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