1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP 27 28 #include "classfile/javaClasses.hpp" 29 #include "gc_implementation/g1/heapRegionSet.hpp" 30 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" 31 #include "gc_implementation/shared/gcId.hpp" 32 #include "utilities/taskqueue.hpp" 33 34 class G1CollectedHeap; 35 class CMBitMap; 36 class CMTask; 37 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue; 38 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet; 39 40 // Closure used by CM during concurrent reference discovery 41 // and reference processing (during remarking) to determine 42 // if a particular object is alive. It is primarily used 43 // to determine if referents of discovered reference objects 44 // are alive. An instance is also embedded into the 45 // reference processor as the _is_alive_non_header field 46 class G1CMIsAliveClosure: public BoolObjectClosure { 47 G1CollectedHeap* _g1; 48 public: 49 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { } 50 51 bool do_object_b(oop obj); 52 }; 53 54 // A generic CM bit map. This is essentially a wrapper around the BitMap 55 // class, with one bit per (1<<_shifter) HeapWords. 56 57 class CMBitMapRO VALUE_OBJ_CLASS_SPEC { 58 protected: 59 HeapWord* _bmStartWord; // base address of range covered by map 60 size_t _bmWordSize; // map size (in #HeapWords covered) 61 const int _shifter; // map to char or bit 62 BitMap _bm; // the bit map itself 63 64 public: 65 // constructor 66 CMBitMapRO(int shifter); 67 68 enum { do_yield = true }; 69 70 // inquiries 71 HeapWord* startWord() const { return _bmStartWord; } 72 size_t sizeInWords() const { return _bmWordSize; } 73 // the following is one past the last word in space 74 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 75 76 // read marks 77 78 bool isMarked(HeapWord* addr) const { 79 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 80 "outside underlying space?"); 81 return _bm.at(heapWordToOffset(addr)); 82 } 83 84 // iteration 85 inline bool iterate(BitMapClosure* cl, MemRegion mr); 86 inline bool iterate(BitMapClosure* cl); 87 88 // Return the address corresponding to the next marked bit at or after 89 // "addr", and before "limit", if "limit" is non-NULL. If there is no 90 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 91 HeapWord* getNextMarkedWordAddress(const HeapWord* addr, 92 const HeapWord* limit = NULL) const; 93 // Return the address corresponding to the next unmarked bit at or after 94 // "addr", and before "limit", if "limit" is non-NULL. If there is no 95 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 96 HeapWord* getNextUnmarkedWordAddress(const HeapWord* addr, 97 const HeapWord* limit = NULL) const; 98 99 // conversion utilities 100 HeapWord* offsetToHeapWord(size_t offset) const { 101 return _bmStartWord + (offset << _shifter); 102 } 103 size_t heapWordToOffset(const HeapWord* addr) const { 104 return pointer_delta(addr, _bmStartWord) >> _shifter; 105 } 106 int heapWordDiffToOffsetDiff(size_t diff) const; 107 108 // The argument addr should be the start address of a valid object 109 HeapWord* nextObject(HeapWord* addr) { 110 oop obj = (oop) addr; 111 HeapWord* res = addr + obj->size(); 112 assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity"); 113 return res; 114 } 115 116 void print_on_error(outputStream* st, const char* prefix) const; 117 118 // debugging 119 NOT_PRODUCT(bool covers(MemRegion rs) const;) 120 }; 121 122 class CMBitMapMappingChangedListener : public G1MappingChangedListener { 123 private: 124 CMBitMap* _bm; 125 public: 126 CMBitMapMappingChangedListener() : _bm(NULL) {} 127 128 void set_bitmap(CMBitMap* bm) { _bm = bm; } 129 130 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 131 }; 132 133 class CMBitMap : public CMBitMapRO { 134 private: 135 CMBitMapMappingChangedListener _listener; 136 137 public: 138 static size_t compute_size(size_t heap_size); 139 // Returns the amount of bytes on the heap between two marks in the bitmap. 140 static size_t mark_distance(); 141 142 CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); } 143 144 // Initializes the underlying BitMap to cover the given area. 145 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage); 146 147 // Write marks. 148 inline void mark(HeapWord* addr); 149 inline void clear(HeapWord* addr); 150 inline bool parMark(HeapWord* addr); 151 inline bool parClear(HeapWord* addr); 152 153 void markRange(MemRegion mr); 154 void clearRange(MemRegion mr); 155 156 // Starting at the bit corresponding to "addr" (inclusive), find the next 157 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find 158 // the end of this run (stopping at "end_addr"). Return the MemRegion 159 // covering from the start of the region corresponding to the first bit 160 // of the run to the end of the region corresponding to the last bit of 161 // the run. If there is no "1" bit at or after "addr", return an empty 162 // MemRegion. 163 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr); 164 165 // Clear the whole mark bitmap. 166 void clearAll(); 167 }; 168 169 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 170 class CMMarkStack VALUE_OBJ_CLASS_SPEC { 171 VirtualSpace _virtual_space; // Underlying backing store for actual stack 172 ConcurrentMark* _cm; 173 oop* _base; // bottom of stack 174 jint _index; // one more than last occupied index 175 jint _capacity; // max #elements 176 jint _saved_index; // value of _index saved at start of GC 177 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run 178 179 bool _overflow; 180 bool _should_expand; 181 DEBUG_ONLY(bool _drain_in_progress;) 182 DEBUG_ONLY(bool _drain_in_progress_yields;) 183 184 public: 185 CMMarkStack(ConcurrentMark* cm); 186 ~CMMarkStack(); 187 188 #ifndef PRODUCT 189 jint max_depth() const { 190 return _max_depth; 191 } 192 #endif 193 194 bool allocate(size_t capacity); 195 196 oop pop() { 197 if (!isEmpty()) { 198 return _base[--_index] ; 199 } 200 return NULL; 201 } 202 203 // If overflow happens, don't do the push, and record the overflow. 204 // *Requires* that "ptr" is already marked. 205 void push(oop ptr) { 206 if (isFull()) { 207 // Record overflow. 208 _overflow = true; 209 return; 210 } else { 211 _base[_index++] = ptr; 212 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 213 } 214 } 215 // Non-block impl. Note: concurrency is allowed only with other 216 // "par_push" operations, not with "pop" or "drain". We would need 217 // parallel versions of them if such concurrency was desired. 218 void par_push(oop ptr); 219 220 // Pushes the first "n" elements of "ptr_arr" on the stack. 221 // Non-block impl. Note: concurrency is allowed only with other 222 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain". 223 void par_adjoin_arr(oop* ptr_arr, int n); 224 225 // Pushes the first "n" elements of "ptr_arr" on the stack. 226 // Locking impl: concurrency is allowed only with 227 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 228 // locking strategy. 229 void par_push_arr(oop* ptr_arr, int n); 230 231 // If returns false, the array was empty. Otherwise, removes up to "max" 232 // elements from the stack, and transfers them to "ptr_arr" in an 233 // unspecified order. The actual number transferred is given in "n" ("n 234 // == 0" is deliberately redundant with the return value.) Locking impl: 235 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 236 // operations, which use the same locking strategy. 237 bool par_pop_arr(oop* ptr_arr, int max, int* n); 238 239 // Drain the mark stack, applying the given closure to all fields of 240 // objects on the stack. (That is, continue until the stack is empty, 241 // even if closure applications add entries to the stack.) The "bm" 242 // argument, if non-null, may be used to verify that only marked objects 243 // are on the mark stack. If "yield_after" is "true", then the 244 // concurrent marker performing the drain offers to yield after 245 // processing each object. If a yield occurs, stops the drain operation 246 // and returns false. Otherwise, returns true. 247 template<class OopClosureClass> 248 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false); 249 250 bool isEmpty() { return _index == 0; } 251 bool isFull() { return _index == _capacity; } 252 int maxElems() { return _capacity; } 253 254 bool overflow() { return _overflow; } 255 void clear_overflow() { _overflow = false; } 256 257 bool should_expand() const { return _should_expand; } 258 void set_should_expand(); 259 260 // Expand the stack, typically in response to an overflow condition 261 void expand(); 262 263 int size() { return _index; } 264 265 void setEmpty() { _index = 0; clear_overflow(); } 266 267 // Record the current index. 268 void note_start_of_gc(); 269 270 // Make sure that we have not added any entries to the stack during GC. 271 void note_end_of_gc(); 272 273 // iterate over the oops in the mark stack, up to the bound recorded via 274 // the call above. 275 void oops_do(OopClosure* f); 276 }; 277 278 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC { 279 private: 280 #ifndef PRODUCT 281 uintx _num_remaining; 282 bool _force; 283 #endif // !defined(PRODUCT) 284 285 public: 286 void init() PRODUCT_RETURN; 287 void update() PRODUCT_RETURN; 288 bool should_force() PRODUCT_RETURN_( return false; ); 289 }; 290 291 // this will enable a variety of different statistics per GC task 292 #define _MARKING_STATS_ 0 293 // this will enable the higher verbose levels 294 #define _MARKING_VERBOSE_ 0 295 296 #if _MARKING_STATS_ 297 #define statsOnly(statement) \ 298 do { \ 299 statement ; \ 300 } while (0) 301 #else // _MARKING_STATS_ 302 #define statsOnly(statement) \ 303 do { \ 304 } while (0) 305 #endif // _MARKING_STATS_ 306 307 typedef enum { 308 no_verbose = 0, // verbose turned off 309 stats_verbose, // only prints stats at the end of marking 310 low_verbose, // low verbose, mostly per region and per major event 311 medium_verbose, // a bit more detailed than low 312 high_verbose // per object verbose 313 } CMVerboseLevel; 314 315 class YoungList; 316 317 // Root Regions are regions that are not empty at the beginning of a 318 // marking cycle and which we might collect during an evacuation pause 319 // while the cycle is active. Given that, during evacuation pauses, we 320 // do not copy objects that are explicitly marked, what we have to do 321 // for the root regions is to scan them and mark all objects reachable 322 // from them. According to the SATB assumptions, we only need to visit 323 // each object once during marking. So, as long as we finish this scan 324 // before the next evacuation pause, we can copy the objects from the 325 // root regions without having to mark them or do anything else to them. 326 // 327 // Currently, we only support root region scanning once (at the start 328 // of the marking cycle) and the root regions are all the survivor 329 // regions populated during the initial-mark pause. 330 class CMRootRegions VALUE_OBJ_CLASS_SPEC { 331 private: 332 YoungList* _young_list; 333 ConcurrentMark* _cm; 334 335 volatile bool _scan_in_progress; 336 volatile bool _should_abort; 337 HeapRegion* volatile _next_survivor; 338 339 public: 340 CMRootRegions(); 341 // We actually do most of the initialization in this method. 342 void init(G1CollectedHeap* g1h, ConcurrentMark* cm); 343 344 // Reset the claiming / scanning of the root regions. 345 void prepare_for_scan(); 346 347 // Forces get_next() to return NULL so that the iteration aborts early. 348 void abort() { _should_abort = true; } 349 350 // Return true if the CM thread are actively scanning root regions, 351 // false otherwise. 352 bool scan_in_progress() { return _scan_in_progress; } 353 354 // Claim the next root region to scan atomically, or return NULL if 355 // all have been claimed. 356 HeapRegion* claim_next(); 357 358 // Flag that we're done with root region scanning and notify anyone 359 // who's waiting on it. If aborted is false, assume that all regions 360 // have been claimed. 361 void scan_finished(); 362 363 // If CM threads are still scanning root regions, wait until they 364 // are done. Return true if we had to wait, false otherwise. 365 bool wait_until_scan_finished(); 366 }; 367 368 class ConcurrentMarkThread; 369 370 class ConcurrentMark: public CHeapObj<mtGC> { 371 friend class CMMarkStack; 372 friend class ConcurrentMarkThread; 373 friend class CMTask; 374 friend class CMBitMapClosure; 375 friend class CMGlobalObjectClosure; 376 friend class CMRemarkTask; 377 friend class CMConcurrentMarkingTask; 378 friend class G1ParNoteEndTask; 379 friend class CalcLiveObjectsClosure; 380 friend class G1CMRefProcTaskProxy; 381 friend class G1CMRefProcTaskExecutor; 382 friend class G1CMKeepAliveAndDrainClosure; 383 friend class G1CMDrainMarkingStackClosure; 384 385 protected: 386 ConcurrentMarkThread* _cmThread; // The thread doing the work 387 G1CollectedHeap* _g1h; // The heap 388 uint _parallel_marking_threads; // The number of marking 389 // threads we're using 390 uint _max_parallel_marking_threads; // Max number of marking 391 // threads we'll ever use 392 double _sleep_factor; // How much we have to sleep, with 393 // respect to the work we just did, to 394 // meet the marking overhead goal 395 double _marking_task_overhead; // Marking target overhead for 396 // a single task 397 398 // Same as the two above, but for the cleanup task 399 double _cleanup_sleep_factor; 400 double _cleanup_task_overhead; 401 402 FreeRegionList _cleanup_list; 403 404 // Concurrent marking support structures 405 CMBitMap _markBitMap1; 406 CMBitMap _markBitMap2; 407 CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap 408 CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap 409 410 BitMap _region_bm; 411 BitMap _card_bm; 412 413 // Heap bounds 414 HeapWord* _heap_start; 415 HeapWord* _heap_end; 416 417 // Root region tracking and claiming 418 CMRootRegions _root_regions; 419 420 // For gray objects 421 CMMarkStack _markStack; // Grey objects behind global finger 422 HeapWord* volatile _finger; // The global finger, region aligned, 423 // always points to the end of the 424 // last claimed region 425 426 // Marking tasks 427 uint _max_worker_id;// Maximum worker id 428 uint _active_tasks; // Task num currently active 429 CMTask** _tasks; // Task queue array (max_worker_id len) 430 CMTaskQueueSet* _task_queues; // Task queue set 431 ParallelTaskTerminator _terminator; // For termination 432 433 // Two sync barriers that are used to synchronize tasks when an 434 // overflow occurs. The algorithm is the following. All tasks enter 435 // the first one to ensure that they have all stopped manipulating 436 // the global data structures. After they exit it, they re-initialize 437 // their data structures and task 0 re-initializes the global data 438 // structures. Then, they enter the second sync barrier. This 439 // ensure, that no task starts doing work before all data 440 // structures (local and global) have been re-initialized. When they 441 // exit it, they are free to start working again. 442 WorkGangBarrierSync _first_overflow_barrier_sync; 443 WorkGangBarrierSync _second_overflow_barrier_sync; 444 445 // This is set by any task, when an overflow on the global data 446 // structures is detected 447 volatile bool _has_overflown; 448 // True: marking is concurrent, false: we're in remark 449 volatile bool _concurrent; 450 // Set at the end of a Full GC so that marking aborts 451 volatile bool _has_aborted; 452 GCId _aborted_gc_id; 453 454 // Used when remark aborts due to an overflow to indicate that 455 // another concurrent marking phase should start 456 volatile bool _restart_for_overflow; 457 458 // This is true from the very start of concurrent marking until the 459 // point when all the tasks complete their work. It is really used 460 // to determine the points between the end of concurrent marking and 461 // time of remark. 462 volatile bool _concurrent_marking_in_progress; 463 464 // Verbose level 465 CMVerboseLevel _verbose_level; 466 467 // All of these times are in ms 468 NumberSeq _init_times; 469 NumberSeq _remark_times; 470 NumberSeq _remark_mark_times; 471 NumberSeq _remark_weak_ref_times; 472 NumberSeq _cleanup_times; 473 double _total_counting_time; 474 double _total_rs_scrub_time; 475 476 double* _accum_task_vtime; // Accumulated task vtime 477 478 FlexibleWorkGang* _parallel_workers; 479 480 ForceOverflowSettings _force_overflow_conc; 481 ForceOverflowSettings _force_overflow_stw; 482 483 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes); 484 void weakRefsWork(bool clear_all_soft_refs); 485 486 void swapMarkBitMaps(); 487 488 // It resets the global marking data structures, as well as the 489 // task local ones; should be called during initial mark. 490 void reset(); 491 492 // Resets all the marking data structures. Called when we have to restart 493 // marking or when marking completes (via set_non_marking_state below). 494 void reset_marking_state(bool clear_overflow = true); 495 496 // We do this after we're done with marking so that the marking data 497 // structures are initialized to a sensible and predictable state. 498 void set_non_marking_state(); 499 500 // Called to indicate how many threads are currently active. 501 void set_concurrency(uint active_tasks); 502 503 // It should be called to indicate which phase we're in (concurrent 504 // mark or remark) and how many threads are currently active. 505 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 506 507 // Prints all gathered CM-related statistics 508 void print_stats(); 509 510 bool cleanup_list_is_empty() { 511 return _cleanup_list.is_empty(); 512 } 513 514 // Accessor methods 515 uint parallel_marking_threads() const { return _parallel_marking_threads; } 516 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 517 double sleep_factor() { return _sleep_factor; } 518 double marking_task_overhead() { return _marking_task_overhead;} 519 double cleanup_sleep_factor() { return _cleanup_sleep_factor; } 520 double cleanup_task_overhead() { return _cleanup_task_overhead;} 521 522 HeapWord* finger() { return _finger; } 523 bool concurrent() { return _concurrent; } 524 uint active_tasks() { return _active_tasks; } 525 ParallelTaskTerminator* terminator() { return &_terminator; } 526 527 // It claims the next available region to be scanned by a marking 528 // task/thread. It might return NULL if the next region is empty or 529 // we have run out of regions. In the latter case, out_of_regions() 530 // determines whether we've really run out of regions or the task 531 // should call claim_region() again. This might seem a bit 532 // awkward. Originally, the code was written so that claim_region() 533 // either successfully returned with a non-empty region or there 534 // were no more regions to be claimed. The problem with this was 535 // that, in certain circumstances, it iterated over large chunks of 536 // the heap finding only empty regions and, while it was working, it 537 // was preventing the calling task to call its regular clock 538 // method. So, this way, each task will spend very little time in 539 // claim_region() and is allowed to call the regular clock method 540 // frequently. 541 HeapRegion* claim_region(uint worker_id); 542 543 // It determines whether we've run out of regions to scan. Note that 544 // the finger can point past the heap end in case the heap was expanded 545 // to satisfy an allocation without doing a GC. This is fine, because all 546 // objects in those regions will be considered live anyway because of 547 // SATB guarantees (i.e. their TAMS will be equal to bottom). 548 bool out_of_regions() { return _finger >= _heap_end; } 549 550 // Returns the task with the given id 551 CMTask* task(int id) { 552 assert(0 <= id && id < (int) _active_tasks, 553 "task id not within active bounds"); 554 return _tasks[id]; 555 } 556 557 // Returns the task queue with the given id 558 CMTaskQueue* task_queue(int id) { 559 assert(0 <= id && id < (int) _active_tasks, 560 "task queue id not within active bounds"); 561 return (CMTaskQueue*) _task_queues->queue(id); 562 } 563 564 // Returns the task queue set 565 CMTaskQueueSet* task_queues() { return _task_queues; } 566 567 // Access / manipulation of the overflow flag which is set to 568 // indicate that the global stack has overflown 569 bool has_overflown() { return _has_overflown; } 570 void set_has_overflown() { _has_overflown = true; } 571 void clear_has_overflown() { _has_overflown = false; } 572 bool restart_for_overflow() { return _restart_for_overflow; } 573 574 // Methods to enter the two overflow sync barriers 575 void enter_first_sync_barrier(uint worker_id); 576 void enter_second_sync_barrier(uint worker_id); 577 578 ForceOverflowSettings* force_overflow_conc() { 579 return &_force_overflow_conc; 580 } 581 582 ForceOverflowSettings* force_overflow_stw() { 583 return &_force_overflow_stw; 584 } 585 586 ForceOverflowSettings* force_overflow() { 587 if (concurrent()) { 588 return force_overflow_conc(); 589 } else { 590 return force_overflow_stw(); 591 } 592 } 593 594 // Live Data Counting data structures... 595 // These data structures are initialized at the start of 596 // marking. They are written to while marking is active. 597 // They are aggregated during remark; the aggregated values 598 // are then used to populate the _region_bm, _card_bm, and 599 // the total live bytes, which are then subsequently updated 600 // during cleanup. 601 602 // An array of bitmaps (one bit map per task). Each bitmap 603 // is used to record the cards spanned by the live objects 604 // marked by that task/worker. 605 BitMap* _count_card_bitmaps; 606 607 // Used to record the number of marked live bytes 608 // (for each region, by worker thread). 609 size_t** _count_marked_bytes; 610 611 // Card index of the bottom of the G1 heap. Used for biasing indices into 612 // the card bitmaps. 613 intptr_t _heap_bottom_card_num; 614 615 // Set to true when initialization is complete 616 bool _completed_initialization; 617 618 public: 619 // Manipulation of the global mark stack. 620 // Notice that the first mark_stack_push is CAS-based, whereas the 621 // two below are Mutex-based. This is OK since the first one is only 622 // called during evacuation pauses and doesn't compete with the 623 // other two (which are called by the marking tasks during 624 // concurrent marking or remark). 625 bool mark_stack_push(oop p) { 626 _markStack.par_push(p); 627 if (_markStack.overflow()) { 628 set_has_overflown(); 629 return false; 630 } 631 return true; 632 } 633 bool mark_stack_push(oop* arr, int n) { 634 _markStack.par_push_arr(arr, n); 635 if (_markStack.overflow()) { 636 set_has_overflown(); 637 return false; 638 } 639 return true; 640 } 641 void mark_stack_pop(oop* arr, int max, int* n) { 642 _markStack.par_pop_arr(arr, max, n); 643 } 644 size_t mark_stack_size() { return _markStack.size(); } 645 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 646 bool mark_stack_overflow() { return _markStack.overflow(); } 647 bool mark_stack_empty() { return _markStack.isEmpty(); } 648 649 CMRootRegions* root_regions() { return &_root_regions; } 650 651 bool concurrent_marking_in_progress() { 652 return _concurrent_marking_in_progress; 653 } 654 void set_concurrent_marking_in_progress() { 655 _concurrent_marking_in_progress = true; 656 } 657 void clear_concurrent_marking_in_progress() { 658 _concurrent_marking_in_progress = false; 659 } 660 661 void update_accum_task_vtime(int i, double vtime) { 662 _accum_task_vtime[i] += vtime; 663 } 664 665 double all_task_accum_vtime() { 666 double ret = 0.0; 667 for (uint i = 0; i < _max_worker_id; ++i) 668 ret += _accum_task_vtime[i]; 669 return ret; 670 } 671 672 // Attempts to steal an object from the task queues of other tasks 673 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) { 674 return _task_queues->steal(worker_id, hash_seed, obj); 675 } 676 677 ConcurrentMark(G1CollectedHeap* g1h, 678 G1RegionToSpaceMapper* prev_bitmap_storage, 679 G1RegionToSpaceMapper* next_bitmap_storage); 680 ~ConcurrentMark(); 681 682 ConcurrentMarkThread* cmThread() { return _cmThread; } 683 684 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 685 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 686 687 // Returns the number of GC threads to be used in a concurrent 688 // phase based on the number of GC threads being used in a STW 689 // phase. 690 uint scale_parallel_threads(uint n_par_threads); 691 692 // Calculates the number of GC threads to be used in a concurrent phase. 693 uint calc_parallel_marking_threads(); 694 695 // The following three are interaction between CM and 696 // G1CollectedHeap 697 698 // This notifies CM that a root during initial-mark needs to be 699 // grayed. It is MT-safe. word_size is the size of the object in 700 // words. It is passed explicitly as sometimes we cannot calculate 701 // it from the given object because it might be in an inconsistent 702 // state (e.g., in to-space and being copied). So the caller is 703 // responsible for dealing with this issue (e.g., get the size from 704 // the from-space image when the to-space image might be 705 // inconsistent) and always passing the size. hr is the region that 706 // contains the object and it's passed optionally from callers who 707 // might already have it (no point in recalculating it). 708 inline void grayRoot(oop obj, 709 size_t word_size, 710 uint worker_id, 711 HeapRegion* hr = NULL); 712 713 // It iterates over the heap and for each object it comes across it 714 // will dump the contents of its reference fields, as well as 715 // liveness information for the object and its referents. The dump 716 // will be written to a file with the following name: 717 // G1PrintReachableBaseFile + "." + str. 718 // vo decides whether the prev (vo == UsePrevMarking), the next 719 // (vo == UseNextMarking) marking information, or the mark word 720 // (vo == UseMarkWord) will be used to determine the liveness of 721 // each object / referent. 722 // If all is true, all objects in the heap will be dumped, otherwise 723 // only the live ones. In the dump the following symbols / breviations 724 // are used: 725 // M : an explicitly live object (its bitmap bit is set) 726 // > : an implicitly live object (over tams) 727 // O : an object outside the G1 heap (typically: in the perm gen) 728 // NOT : a reference field whose referent is not live 729 // AND MARKED : indicates that an object is both explicitly and 730 // implicitly live (it should be one or the other, not both) 731 void print_reachable(const char* str, 732 VerifyOption vo, 733 bool all) PRODUCT_RETURN; 734 735 // Clear the next marking bitmap (will be called concurrently). 736 void clearNextBitmap(); 737 738 // Return whether the next mark bitmap has no marks set. To be used for assertions 739 // only. Will not yield to pause requests. 740 bool nextMarkBitmapIsClear(); 741 742 // These two do the work that needs to be done before and after the 743 // initial root checkpoint. Since this checkpoint can be done at two 744 // different points (i.e. an explicit pause or piggy-backed on a 745 // young collection), then it's nice to be able to easily share the 746 // pre/post code. It might be the case that we can put everything in 747 // the post method. TP 748 void checkpointRootsInitialPre(); 749 void checkpointRootsInitialPost(); 750 751 // Scan all the root regions and mark everything reachable from 752 // them. 753 void scanRootRegions(); 754 755 // Scan a single root region and mark everything reachable from it. 756 void scanRootRegion(HeapRegion* hr, uint worker_id); 757 758 // Do concurrent phase of marking, to a tentative transitive closure. 759 void markFromRoots(); 760 761 void checkpointRootsFinal(bool clear_all_soft_refs); 762 void checkpointRootsFinalWork(); 763 void cleanup(); 764 void completeCleanup(); 765 766 // Mark in the previous bitmap. NB: this is usually read-only, so use 767 // this carefully! 768 inline void markPrev(oop p); 769 770 // Clears marks for all objects in the given range, for the prev or 771 // next bitmaps. NB: the previous bitmap is usually 772 // read-only, so use this carefully! 773 void clearRangePrevBitmap(MemRegion mr); 774 void clearRangeNextBitmap(MemRegion mr); 775 776 // Notify data structures that a GC has started. 777 void note_start_of_gc() { 778 _markStack.note_start_of_gc(); 779 } 780 781 // Notify data structures that a GC is finished. 782 void note_end_of_gc() { 783 _markStack.note_end_of_gc(); 784 } 785 786 // Verify that there are no CSet oops on the stacks (taskqueues / 787 // global mark stack), enqueued SATB buffers, per-thread SATB 788 // buffers, and fingers (global / per-task). The boolean parameters 789 // decide which of the above data structures to verify. If marking 790 // is not in progress, it's a no-op. 791 void verify_no_cset_oops(bool verify_stacks, 792 bool verify_enqueued_buffers, 793 bool verify_thread_buffers, 794 bool verify_fingers) PRODUCT_RETURN; 795 796 bool isPrevMarked(oop p) const { 797 assert(p != NULL && p->is_oop(), "expected an oop"); 798 HeapWord* addr = (HeapWord*)p; 799 assert(addr >= _prevMarkBitMap->startWord() || 800 addr < _prevMarkBitMap->endWord(), "in a region"); 801 802 return _prevMarkBitMap->isMarked(addr); 803 } 804 805 inline bool do_yield_check(uint worker_i = 0); 806 807 // Called to abort the marking cycle after a Full GC takes place. 808 void abort(); 809 810 bool has_aborted() { return _has_aborted; } 811 812 const GCId& concurrent_gc_id(); 813 814 // This prints the global/local fingers. It is used for debugging. 815 NOT_PRODUCT(void print_finger();) 816 817 void print_summary_info(); 818 819 void print_worker_threads_on(outputStream* st) const; 820 821 void print_on_error(outputStream* st) const; 822 823 // The following indicate whether a given verbose level has been 824 // set. Notice that anything above stats is conditional to 825 // _MARKING_VERBOSE_ having been set to 1 826 bool verbose_stats() { 827 return _verbose_level >= stats_verbose; 828 } 829 bool verbose_low() { 830 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; 831 } 832 bool verbose_medium() { 833 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; 834 } 835 bool verbose_high() { 836 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; 837 } 838 839 // Liveness counting 840 841 // Utility routine to set an exclusive range of cards on the given 842 // card liveness bitmap 843 inline void set_card_bitmap_range(BitMap* card_bm, 844 BitMap::idx_t start_idx, 845 BitMap::idx_t end_idx, 846 bool is_par); 847 848 // Returns the card number of the bottom of the G1 heap. 849 // Used in biasing indices into accounting card bitmaps. 850 intptr_t heap_bottom_card_num() const { 851 return _heap_bottom_card_num; 852 } 853 854 // Returns the card bitmap for a given task or worker id. 855 BitMap* count_card_bitmap_for(uint worker_id) { 856 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 857 assert(_count_card_bitmaps != NULL, "uninitialized"); 858 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 859 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 860 return task_card_bm; 861 } 862 863 // Returns the array containing the marked bytes for each region, 864 // for the given worker or task id. 865 size_t* count_marked_bytes_array_for(uint worker_id) { 866 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 867 assert(_count_marked_bytes != NULL, "uninitialized"); 868 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 869 assert(marked_bytes_array != NULL, "uninitialized"); 870 return marked_bytes_array; 871 } 872 873 // Returns the index in the liveness accounting card table bitmap 874 // for the given address 875 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 876 877 // Counts the size of the given memory region in the the given 878 // marked_bytes array slot for the given HeapRegion. 879 // Sets the bits in the given card bitmap that are associated with the 880 // cards that are spanned by the memory region. 881 inline void count_region(MemRegion mr, 882 HeapRegion* hr, 883 size_t* marked_bytes_array, 884 BitMap* task_card_bm); 885 886 // Counts the given memory region in the task/worker counting 887 // data structures for the given worker id. 888 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id); 889 890 // Counts the given object in the given task/worker counting 891 // data structures. 892 inline void count_object(oop obj, 893 HeapRegion* hr, 894 size_t* marked_bytes_array, 895 BitMap* task_card_bm); 896 897 // Attempts to mark the given object and, if successful, counts 898 // the object in the given task/worker counting structures. 899 inline bool par_mark_and_count(oop obj, 900 HeapRegion* hr, 901 size_t* marked_bytes_array, 902 BitMap* task_card_bm); 903 904 // Attempts to mark the given object and, if successful, counts 905 // the object in the task/worker counting structures for the 906 // given worker id. 907 inline bool par_mark_and_count(oop obj, 908 size_t word_size, 909 HeapRegion* hr, 910 uint worker_id); 911 912 // Returns true if initialization was successfully completed. 913 bool completed_initialization() const { 914 return _completed_initialization; 915 } 916 917 protected: 918 // Clear all the per-task bitmaps and arrays used to store the 919 // counting data. 920 void clear_all_count_data(); 921 922 // Aggregates the counting data for each worker/task 923 // that was constructed while marking. Also sets 924 // the amount of marked bytes for each region and 925 // the top at concurrent mark count. 926 void aggregate_count_data(); 927 928 // Verification routine 929 void verify_count_data(); 930 }; 931 932 // A class representing a marking task. 933 class CMTask : public TerminatorTerminator { 934 private: 935 enum PrivateConstants { 936 // the regular clock call is called once the scanned words reaches 937 // this limit 938 words_scanned_period = 12*1024, 939 // the regular clock call is called once the number of visited 940 // references reaches this limit 941 refs_reached_period = 384, 942 // initial value for the hash seed, used in the work stealing code 943 init_hash_seed = 17, 944 // how many entries will be transferred between global stack and 945 // local queues 946 global_stack_transfer_size = 16 947 }; 948 949 uint _worker_id; 950 G1CollectedHeap* _g1h; 951 ConcurrentMark* _cm; 952 CMBitMap* _nextMarkBitMap; 953 // the task queue of this task 954 CMTaskQueue* _task_queue; 955 private: 956 // the task queue set---needed for stealing 957 CMTaskQueueSet* _task_queues; 958 // indicates whether the task has been claimed---this is only for 959 // debugging purposes 960 bool _claimed; 961 962 // number of calls to this task 963 int _calls; 964 965 // when the virtual timer reaches this time, the marking step should 966 // exit 967 double _time_target_ms; 968 // the start time of the current marking step 969 double _start_time_ms; 970 971 // the oop closure used for iterations over oops 972 G1CMOopClosure* _cm_oop_closure; 973 974 // the region this task is scanning, NULL if we're not scanning any 975 HeapRegion* _curr_region; 976 // the local finger of this task, NULL if we're not scanning a region 977 HeapWord* _finger; 978 // limit of the region this task is scanning, NULL if we're not scanning one 979 HeapWord* _region_limit; 980 981 // the number of words this task has scanned 982 size_t _words_scanned; 983 // When _words_scanned reaches this limit, the regular clock is 984 // called. Notice that this might be decreased under certain 985 // circumstances (i.e. when we believe that we did an expensive 986 // operation). 987 size_t _words_scanned_limit; 988 // the initial value of _words_scanned_limit (i.e. what it was 989 // before it was decreased). 990 size_t _real_words_scanned_limit; 991 992 // the number of references this task has visited 993 size_t _refs_reached; 994 // When _refs_reached reaches this limit, the regular clock is 995 // called. Notice this this might be decreased under certain 996 // circumstances (i.e. when we believe that we did an expensive 997 // operation). 998 size_t _refs_reached_limit; 999 // the initial value of _refs_reached_limit (i.e. what it was before 1000 // it was decreased). 1001 size_t _real_refs_reached_limit; 1002 1003 // used by the work stealing stuff 1004 int _hash_seed; 1005 // if this is true, then the task has aborted for some reason 1006 bool _has_aborted; 1007 // set when the task aborts because it has met its time quota 1008 bool _has_timed_out; 1009 // true when we're draining SATB buffers; this avoids the task 1010 // aborting due to SATB buffers being available (as we're already 1011 // dealing with them) 1012 bool _draining_satb_buffers; 1013 1014 // number sequence of past step times 1015 NumberSeq _step_times_ms; 1016 // elapsed time of this task 1017 double _elapsed_time_ms; 1018 // termination time of this task 1019 double _termination_time_ms; 1020 // when this task got into the termination protocol 1021 double _termination_start_time_ms; 1022 1023 // true when the task is during a concurrent phase, false when it is 1024 // in the remark phase (so, in the latter case, we do not have to 1025 // check all the things that we have to check during the concurrent 1026 // phase, i.e. SATB buffer availability...) 1027 bool _concurrent; 1028 1029 TruncatedSeq _marking_step_diffs_ms; 1030 1031 // Counting data structures. Embedding the task's marked_bytes_array 1032 // and card bitmap into the actual task saves having to go through 1033 // the ConcurrentMark object. 1034 size_t* _marked_bytes_array; 1035 BitMap* _card_bm; 1036 1037 // LOTS of statistics related with this task 1038 #if _MARKING_STATS_ 1039 NumberSeq _all_clock_intervals_ms; 1040 double _interval_start_time_ms; 1041 1042 size_t _aborted; 1043 size_t _aborted_overflow; 1044 size_t _aborted_cm_aborted; 1045 size_t _aborted_yield; 1046 size_t _aborted_timed_out; 1047 size_t _aborted_satb; 1048 size_t _aborted_termination; 1049 1050 size_t _steal_attempts; 1051 size_t _steals; 1052 1053 size_t _clock_due_to_marking; 1054 size_t _clock_due_to_scanning; 1055 1056 size_t _local_pushes; 1057 size_t _local_pops; 1058 size_t _local_max_size; 1059 size_t _objs_scanned; 1060 1061 size_t _global_pushes; 1062 size_t _global_pops; 1063 size_t _global_max_size; 1064 1065 size_t _global_transfers_to; 1066 size_t _global_transfers_from; 1067 1068 size_t _regions_claimed; 1069 size_t _objs_found_on_bitmap; 1070 1071 size_t _satb_buffers_processed; 1072 #endif // _MARKING_STATS_ 1073 1074 // it updates the local fields after this task has claimed 1075 // a new region to scan 1076 void setup_for_region(HeapRegion* hr); 1077 // it brings up-to-date the limit of the region 1078 void update_region_limit(); 1079 1080 // called when either the words scanned or the refs visited limit 1081 // has been reached 1082 void reached_limit(); 1083 // recalculates the words scanned and refs visited limits 1084 void recalculate_limits(); 1085 // decreases the words scanned and refs visited limits when we reach 1086 // an expensive operation 1087 void decrease_limits(); 1088 // it checks whether the words scanned or refs visited reached their 1089 // respective limit and calls reached_limit() if they have 1090 void check_limits() { 1091 if (_words_scanned >= _words_scanned_limit || 1092 _refs_reached >= _refs_reached_limit) { 1093 reached_limit(); 1094 } 1095 } 1096 // this is supposed to be called regularly during a marking step as 1097 // it checks a bunch of conditions that might cause the marking step 1098 // to abort 1099 void regular_clock_call(); 1100 bool concurrent() { return _concurrent; } 1101 1102 public: 1103 // It resets the task; it should be called right at the beginning of 1104 // a marking phase. 1105 void reset(CMBitMap* _nextMarkBitMap); 1106 // it clears all the fields that correspond to a claimed region. 1107 void clear_region_fields(); 1108 1109 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 1110 1111 // The main method of this class which performs a marking step 1112 // trying not to exceed the given duration. However, it might exit 1113 // prematurely, according to some conditions (i.e. SATB buffers are 1114 // available for processing). 1115 void do_marking_step(double target_ms, 1116 bool do_termination, 1117 bool is_serial); 1118 1119 // These two calls start and stop the timer 1120 void record_start_time() { 1121 _elapsed_time_ms = os::elapsedTime() * 1000.0; 1122 } 1123 void record_end_time() { 1124 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 1125 } 1126 1127 // returns the worker ID associated with this task. 1128 uint worker_id() { return _worker_id; } 1129 1130 // From TerminatorTerminator. It determines whether this task should 1131 // exit the termination protocol after it's entered it. 1132 virtual bool should_exit_termination(); 1133 1134 // Resets the local region fields after a task has finished scanning a 1135 // region; or when they have become stale as a result of the region 1136 // being evacuated. 1137 void giveup_current_region(); 1138 1139 HeapWord* finger() { return _finger; } 1140 1141 bool has_aborted() { return _has_aborted; } 1142 void set_has_aborted() { _has_aborted = true; } 1143 void clear_has_aborted() { _has_aborted = false; } 1144 bool has_timed_out() { return _has_timed_out; } 1145 bool claimed() { return _claimed; } 1146 1147 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 1148 1149 // It grays the object by marking it and, if necessary, pushing it 1150 // on the local queue 1151 inline void deal_with_reference(oop obj); 1152 1153 // It scans an object and visits its children. 1154 void scan_object(oop obj); 1155 1156 // It pushes an object on the local queue. 1157 inline void push(oop obj); 1158 1159 // These two move entries to/from the global stack. 1160 void move_entries_to_global_stack(); 1161 void get_entries_from_global_stack(); 1162 1163 // It pops and scans objects from the local queue. If partially is 1164 // true, then it stops when the queue size is of a given limit. If 1165 // partially is false, then it stops when the queue is empty. 1166 void drain_local_queue(bool partially); 1167 // It moves entries from the global stack to the local queue and 1168 // drains the local queue. If partially is true, then it stops when 1169 // both the global stack and the local queue reach a given size. If 1170 // partially if false, it tries to empty them totally. 1171 void drain_global_stack(bool partially); 1172 // It keeps picking SATB buffers and processing them until no SATB 1173 // buffers are available. 1174 void drain_satb_buffers(); 1175 1176 // moves the local finger to a new location 1177 inline void move_finger_to(HeapWord* new_finger) { 1178 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 1179 _finger = new_finger; 1180 } 1181 1182 CMTask(uint worker_id, 1183 ConcurrentMark *cm, 1184 size_t* marked_bytes, 1185 BitMap* card_bm, 1186 CMTaskQueue* task_queue, 1187 CMTaskQueueSet* task_queues); 1188 1189 // it prints statistics associated with this task 1190 void print_stats(); 1191 1192 #if _MARKING_STATS_ 1193 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } 1194 #endif // _MARKING_STATS_ 1195 }; 1196 1197 // Class that's used to to print out per-region liveness 1198 // information. It's currently used at the end of marking and also 1199 // after we sort the old regions at the end of the cleanup operation. 1200 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 1201 private: 1202 outputStream* _out; 1203 1204 // Accumulators for these values. 1205 size_t _total_used_bytes; 1206 size_t _total_capacity_bytes; 1207 size_t _total_prev_live_bytes; 1208 size_t _total_next_live_bytes; 1209 1210 // These are set up when we come across a "stars humongous" region 1211 // (as this is where most of this information is stored, not in the 1212 // subsequent "continues humongous" regions). After that, for every 1213 // region in a given humongous region series we deduce the right 1214 // values for it by simply subtracting the appropriate amount from 1215 // these fields. All these values should reach 0 after we've visited 1216 // the last region in the series. 1217 size_t _hum_used_bytes; 1218 size_t _hum_capacity_bytes; 1219 size_t _hum_prev_live_bytes; 1220 size_t _hum_next_live_bytes; 1221 1222 // Accumulator for the remembered set size 1223 size_t _total_remset_bytes; 1224 1225 // Accumulator for strong code roots memory size 1226 size_t _total_strong_code_roots_bytes; 1227 1228 static double perc(size_t val, size_t total) { 1229 if (total == 0) { 1230 return 0.0; 1231 } else { 1232 return 100.0 * ((double) val / (double) total); 1233 } 1234 } 1235 1236 static double bytes_to_mb(size_t val) { 1237 return (double) val / (double) M; 1238 } 1239 1240 // See the .cpp file. 1241 size_t get_hum_bytes(size_t* hum_bytes); 1242 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1243 size_t* prev_live_bytes, size_t* next_live_bytes); 1244 1245 public: 1246 // The header and footer are printed in the constructor and 1247 // destructor respectively. 1248 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name); 1249 virtual bool doHeapRegion(HeapRegion* r); 1250 ~G1PrintRegionLivenessInfoClosure(); 1251 }; 1252 1253 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP