1 /*
2 * Copyright (c) 2001, 2012, 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
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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).
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
27
28 #include "gc_implementation/g1/heapRegionSets.hpp"
29 #include "utilities/taskqueue.hpp"
30
31 class G1CollectedHeap;
32 class CMTask;
33 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue;
34 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
35
36 // Closure used by CM during concurrent reference discovery
37 // and reference processing (during remarking) to determine
38 // if a particular object is alive. It is primarily used
39 // to determine if referents of discovered reference objects
40 // are alive. An instance is also embedded into the
41 // reference processor as the _is_alive_non_header field
42 class G1CMIsAliveClosure: public BoolObjectClosure {
43 G1CollectedHeap* _g1;
44 public:
45 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
46
47 void do_object(oop obj) {
48 ShouldNotCallThis();
49 }
50 bool do_object_b(oop obj);
51 };
52
53 // A generic CM bit map. This is essentially a wrapper around the BitMap
54 // class, with one bit per (1<<_shifter) HeapWords.
55
56 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
57 protected:
58 HeapWord* _bmStartWord; // base address of range covered by map
59 size_t _bmWordSize; // map size (in #HeapWords covered)
60 const int _shifter; // map to char or bit
61 VirtualSpace _virtual_space; // underlying the bit map
62 BitMap _bm; // the bit map itself
63
64 public:
65 // constructor
66 CMBitMapRO(ReservedSpace rs, 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(HeapWord* addr,
92 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(HeapWord* addr,
97 HeapWord* limit = NULL) const;
98
99 // conversion utilities
100 // XXX Fix these so that offsets are size_t's...
101 HeapWord* offsetToHeapWord(size_t offset) const {
102 return _bmStartWord + (offset << _shifter);
103 }
104 size_t heapWordToOffset(HeapWord* addr) const {
105 return pointer_delta(addr, _bmStartWord) >> _shifter;
106 }
107 int heapWordDiffToOffsetDiff(size_t diff) const;
108 HeapWord* nextWord(HeapWord* addr) {
109 return offsetToHeapWord(heapWordToOffset(addr) + 1);
110 }
111
112 // debugging
113 NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
114 };
115
116 class CMBitMap : public CMBitMapRO {
117
118 public:
119 // constructor
120 CMBitMap(ReservedSpace rs, int shifter) :
121 CMBitMapRO(rs, shifter) {}
122
123 // write marks
124 void mark(HeapWord* addr) {
125 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
126 "outside underlying space?");
127 _bm.set_bit(heapWordToOffset(addr));
128 }
129 void clear(HeapWord* addr) {
130 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
131 "outside underlying space?");
132 _bm.clear_bit(heapWordToOffset(addr));
133 }
134 bool parMark(HeapWord* addr) {
135 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
136 "outside underlying space?");
137 return _bm.par_set_bit(heapWordToOffset(addr));
138 }
139 bool parClear(HeapWord* addr) {
140 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
141 "outside underlying space?");
142 return _bm.par_clear_bit(heapWordToOffset(addr));
143 }
144 void markRange(MemRegion mr);
145 void clearAll();
146 void clearRange(MemRegion mr);
147
148 // Starting at the bit corresponding to "addr" (inclusive), find the next
149 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
150 // the end of this run (stopping at "end_addr"). Return the MemRegion
151 // covering from the start of the region corresponding to the first bit
152 // of the run to the end of the region corresponding to the last bit of
153 // the run. If there is no "1" bit at or after "addr", return an empty
154 // MemRegion.
155 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
156 };
157
158 // Represents a marking stack used by the CM collector.
159 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
160 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
161 ConcurrentMark* _cm;
162 oop* _base; // bottom of stack
163 jint _index; // one more than last occupied index
164 jint _capacity; // max #elements
165 jint _saved_index; // value of _index saved at start of GC
166 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
167
168 bool _overflow;
169 DEBUG_ONLY(bool _drain_in_progress;)
170 DEBUG_ONLY(bool _drain_in_progress_yields;)
171
172 public:
173 CMMarkStack(ConcurrentMark* cm);
174 ~CMMarkStack();
175
176 void allocate(size_t size);
177
178 oop pop() {
179 if (!isEmpty()) {
180 return _base[--_index] ;
181 }
182 return NULL;
183 }
184
185 // If overflow happens, don't do the push, and record the overflow.
186 // *Requires* that "ptr" is already marked.
187 void push(oop ptr) {
188 if (isFull()) {
189 // Record overflow.
190 _overflow = true;
191 return;
192 } else {
193 _base[_index++] = ptr;
194 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
195 }
196 }
197 // Non-block impl. Note: concurrency is allowed only with other
198 // "par_push" operations, not with "pop" or "drain". We would need
199 // parallel versions of them if such concurrency was desired.
200 void par_push(oop ptr);
201
202 // Pushes the first "n" elements of "ptr_arr" on the stack.
203 // Non-block impl. Note: concurrency is allowed only with other
204 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
205 void par_adjoin_arr(oop* ptr_arr, int n);
206
207 // Pushes the first "n" elements of "ptr_arr" on the stack.
208 // Locking impl: concurrency is allowed only with
209 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
210 // locking strategy.
211 void par_push_arr(oop* ptr_arr, int n);
212
213 // If returns false, the array was empty. Otherwise, removes up to "max"
214 // elements from the stack, and transfers them to "ptr_arr" in an
215 // unspecified order. The actual number transferred is given in "n" ("n
216 // == 0" is deliberately redundant with the return value.) Locking impl:
217 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
218 // operations, which use the same locking strategy.
219 bool par_pop_arr(oop* ptr_arr, int max, int* n);
220
221 // Drain the mark stack, applying the given closure to all fields of
222 // objects on the stack. (That is, continue until the stack is empty,
223 // even if closure applications add entries to the stack.) The "bm"
224 // argument, if non-null, may be used to verify that only marked objects
225 // are on the mark stack. If "yield_after" is "true", then the
226 // concurrent marker performing the drain offers to yield after
227 // processing each object. If a yield occurs, stops the drain operation
228 // and returns false. Otherwise, returns true.
229 template<class OopClosureClass>
230 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
231
232 bool isEmpty() { return _index == 0; }
233 bool isFull() { return _index == _capacity; }
234 int maxElems() { return _capacity; }
235
236 bool overflow() { return _overflow; }
237 void clear_overflow() { _overflow = false; }
238
239 int size() { return _index; }
240
241 void setEmpty() { _index = 0; clear_overflow(); }
242
243 // Record the current index.
244 void note_start_of_gc();
245
246 // Make sure that we have not added any entries to the stack during GC.
247 void note_end_of_gc();
248
249 // iterate over the oops in the mark stack, up to the bound recorded via
250 // the call above.
251 void oops_do(OopClosure* f);
252 };
253
254 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
255 private:
256 #ifndef PRODUCT
257 uintx _num_remaining;
258 bool _force;
259 #endif // !defined(PRODUCT)
260
261 public:
262 void init() PRODUCT_RETURN;
263 void update() PRODUCT_RETURN;
264 bool should_force() PRODUCT_RETURN_( return false; );
265 };
266
267 // this will enable a variety of different statistics per GC task
268 #define _MARKING_STATS_ 0
269 // this will enable the higher verbose levels
270 #define _MARKING_VERBOSE_ 0
271
272 #if _MARKING_STATS_
273 #define statsOnly(statement) \
274 do { \
275 statement ; \
276 } while (0)
277 #else // _MARKING_STATS_
278 #define statsOnly(statement) \
279 do { \
280 } while (0)
281 #endif // _MARKING_STATS_
282
283 typedef enum {
284 no_verbose = 0, // verbose turned off
285 stats_verbose, // only prints stats at the end of marking
286 low_verbose, // low verbose, mostly per region and per major event
287 medium_verbose, // a bit more detailed than low
288 high_verbose // per object verbose
289 } CMVerboseLevel;
290
291 class YoungList;
292
293 // Root Regions are regions that are not empty at the beginning of a
294 // marking cycle and which we might collect during an evacuation pause
295 // while the cycle is active. Given that, during evacuation pauses, we
296 // do not copy objects that are explicitly marked, what we have to do
297 // for the root regions is to scan them and mark all objects reachable
298 // from them. According to the SATB assumptions, we only need to visit
299 // each object once during marking. So, as long as we finish this scan
300 // before the next evacuation pause, we can copy the objects from the
301 // root regions without having to mark them or do anything else to them.
302 //
303 // Currently, we only support root region scanning once (at the start
304 // of the marking cycle) and the root regions are all the survivor
305 // regions populated during the initial-mark pause.
306 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
307 private:
308 YoungList* _young_list;
309 ConcurrentMark* _cm;
310
311 volatile bool _scan_in_progress;
312 volatile bool _should_abort;
313 HeapRegion* volatile _next_survivor;
314
315 public:
316 CMRootRegions();
317 // We actually do most of the initialization in this method.
318 void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
319
320 // Reset the claiming / scanning of the root regions.
321 void prepare_for_scan();
322
323 // Forces get_next() to return NULL so that the iteration aborts early.
324 void abort() { _should_abort = true; }
325
326 // Return true if the CM thread are actively scanning root regions,
327 // false otherwise.
328 bool scan_in_progress() { return _scan_in_progress; }
329
330 // Claim the next root region to scan atomically, or return NULL if
331 // all have been claimed.
332 HeapRegion* claim_next();
333
334 // Flag that we're done with root region scanning and notify anyone
335 // who's waiting on it. If aborted is false, assume that all regions
336 // have been claimed.
337 void scan_finished();
338
339 // If CM threads are still scanning root regions, wait until they
340 // are done. Return true if we had to wait, false otherwise.
341 bool wait_until_scan_finished();
342 };
343
344 class ConcurrentMarkThread;
345
346 class ConcurrentMark: public CHeapObj<mtGC> {
347 friend class ConcurrentMarkThread;
348 friend class CMTask;
349 friend class CMBitMapClosure;
350 friend class CMGlobalObjectClosure;
351 friend class CMRemarkTask;
352 friend class CMConcurrentMarkingTask;
353 friend class G1ParNoteEndTask;
354 friend class CalcLiveObjectsClosure;
355 friend class G1CMRefProcTaskProxy;
356 friend class G1CMRefProcTaskExecutor;
357 friend class G1CMParKeepAliveAndDrainClosure;
358 friend class G1CMParDrainMarkingStackClosure;
359
360 protected:
361 ConcurrentMarkThread* _cmThread; // the thread doing the work
362 G1CollectedHeap* _g1h; // the heap.
363 uint _parallel_marking_threads; // the number of marking
364 // threads we're use
365 uint _max_parallel_marking_threads; // max number of marking
366 // threads we'll ever use
367 double _sleep_factor; // how much we have to sleep, with
368 // respect to the work we just did, to
369 // meet the marking overhead goal
370 double _marking_task_overhead; // marking target overhead for
371 // a single task
372
373 // same as the two above, but for the cleanup task
374 double _cleanup_sleep_factor;
375 double _cleanup_task_overhead;
376
377 FreeRegionList _cleanup_list;
378
379 // Concurrent marking support structures
380 CMBitMap _markBitMap1;
381 CMBitMap _markBitMap2;
382 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
383 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
384
385 BitMap _region_bm;
386 BitMap _card_bm;
387
388 // Heap bounds
389 HeapWord* _heap_start;
390 HeapWord* _heap_end;
391
392 // Root region tracking and claiming.
393 CMRootRegions _root_regions;
394
395 // For gray objects
396 CMMarkStack _markStack; // Grey objects behind global finger.
397 HeapWord* volatile _finger; // the global finger, region aligned,
398 // always points to the end of the
399 // last claimed region
400
401 // marking tasks
402 uint _max_task_num; // maximum task number
403 uint _active_tasks; // task num currently active
404 CMTask** _tasks; // task queue array (max_task_num len)
405 CMTaskQueueSet* _task_queues; // task queue set
406 ParallelTaskTerminator _terminator; // for termination
407
408 // Two sync barriers that are used to synchronise tasks when an
409 // overflow occurs. The algorithm is the following. All tasks enter
410 // the first one to ensure that they have all stopped manipulating
411 // the global data structures. After they exit it, they re-initialise
412 // their data structures and task 0 re-initialises the global data
413 // structures. Then, they enter the second sync barrier. This
414 // ensure, that no task starts doing work before all data
415 // structures (local and global) have been re-initialised. When they
416 // exit it, they are free to start working again.
417 WorkGangBarrierSync _first_overflow_barrier_sync;
418 WorkGangBarrierSync _second_overflow_barrier_sync;
419
420 // this is set by any task, when an overflow on the global data
421 // structures is detected.
422 volatile bool _has_overflown;
423 // true: marking is concurrent, false: we're in remark
424 volatile bool _concurrent;
425 // set at the end of a Full GC so that marking aborts
426 volatile bool _has_aborted;
427
428 // used when remark aborts due to an overflow to indicate that
429 // another concurrent marking phase should start
430 volatile bool _restart_for_overflow;
431
432 // This is true from the very start of concurrent marking until the
433 // point when all the tasks complete their work. It is really used
434 // to determine the points between the end of concurrent marking and
435 // time of remark.
436 volatile bool _concurrent_marking_in_progress;
437
438 // verbose level
439 CMVerboseLevel _verbose_level;
440
441 // All of these times are in ms.
442 NumberSeq _init_times;
443 NumberSeq _remark_times;
444 NumberSeq _remark_mark_times;
445 NumberSeq _remark_weak_ref_times;
446 NumberSeq _cleanup_times;
447 double _total_counting_time;
448 double _total_rs_scrub_time;
449
450 double* _accum_task_vtime; // accumulated task vtime
451
452 FlexibleWorkGang* _parallel_workers;
453
454 ForceOverflowSettings _force_overflow_conc;
455 ForceOverflowSettings _force_overflow_stw;
456
457 void weakRefsWork(bool clear_all_soft_refs);
458
459 void swapMarkBitMaps();
460
461 // It resets the global marking data structures, as well as the
462 // task local ones; should be called during initial mark.
463 void reset();
464 // It resets all the marking data structures.
465 void clear_marking_state(bool clear_overflow = true);
466
467 // It should be called to indicate which phase we're in (concurrent
468 // mark or remark) and how many threads are currently active.
469 void set_phase(uint active_tasks, bool concurrent);
470 // We do this after we're done with marking so that the marking data
471 // structures are initialised to a sensible and predictable state.
472 void set_non_marking_state();
473
474 // prints all gathered CM-related statistics
475 void print_stats();
476
477 bool cleanup_list_is_empty() {
478 return _cleanup_list.is_empty();
479 }
480
481 // accessor methods
482 uint parallel_marking_threads() { return _parallel_marking_threads; }
483 uint max_parallel_marking_threads() { return _max_parallel_marking_threads;}
484 double sleep_factor() { return _sleep_factor; }
485 double marking_task_overhead() { return _marking_task_overhead;}
486 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
487 double cleanup_task_overhead() { return _cleanup_task_overhead;}
488
489 HeapWord* finger() { return _finger; }
490 bool concurrent() { return _concurrent; }
491 uint active_tasks() { return _active_tasks; }
492 ParallelTaskTerminator* terminator() { return &_terminator; }
493
494 // It claims the next available region to be scanned by a marking
495 // task. It might return NULL if the next region is empty or we have
496 // run out of regions. In the latter case, out_of_regions()
497 // determines whether we've really run out of regions or the task
498 // should call claim_region() again. This might seem a bit
499 // awkward. Originally, the code was written so that claim_region()
500 // either successfully returned with a non-empty region or there
501 // were no more regions to be claimed. The problem with this was
502 // that, in certain circumstances, it iterated over large chunks of
503 // the heap finding only empty regions and, while it was working, it
504 // was preventing the calling task to call its regular clock
505 // method. So, this way, each task will spend very little time in
506 // claim_region() and is allowed to call the regular clock method
507 // frequently.
508 HeapRegion* claim_region(int task);
509
510 // It determines whether we've run out of regions to scan.
511 bool out_of_regions() { return _finger == _heap_end; }
512
513 // Returns the task with the given id
514 CMTask* task(int id) {
515 assert(0 <= id && id < (int) _active_tasks,
516 "task id not within active bounds");
517 return _tasks[id];
518 }
519
520 // Returns the task queue with the given id
521 CMTaskQueue* task_queue(int id) {
522 assert(0 <= id && id < (int) _active_tasks,
523 "task queue id not within active bounds");
524 return (CMTaskQueue*) _task_queues->queue(id);
525 }
526
527 // Returns the task queue set
528 CMTaskQueueSet* task_queues() { return _task_queues; }
529
530 // Access / manipulation of the overflow flag which is set to
531 // indicate that the global stack has overflown
532 bool has_overflown() { return _has_overflown; }
533 void set_has_overflown() { _has_overflown = true; }
534 void clear_has_overflown() { _has_overflown = false; }
535 bool restart_for_overflow() { return _restart_for_overflow; }
536
537 bool has_aborted() { return _has_aborted; }
538
539 // Methods to enter the two overflow sync barriers
540 void enter_first_sync_barrier(int task_num);
541 void enter_second_sync_barrier(int task_num);
542
543 ForceOverflowSettings* force_overflow_conc() {
544 return &_force_overflow_conc;
545 }
546
547 ForceOverflowSettings* force_overflow_stw() {
548 return &_force_overflow_stw;
549 }
550
551 ForceOverflowSettings* force_overflow() {
552 if (concurrent()) {
553 return force_overflow_conc();
554 } else {
555 return force_overflow_stw();
556 }
557 }
558
559 // Live Data Counting data structures...
560 // These data structures are initialized at the start of
561 // marking. They are written to while marking is active.
562 // They are aggregated during remark; the aggregated values
563 // are then used to populate the _region_bm, _card_bm, and
564 // the total live bytes, which are then subsequently updated
565 // during cleanup.
566
567 // An array of bitmaps (one bit map per task). Each bitmap
568 // is used to record the cards spanned by the live objects
569 // marked by that task/worker.
570 BitMap* _count_card_bitmaps;
571
572 // Used to record the number of marked live bytes
573 // (for each region, by worker thread).
574 size_t** _count_marked_bytes;
575
576 // Card index of the bottom of the G1 heap. Used for biasing indices into
577 // the card bitmaps.
578 intptr_t _heap_bottom_card_num;
579
580 public:
581 // Manipulation of the global mark stack.
582 // Notice that the first mark_stack_push is CAS-based, whereas the
583 // two below are Mutex-based. This is OK since the first one is only
584 // called during evacuation pauses and doesn't compete with the
585 // other two (which are called by the marking tasks during
586 // concurrent marking or remark).
587 bool mark_stack_push(oop p) {
588 _markStack.par_push(p);
589 if (_markStack.overflow()) {
590 set_has_overflown();
591 return false;
592 }
593 return true;
594 }
595 bool mark_stack_push(oop* arr, int n) {
596 _markStack.par_push_arr(arr, n);
597 if (_markStack.overflow()) {
598 set_has_overflown();
599 return false;
600 }
601 return true;
602 }
603 void mark_stack_pop(oop* arr, int max, int* n) {
604 _markStack.par_pop_arr(arr, max, n);
605 }
606 size_t mark_stack_size() { return _markStack.size(); }
607 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
608 bool mark_stack_overflow() { return _markStack.overflow(); }
609 bool mark_stack_empty() { return _markStack.isEmpty(); }
610
611 CMRootRegions* root_regions() { return &_root_regions; }
612
613 bool concurrent_marking_in_progress() {
614 return _concurrent_marking_in_progress;
615 }
616 void set_concurrent_marking_in_progress() {
617 _concurrent_marking_in_progress = true;
618 }
619 void clear_concurrent_marking_in_progress() {
620 _concurrent_marking_in_progress = false;
621 }
622
623 void update_accum_task_vtime(int i, double vtime) {
624 _accum_task_vtime[i] += vtime;
625 }
626
627 double all_task_accum_vtime() {
628 double ret = 0.0;
629 for (int i = 0; i < (int)_max_task_num; ++i)
630 ret += _accum_task_vtime[i];
631 return ret;
632 }
633
634 // Attempts to steal an object from the task queues of other tasks
635 bool try_stealing(int task_num, int* hash_seed, oop& obj) {
636 return _task_queues->steal(task_num, hash_seed, obj);
637 }
638
639 ConcurrentMark(ReservedSpace rs, uint max_regions);
640 ~ConcurrentMark();
641
642 ConcurrentMarkThread* cmThread() { return _cmThread; }
643
644 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
645 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
646
647 // Returns the number of GC threads to be used in a concurrent
648 // phase based on the number of GC threads being used in a STW
649 // phase.
650 uint scale_parallel_threads(uint n_par_threads);
651
652 // Calculates the number of GC threads to be used in a concurrent phase.
653 uint calc_parallel_marking_threads();
654
655 // The following three are interaction between CM and
656 // G1CollectedHeap
657
658 // This notifies CM that a root during initial-mark needs to be
659 // grayed. It is MT-safe. word_size is the size of the object in
660 // words. It is passed explicitly as sometimes we cannot calculate
661 // it from the given object because it might be in an inconsistent
662 // state (e.g., in to-space and being copied). So the caller is
663 // responsible for dealing with this issue (e.g., get the size from
664 // the from-space image when the to-space image might be
665 // inconsistent) and always passing the size. hr is the region that
666 // contains the object and it's passed optionally from callers who
667 // might already have it (no point in recalculating it).
668 inline void grayRoot(oop obj, size_t word_size,
669 uint worker_id, HeapRegion* hr = NULL);
670
671 // It iterates over the heap and for each object it comes across it
672 // will dump the contents of its reference fields, as well as
673 // liveness information for the object and its referents. The dump
674 // will be written to a file with the following name:
675 // G1PrintReachableBaseFile + "." + str.
676 // vo decides whether the prev (vo == UsePrevMarking), the next
677 // (vo == UseNextMarking) marking information, or the mark word
678 // (vo == UseMarkWord) will be used to determine the liveness of
679 // each object / referent.
680 // If all is true, all objects in the heap will be dumped, otherwise
681 // only the live ones. In the dump the following symbols / breviations
682 // are used:
683 // M : an explicitly live object (its bitmap bit is set)
684 // > : an implicitly live object (over tams)
685 // O : an object outside the G1 heap (typically: in the perm gen)
686 // NOT : a reference field whose referent is not live
687 // AND MARKED : indicates that an object is both explicitly and
688 // implicitly live (it should be one or the other, not both)
689 void print_reachable(const char* str,
690 VerifyOption vo, bool all) PRODUCT_RETURN;
691
692 // Clear the next marking bitmap (will be called concurrently).
693 void clearNextBitmap();
694
695 // These two do the work that needs to be done before and after the
696 // initial root checkpoint. Since this checkpoint can be done at two
697 // different points (i.e. an explicit pause or piggy-backed on a
698 // young collection), then it's nice to be able to easily share the
699 // pre/post code. It might be the case that we can put everything in
700 // the post method. TP
701 void checkpointRootsInitialPre();
702 void checkpointRootsInitialPost();
703
704 // Scan all the root regions and mark everything reachable from
705 // them.
706 void scanRootRegions();
707
708 // Scan a single root region and mark everything reachable from it.
709 void scanRootRegion(HeapRegion* hr, uint worker_id);
710
711 // Do concurrent phase of marking, to a tentative transitive closure.
712 void markFromRoots();
713
714 void checkpointRootsFinal(bool clear_all_soft_refs);
715 void checkpointRootsFinalWork();
716 void cleanup();
717 void completeCleanup();
718
719 // Mark in the previous bitmap. NB: this is usually read-only, so use
720 // this carefully!
721 inline void markPrev(oop p);
722
723 // Clears marks for all objects in the given range, for the prev,
724 // next, or both bitmaps. NB: the previous bitmap is usually
725 // read-only, so use this carefully!
726 void clearRangePrevBitmap(MemRegion mr);
727 void clearRangeNextBitmap(MemRegion mr);
728 void clearRangeBothBitmaps(MemRegion mr);
729
730 // Notify data structures that a GC has started.
731 void note_start_of_gc() {
732 _markStack.note_start_of_gc();
733 }
734
735 // Notify data structures that a GC is finished.
736 void note_end_of_gc() {
737 _markStack.note_end_of_gc();
738 }
739
740 // Verify that there are no CSet oops on the stacks (taskqueues /
741 // global mark stack), enqueued SATB buffers, per-thread SATB
742 // buffers, and fingers (global / per-task). The boolean parameters
743 // decide which of the above data structures to verify. If marking
744 // is not in progress, it's a no-op.
745 void verify_no_cset_oops(bool verify_stacks,
746 bool verify_enqueued_buffers,
747 bool verify_thread_buffers,
748 bool verify_fingers) PRODUCT_RETURN;
749
750 // It is called at the end of an evacuation pause during marking so
751 // that CM is notified of where the new end of the heap is. It
752 // doesn't do anything if concurrent_marking_in_progress() is false,
753 // unless the force parameter is true.
754 void update_g1_committed(bool force = false);
755
756 bool isMarked(oop p) const {
757 assert(p != NULL && p->is_oop(), "expected an oop");
758 HeapWord* addr = (HeapWord*)p;
759 assert(addr >= _nextMarkBitMap->startWord() ||
760 addr < _nextMarkBitMap->endWord(), "in a region");
761
762 return _nextMarkBitMap->isMarked(addr);
763 }
764
765 inline bool not_yet_marked(oop p) const;
766
767 // XXX Debug code
768 bool containing_card_is_marked(void* p);
769 bool containing_cards_are_marked(void* start, void* last);
770
771 bool isPrevMarked(oop p) const {
772 assert(p != NULL && p->is_oop(), "expected an oop");
773 HeapWord* addr = (HeapWord*)p;
774 assert(addr >= _prevMarkBitMap->startWord() ||
775 addr < _prevMarkBitMap->endWord(), "in a region");
776
777 return _prevMarkBitMap->isMarked(addr);
778 }
779
780 inline bool do_yield_check(uint worker_i = 0);
781 inline bool should_yield();
782
783 // Called to abort the marking cycle after a Full GC takes palce.
784 void abort();
785
786 // This prints the global/local fingers. It is used for debugging.
787 NOT_PRODUCT(void print_finger();)
788
789 void print_summary_info();
790
791 void print_worker_threads_on(outputStream* st) const;
792
793 // The following indicate whether a given verbose level has been
794 // set. Notice that anything above stats is conditional to
795 // _MARKING_VERBOSE_ having been set to 1
796 bool verbose_stats() {
797 return _verbose_level >= stats_verbose;
798 }
799 bool verbose_low() {
800 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
801 }
802 bool verbose_medium() {
803 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
804 }
805 bool verbose_high() {
806 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
807 }
808
809 // Counting data structure accessors
810
811 // Returns the card number of the bottom of the G1 heap.
812 // Used in biasing indices into accounting card bitmaps.
813 intptr_t heap_bottom_card_num() const {
814 return _heap_bottom_card_num;
815 }
816
817 // Returns the card bitmap for a given task or worker id.
818 BitMap* count_card_bitmap_for(uint worker_id) {
819 assert(0 <= worker_id && worker_id < _max_task_num, "oob");
820 assert(_count_card_bitmaps != NULL, "uninitialized");
821 BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
822 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
823 return task_card_bm;
824 }
825
826 // Returns the array containing the marked bytes for each region,
827 // for the given worker or task id.
828 size_t* count_marked_bytes_array_for(uint worker_id) {
829 assert(0 <= worker_id && worker_id < _max_task_num, "oob");
830 assert(_count_marked_bytes != NULL, "uninitialized");
831 size_t* marked_bytes_array = _count_marked_bytes[worker_id];
832 assert(marked_bytes_array != NULL, "uninitialized");
833 return marked_bytes_array;
834 }
835
836 // Returns the index in the liveness accounting card table bitmap
837 // for the given address
838 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
839
840 // Counts the size of the given memory region in the the given
841 // marked_bytes array slot for the given HeapRegion.
842 // Sets the bits in the given card bitmap that are associated with the
843 // cards that are spanned by the memory region.
844 inline void count_region(MemRegion mr, HeapRegion* hr,
845 size_t* marked_bytes_array,
846 BitMap* task_card_bm);
847
848 // Counts the given memory region in the task/worker counting
849 // data structures for the given worker id.
850 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
851
852 // Counts the given memory region in the task/worker counting
853 // data structures for the given worker id.
854 inline void count_region(MemRegion mr, uint worker_id);
855
856 // Counts the given object in the given task/worker counting
857 // data structures.
858 inline void count_object(oop obj, HeapRegion* hr,
859 size_t* marked_bytes_array,
860 BitMap* task_card_bm);
861
862 // Counts the given object in the task/worker counting data
863 // structures for the given worker id.
864 inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
865
866 // Attempts to mark the given object and, if successful, counts
867 // the object in the given task/worker counting structures.
868 inline bool par_mark_and_count(oop obj, HeapRegion* hr,
869 size_t* marked_bytes_array,
870 BitMap* task_card_bm);
871
872 // Attempts to mark the given object and, if successful, counts
873 // the object in the task/worker counting structures for the
874 // given worker id.
875 inline bool par_mark_and_count(oop obj, size_t word_size,
876 HeapRegion* hr, uint worker_id);
877
878 // Attempts to mark the given object and, if successful, counts
879 // the object in the task/worker counting structures for the
880 // given worker id.
881 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
882
883 // Similar to the above routine but we don't know the heap region that
884 // contains the object to be marked/counted, which this routine looks up.
885 inline bool par_mark_and_count(oop obj, uint worker_id);
886
887 // Similar to the above routine but there are times when we cannot
888 // safely calculate the size of obj due to races and we, therefore,
889 // pass the size in as a parameter. It is the caller's reponsibility
890 // to ensure that the size passed in for obj is valid.
891 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
892
893 // Unconditionally mark the given object, and unconditinally count
894 // the object in the counting structures for worker id 0.
895 // Should *not* be called from parallel code.
896 inline bool mark_and_count(oop obj, HeapRegion* hr);
897
898 // Similar to the above routine but we don't know the heap region that
899 // contains the object to be marked/counted, which this routine looks up.
900 // Should *not* be called from parallel code.
901 inline bool mark_and_count(oop obj);
902
903 protected:
904 // Clear all the per-task bitmaps and arrays used to store the
905 // counting data.
906 void clear_all_count_data();
907
908 // Aggregates the counting data for each worker/task
909 // that was constructed while marking. Also sets
910 // the amount of marked bytes for each region and
911 // the top at concurrent mark count.
912 void aggregate_count_data();
913
914 // Verification routine
915 void verify_count_data();
916 };
917
918 // A class representing a marking task.
919 class CMTask : public TerminatorTerminator {
920 private:
921 enum PrivateConstants {
922 // the regular clock call is called once the scanned words reaches
923 // this limit
924 words_scanned_period = 12*1024,
925 // the regular clock call is called once the number of visited
926 // references reaches this limit
927 refs_reached_period = 384,
928 // initial value for the hash seed, used in the work stealing code
929 init_hash_seed = 17,
930 // how many entries will be transferred between global stack and
931 // local queues
932 global_stack_transfer_size = 16
933 };
934
935 int _task_id;
936 G1CollectedHeap* _g1h;
937 ConcurrentMark* _cm;
938 CMBitMap* _nextMarkBitMap;
939 // the task queue of this task
940 CMTaskQueue* _task_queue;
941 private:
942 // the task queue set---needed for stealing
943 CMTaskQueueSet* _task_queues;
944 // indicates whether the task has been claimed---this is only for
945 // debugging purposes
946 bool _claimed;
947
948 // number of calls to this task
949 int _calls;
950
951 // when the virtual timer reaches this time, the marking step should
952 // exit
953 double _time_target_ms;
954 // the start time of the current marking step
955 double _start_time_ms;
956
957 // the oop closure used for iterations over oops
958 G1CMOopClosure* _cm_oop_closure;
959
960 // the region this task is scanning, NULL if we're not scanning any
961 HeapRegion* _curr_region;
962 // the local finger of this task, NULL if we're not scanning a region
963 HeapWord* _finger;
964 // limit of the region this task is scanning, NULL if we're not scanning one
965 HeapWord* _region_limit;
966
967 // the number of words this task has scanned
968 size_t _words_scanned;
969 // When _words_scanned reaches this limit, the regular clock is
970 // called. Notice that this might be decreased under certain
971 // circumstances (i.e. when we believe that we did an expensive
972 // operation).
973 size_t _words_scanned_limit;
974 // the initial value of _words_scanned_limit (i.e. what it was
975 // before it was decreased).
976 size_t _real_words_scanned_limit;
977
978 // the number of references this task has visited
979 size_t _refs_reached;
980 // When _refs_reached reaches this limit, the regular clock is
981 // called. Notice this this might be decreased under certain
982 // circumstances (i.e. when we believe that we did an expensive
983 // operation).
984 size_t _refs_reached_limit;
985 // the initial value of _refs_reached_limit (i.e. what it was before
986 // it was decreased).
987 size_t _real_refs_reached_limit;
988
989 // used by the work stealing stuff
990 int _hash_seed;
991 // if this is true, then the task has aborted for some reason
992 bool _has_aborted;
993 // set when the task aborts because it has met its time quota
994 bool _has_timed_out;
995 // true when we're draining SATB buffers; this avoids the task
996 // aborting due to SATB buffers being available (as we're already
997 // dealing with them)
998 bool _draining_satb_buffers;
999
1000 // number sequence of past step times
1001 NumberSeq _step_times_ms;
1002 // elapsed time of this task
1003 double _elapsed_time_ms;
1004 // termination time of this task
1005 double _termination_time_ms;
1006 // when this task got into the termination protocol
1007 double _termination_start_time_ms;
1008
1009 // true when the task is during a concurrent phase, false when it is
1010 // in the remark phase (so, in the latter case, we do not have to
1011 // check all the things that we have to check during the concurrent
1012 // phase, i.e. SATB buffer availability...)
1013 bool _concurrent;
1014
1015 TruncatedSeq _marking_step_diffs_ms;
1016
1017 // Counting data structures. Embedding the task's marked_bytes_array
1018 // and card bitmap into the actual task saves having to go through
1019 // the ConcurrentMark object.
1020 size_t* _marked_bytes_array;
1021 BitMap* _card_bm;
1022
1023 // LOTS of statistics related with this task
1024 #if _MARKING_STATS_
1025 NumberSeq _all_clock_intervals_ms;
1026 double _interval_start_time_ms;
1027
1028 int _aborted;
1029 int _aborted_overflow;
1030 int _aborted_cm_aborted;
1031 int _aborted_yield;
1032 int _aborted_timed_out;
1033 int _aborted_satb;
1034 int _aborted_termination;
1035
1036 int _steal_attempts;
1037 int _steals;
1038
1039 int _clock_due_to_marking;
1040 int _clock_due_to_scanning;
1041
1042 int _local_pushes;
1043 int _local_pops;
1044 int _local_max_size;
1045 int _objs_scanned;
1046
1047 int _global_pushes;
1048 int _global_pops;
1049 int _global_max_size;
1050
1051 int _global_transfers_to;
1052 int _global_transfers_from;
1053
1054 int _regions_claimed;
1055 int _objs_found_on_bitmap;
1056
1057 int _satb_buffers_processed;
1058 #endif // _MARKING_STATS_
1059
1060 // it updates the local fields after this task has claimed
1061 // a new region to scan
1062 void setup_for_region(HeapRegion* hr);
1063 // it brings up-to-date the limit of the region
1064 void update_region_limit();
1065
1066 // called when either the words scanned or the refs visited limit
1067 // has been reached
1068 void reached_limit();
1069 // recalculates the words scanned and refs visited limits
1070 void recalculate_limits();
1071 // decreases the words scanned and refs visited limits when we reach
1072 // an expensive operation
1073 void decrease_limits();
1074 // it checks whether the words scanned or refs visited reached their
1075 // respective limit and calls reached_limit() if they have
1076 void check_limits() {
1077 if (_words_scanned >= _words_scanned_limit ||
1078 _refs_reached >= _refs_reached_limit) {
1079 reached_limit();
1080 }
1081 }
1082 // this is supposed to be called regularly during a marking step as
1083 // it checks a bunch of conditions that might cause the marking step
1084 // to abort
1085 void regular_clock_call();
1086 bool concurrent() { return _concurrent; }
1087
1088 public:
1089 // It resets the task; it should be called right at the beginning of
1090 // a marking phase.
1091 void reset(CMBitMap* _nextMarkBitMap);
1092 // it clears all the fields that correspond to a claimed region.
1093 void clear_region_fields();
1094
1095 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1096
1097 // The main method of this class which performs a marking step
1098 // trying not to exceed the given duration. However, it might exit
1099 // prematurely, according to some conditions (i.e. SATB buffers are
1100 // available for processing).
1101 void do_marking_step(double target_ms, bool do_stealing, bool do_termination);
1102
1103 // These two calls start and stop the timer
1104 void record_start_time() {
1105 _elapsed_time_ms = os::elapsedTime() * 1000.0;
1106 }
1107 void record_end_time() {
1108 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1109 }
1110
1111 // returns the task ID
1112 int task_id() { return _task_id; }
1113
1114 // From TerminatorTerminator. It determines whether this task should
1115 // exit the termination protocol after it's entered it.
1116 virtual bool should_exit_termination();
1117
1118 // Resets the local region fields after a task has finished scanning a
1119 // region; or when they have become stale as a result of the region
1120 // being evacuated.
1121 void giveup_current_region();
1122
1123 HeapWord* finger() { return _finger; }
1124
1125 bool has_aborted() { return _has_aborted; }
1126 void set_has_aborted() { _has_aborted = true; }
1127 void clear_has_aborted() { _has_aborted = false; }
1128 bool has_timed_out() { return _has_timed_out; }
1129 bool claimed() { return _claimed; }
1130
1131 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
1132
1133 // It grays the object by marking it and, if necessary, pushing it
1134 // on the local queue
1135 inline void deal_with_reference(oop obj);
1136
1137 // It scans an object and visits its children.
1138 void scan_object(oop obj);
1139
1140 // It pushes an object on the local queue.
1141 inline void push(oop obj);
1142
1143 // These two move entries to/from the global stack.
1144 void move_entries_to_global_stack();
1145 void get_entries_from_global_stack();
1146
1147 // It pops and scans objects from the local queue. If partially is
1148 // true, then it stops when the queue size is of a given limit. If
1149 // partially is false, then it stops when the queue is empty.
1150 void drain_local_queue(bool partially);
1151 // It moves entries from the global stack to the local queue and
1152 // drains the local queue. If partially is true, then it stops when
1153 // both the global stack and the local queue reach a given size. If
1154 // partially if false, it tries to empty them totally.
1155 void drain_global_stack(bool partially);
1156 // It keeps picking SATB buffers and processing them until no SATB
1157 // buffers are available.
1158 void drain_satb_buffers();
1159
1160 // moves the local finger to a new location
1161 inline void move_finger_to(HeapWord* new_finger) {
1162 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1163 _finger = new_finger;
1164 }
1165
1166 CMTask(int task_num, ConcurrentMark *cm,
1167 size_t* marked_bytes, BitMap* card_bm,
1168 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1169
1170 // it prints statistics associated with this task
1171 void print_stats();
1172
1173 #if _MARKING_STATS_
1174 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1175 #endif // _MARKING_STATS_
1176 };
1177
1178 // Class that's used to to print out per-region liveness
1179 // information. It's currently used at the end of marking and also
1180 // after we sort the old regions at the end of the cleanup operation.
1181 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1182 private:
1183 outputStream* _out;
1184
1185 // Accumulators for these values.
1186 size_t _total_used_bytes;
1187 size_t _total_capacity_bytes;
1188 size_t _total_prev_live_bytes;
1189 size_t _total_next_live_bytes;
1190
1191 // These are set up when we come across a "stars humongous" region
1192 // (as this is where most of this information is stored, not in the
1193 // subsequent "continues humongous" regions). After that, for every
1194 // region in a given humongous region series we deduce the right
1195 // values for it by simply subtracting the appropriate amount from
1196 // these fields. All these values should reach 0 after we've visited
1197 // the last region in the series.
1198 size_t _hum_used_bytes;
1199 size_t _hum_capacity_bytes;
1200 size_t _hum_prev_live_bytes;
1201 size_t _hum_next_live_bytes;
1202
1203 static double perc(size_t val, size_t total) {
1204 if (total == 0) {
1205 return 0.0;
1206 } else {
1207 return 100.0 * ((double) val / (double) total);
1208 }
1209 }
1210
1211 static double bytes_to_mb(size_t val) {
1212 return (double) val / (double) M;
1213 }
1214
1215 // See the .cpp file.
1216 size_t get_hum_bytes(size_t* hum_bytes);
1217 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1218 size_t* prev_live_bytes, size_t* next_live_bytes);
1219
1220 public:
1221 // The header and footer are printed in the constructor and
1222 // destructor respectively.
1223 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1224 virtual bool doHeapRegion(HeapRegion* r);
1225 ~G1PrintRegionLivenessInfoClosure();
1226 };
1227
1228 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP