop(HeapWord* ptr); 1270 void do_yield_work(); 1271 }; 1272 1273 // This closure is used to do concurrent multi-threaded 1274 // marking from the roots following the first checkpoint. 1275 // XXX This should really be a subclass of The serial version 1276 // above, but i have not had the time to refactor things cleanly. 1277 class ParMarkFromRootsClosure: public BitMapClosure { 1278 CMSCollector* _collector; 1279 MemRegion _whole_span; 1280 MemRegion _span; 1281 CMSBitMap* _bit_map; 1282 CMSBitMap* _mut; 1283 OopTaskQueue* _work_queue; 1284 CMSMarkStack* _overflow_stack; 1285 int _skip_bits; 1286 HeapWord* _finger; 1287 HeapWord* _threshold; 1288 CMSConcMarkingTask* _task; 1289 public: 1290 ParMarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1291 MemRegion span, 1292 CMSBitMap* bit_map, 1293 OopTaskQueue* work_queue, 1294 CMSMarkStack* overflow_stack); 1295 bool do_bit(size_t offset); 1296 inline void do_yield_check(); 1297 1298 private: 1299 void scan_oops_in_oop(HeapWord* ptr); 1300 void do_yield_work(); 1301 bool get_work_from_overflow_stack(); 1302 }; 1303 1304 // The following closures are used to do certain kinds of verification of 1305 // CMS marking. 1306 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1307 CMSCollector* _collector; 1308 MemRegion _span; 1309 CMSBitMap* _verification_bm; 1310 CMSBitMap* _cms_bm; 1311 CMSMarkStack* _mark_stack; 1312 protected: 1313 void do_oop(oop p); 1314 template <class T> inline void do_oop_work(T *p) { 1315 oop obj = oopDesc::load_decode_heap_oop(p); 1316 do_oop(obj); 1317 } 1318 public: 1319 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1320 MemRegion span, 1321 CMSBitMap* verification_bm, 1322 CMSBitMap* cms_bm, 1323 CMSMarkStack* mark_stack); 1324 void do_oop(oop* p); 1325 void do_oop(narrowOop* p); 1326 1327 // Deal with a stack overflow condition 1328 void handle_stack_overflow(HeapWord* lost); 1329 }; 1330 1331 class MarkFromRootsVerifyClosure: public BitMapClosure { 1332 CMSCollector* _collector; 1333 MemRegion _span; 1334 CMSBitMap* _verification_bm; 1335 CMSBitMap* _cms_bm; 1336 CMSMarkStack* _mark_stack; 1337 HeapWord* _finger; 1338 PushAndMarkVerifyClosure _pam_verify_closure; 1339 public: 1340 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1341 CMSBitMap* verification_bm, 1342 CMSBitMap* cms_bm, 1343 CMSMarkStack* mark_stack); 1344 bool do_bit(size_t offset); 1345 void reset(HeapWord* addr); 1346 }; 1347 1348 1349 // This closure is used to check that a certain set of bits is 1350 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1351 class FalseBitMapClosure: public BitMapClosure { 1352 public: 1353 bool do_bit(size_t offset) { 1354 guarantee(false, "Should not have a 1 bit"); 1355 return true; 1356 } 1357 }; 1358 1359 // A version of ObjectClosure with "memory" (see _previous_address below) 1360 class UpwardsObjectClosure: public BoolObjectClosure { 1361 HeapWord* _previous_address; 1362 public: 1363 UpwardsObjectClosure() : _previous_address(NULL) { } 1364 void set_previous(HeapWord* addr) { _previous_address = addr; } 1365 HeapWord* previous() { return _previous_address; } 1366 // A return value of "true" can be used by the caller to decide 1367 // if this object's end should *NOT* be recorded in 1368 // _previous_address above. 1369 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1370 }; 1371 1372 // This closure is used during the second checkpointing phase 1373 // to rescan the marked objects on the dirty cards in the mod 1374 // union table and the card table proper. It's invoked via 1375 // MarkFromDirtyCardsClosure below. It uses either 1376 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1377 // declared in genOopClosures.hpp to accomplish some of its work. 1378 // In the parallel case the bitMap is shared, so access to 1379 // it needs to be suitably synchronized for updates by embedded 1380 // closures that update it; however, this closure itself only 1381 // reads the bit_map and because it is idempotent, is immune to 1382 // reading stale values. 1383 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1384 #ifdef ASSERT 1385 CMSCollector* _collector; 1386 MemRegion _span; 1387 union { 1388 CMSMarkStack* _mark_stack; 1389 OopTaskQueue* _work_queue; 1390 }; 1391 #endif // ASSERT 1392 bool _parallel; 1393 CMSBitMap* _bit_map; 1394 union { 1395 MarkRefsIntoAndScanClosure* _scan_closure; 1396 ParMarkRefsIntoAndScanClosure* _par_scan_closure; 1397 }; 1398 1399 public: 1400 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1401 MemRegion span, 1402 ReferenceProcessor* rp, 1403 CMSBitMap* bit_map, 1404 CMSMarkStack* mark_stack, 1405 MarkRefsIntoAndScanClosure* cl): 1406 #ifdef ASSERT 1407 _collector(collector), 1408 _span(span), 1409 _mark_stack(mark_stack), 1410 #endif // ASSERT 1411 _parallel(false), 1412 _bit_map(bit_map), 1413 _scan_closure(cl) { } 1414 1415 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1416 MemRegion span, 1417 ReferenceProcessor* rp, 1418 CMSBitMap* bit_map, 1419 OopTaskQueue* work_queue, 1420 ParMarkRefsIntoAndScanClosure* cl): 1421 #ifdef ASSERT 1422 _collector(collector), 1423 _span(span), 1424 _work_queue(work_queue), 1425 #endif // ASSERT 1426 _parallel(true), 1427 _bit_map(bit_map), 1428 _par_scan_closure(cl) { } 1429 1430 bool do_object_b(oop obj) { 1431 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1432 return false; 1433 } 1434 bool do_object_bm(oop p, MemRegion mr); 1435 }; 1436 1437 // This closure is used during the second checkpointing phase 1438 // to rescan the marked objects on the dirty cards in the mod 1439 // union table and the card table proper. It invokes 1440 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1441 // In the parallel case, the bit map is shared and requires 1442 // synchronized access. 1443 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1444 CompactibleFreeListSpace* _space; 1445 ScanMarkedObjectsAgainClosure _scan_cl; 1446 size_t _num_dirty_cards; 1447 1448 public: 1449 MarkFromDirtyCardsClosure(CMSCollector* collector, 1450 MemRegion span, 1451 CompactibleFreeListSpace* space, 1452 CMSBitMap* bit_map, 1453 CMSMarkStack* mark_stack, 1454 MarkRefsIntoAndScanClosure* cl): 1455 _space(space), 1456 _num_dirty_cards(0), 1457 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1458 mark_stack, cl) { } 1459 1460 MarkFromDirtyCardsClosure(CMSCollector* collector, 1461 MemRegion span, 1462 CompactibleFreeListSpace* space, 1463 CMSBitMap* bit_map, 1464 OopTaskQueue* work_queue, 1465 ParMarkRefsIntoAndScanClosure* cl): 1466 _space(space), 1467 _num_dirty_cards(0), 1468 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1469 work_queue, cl) { } 1470 1471 void do_MemRegion(MemRegion mr); 1472 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1473 size_t num_dirty_cards() { return _num_dirty_cards; } 1474 }; 1475 1476 // This closure is used in the non-product build to check 1477 // that there are no MemRegions with a certain property. 1478 class FalseMemRegionClosure: public MemRegionClosure { 1479 void do_MemRegion(MemRegion mr) { 1480 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1481 guarantee(false, "Should never be here"); 1482 } 1483 }; 1484 1485 // This closure is used during the precleaning phase 1486 // to "carefully" rescan marked objects on dirty cards. 1487 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1488 // to accomplish some of its work. 1489 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1490 CMSCollector* _collector; 1491 MemRegion _span; 1492 bool _yield; 1493 Mutex* _freelistLock; 1494 CMSBitMap* _bitMap; 1495 CMSMarkStack* _markStack; 1496 MarkRefsIntoAndScanClosure* _scanningClosure; 1497 DEBUG_ONLY(HeapWord* _last_scanned_object;) 1498 1499 public: 1500 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1501 MemRegion span, 1502 CMSBitMap* bitMap, 1503 CMSMarkStack* markStack, 1504 MarkRefsIntoAndScanClosure* cl, 1505 bool should_yield): 1506 _collector(collector), 1507 _span(span), 1508 _yield(should_yield), 1509 _bitMap(bitMap), 1510 _markStack(markStack), 1511 _scanningClosure(cl) 1512 DEBUG_ONLY(COMMA _last_scanned_object(NULL)) 1513 { } 1514 1515 void do_object(oop p) { 1516 guarantee(false, "call do_object_careful instead"); 1517 } 1518 1519 size_t do_object_careful(oop p) { 1520 guarantee(false, "Unexpected caller"); 1521 return 0; 1522 } 1523 1524 size_t do_object_careful_m(oop p, MemRegion mr); 1525 1526 void setFreelistLock(Mutex* m) { 1527 _freelistLock = m; 1528 _scanningClosure->set_freelistLock(m); 1529 } 1530 1531 private: 1532 inline bool do_yield_check(); 1533 1534 void do_yield_work(); 1535 }; 1536 1537 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1538 CMSCollector* _collector; 1539 MemRegion _span; 1540 bool _yield; 1541 CMSBitMap* _bit_map; 1542 CMSMarkStack* _mark_stack; 1543 PushAndMarkClosure* _scanning_closure; 1544 unsigned int _before_count; 1545 1546 public: 1547 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1548 MemRegion span, 1549 CMSBitMap* bit_map, 1550 CMSMarkStack* mark_stack, 1551 PushAndMarkClosure* cl, 1552 unsigned int before_count, 1553 bool should_yield): 1554 _collector(collector), 1555 _span(span), 1556 _yield(should_yield), 1557 _bit_map(bit_map), 1558 _mark_stack(mark_stack), 1559 _scanning_closure(cl), 1560 _before_count(before_count) 1561 { } 1562 1563 void do_object(oop p) { 1564 guarantee(false, "call do_object_careful instead"); 1565 } 1566 1567 size_t do_object_careful(oop p); 1568 1569 size_t do_object_careful_m(oop p, MemRegion mr) { 1570 guarantee(false, "Unexpected caller"); 1571 return 0; 1572 } 1573 1574 private: 1575 inline void do_yield_check(); 1576 void do_yield_work(); 1577 }; 1578 1579 // This closure is used to accomplish the sweeping work 1580 // after the second checkpoint but before the concurrent reset 1581 // phase. 1582 // 1583 // Terminology 1584 // left hand chunk (LHC) - block of one or more chunks currently being 1585 // coalesced. The LHC is available for coalescing with a new chunk. 1586 // right hand chunk (RHC) - block that is currently being swept that is 1587 // free or garbage that can be coalesced with the LHC. 1588 // _inFreeRange is true if there is currently a LHC 1589 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1590 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1591 // _freeFinger is the address of the current LHC 1592 class SweepClosure: public BlkClosureCareful { 1593 CMSCollector* _collector; // collector doing the work 1594 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1595 CompactibleFreeListSpace* _sp; // Space being swept 1596 HeapWord* _limit;// the address at or above which the sweep should stop 1597 // because we do not expect newly garbage blocks 1598 // eligible for sweeping past that address. 1599 Mutex* _freelistLock; // Free list lock (in space) 1600 CMSBitMap* _bitMap; // Marking bit map (in 1601 // generation) 1602 bool _inFreeRange; // Indicates if we are in the 1603 // midst of a free run 1604 bool _freeRangeInFreeLists; 1605 // Often, we have just found 1606 // a free chunk and started 1607 // a new free range; we do not 1608 // eagerly remove this chunk from 1609 // the free lists unless there is 1610 // a possibility of coalescing. 1611 // When true, this flag indicates 1612 // that the _freeFinger below 1613 // points to a potentially free chunk 1614 // that may still be in the free lists 1615 bool _lastFreeRangeCoalesced; 1616 // free range contains chunks 1617 // coalesced 1618 bool _yield; 1619 // Whether sweeping should be 1620 // done with yields. For instance 1621 // when done by the foreground 1622 // collector we shouldn't yield. 1623 HeapWord* _freeFinger; // When _inFreeRange is set, the 1624 // pointer to the "left hand 1625 // chunk" 1626 size_t _freeRangeSize; 1627 // When _inFreeRange is set, this 1628 // indicates the accumulated size 1629 // of the "left hand chunk" 1630 NOT_PRODUCT( 1631 size_t _numObjectsFreed; 1632 size_t _numWordsFreed; 1633 size_t _numObjectsLive; 1634 size_t _numWordsLive; 1635 size_t _numObjectsAlreadyFree; 1636 size_t _numWordsAlreadyFree; 1637 FreeChunk* _last_fc; 1638 ) 1639 private: 1640 // Code that is common to a free chunk or garbage when 1641 // encountered during sweeping. 1642 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1643 // Process a free chunk during sweeping. 1644 void do_already_free_chunk(FreeChunk *fc); 1645 // Work method called when processing an already free or a 1646 // freshly garbage chunk to do a lookahead and possibly a 1647 // preemptive flush if crossing over _limit. 1648 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1649 // Process a garbage chunk during sweeping. 1650 size_t do_garbage_chunk(FreeChunk *fc); 1651 // Process a live chunk during sweeping. 1652 size_t do_live_chunk(FreeChunk* fc); 1653 1654 // Accessors. 1655 HeapWord* freeFinger() const { return _freeFinger; } 1656 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1657 bool inFreeRange() const { return _inFreeRange; } 1658 void set_inFreeRange(bool v) { _inFreeRange = v; } 1659 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1660 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1661 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1662 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1663 1664 // Initialize a free range. 1665 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1666 // Return this chunk to the free lists. 1667 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1668 1669 // Check if we should yield and do so when necessary. 1670 inline void do_yield_check(HeapWord* addr); 1671 1672 // Yield 1673 void do_yield_work(HeapWord* addr); 1674 1675 // Debugging/Printing 1676 void print_free_block_coalesced(FreeChunk* fc) const; 1677 1678 public: 1679 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1680 CMSBitMap* bitMap, bool should_yield); 1681 ~SweepClosure() PRODUCT_RETURN; 1682 1683 size_t do_blk_careful(HeapWord* addr); 1684 void print() const { print_on(tty); } 1685 void print_on(outputStream *st) const; 1686 }; 1687 1688 // Closures related to weak references processing 1689 1690 // During CMS' weak reference processing, this is a 1691 // work-routine/closure used to complete transitive 1692 // marking of objects as live after a certain point 1693 // in which an initial set has been completely accumulated. 1694 // This closure is currently used both during the final 1695 // remark stop-world phase, as well as during the concurrent 1696 // precleaning of the discovered reference lists. 1697 class CMSDrainMarkingStackClosure: public VoidClosure { 1698 CMSCollector* _collector; 1699 MemRegion _span; 1700 CMSMarkStack* _mark_stack; 1701 CMSBitMap* _bit_map; 1702 CMSKeepAliveClosure* _keep_alive; 1703 bool _concurrent_precleaning; 1704 public: 1705 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1706 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1707 CMSKeepAliveClosure* keep_alive, 1708 bool cpc): 1709 _collector(collector), 1710 _span(span), 1711 _bit_map(bit_map), 1712 _mark_stack(mark_stack), 1713 _keep_alive(keep_alive), 1714 _concurrent_precleaning(cpc) { 1715 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1716 "Mismatch"); 1717 } 1718 1719 void do_void(); 1720 }; 1721 1722 // A parallel version of CMSDrainMarkingStackClosure above. 1723 class CMSParDrainMarkingStackClosure: public VoidClosure { 1724 CMSCollector* _collector; 1725 MemRegion _span; 1726 OopTaskQueue* _work_queue; 1727 CMSBitMap* _bit_map; 1728 CMSInnerParMarkAndPushClosure _mark_and_push; 1729 1730 public: 1731 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1732 MemRegion span, CMSBitMap* bit_map, 1733 OopTaskQueue* work_queue): 1734 _collector(collector), 1735 _span(span), 1736 _bit_map(bit_map), 1737 _work_queue(work_queue), 1738 _mark_and_push(collector, span, bit_map, work_queue) { } 1739 1740 public: 1741 void trim_queue(uint max); 1742 void do_void(); 1743 }; 1744 1745 // Allow yielding or short-circuiting of reference list 1746 // precleaning work. 1747 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1748 CMSCollector* _collector; 1749 void do_yield_work(); 1750 public: 1751 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1752 _collector(collector) {} 1753 virtual bool should_return(); 1754 }; 1755 1756 1757 // Convenience class that locks free list locks for given CMS collector 1758 class FreelistLocker: public StackObj { 1759 private: 1760 CMSCollector* _collector; 1761 public: 1762 FreelistLocker(CMSCollector* collector): 1763 _collector(collector) { 1764 _collector->getFreelistLocks(); 1765 } 1766 1767 ~FreelistLocker() { 1768 _collector->releaseFreelistLocks(); 1769 } 1770 }; 1771 1772 // Mark all dead objects in a given space. 1773 class MarkDeadObjectsClosure: public BlkClosure { 1774 const CMSCollector* _collector; 1775 const CompactibleFreeListSpace* _sp; 1776 CMSBitMap* _live_bit_map; 1777 CMSBitMap* _dead_bit_map; 1778 public: 1779 MarkDeadObjectsClosure(const CMSCollector* collector, 1780 const CompactibleFreeListSpace* sp, 1781 CMSBitMap *live_bit_map, 1782 CMSBitMap *dead_bit_map) : 1783 _collector(collector), 1784 _sp(sp), 1785 _live_bit_map(live_bit_map), 1786 _dead_bit_map(dead_bit_map) {} 1787 size_t do_blk(HeapWord* addr); 1788 }; 1789 1790 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1791 1792 public: 1793 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1794 }; 1795 1796 1797 #endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP