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_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/taskTerminator.hpp"
34 #include "gc/shared/taskqueue.hpp"
35 #include "gc/shared/verifyOption.hpp"
36 #include "gc/shared/workgroup.hpp"
37 #include "memory/allocation.hpp"
38 #include "utilities/compilerWarnings.hpp"
39
40 class ConcurrentGCTimer;
41 class G1ConcurrentMarkThread;
42 class G1CollectedHeap;
43 class G1CMOopClosure;
44 class G1CMTask;
45 class G1ConcurrentMark;
46 class G1OldTracer;
47 class G1RegionToSpaceMapper;
48 class G1SurvivorRegions;
49 class ThreadClosure;
50
51 PRAGMA_DIAG_PUSH
52 // warning C4522: multiple assignment operators specified
53 PRAGMA_DISABLE_MSVC_WARNING(4522)
54
55 // This is a container class for either an oop or a continuation address for
56 // mark stack entries. Both are pushed onto the mark stack.
57 class G1TaskQueueEntry {
58 private:
59 void* _holder;
60
61 static const uintptr_t ArraySliceBit = 1;
62
63 G1TaskQueueEntry(oop obj) : _holder(obj) {
64 assert(_holder != NULL, "Not allowed to set NULL task queue element");
65 }
66 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { }
67 public:
68 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; }
69 G1TaskQueueEntry() : _holder(NULL) { }
70
71 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); }
72 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); }
73
74 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) {
75 _holder = t._holder;
76 return *this;
77 }
78
79 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile {
80 _holder = t._holder;
81 return *this;
82 }
83
84 oop obj() const {
85 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder));
86 return (oop)_holder;
87 }
88
89 HeapWord* slice() const {
90 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder));
91 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit);
92 }
93
94 bool is_oop() const { return !is_array_slice(); }
95 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; }
96 bool is_null() const { return _holder == NULL; }
97 };
98
99 PRAGMA_DIAG_POP
100
101 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue;
102 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
103
104 // Closure used by CM during concurrent reference discovery
105 // and reference processing (during remarking) to determine
106 // if a particular object is alive. It is primarily used
107 // to determine if referents of discovered reference objects
108 // are alive. An instance is also embedded into the
109 // reference processor as the _is_alive_non_header field
110 class G1CMIsAliveClosure : public BoolObjectClosure {
111 G1CollectedHeap* _g1h;
112 public:
113 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
114 bool do_object_b(oop obj);
115 };
116
117 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure {
118 G1CollectedHeap* _g1h;
119 public:
120 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
121 bool do_object_b(oop obj);
122 };
123
124 // Represents the overflow mark stack used by concurrent marking.
125 //
126 // Stores oops in a huge buffer in virtual memory that is always fully committed.
127 // Resizing may only happen during a STW pause when the stack is empty.
128 //
129 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
130 // stack memory is split into evenly sized chunks of oops. Users can only
131 // add or remove entries on that basis.
132 // Chunks are filled in increasing address order. Not completely filled chunks
133 // have a NULL element as a terminating element.
134 //
135 // Every chunk has a header containing a single pointer element used for memory
136 // management. This wastes some space, but is negligible (< .1% with current sizing).
137 //
138 // Memory management is done using a mix of tracking a high water-mark indicating
139 // that all chunks at a lower address are valid chunks, and a singly linked free
140 // list connecting all empty chunks.
141 class G1CMMarkStack {
142 public:
143 // Number of TaskQueueEntries that can fit in a single chunk.
144 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */;
145 private:
146 struct TaskQueueEntryChunk {
147 TaskQueueEntryChunk* next;
148 G1TaskQueueEntry data[EntriesPerChunk];
149 };
150
151 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack.
152
153 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area.
154 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements.
155
156 char _pad0[DEFAULT_CACHE_LINE_SIZE];
157 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
158 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)];
159 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data.
160 volatile size_t _chunks_in_chunk_list;
161 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)];
162
163 volatile size_t _hwm; // High water mark within the reserved space.
164 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
165
166 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
167 // NULL if out of memory.
168 TaskQueueEntryChunk* allocate_new_chunk();
169
170 // Atomically add the given chunk to the list.
171 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem);
172 // Atomically remove and return a chunk from the given list. Returns NULL if the
173 // list is empty.
174 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list);
175
176 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem);
177 void add_chunk_to_free_list(TaskQueueEntryChunk* elem);
178
179 TaskQueueEntryChunk* remove_chunk_from_chunk_list();
180 TaskQueueEntryChunk* remove_chunk_from_free_list();
181
182 // Resizes the mark stack to the given new capacity. Releases any previous
183 // memory if successful.
184 bool resize(size_t new_capacity);
185
186 public:
187 G1CMMarkStack();
188 ~G1CMMarkStack();
189
190 // Alignment and minimum capacity of this mark stack in number of oops.
191 static size_t capacity_alignment();
192
193 // Allocate and initialize the mark stack with the given number of oops.
194 bool initialize(size_t initial_capacity, size_t max_capacity);
195
196 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark
197 // stack. If less than EntriesPerChunk elements are to be pushed, the array must
198 // be terminated with a NULL.
199 // Returns whether the buffer contents were successfully pushed to the global mark
200 // stack.
201 bool par_push_chunk(G1TaskQueueEntry* buffer);
202
203 // Pops a chunk from this mark stack, copying them into the given buffer. This
204 // chunk may contain up to EntriesPerChunk elements. If there are less, the last
205 // element in the array is a NULL pointer.
206 bool par_pop_chunk(G1TaskQueueEntry* buffer);
207
208 // Return whether the chunk list is empty. Racy due to unsynchronized access to
209 // _chunk_list.
210 bool is_empty() const { return _chunk_list == NULL; }
211
212 size_t capacity() const { return _chunk_capacity; }
213
214 // Expand the stack, typically in response to an overflow condition
215 void expand();
216
217 // Return the approximate number of oops on this mark stack. Racy due to
218 // unsynchronized access to _chunks_in_chunk_list.
219 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; }
220
221 void set_empty();
222
223 // Apply Fn to every oop on the mark stack. The mark stack must not
224 // be modified while iterating.
225 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
226 };
227
228 // Root MemRegions are memory areas that contain objects which references are
229 // roots wrt to the marking. They must be scanned before marking to maintain the
230 // SATB invariant.
231 // Typically they contain the areas from nTAMS to top of the regions.
232 // We could scan and mark through these objects during the initial-mark pause, but for
233 // pause time reasons we move this work to the concurrent phase.
234 // We need to complete this procedure before the next GC because it might determine
235 // that some of these "root objects" are dead, potentially dropping some required
236 // references.
237 // Root MemRegions comprise of the contents of survivor regions at the end
238 // of the GC, and any objects copied into the old gen during GC.
239 class G1CMRootMemRegions {
240 // The set of root MemRegions.
241 MemRegion* _root_regions;
242 size_t const _max_regions;
243
244 volatile size_t _num_root_regions; // Actual number of root regions.
245
246 volatile size_t _claimed_root_regions; // Number of root regions currently claimed.
247
248 volatile bool _scan_in_progress;
249 volatile bool _should_abort;
250
251 void notify_scan_done();
252
253 public:
254 G1CMRootMemRegions(uint const max_regions);
255 ~G1CMRootMemRegions();
256
257 // Reset the data structure to allow addition of new root regions.
258 void reset();
259
260 void add(HeapWord* start, HeapWord* end);
261
262 // Reset the claiming / scanning of the root regions.
263 void prepare_for_scan();
264
265 // Forces get_next() to return NULL so that the iteration aborts early.
266 void abort() { _should_abort = true; }
267
268 // Return true if the CM thread are actively scanning root regions,
269 // false otherwise.
270 bool scan_in_progress() { return _scan_in_progress; }
271
272 // Claim the next root MemRegion to scan atomically, or return NULL if
273 // all have been claimed.
274 const MemRegion* claim_next();
275
276 // The number of root regions to scan.
277 uint num_root_regions() const;
278
279 void cancel_scan();
280
281 // Flag that we're done with root region scanning and notify anyone
282 // who's waiting on it. If aborted is false, assume that all regions
283 // have been claimed.
284 void scan_finished();
285
286 // If CM threads are still scanning root regions, wait until they
287 // are done. Return true if we had to wait, false otherwise.
288 bool wait_until_scan_finished();
289 };
290
291 // This class manages data structures and methods for doing liveness analysis in
292 // G1's concurrent cycle.
293 class G1ConcurrentMark : public CHeapObj<mtGC> {
294 friend class G1ConcurrentMarkThread;
295 friend class G1CMRefProcTaskProxy;
296 friend class G1CMRefProcTaskExecutor;
297 friend class G1CMKeepAliveAndDrainClosure;
298 friend class G1CMDrainMarkingStackClosure;
299 friend class G1CMBitMapClosure;
300 friend class G1CMConcurrentMarkingTask;
301 friend class G1CMRemarkTask;
302 friend class G1CMTask;
303
304 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work
305 G1CollectedHeap* _g1h; // The heap
306 bool _completed_initialization; // Set to true when initialization is complete
307
308 // Concurrent marking support structures
309 G1CMBitMap _mark_bitmap_1;
310 G1CMBitMap _mark_bitmap_2;
311 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap
312 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap
313
314 // Heap bounds
315 MemRegion const _heap;
316
317 // Root region tracking and claiming
318 G1CMRootMemRegions _root_regions;
319
320 // For grey objects
321 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
322 HeapWord* volatile _finger; // The global finger, region aligned,
323 // always pointing to the end of the
324 // last claimed region
325
326 uint _worker_id_offset;
327 uint _max_num_tasks; // Maximum number of marking tasks
328 uint _num_active_tasks; // Number of tasks currently active
329 G1CMTask** _tasks; // Task queue array (max_worker_id length)
330
331 G1CMTaskQueueSet* _task_queues; // Task queue set
332 TaskTerminator _terminator; // For termination
333
334 // Two sync barriers that are used to synchronize tasks when an
335 // overflow occurs. The algorithm is the following. All tasks enter
336 // the first one to ensure that they have all stopped manipulating
337 // the global data structures. After they exit it, they re-initialize
338 // their data structures and task 0 re-initializes the global data
339 // structures. Then, they enter the second sync barrier. This
340 // ensure, that no task starts doing work before all data
341 // structures (local and global) have been re-initialized. When they
342 // exit it, they are free to start working again.
343 WorkGangBarrierSync _first_overflow_barrier_sync;
344 WorkGangBarrierSync _second_overflow_barrier_sync;
345
346 // This is set by any task, when an overflow on the global data
347 // structures is detected
348 volatile bool _has_overflown;
349 // True: marking is concurrent, false: we're in remark
350 volatile bool _concurrent;
351 // Set at the end of a Full GC so that marking aborts
352 volatile bool _has_aborted;
353
354 // Used when remark aborts due to an overflow to indicate that
355 // another concurrent marking phase should start
356 volatile bool _restart_for_overflow;
357
358 ConcurrentGCTimer* _gc_timer_cm;
359
360 G1OldTracer* _gc_tracer_cm;
361
362 // Timing statistics. All of them are in ms
363 NumberSeq _init_times;
364 NumberSeq _remark_times;
365 NumberSeq _remark_mark_times;
366 NumberSeq _remark_weak_ref_times;
367 NumberSeq _cleanup_times;
368 double _total_cleanup_time;
369
370 double* _accum_task_vtime; // Accumulated task vtime
371
372 WorkGang* _concurrent_workers;
373 uint _num_concurrent_workers; // The number of marking worker threads we're using
374 uint _max_concurrent_workers; // Maximum number of marking worker threads
375
376 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller);
377
378 void finalize_marking();
379
380 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes);
381 void weak_refs_work(bool clear_all_soft_refs);
382
383 void report_object_count(bool mark_completed);
384
385 void swap_mark_bitmaps();
386
387 void reclaim_empty_regions();
388
389 // After reclaiming empty regions, update heap sizes.
390 void compute_new_sizes();
391
392 // Clear statistics gathered during the concurrent cycle for the given region after
393 // it has been reclaimed.
394 void clear_statistics(HeapRegion* r);
395
396 // 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_for_restart();
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 reset_at_marking_complete();
407
408 // Called to indicate how many threads are currently active.
409 void set_concurrency(uint active_tasks);
410
411 // 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 HeapWord* finger() { return _finger; }
419 bool concurrent() { return _concurrent; }
420 uint active_tasks() { return _num_active_tasks; }
421 TaskTerminator* terminator() { return &_terminator; }
422
423 // Claims the next available region to be scanned by a marking
424 // task/thread. It might return NULL if the next region is empty or
425 // we have run out of regions. In the latter case, out_of_regions()
426 // determines whether we've really run out of regions or the task
427 // should call claim_region() again. This might seem a bit
428 // awkward. Originally, the code was written so that claim_region()
429 // either successfully returned with a non-empty region or there
430 // were no more regions to be claimed. The problem with this was
431 // that, in certain circumstances, it iterated over large chunks of
432 // the heap finding only empty regions and, while it was working, it
433 // was preventing the calling task to call its regular clock
434 // method. So, this way, each task will spend very little time in
435 // claim_region() and is allowed to call the regular clock method
436 // frequently.
437 HeapRegion* claim_region(uint worker_id);
438
439 // Determines whether we've run out of regions to scan. Note that
440 // the finger can point past the heap end in case the heap was expanded
441 // to satisfy an allocation without doing a GC. This is fine, because all
442 // objects in those regions will be considered live anyway because of
443 // SATB guarantees (i.e. their TAMS will be equal to bottom).
444 bool out_of_regions() { return _finger >= _heap.end(); }
445
446 // Returns the task with the given id
447 G1CMTask* task(uint id) {
448 // During initial mark we use the parallel gc threads to do some work, so
449 // we can only compare against _max_num_tasks.
450 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks);
451 return _tasks[id];
452 }
453
454 // Access / manipulation of the overflow flag which is set to
455 // indicate that the global stack has overflown
456 bool has_overflown() { return _has_overflown; }
457 void set_has_overflown() { _has_overflown = true; }
458 void clear_has_overflown() { _has_overflown = false; }
459 bool restart_for_overflow() { return _restart_for_overflow; }
460
461 // Methods to enter the two overflow sync barriers
462 void enter_first_sync_barrier(uint worker_id);
463 void enter_second_sync_barrier(uint worker_id);
464
465 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
466 // true, periodically insert checks to see if this method should exit prematurely.
467 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
468
469 // Region statistics gathered during marking.
470 G1RegionMarkStats* _region_mark_stats;
471 // Top pointer for each region at the start of the rebuild remembered set process
472 // for regions which remembered sets need to be rebuilt. A NULL for a given region
473 // means that this region does not be scanned during the rebuilding remembered
474 // set phase at all.
475 HeapWord* volatile* _top_at_rebuild_starts;
476 public:
477 void add_to_liveness(uint worker_id, oop const obj, size_t size);
478 // Liveness of the given region as determined by concurrent marking, i.e. the amount of
479 // live words between bottom and nTAMS.
480 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; }
481
482 // Sets the internal top_at_region_start for the given region to current top of the region.
483 inline void update_top_at_rebuild_start(HeapRegion* r);
484 // TARS for the given region during remembered set rebuilding.
485 inline HeapWord* top_at_rebuild_start(uint region) const;
486
487 // Clear statistics gathered during the concurrent cycle for the given region after
488 // it has been reclaimed.
489 void clear_statistics_in_region(uint region_idx);
490 // Notification for eagerly reclaimed regions to clean up.
491 void humongous_object_eagerly_reclaimed(HeapRegion* r);
492 // Manipulation of the global mark stack.
493 // The push and pop operations are used by tasks for transfers
494 // between task-local queues and the global mark stack.
495 bool mark_stack_push(G1TaskQueueEntry* arr) {
496 if (!_global_mark_stack.par_push_chunk(arr)) {
497 set_has_overflown();
498 return false;
499 }
500 return true;
501 }
502 bool mark_stack_pop(G1TaskQueueEntry* arr) {
503 return _global_mark_stack.par_pop_chunk(arr);
504 }
505 size_t mark_stack_size() const { return _global_mark_stack.size(); }
506 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; }
507 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); }
508
509 G1CMRootMemRegions* root_regions() { return &_root_regions; }
510
511 void concurrent_cycle_start();
512 // Abandon current marking iteration due to a Full GC.
513 void concurrent_cycle_abort();
514 void concurrent_cycle_end();
515
516 void update_accum_task_vtime(int i, double vtime) {
517 _accum_task_vtime[i] += vtime;
518 }
519
520 double all_task_accum_vtime() {
521 double ret = 0.0;
522 for (uint i = 0; i < _max_num_tasks; ++i)
523 ret += _accum_task_vtime[i];
524 return ret;
525 }
526
527 // Attempts to steal an object from the task queues of other tasks
528 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry);
529
530 G1ConcurrentMark(G1CollectedHeap* g1h,
531 G1RegionToSpaceMapper* prev_bitmap_storage,
532 G1RegionToSpaceMapper* next_bitmap_storage);
533 ~G1ConcurrentMark();
534
535 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; }
536
537 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; }
538 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; }
539
540 // Calculates the number of concurrent GC threads to be used in the marking phase.
541 uint calc_active_marking_workers();
542
543 // Moves all per-task cached data into global state.
544 void flush_all_task_caches();
545 // Prepare internal data structures for the next mark cycle. This includes clearing
546 // the next mark bitmap and some internal data structures. This method is intended
547 // to be called concurrently to the mutator. It will yield to safepoint requests.
548 void cleanup_for_next_mark();
549
550 // Clear the previous marking bitmap during safepoint.
551 void clear_prev_bitmap(WorkGang* workers);
552
553 // These two methods do the work that needs to be done at the start and end of the
554 // initial mark pause.
555 void pre_initial_mark();
556 void post_initial_mark();
557
558 // Scan all the root regions and mark everything reachable from
559 // them.
560 void scan_root_regions();
561
562 // Scan a single root MemRegion to mark everything reachable from it.
563 void scan_root_region(const MemRegion* region, uint worker_id);
564
565 // Do concurrent phase of marking, to a tentative transitive closure.
566 void mark_from_roots();
567
568 // Do concurrent preclean work.
569 void preclean();
570
571 void remark();
572
573 void cleanup();
574 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use
575 // this carefully.
576 inline void mark_in_prev_bitmap(oop p);
577
578 // Clears marks for all objects in the given range, for the prev or
579 // next bitmaps. Caution: the previous bitmap is usually
580 // read-only, so use this carefully!
581 void clear_range_in_prev_bitmap(MemRegion mr);
582
583 inline bool is_marked_in_prev_bitmap(oop p) const;
584
585 // Verify that there are no collection set oops on the stacks (taskqueues /
586 // global mark stack) and fingers (global / per-task).
587 // If marking is not in progress, it's a no-op.
588 void verify_no_collection_set_oops() PRODUCT_RETURN;
589
590 inline bool do_yield_check();
591
592 bool has_aborted() { return _has_aborted; }
593
594 void print_summary_info();
595
596 void print_worker_threads_on(outputStream* st) const;
597 void threads_do(ThreadClosure* tc) const;
598
599 void print_on_error(outputStream* st) const;
600
601 // Mark the given object on the next bitmap if it is below nTAMS.
602 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj);
603 inline bool mark_in_next_bitmap(uint worker_id, oop const obj);
604
605 inline bool is_marked_in_next_bitmap(oop p) const;
606
607 // Returns true if initialization was successfully completed.
608 bool completed_initialization() const {
609 return _completed_initialization;
610 }
611
612 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
613 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
614
615 private:
616 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application.
617 void rebuild_rem_set_concurrently();
618 };
619
620 // A class representing a marking task.
621 class G1CMTask : public TerminatorTerminator {
622 private:
623 enum PrivateConstants {
624 // The regular clock call is called once the scanned words reaches
625 // this limit
626 words_scanned_period = 12*1024,
627 // The regular clock call is called once the number of visited
628 // references reaches this limit
629 refs_reached_period = 1024,
630 // Initial value for the hash seed, used in the work stealing code
631 init_hash_seed = 17
632 };
633
634 // Number of entries in the per-task stats entry. This seems enough to have a very
635 // low cache miss rate.
636 static const uint RegionMarkStatsCacheSize = 1024;
637
638 G1CMObjArrayProcessor _objArray_processor;
639
640 uint _worker_id;
641 G1CollectedHeap* _g1h;
642 G1ConcurrentMark* _cm;
643 G1CMBitMap* _next_mark_bitmap;
644 // the task queue of this task
645 G1CMTaskQueue* _task_queue;
646
647 G1RegionMarkStatsCache _mark_stats_cache;
648 // Number of calls to this task
649 uint _calls;
650
651 // When the virtual timer reaches this time, the marking step should exit
652 double _time_target_ms;
653 // Start time of the current marking step
654 double _start_time_ms;
655
656 // Oop closure used for iterations over oops
657 G1CMOopClosure* _cm_oop_closure;
658
659 // Region this task is scanning, NULL if we're not scanning any
660 HeapRegion* _curr_region;
661 // Local finger of this task, NULL if we're not scanning a region
662 HeapWord* _finger;
663 // Limit of the region this task is scanning, NULL if we're not scanning one
664 HeapWord* _region_limit;
665
666 // Number of words this task has scanned
667 size_t _words_scanned;
668 // When _words_scanned reaches this limit, the regular clock is
669 // called. Notice that this might be decreased under certain
670 // circumstances (i.e. when we believe that we did an expensive
671 // operation).
672 size_t _words_scanned_limit;
673 // Initial value of _words_scanned_limit (i.e. what it was
674 // before it was decreased).
675 size_t _real_words_scanned_limit;
676
677 // Number of references this task has visited
678 size_t _refs_reached;
679 // When _refs_reached reaches this limit, the regular clock is
680 // called. Notice this this might be decreased under certain
681 // circumstances (i.e. when we believe that we did an expensive
682 // operation).
683 size_t _refs_reached_limit;
684 // Initial value of _refs_reached_limit (i.e. what it was before
685 // it was decreased).
686 size_t _real_refs_reached_limit;
687
688 // If true, then the task has aborted for some reason
689 bool _has_aborted;
690 // Set when the task aborts because it has met its time quota
691 bool _has_timed_out;
692 // True when we're draining SATB buffers; this avoids the task
693 // aborting due to SATB buffers being available (as we're already
694 // dealing with them)
695 bool _draining_satb_buffers;
696
697 // Number sequence of past step times
698 NumberSeq _step_times_ms;
699 // Elapsed time of this task
700 double _elapsed_time_ms;
701 // Termination time of this task
702 double _termination_time_ms;
703 // When this task got into the termination protocol
704 double _termination_start_time_ms;
705
706 TruncatedSeq _marking_step_diff_ms;
707
708 // Updates the local fields after this task has claimed
709 // a new region to scan
710 void setup_for_region(HeapRegion* hr);
711 // Makes the limit of the region up-to-date
712 void update_region_limit();
713
714 // Called when either the words scanned or the refs visited limit
715 // has been reached
716 void reached_limit();
717 // Recalculates the words scanned and refs visited limits
718 void recalculate_limits();
719 // Decreases the words scanned and refs visited limits when we reach
720 // an expensive operation
721 void decrease_limits();
722 // Checks whether the words scanned or refs visited reached their
723 // respective limit and calls reached_limit() if they have
724 void check_limits() {
725 if (_words_scanned >= _words_scanned_limit ||
726 _refs_reached >= _refs_reached_limit) {
727 reached_limit();
728 }
729 }
730 // Supposed to be called regularly during a marking step as
731 // it checks a bunch of conditions that might cause the marking step
732 // to abort
733 // Return true if the marking step should continue. Otherwise, return false to abort
734 bool regular_clock_call();
735
736 // Set abort flag if regular_clock_call() check fails
737 inline void abort_marking_if_regular_check_fail();
738
739 // Test whether obj might have already been passed over by the
740 // mark bitmap scan, and so needs to be pushed onto the mark stack.
741 bool is_below_finger(oop obj, HeapWord* global_finger) const;
742
743 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
744 public:
745 // Apply the closure on the given area of the objArray. Return the number of words
746 // scanned.
747 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
748 // Resets the task; should be called right at the beginning of a marking phase.
749 void reset(G1CMBitMap* next_mark_bitmap);
750 // Clears all the fields that correspond to a claimed region.
751 void clear_region_fields();
752
753 // The main method of this class which performs a marking step
754 // trying not to exceed the given duration. However, it might exit
755 // prematurely, according to some conditions (i.e. SATB buffers are
756 // available for processing).
757 void do_marking_step(double target_ms,
758 bool do_termination,
759 bool is_serial);
760
761 // These two calls start and stop the timer
762 void record_start_time() {
763 _elapsed_time_ms = os::elapsedTime() * 1000.0;
764 }
765 void record_end_time() {
766 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
767 }
768
769 // Returns the worker ID associated with this task.
770 uint worker_id() { return _worker_id; }
771
772 // From TerminatorTerminator. It determines whether this task should
773 // exit the termination protocol after it's entered it.
774 virtual bool should_exit_termination();
775
776 // Resets the local region fields after a task has finished scanning a
777 // region; or when they have become stale as a result of the region
778 // being evacuated.
779 void giveup_current_region();
780
781 HeapWord* finger() { return _finger; }
782
783 bool has_aborted() { return _has_aborted; }
784 void set_has_aborted() { _has_aborted = true; }
785 void clear_has_aborted() { _has_aborted = false; }
786
787 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
788
789 // Increment the number of references this task has visited.
790 void increment_refs_reached() { ++_refs_reached; }
791
792 // Grey the object by marking it. If not already marked, push it on
793 // the local queue if below the finger. obj is required to be below its region's NTAMS.
794 // Returns whether there has been a mark to the bitmap.
795 inline bool make_reference_grey(oop obj);
796
797 // Grey the object (by calling make_grey_reference) if required,
798 // e.g. obj is below its containing region's NTAMS.
799 // Precondition: obj is a valid heap object.
800 // Returns true if the reference caused a mark to be set in the next bitmap.
801 template <class T>
802 inline bool deal_with_reference(T* p);
803
804 // Scans an object and visits its children.
805 inline void scan_task_entry(G1TaskQueueEntry task_entry);
806
807 // Pushes an object on the local queue.
808 inline void push(G1TaskQueueEntry task_entry);
809
810 // Move entries to the global stack.
811 void move_entries_to_global_stack();
812 // Move entries from the global stack, return true if we were successful to do so.
813 bool get_entries_from_global_stack();
814
815 // Pops and scans objects from the local queue. If partially is
816 // true, then it stops when the queue size is of a given limit. If
817 // partially is false, then it stops when the queue is empty.
818 void drain_local_queue(bool partially);
819 // Moves entries from the global stack to the local queue and
820 // drains the local queue. If partially is true, then it stops when
821 // both the global stack and the local queue reach a given size. If
822 // partially if false, it tries to empty them totally.
823 void drain_global_stack(bool partially);
824 // Keeps picking SATB buffers and processing them until no SATB
825 // buffers are available.
826 void drain_satb_buffers();
827
828 // Moves the local finger to a new location
829 inline void move_finger_to(HeapWord* new_finger) {
830 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
831 _finger = new_finger;
832 }
833
834 G1CMTask(uint worker_id,
835 G1ConcurrentMark *cm,
836 G1CMTaskQueue* task_queue,
837 G1RegionMarkStats* mark_stats,
838 uint max_regions);
839
840 inline void update_liveness(oop const obj, size_t const obj_size);
841
842 // Clear (without flushing) the mark cache entry for the given region.
843 void clear_mark_stats_cache(uint region_idx);
844 // Evict the whole statistics cache into the global statistics. Returns the
845 // number of cache hits and misses so far.
846 Pair<size_t, size_t> flush_mark_stats_cache();
847 // Prints statistics associated with this task
848 void print_stats();
849 };
850
851 // Class that's used to to print out per-region liveness
852 // information. It's currently used at the end of marking and also
853 // after we sort the old regions at the end of the cleanup operation.
854 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure {
855 // Accumulators for these values.
856 size_t _total_used_bytes;
857 size_t _total_capacity_bytes;
858 size_t _total_prev_live_bytes;
859 size_t _total_next_live_bytes;
860
861 // Accumulator for the remembered set size
862 size_t _total_remset_bytes;
863
864 // Accumulator for strong code roots memory size
865 size_t _total_strong_code_roots_bytes;
866
867 static double bytes_to_mb(size_t val) {
868 return (double) val / (double) M;
869 }
870
871 public:
872 // The header and footer are printed in the constructor and
873 // destructor respectively.
874 G1PrintRegionLivenessInfoClosure(const char* phase_name);
875 virtual bool do_heap_region(HeapRegion* r);
876 ~G1PrintRegionLivenessInfoClosure();
877 };
878
879 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP