1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_GC_G1_G1CONCURRENTMARK_HPP
26 #define SHARE_GC_G1_G1CONCURRENTMARK_HPP
27
28 #include "gc/g1/g1ConcurrentMarkBitMap.hpp"
29 #include "gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp"
30 #include "gc/g1/g1HeapVerifier.hpp"
31 #include "gc/g1/g1RegionMarkStatsCache.hpp"
32 #include "gc/g1/heapRegionSet.hpp"
33 #include "gc/shared/taskqueue.hpp"
34 #include "gc/shared/verifyOption.hpp"
35 #include "memory/allocation.hpp"
36 #include "utilities/compilerWarnings.hpp"
37
38 class ConcurrentGCTimer;
39 class G1ConcurrentMarkThread;
40 class G1CollectedHeap;
41 class G1CMOopClosure;
42 class G1CMTask;
43 class G1ConcurrentMark;
44 class G1OldTracer;
45 class G1RegionToSpaceMapper;
46 class G1SurvivorRegions;
47
48 PRAGMA_DIAG_PUSH
49 // warning C4522: multiple assignment operators specified
50 PRAGMA_DISABLE_MSVC_WARNING(4522)
51
52 // This is a container class for either an oop or a continuation address for
53 // mark stack entries. Both are pushed onto the mark stack.
54 class G1TaskQueueEntry {
55 private:
56 void* _holder;
57
58 static const uintptr_t ArraySliceBit = 1;
59
60 G1TaskQueueEntry(oop obj) : _holder(obj) {
61 assert(_holder != NULL, "Not allowed to set NULL task queue element");
62 }
63 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { }
64 public:
65 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; }
66 G1TaskQueueEntry() : _holder(NULL) { }
67
68 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); }
69 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); }
70
71 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) {
72 _holder = t._holder;
73 return *this;
74 }
75
76 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile {
77 _holder = t._holder;
78 return *this;
79 }
80
81 oop obj() const {
82 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder));
83 return (oop)_holder;
84 }
85
86 HeapWord* slice() const {
87 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder));
88 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit);
89 }
90
91 bool is_oop() const { return !is_array_slice(); }
92 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; }
93 bool is_null() const { return _holder == NULL; }
94 };
95
96 PRAGMA_DIAG_POP
97
98 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue;
99 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
100
101 // Closure used by CM during concurrent reference discovery
102 // and reference processing (during remarking) to determine
103 // if a particular object is alive. It is primarily used
104 // to determine if referents of discovered reference objects
105 // are alive. An instance is also embedded into the
106 // reference processor as the _is_alive_non_header field
107 class G1CMIsAliveClosure : public BoolObjectClosure {
108 G1CollectedHeap* _g1h;
109 public:
110 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
111 bool do_object_b(oop obj);
112 };
113
114 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure {
115 G1CollectedHeap* _g1h;
116 public:
117 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
118 bool do_object_b(oop obj);
119 };
120
121 // Represents the overflow mark stack used by concurrent marking.
122 //
123 // Stores oops in a huge buffer in virtual memory that is always fully committed.
124 // Resizing may only happen during a STW pause when the stack is empty.
125 //
126 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
127 // stack memory is split into evenly sized chunks of oops. Users can only
128 // add or remove entries on that basis.
129 // Chunks are filled in increasing address order. Not completely filled chunks
130 // have a NULL element as a terminating element.
131 //
132 // Every chunk has a header containing a single pointer element used for memory
133 // management. This wastes some space, but is negligible (< .1% with current sizing).
134 //
135 // Memory management is done using a mix of tracking a high water-mark indicating
136 // that all chunks at a lower address are valid chunks, and a singly linked free
137 // list connecting all empty chunks.
138 class G1CMMarkStack {
139 public:
140 // Number of TaskQueueEntries that can fit in a single chunk.
141 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */;
142 private:
143 struct TaskQueueEntryChunk {
144 TaskQueueEntryChunk* next;
145 G1TaskQueueEntry data[EntriesPerChunk];
146 };
147
148 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack.
149
150 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area.
151 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements.
152
153 char _pad0[DEFAULT_CACHE_LINE_SIZE];
154 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
155 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)];
156 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data.
157 volatile size_t _chunks_in_chunk_list;
158 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)];
159
160 volatile size_t _hwm; // High water mark within the reserved space.
161 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
162
163 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
164 // NULL if out of memory.
165 TaskQueueEntryChunk* allocate_new_chunk();
166
167 // Atomically add the given chunk to the list.
168 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem);
169 // Atomically remove and return a chunk from the given list. Returns NULL if the
170 // list is empty.
171 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list);
172
173 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem);
174 void add_chunk_to_free_list(TaskQueueEntryChunk* elem);
175
176 TaskQueueEntryChunk* remove_chunk_from_chunk_list();
177 TaskQueueEntryChunk* remove_chunk_from_free_list();
178
179 // Resizes the mark stack to the given new capacity. Releases any previous
180 // memory if successful.
181 bool resize(size_t new_capacity);
182
183 public:
184 G1CMMarkStack();
185 ~G1CMMarkStack();
186
187 // Alignment and minimum capacity of this mark stack in number of oops.
188 static size_t capacity_alignment();
189
190 // Allocate and initialize the mark stack with the given number of oops.
191 bool initialize(size_t initial_capacity, size_t max_capacity);
192
193 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark
194 // stack. If less than EntriesPerChunk elements are to be pushed, the array must
195 // be terminated with a NULL.
196 // Returns whether the buffer contents were successfully pushed to the global mark
197 // stack.
198 bool par_push_chunk(G1TaskQueueEntry* buffer);
199
200 // Pops a chunk from this mark stack, copying them into the given buffer. This
201 // chunk may contain up to EntriesPerChunk elements. If there are less, the last
202 // element in the array is a NULL pointer.
203 bool par_pop_chunk(G1TaskQueueEntry* buffer);
204
205 // Return whether the chunk list is empty. Racy due to unsynchronized access to
206 // _chunk_list.
207 bool is_empty() const { return _chunk_list == NULL; }
208
209 size_t capacity() const { return _chunk_capacity; }
210
211 // Expand the stack, typically in response to an overflow condition
212 void expand();
213
214 // Return the approximate number of oops on this mark stack. Racy due to
215 // unsynchronized access to _chunks_in_chunk_list.
216 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; }
217
218 void set_empty();
219
220 // Apply Fn to every oop on the mark stack. The mark stack must not
221 // be modified while iterating.
222 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
223 };
224
225 // Root MemRegions are memory areas that contain objects which references are
226 // roots wrt to the marking. They must be scanned before marking to maintain the
227 // SATB invariant.
228 // Typically they contain the areas from nTAMS to top of the regions.
229 // We could scan and mark through these objects during the initial-mark pause, but for
230 // pause time reasons we move this work to the concurrent phase.
231 // We need to complete this procedure before the next GC because it might determine
232 // that some of these "root objects" are dead, potentially dropping some required
233 // references.
234 // Root MemRegions comprise of the contents of survivor regions at the end
235 // of the GC, and any objects copied into the old gen during GC.
236 class G1CMRootMemRegions {
237 // The set of root MemRegions.
238 MemRegion* _root_regions;
239 size_t const _max_regions;
240
241 volatile size_t _num_root_regions; // Actual number of root regions.
242
243 volatile size_t _claimed_root_regions; // Number of root regions currently claimed.
244
245 volatile bool _scan_in_progress;
246 volatile bool _should_abort;
247
248 void notify_scan_done();
249
250 public:
251 G1CMRootMemRegions(uint const max_regions);
252 ~G1CMRootMemRegions();
253
254 // Reset the data structure to allow addition of new root regions.
255 void reset();
256
257 void add(HeapWord* start, HeapWord* end);
258
259 // Reset the claiming / scanning of the root regions.
260 void prepare_for_scan();
261
262 // Forces get_next() to return NULL so that the iteration aborts early.
263 void abort() { _should_abort = true; }
264
265 // Return true if the CM thread are actively scanning root regions,
266 // false otherwise.
267 bool scan_in_progress() { return _scan_in_progress; }
268
269 // Claim the next root MemRegion to scan atomically, or return NULL if
270 // all have been claimed.
271 MemRegion* claim_next();
272
273 // The number of root regions to scan.
274 uint num_root_regions() const;
275
276 void cancel_scan();
277
278 // Flag that we're done with root region scanning and notify anyone
279 // who's waiting on it. If aborted is false, assume that all regions
280 // have been claimed.
281 void scan_finished();
282
283 // If CM threads are still scanning root regions, wait until they
284 // are done. Return true if we had to wait, false otherwise.
285 bool wait_until_scan_finished();
286 };
287
288 // This class manages data structures and methods for doing liveness analysis in
289 // G1's concurrent cycle.
290 class G1ConcurrentMark : public CHeapObj<mtGC> {
291 friend class G1ConcurrentMarkThread;
292 friend class G1CMRefProcTaskProxy;
293 friend class G1CMRefProcTaskExecutor;
294 friend class G1CMKeepAliveAndDrainClosure;
295 friend class G1CMDrainMarkingStackClosure;
296 friend class G1CMBitMapClosure;
297 friend class G1CMConcurrentMarkingTask;
298 friend class G1CMRemarkTask;
299 friend class G1CMTask;
300
301 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work
302 G1CollectedHeap* _g1h; // The heap
303 bool _completed_initialization; // Set to true when initialization is complete
304
305 // Concurrent marking support structures
306 G1CMBitMap _mark_bitmap_1;
307 G1CMBitMap _mark_bitmap_2;
308 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap
309 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap
310
311 // Heap bounds
312 MemRegion const _heap;
313
314 // Root region tracking and claiming
315 G1CMRootMemRegions _root_regions;
316
317 // For grey objects
318 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
319 HeapWord* volatile _finger; // The global finger, region aligned,
320 // always pointing to the end of the
321 // last claimed region
322
323 uint _worker_id_offset;
324 uint _max_num_tasks; // Maximum number of marking tasks
325 uint _num_active_tasks; // Number of tasks currently active
326 G1CMTask** _tasks; // Task queue array (max_worker_id length)
327
328 G1CMTaskQueueSet* _task_queues; // Task queue set
329 TaskTerminator _terminator; // For termination
330
331 // Two sync barriers that are used to synchronize tasks when an
332 // overflow occurs. The algorithm is the following. All tasks enter
333 // the first one to ensure that they have all stopped manipulating
334 // the global data structures. After they exit it, they re-initialize
335 // their data structures and task 0 re-initializes the global data
336 // structures. Then, they enter the second sync barrier. This
337 // ensure, that no task starts doing work before all data
338 // structures (local and global) have been re-initialized. When they
339 // exit it, they are free to start working again.
340 WorkGangBarrierSync _first_overflow_barrier_sync;
341 WorkGangBarrierSync _second_overflow_barrier_sync;
342
343 // This is set by any task, when an overflow on the global data
344 // structures is detected
345 volatile bool _has_overflown;
346 // True: marking is concurrent, false: we're in remark
347 volatile bool _concurrent;
348 // Set at the end of a Full GC so that marking aborts
349 volatile bool _has_aborted;
350
351 // Used when remark aborts due to an overflow to indicate that
352 // another concurrent marking phase should start
353 volatile bool _restart_for_overflow;
354
355 ConcurrentGCTimer* _gc_timer_cm;
356
357 G1OldTracer* _gc_tracer_cm;
358
359 // Timing statistics. All of them are in ms
360 NumberSeq _init_times;
361 NumberSeq _remark_times;
362 NumberSeq _remark_mark_times;
363 NumberSeq _remark_weak_ref_times;
364 NumberSeq _cleanup_times;
365 double _total_cleanup_time;
366
367 double* _accum_task_vtime; // Accumulated task vtime
368
369 WorkGang* _concurrent_workers;
370 uint _num_concurrent_workers; // The number of marking worker threads we're using
371 uint _max_concurrent_workers; // Maximum number of marking worker threads
372
373 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller);
374
375 void finalize_marking();
376
377 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes);
378 void weak_refs_work(bool clear_all_soft_refs);
379
380 void report_object_count(bool mark_completed);
381
382 void swap_mark_bitmaps();
383
384 void reclaim_empty_regions();
385
386 // After reclaiming empty regions, update heap sizes.
387 void compute_new_sizes();
388
389 // Clear statistics gathered during the concurrent cycle for the given region after
390 // it has been reclaimed.
391 void clear_statistics(HeapRegion* r);
392
393 // Resets the global marking data structures, as well as the
394 // task local ones; should be called during initial mark.
395 void reset();
396
397 // Resets all the marking data structures. Called when we have to restart
398 // marking or when marking completes (via set_non_marking_state below).
399 void reset_marking_for_restart();
400
401 // We do this after we're done with marking so that the marking data
402 // structures are initialized to a sensible and predictable state.
403 void reset_at_marking_complete();
404
405 // Called to indicate how many threads are currently active.
406 void set_concurrency(uint active_tasks);
407
408 // Should be called to indicate which phase we're in (concurrent
409 // mark or remark) and how many threads are currently active.
410 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
411
412 // Prints all gathered CM-related statistics
413 void print_stats();
414
415 HeapWord* finger() { return _finger; }
416 bool concurrent() { return _concurrent; }
417 uint active_tasks() { return _num_active_tasks; }
418 ParallelTaskTerminator* terminator() const { return _terminator.terminator(); }
419
420 // Claims the next available region to be scanned by a marking
421 // task/thread. It might return NULL if the next region is empty or
422 // we have run out of regions. In the latter case, out_of_regions()
423 // determines whether we've really run out of regions or the task
424 // should call claim_region() again. This might seem a bit
425 // awkward. Originally, the code was written so that claim_region()
426 // either successfully returned with a non-empty region or there
427 // were no more regions to be claimed. The problem with this was
428 // that, in certain circumstances, it iterated over large chunks of
429 // the heap finding only empty regions and, while it was working, it
430 // was preventing the calling task to call its regular clock
431 // method. So, this way, each task will spend very little time in
432 // claim_region() and is allowed to call the regular clock method
433 // frequently.
434 HeapRegion* claim_region(uint worker_id);
435
436 // Determines whether we've run out of regions to scan. Note that
437 // the finger can point past the heap end in case the heap was expanded
438 // to satisfy an allocation without doing a GC. This is fine, because all
439 // objects in those regions will be considered live anyway because of
440 // SATB guarantees (i.e. their TAMS will be equal to bottom).
441 bool out_of_regions() { return _finger >= _heap.end(); }
442
443 // Returns the task with the given id
444 G1CMTask* task(uint id) {
445 // During initial mark we use the parallel gc threads to do some work, so
446 // we can only compare against _max_num_tasks.
447 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks);
448 return _tasks[id];
449 }
450
451 // Access / manipulation of the overflow flag which is set to
452 // indicate that the global stack has overflown
453 bool has_overflown() { return _has_overflown; }
454 void set_has_overflown() { _has_overflown = true; }
455 void clear_has_overflown() { _has_overflown = false; }
456 bool restart_for_overflow() { return _restart_for_overflow; }
457
458 // Methods to enter the two overflow sync barriers
459 void enter_first_sync_barrier(uint worker_id);
460 void enter_second_sync_barrier(uint worker_id);
461
462 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
463 // true, periodically insert checks to see if this method should exit prematurely.
464 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
465
466 // Region statistics gathered during marking.
467 G1RegionMarkStats* _region_mark_stats;
468 // Top pointer for each region at the start of the rebuild remembered set process
469 // for regions which remembered sets need to be rebuilt. A NULL for a given region
470 // means that this region does not be scanned during the rebuilding remembered
471 // set phase at all.
472 HeapWord* volatile* _top_at_rebuild_starts;
473 public:
474 void add_to_liveness(uint worker_id, oop const obj, size_t size);
475 // Liveness of the given region as determined by concurrent marking, i.e. the amount of
476 // live words between bottom and nTAMS.
477 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; }
478
479 // Sets the internal top_at_region_start for the given region to current top of the region.
480 inline void update_top_at_rebuild_start(HeapRegion* r);
481 // TARS for the given region during remembered set rebuilding.
482 inline HeapWord* top_at_rebuild_start(uint region) const;
483
484 // Clear statistics gathered during the concurrent cycle for the given region after
485 // it has been reclaimed.
486 void clear_statistics_in_region(uint region_idx);
487 // Notification for eagerly reclaimed regions to clean up.
488 void humongous_object_eagerly_reclaimed(HeapRegion* r);
489 // Manipulation of the global mark stack.
490 // The push and pop operations are used by tasks for transfers
491 // between task-local queues and the global mark stack.
492 bool mark_stack_push(G1TaskQueueEntry* arr) {
493 if (!_global_mark_stack.par_push_chunk(arr)) {
494 set_has_overflown();
495 return false;
496 }
497 return true;
498 }
499 bool mark_stack_pop(G1TaskQueueEntry* arr) {
500 return _global_mark_stack.par_pop_chunk(arr);
501 }
502 size_t mark_stack_size() const { return _global_mark_stack.size(); }
503 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; }
504 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); }
505
506 G1CMRootMemRegions* root_regions() { return &_root_regions; }
507
508 void concurrent_cycle_start();
509 // Abandon current marking iteration due to a Full GC.
510 void concurrent_cycle_abort();
511 void concurrent_cycle_end();
512
513 void update_accum_task_vtime(int i, double vtime) {
514 _accum_task_vtime[i] += vtime;
515 }
516
517 double all_task_accum_vtime() {
518 double ret = 0.0;
519 for (uint i = 0; i < _max_num_tasks; ++i)
520 ret += _accum_task_vtime[i];
521 return ret;
522 }
523
524 // Attempts to steal an object from the task queues of other tasks
525 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry);
526
527 G1ConcurrentMark(G1CollectedHeap* g1h,
528 G1RegionToSpaceMapper* prev_bitmap_storage,
529 G1RegionToSpaceMapper* next_bitmap_storage);
530 ~G1ConcurrentMark();
531
532 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; }
533
534 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; }
535 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; }
536
537 // Calculates the number of concurrent GC threads to be used in the marking phase.
538 uint calc_active_marking_workers();
539
540 // Moves all per-task cached data into global state.
541 void flush_all_task_caches();
542 // Prepare internal data structures for the next mark cycle. This includes clearing
543 // the next mark bitmap and some internal data structures. This method is intended
544 // to be called concurrently to the mutator. It will yield to safepoint requests.
545 void cleanup_for_next_mark();
546
547 // Clear the previous marking bitmap during safepoint.
548 void clear_prev_bitmap(WorkGang* workers);
549
550 // These two methods do the work that needs to be done at the start and end of the
551 // initial mark pause.
552 void pre_initial_mark();
553 void post_initial_mark();
554
555 // Scan all the root regions and mark everything reachable from
556 // them.
557 void scan_root_regions();
558
559 // Scan a single root MemRegion which holds from nTAMS to top and mark everything reachable from it.
560 void scan_root_region(MemRegion* region, uint worker_id);
561
562 // Do concurrent phase of marking, to a tentative transitive closure.
563 void mark_from_roots();
564
565 // Do concurrent preclean work.
566 void preclean();
567
568 void remark();
569
570 void cleanup();
571 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use
572 // this carefully.
573 inline void mark_in_prev_bitmap(oop p);
574
575 // Clears marks for all objects in the given range, for the prev or
576 // next bitmaps. Caution: the previous bitmap is usually
577 // read-only, so use this carefully!
578 void clear_range_in_prev_bitmap(MemRegion mr);
579
580 inline bool is_marked_in_prev_bitmap(oop p) const;
581
582 // Verify that there are no collection set oops on the stacks (taskqueues /
583 // global mark stack) and fingers (global / per-task).
584 // If marking is not in progress, it's a no-op.
585 void verify_no_collection_set_oops() PRODUCT_RETURN;
586
587 inline bool do_yield_check();
588
589 bool has_aborted() { return _has_aborted; }
590
591 void print_summary_info();
592
593 void print_worker_threads_on(outputStream* st) const;
594 void threads_do(ThreadClosure* tc) const;
595
596 void print_on_error(outputStream* st) const;
597
598 // Mark the given object on the next bitmap if it is below nTAMS.
599 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj);
600 inline bool mark_in_next_bitmap(uint worker_id, oop const obj);
601
602 inline bool is_marked_in_next_bitmap(oop p) const;
603
604 // Returns true if initialization was successfully completed.
605 bool completed_initialization() const {
606 return _completed_initialization;
607 }
608
609 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
610 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
611
612 private:
613 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application.
614 void rebuild_rem_set_concurrently();
615 };
616
617 // A class representing a marking task.
618 class G1CMTask : public TerminatorTerminator {
619 private:
620 enum PrivateConstants {
621 // The regular clock call is called once the scanned words reaches
622 // this limit
623 words_scanned_period = 12*1024,
624 // The regular clock call is called once the number of visited
625 // references reaches this limit
626 refs_reached_period = 1024,
627 // Initial value for the hash seed, used in the work stealing code
628 init_hash_seed = 17
629 };
630
631 // Number of entries in the per-task stats entry. This seems enough to have a very
632 // low cache miss rate.
633 static const uint RegionMarkStatsCacheSize = 1024;
634
635 G1CMObjArrayProcessor _objArray_processor;
636
637 uint _worker_id;
638 G1CollectedHeap* _g1h;
639 G1ConcurrentMark* _cm;
640 G1CMBitMap* _next_mark_bitmap;
641 // the task queue of this task
642 G1CMTaskQueue* _task_queue;
643
644 G1RegionMarkStatsCache _mark_stats_cache;
645 // Number of calls to this task
646 uint _calls;
647
648 // When the virtual timer reaches this time, the marking step should exit
649 double _time_target_ms;
650 // Start time of the current marking step
651 double _start_time_ms;
652
653 // Oop closure used for iterations over oops
654 G1CMOopClosure* _cm_oop_closure;
655
656 // Region this task is scanning, NULL if we're not scanning any
657 HeapRegion* _curr_region;
658 // Local finger of this task, NULL if we're not scanning a region
659 HeapWord* _finger;
660 // Limit of the region this task is scanning, NULL if we're not scanning one
661 HeapWord* _region_limit;
662
663 // Number of words this task has scanned
664 size_t _words_scanned;
665 // When _words_scanned reaches this limit, the regular clock is
666 // called. Notice that this might be decreased under certain
667 // circumstances (i.e. when we believe that we did an expensive
668 // operation).
669 size_t _words_scanned_limit;
670 // Initial value of _words_scanned_limit (i.e. what it was
671 // before it was decreased).
672 size_t _real_words_scanned_limit;
673
674 // Number of references this task has visited
675 size_t _refs_reached;
676 // When _refs_reached reaches this limit, the regular clock is
677 // called. Notice this this might be decreased under certain
678 // circumstances (i.e. when we believe that we did an expensive
679 // operation).
680 size_t _refs_reached_limit;
681 // Initial value of _refs_reached_limit (i.e. what it was before
682 // it was decreased).
683 size_t _real_refs_reached_limit;
684
685 // If true, then the task has aborted for some reason
686 bool _has_aborted;
687 // Set when the task aborts because it has met its time quota
688 bool _has_timed_out;
689 // True when we're draining SATB buffers; this avoids the task
690 // aborting due to SATB buffers being available (as we're already
691 // dealing with them)
692 bool _draining_satb_buffers;
693
694 // Number sequence of past step times
695 NumberSeq _step_times_ms;
696 // Elapsed time of this task
697 double _elapsed_time_ms;
698 // Termination time of this task
699 double _termination_time_ms;
700 // When this task got into the termination protocol
701 double _termination_start_time_ms;
702
703 TruncatedSeq _marking_step_diffs_ms;
704
705 // Updates the local fields after this task has claimed
706 // a new region to scan
707 void setup_for_region(HeapRegion* hr);
708 // Makes the limit of the region up-to-date
709 void update_region_limit();
710
711 // Called when either the words scanned or the refs visited limit
712 // has been reached
713 void reached_limit();
714 // Recalculates the words scanned and refs visited limits
715 void recalculate_limits();
716 // Decreases the words scanned and refs visited limits when we reach
717 // an expensive operation
718 void decrease_limits();
719 // Checks whether the words scanned or refs visited reached their
720 // respective limit and calls reached_limit() if they have
721 void check_limits() {
722 if (_words_scanned >= _words_scanned_limit ||
723 _refs_reached >= _refs_reached_limit) {
724 reached_limit();
725 }
726 }
727 // Supposed to be called regularly during a marking step as
728 // it checks a bunch of conditions that might cause the marking step
729 // to abort
730 // Return true if the marking step should continue. Otherwise, return false to abort
731 bool regular_clock_call();
732
733 // Set abort flag if regular_clock_call() check fails
734 inline void abort_marking_if_regular_check_fail();
735
736 // Test whether obj might have already been passed over by the
737 // mark bitmap scan, and so needs to be pushed onto the mark stack.
738 bool is_below_finger(oop obj, HeapWord* global_finger) const;
739
740 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
741 public:
742 // Apply the closure on the given area of the objArray. Return the number of words
743 // scanned.
744 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
745 // Resets the task; should be called right at the beginning of a marking phase.
746 void reset(G1CMBitMap* next_mark_bitmap);
747 // Clears all the fields that correspond to a claimed region.
748 void clear_region_fields();
749
750 // The main method of this class which performs a marking step
751 // trying not to exceed the given duration. However, it might exit
752 // prematurely, according to some conditions (i.e. SATB buffers are
753 // available for processing).
754 void do_marking_step(double target_ms,
755 bool do_termination,
756 bool is_serial);
757
758 // These two calls start and stop the timer
759 void record_start_time() {
760 _elapsed_time_ms = os::elapsedTime() * 1000.0;
761 }
762 void record_end_time() {
763 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
764 }
765
766 // Returns the worker ID associated with this task.
767 uint worker_id() { return _worker_id; }
768
769 // From TerminatorTerminator. It determines whether this task should
770 // exit the termination protocol after it's entered it.
771 virtual bool should_exit_termination();
772
773 // Resets the local region fields after a task has finished scanning a
774 // region; or when they have become stale as a result of the region
775 // being evacuated.
776 void giveup_current_region();
777
778 HeapWord* finger() { return _finger; }
779
780 bool has_aborted() { return _has_aborted; }
781 void set_has_aborted() { _has_aborted = true; }
782 void clear_has_aborted() { _has_aborted = false; }
783
784 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
785
786 // Increment the number of references this task has visited.
787 void increment_refs_reached() { ++_refs_reached; }
788
789 // Grey the object by marking it. If not already marked, push it on
790 // the local queue if below the finger. obj is required to be below its region's NTAMS.
791 // Returns whether there has been a mark to the bitmap.
792 inline bool make_reference_grey(oop obj);
793
794 // Grey the object (by calling make_grey_reference) if required,
795 // e.g. obj is below its containing region's NTAMS.
796 // Precondition: obj is a valid heap object.
797 // Returns true if the reference caused a mark to be set in the next bitmap.
798 template <class T>
799 inline bool deal_with_reference(T* p);
800
801 // Scans an object and visits its children.
802 inline void scan_task_entry(G1TaskQueueEntry task_entry);
803
804 // Pushes an object on the local queue.
805 inline void push(G1TaskQueueEntry task_entry);
806
807 // Move entries to the global stack.
808 void move_entries_to_global_stack();
809 // Move entries from the global stack, return true if we were successful to do so.
810 bool get_entries_from_global_stack();
811
812 // Pops and scans objects from the local queue. If partially is
813 // true, then it stops when the queue size is of a given limit. If
814 // partially is false, then it stops when the queue is empty.
815 void drain_local_queue(bool partially);
816 // Moves entries from the global stack to the local queue and
817 // drains the local queue. If partially is true, then it stops when
818 // both the global stack and the local queue reach a given size. If
819 // partially if false, it tries to empty them totally.
820 void drain_global_stack(bool partially);
821 // Keeps picking SATB buffers and processing them until no SATB
822 // buffers are available.
823 void drain_satb_buffers();
824
825 // Moves the local finger to a new location
826 inline void move_finger_to(HeapWord* new_finger) {
827 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
828 _finger = new_finger;
829 }
830
831 G1CMTask(uint worker_id,
832 G1ConcurrentMark *cm,
833 G1CMTaskQueue* task_queue,
834 G1RegionMarkStats* mark_stats,
835 uint max_regions);
836
837 inline void update_liveness(oop const obj, size_t const obj_size);
838
839 // Clear (without flushing) the mark cache entry for the given region.
840 void clear_mark_stats_cache(uint region_idx);
841 // Evict the whole statistics cache into the global statistics. Returns the
842 // number of cache hits and misses so far.
843 Pair<size_t, size_t> flush_mark_stats_cache();
844 // Prints statistics associated with this task
845 void print_stats();
846 };
847
848 // Class that's used to to print out per-region liveness
849 // information. It's currently used at the end of marking and also
850 // after we sort the old regions at the end of the cleanup operation.
851 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure {
852 // Accumulators for these values.
853 size_t _total_used_bytes;
854 size_t _total_capacity_bytes;
855 size_t _total_prev_live_bytes;
856 size_t _total_next_live_bytes;
857
858 // Accumulator for the remembered set size
859 size_t _total_remset_bytes;
860
861 // Accumulator for strong code roots memory size
862 size_t _total_strong_code_roots_bytes;
863
864 static double bytes_to_mb(size_t val) {
865 return (double) val / (double) M;
866 }
867
868 public:
869 // The header and footer are printed in the constructor and
870 // destructor respectively.
871 G1PrintRegionLivenessInfoClosure(const char* phase_name);
872 virtual bool do_heap_region(HeapRegion* r);
873 ~G1PrintRegionLivenessInfoClosure();
874 };
875
876 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP