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
307 // Concurrent marking support structures
308 G1CMBitMap _mark_bitmap_1;
309 G1CMBitMap _mark_bitmap_2;
310 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap
311 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap
312
313 // Heap bounds
314 MemRegion const _heap;
315
316 // Root region tracking and claiming
317 G1CMRootMemRegions _root_regions;
318
319 // For grey objects
320 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
321 HeapWord* volatile _finger; // The global finger, region aligned,
322 // always pointing to the end of the
323 // last claimed region
324
325 uint _worker_id_offset;
326 uint _max_num_tasks; // Maximum number of marking tasks
327 uint _num_active_tasks; // Number of tasks currently active
328 G1CMTask** _tasks; // Task queue array (max_worker_id length)
329
330 G1CMTaskQueueSet* _task_queues; // Task queue set
331 TaskTerminator _terminator; // For termination
332
333 // Two sync barriers that are used to synchronize tasks when an
334 // overflow occurs. The algorithm is the following. All tasks enter
335 // the first one to ensure that they have all stopped manipulating
336 // the global data structures. After they exit it, they re-initialize
337 // their data structures and task 0 re-initializes the global data
338 // structures. Then, they enter the second sync barrier. This
339 // ensure, that no task starts doing work before all data
340 // structures (local and global) have been re-initialized. When they
341 // exit it, they are free to start working again.
342 WorkGangBarrierSync _first_overflow_barrier_sync;
343 WorkGangBarrierSync _second_overflow_barrier_sync;
344
345 // This is set by any task, when an overflow on the global data
346 // structures is detected
347 volatile bool _has_overflown;
348 // True: marking is concurrent, false: we're in remark
349 volatile bool _concurrent;
350 // Set at the end of a Full GC so that marking aborts
351 volatile bool _has_aborted;
352
353 // Used when remark aborts due to an overflow to indicate that
354 // another concurrent marking phase should start
355 volatile bool _restart_for_overflow;
356
357 ConcurrentGCTimer* _gc_timer_cm;
358
359 G1OldTracer* _gc_tracer_cm;
360
361 // Timing statistics. All of them are in ms
362 NumberSeq _init_times;
363 NumberSeq _remark_times;
364 NumberSeq _remark_mark_times;
365 NumberSeq _remark_weak_ref_times;
366 NumberSeq _cleanup_times;
367 double _total_cleanup_time;
368
369 double* _accum_task_vtime; // Accumulated task vtime
370
371 WorkGang* _concurrent_workers;
372 uint _num_concurrent_workers; // The number of marking worker threads we're using
373 uint _max_concurrent_workers; // Maximum number of marking worker threads
374
375 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller);
376
377 void finalize_marking();
378
379 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes);
380 void weak_refs_work(bool clear_all_soft_refs);
381
382 void report_object_count(bool mark_completed);
383
384 void swap_mark_bitmaps();
385
386 void reclaim_empty_regions();
387
388 // After reclaiming empty regions, update heap sizes.
389 void compute_new_sizes();
390
391 // Clear statistics gathered during the concurrent cycle for the given region after
392 // it has been reclaimed.
393 void clear_statistics(HeapRegion* r);
394
395 // Resets the global marking data structures, as well as the
396 // task local ones; should be called during initial mark.
397 void reset();
398
399 // Resets all the marking data structures. Called when we have to restart
400 // marking or when marking completes (via set_non_marking_state below).
401 void reset_marking_for_restart();
402
403 // We do this after we're done with marking so that the marking data
404 // structures are initialized to a sensible and predictable state.
405 void reset_at_marking_complete();
406
407 // Called to indicate how many threads are currently active.
408 void set_concurrency(uint active_tasks);
409
410 // Should be called to indicate which phase we're in (concurrent
411 // mark or remark) and how many threads are currently active.
412 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
413
414 // Prints all gathered CM-related statistics
415 void print_stats();
416
417 HeapWord* finger() { return _finger; }
418 bool concurrent() { return _concurrent; }
419 uint active_tasks() { return _num_active_tasks; }
420 TaskTerminator* terminator() { return &_terminator; }
421
422 // Claims the next available region to be scanned by a marking
423 // task/thread. It might return NULL if the next region is empty or
424 // we have run out of regions. In the latter case, out_of_regions()
425 // determines whether we've really run out of regions or the task
426 // should call claim_region() again. This might seem a bit
427 // awkward. Originally, the code was written so that claim_region()
428 // either successfully returned with a non-empty region or there
429 // were no more regions to be claimed. The problem with this was
430 // that, in certain circumstances, it iterated over large chunks of
431 // the heap finding only empty regions and, while it was working, it
432 // was preventing the calling task to call its regular clock
433 // method. So, this way, each task will spend very little time in
434 // claim_region() and is allowed to call the regular clock method
435 // frequently.
436 HeapRegion* claim_region(uint worker_id);
437
438 // Determines whether we've run out of regions to scan. Note that
439 // the finger can point past the heap end in case the heap was expanded
440 // to satisfy an allocation without doing a GC. This is fine, because all
441 // objects in those regions will be considered live anyway because of
442 // SATB guarantees (i.e. their TAMS will be equal to bottom).
443 bool out_of_regions() { return _finger >= _heap.end(); }
444
445 // Returns the task with the given id
446 G1CMTask* task(uint id) {
447 // During initial mark we use the parallel gc threads to do some work, so
448 // we can only compare against _max_num_tasks.
449 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks);
450 return _tasks[id];
451 }
452
453 // Access / manipulation of the overflow flag which is set to
454 // indicate that the global stack has overflown
455 bool has_overflown() { return _has_overflown; }
456 void set_has_overflown() { _has_overflown = true; }
457 void clear_has_overflown() { _has_overflown = false; }
458 bool restart_for_overflow() { return _restart_for_overflow; }
459
460 // Methods to enter the two overflow sync barriers
461 void enter_first_sync_barrier(uint worker_id);
462 void enter_second_sync_barrier(uint worker_id);
463
464 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
465 // true, periodically insert checks to see if this method should exit prematurely.
466 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
467
468 // Region statistics gathered during marking.
469 G1RegionMarkStats* _region_mark_stats;
470 // Top pointer for each region at the start of the rebuild remembered set process
471 // for regions which remembered sets need to be rebuilt. A NULL for a given region
472 // means that this region does not be scanned during the rebuilding remembered
473 // set phase at all.
474 HeapWord* volatile* _top_at_rebuild_starts;
475 public:
476 void add_to_liveness(uint worker_id, oop const obj, size_t size);
477 // Liveness of the given region as determined by concurrent marking, i.e. the amount of
478 // live words between bottom and nTAMS.
479 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; }
480
481 // Sets the internal top_at_region_start for the given region to current top of the region.
482 inline void update_top_at_rebuild_start(HeapRegion* r);
483 // TARS for the given region during remembered set rebuilding.
484 inline HeapWord* top_at_rebuild_start(uint region) const;
485
486 // Clear statistics gathered during the concurrent cycle for the given region after
487 // it has been reclaimed.
488 void clear_statistics_in_region(uint region_idx);
489 // Notification for eagerly reclaimed regions to clean up.
490 void humongous_object_eagerly_reclaimed(HeapRegion* r);
491 // Manipulation of the global mark stack.
492 // The push and pop operations are used by tasks for transfers
493 // between task-local queues and the global mark stack.
494 bool mark_stack_push(G1TaskQueueEntry* arr) {
495 if (!_global_mark_stack.par_push_chunk(arr)) {
496 set_has_overflown();
497 return false;
498 }
499 return true;
500 }
501 bool mark_stack_pop(G1TaskQueueEntry* arr) {
502 return _global_mark_stack.par_pop_chunk(arr);
503 }
504 size_t mark_stack_size() const { return _global_mark_stack.size(); }
505 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; }
506 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); }
507
508 G1CMRootMemRegions* root_regions() { return &_root_regions; }
509
510 void concurrent_cycle_start();
511 // Abandon current marking iteration due to a Full GC.
512 void concurrent_cycle_abort();
513 void concurrent_cycle_end();
514
515 void update_accum_task_vtime(int i, double vtime) {
516 _accum_task_vtime[i] += vtime;
517 }
518
519 double all_task_accum_vtime() {
520 double ret = 0.0;
521 for (uint i = 0; i < _max_num_tasks; ++i)
522 ret += _accum_task_vtime[i];
523 return ret;
524 }
525
526 // Attempts to steal an object from the task queues of other tasks
527 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry);
528
529 G1ConcurrentMark(G1CollectedHeap* g1h,
530 G1RegionToSpaceMapper* prev_bitmap_storage,
531 G1RegionToSpaceMapper* next_bitmap_storage);
532 ~G1ConcurrentMark();
533
534 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; }
535
536 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; }
537 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; }
538
539 // Calculates the number of concurrent GC threads to be used in the marking phase.
540 uint calc_active_marking_workers();
541
542 // Moves all per-task cached data into global state.
543 void flush_all_task_caches();
544 // Prepare internal data structures for the next mark cycle. This includes clearing
545 // the next mark bitmap and some internal data structures. This method is intended
546 // to be called concurrently to the mutator. It will yield to safepoint requests.
547 void cleanup_for_next_mark();
548
549 // Clear the previous marking bitmap during safepoint.
550 void clear_prev_bitmap(WorkGang* workers);
551
552 // These two methods do the work that needs to be done at the start and end of the
553 // initial mark pause.
554 void pre_initial_mark();
555 void post_initial_mark();
556
557 // Scan all the root regions and mark everything reachable from
558 // them.
559 void scan_root_regions();
560
561 // Scan a single root MemRegion to mark everything reachable from it.
562 void scan_root_region(const MemRegion* region, uint worker_id);
563
564 // Do concurrent phase of marking, to a tentative transitive closure.
565 void mark_from_roots();
566
567 // Do concurrent preclean work.
568 void preclean();
569
570 void remark();
571
572 void cleanup();
573 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use
574 // this carefully.
575 inline void mark_in_prev_bitmap(oop p);
576
577 // Clears marks for all objects in the given range, for the prev or
578 // next bitmaps. Caution: the previous bitmap is usually
579 // read-only, so use this carefully!
580 void clear_range_in_prev_bitmap(MemRegion mr);
581
582 inline bool is_marked_in_prev_bitmap(oop p) const;
583
584 // Verify that there are no collection set oops on the stacks (taskqueues /
585 // global mark stack) and fingers (global / per-task).
586 // If marking is not in progress, it's a no-op.
587 void verify_no_collection_set_oops() PRODUCT_RETURN;
588
589 inline bool do_yield_check();
590
591 bool has_aborted() { return _has_aborted; }
592
593 void print_summary_info();
594
595 void print_worker_threads_on(outputStream* st) const;
596 void threads_do(ThreadClosure* tc) const;
597
598 void print_on_error(outputStream* st) const;
599
600 // Mark the given object on the next bitmap if it is below nTAMS.
601 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj);
602 inline bool mark_in_next_bitmap(uint worker_id, oop const obj);
603
604 inline bool is_marked_in_next_bitmap(oop p) const;
605
606 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
607 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
608
609 private:
610 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application.
611 void rebuild_rem_set_concurrently();
612 };
613
614 // A class representing a marking task.
615 class G1CMTask : public TerminatorTerminator {
616 private:
617 enum PrivateConstants {
618 // The regular clock call is called once the scanned words reaches
619 // this limit
620 words_scanned_period = 12*1024,
621 // The regular clock call is called once the number of visited
622 // references reaches this limit
623 refs_reached_period = 1024,
624 // Initial value for the hash seed, used in the work stealing code
625 init_hash_seed = 17
626 };
627
628 // Number of entries in the per-task stats entry. This seems enough to have a very
629 // low cache miss rate.
630 static const uint RegionMarkStatsCacheSize = 1024;
631
632 G1CMObjArrayProcessor _objArray_processor;
633
634 uint _worker_id;
635 G1CollectedHeap* _g1h;
636 G1ConcurrentMark* _cm;
637 G1CMBitMap* _next_mark_bitmap;
638 // the task queue of this task
639 G1CMTaskQueue* _task_queue;
640
641 G1RegionMarkStatsCache _mark_stats_cache;
642 // Number of calls to this task
643 uint _calls;
644
645 // When the virtual timer reaches this time, the marking step should exit
646 double _time_target_ms;
647 // Start time of the current marking step
648 double _start_time_ms;
649
650 // Oop closure used for iterations over oops
651 G1CMOopClosure* _cm_oop_closure;
652
653 // Region this task is scanning, NULL if we're not scanning any
654 HeapRegion* _curr_region;
655 // Local finger of this task, NULL if we're not scanning a region
656 HeapWord* _finger;
657 // Limit of the region this task is scanning, NULL if we're not scanning one
658 HeapWord* _region_limit;
659
660 // Number of words this task has scanned
661 size_t _words_scanned;
662 // When _words_scanned reaches this limit, the regular clock is
663 // called. Notice that this might be decreased under certain
664 // circumstances (i.e. when we believe that we did an expensive
665 // operation).
666 size_t _words_scanned_limit;
667 // Initial value of _words_scanned_limit (i.e. what it was
668 // before it was decreased).
669 size_t _real_words_scanned_limit;
670
671 // Number of references this task has visited
672 size_t _refs_reached;
673 // When _refs_reached reaches this limit, the regular clock is
674 // called. Notice this this might be decreased under certain
675 // circumstances (i.e. when we believe that we did an expensive
676 // operation).
677 size_t _refs_reached_limit;
678 // Initial value of _refs_reached_limit (i.e. what it was before
679 // it was decreased).
680 size_t _real_refs_reached_limit;
681
682 // If true, then the task has aborted for some reason
683 bool _has_aborted;
684 // Set when the task aborts because it has met its time quota
685 bool _has_timed_out;
686 // True when we're draining SATB buffers; this avoids the task
687 // aborting due to SATB buffers being available (as we're already
688 // dealing with them)
689 bool _draining_satb_buffers;
690
691 // Number sequence of past step times
692 NumberSeq _step_times_ms;
693 // Elapsed time of this task
694 double _elapsed_time_ms;
695 // Termination time of this task
696 double _termination_time_ms;
697 // When this task got into the termination protocol
698 double _termination_start_time_ms;
699
700 TruncatedSeq _marking_step_diff_ms;
701
702 // Updates the local fields after this task has claimed
703 // a new region to scan
704 void setup_for_region(HeapRegion* hr);
705 // Makes the limit of the region up-to-date
706 void update_region_limit();
707
708 // Called when either the words scanned or the refs visited limit
709 // has been reached
710 void reached_limit();
711 // Recalculates the words scanned and refs visited limits
712 void recalculate_limits();
713 // Decreases the words scanned and refs visited limits when we reach
714 // an expensive operation
715 void decrease_limits();
716 // Checks whether the words scanned or refs visited reached their
717 // respective limit and calls reached_limit() if they have
718 void check_limits() {
719 if (_words_scanned >= _words_scanned_limit ||
720 _refs_reached >= _refs_reached_limit) {
721 reached_limit();
722 }
723 }
724 // Supposed to be called regularly during a marking step as
725 // it checks a bunch of conditions that might cause the marking step
726 // to abort
727 // Return true if the marking step should continue. Otherwise, return false to abort
728 bool regular_clock_call();
729
730 // Set abort flag if regular_clock_call() check fails
731 inline void abort_marking_if_regular_check_fail();
732
733 // Test whether obj might have already been passed over by the
734 // mark bitmap scan, and so needs to be pushed onto the mark stack.
735 bool is_below_finger(oop obj, HeapWord* global_finger) const;
736
737 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
738 public:
739 // Apply the closure on the given area of the objArray. Return the number of words
740 // scanned.
741 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
742 // Resets the task; should be called right at the beginning of a marking phase.
743 void reset(G1CMBitMap* next_mark_bitmap);
744 // Clears all the fields that correspond to a claimed region.
745 void clear_region_fields();
746
747 // The main method of this class which performs a marking step
748 // trying not to exceed the given duration. However, it might exit
749 // prematurely, according to some conditions (i.e. SATB buffers are
750 // available for processing).
751 void do_marking_step(double target_ms,
752 bool do_termination,
753 bool is_serial);
754
755 // These two calls start and stop the timer
756 void record_start_time() {
757 _elapsed_time_ms = os::elapsedTime() * 1000.0;
758 }
759 void record_end_time() {
760 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
761 }
762
763 // Returns the worker ID associated with this task.
764 uint worker_id() { return _worker_id; }
765
766 // From TerminatorTerminator. It determines whether this task should
767 // exit the termination protocol after it's entered it.
768 virtual bool should_exit_termination();
769
770 // Resets the local region fields after a task has finished scanning a
771 // region; or when they have become stale as a result of the region
772 // being evacuated.
773 void giveup_current_region();
774
775 HeapWord* finger() { return _finger; }
776
777 bool has_aborted() { return _has_aborted; }
778 void set_has_aborted() { _has_aborted = true; }
779 void clear_has_aborted() { _has_aborted = false; }
780
781 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
782
783 // Increment the number of references this task has visited.
784 void increment_refs_reached() { ++_refs_reached; }
785
786 // Grey the object by marking it. If not already marked, push it on
787 // the local queue if below the finger. obj is required to be below its region's NTAMS.
788 // Returns whether there has been a mark to the bitmap.
789 inline bool make_reference_grey(oop obj);
790
791 // Grey the object (by calling make_grey_reference) if required,
792 // e.g. obj is below its containing region's NTAMS.
793 // Precondition: obj is a valid heap object.
794 // Returns true if the reference caused a mark to be set in the next bitmap.
795 template <class T>
796 inline bool deal_with_reference(T* p);
797
798 // Scans an object and visits its children.
799 inline void scan_task_entry(G1TaskQueueEntry task_entry);
800
801 // Pushes an object on the local queue.
802 inline void push(G1TaskQueueEntry task_entry);
803
804 // Move entries to the global stack.
805 void move_entries_to_global_stack();
806 // Move entries from the global stack, return true if we were successful to do so.
807 bool get_entries_from_global_stack();
808
809 // Pops and scans objects from the local queue. If partially is
810 // true, then it stops when the queue size is of a given limit. If
811 // partially is false, then it stops when the queue is empty.
812 void drain_local_queue(bool partially);
813 // Moves entries from the global stack to the local queue and
814 // drains the local queue. If partially is true, then it stops when
815 // both the global stack and the local queue reach a given size. If
816 // partially if false, it tries to empty them totally.
817 void drain_global_stack(bool partially);
818 // Keeps picking SATB buffers and processing them until no SATB
819 // buffers are available.
820 void drain_satb_buffers();
821
822 // Moves the local finger to a new location
823 inline void move_finger_to(HeapWord* new_finger) {
824 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
825 _finger = new_finger;
826 }
827
828 G1CMTask(uint worker_id,
829 G1ConcurrentMark *cm,
830 G1CMTaskQueue* task_queue,
831 G1RegionMarkStats* mark_stats,
832 uint max_regions);
833
834 inline void update_liveness(oop const obj, size_t const obj_size);
835
836 // Clear (without flushing) the mark cache entry for the given region.
837 void clear_mark_stats_cache(uint region_idx);
838 // Evict the whole statistics cache into the global statistics. Returns the
839 // number of cache hits and misses so far.
840 Pair<size_t, size_t> flush_mark_stats_cache();
841 // Prints statistics associated with this task
842 void print_stats();
843 };
844
845 // Class that's used to to print out per-region liveness
846 // information. It's currently used at the end of marking and also
847 // after we sort the old regions at the end of the cleanup operation.
848 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure {
849 // Accumulators for these values.
850 size_t _total_used_bytes;
851 size_t _total_capacity_bytes;
852 size_t _total_prev_live_bytes;
853 size_t _total_next_live_bytes;
854
855 // Accumulator for the remembered set size
856 size_t _total_remset_bytes;
857
858 // Accumulator for strong code roots memory size
859 size_t _total_strong_code_roots_bytes;
860
861 static double bytes_to_mb(size_t val) {
862 return (double) val / (double) M;
863 }
864
865 public:
866 // The header and footer are printed in the constructor and
867 // destructor respectively.
868 G1PrintRegionLivenessInfoClosure(const char* phase_name);
869 virtual bool do_heap_region(HeapRegion* r);
870 ~G1PrintRegionLivenessInfoClosure();
871 };
872
873 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP