1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
27
28 #include "classfile/javaClasses.hpp"
29 #include "gc/g1/g1RegionToSpaceMapper.hpp"
30 #include "gc/g1/heapRegionSet.hpp"
31 #include "gc/shared/taskqueue.hpp"
32
33 class G1CollectedHeap;
34 class G1CMBitMap;
35 class G1CMTask;
36 class G1ConcurrentMark;
37 typedef GenericTaskQueue<oop, mtGC> G1CMTaskQueue;
38 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
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 G1CMBitMapRO 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 G1CMBitMapRO(int shifter);
67
68 // inquiries
69 HeapWord* startWord() const { return _bmStartWord; }
70 // the following is one past the last word in space
71 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
72
73 // read marks
74
75 bool isMarked(HeapWord* addr) const {
76 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
77 "outside underlying space?");
78 return _bm.at(heapWordToOffset(addr));
79 }
80
81 // iteration
82 inline bool iterate(BitMapClosure* cl, MemRegion mr);
83
84 // Return the address corresponding to the next marked bit at or after
85 // "addr", and before "limit", if "limit" is non-NULL. If there is no
86 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
87 HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
88 const HeapWord* limit = NULL) const;
89
90 // conversion utilities
91 HeapWord* offsetToHeapWord(size_t offset) const {
92 return _bmStartWord + (offset << _shifter);
93 }
94 size_t heapWordToOffset(const HeapWord* addr) const {
95 return pointer_delta(addr, _bmStartWord) >> _shifter;
96 }
97
98 // The argument addr should be the start address of a valid object
99 inline HeapWord* nextObject(HeapWord* addr);
100
101 void print_on_error(outputStream* st, const char* prefix) const;
102
103 // debugging
104 NOT_PRODUCT(bool covers(MemRegion rs) const;)
105 };
106
107 class G1CMBitMapMappingChangedListener : public G1MappingChangedListener {
108 private:
109 G1CMBitMap* _bm;
110 public:
111 G1CMBitMapMappingChangedListener() : _bm(NULL) {}
112
113 void set_bitmap(G1CMBitMap* bm) { _bm = bm; }
114
115 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
116 };
117
118 class G1CMBitMap : public G1CMBitMapRO {
119 private:
120 G1CMBitMapMappingChangedListener _listener;
121
122 public:
123 static size_t compute_size(size_t heap_size);
124 // Returns the amount of bytes on the heap between two marks in the bitmap.
125 static size_t mark_distance();
126 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
127 // mark bitmap corresponds to. This is the same as the mark distance above.
128 static size_t heap_map_factor() {
129 return mark_distance();
130 }
131
132 G1CMBitMap() : G1CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
133
134 // Initializes the underlying BitMap to cover the given area.
135 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
136
137 // Write marks.
138 inline void mark(HeapWord* addr);
139 inline void clear(HeapWord* addr);
140 inline bool parMark(HeapWord* addr);
141
142 void clear_range(MemRegion mr);
143 };
144
145 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
146 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC {
147 VirtualSpace _virtual_space; // Underlying backing store for actual stack
148 G1ConcurrentMark* _cm;
149 oop* _base; // bottom of stack
150 jint _index; // one more than last occupied index
151 jint _capacity; // max #elements
152 jint _saved_index; // value of _index saved at start of GC
153
154 bool _overflow;
155 bool _should_expand;
156
157 public:
158 G1CMMarkStack(G1ConcurrentMark* cm);
159 ~G1CMMarkStack();
160
161 bool allocate(size_t capacity);
162
163 // Pushes the first "n" elements of "ptr_arr" on the stack.
164 // Locking impl: concurrency is allowed only with
165 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
166 // locking strategy.
167 void par_push_arr(oop* ptr_arr, int n);
168
169 // If returns false, the array was empty. Otherwise, removes up to "max"
170 // elements from the stack, and transfers them to "ptr_arr" in an
171 // unspecified order. The actual number transferred is given in "n" ("n
172 // == 0" is deliberately redundant with the return value.) Locking impl:
173 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
174 // operations, which use the same locking strategy.
175 bool par_pop_arr(oop* ptr_arr, int max, int* n);
176
177 bool isEmpty() { return _index == 0; }
178 int maxElems() { return _capacity; }
179
180 bool overflow() { return _overflow; }
181 void clear_overflow() { _overflow = false; }
182
183 bool should_expand() const { return _should_expand; }
184 void set_should_expand();
185
186 // Expand the stack, typically in response to an overflow condition
187 void expand();
188
189 int size() { return _index; }
190
191 void setEmpty() { _index = 0; clear_overflow(); }
192
193 // Record the current index.
194 void note_start_of_gc();
195
196 // Make sure that we have not added any entries to the stack during GC.
197 void note_end_of_gc();
198
199 // Apply fn to each oop in the mark stack, up to the bound recorded
200 // via one of the above "note" functions. The mark stack must not
201 // be modified while iterating.
202 template<typename Fn> void iterate(Fn fn);
203 };
204
205 class YoungList;
206
207 // Root Regions are regions that are not empty at the beginning of a
208 // marking cycle and which we might collect during an evacuation pause
209 // while the cycle is active. Given that, during evacuation pauses, we
210 // do not copy objects that are explicitly marked, what we have to do
211 // for the root regions is to scan them and mark all objects reachable
212 // from them. According to the SATB assumptions, we only need to visit
213 // each object once during marking. So, as long as we finish this scan
214 // before the next evacuation pause, we can copy the objects from the
215 // root regions without having to mark them or do anything else to them.
216 //
217 // Currently, we only support root region scanning once (at the start
218 // of the marking cycle) and the root regions are all the survivor
219 // regions populated during the initial-mark pause.
220 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC {
221 private:
222 YoungList* _young_list;
223 G1ConcurrentMark* _cm;
224
225 volatile bool _scan_in_progress;
226 volatile bool _should_abort;
227 HeapRegion* volatile _next_survivor;
228
229 void notify_scan_done();
230
231 public:
232 G1CMRootRegions();
233 // We actually do most of the initialization in this method.
234 void init(G1CollectedHeap* g1h, G1ConcurrentMark* cm);
235
236 // Reset the claiming / scanning of the root regions.
237 void prepare_for_scan();
238
239 // Forces get_next() to return NULL so that the iteration aborts early.
240 void abort() { _should_abort = true; }
241
242 // Return true if the CM thread are actively scanning root regions,
243 // false otherwise.
244 bool scan_in_progress() { return _scan_in_progress; }
245
246 // Claim the next root region to scan atomically, or return NULL if
247 // all have been claimed.
248 HeapRegion* claim_next();
249
250 void cancel_scan();
251
252 // Flag that we're done with root region scanning and notify anyone
253 // who's waiting on it. If aborted is false, assume that all regions
254 // have been claimed.
255 void scan_finished();
256
257 // If CM threads are still scanning root regions, wait until they
258 // are done. Return true if we had to wait, false otherwise.
259 bool wait_until_scan_finished();
260 };
261
262 class ConcurrentMarkThread;
263
264 class G1ConcurrentMark: public CHeapObj<mtGC> {
265 friend class ConcurrentMarkThread;
266 friend class G1ParNoteEndTask;
267 friend class G1VerifyLiveDataClosure;
268 friend class G1CMRefProcTaskProxy;
269 friend class G1CMRefProcTaskExecutor;
270 friend class G1CMKeepAliveAndDrainClosure;
271 friend class G1CMDrainMarkingStackClosure;
272 friend class G1CMBitMapClosure;
273 friend class G1CMConcurrentMarkingTask;
274 friend class G1CMMarkStack;
275 friend class G1CMRemarkTask;
276 friend class G1CMTask;
277
278 protected:
279 ConcurrentMarkThread* _cmThread; // The thread doing the work
280 G1CollectedHeap* _g1h; // The heap
281 uint _parallel_marking_threads; // The number of marking
282 // threads we're using
283 uint _max_parallel_marking_threads; // Max number of marking
284 // threads we'll ever use
285 double _sleep_factor; // How much we have to sleep, with
286 // respect to the work we just did, to
287 // meet the marking overhead goal
288 double _marking_task_overhead; // Marking target overhead for
289 // a single task
290
291 FreeRegionList _cleanup_list;
292
293 // Concurrent marking support structures
294 G1CMBitMap _markBitMap1;
295 G1CMBitMap _markBitMap2;
296 G1CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap
297 G1CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
298
299 // Liveness count data. After marking G1 iterates over the recently gathered mark
300 // bitmap and records rough information about liveness on card and region basis.
301 // This information can be used for e.g. remembered set scrubbing.
302
303 // A set bit indicates whether the given region contains any live object.
304 BitMap _region_live_bm;
305 // A set bit indicates that the given card contains a live object.
306 BitMap _card_live_bm;
307
308 // Heap bounds
309 HeapWord* _heap_start;
310 HeapWord* _heap_end;
311
312 // Root region tracking and claiming
313 G1CMRootRegions _root_regions;
314
315 // For gray objects
316 G1CMMarkStack _markStack; // Grey objects behind global finger
317 HeapWord* volatile _finger; // The global finger, region aligned,
318 // always points to the end of the
319 // last claimed region
320
321 // Marking tasks
322 uint _max_worker_id;// Maximum worker id
323 uint _active_tasks; // Task num currently active
324 G1CMTask** _tasks; // Task queue array (max_worker_id len)
325 G1CMTaskQueueSet* _task_queues; // Task queue set
326 ParallelTaskTerminator _terminator; // For termination
327
328 // Two sync barriers that are used to synchronize tasks when an
329 // overflow occurs. The algorithm is the following. All tasks enter
330 // the first one to ensure that they have all stopped manipulating
331 // the global data structures. After they exit it, they re-initialize
332 // their data structures and task 0 re-initializes the global data
333 // structures. Then, they enter the second sync barrier. This
334 // ensure, that no task starts doing work before all data
335 // structures (local and global) have been re-initialized. When they
336 // exit it, they are free to start working again.
337 WorkGangBarrierSync _first_overflow_barrier_sync;
338 WorkGangBarrierSync _second_overflow_barrier_sync;
339
340 // This is set by any task, when an overflow on the global data
341 // structures is detected
342 volatile bool _has_overflown;
343 // True: marking is concurrent, false: we're in remark
344 volatile bool _concurrent;
345 // Set at the end of a Full GC so that marking aborts
346 volatile bool _has_aborted;
347
348 // Used when remark aborts due to an overflow to indicate that
349 // another concurrent marking phase should start
350 volatile bool _restart_for_overflow;
351
352 // This is true from the very start of concurrent marking until the
353 // point when all the tasks complete their work. It is really used
354 // to determine the points between the end of concurrent marking and
355 // time of remark.
356 volatile bool _concurrent_marking_in_progress;
357
358 // There would be a race between ConcurrentMarkThread and VMThread(ConcurrentMark::abort())
359 // to call ConcurrentGCTimer::register_gc_concurrent_end().
360 // And this variable is used to keep track of concurrent phase.
361 volatile uint _concurrent_phase_status;
362 // Concurrent phase is not yet started.
363 static const uint ConcPhaseNotStarted = 0;
364 // Concurrent phase is started.
365 static const uint ConcPhaseStarted = 1;
366 // Caller thread of ConcurrentGCTimer::register_gc_concurrent_end() is ending concurrent phase.
367 // So other thread should wait until the status to be changed to ConcPhaseNotStarted.
368 static const uint ConcPhaseStopping = 2;
369
370 // All of these times are in ms
371 NumberSeq _init_times;
372 NumberSeq _remark_times;
373 NumberSeq _remark_mark_times;
374 NumberSeq _remark_weak_ref_times;
375 NumberSeq _cleanup_times;
376 double _total_counting_time;
377 double _total_rs_scrub_time;
378
379 double* _accum_task_vtime; // Accumulated task vtime
380
381 WorkGang* _parallel_workers;
382
383 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
384 void weakRefsWork(bool clear_all_soft_refs);
385
386 void swapMarkBitMaps();
387
388 // Allocates and returns a zero-ed out "large" bitmap of the given size in bits.
389 // It is always allocated using virtual memory.
390 BitMap allocate_large_bitmap(BitMap::idx_t size_in_bits);
391 // Allocates the memory for all bitmaps used by the concurrent marking.
392 void allocate_internal_bitmaps();
393 // Pre-touches the internal bitmaps.
394 void pretouch_internal_bitmaps();
395
396 // It resets the global marking data structures, as well as the
397 // task local ones; should be called during initial mark.
398 void reset();
399
400 // Resets all the marking data structures. Called when we have to restart
401 // marking or when marking completes (via set_non_marking_state below).
402 void reset_marking_state(bool clear_overflow = true);
403
404 // We do this after we're done with marking so that the marking data
405 // structures are initialized to a sensible and predictable state.
406 void set_non_marking_state();
407
408 // Called to indicate how many threads are currently active.
409 void set_concurrency(uint active_tasks);
410
411 // It should be called to indicate which phase we're in (concurrent
412 // mark or remark) and how many threads are currently active.
413 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
414
415 // Prints all gathered CM-related statistics
416 void print_stats();
417
418 bool cleanup_list_is_empty() {
419 return _cleanup_list.is_empty();
420 }
421
422 // Accessor methods
423 uint parallel_marking_threads() const { return _parallel_marking_threads; }
424 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
425 double sleep_factor() { return _sleep_factor; }
426 double marking_task_overhead() { return _marking_task_overhead;}
427
428 HeapWord* finger() { return _finger; }
429 bool concurrent() { return _concurrent; }
430 uint active_tasks() { return _active_tasks; }
431 ParallelTaskTerminator* terminator() { return &_terminator; }
432
433 // It claims the next available region to be scanned by a marking
434 // task/thread. It might return NULL if the next region is empty or
435 // we have run out of regions. In the latter case, out_of_regions()
436 // determines whether we've really run out of regions or the task
437 // should call claim_region() again. This might seem a bit
438 // awkward. Originally, the code was written so that claim_region()
439 // either successfully returned with a non-empty region or there
440 // were no more regions to be claimed. The problem with this was
441 // that, in certain circumstances, it iterated over large chunks of
442 // the heap finding only empty regions and, while it was working, it
443 // was preventing the calling task to call its regular clock
444 // method. So, this way, each task will spend very little time in
445 // claim_region() and is allowed to call the regular clock method
446 // frequently.
447 HeapRegion* claim_region(uint worker_id);
448
449 // It determines whether we've run out of regions to scan. Note that
450 // the finger can point past the heap end in case the heap was expanded
451 // to satisfy an allocation without doing a GC. This is fine, because all
452 // objects in those regions will be considered live anyway because of
453 // SATB guarantees (i.e. their TAMS will be equal to bottom).
454 bool out_of_regions() { return _finger >= _heap_end; }
455
456 // Returns the task with the given id
457 G1CMTask* task(int id) {
458 assert(0 <= id && id < (int) _active_tasks,
459 "task id not within active bounds");
460 return _tasks[id];
461 }
462
463 // Returns the task queue with the given id
464 G1CMTaskQueue* task_queue(int id) {
465 assert(0 <= id && id < (int) _active_tasks,
466 "task queue id not within active bounds");
467 return (G1CMTaskQueue*) _task_queues->queue(id);
468 }
469
470 // Returns the task queue set
471 G1CMTaskQueueSet* task_queues() { return _task_queues; }
472
473 // Access / manipulation of the overflow flag which is set to
474 // indicate that the global stack has overflown
475 bool has_overflown() { return _has_overflown; }
476 void set_has_overflown() { _has_overflown = true; }
477 void clear_has_overflown() { _has_overflown = false; }
478 bool restart_for_overflow() { return _restart_for_overflow; }
479
480 // Methods to enter the two overflow sync barriers
481 void enter_first_sync_barrier(uint worker_id);
482 void enter_second_sync_barrier(uint worker_id);
483
484 // Card index of the bottom of the G1 heap. Used for biasing indices into
485 // the card bitmaps.
486 intptr_t _heap_bottom_card_num;
487
488 // Set to true when initialization is complete
489 bool _completed_initialization;
490
491 // end_timer, true to end gc timer after ending concurrent phase.
492 void register_concurrent_phase_end_common(bool end_timer);
493
494 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
495 // true, periodically insert checks to see if this method should exit prematurely.
496 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
497 public:
498 // Manipulation of the global mark stack.
499 // The push and pop operations are used by tasks for transfers
500 // between task-local queues and the global mark stack, and use
501 // locking for concurrency safety.
502 bool mark_stack_push(oop* arr, int n) {
503 _markStack.par_push_arr(arr, n);
504 if (_markStack.overflow()) {
505 set_has_overflown();
506 return false;
507 }
508 return true;
509 }
510 void mark_stack_pop(oop* arr, int max, int* n) {
511 _markStack.par_pop_arr(arr, max, n);
512 }
513 size_t mark_stack_size() { return _markStack.size(); }
514 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
515 bool mark_stack_overflow() { return _markStack.overflow(); }
516 bool mark_stack_empty() { return _markStack.isEmpty(); }
517
518 G1CMRootRegions* root_regions() { return &_root_regions; }
519
520 bool concurrent_marking_in_progress() {
521 return _concurrent_marking_in_progress;
522 }
523 void set_concurrent_marking_in_progress() {
524 _concurrent_marking_in_progress = true;
525 }
526 void clear_concurrent_marking_in_progress() {
527 _concurrent_marking_in_progress = false;
528 }
529
530 void register_concurrent_phase_start(const char* title);
531 void register_concurrent_phase_end();
532 // Ends both concurrent phase and timer.
533 void register_concurrent_gc_end_and_stop_timer();
534
535 void update_accum_task_vtime(int i, double vtime) {
536 _accum_task_vtime[i] += vtime;
537 }
538
539 double all_task_accum_vtime() {
540 double ret = 0.0;
541 for (uint i = 0; i < _max_worker_id; ++i)
542 ret += _accum_task_vtime[i];
543 return ret;
544 }
545
546 // Attempts to steal an object from the task queues of other tasks
547 bool try_stealing(uint worker_id, int* hash_seed, oop& obj);
548
549 G1ConcurrentMark(G1CollectedHeap* g1h,
550 G1RegionToSpaceMapper* prev_bitmap_storage,
551 G1RegionToSpaceMapper* next_bitmap_storage);
552 ~G1ConcurrentMark();
553
554 ConcurrentMarkThread* cmThread() { return _cmThread; }
555
556 G1CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
557 G1CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
558
559 // Returns the number of GC threads to be used in a concurrent
560 // phase based on the number of GC threads being used in a STW
561 // phase.
562 uint scale_parallel_threads(uint n_par_threads);
563
564 // Calculates the number of GC threads to be used in a concurrent phase.
565 uint calc_parallel_marking_threads();
566
567 // The following three are interaction between CM and
568 // G1CollectedHeap
569
570 // This notifies CM that a root during initial-mark needs to be
571 // grayed. It is MT-safe. hr is the region that
572 // contains the object and it's passed optionally from callers who
573 // might already have it (no point in recalculating it).
574 inline void grayRoot(oop obj,
575 HeapRegion* hr = NULL);
576
577 // Prepare internal data structures for the next mark cycle. This includes clearing
578 // the next mark bitmap and some internal data structures. This method is intended
579 // to be called concurrently to the mutator. It will yield to safepoint requests.
580 void cleanup_for_next_mark();
581
582 // Clear the previous marking bitmap during safepoint.
583 void clear_prev_bitmap(WorkGang* workers);
584
585 // Return whether the next mark bitmap has no marks set. To be used for assertions
586 // only. Will not yield to pause requests.
587 bool nextMarkBitmapIsClear();
588
589 // These two do the work that needs to be done before and after the
590 // initial root checkpoint. Since this checkpoint can be done at two
591 // different points (i.e. an explicit pause or piggy-backed on a
592 // young collection), then it's nice to be able to easily share the
593 // pre/post code. It might be the case that we can put everything in
594 // the post method. TP
595 void checkpointRootsInitialPre();
596 void checkpointRootsInitialPost();
597
598 // Scan all the root regions and mark everything reachable from
599 // them.
600 void scan_root_regions();
601
602 // Scan a single root region and mark everything reachable from it.
603 void scanRootRegion(HeapRegion* hr, uint worker_id);
604
605 // Do concurrent phase of marking, to a tentative transitive closure.
606 void mark_from_roots();
607
608 void checkpointRootsFinal(bool clear_all_soft_refs);
609 void checkpointRootsFinalWork();
610 void cleanup();
611 void complete_cleanup();
612
613 // Mark in the previous bitmap. NB: this is usually read-only, so use
614 // this carefully!
615 inline void markPrev(oop p);
616
617 // Clears marks for all objects in the given range, for the prev or
618 // next bitmaps. NB: the previous bitmap is usually
619 // read-only, so use this carefully!
620 void clearRangePrevBitmap(MemRegion mr);
621
622 // Notify data structures that a GC has started.
623 void note_start_of_gc() {
624 _markStack.note_start_of_gc();
625 }
626
627 // Notify data structures that a GC is finished.
628 void note_end_of_gc() {
629 _markStack.note_end_of_gc();
630 }
631
632 // Verify that there are no CSet oops on the stacks (taskqueues /
633 // global mark stack) and fingers (global / per-task).
634 // If marking is not in progress, it's a no-op.
635 void verify_no_cset_oops() PRODUCT_RETURN;
636
637 inline bool isPrevMarked(oop p) const;
638
639 inline bool do_yield_check(uint worker_i = 0);
640
641 // Abandon current marking iteration due to a Full GC.
642 void abort();
643
644 bool has_aborted() { return _has_aborted; }
645
646 void print_summary_info();
647
648 void print_worker_threads_on(outputStream* st) const;
649
650 void print_on_error(outputStream* st) const;
651
652 // Returns the card number of the bottom of the G1 heap.
653 // Used in biasing indices into accounting card bitmaps.
654 intptr_t heap_bottom_card_num() const {
655 return _heap_bottom_card_num;
656 }
657
658 // Returns the index in the per-card liveness count bitmap
659 // for the given address
660 inline BitMap::idx_t card_live_bitmap_index_for(HeapWord* addr);
661
662 // Attempts to mark the given object on the next mark bitmap.
663 inline bool par_mark(oop obj);
664
665 // Returns true if initialization was successfully completed.
666 bool completed_initialization() const {
667 return _completed_initialization;
668 }
669
670 private:
671 // Clear (Reset) all liveness count data.
672 void clear_all_live_data(WorkGang* workers);
673
674 // Verify all of the above data structures that they are in initial state.
675 void verify_all_live_data();
676
677 // Aggregates the per-card liveness data based on the current marking. Also sets
678 // the amount of marked bytes for each region.
679 void create_live_data();
680
681 // Verification routine
682 void verify_live_data();
683 };
684
685 // A class representing a marking task.
686 class G1CMTask : public TerminatorTerminator {
687 private:
688 enum PrivateConstants {
689 // the regular clock call is called once the scanned words reaches
690 // this limit
691 words_scanned_period = 12*1024,
692 // the regular clock call is called once the number of visited
693 // references reaches this limit
694 refs_reached_period = 384,
695 // initial value for the hash seed, used in the work stealing code
696 init_hash_seed = 17,
697 // how many entries will be transferred between global stack and
698 // local queues
699 global_stack_transfer_size = 16
700 };
701
702 uint _worker_id;
703 G1CollectedHeap* _g1h;
704 G1ConcurrentMark* _cm;
705 G1CMBitMap* _nextMarkBitMap;
706 // the task queue of this task
707 G1CMTaskQueue* _task_queue;
708 private:
709 // the task queue set---needed for stealing
710 G1CMTaskQueueSet* _task_queues;
711 // indicates whether the task has been claimed---this is only for
712 // debugging purposes
713 bool _claimed;
714
715 // number of calls to this task
716 int _calls;
717
718 // when the virtual timer reaches this time, the marking step should
719 // exit
720 double _time_target_ms;
721 // the start time of the current marking step
722 double _start_time_ms;
723
724 // the oop closure used for iterations over oops
725 G1CMOopClosure* _cm_oop_closure;
726
727 // the region this task is scanning, NULL if we're not scanning any
728 HeapRegion* _curr_region;
729 // the local finger of this task, NULL if we're not scanning a region
730 HeapWord* _finger;
731 // limit of the region this task is scanning, NULL if we're not scanning one
732 HeapWord* _region_limit;
733
734 // the number of words this task has scanned
735 size_t _words_scanned;
736 // When _words_scanned reaches this limit, the regular clock is
737 // called. Notice that this might be decreased under certain
738 // circumstances (i.e. when we believe that we did an expensive
739 // operation).
740 size_t _words_scanned_limit;
741 // the initial value of _words_scanned_limit (i.e. what it was
742 // before it was decreased).
743 size_t _real_words_scanned_limit;
744
745 // the number of references this task has visited
746 size_t _refs_reached;
747 // When _refs_reached reaches this limit, the regular clock is
748 // called. Notice this this might be decreased under certain
749 // circumstances (i.e. when we believe that we did an expensive
750 // operation).
751 size_t _refs_reached_limit;
752 // the initial value of _refs_reached_limit (i.e. what it was before
753 // it was decreased).
754 size_t _real_refs_reached_limit;
755
756 // used by the work stealing stuff
757 int _hash_seed;
758 // if this is true, then the task has aborted for some reason
759 bool _has_aborted;
760 // set when the task aborts because it has met its time quota
761 bool _has_timed_out;
762 // true when we're draining SATB buffers; this avoids the task
763 // aborting due to SATB buffers being available (as we're already
764 // dealing with them)
765 bool _draining_satb_buffers;
766
767 // number sequence of past step times
768 NumberSeq _step_times_ms;
769 // elapsed time of this task
770 double _elapsed_time_ms;
771 // termination time of this task
772 double _termination_time_ms;
773 // when this task got into the termination protocol
774 double _termination_start_time_ms;
775
776 // true when the task is during a concurrent phase, false when it is
777 // in the remark phase (so, in the latter case, we do not have to
778 // check all the things that we have to check during the concurrent
779 // phase, i.e. SATB buffer availability...)
780 bool _concurrent;
781
782 TruncatedSeq _marking_step_diffs_ms;
783
784 // it updates the local fields after this task has claimed
785 // a new region to scan
786 void setup_for_region(HeapRegion* hr);
787 // it brings up-to-date the limit of the region
788 void update_region_limit();
789
790 // called when either the words scanned or the refs visited limit
791 // has been reached
792 void reached_limit();
793 // recalculates the words scanned and refs visited limits
794 void recalculate_limits();
795 // decreases the words scanned and refs visited limits when we reach
796 // an expensive operation
797 void decrease_limits();
798 // it checks whether the words scanned or refs visited reached their
799 // respective limit and calls reached_limit() if they have
800 void check_limits() {
801 if (_words_scanned >= _words_scanned_limit ||
802 _refs_reached >= _refs_reached_limit) {
803 reached_limit();
804 }
805 }
806 // this is supposed to be called regularly during a marking step as
807 // it checks a bunch of conditions that might cause the marking step
808 // to abort
809 void regular_clock_call();
810 bool concurrent() { return _concurrent; }
811
812 // Test whether obj might have already been passed over by the
813 // mark bitmap scan, and so needs to be pushed onto the mark stack.
814 bool is_below_finger(oop obj, HeapWord* global_finger) const;
815
816 template<bool scan> void process_grey_object(oop obj);
817
818 public:
819 // It resets the task; it should be called right at the beginning of
820 // a marking phase.
821 void reset(G1CMBitMap* _nextMarkBitMap);
822 // it clears all the fields that correspond to a claimed region.
823 void clear_region_fields();
824
825 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
826
827 // The main method of this class which performs a marking step
828 // trying not to exceed the given duration. However, it might exit
829 // prematurely, according to some conditions (i.e. SATB buffers are
830 // available for processing).
831 void do_marking_step(double target_ms,
832 bool do_termination,
833 bool is_serial);
834
835 // These two calls start and stop the timer
836 void record_start_time() {
837 _elapsed_time_ms = os::elapsedTime() * 1000.0;
838 }
839 void record_end_time() {
840 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
841 }
842
843 // returns the worker ID associated with this task.
844 uint worker_id() { return _worker_id; }
845
846 // From TerminatorTerminator. It determines whether this task should
847 // exit the termination protocol after it's entered it.
848 virtual bool should_exit_termination();
849
850 // Resets the local region fields after a task has finished scanning a
851 // region; or when they have become stale as a result of the region
852 // being evacuated.
853 void giveup_current_region();
854
855 HeapWord* finger() { return _finger; }
856
857 bool has_aborted() { return _has_aborted; }
858 void set_has_aborted() { _has_aborted = true; }
859 void clear_has_aborted() { _has_aborted = false; }
860 bool has_timed_out() { return _has_timed_out; }
861 bool claimed() { return _claimed; }
862
863 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
864
865 // Increment the number of references this task has visited.
866 void increment_refs_reached() { ++_refs_reached; }
867
868 // Grey the object by marking it. If not already marked, push it on
869 // the local queue if below the finger.
870 // Precondition: obj is below region's NTAMS.
871 inline void make_reference_grey(oop obj);
872
873 // Grey the object (by calling make_grey_reference) if required,
874 // e.g. obj is below its containing region's NTAMS.
875 // Precondition: obj is a valid heap object.
876 inline void deal_with_reference(oop obj);
877
878 // It scans an object and visits its children.
879 inline void scan_object(oop obj);
880
881 // It pushes an object on the local queue.
882 inline void push(oop obj);
883
884 // These two move entries to/from the global stack.
885 void move_entries_to_global_stack();
886 void get_entries_from_global_stack();
887
888 // It pops and scans objects from the local queue. If partially is
889 // true, then it stops when the queue size is of a given limit. If
890 // partially is false, then it stops when the queue is empty.
891 void drain_local_queue(bool partially);
892 // It moves entries from the global stack to the local queue and
893 // drains the local queue. If partially is true, then it stops when
894 // both the global stack and the local queue reach a given size. If
895 // partially if false, it tries to empty them totally.
896 void drain_global_stack(bool partially);
897 // It keeps picking SATB buffers and processing them until no SATB
898 // buffers are available.
899 void drain_satb_buffers();
900
901 // moves the local finger to a new location
902 inline void move_finger_to(HeapWord* new_finger) {
903 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
904 _finger = new_finger;
905 }
906
907 G1CMTask(uint worker_id,
908 G1ConcurrentMark *cm,
909 G1CMTaskQueue* task_queue,
910 G1CMTaskQueueSet* task_queues);
911
912 // it prints statistics associated with this task
913 void print_stats();
914 };
915
916 // Class that's used to to print out per-region liveness
917 // information. It's currently used at the end of marking and also
918 // after we sort the old regions at the end of the cleanup operation.
919 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
920 private:
921 // Accumulators for these values.
922 size_t _total_used_bytes;
923 size_t _total_capacity_bytes;
924 size_t _total_prev_live_bytes;
925 size_t _total_next_live_bytes;
926
927 // These are set up when we come across a "stars humongous" region
928 // (as this is where most of this information is stored, not in the
929 // subsequent "continues humongous" regions). After that, for every
930 // region in a given humongous region series we deduce the right
931 // values for it by simply subtracting the appropriate amount from
932 // these fields. All these values should reach 0 after we've visited
933 // the last region in the series.
934 size_t _hum_used_bytes;
935 size_t _hum_capacity_bytes;
936 size_t _hum_prev_live_bytes;
937 size_t _hum_next_live_bytes;
938
939 // Accumulator for the remembered set size
940 size_t _total_remset_bytes;
941
942 // Accumulator for strong code roots memory size
943 size_t _total_strong_code_roots_bytes;
944
945 static double perc(size_t val, size_t total) {
946 if (total == 0) {
947 return 0.0;
948 } else {
949 return 100.0 * ((double) val / (double) total);
950 }
951 }
952
953 static double bytes_to_mb(size_t val) {
954 return (double) val / (double) M;
955 }
956
957 // See the .cpp file.
958 size_t get_hum_bytes(size_t* hum_bytes);
959 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
960 size_t* prev_live_bytes, size_t* next_live_bytes);
961
962 public:
963 // The header and footer are printed in the constructor and
964 // destructor respectively.
965 G1PrintRegionLivenessInfoClosure(const char* phase_name);
966 virtual bool doHeapRegion(HeapRegion* r);
967 ~G1PrintRegionLivenessInfoClosure();
968 };
969
970 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP