1 /* 2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP 27 28 #include "gc_implementation/shared/gcHeapSummary.hpp" 29 #include "gc_implementation/shared/gSpaceCounters.hpp" 30 #include "gc_implementation/shared/gcStats.hpp" 31 #include "gc_implementation/shared/gcWhen.hpp" 32 #include "gc_implementation/shared/generationCounters.hpp" 33 #include "memory/cardGeneration.hpp" 34 #include "memory/freeBlockDictionary.hpp" 35 #include "memory/iterator.hpp" 36 #include "runtime/mutexLocker.hpp" 37 #include "runtime/virtualspace.hpp" 38 #include "services/memoryService.hpp" 39 #include "utilities/bitMap.inline.hpp" 40 #include "utilities/stack.inline.hpp" 41 #include "utilities/taskqueue.hpp" 42 #include "utilities/yieldingWorkgroup.hpp" 43 44 // ConcurrentMarkSweepGeneration is in support of a concurrent 45 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker 46 // style. We assume, for now, that this generation is always the 47 // seniormost generation and for simplicity 48 // in the first implementation, that this generation is a single compactible 49 // space. Neither of these restrictions appears essential, and will be 50 // relaxed in the future when more time is available to implement the 51 // greater generality (and there's a need for it). 52 // 53 // Concurrent mode failures are currently handled by 54 // means of a sliding mark-compact. 55 56 class AdaptiveSizePolicy; 57 class CMSConcMarkingTask; 58 class CMSGCAdaptivePolicyCounters; 59 class CMSTracer; 60 class ConcurrentGCTimer; 61 class ConcurrentMarkSweepGeneration; 62 class ConcurrentMarkSweepPolicy; 63 class ConcurrentMarkSweepThread; 64 class CompactibleFreeListSpace; 65 class FreeChunk; 66 class PromotionInfo; 67 class ScanMarkedObjectsAgainCarefullyClosure; 68 class TenuredGeneration; 69 class SerialOldTracer; 70 71 // A generic CMS bit map. It's the basis for both the CMS marking bit map 72 // as well as for the mod union table (in each case only a subset of the 73 // methods are used). This is essentially a wrapper around the BitMap class, 74 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map, 75 // we have _shifter == 0. and for the mod union table we have 76 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.) 77 // XXX 64-bit issues in BitMap? 78 class CMSBitMap VALUE_OBJ_CLASS_SPEC { 79 friend class VMStructs; 80 81 HeapWord* _bmStartWord; // base address of range covered by map 82 size_t _bmWordSize; // map size (in #HeapWords covered) 83 const int _shifter; // shifts to convert HeapWord to bit position 84 VirtualSpace _virtual_space; // underlying the bit map 85 BitMap _bm; // the bit map itself 86 public: 87 Mutex* const _lock; // mutex protecting _bm; 88 89 public: 90 // constructor 91 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 92 93 // allocates the actual storage for the map 94 bool allocate(MemRegion mr); 95 // field getter 96 Mutex* lock() const { return _lock; } 97 // locking verifier convenience function 98 void assert_locked() const PRODUCT_RETURN; 99 100 // inquiries 101 HeapWord* startWord() const { return _bmStartWord; } 102 size_t sizeInWords() const { return _bmWordSize; } 103 size_t sizeInBits() const { return _bm.size(); } 104 // the following is one past the last word in space 105 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 106 107 // reading marks 108 bool isMarked(HeapWord* addr) const; 109 bool par_isMarked(HeapWord* addr) const; // do not lock checks 110 bool isUnmarked(HeapWord* addr) const; 111 bool isAllClear() const; 112 113 // writing marks 114 void mark(HeapWord* addr); 115 // For marking by parallel GC threads; 116 // returns true if we did, false if another thread did 117 bool par_mark(HeapWord* addr); 118 119 void mark_range(MemRegion mr); 120 void par_mark_range(MemRegion mr); 121 void mark_large_range(MemRegion mr); 122 void par_mark_large_range(MemRegion mr); 123 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 124 void clear_range(MemRegion mr); 125 void par_clear_range(MemRegion mr); 126 void clear_large_range(MemRegion mr); 127 void par_clear_large_range(MemRegion mr); 128 void clear_all(); 129 void clear_all_incrementally(); // Not yet implemented!! 130 131 NOT_PRODUCT( 132 // checks the memory region for validity 133 void region_invariant(MemRegion mr); 134 ) 135 136 // iteration 137 void iterate(BitMapClosure* cl) { 138 _bm.iterate(cl); 139 } 140 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 141 void dirty_range_iterate_clear(MemRegionClosure* cl); 142 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 143 144 // auxiliary support for iteration 145 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 146 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 147 HeapWord* end_addr) const; 148 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 149 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 150 HeapWord* end_addr) const; 151 MemRegion getAndClearMarkedRegion(HeapWord* addr); 152 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 153 HeapWord* end_addr); 154 155 // conversion utilities 156 HeapWord* offsetToHeapWord(size_t offset) const; 157 size_t heapWordToOffset(HeapWord* addr) const; 158 size_t heapWordDiffToOffsetDiff(size_t diff) const; 159 160 void print_on_error(outputStream* st, const char* prefix) const; 161 162 // debugging 163 // is this address range covered by the bit-map? 164 NOT_PRODUCT( 165 bool covers(MemRegion mr) const; 166 bool covers(HeapWord* start, size_t size = 0) const; 167 ) 168 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 169 }; 170 171 // Represents a marking stack used by the CMS collector. 172 // Ideally this should be GrowableArray<> just like MSC's marking stack(s). 173 class CMSMarkStack: public CHeapObj<mtGC> { 174 // 175 friend class CMSCollector; // To get at expansion stats further below. 176 // 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 _hit_limit(0), 193 _failed_double(0) {} 194 195 bool allocate(size_t size); 196 197 size_t capacity() const { return _capacity; } 198 199 oop pop() { 200 if (!isEmpty()) { 201 return _base[--_index] ; 202 } 203 return NULL; 204 } 205 206 bool push(oop ptr) { 207 if (isFull()) { 208 return false; 209 } else { 210 _base[_index++] = ptr; 211 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 212 return true; 213 } 214 } 215 216 bool isEmpty() const { return _index == 0; } 217 bool isFull() const { 218 assert(_index <= _capacity, "buffer overflow"); 219 return _index == _capacity; 220 } 221 222 size_t length() { return _index; } 223 224 // "Parallel versions" of some of the above 225 oop par_pop() { 226 // lock and pop 227 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 228 return pop(); 229 } 230 231 bool par_push(oop ptr) { 232 // lock and push 233 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 234 return push(ptr); 235 } 236 237 // Forcibly reset the stack, losing all of its contents. 238 void reset() { 239 _index = 0; 240 } 241 242 // Expand the stack, typically in response to an overflow condition. 243 void expand(); 244 245 // Compute the least valued stack element. 246 oop least_value(HeapWord* low) { 247 oop least = (oop)low; 248 for (size_t i = 0; i < _index; i++) { 249 least = MIN2(least, _base[i]); 250 } 251 return least; 252 } 253 254 // Exposed here to allow stack expansion in || case. 255 Mutex* par_lock() { return &_par_lock; } 256 }; 257 258 class CardTableRS; 259 class CMSParGCThreadState; 260 261 class ModUnionClosure: public MemRegionClosure { 262 protected: 263 CMSBitMap* _t; 264 public: 265 ModUnionClosure(CMSBitMap* t): _t(t) { } 266 void do_MemRegion(MemRegion mr); 267 }; 268 269 class ModUnionClosurePar: public ModUnionClosure { 270 public: 271 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 272 void do_MemRegion(MemRegion mr); 273 }; 274 275 // Survivor Chunk Array in support of parallelization of 276 // Survivor Space rescan. 277 class ChunkArray: public CHeapObj<mtGC> { 278 size_t _index; 279 size_t _capacity; 280 size_t _overflows; 281 HeapWord** _array; // storage for array 282 283 public: 284 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 285 ChunkArray(HeapWord** a, size_t c): 286 _index(0), _capacity(c), _overflows(0), _array(a) {} 287 288 HeapWord** array() { return _array; } 289 void set_array(HeapWord** a) { _array = a; } 290 291 size_t capacity() { return _capacity; } 292 void set_capacity(size_t c) { _capacity = c; } 293 294 size_t end() { 295 assert(_index <= capacity(), 296 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 297 _index, _capacity)); 298 return _index; 299 } // exclusive 300 301 HeapWord* nth(size_t n) { 302 assert(n < end(), "Out of bounds access"); 303 return _array[n]; 304 } 305 306 void reset() { 307 _index = 0; 308 if (_overflows > 0 && PrintCMSStatistics > 1) { 309 warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", 310 _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 err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 323 "): out of bounds at overflow#" SIZE_FORMAT, 324 _index, _capacity, _overflows)); 325 } 326 } 327 }; 328 329 // 330 // Timing, allocation and promotion statistics for gc scheduling and incremental 331 // mode pacing. Most statistics are exponential averages. 332 // 333 class CMSStats VALUE_OBJ_CLASS_SPEC { 334 private: 335 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 336 337 // The following are exponential averages with factor alpha: 338 // avg = (100 - alpha) * avg + alpha * cur_sample 339 // 340 // The durations measure: end_time[n] - start_time[n] 341 // The periods measure: start_time[n] - start_time[n-1] 342 // 343 // The cms period and duration include only concurrent collections; time spent 344 // in foreground cms collections due to System.gc() or because of a failure to 345 // keep up are not included. 346 // 347 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 348 // real value, but is used only after the first period. A value of 100 is 349 // used for the first sample so it gets the entire weight. 350 unsigned int _saved_alpha; // 0-100 351 unsigned int _gc0_alpha; 352 unsigned int _cms_alpha; 353 354 double _gc0_duration; 355 double _gc0_period; 356 size_t _gc0_promoted; // bytes promoted per gc0 357 double _cms_duration; 358 double _cms_duration_pre_sweep; // time from initiation to start of sweep 359 double _cms_period; 360 size_t _cms_allocated; // bytes of direct allocation per gc0 period 361 362 // Timers. 363 elapsedTimer _cms_timer; 364 TimeStamp _gc0_begin_time; 365 TimeStamp _cms_begin_time; 366 TimeStamp _cms_end_time; 367 368 // Snapshots of the amount used in the CMS generation. 369 size_t _cms_used_at_gc0_begin; 370 size_t _cms_used_at_gc0_end; 371 size_t _cms_used_at_cms_begin; 372 373 // Used to prevent the duty cycle from being reduced in the middle of a cms 374 // cycle. 375 bool _allow_duty_cycle_reduction; 376 377 enum { 378 _GC0_VALID = 0x1, 379 _CMS_VALID = 0x2, 380 _ALL_VALID = _GC0_VALID | _CMS_VALID 381 }; 382 383 unsigned int _valid_bits; 384 385 protected: 386 // In support of adjusting of cms trigger ratios based on history 387 // of concurrent mode failure. 388 double cms_free_adjustment_factor(size_t free) const; 389 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 390 391 public: 392 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 393 unsigned int alpha = CMSExpAvgFactor); 394 395 // Whether or not the statistics contain valid data; higher level statistics 396 // cannot be called until this returns true (they require at least one young 397 // gen and one cms cycle to have completed). 398 bool valid() const; 399 400 // Record statistics. 401 void record_gc0_begin(); 402 void record_gc0_end(size_t cms_gen_bytes_used); 403 void record_cms_begin(); 404 void record_cms_end(); 405 406 // Allow management of the cms timer, which must be stopped/started around 407 // yield points. 408 elapsedTimer& cms_timer() { return _cms_timer; } 409 void start_cms_timer() { _cms_timer.start(); } 410 void stop_cms_timer() { _cms_timer.stop(); } 411 412 // Basic statistics; units are seconds or bytes. 413 double gc0_period() const { return _gc0_period; } 414 double gc0_duration() const { return _gc0_duration; } 415 size_t gc0_promoted() const { return _gc0_promoted; } 416 double cms_period() const { return _cms_period; } 417 double cms_duration() const { return _cms_duration; } 418 size_t cms_allocated() const { return _cms_allocated; } 419 420 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 421 422 // Seconds since the last background cms cycle began or ended. 423 double cms_time_since_begin() const; 424 double cms_time_since_end() const; 425 426 // Higher level statistics--caller must check that valid() returns true before 427 // calling. 428 429 // Returns bytes promoted per second of wall clock time. 430 double promotion_rate() const; 431 432 // Returns bytes directly allocated per second of wall clock time. 433 double cms_allocation_rate() const; 434 435 // Rate at which space in the cms generation is being consumed (sum of the 436 // above two). 437 double cms_consumption_rate() const; 438 439 // Returns an estimate of the number of seconds until the cms generation will 440 // fill up, assuming no collection work is done. 441 double time_until_cms_gen_full() const; 442 443 // Returns an estimate of the number of seconds remaining until 444 // the cms generation collection should start. 445 double time_until_cms_start() const; 446 447 // End of higher level statistics. 448 449 // Debugging. 450 void print_on(outputStream* st) const PRODUCT_RETURN; 451 void print() const { print_on(gclog_or_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 Par_PushOrMarkClosure; // to access _restart_addr 511 friend class MarkFromRootsClosure; // -- ditto -- 512 // ... and for clearing cards 513 friend class Par_MarkFromRootsClosure; // to access _restart_addr 514 // ... and for clearing cards 515 friend class Par_ConcMarkingClosure; // 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 Par_PushAndMarkClosure; // -- 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 oop _overflow_list; 542 // The following array-pair keeps track of mark words 543 // displaced for accommodating overflow list above. 544 // This code will likely be revisited under RFE#4922830. 545 Stack<oop, mtGC> _preserved_oop_stack; 546 Stack<markOop, mtGC> _preserved_mark_stack; 547 548 int* _hash_seed; 549 550 // In support of multi-threaded concurrent phases 551 YieldingFlexibleWorkGang* _conc_workers; 552 553 // Performance Counters 554 CollectorCounters* _gc_counters; 555 556 // Initialization Errors 557 bool _completed_initialization; 558 559 // In support of ExplicitGCInvokesConcurrent 560 static bool _full_gc_requested; 561 static GCCause::Cause _full_gc_cause; 562 unsigned int _collection_count_start; 563 564 // Should we unload classes this concurrent cycle? 565 bool _should_unload_classes; 566 unsigned int _concurrent_cycles_since_last_unload; 567 unsigned int concurrent_cycles_since_last_unload() const { 568 return _concurrent_cycles_since_last_unload; 569 } 570 // Did we (allow) unload classes in the previous concurrent cycle? 571 bool unloaded_classes_last_cycle() const { 572 return concurrent_cycles_since_last_unload() == 0; 573 } 574 // Root scanning options for perm gen 575 int _roots_scanning_options; 576 int roots_scanning_options() const { return _roots_scanning_options; } 577 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 578 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 579 580 // Verification support 581 CMSBitMap _verification_mark_bm; 582 void verify_after_remark_work_1(); 583 void verify_after_remark_work_2(); 584 585 // True if any verification flag is on. 586 bool _verifying; 587 bool verifying() const { return _verifying; } 588 void set_verifying(bool v) { _verifying = v; } 589 590 // Collector policy 591 ConcurrentMarkSweepPolicy* _collector_policy; 592 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 593 594 void set_did_compact(bool v); 595 596 // XXX Move these to CMSStats ??? FIX ME !!! 597 elapsedTimer _inter_sweep_timer; // Time between sweeps 598 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 599 // Padded decaying average estimates of the above 600 AdaptivePaddedAverage _inter_sweep_estimate; 601 AdaptivePaddedAverage _intra_sweep_estimate; 602 603 CMSTracer* _gc_tracer_cm; 604 ConcurrentGCTimer* _gc_timer_cm; 605 606 bool _cms_start_registered; 607 608 GCHeapSummary _last_heap_summary; 609 MetaspaceSummary _last_metaspace_summary; 610 611 void register_gc_start(GCCause::Cause cause); 612 void register_gc_end(); 613 void save_heap_summary(); 614 void report_heap_summary(GCWhen::Type when); 615 616 protected: 617 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 618 MemRegion _span; // Span covering above two 619 CardTableRS* _ct; // Card table 620 621 // CMS marking support structures 622 CMSBitMap _markBitMap; 623 CMSBitMap _modUnionTable; 624 CMSMarkStack _markStack; 625 626 HeapWord* _restart_addr; // In support of marking stack overflow 627 void lower_restart_addr(HeapWord* low); 628 629 // Counters in support of marking stack / work queue overflow handling: 630 // a non-zero value indicates certain types of overflow events during 631 // the current CMS cycle and could lead to stack resizing efforts at 632 // an opportune future time. 633 size_t _ser_pmc_preclean_ovflw; 634 size_t _ser_pmc_remark_ovflw; 635 size_t _par_pmc_remark_ovflw; 636 size_t _ser_kac_preclean_ovflw; 637 size_t _ser_kac_ovflw; 638 size_t _par_kac_ovflw; 639 NOT_PRODUCT(ssize_t _num_par_pushes;) 640 641 // ("Weak") Reference processing support. 642 ReferenceProcessor* _ref_processor; 643 CMSIsAliveClosure _is_alive_closure; 644 // Keep this textually after _markBitMap and _span; c'tor dependency. 645 646 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 647 ModUnionClosure _modUnionClosure; 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; // the younger gen 725 726 HeapWord** _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* gen, 774 ScanMarkedObjectsAgainCarefullyClosure* cl); 775 size_t preclean_card_table(ConcurrentMarkSweepGeneration* 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_klasses(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* gen); 799 800 // (Concurrent) resetting of support data structures 801 void reset(bool concurrent); 802 803 // Clear _expansion_cause fields of constituent generations 804 void clear_expansion_cause(); 805 806 // An auxiliary method used to record the ends of 807 // used regions of each generation to limit the extent of sweep 808 void save_sweep_limits(); 809 810 // A work method used by the foreground collector to do 811 // a mark-sweep-compact. 812 void do_compaction_work(bool clear_all_soft_refs); 813 814 // Work methods for reporting concurrent mode interruption or failure 815 bool is_external_interruption(); 816 void report_concurrent_mode_interruption(); 817 818 // If the background GC is active, acquire control from the background 819 // GC and do the collection. 820 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 821 822 // For synchronizing passing of control from background to foreground 823 // GC. waitForForegroundGC() is called by the background 824 // collector. It if had to wait for a foreground collection, 825 // it returns true and the background collection should assume 826 // that the collection was finished by the foreground 827 // collector. 828 bool waitForForegroundGC(); 829 830 size_t block_size_using_printezis_bits(HeapWord* addr) const; 831 size_t block_size_if_printezis_bits(HeapWord* addr) const; 832 HeapWord* next_card_start_after_block(HeapWord* addr) const; 833 834 void setup_cms_unloading_and_verification_state(); 835 public: 836 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 837 CardTableRS* ct, 838 ConcurrentMarkSweepPolicy* cp); 839 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 840 841 ReferenceProcessor* ref_processor() { return _ref_processor; } 842 void ref_processor_init(); 843 844 Mutex* bitMapLock() const { return _markBitMap.lock(); } 845 static CollectorState abstract_state() { return _collectorState; } 846 847 bool should_abort_preclean() const; // Whether preclean should be aborted. 848 size_t get_eden_used() const; 849 size_t get_eden_capacity() const; 850 851 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 852 853 // Locking checks 854 NOT_PRODUCT(static bool have_cms_token();) 855 856 bool shouldConcurrentCollect(); 857 858 void collect(bool full, 859 bool clear_all_soft_refs, 860 size_t size, 861 bool tlab); 862 void collect_in_background(GCCause::Cause cause); 863 864 // In support of ExplicitGCInvokesConcurrent 865 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 866 // Should we unload classes in a particular concurrent cycle? 867 bool should_unload_classes() const { 868 return _should_unload_classes; 869 } 870 void update_should_unload_classes(); 871 872 void direct_allocated(HeapWord* start, size_t size); 873 874 // Object is dead if not marked and current phase is sweeping. 875 bool is_dead_obj(oop obj) const; 876 877 // After a promotion (of "start"), do any necessary marking. 878 // If "par", then it's being done by a parallel GC thread. 879 // The last two args indicate if we need precise marking 880 // and if so the size of the object so it can be dirtied 881 // in its entirety. 882 void promoted(bool par, HeapWord* start, 883 bool is_obj_array, size_t obj_size); 884 885 void getFreelistLocks() const; 886 void releaseFreelistLocks() const; 887 bool haveFreelistLocks() const; 888 889 // Adjust size of underlying generation 890 void compute_new_size(); 891 892 // GC prologue and epilogue 893 void gc_prologue(bool full); 894 void gc_epilogue(bool full); 895 896 jlong time_of_last_gc(jlong now) { 897 if (_collectorState <= Idling) { 898 // gc not in progress 899 return _time_of_last_gc; 900 } else { 901 // collection in progress 902 return now; 903 } 904 } 905 906 // Support for parallel remark of survivor space 907 void* get_data_recorder(int thr_num); 908 void sample_eden_chunk(); 909 910 CMSBitMap* markBitMap() { return &_markBitMap; } 911 void directAllocated(HeapWord* start, size_t size); 912 913 // Main CMS steps and related support 914 void checkpointRootsInitial(); 915 bool markFromRoots(); // a return value of false indicates failure 916 // due to stack overflow 917 void preclean(); 918 void checkpointRootsFinal(); 919 void sweep(); 920 921 // Check that the currently executing thread is the expected 922 // one (foreground collector or background collector). 923 static void check_correct_thread_executing() PRODUCT_RETURN; 924 925 bool is_cms_reachable(HeapWord* addr); 926 927 // Performance Counter Support 928 CollectorCounters* counters() { return _gc_counters; } 929 930 // Timer stuff 931 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 932 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 933 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 934 double timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); } 935 936 int yields() { return _numYields; } 937 void resetYields() { _numYields = 0; } 938 void incrementYields() { _numYields++; } 939 void resetNumDirtyCards() { _numDirtyCards = 0; } 940 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 941 size_t numDirtyCards() { return _numDirtyCards; } 942 943 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 944 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 945 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 946 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 947 size_t sweep_count() const { return _sweep_count; } 948 void increment_sweep_count() { _sweep_count++; } 949 950 // Timers/stats for gc scheduling and incremental mode pacing. 951 CMSStats& stats() { return _stats; } 952 953 // Adaptive size policy 954 AdaptiveSizePolicy* size_policy(); 955 956 static void print_on_error(outputStream* st); 957 958 // Debugging 959 void verify(); 960 bool verify_after_remark(bool silent = VerifySilently); 961 void verify_ok_to_terminate() const PRODUCT_RETURN; 962 void verify_work_stacks_empty() const PRODUCT_RETURN; 963 void verify_overflow_empty() const PRODUCT_RETURN; 964 965 // Convenience methods in support of debugging 966 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 967 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 968 969 // Accessors 970 CMSMarkStack* verification_mark_stack() { return &_markStack; } 971 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 972 973 // Initialization errors 974 bool completed_initialization() { return _completed_initialization; } 975 976 void print_eden_and_survivor_chunk_arrays(); 977 }; 978 979 class CMSExpansionCause : public AllStatic { 980 public: 981 enum Cause { 982 _no_expansion, 983 _satisfy_free_ratio, 984 _satisfy_promotion, 985 _satisfy_allocation, 986 _allocate_par_lab, 987 _allocate_par_spooling_space, 988 _adaptive_size_policy 989 }; 990 // Return a string describing the cause of the expansion. 991 static const char* to_string(CMSExpansionCause::Cause cause); 992 }; 993 994 class ConcurrentMarkSweepGeneration: public CardGeneration { 995 friend class VMStructs; 996 friend class ConcurrentMarkSweepThread; 997 friend class ConcurrentMarkSweep; 998 friend class CMSCollector; 999 protected: 1000 static CMSCollector* _collector; // the collector that collects us 1001 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1002 1003 // Performance Counters 1004 GenerationCounters* _gen_counters; 1005 GSpaceCounters* _space_counters; 1006 1007 // Words directly allocated, used by CMSStats. 1008 size_t _direct_allocated_words; 1009 1010 // Non-product stat counters 1011 NOT_PRODUCT( 1012 size_t _numObjectsPromoted; 1013 size_t _numWordsPromoted; 1014 size_t _numObjectsAllocated; 1015 size_t _numWordsAllocated; 1016 ) 1017 1018 // Used for sizing decisions 1019 bool _incremental_collection_failed; 1020 bool incremental_collection_failed() { 1021 return _incremental_collection_failed; 1022 } 1023 void set_incremental_collection_failed() { 1024 _incremental_collection_failed = true; 1025 } 1026 void clear_incremental_collection_failed() { 1027 _incremental_collection_failed = false; 1028 } 1029 1030 // accessors 1031 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1032 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1033 1034 private: 1035 // For parallel young-gen GC support. 1036 CMSParGCThreadState** _par_gc_thread_states; 1037 1038 // Reason generation was expanded 1039 CMSExpansionCause::Cause _expansion_cause; 1040 1041 // In support of MinChunkSize being larger than min object size 1042 const double _dilatation_factor; 1043 1044 // True if a compacting collection was done. 1045 bool _did_compact; 1046 bool did_compact() { return _did_compact; } 1047 1048 // Fraction of current occupancy at which to start a CMS collection which 1049 // will collect this generation (at least). 1050 double _initiating_occupancy; 1051 1052 protected: 1053 // Shrink generation by specified size (returns false if unable to shrink) 1054 void shrink_free_list_by(size_t bytes); 1055 1056 // Update statistics for GC 1057 virtual void update_gc_stats(int level, bool full); 1058 1059 // Maximum available space in the generation (including uncommitted) 1060 // space. 1061 size_t max_available() const; 1062 1063 // getter and initializer for _initiating_occupancy field. 1064 double initiating_occupancy() const { return _initiating_occupancy; } 1065 void init_initiating_occupancy(intx io, uintx tr); 1066 1067 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1068 1069 public: 1070 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, 1071 int level, CardTableRS* ct, 1072 bool use_adaptive_freelists, 1073 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 1074 1075 // Accessors 1076 CMSCollector* collector() const { return _collector; } 1077 static void set_collector(CMSCollector* collector) { 1078 assert(_collector == NULL, "already set"); 1079 _collector = collector; 1080 } 1081 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1082 1083 Mutex* freelistLock() const; 1084 1085 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1086 1087 void set_did_compact(bool v) { _did_compact = v; } 1088 1089 bool refs_discovery_is_atomic() const { return false; } 1090 bool refs_discovery_is_mt() const { 1091 // Note: CMS does MT-discovery during the parallel-remark 1092 // phases. Use ReferenceProcessorMTMutator to make refs 1093 // discovery MT-safe during such phases or other parallel 1094 // discovery phases in the future. This may all go away 1095 // if/when we decide that refs discovery is sufficiently 1096 // rare that the cost of the CAS's involved is in the 1097 // noise. That's a measurement that should be done, and 1098 // the code simplified if that turns out to be the case. 1099 return ConcGCThreads > 1; 1100 } 1101 1102 // Override 1103 virtual void ref_processor_init(); 1104 1105 // Grow generation by specified size (returns false if unable to grow) 1106 bool grow_by(size_t bytes); 1107 // Grow generation to reserved size. 1108 bool grow_to_reserved(); 1109 1110 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1111 1112 // Space enquiries 1113 size_t capacity() const; 1114 size_t used() const; 1115 size_t free() const; 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() const; 1122 MemRegion used_region_at_save_marks() const; 1123 1124 // Does a "full" (forced) collection invoked on this generation collect 1125 // all younger generations as well? Note that the second conjunct is a 1126 // hack to allow the collection of the younger gen first if the flag is 1127 // set. 1128 virtual bool full_collects_younger_generations() const { 1129 return !ScavengeBeforeFullGC; 1130 } 1131 1132 void space_iterate(SpaceClosure* blk, bool usedOnly = false); 1133 1134 // Support for compaction 1135 CompactibleSpace* first_compaction_space() const; 1136 // Adjust quantities in the generation affected by 1137 // the compaction. 1138 void reset_after_compaction(); 1139 1140 // Allocation support 1141 HeapWord* allocate(size_t size, bool tlab); 1142 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1143 oop promote(oop obj, size_t obj_size); 1144 HeapWord* par_allocate(size_t size, bool tlab) { 1145 return allocate(size, tlab); 1146 } 1147 1148 1149 // Used by CMSStats to track direct allocation. The value is sampled and 1150 // reset after each young gen collection. 1151 size_t direct_allocated_words() const { return _direct_allocated_words; } 1152 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1153 1154 // Overrides for parallel promotion. 1155 virtual oop par_promote(int thread_num, 1156 oop obj, markOop m, size_t word_sz); 1157 virtual void par_promote_alloc_done(int thread_num); 1158 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1159 1160 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1161 1162 // Inform this (non-young) generation that a promotion failure was 1163 // encountered during a collection of a younger generation that 1164 // promotes into this generation. 1165 virtual void promotion_failure_occurred(); 1166 1167 bool should_collect(bool full, size_t size, bool tlab); 1168 virtual bool should_concurrent_collect() const; 1169 virtual bool is_too_full() const; 1170 void collect(bool full, 1171 bool clear_all_soft_refs, 1172 size_t size, 1173 bool tlab); 1174 1175 HeapWord* expand_and_allocate(size_t word_size, 1176 bool tlab, 1177 bool parallel = false); 1178 1179 // GC prologue and epilogue 1180 void gc_prologue(bool full); 1181 void gc_prologue_work(bool full, bool registerClosure, 1182 ModUnionClosure* modUnionClosure); 1183 void gc_epilogue(bool full); 1184 void gc_epilogue_work(bool full); 1185 1186 // Time since last GC of this generation 1187 jlong time_of_last_gc(jlong now) { 1188 return collector()->time_of_last_gc(now); 1189 } 1190 void update_time_of_last_gc(jlong now) { 1191 collector()-> update_time_of_last_gc(now); 1192 } 1193 1194 // Allocation failure 1195 virtual bool expand(size_t bytes, size_t expand_bytes); 1196 void shrink(size_t bytes); 1197 void shrink_by(size_t bytes); 1198 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1199 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1200 1201 // Iteration support and related enquiries 1202 void save_marks(); 1203 bool no_allocs_since_save_marks(); 1204 void younger_refs_iterate(OopsInGenClosure* cl); 1205 1206 // Iteration support specific to CMS generations 1207 void save_sweep_limit(); 1208 1209 // More iteration support 1210 virtual void oop_iterate(ExtendedOopClosure* cl); 1211 virtual void safe_object_iterate(ObjectClosure* cl); 1212 virtual void object_iterate(ObjectClosure* cl); 1213 1214 // Need to declare the full complement of closures, whether we'll 1215 // override them or not, or get message from the compiler: 1216 // oop_since_save_marks_iterate_nv hides virtual function... 1217 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1218 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1219 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1220 1221 // Smart allocation XXX -- move to CFLSpace? 1222 void setNearLargestChunk(); 1223 bool isNearLargestChunk(HeapWord* addr); 1224 1225 // Get the chunk at the end of the space. Delegates to 1226 // the space. 1227 FreeChunk* find_chunk_at_end(); 1228 1229 void post_compact(); 1230 1231 // Debugging 1232 void prepare_for_verify(); 1233 void verify(); 1234 void print_statistics() PRODUCT_RETURN; 1235 1236 // Performance Counters support 1237 virtual void update_counters(); 1238 virtual void update_counters(size_t used); 1239 void initialize_performance_counters(); 1240 CollectorCounters* counters() { return collector()->counters(); } 1241 1242 // Support for parallel remark of survivor space 1243 void* get_data_recorder(int thr_num) { 1244 //Delegate to collector 1245 return collector()->get_data_recorder(thr_num); 1246 } 1247 void sample_eden_chunk() { 1248 //Delegate to collector 1249 return collector()->sample_eden_chunk(); 1250 } 1251 1252 // Printing 1253 const char* name() const; 1254 virtual const char* short_name() const { return "CMS"; } 1255 void print() const; 1256 void printOccupancy(const char* s); 1257 1258 // Resize the generation after a compacting GC. The 1259 // generation can be treated as a contiguous space 1260 // after the compaction. 1261 virtual void compute_new_size(); 1262 // Resize the generation after a non-compacting 1263 // collection. 1264 void compute_new_size_free_list(); 1265 }; 1266 1267 // 1268 // Closures of various sorts used by CMS to accomplish its work 1269 // 1270 1271 // This closure is used to do concurrent marking from the roots 1272 // following the first checkpoint. 1273 class MarkFromRootsClosure: public BitMapClosure { 1274 CMSCollector* _collector; 1275 MemRegion _span; 1276 CMSBitMap* _bitMap; 1277 CMSBitMap* _mut; 1278 CMSMarkStack* _markStack; 1279 bool _yield; 1280 int _skipBits; 1281 HeapWord* _finger; 1282 HeapWord* _threshold; 1283 DEBUG_ONLY(bool _verifying;) 1284 1285 public: 1286 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1287 CMSBitMap* bitMap, 1288 CMSMarkStack* markStack, 1289 bool should_yield, bool verifying = false); 1290 bool do_bit(size_t offset); 1291 void reset(HeapWord* addr); 1292 inline void do_yield_check(); 1293 1294 private: 1295 void scanOopsInOop(HeapWord* ptr); 1296 void do_yield_work(); 1297 }; 1298 1299 // This closure is used to do concurrent multi-threaded 1300 // marking from the roots following the first checkpoint. 1301 // XXX This should really be a subclass of The serial version 1302 // above, but i have not had the time to refactor things cleanly. 1303 class Par_MarkFromRootsClosure: public BitMapClosure { 1304 CMSCollector* _collector; 1305 MemRegion _whole_span; 1306 MemRegion _span; 1307 CMSBitMap* _bit_map; 1308 CMSBitMap* _mut; 1309 OopTaskQueue* _work_queue; 1310 CMSMarkStack* _overflow_stack; 1311 int _skip_bits; 1312 HeapWord* _finger; 1313 HeapWord* _threshold; 1314 CMSConcMarkingTask* _task; 1315 public: 1316 Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1317 MemRegion span, 1318 CMSBitMap* bit_map, 1319 OopTaskQueue* work_queue, 1320 CMSMarkStack* overflow_stack); 1321 bool do_bit(size_t offset); 1322 inline void do_yield_check(); 1323 1324 private: 1325 void scan_oops_in_oop(HeapWord* ptr); 1326 void do_yield_work(); 1327 bool get_work_from_overflow_stack(); 1328 }; 1329 1330 // The following closures are used to do certain kinds of verification of 1331 // CMS marking. 1332 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1333 CMSCollector* _collector; 1334 MemRegion _span; 1335 CMSBitMap* _verification_bm; 1336 CMSBitMap* _cms_bm; 1337 CMSMarkStack* _mark_stack; 1338 protected: 1339 void do_oop(oop p); 1340 template <class T> inline void do_oop_work(T *p) { 1341 oop obj = oopDesc::load_decode_heap_oop(p); 1342 do_oop(obj); 1343 } 1344 public: 1345 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1346 MemRegion span, 1347 CMSBitMap* verification_bm, 1348 CMSBitMap* cms_bm, 1349 CMSMarkStack* mark_stack); 1350 void do_oop(oop* p); 1351 void do_oop(narrowOop* p); 1352 1353 // Deal with a stack overflow condition 1354 void handle_stack_overflow(HeapWord* lost); 1355 }; 1356 1357 class MarkFromRootsVerifyClosure: public BitMapClosure { 1358 CMSCollector* _collector; 1359 MemRegion _span; 1360 CMSBitMap* _verification_bm; 1361 CMSBitMap* _cms_bm; 1362 CMSMarkStack* _mark_stack; 1363 HeapWord* _finger; 1364 PushAndMarkVerifyClosure _pam_verify_closure; 1365 public: 1366 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1367 CMSBitMap* verification_bm, 1368 CMSBitMap* cms_bm, 1369 CMSMarkStack* mark_stack); 1370 bool do_bit(size_t offset); 1371 void reset(HeapWord* addr); 1372 }; 1373 1374 1375 // This closure is used to check that a certain set of bits is 1376 // "empty" (i.e. the bit vector doesn't have any 1-bits). 1377 class FalseBitMapClosure: public BitMapClosure { 1378 public: 1379 bool do_bit(size_t offset) { 1380 guarantee(false, "Should not have a 1 bit"); 1381 return true; 1382 } 1383 }; 1384 1385 // A version of ObjectClosure with "memory" (see _previous_address below) 1386 class UpwardsObjectClosure: public BoolObjectClosure { 1387 HeapWord* _previous_address; 1388 public: 1389 UpwardsObjectClosure() : _previous_address(NULL) { } 1390 void set_previous(HeapWord* addr) { _previous_address = addr; } 1391 HeapWord* previous() { return _previous_address; } 1392 // A return value of "true" can be used by the caller to decide 1393 // if this object's end should *NOT* be recorded in 1394 // _previous_address above. 1395 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1396 }; 1397 1398 // This closure is used during the second checkpointing phase 1399 // to rescan the marked objects on the dirty cards in the mod 1400 // union table and the card table proper. It's invoked via 1401 // MarkFromDirtyCardsClosure below. It uses either 1402 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1403 // declared in genOopClosures.hpp to accomplish some of its work. 1404 // In the parallel case the bitMap is shared, so access to 1405 // it needs to be suitably synchronized for updates by embedded 1406 // closures that update it; however, this closure itself only 1407 // reads the bit_map and because it is idempotent, is immune to 1408 // reading stale values. 1409 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1410 #ifdef ASSERT 1411 CMSCollector* _collector; 1412 MemRegion _span; 1413 union { 1414 CMSMarkStack* _mark_stack; 1415 OopTaskQueue* _work_queue; 1416 }; 1417 #endif // ASSERT 1418 bool _parallel; 1419 CMSBitMap* _bit_map; 1420 union { 1421 MarkRefsIntoAndScanClosure* _scan_closure; 1422 Par_MarkRefsIntoAndScanClosure* _par_scan_closure; 1423 }; 1424 1425 public: 1426 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1427 MemRegion span, 1428 ReferenceProcessor* rp, 1429 CMSBitMap* bit_map, 1430 CMSMarkStack* mark_stack, 1431 MarkRefsIntoAndScanClosure* cl): 1432 #ifdef ASSERT 1433 _collector(collector), 1434 _span(span), 1435 _mark_stack(mark_stack), 1436 #endif // ASSERT 1437 _parallel(false), 1438 _bit_map(bit_map), 1439 _scan_closure(cl) { } 1440 1441 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1442 MemRegion span, 1443 ReferenceProcessor* rp, 1444 CMSBitMap* bit_map, 1445 OopTaskQueue* work_queue, 1446 Par_MarkRefsIntoAndScanClosure* cl): 1447 #ifdef ASSERT 1448 _collector(collector), 1449 _span(span), 1450 _work_queue(work_queue), 1451 #endif // ASSERT 1452 _parallel(true), 1453 _bit_map(bit_map), 1454 _par_scan_closure(cl) { } 1455 1456 bool do_object_b(oop obj) { 1457 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1458 return false; 1459 } 1460 bool do_object_bm(oop p, MemRegion mr); 1461 }; 1462 1463 // This closure is used during the second checkpointing phase 1464 // to rescan the marked objects on the dirty cards in the mod 1465 // union table and the card table proper. It invokes 1466 // ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1467 // In the parallel case, the bit map is shared and requires 1468 // synchronized access. 1469 class MarkFromDirtyCardsClosure: public MemRegionClosure { 1470 CompactibleFreeListSpace* _space; 1471 ScanMarkedObjectsAgainClosure _scan_cl; 1472 size_t _num_dirty_cards; 1473 1474 public: 1475 MarkFromDirtyCardsClosure(CMSCollector* collector, 1476 MemRegion span, 1477 CompactibleFreeListSpace* space, 1478 CMSBitMap* bit_map, 1479 CMSMarkStack* mark_stack, 1480 MarkRefsIntoAndScanClosure* cl): 1481 _space(space), 1482 _num_dirty_cards(0), 1483 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1484 mark_stack, cl) { } 1485 1486 MarkFromDirtyCardsClosure(CMSCollector* collector, 1487 MemRegion span, 1488 CompactibleFreeListSpace* space, 1489 CMSBitMap* bit_map, 1490 OopTaskQueue* work_queue, 1491 Par_MarkRefsIntoAndScanClosure* cl): 1492 _space(space), 1493 _num_dirty_cards(0), 1494 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1495 work_queue, cl) { } 1496 1497 void do_MemRegion(MemRegion mr); 1498 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1499 size_t num_dirty_cards() { return _num_dirty_cards; } 1500 }; 1501 1502 // This closure is used in the non-product build to check 1503 // that there are no MemRegions with a certain property. 1504 class FalseMemRegionClosure: public MemRegionClosure { 1505 void do_MemRegion(MemRegion mr) { 1506 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1507 guarantee(false, "Should never be here"); 1508 } 1509 }; 1510 1511 // This closure is used during the precleaning phase 1512 // to "carefully" rescan marked objects on dirty cards. 1513 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1514 // to accomplish some of its work. 1515 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1516 CMSCollector* _collector; 1517 MemRegion _span; 1518 bool _yield; 1519 Mutex* _freelistLock; 1520 CMSBitMap* _bitMap; 1521 CMSMarkStack* _markStack; 1522 MarkRefsIntoAndScanClosure* _scanningClosure; 1523 1524 public: 1525 ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector, 1526 MemRegion span, 1527 CMSBitMap* bitMap, 1528 CMSMarkStack* markStack, 1529 MarkRefsIntoAndScanClosure* cl, 1530 bool should_yield): 1531 _collector(collector), 1532 _span(span), 1533 _yield(should_yield), 1534 _bitMap(bitMap), 1535 _markStack(markStack), 1536 _scanningClosure(cl) { 1537 } 1538 1539 void do_object(oop p) { 1540 guarantee(false, "call do_object_careful instead"); 1541 } 1542 1543 size_t do_object_careful(oop p) { 1544 guarantee(false, "Unexpected caller"); 1545 return 0; 1546 } 1547 1548 size_t do_object_careful_m(oop p, MemRegion mr); 1549 1550 void setFreelistLock(Mutex* m) { 1551 _freelistLock = m; 1552 _scanningClosure->set_freelistLock(m); 1553 } 1554 1555 private: 1556 inline bool do_yield_check(); 1557 1558 void do_yield_work(); 1559 }; 1560 1561 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1562 CMSCollector* _collector; 1563 MemRegion _span; 1564 bool _yield; 1565 CMSBitMap* _bit_map; 1566 CMSMarkStack* _mark_stack; 1567 PushAndMarkClosure* _scanning_closure; 1568 unsigned int _before_count; 1569 1570 public: 1571 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1572 MemRegion span, 1573 CMSBitMap* bit_map, 1574 CMSMarkStack* mark_stack, 1575 PushAndMarkClosure* cl, 1576 unsigned int before_count, 1577 bool should_yield): 1578 _collector(collector), 1579 _span(span), 1580 _yield(should_yield), 1581 _bit_map(bit_map), 1582 _mark_stack(mark_stack), 1583 _scanning_closure(cl), 1584 _before_count(before_count) 1585 { } 1586 1587 void do_object(oop p) { 1588 guarantee(false, "call do_object_careful instead"); 1589 } 1590 1591 size_t do_object_careful(oop p); 1592 1593 size_t do_object_careful_m(oop p, MemRegion mr) { 1594 guarantee(false, "Unexpected caller"); 1595 return 0; 1596 } 1597 1598 private: 1599 inline void do_yield_check(); 1600 void do_yield_work(); 1601 }; 1602 1603 // This closure is used to accomplish the sweeping work 1604 // after the second checkpoint but before the concurrent reset 1605 // phase. 1606 // 1607 // Terminology 1608 // left hand chunk (LHC) - block of one or more chunks currently being 1609 // coalesced. The LHC is available for coalescing with a new chunk. 1610 // right hand chunk (RHC) - block that is currently being swept that is 1611 // free or garbage that can be coalesced with the LHC. 1612 // _inFreeRange is true if there is currently a LHC 1613 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1614 // _freeRangeInFreeLists is true if the LHC is in the free lists. 1615 // _freeFinger is the address of the current LHC 1616 class SweepClosure: public BlkClosureCareful { 1617 CMSCollector* _collector; // collector doing the work 1618 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1619 CompactibleFreeListSpace* _sp; // Space being swept 1620 HeapWord* _limit;// the address at or above which the sweep should stop 1621 // because we do not expect newly garbage blocks 1622 // eligible for sweeping past that address. 1623 Mutex* _freelistLock; // Free list lock (in space) 1624 CMSBitMap* _bitMap; // Marking bit map (in 1625 // generation) 1626 bool _inFreeRange; // Indicates if we are in the 1627 // midst of a free run 1628 bool _freeRangeInFreeLists; 1629 // Often, we have just found 1630 // a free chunk and started 1631 // a new free range; we do not 1632 // eagerly remove this chunk from 1633 // the free lists unless there is 1634 // a possibility of coalescing. 1635 // When true, this flag indicates 1636 // that the _freeFinger below 1637 // points to a potentially free chunk 1638 // that may still be in the free lists 1639 bool _lastFreeRangeCoalesced; 1640 // free range contains chunks 1641 // coalesced 1642 bool _yield; 1643 // Whether sweeping should be 1644 // done with yields. For instance 1645 // when done by the foreground 1646 // collector we shouldn't yield. 1647 HeapWord* _freeFinger; // When _inFreeRange is set, the 1648 // pointer to the "left hand 1649 // chunk" 1650 size_t _freeRangeSize; 1651 // When _inFreeRange is set, this 1652 // indicates the accumulated size 1653 // of the "left hand chunk" 1654 NOT_PRODUCT( 1655 size_t _numObjectsFreed; 1656 size_t _numWordsFreed; 1657 size_t _numObjectsLive; 1658 size_t _numWordsLive; 1659 size_t _numObjectsAlreadyFree; 1660 size_t _numWordsAlreadyFree; 1661 FreeChunk* _last_fc; 1662 ) 1663 private: 1664 // Code that is common to a free chunk or garbage when 1665 // encountered during sweeping. 1666 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1667 // Process a free chunk during sweeping. 1668 void do_already_free_chunk(FreeChunk *fc); 1669 // Work method called when processing an already free or a 1670 // freshly garbage chunk to do a lookahead and possibly a 1671 // preemptive flush if crossing over _limit. 1672 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1673 // Process a garbage chunk during sweeping. 1674 size_t do_garbage_chunk(FreeChunk *fc); 1675 // Process a live chunk during sweeping. 1676 size_t do_live_chunk(FreeChunk* fc); 1677 1678 // Accessors. 1679 HeapWord* freeFinger() const { return _freeFinger; } 1680 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1681 bool inFreeRange() const { return _inFreeRange; } 1682 void set_inFreeRange(bool v) { _inFreeRange = v; } 1683 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1684 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1685 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1686 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1687 1688 // Initialize a free range. 1689 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1690 // Return this chunk to the free lists. 1691 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1692 1693 // Check if we should yield and do so when necessary. 1694 inline void do_yield_check(HeapWord* addr); 1695 1696 // Yield 1697 void do_yield_work(HeapWord* addr); 1698 1699 // Debugging/Printing 1700 void print_free_block_coalesced(FreeChunk* fc) const; 1701 1702 public: 1703 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1704 CMSBitMap* bitMap, bool should_yield); 1705 ~SweepClosure() PRODUCT_RETURN; 1706 1707 size_t do_blk_careful(HeapWord* addr); 1708 void print() const { print_on(tty); } 1709 void print_on(outputStream *st) const; 1710 }; 1711 1712 // Closures related to weak references processing 1713 1714 // During CMS' weak reference processing, this is a 1715 // work-routine/closure used to complete transitive 1716 // marking of objects as live after a certain point 1717 // in which an initial set has been completely accumulated. 1718 // This closure is currently used both during the final 1719 // remark stop-world phase, as well as during the concurrent 1720 // precleaning of the discovered reference lists. 1721 class CMSDrainMarkingStackClosure: public VoidClosure { 1722 CMSCollector* _collector; 1723 MemRegion _span; 1724 CMSMarkStack* _mark_stack; 1725 CMSBitMap* _bit_map; 1726 CMSKeepAliveClosure* _keep_alive; 1727 bool _concurrent_precleaning; 1728 public: 1729 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1730 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1731 CMSKeepAliveClosure* keep_alive, 1732 bool cpc): 1733 _collector(collector), 1734 _span(span), 1735 _bit_map(bit_map), 1736 _mark_stack(mark_stack), 1737 _keep_alive(keep_alive), 1738 _concurrent_precleaning(cpc) { 1739 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1740 "Mismatch"); 1741 } 1742 1743 void do_void(); 1744 }; 1745 1746 // A parallel version of CMSDrainMarkingStackClosure above. 1747 class CMSParDrainMarkingStackClosure: public VoidClosure { 1748 CMSCollector* _collector; 1749 MemRegion _span; 1750 OopTaskQueue* _work_queue; 1751 CMSBitMap* _bit_map; 1752 CMSInnerParMarkAndPushClosure _mark_and_push; 1753 1754 public: 1755 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1756 MemRegion span, CMSBitMap* bit_map, 1757 OopTaskQueue* work_queue): 1758 _collector(collector), 1759 _span(span), 1760 _bit_map(bit_map), 1761 _work_queue(work_queue), 1762 _mark_and_push(collector, span, bit_map, work_queue) { } 1763 1764 public: 1765 void trim_queue(uint max); 1766 void do_void(); 1767 }; 1768 1769 // Allow yielding or short-circuiting of reference list 1770 // precleaning work. 1771 class CMSPrecleanRefsYieldClosure: public YieldClosure { 1772 CMSCollector* _collector; 1773 void do_yield_work(); 1774 public: 1775 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1776 _collector(collector) {} 1777 virtual bool should_return(); 1778 }; 1779 1780 1781 // Convenience class that locks free list locks for given CMS collector 1782 class FreelistLocker: public StackObj { 1783 private: 1784 CMSCollector* _collector; 1785 public: 1786 FreelistLocker(CMSCollector* collector): 1787 _collector(collector) { 1788 _collector->getFreelistLocks(); 1789 } 1790 1791 ~FreelistLocker() { 1792 _collector->releaseFreelistLocks(); 1793 } 1794 }; 1795 1796 // Mark all dead objects in a given space. 1797 class MarkDeadObjectsClosure: public BlkClosure { 1798 const CMSCollector* _collector; 1799 const CompactibleFreeListSpace* _sp; 1800 CMSBitMap* _live_bit_map; 1801 CMSBitMap* _dead_bit_map; 1802 public: 1803 MarkDeadObjectsClosure(const CMSCollector* collector, 1804 const CompactibleFreeListSpace* sp, 1805 CMSBitMap *live_bit_map, 1806 CMSBitMap *dead_bit_map) : 1807 _collector(collector), 1808 _sp(sp), 1809 _live_bit_map(live_bit_map), 1810 _dead_bit_map(dead_bit_map) {} 1811 size_t do_blk(HeapWord* addr); 1812 }; 1813 1814 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1815 1816 public: 1817 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1818 }; 1819 1820 1821 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPGENERATION_HPP