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 ConcurrentMarkSweepPolicy; 66 class ConcurrentMarkSweepThread; 67 class CompactibleFreeListSpace; 68 class FreeChunk; 69 class ParNewGeneration; 70 class PromotionInfo; 71 class ScanMarkedObjectsAgainCarefullyClosure; 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 == CardTable::card_shift - LogHeapWordSize.) 80 // XXX 64-bit issues in BitMap? 81 class CMSBitMap { 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 { 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 CollectorCounters* _cgc_counters; 556 557 // Initialization Errors 558 bool _completed_initialization; 559 560 // In support of ExplicitGCInvokesConcurrent 561 static bool _full_gc_requested; 562 static GCCause::Cause _full_gc_cause; 563 unsigned int _collection_count_start; 564 565 // Should we unload classes this concurrent cycle? 566 bool _should_unload_classes; 567 unsigned int _concurrent_cycles_since_last_unload; 568 unsigned int concurrent_cycles_since_last_unload() const { 569 return _concurrent_cycles_since_last_unload; 570 } 571 // Did we (allow) unload classes in the previous concurrent cycle? 572 bool unloaded_classes_last_cycle() const { 573 return concurrent_cycles_since_last_unload() == 0; 574 } 575 // Root scanning options for perm gen 576 int _roots_scanning_options; 577 int roots_scanning_options() const { return _roots_scanning_options; } 578 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 579 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 580 581 // Verification support 582 CMSBitMap _verification_mark_bm; 583 void verify_after_remark_work_1(); 584 void verify_after_remark_work_2(); 585 586 // True if any verification flag is on. 587 bool _verifying; 588 bool verifying() const { return _verifying; } 589 void set_verifying(bool v) { _verifying = v; } 590 591 // Collector policy 592 ConcurrentMarkSweepPolicy* _collector_policy; 593 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 594 595 void set_did_compact(bool v); 596 597 // XXX Move these to CMSStats ??? FIX ME !!! 598 elapsedTimer _inter_sweep_timer; // Time between sweeps 599 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 600 // Padded decaying average estimates of the above 601 AdaptivePaddedAverage _inter_sweep_estimate; 602 AdaptivePaddedAverage _intra_sweep_estimate; 603 604 CMSTracer* _gc_tracer_cm; 605 ConcurrentGCTimer* _gc_timer_cm; 606 607 bool _cms_start_registered; 608 609 GCHeapSummary _last_heap_summary; 610 MetaspaceSummary _last_metaspace_summary; 611 612 void register_gc_start(GCCause::Cause cause); 613 void register_gc_end(); 614 void save_heap_summary(); 615 void report_heap_summary(GCWhen::Type when); 616 617 protected: 618 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 619 MemRegion _span; // Span covering above two 620 CardTableRS* _ct; // Card table 621 622 // CMS marking support structures 623 CMSBitMap _markBitMap; 624 CMSBitMap _modUnionTable; 625 CMSMarkStack _markStack; 626 627 HeapWord* _restart_addr; // In support of marking stack overflow 628 void lower_restart_addr(HeapWord* low); 629 630 // Counters in support of marking stack / work queue overflow handling: 631 // a non-zero value indicates certain types of overflow events during 632 // the current CMS cycle and could lead to stack resizing efforts at 633 // an opportune future time. 634 size_t _ser_pmc_preclean_ovflw; 635 size_t _ser_pmc_remark_ovflw; 636 size_t _par_pmc_remark_ovflw; 637 size_t _ser_kac_preclean_ovflw; 638 size_t _ser_kac_ovflw; 639 size_t _par_kac_ovflw; 640 NOT_PRODUCT(ssize_t _num_par_pushes;) 641 642 // ("Weak") Reference processing support. 643 ReferenceProcessor* _ref_processor; 644 CMSIsAliveClosure _is_alive_closure; 645 // Keep this textually after _markBitMap and _span; c'tor dependency. 646 647 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 648 ModUnionClosurePar _modUnionClosurePar; 649 650 // CMS abstract state machine 651 // initial_state: Idling 652 // next_state(Idling) = {Marking} 653 // next_state(Marking) = {Precleaning, Sweeping} 654 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 655 // next_state(AbortablePreclean) = {FinalMarking} 656 // next_state(FinalMarking) = {Sweeping} 657 // next_state(Sweeping) = {Resizing} 658 // next_state(Resizing) = {Resetting} 659 // next_state(Resetting) = {Idling} 660 // The numeric values below are chosen so that: 661 // . _collectorState <= Idling == post-sweep && pre-mark 662 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 663 // precleaning || abortablePrecleanb 664 public: 665 enum CollectorState { 666 Resizing = 0, 667 Resetting = 1, 668 Idling = 2, 669 InitialMarking = 3, 670 Marking = 4, 671 Precleaning = 5, 672 AbortablePreclean = 6, 673 FinalMarking = 7, 674 Sweeping = 8 675 }; 676 protected: 677 static CollectorState _collectorState; 678 679 // State related to prologue/epilogue invocation for my generations 680 bool _between_prologue_and_epilogue; 681 682 // Signaling/State related to coordination between fore- and background GC 683 // Note: When the baton has been passed from background GC to foreground GC, 684 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 685 static bool _foregroundGCIsActive; // true iff foreground collector is active or 686 // wants to go active 687 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 688 // yet passed the baton to the foreground GC 689 690 // Support for CMSScheduleRemark (abortable preclean) 691 bool _abort_preclean; 692 bool _start_sampling; 693 694 int _numYields; 695 size_t _numDirtyCards; 696 size_t _sweep_count; 697 698 // Occupancy used for bootstrapping stats 699 double _bootstrap_occupancy; 700 701 // Timer 702 elapsedTimer _timer; 703 704 // Timing, allocation and promotion statistics, used for scheduling. 705 CMSStats _stats; 706 707 enum CMS_op_type { 708 CMS_op_checkpointRootsInitial, 709 CMS_op_checkpointRootsFinal 710 }; 711 712 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 713 bool stop_world_and_do(CMS_op_type op); 714 715 OopTaskQueueSet* task_queues() { return _task_queues; } 716 int* hash_seed(int i) { return &_hash_seed[i]; } 717 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 718 719 // Support for parallelizing Eden rescan in CMS remark phase 720 void sample_eden(); // ... sample Eden space top 721 722 private: 723 // Support for parallelizing young gen rescan in CMS remark phase 724 ParNewGeneration* _young_gen; 725 726 HeapWord* volatile* _top_addr; // ... Top of Eden 727 HeapWord** _end_addr; // ... End of Eden 728 Mutex* _eden_chunk_lock; 729 HeapWord** _eden_chunk_array; // ... Eden partitioning array 730 size_t _eden_chunk_index; // ... top (exclusive) of array 731 size_t _eden_chunk_capacity; // ... max entries in array 732 733 // Support for parallelizing survivor space rescan 734 HeapWord** _survivor_chunk_array; 735 size_t _survivor_chunk_index; 736 size_t _survivor_chunk_capacity; 737 size_t* _cursor; 738 ChunkArray* _survivor_plab_array; 739 740 // Support for marking stack overflow handling 741 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 742 bool par_take_from_overflow_list(size_t num, 743 OopTaskQueue* to_work_q, 744 int no_of_gc_threads); 745 void push_on_overflow_list(oop p); 746 void par_push_on_overflow_list(oop p); 747 // The following is, obviously, not, in general, "MT-stable" 748 bool overflow_list_is_empty() const; 749 750 void preserve_mark_if_necessary(oop p); 751 void par_preserve_mark_if_necessary(oop p); 752 void preserve_mark_work(oop p, markOop m); 753 void restore_preserved_marks_if_any(); 754 NOT_PRODUCT(bool no_preserved_marks() const;) 755 // In support of testing overflow code 756 NOT_PRODUCT(int _overflow_counter;) 757 NOT_PRODUCT(bool simulate_overflow();) // Sequential 758 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 759 760 // CMS work methods 761 void checkpointRootsInitialWork(); // Initial checkpoint work 762 763 // A return value of false indicates failure due to stack overflow 764 bool markFromRootsWork(); // Concurrent marking work 765 766 public: // FIX ME!!! only for testing 767 bool do_marking_st(); // Single-threaded marking 768 bool do_marking_mt(); // Multi-threaded marking 769 770 private: 771 772 // Concurrent precleaning work 773 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen, 774 ScanMarkedObjectsAgainCarefullyClosure* cl); 775 size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen, 776 ScanMarkedObjectsAgainCarefullyClosure* cl); 777 // Does precleaning work, returning a quantity indicative of 778 // the amount of "useful work" done. 779 size_t preclean_work(bool clean_refs, bool clean_survivors); 780 void preclean_cld(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 781 void abortable_preclean(); // Preclean while looking for possible abort 782 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 783 // Helper function for above; merge-sorts the per-thread plab samples 784 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 785 // Resets (i.e. clears) the per-thread plab sample vectors 786 void reset_survivor_plab_arrays(); 787 788 // Final (second) checkpoint work 789 void checkpointRootsFinalWork(); 790 // Work routine for parallel version of remark 791 void do_remark_parallel(); 792 // Work routine for non-parallel version of remark 793 void do_remark_non_parallel(); 794 // Reference processing work routine (during second checkpoint) 795 void refProcessingWork(); 796 797 // Concurrent sweeping work 798 void sweepWork(ConcurrentMarkSweepGeneration* old_gen); 799 800 // Concurrent resetting of support data structures 801 void reset_concurrent(); 802 // Resetting of support data structures from a STW full GC 803 void reset_stw(); 804 805 // Clear _expansion_cause fields of constituent generations 806 void clear_expansion_cause(); 807 808 // An auxiliary method used to record the ends of 809 // used regions of each generation to limit the extent of sweep 810 void save_sweep_limits(); 811 812 // A work method used by the foreground collector to do 813 // a mark-sweep-compact. 814 void do_compaction_work(bool clear_all_soft_refs); 815 816 // Work methods for reporting concurrent mode interruption or failure 817 bool is_external_interruption(); 818 void report_concurrent_mode_interruption(); 819 820 // If the background GC is active, acquire control from the background 821 // GC and do the collection. 822 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 823 824 // For synchronizing passing of control from background to foreground 825 // GC. waitForForegroundGC() is called by the background 826 // collector. It if had to wait for a foreground collection, 827 // it returns true and the background collection should assume 828 // that the collection was finished by the foreground 829 // collector. 830 bool waitForForegroundGC(); 831 832 size_t block_size_using_printezis_bits(HeapWord* addr) const; 833 size_t block_size_if_printezis_bits(HeapWord* addr) const; 834 HeapWord* next_card_start_after_block(HeapWord* addr) const; 835 836 void setup_cms_unloading_and_verification_state(); 837 public: 838 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 839 CardTableRS* ct, 840 ConcurrentMarkSweepPolicy* cp); 841 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 842 843 ReferenceProcessor* ref_processor() { return _ref_processor; } 844 void ref_processor_init(); 845 846 Mutex* bitMapLock() const { return _markBitMap.lock(); } 847 static CollectorState abstract_state() { return _collectorState; } 848 849 bool should_abort_preclean() const; // Whether preclean should be aborted. 850 size_t get_eden_used() const; 851 size_t get_eden_capacity() const; 852 853 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 854 855 // Locking checks 856 NOT_PRODUCT(static bool have_cms_token();) 857 858 bool shouldConcurrentCollect(); 859 860 void collect(bool full, 861 bool clear_all_soft_refs, 862 size_t size, 863 bool tlab); 864 void collect_in_background(GCCause::Cause cause); 865 866 // In support of ExplicitGCInvokesConcurrent 867 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 868 // Should we unload classes in a particular concurrent cycle? 869 bool should_unload_classes() const { 870 return _should_unload_classes; 871 } 872 void update_should_unload_classes(); 873 874 void direct_allocated(HeapWord* start, size_t size); 875 876 // Object is dead if not marked and current phase is sweeping. 877 bool is_dead_obj(oop obj) const; 878 879 // After a promotion (of "start"), do any necessary marking. 880 // If "par", then it's being done by a parallel GC thread. 881 // The last two args indicate if we need precise marking 882 // and if so the size of the object so it can be dirtied 883 // in its entirety. 884 void promoted(bool par, HeapWord* start, 885 bool is_obj_array, size_t obj_size); 886 887 void getFreelistLocks() const; 888 void releaseFreelistLocks() const; 889 bool haveFreelistLocks() const; 890 891 // Adjust size of underlying generation 892 void compute_new_size(); 893 894 // GC prologue and epilogue 895 void gc_prologue(bool full); 896 void gc_epilogue(bool full); 897 898 jlong time_of_last_gc(jlong now) { 899 if (_collectorState <= Idling) { 900 // gc not in progress 901 return _time_of_last_gc; 902 } else { 903 // collection in progress 904 return now; 905 } 906 } 907 908 // Support for parallel remark of survivor space 909 void* get_data_recorder(int thr_num); 910 void sample_eden_chunk(); 911 912 CMSBitMap* markBitMap() { return &_markBitMap; } 913 void directAllocated(HeapWord* start, size_t size); 914 915 // Main CMS steps and related support 916 void checkpointRootsInitial(); 917 bool markFromRoots(); // a return value of false indicates failure 918 // due to stack overflow 919 void preclean(); 920 void checkpointRootsFinal(); 921 void sweep(); 922 923 // Check that the currently executing thread is the expected 924 // one (foreground collector or background collector). 925 static void check_correct_thread_executing() PRODUCT_RETURN; 926 927 NOT_PRODUCT(bool is_cms_reachable(HeapWord* addr);) 928 929 // Performance Counter Support 930 CollectorCounters* counters() { return _gc_counters; } 931 CollectorCounters* cgc_counters() { return _cgc_counters; } 932 933 // Timer stuff 934 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 935 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 936 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 937 jlong timerTicks() { assert(!_timer.is_active(), "Error"); return _timer.ticks(); } 938 939 int yields() { return _numYields; } 940 void resetYields() { _numYields = 0; } 941 void incrementYields() { _numYields++; } 942 void resetNumDirtyCards() { _numDirtyCards = 0; } 943 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 944 size_t numDirtyCards() { return _numDirtyCards; } 945 946 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 947 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 948 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 949 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 950 size_t sweep_count() const { return _sweep_count; } 951 void increment_sweep_count() { _sweep_count++; } 952 953 // Timers/stats for gc scheduling and incremental mode pacing. 954 CMSStats& stats() { return _stats; } 955 956 // Adaptive size policy 957 AdaptiveSizePolicy* size_policy(); 958 959 static void print_on_error(outputStream* st); 960 961 // Debugging 962 void verify(); 963 bool verify_after_remark(); 964 void verify_ok_to_terminate() const PRODUCT_RETURN; 965 void verify_work_stacks_empty() const PRODUCT_RETURN; 966 void verify_overflow_empty() const PRODUCT_RETURN; 967 968 // Convenience methods in support of debugging 969 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 970 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 971 972 // Accessors 973 CMSMarkStack* verification_mark_stack() { return &_markStack; } 974 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 975 976 // Initialization errors 977 bool completed_initialization() { return _completed_initialization; } 978 979 void print_eden_and_survivor_chunk_arrays(); 980 981 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 982 }; 983 984 class CMSExpansionCause : public AllStatic { 985 public: 986 enum Cause { 987 _no_expansion, 988 _satisfy_free_ratio, 989 _satisfy_promotion, 990 _satisfy_allocation, 991 _allocate_par_lab, 992 _allocate_par_spooling_space, 993 _adaptive_size_policy 994 }; 995 // Return a string describing the cause of the expansion. 996 static const char* to_string(CMSExpansionCause::Cause cause); 997 }; 998 999 class ConcurrentMarkSweepGeneration: public CardGeneration { 1000 friend class VMStructs; 1001 friend class ConcurrentMarkSweepThread; 1002 friend class ConcurrentMarkSweep; 1003 friend class CMSCollector; 1004 protected: 1005 static CMSCollector* _collector; // the collector that collects us 1006 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1007 1008 // Performance Counters 1009 GenerationCounters* _gen_counters; 1010 GSpaceCounters* _space_counters; 1011 1012 // Words directly allocated, used by CMSStats. 1013 size_t _direct_allocated_words; 1014 1015 // Non-product stat counters 1016 NOT_PRODUCT( 1017 size_t _numObjectsPromoted; 1018 size_t _numWordsPromoted; 1019 size_t _numObjectsAllocated; 1020 size_t _numWordsAllocated; 1021 ) 1022 1023 // Used for sizing decisions 1024 bool _incremental_collection_failed; 1025 bool incremental_collection_failed() { 1026 return _incremental_collection_failed; 1027 } 1028 void set_incremental_collection_failed() { 1029 _incremental_collection_failed = true; 1030 } 1031 void clear_incremental_collection_failed() { 1032 _incremental_collection_failed = false; 1033 } 1034 1035 // accessors 1036 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1037 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1038 1039 // Accessing spaces 1040 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } 1041 1042 private: 1043 // For parallel young-gen GC support. 1044 CMSParGCThreadState** _par_gc_thread_states; 1045 1046 // Reason generation was expanded 1047 CMSExpansionCause::Cause _expansion_cause; 1048 1049 // In support of MinChunkSize being larger than min object size 1050 const double _dilatation_factor; 1051 1052 // True if a compacting collection was done. 1053 bool _did_compact; 1054 bool did_compact() { return _did_compact; } 1055 1056 // Fraction of current occupancy at which to start a CMS collection which 1057 // will collect this generation (at least). 1058 double _initiating_occupancy; 1059 1060 protected: 1061 // Shrink generation by specified size (returns false if unable to shrink) 1062 void shrink_free_list_by(size_t bytes); 1063 1064 // Update statistics for GC 1065 virtual void update_gc_stats(Generation* current_generation, bool full); 1066 1067 // Maximum available space in the generation (including uncommitted) 1068 // space. 1069 size_t max_available() const; 1070 1071 // getter and initializer for _initiating_occupancy field. 1072 double initiating_occupancy() const { return _initiating_occupancy; } 1073 void init_initiating_occupancy(intx io, uintx tr); 1074 1075 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1076 1077 void assert_correct_size_change_locking(); 1078 1079 public: 1080 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, CardTableRS* ct); 1081 1082 // Accessors 1083 CMSCollector* collector() const { return _collector; } 1084 static void set_collector(CMSCollector* collector) { 1085 assert(_collector == NULL, "already set"); 1086 _collector = collector; 1087 } 1088 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1089 1090 Mutex* freelistLock() const; 1091 1092 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1093 1094 void set_did_compact(bool v) { _did_compact = v; } 1095 1096 bool refs_discovery_is_atomic() const { return false; } 1097 bool refs_discovery_is_mt() const { 1098 // Note: CMS does MT-discovery during the parallel-remark 1099 // phases. Use ReferenceProcessorMTMutator to make refs 1100 // discovery MT-safe during such phases or other parallel 1101 // discovery phases in the future. This may all go away 1102 // if/when we decide that refs discovery is sufficiently 1103 // rare that the cost of the CAS's involved is in the 1104 // noise. That's a measurement that should be done, and 1105 // the code simplified if that turns out to be the case. 1106 return ConcGCThreads > 1; 1107 } 1108 1109 // Override 1110 virtual void ref_processor_init(); 1111 1112 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1113 1114 // Space enquiries 1115 double occupancy() const { return ((double)used())/((double)capacity()); } 1116 size_t contiguous_available() const; 1117 size_t unsafe_max_alloc_nogc() const; 1118 1119 // over-rides 1120 MemRegion used_region_at_save_marks() const; 1121 1122 // Adjust quantities in the generation affected by 1123 // the compaction. 1124 void reset_after_compaction(); 1125 1126 // Allocation support 1127 HeapWord* allocate(size_t size, bool tlab); 1128 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1129 oop promote(oop obj, size_t obj_size); 1130 HeapWord* par_allocate(size_t size, bool tlab) { 1131 return allocate(size, tlab); 1132 } 1133 1134 1135 // Used by CMSStats to track direct allocation. The value is sampled and 1136 // reset after each young gen collection. 1137 size_t direct_allocated_words() const { return _direct_allocated_words; } 1138 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1139 1140 // Overrides for parallel promotion. 1141 virtual oop par_promote(int thread_num, 1142 oop obj, markOop m, size_t word_sz); 1143 virtual void par_promote_alloc_done(int thread_num); 1144 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1145 1146 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1147 1148 // Inform this (old) generation that a promotion failure was 1149 // encountered during a collection of the young generation. 1150 virtual void promotion_failure_occurred(); 1151 1152 bool should_collect(bool full, size_t size, bool tlab); 1153 virtual bool should_concurrent_collect() const; 1154 virtual bool is_too_full() const; 1155 void collect(bool full, 1156 bool clear_all_soft_refs, 1157 size_t size, 1158 bool tlab); 1159 1160 HeapWord* expand_and_allocate(size_t word_size, 1161 bool tlab, 1162 bool parallel = false); 1163 1164 // GC prologue and epilogue 1165 void gc_prologue(bool full); 1166 void gc_prologue_work(bool full, bool registerClosure, 1167 ModUnionClosure* modUnionClosure); 1168 void gc_epilogue(bool full); 1169 void gc_epilogue_work(bool full); 1170 1171 // Time since last GC of this generation 1172 jlong time_of_last_gc(jlong now) { 1173 return collector()->time_of_last_gc(now); 1174 } 1175 void update_time_of_last_gc(jlong now) { 1176 collector()-> update_time_of_last_gc(now); 1177 } 1178 1179 // Allocation failure 1180 void shrink(size_t bytes); 1181 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1182 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1183 1184 // Iteration support and related enquiries 1185 void save_marks(); 1186 bool no_allocs_since_save_marks(); 1187 1188 // Iteration support specific to CMS generations 1189 void save_sweep_limit(); 1190 1191 // More iteration support 1192 virtual void oop_iterate(ExtendedOopClosure* cl); 1193 virtual void safe_object_iterate(ObjectClosure* cl); 1194 virtual void object_iterate(ObjectClosure* cl); 1195 1196 // Need to declare the full complement of closures, whether we'll 1197 // override them or not, or get message from the compiler: 1198 // oop_since_save_marks_iterate_nv hides virtual function... 1199 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1200 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1201 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1202 1203 // Smart allocation XXX -- move to CFLSpace? 1204 void setNearLargestChunk(); 1205 bool isNearLargestChunk(HeapWord* addr); 1206 1207 // Get the chunk at the end of the space. Delegates to 1208 // the space. 1209 FreeChunk* find_chunk_at_end(); 1210 1211 void post_compact(); 1212 1213 // Debugging 1214 void prepare_for_verify(); 1215 void verify(); 1216 void print_statistics() PRODUCT_RETURN; 1217 1218 // Performance Counters support 1219 virtual void update_counters(); 1220 virtual void update_counters(size_t used); 1221 void initialize_performance_counters(); 1222 CollectorCounters* counters() { return collector()->counters(); } 1223 1224 // Support for parallel remark of survivor space 1225 void* get_data_recorder(int thr_num) { 1226 //Delegate to collector 1227 return collector()->get_data_recorder(thr_num); 1228 } 1229 void sample_eden_chunk() { 1230 //Delegate to collector 1231 return collector()->sample_eden_chunk(); 1232 } 1233 1234 // Printing 1235 const char* name() const; 1236 virtual const char* short_name() const { return "CMS"; } 1237 void print() const; 1238 1239 // Resize the generation after a compacting GC. The 1240 // generation can be treated as a contiguous space 1241 // after the compaction. 1242 virtual void compute_new_size(); 1243 // Resize the generation after a non-compacting 1244 // collection. 1245 void compute_new_size_free_list(); 1246 }; 1247 1248 // 1249 // Closures of various sorts used by CMS to accomplish its work 1250 // 1251 1252 // This closure is used to do concurrent marking from the roots 1253 // following the first checkpoint. 1254 class MarkFromRootsClosure: public BitMapClosure { 1255 CMSCollector* _collector; 1256 MemRegion _span; 1257 CMSBitMap* _bitMap; 1258 CMSBitMap* _mut; 1259 CMSMarkStack* _markStack; 1260 bool _yield; 1261 int _skipBits; 1262 HeapWord* _finger; 1263 HeapWord* _threshold; 1264 DEBUG_ONLY(bool _verifying;) 1265 1266 public: 1267 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1268 CMSBitMap* bitMap, 1269 CMSMarkStack* markStack, 1270 bool should_yield, bool verifying = false); 1271 bool do_bit(size_t offset); 1272 void reset(HeapWord* addr); 1273 inline void do_yield_check(); 1274 1275 private: 1276 void scanOopsInOop(HeapWord* ptr); 1277 void do_yield_work(); 1278 }; 1279 1280 // This closure is used to do concurrent multi-threaded 1281 // marking from the roots following the first checkpoint. 1282 // XXX This should really be a subclass of The serial version 1283 // above, but i have not had the time to refactor things cleanly. 1284 class ParMarkFromRootsClosure: public BitMapClosure { 1285 CMSCollector* _collector; 1286 MemRegion _whole_span; 1287 MemRegion _span; 1288 CMSBitMap* _bit_map; 1289 CMSBitMap* _mut; 1290 OopTaskQueue* _work_queue; 1291 CMSMarkStack* _overflow_stack; 1292 int _skip_bits; 1293 HeapWord* _finger; 1294 HeapWord* _threshold; 1295 CMSConcMarkingTask* _task; 1296 public: 1297 ParMarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1298 MemRegion span, 1299 CMSBitMap* bit_map, 1300 OopTaskQueue* work_queue, 1301 CMSMarkStack* overflow_stack); 1302 bool do_bit(size_t offset); 1303 inline void do_yield_check(); 1304 1305 private: 1306 void scan_oops_in_oop(HeapWord* ptr); 1307 void do_yield_work(); 1308 bool get_work_from_overflow_stack(); 1309 }; 1310 1311 // The following closures are used to do certain kinds of verification of 1312 // CMS marking. 1313 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1314 CMSCollector* _collector; 1315 MemRegion _span; 1316 CMSBitMap* _verification_bm; 1317 CMSBitMap* _cms_bm; 1318 CMSMarkStack* _mark_stack; 1319 protected: 1320 void do_oop(oop p); 1321 template <class T> void do_oop_work(T *p); 1322 1323 public: 1324 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1325 MemRegion span, 1326 CMSBitMap* verification_bm, 1327 CMSBitMap* cms_bm, 1328 CMSMarkStack* mark_stack); 1329 void do_oop(oop* p); 1330 void do_oop(narrowOop* p); 1331 1332 // Deal with a stack overflow condition 1333 void handle_stack_overflow(HeapWord* lost); 1334 }; 1335 1336 class MarkFromRootsVerifyClosure: public BitMapClosure { 1337 CMSCollector* _collector; 1338 MemRegion _span; 1339 CMSBitMap* _verification_bm; 1340 CMSBitMap* _cms_bm; 1341 CMSMarkStack* _mark_stack; 1342 HeapWord* _finger; 1343 PushAndMarkVerifyClosure _pam_verify_closure; 1344 public: 1345 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1346 CMSBitMap* verification_bm, 1347 CMSBitMap* cms_bm, 1348 CMSMarkStack* mark_stack); 1349 bool do_bit(size_t offset); 1350 void reset(HeapWord* addr); 1351 }; 1352 1353 1354 // This closure is used to check that a certain set of bits is 1355 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1356 class FalseBitMapClosure: public BitMapClosure { 1357 public: 1358 bool do_bit(size_t offset) { 1359 guarantee(false, "Should not have a 1 bit"); 1360 return true; 1361 } 1362 }; 1363 1364 // A version of ObjectClosure with "memory" (see _previous_address below) 1365 class UpwardsObjectClosure: public BoolObjectClosure { 1366 HeapWord* _previous_address; 1367 public: 1368 UpwardsObjectClosure() : _previous_address(NULL) { } 1369 void set_previous(HeapWord* addr) { _previous_address = addr; } 1370 HeapWord* previous() { return _previous_address; } 1371 // A return value of "true" can be used by the caller to decide 1372 // if this object's end should *NOT* be recorded in 1373 // _previous_address above. 1374 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1375 }; 1376 1377 // This closure is used during the second checkpointing phase 1378 // to rescan the marked objects on the dirty cards in the mod 1379 // union table and the card table proper. It's invoked via 1380 // MarkFromDirtyCardsClosure below. It uses either 1381 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1382 // declared in genOopClosures.hpp to accomplish some of its work. 1383 // In the parallel case the bitMap is shared, so access to 1384 // it needs to be suitably synchronized for updates by embedded 1385 // closures that update it; however, this closure itself only 1386 // reads the bit_map and because it is idempotent, is immune to 1387 // reading stale values. 1388 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1389 #ifdef ASSERT 1390 CMSCollector* _collector; 1391 MemRegion _span; 1392 union { 1393 CMSMarkStack* _mark_stack; 1394 OopTaskQueue* _work_queue; 1395 }; 1396 #endif // ASSERT 1397 bool _parallel; 1398 CMSBitMap* _bit_map; 1399 union { 1400 MarkRefsIntoAndScanClosure* _scan_closure; 1401 ParMarkRefsIntoAndScanClosure* _par_scan_closure; 1402 }; 1403 1404 public: 1405 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1406 MemRegion span, 1407 ReferenceProcessor* rp, 1408 CMSBitMap* bit_map, 1409 CMSMarkStack* mark_stack, 1410 MarkRefsIntoAndScanClosure* cl): 1411 #ifdef ASSERT 1412 _collector(collector), 1413 _span(span), 1414 _mark_stack(mark_stack), 1415 #endif // ASSERT 1416 _parallel(false), 1417 _bit_map(bit_map), 1418 _scan_closure(cl) { } 1419 1420 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1421 MemRegion span, 1422 ReferenceProcessor* rp, 1423 CMSBitMap* bit_map, 1424 OopTaskQueue* work_queue, 1425 ParMarkRefsIntoAndScanClosure* cl): 1426 #ifdef ASSERT 1427 _collector(collector), 1428 _span(span), 1429 _work_queue(work_queue), 1430 #endif // ASSERT 1431 _parallel(true), 1432 _bit_map(bit_map), 1433 _par_scan_closure(cl) { } 1434 1435 bool do_object_b(oop obj) { 1436 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1437 return false; 1438 } 1439 bool do_object_bm(oop p, MemRegion mr); 1440 }; 1441 1442 // This closure is used during the second checkpointing phase 1443 // to rescan the marked objects on the dirty cards in the mod 1444 // union table and the card table proper. It invokes 1445 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1446 // In the parallel case, the bit map is shared and requires 1447 // synchronized access. 1448 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1449 CompactibleFreeListSpace* _space; 1450 ScanMarkedObjectsAgainClosure _scan_cl; 1451 size_t _num_dirty_cards; 1452 1453 public: 1454 MarkFromDirtyCardsClosure(CMSCollector* collector, 1455 MemRegion span, 1456 CompactibleFreeListSpace* space, 1457 CMSBitMap* bit_map, 1458 CMSMarkStack* mark_stack, 1459 MarkRefsIntoAndScanClosure* cl): 1460 _space(space), 1461 _num_dirty_cards(0), 1462 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1463 mark_stack, cl) { } 1464 1465 MarkFromDirtyCardsClosure(CMSCollector* collector, 1466 MemRegion span, 1467 CompactibleFreeListSpace* space, 1468 CMSBitMap* bit_map, 1469 OopTaskQueue* work_queue, 1470 ParMarkRefsIntoAndScanClosure* cl): 1471 _space(space), 1472 _num_dirty_cards(0), 1473 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1474 work_queue, cl) { } 1475 1476 void do_MemRegion(MemRegion mr); 1477 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1478 size_t num_dirty_cards() { return _num_dirty_cards; } 1479 }; 1480 1481 // This closure is used in the non-product build to check 1482 // that there are no MemRegions with a certain property. 1483 class FalseMemRegionClosure: public MemRegionClosure { 1484 void do_MemRegion(MemRegion mr) { 1485 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1486 guarantee(false, "Should never be here"); 1487 } 1488 }; 1489 1490 // This closure is used during the precleaning phase 1491 // to "carefully" rescan marked objects on dirty cards. 1492 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1493 // to accomplish some of its work. 1494 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1495 CMSCollector* _collector; 1496 MemRegion _span; 1497 bool _yield; 1498 Mutex* _freelistLock; 1499 CMSBitMap* _bitMap; 1500 CMSMarkStack* _markStack; 1501 MarkRefsIntoAndScanClosure* _scanningClosure; 1502 DEBUG_ONLY(HeapWord* _last_scanned_object;) 1503 1504 public: 1505 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1506 MemRegion span, 1507 CMSBitMap* bitMap, 1508 CMSMarkStack* markStack, 1509 MarkRefsIntoAndScanClosure* cl, 1510 bool should_yield): 1511 _collector(collector), 1512 _span(span), 1513 _yield(should_yield), 1514 _bitMap(bitMap), 1515 _markStack(markStack), 1516 _scanningClosure(cl) 1517 DEBUG_ONLY(COMMA _last_scanned_object(NULL)) 1518 { } 1519 1520 void do_object(oop p) { 1521 guarantee(false, "call do_object_careful instead"); 1522 } 1523 1524 size_t do_object_careful(oop p) { 1525 guarantee(false, "Unexpected caller"); 1526 return 0; 1527 } 1528 1529 size_t do_object_careful_m(oop p, MemRegion mr); 1530 1531 void setFreelistLock(Mutex* m) { 1532 _freelistLock = m; 1533 _scanningClosure->set_freelistLock(m); 1534 } 1535 1536 private: 1537 inline bool do_yield_check(); 1538 1539 void do_yield_work(); 1540 }; 1541 1542 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1543 CMSCollector* _collector; 1544 MemRegion _span; 1545 bool _yield; 1546 CMSBitMap* _bit_map; 1547 CMSMarkStack* _mark_stack; 1548 PushAndMarkClosure* _scanning_closure; 1549 unsigned int _before_count; 1550 1551 public: 1552 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1553 MemRegion span, 1554 CMSBitMap* bit_map, 1555 CMSMarkStack* mark_stack, 1556 PushAndMarkClosure* cl, 1557 unsigned int before_count, 1558 bool should_yield): 1559 _collector(collector), 1560 _span(span), 1561 _yield(should_yield), 1562 _bit_map(bit_map), 1563 _mark_stack(mark_stack), 1564 _scanning_closure(cl), 1565 _before_count(before_count) 1566 { } 1567 1568 void do_object(oop p) { 1569 guarantee(false, "call do_object_careful instead"); 1570 } 1571 1572 size_t do_object_careful(oop p); 1573 1574 size_t do_object_careful_m(oop p, MemRegion mr) { 1575 guarantee(false, "Unexpected caller"); 1576 return 0; 1577 } 1578 1579 private: 1580 inline void do_yield_check(); 1581 void do_yield_work(); 1582 }; 1583 1584 // This closure is used to accomplish the sweeping work 1585 // after the second checkpoint but before the concurrent reset 1586 // phase. 1587 // 1588 // Terminology 1589 // left hand chunk (LHC) - block of one or more chunks currently being 1590 // coalesced. The LHC is available for coalescing with a new chunk. 1591 // right hand chunk (RHC) - block that is currently being swept that is 1592 // free or garbage that can be coalesced with the LHC. 1593 // _inFreeRange is true if there is currently a LHC 1594 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1595 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1596 // _freeFinger is the address of the current LHC 1597 class SweepClosure: public BlkClosureCareful { 1598 CMSCollector* _collector; // collector doing the work 1599 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1600 CompactibleFreeListSpace* _sp; // Space being swept 1601 HeapWord* _limit;// the address at or above which the sweep should stop 1602 // because we do not expect newly garbage blocks 1603 // eligible for sweeping past that address. 1604 Mutex* _freelistLock; // Free list lock (in space) 1605 CMSBitMap* _bitMap; // Marking bit map (in 1606 // generation) 1607 bool _inFreeRange; // Indicates if we are in the 1608 // midst of a free run 1609 bool _freeRangeInFreeLists; 1610 // Often, we have just found 1611 // a free chunk and started 1612 // a new free range; we do not 1613 // eagerly remove this chunk from 1614 // the free lists unless there is 1615 // a possibility of coalescing. 1616 // When true, this flag indicates 1617 // that the _freeFinger below 1618 // points to a potentially free chunk 1619 // that may still be in the free lists 1620 bool _lastFreeRangeCoalesced; 1621 // free range contains chunks 1622 // coalesced 1623 bool _yield; 1624 // Whether sweeping should be 1625 // done with yields. For instance 1626 // when done by the foreground 1627 // collector we shouldn't yield. 1628 HeapWord* _freeFinger; // When _inFreeRange is set, the 1629 // pointer to the "left hand 1630 // chunk" 1631 size_t _freeRangeSize; 1632 // When _inFreeRange is set, this 1633 // indicates the accumulated size 1634 // of the "left hand chunk" 1635 NOT_PRODUCT( 1636 size_t _numObjectsFreed; 1637 size_t _numWordsFreed; 1638 size_t _numObjectsLive; 1639 size_t _numWordsLive; 1640 size_t _numObjectsAlreadyFree; 1641 size_t _numWordsAlreadyFree; 1642 FreeChunk* _last_fc; 1643 ) 1644 private: 1645 // Code that is common to a free chunk or garbage when 1646 // encountered during sweeping. 1647 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1648 // Process a free chunk during sweeping. 1649 void do_already_free_chunk(FreeChunk *fc); 1650 // Work method called when processing an already free or a 1651 // freshly garbage chunk to do a lookahead and possibly a 1652 // preemptive flush if crossing over _limit. 1653 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1654 // Process a garbage chunk during sweeping. 1655 size_t do_garbage_chunk(FreeChunk *fc); 1656 // Process a live chunk during sweeping. 1657 size_t do_live_chunk(FreeChunk* fc); 1658 1659 // Accessors. 1660 HeapWord* freeFinger() const { return _freeFinger; } 1661 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1662 bool inFreeRange() const { return _inFreeRange; } 1663 void set_inFreeRange(bool v) { _inFreeRange = v; } 1664 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1665 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1666 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1667 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1668 1669 // Initialize a free range. 1670 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1671 // Return this chunk to the free lists. 1672 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1673 1674 // Check if we should yield and do so when necessary. 1675 inline void do_yield_check(HeapWord* addr); 1676 1677 // Yield 1678 void do_yield_work(HeapWord* addr); 1679 1680 // Debugging/Printing 1681 void print_free_block_coalesced(FreeChunk* fc) const; 1682 1683 public: 1684 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1685 CMSBitMap* bitMap, bool should_yield); 1686 ~SweepClosure() PRODUCT_RETURN; 1687 1688 size_t do_blk_careful(HeapWord* addr); 1689 void print() const { print_on(tty); } 1690 void print_on(outputStream *st) const; 1691 }; 1692 1693 // Closures related to weak references processing 1694 1695 // During CMS' weak reference processing, this is a 1696 // work-routine/closure used to complete transitive 1697 // marking of objects as live after a certain point 1698 // in which an initial set has been completely accumulated. 1699 // This closure is currently used both during the final 1700 // remark stop-world phase, as well as during the concurrent 1701 // precleaning of the discovered reference lists. 1702 class CMSDrainMarkingStackClosure: public VoidClosure { 1703 CMSCollector* _collector; 1704 MemRegion _span; 1705 CMSMarkStack* _mark_stack; 1706 CMSBitMap* _bit_map; 1707 CMSKeepAliveClosure* _keep_alive; 1708 bool _concurrent_precleaning; 1709 public: 1710 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1711 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1712 CMSKeepAliveClosure* keep_alive, 1713 bool cpc): 1714 _collector(collector), 1715 _span(span), 1716 _bit_map(bit_map), 1717 _mark_stack(mark_stack), 1718 _keep_alive(keep_alive), 1719 _concurrent_precleaning(cpc) { 1720 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1721 "Mismatch"); 1722 } 1723 1724 void do_void(); 1725 }; 1726 1727 // A parallel version of CMSDrainMarkingStackClosure above. 1728 class CMSParDrainMarkingStackClosure: public VoidClosure { 1729 CMSCollector* _collector; 1730 MemRegion _span; 1731 OopTaskQueue* _work_queue; 1732 CMSBitMap* _bit_map; 1733 CMSInnerParMarkAndPushClosure _mark_and_push; 1734 1735 public: 1736 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1737 MemRegion span, CMSBitMap* bit_map, 1738 OopTaskQueue* work_queue): 1739 _collector(collector), 1740 _span(span), 1741 _bit_map(bit_map), 1742 _work_queue(work_queue), 1743 _mark_and_push(collector, span, bit_map, work_queue) { } 1744 1745 public: 1746 void trim_queue(uint max); 1747 void do_void(); 1748 }; 1749 1750 // Allow yielding or short-circuiting of reference list 1751 // precleaning work. 1752 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1753 CMSCollector* _collector; 1754 void do_yield_work(); 1755 public: 1756 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1757 _collector(collector) {} 1758 virtual bool should_return(); 1759 }; 1760 1761 1762 // Convenience class that locks free list locks for given CMS collector 1763 class FreelistLocker: public StackObj { 1764 private: 1765 CMSCollector* _collector; 1766 public: 1767 FreelistLocker(CMSCollector* collector): 1768 _collector(collector) { 1769 _collector->getFreelistLocks(); 1770 } 1771 1772 ~FreelistLocker() { 1773 _collector->releaseFreelistLocks(); 1774 } 1775 }; 1776 1777 // Mark all dead objects in a given space. 1778 class MarkDeadObjectsClosure: public BlkClosure { 1779 const CMSCollector* _collector; 1780 const CompactibleFreeListSpace* _sp; 1781 CMSBitMap* _live_bit_map; 1782 CMSBitMap* _dead_bit_map; 1783 public: 1784 MarkDeadObjectsClosure(const CMSCollector* collector, 1785 const CompactibleFreeListSpace* sp, 1786 CMSBitMap *live_bit_map, 1787 CMSBitMap *dead_bit_map) : 1788 _collector(collector), 1789 _sp(sp), 1790 _live_bit_map(live_bit_map), 1791 _dead_bit_map(dead_bit_map) {} 1792 size_t do_blk(HeapWord* addr); 1793 }; 1794 1795 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1796 1797 public: 1798 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1799 }; 1800 1801 1802 #endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP