1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_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/freeBlockDictionary.hpp" 40 #include "memory/iterator.hpp" 41 #include "memory/virtualspace.hpp" 42 #include "runtime/mutexLocker.hpp" 43 #include "services/memoryService.hpp" 44 #include "utilities/bitMap.hpp" 45 #include "utilities/stack.hpp" 46 47 // ConcurrentMarkSweepGeneration is in support of a concurrent 48 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker 49 // style. We assume, for now, that this generation is always the 50 // seniormost generation and for simplicity 51 // in the first implementation, that this generation is a single compactible 52 // space. Neither of these restrictions appears essential, and will be 53 // relaxed in the future when more time is available to implement the 54 // greater generality (and there's a need for it). 55 // 56 // Concurrent mode failures are currently handled by 57 // means of a sliding mark-compact. 58 59 class AdaptiveSizePolicy; 60 class CMSCollector; 61 class CMSConcMarkingTask; 62 class CMSGCAdaptivePolicyCounters; 63 class CMSTracer; 64 class ConcurrentGCTimer; 65 class ConcurrentMarkSweepGeneration; 66 class ConcurrentMarkSweepPolicy; 67 class ConcurrentMarkSweepThread; 68 class CompactibleFreeListSpace; 69 class FreeChunk; 70 class ParNewGeneration; 71 class PromotionInfo; 72 class ScanMarkedObjectsAgainCarefullyClosure; 73 class TenuredGeneration; 74 class SerialOldTracer; 75 76 // A generic CMS bit map. It's the basis for both the CMS marking bit map 77 // as well as for the mod union table (in each case only a subset of the 78 // methods are used). This is essentially a wrapper around the BitMap class, 79 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 80 // we have _shifter == 0. and for the mod union table we have 81 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 82 // XXX 64-bit issues in BitMap? 83 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 84 friend class VMStructs; 85 86 HeapWord* _bmStartWord; // base address of range covered by map 87 size_t _bmWordSize; // map size (in #HeapWords covered) 88 const int _shifter; // shifts to convert HeapWord to bit position 89 VirtualSpace _virtual_space; // underlying the bit map 90 BitMap _bm; // the bit map itself 91 public: 92 Mutex* const _lock; // mutex protecting _bm; 93 94 public: 95 // constructor 96 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 97 98 // allocates the actual storage for the map 99 bool allocate(MemRegion mr); 100 // field getter 101 Mutex* lock() const { return _lock; } 102 // locking verifier convenience function 103 void assert_locked() const PRODUCT_RETURN; 104 105 // inquiries 106 HeapWord* startWord() const { return _bmStartWord; } 107 size_t sizeInWords() const { return _bmWordSize; } 108 size_t sizeInBits() const { return _bm.size(); } 109 // the following is one past the last word in space 110 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 111 112 // reading marks 113 bool isMarked(HeapWord* addr) const; 114 bool par_isMarked(HeapWord* addr) const; // do not lock checks 115 bool isUnmarked(HeapWord* addr) const; 116 bool isAllClear() const; 117 118 // writing marks 119 void mark(HeapWord* addr); 120 // For marking by parallel GC threads; 121 // returns true if we did, false if another thread did 122 bool par_mark(HeapWord* addr); 123 124 void mark_range(MemRegion mr); 125 void par_mark_range(MemRegion mr); 126 void mark_large_range(MemRegion mr); 127 void par_mark_large_range(MemRegion mr); 128 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 129 void clear_range(MemRegion mr); 130 void par_clear_range(MemRegion mr); 131 void clear_large_range(MemRegion mr); 132 void par_clear_large_range(MemRegion mr); 133 void clear_all(); 134 void clear_all_incrementally(); // Not yet implemented!! 135 136 NOT_PRODUCT( 137 // checks the memory region for validity 138 void region_invariant(MemRegion mr); 139 ) 140 141 // iteration 142 void iterate(BitMapClosure* cl) { 143 _bm.iterate(cl); 144 } 145 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 146 void dirty_range_iterate_clear(MemRegionClosure* cl); 147 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 148 149 // auxiliary support for iteration 150 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 151 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 152 HeapWord* end_addr) const; 153 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 154 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 155 HeapWord* end_addr) const; 156 MemRegion getAndClearMarkedRegion(HeapWord* addr); 157 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 158 HeapWord* end_addr); 159 160 // conversion utilities 161 HeapWord* offsetToHeapWord(size_t offset) const; 162 size_t heapWordToOffset(HeapWord* addr) const; 163 size_t heapWordDiffToOffsetDiff(size_t diff) const; 164 165 void print_on_error(outputStream* st, const char* prefix) const; 166 167 // debugging 168 // is this address range covered by the bit-map? 169 NOT_PRODUCT( 170 bool covers(MemRegion mr) const; 171 bool covers(HeapWord* start, size_t size = 0) const; 172 ) 173 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 174 }; 175 176 // Represents a marking stack used by the CMS collector. 177 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 178 class CMSMarkStack: public CHeapObj<mtGC> { 179 friend class CMSCollector; // To get at expansion stats further below. 180 181 VirtualSpace _virtual_space; // Space for the stack 182 oop* _base; // Bottom of stack 183 size_t _index; // One more than last occupied index 184 size_t _capacity; // Max #elements 185 Mutex _par_lock; // An advisory lock used in case of parallel access 186 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run 187 188 protected: 189 size_t _hit_limit; // We hit max stack size limit 190 size_t _failed_double; // We failed expansion before hitting limit 191 192 public: 193 CMSMarkStack(): 194 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true, 195 Monitor::_safepoint_check_never), 196 _hit_limit(0), 197 _failed_double(0) {} 198 199 bool allocate(size_t size); 200 201 size_t capacity() const { return _capacity; } 202 203 oop pop() { 204 if (!isEmpty()) { 205 return _base[--_index] ; 206 } 207 return NULL; 208 } 209 210 bool push(oop ptr) { 211 if (isFull()) { 212 return false; 213 } else { 214 _base[_index++] = ptr; 215 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 216 return true; 217 } 218 } 219 220 bool isEmpty() const { return _index == 0; } 221 bool isFull() const { 222 assert(_index <= _capacity, "buffer overflow"); 223 return _index == _capacity; 224 } 225 226 size_t length() { return _index; } 227 228 // "Parallel versions" of some of the above 229 oop par_pop() { 230 // lock and pop 231 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 232 return pop(); 233 } 234 235 bool par_push(oop ptr) { 236 // lock and push 237 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 238 return push(ptr); 239 } 240 241 // Forcibly reset the stack, losing all of its contents. 242 void reset() { 243 _index = 0; 244 } 245 246 // Expand the stack, typically in response to an overflow condition. 247 void expand(); 248 249 // Compute the least valued stack element. 250 oop least_value(HeapWord* low) { 251 oop least = (oop)low; 252 for (size_t i = 0; i < _index; i++) { 253 least = MIN2(least, _base[i]); 254 } 255 return least; 256 } 257 258 // Exposed here to allow stack expansion in || case. 259 Mutex* par_lock() { return &_par_lock; } 260 }; 261 262 class CardTableRS; 263 class CMSParGCThreadState; 264 265 class ModUnionClosure: public MemRegionClosure { 266 protected: 267 CMSBitMap* _t; 268 public: 269 ModUnionClosure(CMSBitMap* t): _t(t) { } 270 void do_MemRegion(MemRegion mr); 271 }; 272 273 class ModUnionClosurePar: public ModUnionClosure { 274 public: 275 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 276 void do_MemRegion(MemRegion mr); 277 }; 278 279 // Survivor Chunk Array in support of parallelization of 280 // Survivor Space rescan. 281 class ChunkArray: public CHeapObj<mtGC> { 282 size_t _index; 283 size_t _capacity; 284 size_t _overflows; 285 HeapWord** _array; // storage for array 286 287 public: 288 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 289 ChunkArray(HeapWord** a, size_t c): 290 _index(0), _capacity(c), _overflows(0), _array(a) {} 291 292 HeapWord** array() { return _array; } 293 void set_array(HeapWord** a) { _array = a; } 294 295 size_t capacity() { return _capacity; } 296 void set_capacity(size_t c) { _capacity = c; } 297 298 size_t end() { 299 assert(_index <= capacity(), 300 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 301 _index, _capacity); 302 return _index; 303 } // exclusive 304 305 HeapWord* nth(size_t n) { 306 assert(n < end(), "Out of bounds access"); 307 return _array[n]; 308 } 309 310 void reset() { 311 _index = 0; 312 if (_overflows > 0) { 313 log_trace(gc)("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", _capacity, _overflows); 314 } 315 _overflows = 0; 316 } 317 318 void record_sample(HeapWord* p, size_t sz) { 319 // For now we do not do anything with the size 320 if (_index < _capacity) { 321 _array[_index++] = p; 322 } else { 323 ++_overflows; 324 assert(_index == _capacity, 325 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 326 "): out of bounds at overflow#" SIZE_FORMAT, 327 _index, _capacity, _overflows); 328 } 329 } 330 }; 331 332 // 333 // Timing, allocation and promotion statistics for gc scheduling and incremental 334 // mode pacing. Most statistics are exponential averages. 335 // 336 class CMSStats VALUE_OBJ_CLASS_SPEC { 337 private: 338 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 339 340 // The following are exponential averages with factor alpha: 341 // avg = (100 - alpha) * avg + alpha * cur_sample 342 // 343 // The durations measure: end_time[n] - start_time[n] 344 // The periods measure: start_time[n] - start_time[n-1] 345 // 346 // The cms period and duration include only concurrent collections; time spent 347 // in foreground cms collections due to System.gc() or because of a failure to 348 // keep up are not included. 349 // 350 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 351 // real value, but is used only after the first period. A value of 100 is 352 // used for the first sample so it gets the entire weight. 353 unsigned int _saved_alpha; // 0-100 354 unsigned int _gc0_alpha; 355 unsigned int _cms_alpha; 356 357 double _gc0_duration; 358 double _gc0_period; 359 size_t _gc0_promoted; // bytes promoted per gc0 360 double _cms_duration; 361 double _cms_duration_pre_sweep; // time from initiation to start of sweep 362 double _cms_period; 363 size_t _cms_allocated; // bytes of direct allocation per gc0 period 364 365 // Timers. 366 elapsedTimer _cms_timer; 367 TimeStamp _gc0_begin_time; 368 TimeStamp _cms_begin_time; 369 TimeStamp _cms_end_time; 370 371 // Snapshots of the amount used in the CMS generation. 372 size_t _cms_used_at_gc0_begin; 373 size_t _cms_used_at_gc0_end; 374 size_t _cms_used_at_cms_begin; 375 376 // Used to prevent the duty cycle from being reduced in the middle of a cms 377 // cycle. 378 bool _allow_duty_cycle_reduction; 379 380 enum { 381 _GC0_VALID = 0x1, 382 _CMS_VALID = 0x2, 383 _ALL_VALID = _GC0_VALID | _CMS_VALID 384 }; 385 386 unsigned int _valid_bits; 387 388 protected: 389 // In support of adjusting of cms trigger ratios based on history 390 // of concurrent mode failure. 391 double cms_free_adjustment_factor(size_t free) const; 392 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 393 394 public: 395 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 396 unsigned int alpha = CMSExpAvgFactor); 397 398 // Whether or not the statistics contain valid data; higher level statistics 399 // cannot be called until this returns true (they require at least one young 400 // gen and one cms cycle to have completed). 401 bool valid() const; 402 403 // Record statistics. 404 void record_gc0_begin(); 405 void record_gc0_end(size_t cms_gen_bytes_used); 406 void record_cms_begin(); 407 void record_cms_end(); 408 409 // Allow management of the cms timer, which must be stopped/started around 410 // yield points. 411 elapsedTimer& cms_timer() { return _cms_timer; } 412 void start_cms_timer() { _cms_timer.start(); } 413 void stop_cms_timer() { _cms_timer.stop(); } 414 415 // Basic statistics; units are seconds or bytes. 416 double gc0_period() const { return _gc0_period; } 417 double gc0_duration() const { return _gc0_duration; } 418 size_t gc0_promoted() const { return _gc0_promoted; } 419 double cms_period() const { return _cms_period; } 420 double cms_duration() const { return _cms_duration; } 421 size_t cms_allocated() const { return _cms_allocated; } 422 423 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 424 425 // Seconds since the last background cms cycle began or ended. 426 double cms_time_since_begin() const; 427 double cms_time_since_end() const; 428 429 // Higher level statistics--caller must check that valid() returns true before 430 // calling. 431 432 // Returns bytes promoted per second of wall clock time. 433 double promotion_rate() const; 434 435 // Returns bytes directly allocated per second of wall clock time. 436 double cms_allocation_rate() const; 437 438 // Rate at which space in the cms generation is being consumed (sum of the 439 // above two). 440 double cms_consumption_rate() const; 441 442 // Returns an estimate of the number of seconds until the cms generation will 443 // fill up, assuming no collection work is done. 444 double time_until_cms_gen_full() const; 445 446 // Returns an estimate of the number of seconds remaining until 447 // the cms generation collection should start. 448 double time_until_cms_start() const; 449 450 // End of higher level statistics. 451 452 // Debugging. 453 void print_on(outputStream* st) const PRODUCT_RETURN; 454 void print() const { print_on(tty); } 455 }; 456 457 // A closure related to weak references processing which 458 // we embed in the CMSCollector, since we need to pass 459 // it to the reference processor for secondary filtering 460 // of references based on reachability of referent; 461 // see role of _is_alive_non_header closure in the 462 // ReferenceProcessor class. 463 // For objects in the CMS generation, this closure checks 464 // if the object is "live" (reachable). Used in weak 465 // reference processing. 466 class CMSIsAliveClosure: public BoolObjectClosure { 467 const MemRegion _span; 468 const CMSBitMap* _bit_map; 469 470 friend class CMSCollector; 471 public: 472 CMSIsAliveClosure(MemRegion span, 473 CMSBitMap* bit_map): 474 _span(span), 475 _bit_map(bit_map) { 476 assert(!span.is_empty(), "Empty span could spell trouble"); 477 } 478 479 bool do_object_b(oop obj); 480 }; 481 482 483 // Implements AbstractRefProcTaskExecutor for CMS. 484 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 485 public: 486 487 CMSRefProcTaskExecutor(CMSCollector& collector) 488 : _collector(collector) 489 { } 490 491 // Executes a task using worker threads. 492 virtual void execute(ProcessTask& task); 493 virtual void execute(EnqueueTask& task); 494 private: 495 CMSCollector& _collector; 496 }; 497 498 499 class CMSCollector: public CHeapObj<mtGC> { 500 friend class VMStructs; 501 friend class ConcurrentMarkSweepThread; 502 friend class ConcurrentMarkSweepGeneration; 503 friend class CompactibleFreeListSpace; 504 friend class CMSParMarkTask; 505 friend class CMSParInitialMarkTask; 506 friend class CMSParRemarkTask; 507 friend class CMSConcMarkingTask; 508 friend class CMSRefProcTaskProxy; 509 friend class CMSRefProcTaskExecutor; 510 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 511 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 512 friend class PushOrMarkClosure; // to access _restart_addr 513 friend class Par_PushOrMarkClosure; // to access _restart_addr 514 friend class MarkFromRootsClosure; // -- ditto -- 515 // ... and for clearing cards 516 friend class Par_MarkFromRootsClosure; // to access _restart_addr 517 // ... and for clearing cards 518 friend class Par_ConcMarkingClosure; // to access _restart_addr etc. 519 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 520 friend class PushAndMarkVerifyClosure; // -- ditto -- 521 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 522 friend class PushAndMarkClosure; // -- ditto -- 523 friend class Par_PushAndMarkClosure; // -- ditto -- 524 friend class CMSKeepAliveClosure; // -- ditto -- 525 friend class CMSDrainMarkingStackClosure; // -- ditto -- 526 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 527 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 528 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 529 friend class VM_CMS_Operation; 530 friend class VM_CMS_Initial_Mark; 531 friend class VM_CMS_Final_Remark; 532 friend class TraceCMSMemoryManagerStats; 533 534 private: 535 jlong _time_of_last_gc; 536 void update_time_of_last_gc(jlong now) { 537 _time_of_last_gc = now; 538 } 539 540 OopTaskQueueSet* _task_queues; 541 542 // Overflow list of grey objects, threaded through mark-word 543 // Manipulated with CAS in the parallel/multi-threaded case. 544 oop _overflow_list; 545 // The following array-pair keeps track of mark words 546 // displaced for accommodating overflow list above. 547 // This code will likely be revisited under RFE#4922830. 548 Stack<oop, mtGC> _preserved_oop_stack; 549 Stack<markOop, mtGC> _preserved_mark_stack; 550 551 int* _hash_seed; 552 553 // In support of multi-threaded concurrent phases 554 YieldingFlexibleWorkGang* _conc_workers; 555 556 // Performance Counters 557 CollectorCounters* _gc_counters; 558 559 // Initialization Errors 560 bool _completed_initialization; 561 562 // In support of ExplicitGCInvokesConcurrent 563 static bool _full_gc_requested; 564 static GCCause::Cause _full_gc_cause; 565 unsigned int _collection_count_start; 566 567 // Should we unload classes this concurrent cycle? 568 bool _should_unload_classes; 569 unsigned int _concurrent_cycles_since_last_unload; 570 unsigned int concurrent_cycles_since_last_unload() const { 571 return _concurrent_cycles_since_last_unload; 572 } 573 // Did we (allow) unload classes in the previous concurrent cycle? 574 bool unloaded_classes_last_cycle() const { 575 return concurrent_cycles_since_last_unload() == 0; 576 } 577 // Root scanning options for perm gen 578 int _roots_scanning_options; 579 int roots_scanning_options() const { return _roots_scanning_options; } 580 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 581 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 582 583 // Verification support 584 CMSBitMap _verification_mark_bm; 585 void verify_after_remark_work_1(); 586 void verify_after_remark_work_2(); 587 588 // True if any verification flag is on. 589 bool _verifying; 590 bool verifying() const { return _verifying; } 591 void set_verifying(bool v) { _verifying = v; } 592 593 // Collector policy 594 ConcurrentMarkSweepPolicy* _collector_policy; 595 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 596 597 void set_did_compact(bool v); 598 599 // XXX Move these to CMSStats ??? FIX ME !!! 600 elapsedTimer _inter_sweep_timer; // Time between sweeps 601 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 602 // Padded decaying average estimates of the above 603 AdaptivePaddedAverage _inter_sweep_estimate; 604 AdaptivePaddedAverage _intra_sweep_estimate; 605 606 CMSTracer* _gc_tracer_cm; 607 ConcurrentGCTimer* _gc_timer_cm; 608 609 bool _cms_start_registered; 610 611 GCHeapSummary _last_heap_summary; 612 MetaspaceSummary _last_metaspace_summary; 613 614 void register_gc_start(GCCause::Cause cause); 615 void register_gc_end(); 616 void save_heap_summary(); 617 void report_heap_summary(GCWhen::Type when); 618 619 protected: 620 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 621 MemRegion _span; // Span covering above two 622 CardTableRS* _ct; // Card table 623 624 // CMS marking support structures 625 CMSBitMap _markBitMap; 626 CMSBitMap _modUnionTable; 627 CMSMarkStack _markStack; 628 629 HeapWord* _restart_addr; // In support of marking stack overflow 630 void lower_restart_addr(HeapWord* low); 631 632 // Counters in support of marking stack / work queue overflow handling: 633 // a non-zero value indicates certain types of overflow events during 634 // the current CMS cycle and could lead to stack resizing efforts at 635 // an opportune future time. 636 size_t _ser_pmc_preclean_ovflw; 637 size_t _ser_pmc_remark_ovflw; 638 size_t _par_pmc_remark_ovflw; 639 size_t _ser_kac_preclean_ovflw; 640 size_t _ser_kac_ovflw; 641 size_t _par_kac_ovflw; 642 NOT_PRODUCT(ssize_t _num_par_pushes;) 643 644 // ("Weak") Reference processing support. 645 ReferenceProcessor* _ref_processor; 646 CMSIsAliveClosure _is_alive_closure; 647 // Keep this textually after _markBitMap and _span; c'tor dependency. 648 649 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 650 ModUnionClosurePar _modUnionClosurePar; 651 652 // CMS abstract state machine 653 // initial_state: Idling 654 // next_state(Idling) = {Marking} 655 // next_state(Marking) = {Precleaning, Sweeping} 656 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 657 // next_state(AbortablePreclean) = {FinalMarking} 658 // next_state(FinalMarking) = {Sweeping} 659 // next_state(Sweeping) = {Resizing} 660 // next_state(Resizing) = {Resetting} 661 // next_state(Resetting) = {Idling} 662 // The numeric values below are chosen so that: 663 // . _collectorState <= Idling == post-sweep && pre-mark 664 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 665 // precleaning || abortablePrecleanb 666 public: 667 enum CollectorState { 668 Resizing = 0, 669 Resetting = 1, 670 Idling = 2, 671 InitialMarking = 3, 672 Marking = 4, 673 Precleaning = 5, 674 AbortablePreclean = 6, 675 FinalMarking = 7, 676 Sweeping = 8 677 }; 678 protected: 679 static CollectorState _collectorState; 680 681 // State related to prologue/epilogue invocation for my generations 682 bool _between_prologue_and_epilogue; 683 684 // Signaling/State related to coordination between fore- and background GC 685 // Note: When the baton has been passed from background GC to foreground GC, 686 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 687 static bool _foregroundGCIsActive; // true iff foreground collector is active or 688 // wants to go active 689 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 690 // yet passed the baton to the foreground GC 691 692 // Support for CMSScheduleRemark (abortable preclean) 693 bool _abort_preclean; 694 bool _start_sampling; 695 696 int _numYields; 697 size_t _numDirtyCards; 698 size_t _sweep_count; 699 700 // Occupancy used for bootstrapping stats 701 double _bootstrap_occupancy; 702 703 // Timer 704 elapsedTimer _timer; 705 706 // Timing, allocation and promotion statistics, used for scheduling. 707 CMSStats _stats; 708 709 enum CMS_op_type { 710 CMS_op_checkpointRootsInitial, 711 CMS_op_checkpointRootsFinal 712 }; 713 714 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 715 bool stop_world_and_do(CMS_op_type op); 716 717 OopTaskQueueSet* task_queues() { return _task_queues; } 718 int* hash_seed(int i) { return &_hash_seed[i]; } 719 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 720 721 // Support for parallelizing Eden rescan in CMS remark phase 722 void sample_eden(); // ... sample Eden space top 723 724 private: 725 // Support for parallelizing young gen rescan in CMS remark phase 726 ParNewGeneration* _young_gen; 727 728 HeapWord** _top_addr; // ... Top of Eden 729 HeapWord** _end_addr; // ... End of Eden 730 Mutex* _eden_chunk_lock; 731 HeapWord** _eden_chunk_array; // ... Eden partitioning array 732 size_t _eden_chunk_index; // ... top (exclusive) of array 733 size_t _eden_chunk_capacity; // ... max entries in array 734 735 // Support for parallelizing survivor space rescan 736 HeapWord** _survivor_chunk_array; 737 size_t _survivor_chunk_index; 738 size_t _survivor_chunk_capacity; 739 size_t* _cursor; 740 ChunkArray* _survivor_plab_array; 741 742 // Support for marking stack overflow handling 743 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 744 bool par_take_from_overflow_list(size_t num, 745 OopTaskQueue* to_work_q, 746 int no_of_gc_threads); 747 void push_on_overflow_list(oop p); 748 void par_push_on_overflow_list(oop p); 749 // The following is, obviously, not, in general, "MT-stable" 750 bool overflow_list_is_empty() const; 751 752 void preserve_mark_if_necessary(oop p); 753 void par_preserve_mark_if_necessary(oop p); 754 void preserve_mark_work(oop p, markOop m); 755 void restore_preserved_marks_if_any(); 756 NOT_PRODUCT(bool no_preserved_marks() const;) 757 // In support of testing overflow code 758 NOT_PRODUCT(int _overflow_counter;) 759 NOT_PRODUCT(bool simulate_overflow();) // Sequential 760 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 761 762 // CMS work methods 763 void checkpointRootsInitialWork(); // Initial checkpoint work 764 765 // A return value of false indicates failure due to stack overflow 766 bool markFromRootsWork(); // Concurrent marking work 767 768 public: // FIX ME!!! only for testing 769 bool do_marking_st(); // Single-threaded marking 770 bool do_marking_mt(); // Multi-threaded marking 771 772 private: 773 774 // Concurrent precleaning work 775 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen, 776 ScanMarkedObjectsAgainCarefullyClosure* cl); 777 size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen, 778 ScanMarkedObjectsAgainCarefullyClosure* cl); 779 // Does precleaning work, returning a quantity indicative of 780 // the amount of "useful work" done. 781 size_t preclean_work(bool clean_refs, bool clean_survivors); 782 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 783 void abortable_preclean(); // Preclean while looking for possible abort 784 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 785 // Helper function for above; merge-sorts the per-thread plab samples 786 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 787 // Resets (i.e. clears) the per-thread plab sample vectors 788 void reset_survivor_plab_arrays(); 789 790 // Final (second) checkpoint work 791 void checkpointRootsFinalWork(); 792 // Work routine for parallel version of remark 793 void do_remark_parallel(); 794 // Work routine for non-parallel version of remark 795 void do_remark_non_parallel(); 796 // Reference processing work routine (during second checkpoint) 797 void refProcessingWork(); 798 799 // Concurrent sweeping work 800 void sweepWork(ConcurrentMarkSweepGeneration* old_gen); 801 802 // Concurrent resetting of support data structures 803 void reset_concurrent(); 804 // Resetting of support data structures from a STW full GC 805 void reset_stw(); 806 807 // Clear _expansion_cause fields of constituent generations 808 void clear_expansion_cause(); 809 810 // An auxiliary method used to record the ends of 811 // used regions of each generation to limit the extent of sweep 812 void save_sweep_limits(); 813 814 // A work method used by the foreground collector to do 815 // a mark-sweep-compact. 816 void do_compaction_work(bool clear_all_soft_refs); 817 818 // Work methods for reporting concurrent mode interruption or failure 819 bool is_external_interruption(); 820 void report_concurrent_mode_interruption(); 821 822 // If the background GC is active, acquire control from the background 823 // GC and do the collection. 824 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 825 826 // For synchronizing passing of control from background to foreground 827 // GC. waitForForegroundGC() is called by the background 828 // collector. It if had to wait for a foreground collection, 829 // it returns true and the background collection should assume 830 // that the collection was finished by the foreground 831 // collector. 832 bool waitForForegroundGC(); 833 834 size_t block_size_using_printezis_bits(HeapWord* addr) const; 835 size_t block_size_if_printezis_bits(HeapWord* addr) const; 836 HeapWord* next_card_start_after_block(HeapWord* addr) const; 837 838 void setup_cms_unloading_and_verification_state(); 839 public: 840 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 841 CardTableRS* ct, 842 ConcurrentMarkSweepPolicy* cp); 843 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 844 845 ReferenceProcessor* ref_processor() { return _ref_processor; } 846 void ref_processor_init(); 847 848 Mutex* bitMapLock() const { return _markBitMap.lock(); } 849 static CollectorState abstract_state() { return _collectorState; } 850 851 bool should_abort_preclean() const; // Whether preclean should be aborted. 852 size_t get_eden_used() const; 853 size_t get_eden_capacity() const; 854 855 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 856 857 // Locking checks 858 NOT_PRODUCT(static bool have_cms_token();) 859 860 bool shouldConcurrentCollect(); 861 862 void collect(bool full, 863 bool clear_all_soft_refs, 864 size_t size, 865 bool tlab); 866 void collect_in_background(GCCause::Cause cause); 867 868 // In support of ExplicitGCInvokesConcurrent 869 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 870 // Should we unload classes in a particular concurrent cycle? 871 bool should_unload_classes() const { 872 return _should_unload_classes; 873 } 874 void update_should_unload_classes(); 875 876 void direct_allocated(HeapWord* start, size_t size); 877 878 // Object is dead if not marked and current phase is sweeping. 879 bool is_dead_obj(oop obj) const; 880 881 // After a promotion (of "start"), do any necessary marking. 882 // If "par", then it's being done by a parallel GC thread. 883 // The last two args indicate if we need precise marking 884 // and if so the size of the object so it can be dirtied 885 // in its entirety. 886 void promoted(bool par, HeapWord* start, 887 bool is_obj_array, size_t obj_size); 888 889 void getFreelistLocks() const; 890 void releaseFreelistLocks() const; 891 bool haveFreelistLocks() const; 892 893 // Adjust size of underlying generation 894 void compute_new_size(); 895 896 // GC prologue and epilogue 897 void gc_prologue(bool full); 898 void gc_epilogue(bool full); 899 900 jlong time_of_last_gc(jlong now) { 901 if (_collectorState <= Idling) { 902 // gc not in progress 903 return _time_of_last_gc; 904 } else { 905 // collection in progress 906 return now; 907 } 908 } 909 910 // Support for parallel remark of survivor space 911 void* get_data_recorder(int thr_num); 912 void sample_eden_chunk(); 913 914 CMSBitMap* markBitMap() { return &_markBitMap; } 915 void directAllocated(HeapWord* start, size_t size); 916 917 // Main CMS steps and related support 918 void checkpointRootsInitial(); 919 bool markFromRoots(); // a return value of false indicates failure 920 // due to stack overflow 921 void preclean(); 922 void checkpointRootsFinal(); 923 void sweep(); 924 925 // Check that the currently executing thread is the expected 926 // one (foreground collector or background collector). 927 static void check_correct_thread_executing() PRODUCT_RETURN; 928 929 NOT_PRODUCT(bool is_cms_reachable(HeapWord* addr);) 930 931 // Performance Counter Support 932 CollectorCounters* counters() { return _gc_counters; } 933 934 // Timer stuff 935 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 936 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 937 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 938 jlong timerTicks() { assert(!_timer.is_active(), "Error"); return _timer.ticks(); } 939 940 int yields() { return _numYields; } 941 void resetYields() { _numYields = 0; } 942 void incrementYields() { _numYields++; } 943 void resetNumDirtyCards() { _numDirtyCards = 0; } 944 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 945 size_t numDirtyCards() { return _numDirtyCards; } 946 947 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 948 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 949 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 950 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 951 size_t sweep_count() const { return _sweep_count; } 952 void increment_sweep_count() { _sweep_count++; } 953 954 // Timers/stats for gc scheduling and incremental mode pacing. 955 CMSStats& stats() { return _stats; } 956 957 // Adaptive size policy 958 AdaptiveSizePolicy* size_policy(); 959 960 static void print_on_error(outputStream* st); 961 962 // Debugging 963 void verify(); 964 bool verify_after_remark(); 965 void verify_ok_to_terminate() const PRODUCT_RETURN; 966 void verify_work_stacks_empty() const PRODUCT_RETURN; 967 void verify_overflow_empty() const PRODUCT_RETURN; 968 969 // Convenience methods in support of debugging 970 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 971 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 972 973 // Accessors 974 CMSMarkStack* verification_mark_stack() { return &_markStack; } 975 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 976 977 // Initialization errors 978 bool completed_initialization() { return _completed_initialization; } 979 980 void print_eden_and_survivor_chunk_arrays(); 981 982 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 983 }; 984 985 class CMSExpansionCause : public AllStatic { 986 public: 987 enum Cause { 988 _no_expansion, 989 _satisfy_free_ratio, 990 _satisfy_promotion, 991 _satisfy_allocation, 992 _allocate_par_lab, 993 _allocate_par_spooling_space, 994 _adaptive_size_policy 995 }; 996 // Return a string describing the cause of the expansion. 997 static const char* to_string(CMSExpansionCause::Cause cause); 998 }; 999 1000 class ConcurrentMarkSweepGeneration: public CardGeneration { 1001 friend class VMStructs; 1002 friend class ConcurrentMarkSweepThread; 1003 friend class ConcurrentMarkSweep; 1004 friend class CMSCollector; 1005 protected: 1006 static CMSCollector* _collector; // the collector that collects us 1007 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1008 1009 // Performance Counters 1010 GenerationCounters* _gen_counters; 1011 GSpaceCounters* _space_counters; 1012 1013 // Words directly allocated, used by CMSStats. 1014 size_t _direct_allocated_words; 1015 1016 // Non-product stat counters 1017 NOT_PRODUCT( 1018 size_t _numObjectsPromoted; 1019 size_t _numWordsPromoted; 1020 size_t _numObjectsAllocated; 1021 size_t _numWordsAllocated; 1022 ) 1023 1024 // Used for sizing decisions 1025 bool _incremental_collection_failed; 1026 bool incremental_collection_failed() { 1027 return _incremental_collection_failed; 1028 } 1029 void set_incremental_collection_failed() { 1030 _incremental_collection_failed = true; 1031 } 1032 void clear_incremental_collection_failed() { 1033 _incremental_collection_failed = false; 1034 } 1035 1036 // accessors 1037 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1038 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1039 1040 // Accessing spaces 1041 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } 1042 1043 private: 1044 // For parallel young-gen GC support. 1045 CMSParGCThreadState** _par_gc_thread_states; 1046 1047 // Reason generation was expanded 1048 CMSExpansionCause::Cause _expansion_cause; 1049 1050 // In support of MinChunkSize being larger than min object size 1051 const double _dilatation_factor; 1052 1053 // True if a compacting collection was done. 1054 bool _did_compact; 1055 bool did_compact() { return _did_compact; } 1056 1057 // Fraction of current occupancy at which to start a CMS collection which 1058 // will collect this generation (at least). 1059 double _initiating_occupancy; 1060 1061 protected: 1062 // Shrink generation by specified size (returns false if unable to shrink) 1063 void shrink_free_list_by(size_t bytes); 1064 1065 // Update statistics for GC 1066 virtual void update_gc_stats(Generation* current_generation, bool full); 1067 1068 // Maximum available space in the generation (including uncommitted) 1069 // space. 1070 size_t max_available() const; 1071 1072 // getter and initializer for _initiating_occupancy field. 1073 double initiating_occupancy() const { return _initiating_occupancy; } 1074 void init_initiating_occupancy(intx io, uintx tr); 1075 1076 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1077 1078 void assert_correct_size_change_locking(); 1079 1080 public: 1081 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, CardTableRS* ct); 1082 1083 // Accessors 1084 CMSCollector* collector() const { return _collector; } 1085 static void set_collector(CMSCollector* collector) { 1086 assert(_collector == NULL, "already set"); 1087 _collector = collector; 1088 } 1089 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1090 1091 Mutex* freelistLock() const; 1092 1093 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1094 1095 void set_did_compact(bool v) { _did_compact = v; } 1096 1097 bool refs_discovery_is_atomic() const { return false; } 1098 bool refs_discovery_is_mt() const { 1099 // Note: CMS does MT-discovery during the parallel-remark 1100 // phases. Use ReferenceProcessorMTMutator to make refs 1101 // discovery MT-safe during such phases or other parallel 1102 // discovery phases in the future. This may all go away 1103 // if/when we decide that refs discovery is sufficiently 1104 // rare that the cost of the CAS's involved is in the 1105 // noise. That's a measurement that should be done, and 1106 // the code simplified if that turns out to be the case. 1107 return ConcGCThreads > 1; 1108 } 1109 1110 // Override 1111 virtual void ref_processor_init(); 1112 1113 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1114 1115 // Space enquiries 1116 double occupancy() const { return ((double)used())/((double)capacity()); } 1117 size_t contiguous_available() const; 1118 size_t unsafe_max_alloc_nogc() const; 1119 1120 // over-rides 1121 MemRegion used_region_at_save_marks() const; 1122 1123 // Adjust quantities in the generation affected by 1124 // the compaction. 1125 void reset_after_compaction(); 1126 1127 // Allocation support 1128 HeapWord* allocate(size_t size, bool tlab); 1129 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1130 oop promote(oop obj, size_t obj_size); 1131 HeapWord* par_allocate(size_t size, bool tlab) { 1132 return allocate(size, tlab); 1133 } 1134 1135 1136 // Used by CMSStats to track direct allocation. The value is sampled and 1137 // reset after each young gen collection. 1138 size_t direct_allocated_words() const { return _direct_allocated_words; } 1139 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1140 1141 // Overrides for parallel promotion. 1142 virtual oop par_promote(int thread_num, 1143 oop obj, markOop m, size_t word_sz); 1144 virtual void par_promote_alloc_done(int thread_num); 1145 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1146 1147 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1148 1149 // Inform this (old) generation that a promotion failure was 1150 // encountered during a collection of the young generation. 1151 virtual void promotion_failure_occurred(); 1152 1153 bool should_collect(bool full, size_t size, bool tlab); 1154 virtual bool should_concurrent_collect() const; 1155 virtual bool is_too_full() const; 1156 void collect(bool full, 1157 bool clear_all_soft_refs, 1158 size_t size, 1159 bool tlab); 1160 1161 HeapWord* expand_and_allocate(size_t word_size, 1162 bool tlab, 1163 bool parallel = false); 1164 1165 // GC prologue and epilogue 1166 void gc_prologue(bool full); 1167 void gc_prologue_work(bool full, bool registerClosure, 1168 ModUnionClosure* modUnionClosure); 1169 void gc_epilogue(bool full); 1170 void gc_epilogue_work(bool full); 1171 1172 // Time since last GC of this generation 1173 jlong time_of_last_gc(jlong now) { 1174 return collector()->time_of_last_gc(now); 1175 } 1176 void update_time_of_last_gc(jlong now) { 1177 collector()-> update_time_of_last_gc(now); 1178 } 1179 1180 // Allocation failure 1181 void shrink(size_t bytes); 1182 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1183 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1184 1185 // Iteration support and related enquiries 1186 void save_marks(); 1187 bool no_allocs_since_save_marks(); 1188 1189 // Iteration support specific to CMS generations 1190 void save_sweep_limit(); 1191 1192 // More iteration support 1193 virtual void oop_iterate(ExtendedOopClosure* cl); 1194 virtual void safe_object_iterate(ObjectClosure* cl); 1195 virtual void object_iterate(ObjectClosure* cl); 1196 1197 // Need to declare the full complement of closures, whether we'll 1198 // override them or not, or get message from the compiler: 1199 // oop_since_save_marks_iterate_nv hides virtual function... 1200 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1201 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1202 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1203 1204 // Smart allocation XXX -- move to CFLSpace? 1205 void setNearLargestChunk(); 1206 bool isNearLargestChunk(HeapWord* addr); 1207 1208 // Get the chunk at the end of the space. Delegates to 1209 // the space. 1210 FreeChunk* find_chunk_at_end(); 1211 1212 void post_compact(); 1213 1214 // Debugging 1215 void prepare_for_verify(); 1216 void verify(); 1217 void print_statistics() PRODUCT_RETURN; 1218 1219 // Performance Counters support 1220 virtual void update_counters(); 1221 virtual void update_counters(size_t used); 1222 void initialize_performance_counters(); 1223 CollectorCounters* counters() { return collector()->counters(); } 1224 1225 // Support for parallel remark of survivor space 1226 void* get_data_recorder(int thr_num) { 1227 //Delegate to collector 1228 return collector()->get_data_recorder(thr_num); 1229 } 1230 void sample_eden_chunk() { 1231 //Delegate to collector 1232 return collector()->sample_eden_chunk(); 1233 } 1234 1235 // Printing 1236 const char* name() const; 1237 virtual const char* short_name() const { return "CMS"; } 1238 void print() const; 1239 1240 // Resize the generation after a compacting GC. The 1241 // generation can be treated as a contiguous space 1242 // after the compaction. 1243 virtual void compute_new_size(); 1244 // Resize the generation after a non-compacting 1245 // collection. 1246 void compute_new_size_free_list(); 1247 }; 1248 1249 // 1250 // Closures of various sorts used by CMS to accomplish its work 1251 // 1252 1253 // This closure is used to do concurrent marking from the roots 1254 // following the first checkpoint. 1255 class MarkFromRootsClosure: public BitMapClosure { 1256 CMSCollector* _collector; 1257 MemRegion _span; 1258 CMSBitMap* _bitMap; 1259 CMSBitMap* _mut; 1260 CMSMarkStack* _markStack; 1261 bool _yield; 1262 int _skipBits; 1263 HeapWord* _finger; 1264 HeapWord* _threshold; 1265 DEBUG_ONLY(bool _verifying;) 1266 1267 public: 1268 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1269 CMSBitMap* bitMap, 1270 CMSMarkStack* markStack, 1271 bool should_yield, bool verifying = false); 1272 bool do_bit(size_t offset); 1273 void reset(HeapWord* addr); 1274 inline void do_yield_check(); 1275 1276 private: 1277 void scanOopsInOop(HeapWord* ptr); 1278 void do_yield_work(); 1279 }; 1280 1281 // This closure is used to do concurrent multi-threaded 1282 // marking from the roots following the first checkpoint. 1283 // XXX This should really be a subclass of The serial version 1284 // above, but i have not had the time to refactor things cleanly. 1285 class Par_MarkFromRootsClosure: public BitMapClosure { 1286 CMSCollector* _collector; 1287 MemRegion _whole_span; 1288 MemRegion _span; 1289 CMSBitMap* _bit_map; 1290 CMSBitMap* _mut; 1291 OopTaskQueue* _work_queue; 1292 CMSMarkStack* _overflow_stack; 1293 int _skip_bits; 1294 HeapWord* _finger; 1295 HeapWord* _threshold; 1296 CMSConcMarkingTask* _task; 1297 public: 1298 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1299 MemRegion span, 1300 CMSBitMap* bit_map, 1301 OopTaskQueue* work_queue, 1302 CMSMarkStack* overflow_stack); 1303 bool do_bit(size_t offset); 1304 inline void do_yield_check(); 1305 1306 private: 1307 void scan_oops_in_oop(HeapWord* ptr); 1308 void do_yield_work(); 1309 bool get_work_from_overflow_stack(); 1310 }; 1311 1312 // The following closures are used to do certain kinds of verification of 1313 // CMS marking. 1314 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1315 CMSCollector* _collector; 1316 MemRegion _span; 1317 CMSBitMap* _verification_bm; 1318 CMSBitMap* _cms_bm; 1319 CMSMarkStack* _mark_stack; 1320 protected: 1321 void do_oop(oop p); 1322 template <class T> inline void do_oop_work(T *p) { 1323 oop obj = oopDesc::load_decode_heap_oop(p); 1324 do_oop(obj); 1325 } 1326 public: 1327 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1328 MemRegion span, 1329 CMSBitMap* verification_bm, 1330 CMSBitMap* cms_bm, 1331 CMSMarkStack* mark_stack); 1332 void do_oop(oop* p); 1333 void do_oop(narrowOop* p); 1334 1335 // Deal with a stack overflow condition 1336 void handle_stack_overflow(HeapWord* lost); 1337 }; 1338 1339 class MarkFromRootsVerifyClosure: public BitMapClosure { 1340 CMSCollector* _collector; 1341 MemRegion _span; 1342 CMSBitMap* _verification_bm; 1343 CMSBitMap* _cms_bm; 1344 CMSMarkStack* _mark_stack; 1345 HeapWord* _finger; 1346 PushAndMarkVerifyClosure _pam_verify_closure; 1347 public: 1348 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1349 CMSBitMap* verification_bm, 1350 CMSBitMap* cms_bm, 1351 CMSMarkStack* mark_stack); 1352 bool do_bit(size_t offset); 1353 void reset(HeapWord* addr); 1354 }; 1355 1356 1357 // This closure is used to check that a certain set of bits is 1358 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1359 class FalseBitMapClosure: public BitMapClosure { 1360 public: 1361 bool do_bit(size_t offset) { 1362 guarantee(false, "Should not have a 1 bit"); 1363 return true; 1364 } 1365 }; 1366 1367 // A version of ObjectClosure with "memory" (see _previous_address below) 1368 class UpwardsObjectClosure: public BoolObjectClosure { 1369 HeapWord* _previous_address; 1370 public: 1371 UpwardsObjectClosure() : _previous_address(NULL) { } 1372 void set_previous(HeapWord* addr) { _previous_address = addr; } 1373 HeapWord* previous() { return _previous_address; } 1374 // A return value of "true" can be used by the caller to decide 1375 // if this object's end should *NOT* be recorded in 1376 // _previous_address above. 1377 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1378 }; 1379 1380 // This closure is used during the second checkpointing phase 1381 // to rescan the marked objects on the dirty cards in the mod 1382 // union table and the card table proper. It's invoked via 1383 // MarkFromDirtyCardsClosure below. It uses either 1384 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1385 // declared in genOopClosures.hpp to accomplish some of its work. 1386 // In the parallel case the bitMap is shared, so access to 1387 // it needs to be suitably synchronized for updates by embedded 1388 // closures that update it; however, this closure itself only 1389 // reads the bit_map and because it is idempotent, is immune to 1390 // reading stale values. 1391 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1392 #ifdef ASSERT 1393 CMSCollector* _collector; 1394 MemRegion _span; 1395 union { 1396 CMSMarkStack* _mark_stack; 1397 OopTaskQueue* _work_queue; 1398 }; 1399 #endif // ASSERT 1400 bool _parallel; 1401 CMSBitMap* _bit_map; 1402 union { 1403 MarkRefsIntoAndScanClosure* _scan_closure; 1404 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1405 }; 1406 1407 public: 1408 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1409 MemRegion span, 1410 ReferenceProcessor* rp, 1411 CMSBitMap* bit_map, 1412 CMSMarkStack* mark_stack, 1413 MarkRefsIntoAndScanClosure* cl): 1414 #ifdef ASSERT 1415 _collector(collector), 1416 _span(span), 1417 _mark_stack(mark_stack), 1418 #endif // ASSERT 1419 _parallel(false), 1420 _bit_map(bit_map), 1421 _scan_closure(cl) { } 1422 1423 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1424 MemRegion span, 1425 ReferenceProcessor* rp, 1426 CMSBitMap* bit_map, 1427 OopTaskQueue* work_queue, 1428 Par_MarkRefsIntoAndScanClosure* cl): 1429 #ifdef ASSERT 1430 _collector(collector), 1431 _span(span), 1432 _work_queue(work_queue), 1433 #endif // ASSERT 1434 _parallel(true), 1435 _bit_map(bit_map), 1436 _par_scan_closure(cl) { } 1437 1438 bool do_object_b(oop obj) { 1439 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1440 return false; 1441 } 1442 bool do_object_bm(oop p, MemRegion mr); 1443 }; 1444 1445 // This closure is used during the second checkpointing phase 1446 // to rescan the marked objects on the dirty cards in the mod 1447 // union table and the card table proper. It invokes 1448 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1449 // In the parallel case, the bit map is shared and requires 1450 // synchronized access. 1451 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1452 CompactibleFreeListSpace* _space; 1453 ScanMarkedObjectsAgainClosure _scan_cl; 1454 size_t _num_dirty_cards; 1455 1456 public: 1457 MarkFromDirtyCardsClosure(CMSCollector* collector, 1458 MemRegion span, 1459 CompactibleFreeListSpace* space, 1460 CMSBitMap* bit_map, 1461 CMSMarkStack* mark_stack, 1462 MarkRefsIntoAndScanClosure* cl): 1463 _space(space), 1464 _num_dirty_cards(0), 1465 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1466 mark_stack, cl) { } 1467 1468 MarkFromDirtyCardsClosure(CMSCollector* collector, 1469 MemRegion span, 1470 CompactibleFreeListSpace* space, 1471 CMSBitMap* bit_map, 1472 OopTaskQueue* work_queue, 1473 Par_MarkRefsIntoAndScanClosure* cl): 1474 _space(space), 1475 _num_dirty_cards(0), 1476 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1477 work_queue, cl) { } 1478 1479 void do_MemRegion(MemRegion mr); 1480 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1481 size_t num_dirty_cards() { return _num_dirty_cards; } 1482 }; 1483 1484 // This closure is used in the non-product build to check 1485 // that there are no MemRegions with a certain property. 1486 class FalseMemRegionClosure: public MemRegionClosure { 1487 void do_MemRegion(MemRegion mr) { 1488 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1489 guarantee(false, "Should never be here"); 1490 } 1491 }; 1492 1493 // This closure is used during the precleaning phase 1494 // to "carefully" rescan marked objects on dirty cards. 1495 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1496 // to accomplish some of its work. 1497 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1498 CMSCollector* _collector; 1499 MemRegion _span; 1500 bool _yield; 1501 Mutex* _freelistLock; 1502 CMSBitMap* _bitMap; 1503 CMSMarkStack* _markStack; 1504 MarkRefsIntoAndScanClosure* _scanningClosure; 1505 1506 public: 1507 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1508 MemRegion span, 1509 CMSBitMap* bitMap, 1510 CMSMarkStack* markStack, 1511 MarkRefsIntoAndScanClosure* cl, 1512 bool should_yield): 1513 _collector(collector), 1514 _span(span), 1515 _yield(should_yield), 1516 _bitMap(bitMap), 1517 _markStack(markStack), 1518 _scanningClosure(cl) { 1519 } 1520 1521 void do_object(oop p) { 1522 guarantee(false, "call do_object_careful instead"); 1523 } 1524 1525 size_t do_object_careful(oop p) { 1526 guarantee(false, "Unexpected caller"); 1527 return 0; 1528 } 1529 1530 size_t do_object_careful_m(oop p, MemRegion mr); 1531 1532 void setFreelistLock(Mutex* m) { 1533 _freelistLock = m; 1534 _scanningClosure->set_freelistLock(m); 1535 } 1536 1537 private: 1538 inline bool do_yield_check(); 1539 1540 void do_yield_work(); 1541 }; 1542 1543 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1544 CMSCollector* _collector; 1545 MemRegion _span; 1546 bool _yield; 1547 CMSBitMap* _bit_map; 1548 CMSMarkStack* _mark_stack; 1549 PushAndMarkClosure* _scanning_closure; 1550 unsigned int _before_count; 1551 1552 public: 1553 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1554 MemRegion span, 1555 CMSBitMap* bit_map, 1556 CMSMarkStack* mark_stack, 1557 PushAndMarkClosure* cl, 1558 unsigned int before_count, 1559 bool should_yield): 1560 _collector(collector), 1561 _span(span), 1562 _yield(should_yield), 1563 _bit_map(bit_map), 1564 _mark_stack(mark_stack), 1565 _scanning_closure(cl), 1566 _before_count(before_count) 1567 { } 1568 1569 void do_object(oop p) { 1570 guarantee(false, "call do_object_careful instead"); 1571 } 1572 1573 size_t do_object_careful(oop p); 1574 1575 size_t do_object_careful_m(oop p, MemRegion mr) { 1576 guarantee(false, "Unexpected caller"); 1577 return 0; 1578 } 1579 1580 private: 1581 inline void do_yield_check(); 1582 void do_yield_work(); 1583 }; 1584 1585 // This closure is used to accomplish the sweeping work 1586 // after the second checkpoint but before the concurrent reset 1587 // phase. 1588 // 1589 // Terminology 1590 // left hand chunk (LHC) - block of one or more chunks currently being 1591 // coalesced. The LHC is available for coalescing with a new chunk. 1592 // right hand chunk (RHC) - block that is currently being swept that is 1593 // free or garbage that can be coalesced with the LHC. 1594 // _inFreeRange is true if there is currently a LHC 1595 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1596 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1597 // _freeFinger is the address of the current LHC 1598 class SweepClosure: public BlkClosureCareful { 1599 CMSCollector* _collector; // collector doing the work 1600 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1601 CompactibleFreeListSpace* _sp; // Space being swept 1602 HeapWord* _limit;// the address at or above which the sweep should stop 1603 // because we do not expect newly garbage blocks 1604 // eligible for sweeping past that address. 1605 Mutex* _freelistLock; // Free list lock (in space) 1606 CMSBitMap* _bitMap; // Marking bit map (in 1607 // generation) 1608 bool _inFreeRange; // Indicates if we are in the 1609 // midst of a free run 1610 bool _freeRangeInFreeLists; 1611 // Often, we have just found 1612 // a free chunk and started 1613 // a new free range; we do not 1614 // eagerly remove this chunk from 1615 // the free lists unless there is 1616 // a possibility of coalescing. 1617 // When true, this flag indicates 1618 // that the _freeFinger below 1619 // points to a potentially free chunk 1620 // that may still be in the free lists 1621 bool _lastFreeRangeCoalesced; 1622 // free range contains chunks 1623 // coalesced 1624 bool _yield; 1625 // Whether sweeping should be 1626 // done with yields. For instance 1627 // when done by the foreground 1628 // collector we shouldn't yield. 1629 HeapWord* _freeFinger; // When _inFreeRange is set, the 1630 // pointer to the "left hand 1631 // chunk" 1632 size_t _freeRangeSize; 1633 // When _inFreeRange is set, this 1634 // indicates the accumulated size 1635 // of the "left hand chunk" 1636 NOT_PRODUCT( 1637 size_t _numObjectsFreed; 1638 size_t _numWordsFreed; 1639 size_t _numObjectsLive; 1640 size_t _numWordsLive; 1641 size_t _numObjectsAlreadyFree; 1642 size_t _numWordsAlreadyFree; 1643 FreeChunk* _last_fc; 1644 ) 1645 private: 1646 // Code that is common to a free chunk or garbage when 1647 // encountered during sweeping. 1648 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1649 // Process a free chunk during sweeping. 1650 void do_already_free_chunk(FreeChunk *fc); 1651 // Work method called when processing an already free or a 1652 // freshly garbage chunk to do a lookahead and possibly a 1653 // preemptive flush if crossing over _limit. 1654 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1655 // Process a garbage chunk during sweeping. 1656 size_t do_garbage_chunk(FreeChunk *fc); 1657 // Process a live chunk during sweeping. 1658 size_t do_live_chunk(FreeChunk* fc); 1659 1660 // Accessors. 1661 HeapWord* freeFinger() const { return _freeFinger; } 1662 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1663 bool inFreeRange() const { return _inFreeRange; } 1664 void set_inFreeRange(bool v) { _inFreeRange = v; } 1665 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1666 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1667 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1668 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1669 1670 // Initialize a free range. 1671 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1672 // Return this chunk to the free lists. 1673 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1674 1675 // Check if we should yield and do so when necessary. 1676 inline void do_yield_check(HeapWord* addr); 1677 1678 // Yield 1679 void do_yield_work(HeapWord* addr); 1680 1681 // Debugging/Printing 1682 void print_free_block_coalesced(FreeChunk* fc) const; 1683 1684 public: 1685 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1686 CMSBitMap* bitMap, bool should_yield); 1687 ~SweepClosure() PRODUCT_RETURN; 1688 1689 size_t do_blk_careful(HeapWord* addr); 1690 void print() const { print_on(tty); } 1691 void print_on(outputStream *st) const; 1692 }; 1693 1694 // Closures related to weak references processing 1695 1696 // During CMS' weak reference processing, this is a 1697 // work-routine/closure used to complete transitive 1698 // marking of objects as live after a certain point 1699 // in which an initial set has been completely accumulated. 1700 // This closure is currently used both during the final 1701 // remark stop-world phase, as well as during the concurrent 1702 // precleaning of the discovered reference lists. 1703 class CMSDrainMarkingStackClosure: public VoidClosure { 1704 CMSCollector* _collector; 1705 MemRegion _span; 1706 CMSMarkStack* _mark_stack; 1707 CMSBitMap* _bit_map; 1708 CMSKeepAliveClosure* _keep_alive; 1709 bool _concurrent_precleaning; 1710 public: 1711 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1712 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1713 CMSKeepAliveClosure* keep_alive, 1714 bool cpc): 1715 _collector(collector), 1716 _span(span), 1717 _bit_map(bit_map), 1718 _mark_stack(mark_stack), 1719 _keep_alive(keep_alive), 1720 _concurrent_precleaning(cpc) { 1721 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1722 "Mismatch"); 1723 } 1724 1725 void do_void(); 1726 }; 1727 1728 // A parallel version of CMSDrainMarkingStackClosure above. 1729 class CMSParDrainMarkingStackClosure: public VoidClosure { 1730 CMSCollector* _collector; 1731 MemRegion _span; 1732 OopTaskQueue* _work_queue; 1733 CMSBitMap* _bit_map; 1734 CMSInnerParMarkAndPushClosure _mark_and_push; 1735 1736 public: 1737 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1738 MemRegion span, CMSBitMap* bit_map, 1739 OopTaskQueue* work_queue): 1740 _collector(collector), 1741 _span(span), 1742 _bit_map(bit_map), 1743 _work_queue(work_queue), 1744 _mark_and_push(collector, span, bit_map, work_queue) { } 1745 1746 public: 1747 void trim_queue(uint max); 1748 void do_void(); 1749 }; 1750 1751 // Allow yielding or short-circuiting of reference list 1752 // precleaning work. 1753 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1754 CMSCollector* _collector; 1755 void do_yield_work(); 1756 public: 1757 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1758 _collector(collector) {} 1759 virtual bool should_return(); 1760 }; 1761 1762 1763 // Convenience class that locks free list locks for given CMS collector 1764 class FreelistLocker: public StackObj { 1765 private: 1766 CMSCollector* _collector; 1767 public: 1768 FreelistLocker(CMSCollector* collector): 1769 _collector(collector) { 1770 _collector->getFreelistLocks(); 1771 } 1772 1773 ~FreelistLocker() { 1774 _collector->releaseFreelistLocks(); 1775 } 1776 }; 1777 1778 // Mark all dead objects in a given space. 1779 class MarkDeadObjectsClosure: public BlkClosure { 1780 const CMSCollector* _collector; 1781 const CompactibleFreeListSpace* _sp; 1782 CMSBitMap* _live_bit_map; 1783 CMSBitMap* _dead_bit_map; 1784 public: 1785 MarkDeadObjectsClosure(const CMSCollector* collector, 1786 const CompactibleFreeListSpace* sp, 1787 CMSBitMap *live_bit_map, 1788 CMSBitMap *dead_bit_map) : 1789 _collector(collector), 1790 _sp(sp), 1791 _live_bit_map(live_bit_map), 1792 _dead_bit_map(dead_bit_map) {} 1793 size_t do_blk(HeapWord* addr); 1794 }; 1795 1796 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1797 1798 public: 1799 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1800 }; 1801 1802 1803 #endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP