1/* 2 * Copyright (c) 2001, 2016, 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 59class AdaptiveSizePolicy; 60class CMSCollector; 61class CMSConcMarkingTask; 62class CMSGCAdaptivePolicyCounters; 63class CMSTracer; 64class ConcurrentGCTimer; 65class ConcurrentMarkSweepGeneration; 66class ConcurrentMarkSweepPolicy; 67class ConcurrentMarkSweepThread; 68class CompactibleFreeListSpace; 69class FreeChunk; 70class ParNewGeneration; 71class PromotionInfo; 72class ScanMarkedObjectsAgainCarefullyClosure; 73class TenuredGeneration; 74class 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? 83class 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 BitMapView _bm; // the bit map itself 91 Mutex* const _lock; // mutex protecting _bm; 92 93 public: 94 // constructor 95 CMSBitMap(int shifter, int mutex_rank, const char* mutex_name); 96 97 // allocates the actual storage for the map 98 bool allocate(MemRegion mr); 99 // field getter 100 Mutex* lock() const { return _lock; } 101 // locking verifier convenience function 102 void assert_locked() const PRODUCT_RETURN; 103 104 // inquiries 105 HeapWord* startWord() const { return _bmStartWord; } 106 size_t sizeInWords() const { return _bmWordSize; } 107 size_t sizeInBits() const { return _bm.size(); } 108 // the following is one past the last word in space 109 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 110 111 // reading marks 112 bool isMarked(HeapWord* addr) const; 113 bool par_isMarked(HeapWord* addr) const; // do not lock checks 114 bool isUnmarked(HeapWord* addr) const; 115 bool isAllClear() const; 116 117 // writing marks 118 void mark(HeapWord* addr); 119 // For marking by parallel GC threads; 120 // returns true if we did, false if another thread did 121 bool par_mark(HeapWord* addr); 122 123 void mark_range(MemRegion mr); 124 void par_mark_range(MemRegion mr); 125 void mark_large_range(MemRegion mr); 126 void par_mark_large_range(MemRegion mr); 127 void par_clear(HeapWord* addr); // For unmarking by parallel GC threads. 128 void clear_range(MemRegion mr); 129 void par_clear_range(MemRegion mr); 130 void clear_large_range(MemRegion mr); 131 void par_clear_large_range(MemRegion mr); 132 void clear_all(); 133 void clear_all_incrementally(); // Not yet implemented!! 134 135 NOT_PRODUCT( 136 // checks the memory region for validity 137 void region_invariant(MemRegion mr); 138 ) 139 140 // iteration 141 void iterate(BitMapClosure* cl) { 142 _bm.iterate(cl); 143 } 144 void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right); 145 void dirty_range_iterate_clear(MemRegionClosure* cl); 146 void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl); 147 148 // auxiliary support for iteration 149 HeapWord* getNextMarkedWordAddress(HeapWord* addr) const; 150 HeapWord* getNextMarkedWordAddress(HeapWord* start_addr, 151 HeapWord* end_addr) const; 152 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const; 153 HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr, 154 HeapWord* end_addr) const; 155 MemRegion getAndClearMarkedRegion(HeapWord* addr); 156 MemRegion getAndClearMarkedRegion(HeapWord* start_addr, 157 HeapWord* end_addr); 158 159 // conversion utilities 160 HeapWord* offsetToHeapWord(size_t offset) const; 161 size_t heapWordToOffset(HeapWord* addr) const; 162 size_t heapWordDiffToOffsetDiff(size_t diff) const; 163 164 void print_on_error(outputStream* st, const char* prefix) const; 165 166 // debugging 167 // is this address range covered by the bit-map? 168 NOT_PRODUCT( 169 bool covers(MemRegion mr) const; 170 bool covers(HeapWord* start, size_t size = 0) const; 171 ) 172 void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN; 173}; 174 175// Represents a marking stack used by the CMS collector. 176// Ideally this should be GrowableArray<> just like MSC's marking stack(s). 177class CMSMarkStack: public CHeapObj<mtGC> { 178 friend class CMSCollector; // To get at expansion stats further below. 179 180 VirtualSpace _virtual_space; // Space for the stack 181 oop* _base; // Bottom of stack 182 size_t _index; // One more than last occupied index 183 size_t _capacity; // Max #elements 184 Mutex _par_lock; // An advisory lock used in case of parallel access 185 NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run 186 187 protected: 188 size_t _hit_limit; // We hit max stack size limit 189 size_t _failed_double; // We failed expansion before hitting limit 190 191 public: 192 CMSMarkStack(): 193 _par_lock(Mutex::event, "CMSMarkStack._par_lock", true, 194 Monitor::_safepoint_check_never), 195 _hit_limit(0), 196 _failed_double(0) {} 197 198 bool allocate(size_t size); 199 200 size_t capacity() const { return _capacity; } 201 202 oop pop() { 203 if (!isEmpty()) { 204 return _base[--_index] ; 205 } 206 return NULL; 207 } 208 209 bool push(oop ptr) { 210 if (isFull()) { 211 return false; 212 } else { 213 _base[_index++] = ptr; 214 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 215 return true; 216 } 217 } 218 219 bool isEmpty() const { return _index == 0; } 220 bool isFull() const { 221 assert(_index <= _capacity, "buffer overflow"); 222 return _index == _capacity; 223 } 224 225 size_t length() { return _index; } 226 227 // "Parallel versions" of some of the above 228 oop par_pop() { 229 // lock and pop 230 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 231 return pop(); 232 } 233 234 bool par_push(oop ptr) { 235 // lock and push 236 MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag); 237 return push(ptr); 238 } 239 240 // Forcibly reset the stack, losing all of its contents. 241 void reset() { 242 _index = 0; 243 } 244 245 // Expand the stack, typically in response to an overflow condition. 246 void expand(); 247 248 // Compute the least valued stack element. 249 oop least_value(HeapWord* low) { 250 oop least = (oop)low; 251 for (size_t i = 0; i < _index; i++) { 252 least = MIN2(least, _base[i]); 253 } 254 return least; 255 } 256 257 // Exposed here to allow stack expansion in || case. 258 Mutex* par_lock() { return &_par_lock; } 259}; 260 261class CardTableRS; 262class CMSParGCThreadState; 263 264class ModUnionClosure: public MemRegionClosure { 265 protected: 266 CMSBitMap* _t; 267 public: 268 ModUnionClosure(CMSBitMap* t): _t(t) { } 269 void do_MemRegion(MemRegion mr); 270}; 271 272class ModUnionClosurePar: public ModUnionClosure { 273 public: 274 ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { } 275 void do_MemRegion(MemRegion mr); 276}; 277 278// Survivor Chunk Array in support of parallelization of 279// Survivor Space rescan. 280class ChunkArray: public CHeapObj<mtGC> { 281 size_t _index; 282 size_t _capacity; 283 size_t _overflows; 284 HeapWord** _array; // storage for array 285 286 public: 287 ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {} 288 ChunkArray(HeapWord** a, size_t c): 289 _index(0), _capacity(c), _overflows(0), _array(a) {} 290 291 HeapWord** array() { return _array; } 292 void set_array(HeapWord** a) { _array = a; } 293 294 size_t capacity() { return _capacity; } 295 void set_capacity(size_t c) { _capacity = c; } 296 297 size_t end() { 298 assert(_index <= capacity(), 299 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds", 300 _index, _capacity); 301 return _index; 302 } // exclusive 303 304 HeapWord* nth(size_t n) { 305 assert(n < end(), "Out of bounds access"); 306 return _array[n]; 307 } 308 309 void reset() { 310 _index = 0; 311 if (_overflows > 0) { 312 log_trace(gc)("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", _capacity, _overflows); 313 } 314 _overflows = 0; 315 } 316 317 void record_sample(HeapWord* p, size_t sz) { 318 // For now we do not do anything with the size 319 if (_index < _capacity) { 320 _array[_index++] = p; 321 } else { 322 ++_overflows; 323 assert(_index == _capacity, 324 "_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT 325 "): out of bounds at overflow#" SIZE_FORMAT, 326 _index, _capacity, _overflows); 327 } 328 } 329}; 330 331// 332// Timing, allocation and promotion statistics for gc scheduling and incremental 333// mode pacing. Most statistics are exponential averages. 334// 335class CMSStats VALUE_OBJ_CLASS_SPEC { 336 private: 337 ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen. 338 339 // The following are exponential averages with factor alpha: 340 // avg = (100 - alpha) * avg + alpha * cur_sample 341 // 342 // The durations measure: end_time[n] - start_time[n] 343 // The periods measure: start_time[n] - start_time[n-1] 344 // 345 // The cms period and duration include only concurrent collections; time spent 346 // in foreground cms collections due to System.gc() or because of a failure to 347 // keep up are not included. 348 // 349 // There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the 350 // real value, but is used only after the first period. A value of 100 is 351 // used for the first sample so it gets the entire weight. 352 unsigned int _saved_alpha; // 0-100 353 unsigned int _gc0_alpha; 354 unsigned int _cms_alpha; 355 356 double _gc0_duration; 357 double _gc0_period; 358 size_t _gc0_promoted; // bytes promoted per gc0 359 double _cms_duration; 360 double _cms_duration_pre_sweep; // time from initiation to start of sweep 361 double _cms_period; 362 size_t _cms_allocated; // bytes of direct allocation per gc0 period 363 364 // Timers. 365 elapsedTimer _cms_timer; 366 TimeStamp _gc0_begin_time; 367 TimeStamp _cms_begin_time; 368 TimeStamp _cms_end_time; 369 370 // Snapshots of the amount used in the CMS generation. 371 size_t _cms_used_at_gc0_begin; 372 size_t _cms_used_at_gc0_end; 373 size_t _cms_used_at_cms_begin; 374 375 // Used to prevent the duty cycle from being reduced in the middle of a cms 376 // cycle. 377 bool _allow_duty_cycle_reduction; 378 379 enum { 380 _GC0_VALID = 0x1, 381 _CMS_VALID = 0x2, 382 _ALL_VALID = _GC0_VALID | _CMS_VALID 383 }; 384 385 unsigned int _valid_bits; 386 387 protected: 388 // In support of adjusting of cms trigger ratios based on history 389 // of concurrent mode failure. 390 double cms_free_adjustment_factor(size_t free) const; 391 void adjust_cms_free_adjustment_factor(bool fail, size_t free); 392 393 public: 394 CMSStats(ConcurrentMarkSweepGeneration* cms_gen, 395 unsigned int alpha = CMSExpAvgFactor); 396 397 // Whether or not the statistics contain valid data; higher level statistics 398 // cannot be called until this returns true (they require at least one young 399 // gen and one cms cycle to have completed). 400 bool valid() const; 401 402 // Record statistics. 403 void record_gc0_begin(); 404 void record_gc0_end(size_t cms_gen_bytes_used); 405 void record_cms_begin(); 406 void record_cms_end(); 407 408 // Allow management of the cms timer, which must be stopped/started around 409 // yield points. 410 elapsedTimer& cms_timer() { return _cms_timer; } 411 void start_cms_timer() { _cms_timer.start(); } 412 void stop_cms_timer() { _cms_timer.stop(); } 413 414 // Basic statistics; units are seconds or bytes. 415 double gc0_period() const { return _gc0_period; } 416 double gc0_duration() const { return _gc0_duration; } 417 size_t gc0_promoted() const { return _gc0_promoted; } 418 double cms_period() const { return _cms_period; } 419 double cms_duration() const { return _cms_duration; } 420 size_t cms_allocated() const { return _cms_allocated; } 421 422 size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;} 423 424 // Seconds since the last background cms cycle began or ended. 425 double cms_time_since_begin() const; 426 double cms_time_since_end() const; 427 428 // Higher level statistics--caller must check that valid() returns true before 429 // calling. 430 431 // Returns bytes promoted per second of wall clock time. 432 double promotion_rate() const; 433 434 // Returns bytes directly allocated per second of wall clock time. 435 double cms_allocation_rate() const; 436 437 // Rate at which space in the cms generation is being consumed (sum of the 438 // above two). 439 double cms_consumption_rate() const; 440 441 // Returns an estimate of the number of seconds until the cms generation will 442 // fill up, assuming no collection work is done. 443 double time_until_cms_gen_full() const; 444 445 // Returns an estimate of the number of seconds remaining until 446 // the cms generation collection should start. 447 double time_until_cms_start() const; 448 449 // End of higher level statistics. 450 451 // Debugging. 452 void print_on(outputStream* st) const PRODUCT_RETURN; 453 void print() const { print_on(tty); } 454}; 455 456// A closure related to weak references processing which 457// we embed in the CMSCollector, since we need to pass 458// it to the reference processor for secondary filtering 459// of references based on reachability of referent; 460// see role of _is_alive_non_header closure in the 461// ReferenceProcessor class. 462// For objects in the CMS generation, this closure checks 463// if the object is "live" (reachable). Used in weak 464// reference processing. 465class CMSIsAliveClosure: public BoolObjectClosure { 466 const MemRegion _span; 467 const CMSBitMap* _bit_map; 468 469 friend class CMSCollector; 470 public: 471 CMSIsAliveClosure(MemRegion span, 472 CMSBitMap* bit_map): 473 _span(span), 474 _bit_map(bit_map) { 475 assert(!span.is_empty(), "Empty span could spell trouble"); 476 } 477 478 bool do_object_b(oop obj); 479}; 480 481 482// Implements AbstractRefProcTaskExecutor for CMS. 483class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 484public: 485 486 CMSRefProcTaskExecutor(CMSCollector& collector) 487 : _collector(collector) 488 { } 489 490 // Executes a task using worker threads. 491 virtual void execute(ProcessTask& task); 492 virtual void execute(EnqueueTask& task); 493private: 494 CMSCollector& _collector; 495}; 496 497 498class CMSCollector: public CHeapObj<mtGC> { 499 friend class VMStructs; 500 friend class ConcurrentMarkSweepThread; 501 friend class ConcurrentMarkSweepGeneration; 502 friend class CompactibleFreeListSpace; 503 friend class CMSParMarkTask; 504 friend class CMSParInitialMarkTask; 505 friend class CMSParRemarkTask; 506 friend class CMSConcMarkingTask; 507 friend class CMSRefProcTaskProxy; 508 friend class CMSRefProcTaskExecutor; 509 friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden 510 friend class SurvivorSpacePrecleanClosure; // --- ditto ------- 511 friend class PushOrMarkClosure; // to access _restart_addr 512 friend class ParPushOrMarkClosure; // to access _restart_addr 513 friend class MarkFromRootsClosure; // -- ditto -- 514 // ... and for clearing cards 515 friend class ParMarkFromRootsClosure; // to access _restart_addr 516 // ... and for clearing cards 517 friend class ParConcMarkingClosure; // to access _restart_addr etc. 518 friend class MarkFromRootsVerifyClosure; // to access _restart_addr 519 friend class PushAndMarkVerifyClosure; // -- ditto -- 520 friend class MarkRefsIntoAndScanClosure; // to access _overflow_list 521 friend class PushAndMarkClosure; // -- ditto -- 522 friend class ParPushAndMarkClosure; // -- ditto -- 523 friend class CMSKeepAliveClosure; // -- ditto -- 524 friend class CMSDrainMarkingStackClosure; // -- ditto -- 525 friend class CMSInnerParMarkAndPushClosure; // -- ditto -- 526 NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list 527 friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait 528 friend class VM_CMS_Operation; 529 friend class VM_CMS_Initial_Mark; 530 friend class VM_CMS_Final_Remark; 531 friend class TraceCMSMemoryManagerStats; 532 533 private: 534 jlong _time_of_last_gc; 535 void update_time_of_last_gc(jlong now) { 536 _time_of_last_gc = now; 537 } 538 539 OopTaskQueueSet* _task_queues; 540 541 // Overflow list of grey objects, threaded through mark-word 542 // Manipulated with CAS in the parallel/multi-threaded case. 543 oopDesc* volatile _overflow_list; 544 // The following array-pair keeps track of mark words 545 // displaced for accommodating overflow list above. 546 // This code will likely be revisited under RFE#4922830. 547 Stack<oop, mtGC> _preserved_oop_stack; 548 Stack<markOop, mtGC> _preserved_mark_stack; 549 550 int* _hash_seed; 551 552 // In support of multi-threaded concurrent phases 553 YieldingFlexibleWorkGang* _conc_workers; 554 555 // Performance Counters 556 CollectorCounters* _gc_counters; 557 558 // Initialization Errors 559 bool _completed_initialization; 560 561 // In support of ExplicitGCInvokesConcurrent 562 static bool _full_gc_requested; 563 static GCCause::Cause _full_gc_cause; 564 unsigned int _collection_count_start; 565 566 // Should we unload classes this concurrent cycle? 567 bool _should_unload_classes; 568 unsigned int _concurrent_cycles_since_last_unload; 569 unsigned int concurrent_cycles_since_last_unload() const { 570 return _concurrent_cycles_since_last_unload; 571 } 572 // Did we (allow) unload classes in the previous concurrent cycle? 573 bool unloaded_classes_last_cycle() const { 574 return concurrent_cycles_since_last_unload() == 0; 575 } 576 // Root scanning options for perm gen 577 int _roots_scanning_options; 578 int roots_scanning_options() const { return _roots_scanning_options; } 579 void add_root_scanning_option(int o) { _roots_scanning_options |= o; } 580 void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; } 581 582 // Verification support 583 CMSBitMap _verification_mark_bm; 584 void verify_after_remark_work_1(); 585 void verify_after_remark_work_2(); 586 587 // True if any verification flag is on. 588 bool _verifying; 589 bool verifying() const { return _verifying; } 590 void set_verifying(bool v) { _verifying = v; } 591 592 // Collector policy 593 ConcurrentMarkSweepPolicy* _collector_policy; 594 ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; } 595 596 void set_did_compact(bool v); 597 598 // XXX Move these to CMSStats ??? FIX ME !!! 599 elapsedTimer _inter_sweep_timer; // Time between sweeps 600 elapsedTimer _intra_sweep_timer; // Time _in_ sweeps 601 // Padded decaying average estimates of the above 602 AdaptivePaddedAverage _inter_sweep_estimate; 603 AdaptivePaddedAverage _intra_sweep_estimate; 604 605 CMSTracer* _gc_tracer_cm; 606 ConcurrentGCTimer* _gc_timer_cm; 607 608 bool _cms_start_registered; 609 610 GCHeapSummary _last_heap_summary; 611 MetaspaceSummary _last_metaspace_summary; 612 613 void register_gc_start(GCCause::Cause cause); 614 void register_gc_end(); 615 void save_heap_summary(); 616 void report_heap_summary(GCWhen::Type when); 617 618 protected: 619 ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS) 620 MemRegion _span; // Span covering above two 621 CardTableRS* _ct; // Card table 622 623 // CMS marking support structures 624 CMSBitMap _markBitMap; 625 CMSBitMap _modUnionTable; 626 CMSMarkStack _markStack; 627 628 HeapWord* _restart_addr; // In support of marking stack overflow 629 void lower_restart_addr(HeapWord* low); 630 631 // Counters in support of marking stack / work queue overflow handling: 632 // a non-zero value indicates certain types of overflow events during 633 // the current CMS cycle and could lead to stack resizing efforts at 634 // an opportune future time. 635 size_t _ser_pmc_preclean_ovflw; 636 size_t _ser_pmc_remark_ovflw; 637 size_t _par_pmc_remark_ovflw; 638 size_t _ser_kac_preclean_ovflw; 639 size_t _ser_kac_ovflw; 640 size_t _par_kac_ovflw; 641 NOT_PRODUCT(ssize_t _num_par_pushes;) 642 643 // ("Weak") Reference processing support. 644 ReferenceProcessor* _ref_processor; 645 CMSIsAliveClosure _is_alive_closure; 646 // Keep this textually after _markBitMap and _span; c'tor dependency. 647 648 ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work 649 ModUnionClosurePar _modUnionClosurePar; 650 651 // CMS abstract state machine 652 // initial_state: Idling 653 // next_state(Idling) = {Marking} 654 // next_state(Marking) = {Precleaning, Sweeping} 655 // next_state(Precleaning) = {AbortablePreclean, FinalMarking} 656 // next_state(AbortablePreclean) = {FinalMarking} 657 // next_state(FinalMarking) = {Sweeping} 658 // next_state(Sweeping) = {Resizing} 659 // next_state(Resizing) = {Resetting} 660 // next_state(Resetting) = {Idling} 661 // The numeric values below are chosen so that: 662 // . _collectorState <= Idling == post-sweep && pre-mark 663 // . _collectorState in (Idling, Sweeping) == {initial,final}marking || 664 // precleaning || abortablePrecleanb 665 public: 666 enum CollectorState { 667 Resizing = 0, 668 Resetting = 1, 669 Idling = 2, 670 InitialMarking = 3, 671 Marking = 4, 672 Precleaning = 5, 673 AbortablePreclean = 6, 674 FinalMarking = 7, 675 Sweeping = 8 676 }; 677 protected: 678 static CollectorState _collectorState; 679 680 // State related to prologue/epilogue invocation for my generations 681 bool _between_prologue_and_epilogue; 682 683 // Signaling/State related to coordination between fore- and background GC 684 // Note: When the baton has been passed from background GC to foreground GC, 685 // _foregroundGCIsActive is true and _foregroundGCShouldWait is false. 686 static bool _foregroundGCIsActive; // true iff foreground collector is active or 687 // wants to go active 688 static bool _foregroundGCShouldWait; // true iff background GC is active and has not 689 // yet passed the baton to the foreground GC 690 691 // Support for CMSScheduleRemark (abortable preclean) 692 bool _abort_preclean; 693 bool _start_sampling; 694 695 int _numYields; 696 size_t _numDirtyCards; 697 size_t _sweep_count; 698 699 // Occupancy used for bootstrapping stats 700 double _bootstrap_occupancy; 701 702 // Timer 703 elapsedTimer _timer; 704 705 // Timing, allocation and promotion statistics, used for scheduling. 706 CMSStats _stats; 707 708 enum CMS_op_type { 709 CMS_op_checkpointRootsInitial, 710 CMS_op_checkpointRootsFinal 711 }; 712 713 void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause); 714 bool stop_world_and_do(CMS_op_type op); 715 716 OopTaskQueueSet* task_queues() { return _task_queues; } 717 int* hash_seed(int i) { return &_hash_seed[i]; } 718 YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; } 719 720 // Support for parallelizing Eden rescan in CMS remark phase 721 void sample_eden(); // ... sample Eden space top 722 723 private: 724 // Support for parallelizing young gen rescan in CMS remark phase 725 ParNewGeneration* _young_gen; 726 727 HeapWord* volatile* _top_addr; // ... Top of Eden 728 HeapWord** _end_addr; // ... End of Eden 729 Mutex* _eden_chunk_lock; 730 HeapWord** _eden_chunk_array; // ... Eden partitioning array 731 size_t _eden_chunk_index; // ... top (exclusive) of array 732 size_t _eden_chunk_capacity; // ... max entries in array 733 734 // Support for parallelizing survivor space rescan 735 HeapWord** _survivor_chunk_array; 736 size_t _survivor_chunk_index; 737 size_t _survivor_chunk_capacity; 738 size_t* _cursor; 739 ChunkArray* _survivor_plab_array; 740 741 // Support for marking stack overflow handling 742 bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack); 743 bool par_take_from_overflow_list(size_t num, 744 OopTaskQueue* to_work_q, 745 int no_of_gc_threads); 746 void push_on_overflow_list(oop p); 747 void par_push_on_overflow_list(oop p); 748 // The following is, obviously, not, in general, "MT-stable" 749 bool overflow_list_is_empty() const; 750 751 void preserve_mark_if_necessary(oop p); 752 void par_preserve_mark_if_necessary(oop p); 753 void preserve_mark_work(oop p, markOop m); 754 void restore_preserved_marks_if_any(); 755 NOT_PRODUCT(bool no_preserved_marks() const;) 756 // In support of testing overflow code 757 NOT_PRODUCT(int _overflow_counter;) 758 NOT_PRODUCT(bool simulate_overflow();) // Sequential 759 NOT_PRODUCT(bool par_simulate_overflow();) // MT version 760 761 // CMS work methods 762 void checkpointRootsInitialWork(); // Initial checkpoint work 763 764 // A return value of false indicates failure due to stack overflow 765 bool markFromRootsWork(); // Concurrent marking work 766 767 public: // FIX ME!!! only for testing 768 bool do_marking_st(); // Single-threaded marking 769 bool do_marking_mt(); // Multi-threaded marking 770 771 private: 772 773 // Concurrent precleaning work 774 size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen, 775 ScanMarkedObjectsAgainCarefullyClosure* cl); 776 size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen, 777 ScanMarkedObjectsAgainCarefullyClosure* cl); 778 // Does precleaning work, returning a quantity indicative of 779 // the amount of "useful work" done. 780 size_t preclean_work(bool clean_refs, bool clean_survivors); 781 void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock); 782 void abortable_preclean(); // Preclean while looking for possible abort 783 void initialize_sequential_subtasks_for_young_gen_rescan(int i); 784 // Helper function for above; merge-sorts the per-thread plab samples 785 void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads); 786 // Resets (i.e. clears) the per-thread plab sample vectors 787 void reset_survivor_plab_arrays(); 788 789 // Final (second) checkpoint work 790 void checkpointRootsFinalWork(); 791 // Work routine for parallel version of remark 792 void do_remark_parallel(); 793 // Work routine for non-parallel version of remark 794 void do_remark_non_parallel(); 795 // Reference processing work routine (during second checkpoint) 796 void refProcessingWork(); 797 798 // Concurrent sweeping work 799 void sweepWork(ConcurrentMarkSweepGeneration* old_gen); 800 801 // Concurrent resetting of support data structures 802 void reset_concurrent(); 803 // Resetting of support data structures from a STW full GC 804 void reset_stw(); 805 806 // Clear _expansion_cause fields of constituent generations 807 void clear_expansion_cause(); 808 809 // An auxiliary method used to record the ends of 810 // used regions of each generation to limit the extent of sweep 811 void save_sweep_limits(); 812 813 // A work method used by the foreground collector to do 814 // a mark-sweep-compact. 815 void do_compaction_work(bool clear_all_soft_refs); 816 817 // Work methods for reporting concurrent mode interruption or failure 818 bool is_external_interruption(); 819 void report_concurrent_mode_interruption(); 820 821 // If the background GC is active, acquire control from the background 822 // GC and do the collection. 823 void acquire_control_and_collect(bool full, bool clear_all_soft_refs); 824 825 // For synchronizing passing of control from background to foreground 826 // GC. waitForForegroundGC() is called by the background 827 // collector. It if had to wait for a foreground collection, 828 // it returns true and the background collection should assume 829 // that the collection was finished by the foreground 830 // collector. 831 bool waitForForegroundGC(); 832 833 size_t block_size_using_printezis_bits(HeapWord* addr) const; 834 size_t block_size_if_printezis_bits(HeapWord* addr) const; 835 HeapWord* next_card_start_after_block(HeapWord* addr) const; 836 837 void setup_cms_unloading_and_verification_state(); 838 public: 839 CMSCollector(ConcurrentMarkSweepGeneration* cmsGen, 840 CardTableRS* ct, 841 ConcurrentMarkSweepPolicy* cp); 842 ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; } 843 844 ReferenceProcessor* ref_processor() { return _ref_processor; } 845 void ref_processor_init(); 846 847 Mutex* bitMapLock() const { return _markBitMap.lock(); } 848 static CollectorState abstract_state() { return _collectorState; } 849 850 bool should_abort_preclean() const; // Whether preclean should be aborted. 851 size_t get_eden_used() const; 852 size_t get_eden_capacity() const; 853 854 ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; } 855 856 // Locking checks 857 NOT_PRODUCT(static bool have_cms_token();) 858 859 bool shouldConcurrentCollect(); 860 861 void collect(bool full, 862 bool clear_all_soft_refs, 863 size_t size, 864 bool tlab); 865 void collect_in_background(GCCause::Cause cause); 866 867 // In support of ExplicitGCInvokesConcurrent 868 static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause); 869 // Should we unload classes in a particular concurrent cycle? 870 bool should_unload_classes() const { 871 return _should_unload_classes; 872 } 873 void update_should_unload_classes(); 874 875 void direct_allocated(HeapWord* start, size_t size); 876 877 // Object is dead if not marked and current phase is sweeping. 878 bool is_dead_obj(oop obj) const; 879 880 // After a promotion (of "start"), do any necessary marking. 881 // If "par", then it's being done by a parallel GC thread. 882 // The last two args indicate if we need precise marking 883 // and if so the size of the object so it can be dirtied 884 // in its entirety. 885 void promoted(bool par, HeapWord* start, 886 bool is_obj_array, size_t obj_size); 887 888 void getFreelistLocks() const; 889 void releaseFreelistLocks() const; 890 bool haveFreelistLocks() const; 891 892 // Adjust size of underlying generation 893 void compute_new_size(); 894 895 // GC prologue and epilogue 896 void gc_prologue(bool full); 897 void gc_epilogue(bool full); 898 899 jlong time_of_last_gc(jlong now) { 900 if (_collectorState <= Idling) { 901 // gc not in progress 902 return _time_of_last_gc; 903 } else { 904 // collection in progress 905 return now; 906 } 907 } 908 909 // Support for parallel remark of survivor space 910 void* get_data_recorder(int thr_num); 911 void sample_eden_chunk(); 912 913 CMSBitMap* markBitMap() { return &_markBitMap; } 914 void directAllocated(HeapWord* start, size_t size); 915 916 // Main CMS steps and related support 917 void checkpointRootsInitial(); 918 bool markFromRoots(); // a return value of false indicates failure 919 // due to stack overflow 920 void preclean(); 921 void checkpointRootsFinal(); 922 void sweep(); 923 924 // Check that the currently executing thread is the expected 925 // one (foreground collector or background collector). 926 static void check_correct_thread_executing() PRODUCT_RETURN; 927 928 NOT_PRODUCT(bool is_cms_reachable(HeapWord* addr);) 929 930 // Performance Counter Support 931 CollectorCounters* counters() { return _gc_counters; } 932 933 // Timer stuff 934 void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); } 935 void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); } 936 void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); } 937 jlong timerTicks() { assert(!_timer.is_active(), "Error"); return _timer.ticks(); } 938 939 int yields() { return _numYields; } 940 void resetYields() { _numYields = 0; } 941 void incrementYields() { _numYields++; } 942 void resetNumDirtyCards() { _numDirtyCards = 0; } 943 void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; } 944 size_t numDirtyCards() { return _numDirtyCards; } 945 946 static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; } 947 static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; } 948 static bool foregroundGCIsActive() { return _foregroundGCIsActive; } 949 static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; } 950 size_t sweep_count() const { return _sweep_count; } 951 void increment_sweep_count() { _sweep_count++; } 952 953 // Timers/stats for gc scheduling and incremental mode pacing. 954 CMSStats& stats() { return _stats; } 955 956 // Adaptive size policy 957 AdaptiveSizePolicy* size_policy(); 958 959 static void print_on_error(outputStream* st); 960 961 // Debugging 962 void verify(); 963 bool verify_after_remark(); 964 void verify_ok_to_terminate() const PRODUCT_RETURN; 965 void verify_work_stacks_empty() const PRODUCT_RETURN; 966 void verify_overflow_empty() const PRODUCT_RETURN; 967 968 // Convenience methods in support of debugging 969 static const size_t skip_header_HeapWords() PRODUCT_RETURN0; 970 HeapWord* block_start(const void* p) const PRODUCT_RETURN0; 971 972 // Accessors 973 CMSMarkStack* verification_mark_stack() { return &_markStack; } 974 CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; } 975 976 // Initialization errors 977 bool completed_initialization() { return _completed_initialization; } 978 979 void print_eden_and_survivor_chunk_arrays(); 980 981 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 982}; 983 984class CMSExpansionCause : public AllStatic { 985 public: 986 enum Cause { 987 _no_expansion, 988 _satisfy_free_ratio, 989 _satisfy_promotion, 990 _satisfy_allocation, 991 _allocate_par_lab, 992 _allocate_par_spooling_space, 993 _adaptive_size_policy 994 }; 995 // Return a string describing the cause of the expansion. 996 static const char* to_string(CMSExpansionCause::Cause cause); 997}; 998 999class ConcurrentMarkSweepGeneration: public CardGeneration { 1000 friend class VMStructs; 1001 friend class ConcurrentMarkSweepThread; 1002 friend class ConcurrentMarkSweep; 1003 friend class CMSCollector; 1004 protected: 1005 static CMSCollector* _collector; // the collector that collects us 1006 CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now) 1007 1008 // Performance Counters 1009 GenerationCounters* _gen_counters; 1010 GSpaceCounters* _space_counters; 1011 1012 // Words directly allocated, used by CMSStats. 1013 size_t _direct_allocated_words; 1014 1015 // Non-product stat counters 1016 NOT_PRODUCT( 1017 size_t _numObjectsPromoted; 1018 size_t _numWordsPromoted; 1019 size_t _numObjectsAllocated; 1020 size_t _numWordsAllocated; 1021 ) 1022 1023 // Used for sizing decisions 1024 bool _incremental_collection_failed; 1025 bool incremental_collection_failed() { 1026 return _incremental_collection_failed; 1027 } 1028 void set_incremental_collection_failed() { 1029 _incremental_collection_failed = true; 1030 } 1031 void clear_incremental_collection_failed() { 1032 _incremental_collection_failed = false; 1033 } 1034 1035 // accessors 1036 void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;} 1037 CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; } 1038 1039 // Accessing spaces 1040 CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; } 1041 1042 private: 1043 // For parallel young-gen GC support. 1044 CMSParGCThreadState** _par_gc_thread_states; 1045 1046 // Reason generation was expanded 1047 CMSExpansionCause::Cause _expansion_cause; 1048 1049 // In support of MinChunkSize being larger than min object size 1050 const double _dilatation_factor; 1051 1052 // True if a compacting collection was done. 1053 bool _did_compact; 1054 bool did_compact() { return _did_compact; } 1055 1056 // Fraction of current occupancy at which to start a CMS collection which 1057 // will collect this generation (at least). 1058 double _initiating_occupancy; 1059 1060 protected: 1061 // Shrink generation by specified size (returns false if unable to shrink) 1062 void shrink_free_list_by(size_t bytes); 1063 1064 // Update statistics for GC 1065 virtual void update_gc_stats(Generation* current_generation, bool full); 1066 1067 // Maximum available space in the generation (including uncommitted) 1068 // space. 1069 size_t max_available() const; 1070 1071 // getter and initializer for _initiating_occupancy field. 1072 double initiating_occupancy() const { return _initiating_occupancy; } 1073 void init_initiating_occupancy(intx io, uintx tr); 1074 1075 void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause); 1076 1077 void assert_correct_size_change_locking(); 1078 1079 public: 1080 ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size, CardTableRS* ct); 1081 1082 // Accessors 1083 CMSCollector* collector() const { return _collector; } 1084 static void set_collector(CMSCollector* collector) { 1085 assert(_collector == NULL, "already set"); 1086 _collector = collector; 1087 } 1088 CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; } 1089 1090 Mutex* freelistLock() const; 1091 1092 virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; } 1093 1094 void set_did_compact(bool v) { _did_compact = v; } 1095 1096 bool refs_discovery_is_atomic() const { return false; } 1097 bool refs_discovery_is_mt() const { 1098 // Note: CMS does MT-discovery during the parallel-remark 1099 // phases. Use ReferenceProcessorMTMutator to make refs 1100 // discovery MT-safe during such phases or other parallel 1101 // discovery phases in the future. This may all go away 1102 // if/when we decide that refs discovery is sufficiently 1103 // rare that the cost of the CAS's involved is in the 1104 // noise. That's a measurement that should be done, and 1105 // the code simplified if that turns out to be the case. 1106 return ConcGCThreads > 1; 1107 } 1108 1109 // Override 1110 virtual void ref_processor_init(); 1111 1112 void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; } 1113 1114 // Space enquiries 1115 double occupancy() const { return ((double)used())/((double)capacity()); } 1116 size_t contiguous_available() const; 1117 size_t unsafe_max_alloc_nogc() const; 1118 1119 // over-rides 1120 MemRegion used_region_at_save_marks() const; 1121 1122 // Adjust quantities in the generation affected by 1123 // the compaction. 1124 void reset_after_compaction(); 1125 1126 // Allocation support 1127 HeapWord* allocate(size_t size, bool tlab); 1128 HeapWord* have_lock_and_allocate(size_t size, bool tlab); 1129 oop promote(oop obj, size_t obj_size); 1130 HeapWord* par_allocate(size_t size, bool tlab) { 1131 return allocate(size, tlab); 1132 } 1133 1134 1135 // Used by CMSStats to track direct allocation. The value is sampled and 1136 // reset after each young gen collection. 1137 size_t direct_allocated_words() const { return _direct_allocated_words; } 1138 void reset_direct_allocated_words() { _direct_allocated_words = 0; } 1139 1140 // Overrides for parallel promotion. 1141 virtual oop par_promote(int thread_num, 1142 oop obj, markOop m, size_t word_sz); 1143 virtual void par_promote_alloc_done(int thread_num); 1144 virtual void par_oop_since_save_marks_iterate_done(int thread_num); 1145 1146 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const; 1147 1148 // Inform this (old) generation that a promotion failure was 1149 // encountered during a collection of the young generation. 1150 virtual void promotion_failure_occurred(); 1151 1152 bool should_collect(bool full, size_t size, bool tlab); 1153 virtual bool should_concurrent_collect() const; 1154 virtual bool is_too_full() const; 1155 void collect(bool full, 1156 bool clear_all_soft_refs, 1157 size_t size, 1158 bool tlab); 1159 1160 HeapWord* expand_and_allocate(size_t word_size, 1161 bool tlab, 1162 bool parallel = false); 1163 1164 // GC prologue and epilogue 1165 void gc_prologue(bool full); 1166 void gc_prologue_work(bool full, bool registerClosure, 1167 ModUnionClosure* modUnionClosure); 1168 void gc_epilogue(bool full); 1169 void gc_epilogue_work(bool full); 1170 1171 // Time since last GC of this generation 1172 jlong time_of_last_gc(jlong now) { 1173 return collector()->time_of_last_gc(now); 1174 } 1175 void update_time_of_last_gc(jlong now) { 1176 collector()-> update_time_of_last_gc(now); 1177 } 1178 1179 // Allocation failure 1180 void shrink(size_t bytes); 1181 HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz); 1182 bool expand_and_ensure_spooling_space(PromotionInfo* promo); 1183 1184 // Iteration support and related enquiries 1185 void save_marks(); 1186 bool no_allocs_since_save_marks(); 1187 1188 // Iteration support specific to CMS generations 1189 void save_sweep_limit(); 1190 1191 // More iteration support 1192 virtual void oop_iterate(ExtendedOopClosure* cl); 1193 virtual void safe_object_iterate(ObjectClosure* cl); 1194 virtual void object_iterate(ObjectClosure* cl); 1195 1196 // Need to declare the full complement of closures, whether we'll 1197 // override them or not, or get message from the compiler: 1198 // oop_since_save_marks_iterate_nv hides virtual function... 1199 #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 1200 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 1201 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL) 1202 1203 // Smart allocation XXX -- move to CFLSpace? 1204 void setNearLargestChunk(); 1205 bool isNearLargestChunk(HeapWord* addr); 1206 1207 // Get the chunk at the end of the space. Delegates to 1208 // the space. 1209 FreeChunk* find_chunk_at_end(); 1210 1211 void post_compact(); 1212 1213 // Debugging 1214 void prepare_for_verify(); 1215 void verify(); 1216 void print_statistics() PRODUCT_RETURN; 1217 1218 // Performance Counters support 1219 virtual void update_counters(); 1220 virtual void update_counters(size_t used); 1221 void initialize_performance_counters(); 1222 CollectorCounters* counters() { return collector()->counters(); } 1223 1224 // Support for parallel remark of survivor space 1225 void* get_data_recorder(int thr_num) { 1226 //Delegate to collector 1227 return collector()->get_data_recorder(thr_num); 1228 } 1229 void sample_eden_chunk() { 1230 //Delegate to collector 1231 return collector()->sample_eden_chunk(); 1232 } 1233 1234 // Printing 1235 const char* name() const; 1236 virtual const char* short_name() const { return "CMS"; } 1237 void print() const; 1238 1239 // Resize the generation after a compacting GC. The 1240 // generation can be treated as a contiguous space 1241 // after the compaction. 1242 virtual void compute_new_size(); 1243 // Resize the generation after a non-compacting 1244 // collection. 1245 void compute_new_size_free_list(); 1246}; 1247 1248// 1249// Closures of various sorts used by CMS to accomplish its work 1250// 1251 1252// This closure is used to do concurrent marking from the roots 1253// following the first checkpoint. 1254class MarkFromRootsClosure: public BitMapClosure { 1255 CMSCollector* _collector; 1256 MemRegion _span; 1257 CMSBitMap* _bitMap; 1258 CMSBitMap* _mut; 1259 CMSMarkStack* _markStack; 1260 bool _yield; 1261 int _skipBits; 1262 HeapWord* _finger; 1263 HeapWord* _threshold; 1264 DEBUG_ONLY(bool _verifying;) 1265 1266 public: 1267 MarkFromRootsClosure(CMSCollector* collector, MemRegion span, 1268 CMSBitMap* bitMap, 1269 CMSMarkStack* markStack, 1270 bool should_yield, bool verifying = false); 1271 bool do_bit(size_t offset); 1272 void reset(HeapWord* addr); 1273 inline void do_yield_check(); 1274 1275 private: 1276 void scanOopsInOop(HeapWord* ptr); 1277 void do_yield_work(); 1278}; 1279 1280// This closure is used to do concurrent multi-threaded 1281// marking from the roots following the first checkpoint. 1282// XXX This should really be a subclass of The serial version 1283// above, but i have not had the time to refactor things cleanly. 1284class ParMarkFromRootsClosure: public BitMapClosure { 1285 CMSCollector* _collector; 1286 MemRegion _whole_span; 1287 MemRegion _span; 1288 CMSBitMap* _bit_map; 1289 CMSBitMap* _mut; 1290 OopTaskQueue* _work_queue; 1291 CMSMarkStack* _overflow_stack; 1292 int _skip_bits; 1293 HeapWord* _finger; 1294 HeapWord* _threshold; 1295 CMSConcMarkingTask* _task; 1296 public: 1297 ParMarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector, 1298 MemRegion span, 1299 CMSBitMap* bit_map, 1300 OopTaskQueue* work_queue, 1301 CMSMarkStack* overflow_stack); 1302 bool do_bit(size_t offset); 1303 inline void do_yield_check(); 1304 1305 private: 1306 void scan_oops_in_oop(HeapWord* ptr); 1307 void do_yield_work(); 1308 bool get_work_from_overflow_stack(); 1309}; 1310 1311// The following closures are used to do certain kinds of verification of 1312// CMS marking. 1313class PushAndMarkVerifyClosure: public MetadataAwareOopClosure { 1314 CMSCollector* _collector; 1315 MemRegion _span; 1316 CMSBitMap* _verification_bm; 1317 CMSBitMap* _cms_bm; 1318 CMSMarkStack* _mark_stack; 1319 protected: 1320 void do_oop(oop p); 1321 template <class T> inline void do_oop_work(T *p) { 1322 oop obj = oopDesc::load_decode_heap_oop(p); 1323 do_oop(obj); 1324 } 1325 public: 1326 PushAndMarkVerifyClosure(CMSCollector* cms_collector, 1327 MemRegion span, 1328 CMSBitMap* verification_bm, 1329 CMSBitMap* cms_bm, 1330 CMSMarkStack* mark_stack); 1331 void do_oop(oop* p); 1332 void do_oop(narrowOop* p); 1333 1334 // Deal with a stack overflow condition 1335 void handle_stack_overflow(HeapWord* lost); 1336}; 1337 1338class MarkFromRootsVerifyClosure: public BitMapClosure { 1339 CMSCollector* _collector; 1340 MemRegion _span; 1341 CMSBitMap* _verification_bm; 1342 CMSBitMap* _cms_bm; 1343 CMSMarkStack* _mark_stack; 1344 HeapWord* _finger; 1345 PushAndMarkVerifyClosure _pam_verify_closure; 1346 public: 1347 MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span, 1348 CMSBitMap* verification_bm, 1349 CMSBitMap* cms_bm, 1350 CMSMarkStack* mark_stack); 1351 bool do_bit(size_t offset); 1352 void reset(HeapWord* addr); 1353}; 1354 1355 1356// This closure is used to check that a certain set of bits is 1357// "empty" (i.e. the bit vector doesn't have any 1-bits). 1358class FalseBitMapClosure: public BitMapClosure { 1359 public: 1360 bool do_bit(size_t offset) { 1361 guarantee(false, "Should not have a 1 bit"); 1362 return true; 1363 } 1364}; 1365 1366// A version of ObjectClosure with "memory" (see _previous_address below) 1367class UpwardsObjectClosure: public BoolObjectClosure { 1368 HeapWord* _previous_address; 1369 public: 1370 UpwardsObjectClosure() : _previous_address(NULL) { } 1371 void set_previous(HeapWord* addr) { _previous_address = addr; } 1372 HeapWord* previous() { return _previous_address; } 1373 // A return value of "true" can be used by the caller to decide 1374 // if this object's end should *NOT* be recorded in 1375 // _previous_address above. 1376 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 1377}; 1378 1379// This closure is used during the second checkpointing phase 1380// to rescan the marked objects on the dirty cards in the mod 1381// union table and the card table proper. It's invoked via 1382// MarkFromDirtyCardsClosure below. It uses either 1383// [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case) 1384// declared in genOopClosures.hpp to accomplish some of its work. 1385// In the parallel case the bitMap is shared, so access to 1386// it needs to be suitably synchronized for updates by embedded 1387// closures that update it; however, this closure itself only 1388// reads the bit_map and because it is idempotent, is immune to 1389// reading stale values. 1390class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure { 1391 #ifdef ASSERT 1392 CMSCollector* _collector; 1393 MemRegion _span; 1394 union { 1395 CMSMarkStack* _mark_stack; 1396 OopTaskQueue* _work_queue; 1397 }; 1398 #endif // ASSERT 1399 bool _parallel; 1400 CMSBitMap* _bit_map; 1401 union { 1402 MarkRefsIntoAndScanClosure* _scan_closure; 1403 ParMarkRefsIntoAndScanClosure* _par_scan_closure; 1404 }; 1405 1406 public: 1407 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1408 MemRegion span, 1409 ReferenceProcessor* rp, 1410 CMSBitMap* bit_map, 1411 CMSMarkStack* mark_stack, 1412 MarkRefsIntoAndScanClosure* cl): 1413 #ifdef ASSERT 1414 _collector(collector), 1415 _span(span), 1416 _mark_stack(mark_stack), 1417 #endif // ASSERT 1418 _parallel(false), 1419 _bit_map(bit_map), 1420 _scan_closure(cl) { } 1421 1422 ScanMarkedObjectsAgainClosure(CMSCollector* collector, 1423 MemRegion span, 1424 ReferenceProcessor* rp, 1425 CMSBitMap* bit_map, 1426 OopTaskQueue* work_queue, 1427 ParMarkRefsIntoAndScanClosure* cl): 1428 #ifdef ASSERT 1429 _collector(collector), 1430 _span(span), 1431 _work_queue(work_queue), 1432 #endif // ASSERT 1433 _parallel(true), 1434 _bit_map(bit_map), 1435 _par_scan_closure(cl) { } 1436 1437 bool do_object_b(oop obj) { 1438 guarantee(false, "Call do_object_b(oop, MemRegion) form instead"); 1439 return false; 1440 } 1441 bool do_object_bm(oop p, MemRegion mr); 1442}; 1443 1444// This closure is used during the second checkpointing phase 1445// to rescan the marked objects on the dirty cards in the mod 1446// union table and the card table proper. It invokes 1447// ScanMarkedObjectsAgainClosure above to accomplish much of its work. 1448// In the parallel case, the bit map is shared and requires 1449// synchronized access. 1450class MarkFromDirtyCardsClosure: public MemRegionClosure { 1451 CompactibleFreeListSpace* _space; 1452 ScanMarkedObjectsAgainClosure _scan_cl; 1453 size_t _num_dirty_cards; 1454 1455 public: 1456 MarkFromDirtyCardsClosure(CMSCollector* collector, 1457 MemRegion span, 1458 CompactibleFreeListSpace* space, 1459 CMSBitMap* bit_map, 1460 CMSMarkStack* mark_stack, 1461 MarkRefsIntoAndScanClosure* cl): 1462 _space(space), 1463 _num_dirty_cards(0), 1464 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1465 mark_stack, cl) { } 1466 1467 MarkFromDirtyCardsClosure(CMSCollector* collector, 1468 MemRegion span, 1469 CompactibleFreeListSpace* space, 1470 CMSBitMap* bit_map, 1471 OopTaskQueue* work_queue, 1472 ParMarkRefsIntoAndScanClosure* cl): 1473 _space(space), 1474 _num_dirty_cards(0), 1475 _scan_cl(collector, span, collector->ref_processor(), bit_map, 1476 work_queue, cl) { } 1477 1478 void do_MemRegion(MemRegion mr); 1479 void set_space(CompactibleFreeListSpace* space) { _space = space; } 1480 size_t num_dirty_cards() { return _num_dirty_cards; } 1481}; 1482 1483// This closure is used in the non-product build to check 1484// that there are no MemRegions with a certain property. 1485class FalseMemRegionClosure: public MemRegionClosure { 1486 void do_MemRegion(MemRegion mr) { 1487 guarantee(!mr.is_empty(), "Shouldn't be empty"); 1488 guarantee(false, "Should never be here"); 1489 } 1490}; 1491 1492// This closure is used during the precleaning phase 1493// to "carefully" rescan marked objects on dirty cards. 1494// It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp 1495// to accomplish some of its work. 1496class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful { 1497 CMSCollector* _collector; 1498 MemRegion _span; 1499 bool _yield; 1500 Mutex* _freelistLock; 1501 CMSBitMap* _bitMap; 1502 CMSMarkStack* _markStack; 1503 MarkRefsIntoAndScanClosure* _scanningClosure; 1504 DEBUG_ONLY(HeapWord* _last_scanned_object;) 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 DEBUG_ONLY(COMMA _last_scanned_object(NULL)) 1520 { } 1521 1522 void do_object(oop p) { 1523 guarantee(false, "call do_object_careful instead"); 1524 } 1525 1526 size_t do_object_careful(oop p) { 1527 guarantee(false, "Unexpected caller"); 1528 return 0; 1529 } 1530 1531 size_t do_object_careful_m(oop p, MemRegion mr); 1532 1533 void setFreelistLock(Mutex* m) { 1534 _freelistLock = m; 1535 _scanningClosure->set_freelistLock(m); 1536 } 1537 1538 private: 1539 inline bool do_yield_check(); 1540 1541 void do_yield_work(); 1542}; 1543 1544class SurvivorSpacePrecleanClosure: public ObjectClosureCareful { 1545 CMSCollector* _collector; 1546 MemRegion _span; 1547 bool _yield; 1548 CMSBitMap* _bit_map; 1549 CMSMarkStack* _mark_stack; 1550 PushAndMarkClosure* _scanning_closure; 1551 unsigned int _before_count; 1552 1553 public: 1554 SurvivorSpacePrecleanClosure(CMSCollector* collector, 1555 MemRegion span, 1556 CMSBitMap* bit_map, 1557 CMSMarkStack* mark_stack, 1558 PushAndMarkClosure* cl, 1559 unsigned int before_count, 1560 bool should_yield): 1561 _collector(collector), 1562 _span(span), 1563 _yield(should_yield), 1564 _bit_map(bit_map), 1565 _mark_stack(mark_stack), 1566 _scanning_closure(cl), 1567 _before_count(before_count) 1568 { } 1569 1570 void do_object(oop p) { 1571 guarantee(false, "call do_object_careful instead"); 1572 } 1573 1574 size_t do_object_careful(oop p); 1575 1576 size_t do_object_careful_m(oop p, MemRegion mr) { 1577 guarantee(false, "Unexpected caller"); 1578 return 0; 1579 } 1580 1581 private: 1582 inline void do_yield_check(); 1583 void do_yield_work(); 1584}; 1585 1586// This closure is used to accomplish the sweeping work 1587// after the second checkpoint but before the concurrent reset 1588// phase. 1589// 1590// Terminology 1591// left hand chunk (LHC) - block of one or more chunks currently being 1592// coalesced. The LHC is available for coalescing with a new chunk. 1593// right hand chunk (RHC) - block that is currently being swept that is 1594// free or garbage that can be coalesced with the LHC. 1595// _inFreeRange is true if there is currently a LHC 1596// _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk. 1597// _freeRangeInFreeLists is true if the LHC is in the free lists. 1598// _freeFinger is the address of the current LHC 1599class SweepClosure: public BlkClosureCareful { 1600 CMSCollector* _collector; // collector doing the work 1601 ConcurrentMarkSweepGeneration* _g; // Generation being swept 1602 CompactibleFreeListSpace* _sp; // Space being swept 1603 HeapWord* _limit;// the address at or above which the sweep should stop 1604 // because we do not expect newly garbage blocks 1605 // eligible for sweeping past that address. 1606 Mutex* _freelistLock; // Free list lock (in space) 1607 CMSBitMap* _bitMap; // Marking bit map (in 1608 // generation) 1609 bool _inFreeRange; // Indicates if we are in the 1610 // midst of a free run 1611 bool _freeRangeInFreeLists; 1612 // Often, we have just found 1613 // a free chunk and started 1614 // a new free range; we do not 1615 // eagerly remove this chunk from 1616 // the free lists unless there is 1617 // a possibility of coalescing. 1618 // When true, this flag indicates 1619 // that the _freeFinger below 1620 // points to a potentially free chunk 1621 // that may still be in the free lists 1622 bool _lastFreeRangeCoalesced; 1623 // free range contains chunks 1624 // coalesced 1625 bool _yield; 1626 // Whether sweeping should be 1627 // done with yields. For instance 1628 // when done by the foreground 1629 // collector we shouldn't yield. 1630 HeapWord* _freeFinger; // When _inFreeRange is set, the 1631 // pointer to the "left hand 1632 // chunk" 1633 size_t _freeRangeSize; 1634 // When _inFreeRange is set, this 1635 // indicates the accumulated size 1636 // of the "left hand chunk" 1637 NOT_PRODUCT( 1638 size_t _numObjectsFreed; 1639 size_t _numWordsFreed; 1640 size_t _numObjectsLive; 1641 size_t _numWordsLive; 1642 size_t _numObjectsAlreadyFree; 1643 size_t _numWordsAlreadyFree; 1644 FreeChunk* _last_fc; 1645 ) 1646 private: 1647 // Code that is common to a free chunk or garbage when 1648 // encountered during sweeping. 1649 void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize); 1650 // Process a free chunk during sweeping. 1651 void do_already_free_chunk(FreeChunk *fc); 1652 // Work method called when processing an already free or a 1653 // freshly garbage chunk to do a lookahead and possibly a 1654 // preemptive flush if crossing over _limit. 1655 void lookahead_and_flush(FreeChunk* fc, size_t chunkSize); 1656 // Process a garbage chunk during sweeping. 1657 size_t do_garbage_chunk(FreeChunk *fc); 1658 // Process a live chunk during sweeping. 1659 size_t do_live_chunk(FreeChunk* fc); 1660 1661 // Accessors. 1662 HeapWord* freeFinger() const { return _freeFinger; } 1663 void set_freeFinger(HeapWord* v) { _freeFinger = v; } 1664 bool inFreeRange() const { return _inFreeRange; } 1665 void set_inFreeRange(bool v) { _inFreeRange = v; } 1666 bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; } 1667 void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; } 1668 bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; } 1669 void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; } 1670 1671 // Initialize a free range. 1672 void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists); 1673 // Return this chunk to the free lists. 1674 void flush_cur_free_chunk(HeapWord* chunk, size_t size); 1675 1676 // Check if we should yield and do so when necessary. 1677 inline void do_yield_check(HeapWord* addr); 1678 1679 // Yield 1680 void do_yield_work(HeapWord* addr); 1681 1682 // Debugging/Printing 1683 void print_free_block_coalesced(FreeChunk* fc) const; 1684 1685 public: 1686 SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g, 1687 CMSBitMap* bitMap, bool should_yield); 1688 ~SweepClosure() PRODUCT_RETURN; 1689 1690 size_t do_blk_careful(HeapWord* addr); 1691 void print() const { print_on(tty); } 1692 void print_on(outputStream *st) const; 1693}; 1694 1695// Closures related to weak references processing 1696 1697// During CMS' weak reference processing, this is a 1698// work-routine/closure used to complete transitive 1699// marking of objects as live after a certain point 1700// in which an initial set has been completely accumulated. 1701// This closure is currently used both during the final 1702// remark stop-world phase, as well as during the concurrent 1703// precleaning of the discovered reference lists. 1704class CMSDrainMarkingStackClosure: public VoidClosure { 1705 CMSCollector* _collector; 1706 MemRegion _span; 1707 CMSMarkStack* _mark_stack; 1708 CMSBitMap* _bit_map; 1709 CMSKeepAliveClosure* _keep_alive; 1710 bool _concurrent_precleaning; 1711 public: 1712 CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span, 1713 CMSBitMap* bit_map, CMSMarkStack* mark_stack, 1714 CMSKeepAliveClosure* keep_alive, 1715 bool cpc): 1716 _collector(collector), 1717 _span(span), 1718 _bit_map(bit_map), 1719 _mark_stack(mark_stack), 1720 _keep_alive(keep_alive), 1721 _concurrent_precleaning(cpc) { 1722 assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(), 1723 "Mismatch"); 1724 } 1725 1726 void do_void(); 1727}; 1728 1729// A parallel version of CMSDrainMarkingStackClosure above. 1730class CMSParDrainMarkingStackClosure: public VoidClosure { 1731 CMSCollector* _collector; 1732 MemRegion _span; 1733 OopTaskQueue* _work_queue; 1734 CMSBitMap* _bit_map; 1735 CMSInnerParMarkAndPushClosure _mark_and_push; 1736 1737 public: 1738 CMSParDrainMarkingStackClosure(CMSCollector* collector, 1739 MemRegion span, CMSBitMap* bit_map, 1740 OopTaskQueue* work_queue): 1741 _collector(collector), 1742 _span(span), 1743 _bit_map(bit_map), 1744 _work_queue(work_queue), 1745 _mark_and_push(collector, span, bit_map, work_queue) { } 1746 1747 public: 1748 void trim_queue(uint max); 1749 void do_void(); 1750}; 1751 1752// Allow yielding or short-circuiting of reference list 1753// precleaning work. 1754class CMSPrecleanRefsYieldClosure: public YieldClosure { 1755 CMSCollector* _collector; 1756 void do_yield_work(); 1757 public: 1758 CMSPrecleanRefsYieldClosure(CMSCollector* collector): 1759 _collector(collector) {} 1760 virtual bool should_return(); 1761}; 1762 1763 1764// Convenience class that locks free list locks for given CMS collector 1765class FreelistLocker: public StackObj { 1766 private: 1767 CMSCollector* _collector; 1768 public: 1769 FreelistLocker(CMSCollector* collector): 1770 _collector(collector) { 1771 _collector->getFreelistLocks(); 1772 } 1773 1774 ~FreelistLocker() { 1775 _collector->releaseFreelistLocks(); 1776 } 1777}; 1778 1779// Mark all dead objects in a given space. 1780class MarkDeadObjectsClosure: public BlkClosure { 1781 const CMSCollector* _collector; 1782 const CompactibleFreeListSpace* _sp; 1783 CMSBitMap* _live_bit_map; 1784 CMSBitMap* _dead_bit_map; 1785public: 1786 MarkDeadObjectsClosure(const CMSCollector* collector, 1787 const CompactibleFreeListSpace* sp, 1788 CMSBitMap *live_bit_map, 1789 CMSBitMap *dead_bit_map) : 1790 _collector(collector), 1791 _sp(sp), 1792 _live_bit_map(live_bit_map), 1793 _dead_bit_map(dead_bit_map) {} 1794 size_t do_blk(HeapWord* addr); 1795}; 1796 1797class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats { 1798 1799 public: 1800 TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause); 1801}; 1802 1803 1804#endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP 1805