1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
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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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
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24
25 #ifndef SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
27
28 #include "gc/g1/g1ConcurrentMarkBitMap.hpp"
29 #include "gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp"
30 #include "gc/g1/g1RegionMarkStatsCache.hpp"
31 #include "gc/g1/heapRegionSet.hpp"
32 #include "gc/shared/taskqueue.hpp"
33 #include "memory/allocation.hpp"
34
35 class ConcurrentGCTimer;
36 class ConcurrentMarkThread;
37 class G1CollectedHeap;
38 class G1CMTask;
39 class G1ConcurrentMark;
40 class G1OldTracer;
41 class G1RegionToSpaceMapper;
42 class G1SurvivorRegions;
43
44 #ifdef _MSC_VER
45 #pragma warning(push)
46 // warning C4522: multiple assignment operators specified
47 #pragma warning(disable:4522)
48 #endif
49
50 // This is a container class for either an oop or a continuation address for
51 // mark stack entries. Both are pushed onto the mark stack.
52 class G1TaskQueueEntry {
53 private:
54 void* _holder;
55
56 static const uintptr_t ArraySliceBit = 1;
57
58 G1TaskQueueEntry(oop obj) : _holder(obj) {
59 assert(_holder != NULL, "Not allowed to set NULL task queue element");
60 }
61 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { }
62 public:
63 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; }
64 G1TaskQueueEntry() : _holder(NULL) { }
65
66 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); }
67 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); }
68
69 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) {
70 _holder = t._holder;
71 return *this;
72 }
73
74 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile {
75 _holder = t._holder;
76 return *this;
77 }
78
79 oop obj() const {
80 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder));
81 return (oop)_holder;
82 }
83
84 HeapWord* slice() const {
85 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder));
86 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit);
87 }
88
89 bool is_oop() const { return !is_array_slice(); }
90 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; }
91 bool is_null() const { return _holder == NULL; }
92 };
93
94 #ifdef _MSC_VER
95 #pragma warning(pop)
96 #endif
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* g1) : _g1h(g1) { }
111
112 bool do_object_b(oop obj);
113 };
114
115 // Represents the overflow mark stack used by concurrent marking.
116 //
117 // Stores oops in a huge buffer in virtual memory that is always fully committed.
118 // Resizing may only happen during a STW pause when the stack is empty.
119 //
120 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
121 // stack memory is split into evenly sized chunks of oops. Users can only
122 // add or remove entries on that basis.
123 // Chunks are filled in increasing address order. Not completely filled chunks
124 // have a NULL element as a terminating element.
125 //
126 // Every chunk has a header containing a single pointer element used for memory
127 // management. This wastes some space, but is negligible (< .1% with current sizing).
128 //
129 // Memory management is done using a mix of tracking a high water-mark indicating
130 // that all chunks at a lower address are valid chunks, and a singly linked free
131 // list connecting all empty chunks.
132 class G1CMMarkStack {
133 public:
134 // Number of TaskQueueEntries that can fit in a single chunk.
135 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */;
136 private:
137 struct TaskQueueEntryChunk {
138 TaskQueueEntryChunk* next;
139 G1TaskQueueEntry data[EntriesPerChunk];
140 };
141
142 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack.
143
144 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area.
145 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements.
146
147 char _pad0[DEFAULT_CACHE_LINE_SIZE];
148 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
149 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)];
150 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data.
151 volatile size_t _chunks_in_chunk_list;
152 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)];
153
154 volatile size_t _hwm; // High water mark within the reserved space.
155 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
156
157 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
158 // NULL if out of memory.
159 TaskQueueEntryChunk* allocate_new_chunk();
160
161 // Atomically add the given chunk to the list.
162 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem);
163 // Atomically remove and return a chunk from the given list. Returns NULL if the
164 // list is empty.
165 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list);
166
167 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem);
168 void add_chunk_to_free_list(TaskQueueEntryChunk* elem);
169
170 TaskQueueEntryChunk* remove_chunk_from_chunk_list();
171 TaskQueueEntryChunk* remove_chunk_from_free_list();
172
173 // Resizes the mark stack to the given new capacity. Releases any previous
174 // memory if successful.
175 bool resize(size_t new_capacity);
176
177 public:
178 G1CMMarkStack();
179 ~G1CMMarkStack();
180
181 // Alignment and minimum capacity of this mark stack in number of oops.
182 static size_t capacity_alignment();
183
184 // Allocate and initialize the mark stack with the given number of oops.
185 bool initialize(size_t initial_capacity, size_t max_capacity);
186
187 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark
188 // stack. If less than EntriesPerChunk elements are to be pushed, the array must
189 // be terminated with a NULL.
190 // Returns whether the buffer contents were successfully pushed to the global mark
191 // stack.
192 bool par_push_chunk(G1TaskQueueEntry* buffer);
193
194 // Pops a chunk from this mark stack, copying them into the given buffer. This
195 // chunk may contain up to EntriesPerChunk elements. If there are less, the last
196 // element in the array is a NULL pointer.
197 bool par_pop_chunk(G1TaskQueueEntry* buffer);
198
199 // Return whether the chunk list is empty. Racy due to unsynchronized access to
200 // _chunk_list.
201 bool is_empty() const { return _chunk_list == NULL; }
202
203 size_t capacity() const { return _chunk_capacity; }
204
205 // Expand the stack, typically in response to an overflow condition
206 void expand();
207
208 // Return the approximate number of oops on this mark stack. Racy due to
209 // unsynchronized access to _chunks_in_chunk_list.
210 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; }
211
212 void set_empty();
213
214 // Apply Fn to every oop on the mark stack. The mark stack must not
215 // be modified while iterating.
216 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
217 };
218
219 // Root Regions are regions that are not empty at the beginning of a
220 // marking cycle and which we might collect during an evacuation pause
221 // while the cycle is active. Given that, during evacuation pauses, we
222 // do not copy objects that are explicitly marked, what we have to do
223 // for the root regions is to scan them and mark all objects reachable
224 // from them. According to the SATB assumptions, we only need to visit
225 // each object once during marking. So, as long as we finish this scan
226 // before the next evacuation pause, we can copy the objects from the
227 // root regions without having to mark them or do anything else to them.
228 //
229 // Currently, we only support root region scanning once (at the start
230 // of the marking cycle) and the root regions are all the survivor
231 // regions populated during the initial-mark pause.
232 class G1CMRootRegions {
233 private:
234 const G1SurvivorRegions* _survivors;
235 G1ConcurrentMark* _cm;
236
237 volatile bool _scan_in_progress;
238 volatile bool _should_abort;
239 volatile int _claimed_survivor_index;
240
241 void notify_scan_done();
242
243 public:
244 G1CMRootRegions();
245 // We actually do most of the initialization in this method.
246 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm);
247
248 // Reset the claiming / scanning of the root regions.
249 void prepare_for_scan();
250
251 // Forces get_next() to return NULL so that the iteration aborts early.
252 void abort() { _should_abort = true; }
253
254 // Return true if the CM thread are actively scanning root regions,
255 // false otherwise.
256 bool scan_in_progress() { return _scan_in_progress; }
257
258 // Claim the next root region to scan atomically, or return NULL if
259 // all have been claimed.
260 HeapRegion* claim_next();
261
262 // The number of root regions to scan.
263 uint num_root_regions() const;
264
265 void cancel_scan();
266
267 // Flag that we're done with root region scanning and notify anyone
268 // who's waiting on it. If aborted is false, assume that all regions
269 // have been claimed.
270 void scan_finished();
271
272 // If CM threads are still scanning root regions, wait until they
273 // are done. Return true if we had to wait, false otherwise.
274 bool wait_until_scan_finished();
275 };
276
277 // This class manages data structures and methods for doing liveness analysis in
278 // G1's concurrent cycle.
279 class G1ConcurrentMark : public CHeapObj<mtGC> {
280 friend class ConcurrentMarkThread;
281 friend class G1CMRefProcTaskProxy;
282 friend class G1CMRefProcTaskExecutor;
283 friend class G1CMKeepAliveAndDrainClosure;
284 friend class G1CMDrainMarkingStackClosure;
285 friend class G1CMBitMapClosure;
286 friend class G1CMConcurrentMarkingTask;
287 friend class G1CMRemarkTask;
288 friend class G1CMTask;
289
290 ConcurrentMarkThread* _cm_thread; // The thread doing the work
291 G1CollectedHeap* _g1h; // The heap
292 bool _completed_initialization; // Set to true when initialization is complete
293
294 // Concurrent marking support structures
295 G1CMBitMap _mark_bitmap_1;
296 G1CMBitMap _mark_bitmap_2;
297 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap
298 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap
299
300 // Heap bounds
301 MemRegion const _heap;
302
303 // Root region tracking and claiming
304 G1CMRootRegions _root_regions;
305
306 // For grey objects
307 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
308 HeapWord* volatile _finger; // The global finger, region aligned,
309 // always pointing to the end of the
310 // last claimed region
311
312 uint _worker_id_offset;
313 uint _max_num_tasks; // Maximum number of marking tasks
314 uint _num_active_tasks; // Number of tasks currently active
315 G1CMTask** _tasks; // Task queue array (max_worker_id length)
316
317 G1CMTaskQueueSet* _task_queues; // Task queue set
318 ParallelTaskTerminator _terminator; // For termination
319
320 // Two sync barriers that are used to synchronize tasks when an
321 // overflow occurs. The algorithm is the following. All tasks enter
322 // the first one to ensure that they have all stopped manipulating
323 // the global data structures. After they exit it, they re-initialize
324 // their data structures and task 0 re-initializes the global data
325 // structures. Then, they enter the second sync barrier. This
326 // ensure, that no task starts doing work before all data
327 // structures (local and global) have been re-initialized. When they
328 // exit it, they are free to start working again.
329 WorkGangBarrierSync _first_overflow_barrier_sync;
330 WorkGangBarrierSync _second_overflow_barrier_sync;
331
332 // This is set by any task, when an overflow on the global data
333 // structures is detected
334 volatile bool _has_overflown;
335 // True: marking is concurrent, false: we're in remark
336 volatile bool _concurrent;
337 // Set at the end of a Full GC so that marking aborts
338 volatile bool _has_aborted;
339
340 // Used when remark aborts due to an overflow to indicate that
341 // another concurrent marking phase should start
342 volatile bool _restart_for_overflow;
343
344 // This is true from the very start of concurrent marking until the
345 // point when all the tasks complete their work. It is really used
346 // to determine the points between the end of concurrent marking and
347 // time of remark.
348 volatile bool _concurrent_marking_in_progress;
349
350 ConcurrentGCTimer* _gc_timer_cm;
351
352 G1OldTracer* _gc_tracer_cm;
353
354 // Timing statistics. All of them are in ms
355 NumberSeq _init_times;
356 NumberSeq _remark_times;
357 NumberSeq _remark_mark_times;
358 NumberSeq _remark_weak_ref_times;
359 NumberSeq _cleanup_times;
360 double _total_cleanup_time;
361
362 double* _accum_task_vtime; // Accumulated task vtime
363
364 WorkGang* _concurrent_workers;
365 uint _num_concurrent_workers; // The number of marking worker threads we're using
366 uint _max_concurrent_workers; // Maximum number of marking worker threads
367
368 void finalize_marking();
369
370 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes);
371 void weak_refs_work(bool clear_all_soft_refs);
372
373 void swap_mark_bitmaps();
374
375 void reclaim_empty_regions();
376
377 // Resets the global marking data structures, as well as the
378 // task local ones; should be called during initial mark.
379 void reset();
380
381 // Resets all the marking data structures. Called when we have to restart
382 // marking or when marking completes (via set_non_marking_state below).
383 void reset_marking_for_restart();
384
385 // We do this after we're done with marking so that the marking data
386 // structures are initialized to a sensible and predictable state.
387 void reset_at_marking_complete();
388
389 // Called to indicate how many threads are currently active.
390 void set_concurrency(uint active_tasks);
391
392 // Should be called to indicate which phase we're in (concurrent
393 // mark or remark) and how many threads are currently active.
394 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
395
396 // Prints all gathered CM-related statistics
397 void print_stats();
398
399 HeapWord* finger() { return _finger; }
400 bool concurrent() { return _concurrent; }
401 uint active_tasks() { return _num_active_tasks; }
402 ParallelTaskTerminator* terminator() { return &_terminator; }
403
404 // Claims the next available region to be scanned by a marking
405 // task/thread. It might return NULL if the next region is empty or
406 // we have run out of regions. In the latter case, out_of_regions()
407 // determines whether we've really run out of regions or the task
408 // should call claim_region() again. This might seem a bit
409 // awkward. Originally, the code was written so that claim_region()
410 // either successfully returned with a non-empty region or there
411 // were no more regions to be claimed. The problem with this was
412 // that, in certain circumstances, it iterated over large chunks of
413 // the heap finding only empty regions and, while it was working, it
414 // was preventing the calling task to call its regular clock
415 // method. So, this way, each task will spend very little time in
416 // claim_region() and is allowed to call the regular clock method
417 // frequently.
418 HeapRegion* claim_region(uint worker_id);
419
420 // Determines whether we've run out of regions to scan. Note that
421 // the finger can point past the heap end in case the heap was expanded
422 // to satisfy an allocation without doing a GC. This is fine, because all
423 // objects in those regions will be considered live anyway because of
424 // SATB guarantees (i.e. their TAMS will be equal to bottom).
425 bool out_of_regions() { return _finger >= _heap.end(); }
426
427 // Returns the task with the given id
428 G1CMTask* task(uint id) {
429 // During initial mark we use the parallel gc threads to do some work, so
430 // we can only compare against _max_num_tasks.
431 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks);
432 return _tasks[id];
433 }
434
435 // Access / manipulation of the overflow flag which is set to
436 // indicate that the global stack has overflown
437 bool has_overflown() { return _has_overflown; }
438 void set_has_overflown() { _has_overflown = true; }
439 void clear_has_overflown() { _has_overflown = false; }
440 bool restart_for_overflow() { return _restart_for_overflow; }
441
442 // Methods to enter the two overflow sync barriers
443 void enter_first_sync_barrier(uint worker_id);
444 void enter_second_sync_barrier(uint worker_id);
445
446 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
447 // true, periodically insert checks to see if this method should exit prematurely.
448 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
449
450 // Clear statistics gathered during the concurrent cycle for the given region after
451 // it has been reclaimed.
452 void clear_statistics_in_region(uint region_idx);
453 // Region statistics gathered during marking.
454 G1RegionMarkStats* _region_mark_stats;
455 // Top pointer for each region at the start of the rebuild remembered set process
456 // for regions which remembered sets need to be rebuilt. A NULL for a given region
457 // means that this region does not be scanned during the rebuilding remembered
458 // set phase at all.
459 HeapWord* volatile* _top_at_rebuild_starts;
460 public:
461 void add_to_liveness(uint worker_id, oop const obj, size_t size);
462 // Liveness of the given region as determined by concurrent marking, i.e. the amount of
463 // live words between bottom and nTAMS.
464 size_t liveness(uint region) { return _region_mark_stats[region]._live_words; }
465
466 // Sets the internal top_at_region_start for the given region to current top of the region.
467 inline void update_top_at_rebuild_start(HeapRegion* r);
468 // TARS for the given region during remembered set rebuilding.
469 inline HeapWord* top_at_rebuild_start(uint region) const;
470
471 // Notification for eagerly reclaimed regions to clean up.
472 void humongous_object_eagerly_reclaimed(HeapRegion* r);
473 // Manipulation of the global mark stack.
474 // The push and pop operations are used by tasks for transfers
475 // between task-local queues and the global mark stack.
476 bool mark_stack_push(G1TaskQueueEntry* arr) {
477 if (!_global_mark_stack.par_push_chunk(arr)) {
478 set_has_overflown();
479 return false;
480 }
481 return true;
482 }
483 bool mark_stack_pop(G1TaskQueueEntry* arr) {
484 return _global_mark_stack.par_pop_chunk(arr);
485 }
486 size_t mark_stack_size() const { return _global_mark_stack.size(); }
487 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; }
488 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); }
489
490 G1CMRootRegions* root_regions() { return &_root_regions; }
491
492 bool concurrent_marking_in_progress() const {
493 return _concurrent_marking_in_progress;
494 }
495 void set_concurrent_marking_in_progress() {
496 _concurrent_marking_in_progress = true;
497 }
498 void clear_concurrent_marking_in_progress() {
499 _concurrent_marking_in_progress = false;
500 }
501
502 void concurrent_cycle_start();
503 // Abandon current marking iteration due to a Full GC.
504 void concurrent_cycle_abort();
505 void concurrent_cycle_end();
506
507 void update_accum_task_vtime(int i, double vtime) {
508 _accum_task_vtime[i] += vtime;
509 }
510
511 double all_task_accum_vtime() {
512 double ret = 0.0;
513 for (uint i = 0; i < _max_num_tasks; ++i)
514 ret += _accum_task_vtime[i];
515 return ret;
516 }
517
518 // Attempts to steal an object from the task queues of other tasks
519 bool try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry);
520
521 G1ConcurrentMark(G1CollectedHeap* g1h,
522 G1RegionToSpaceMapper* prev_bitmap_storage,
523 G1RegionToSpaceMapper* next_bitmap_storage);
524 ~G1ConcurrentMark();
525
526 ConcurrentMarkThread* cm_thread() { return _cm_thread; }
527
528 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; }
529 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; }
530
531 // Calculates the number of concurrent GC threads to be used in the marking phase.
532 uint calc_active_marking_workers();
533
534 // Moves all per-task cached data into global state.
535 void flush_all_task_caches();
536 // Prepare internal data structures for the next mark cycle. This includes clearing
537 // the next mark bitmap and some internal data structures. This method is intended
538 // to be called concurrently to the mutator. It will yield to safepoint requests.
539 void cleanup_for_next_mark();
540
541 // Clear the previous marking bitmap during safepoint.
542 void clear_prev_bitmap(WorkGang* workers);
543
544 // Return whether the next mark bitmap has no marks set. To be used for assertions
545 // only. Will not yield to pause requests.
546 bool next_mark_bitmap_is_clear();
547
548 // These two methods do the work that needs to be done at the start and end of the
549 // initial mark pause.
550 void pre_initial_mark();
551 void post_initial_mark();
552
553 // Scan all the root regions and mark everything reachable from
554 // them.
555 void scan_root_regions();
556
557 // Scan a single root region and mark everything reachable from it.
558 void scan_root_region(HeapRegion* hr, uint worker_id);
559
560 // Do concurrent phase of marking, to a tentative transitive closure.
561 void mark_from_roots();
562
563 void remark();
564
565 void cleanup();
566 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use
567 // this carefully.
568 inline void mark_in_prev_bitmap(oop p);
569
570 // Clears marks for all objects in the given range, for the prev or
571 // next bitmaps. Caution: the previous bitmap is usually
572 // read-only, so use this carefully!
573 void clear_range_in_prev_bitmap(MemRegion mr);
574
575 inline bool is_marked_in_prev_bitmap(oop p) const;
576
577 // Verify that there are no collection set oops on the stacks (taskqueues /
578 // global mark stack) and fingers (global / per-task).
579 // If marking is not in progress, it's a no-op.
580 void verify_no_cset_oops() PRODUCT_RETURN;
581
582 inline bool do_yield_check();
583
584 bool has_aborted() { return _has_aborted; }
585
586 void print_summary_info();
587
588 void print_worker_threads_on(outputStream* st) const;
589 void threads_do(ThreadClosure* tc) const;
590
591 void print_on_error(outputStream* st) const;
592
593 // Mark the given object on the next bitmap if it is below nTAMS.
594 // If the passed obj_size is zero, it is recalculated from the given object if
595 // needed. This is to be as lazy as possible with accessing the object's size.
596 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj, size_t const obj_size = 0);
597 inline bool mark_in_next_bitmap(uint worker_id, oop const obj, size_t const obj_size = 0);
598
599 // Returns true if initialization was successfully completed.
600 bool completed_initialization() const {
601 return _completed_initialization;
602 }
603
604 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
605 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
606
607 private:
608 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application.
609 void rebuild_rem_set_concurrently();
610 };
611
612 // A class representing a marking task.
613 class G1CMTask : public TerminatorTerminator {
614 private:
615 enum PrivateConstants {
616 // The regular clock call is called once the scanned words reaches
617 // this limit
618 words_scanned_period = 12*1024,
619 // The regular clock call is called once the number of visited
620 // references reaches this limit
621 refs_reached_period = 1024,
622 // Initial value for the hash seed, used in the work stealing code
623 init_hash_seed = 17
624 };
625
626 // Number of entries in the per-task stats entry. This seems enough to have a very
627 // low cache miss rate.
628 static const uint RegionMarkStatsCacheSize = 1024;
629
630 G1CMObjArrayProcessor _objArray_processor;
631
632 uint _worker_id;
633 G1CollectedHeap* _g1h;
634 G1ConcurrentMark* _cm;
635 G1CMBitMap* _next_mark_bitmap;
636 // the task queue of this task
637 G1CMTaskQueue* _task_queue;
638
639 G1RegionMarkStatsCache _mark_stats_cache;
640 // Number of calls to this task
641 uint _calls;
642
643 // When the virtual timer reaches this time, the marking step should exit
644 double _time_target_ms;
645 // Start time of the current marking step
646 double _start_time_ms;
647
648 // Oop closure used for iterations over oops
649 G1CMOopClosure* _cm_oop_closure;
650
651 // Region this task is scanning, NULL if we're not scanning any
652 HeapRegion* _curr_region;
653 // Local finger of this task, NULL if we're not scanning a region
654 HeapWord* _finger;
655 // Limit of the region this task is scanning, NULL if we're not scanning one
656 HeapWord* _region_limit;
657
658 // Number of words this task has scanned
659 size_t _words_scanned;
660 // When _words_scanned reaches this limit, the regular clock is
661 // called. Notice that this might be decreased under certain
662 // circumstances (i.e. when we believe that we did an expensive
663 // operation).
664 size_t _words_scanned_limit;
665 // Initial value of _words_scanned_limit (i.e. what it was
666 // before it was decreased).
667 size_t _real_words_scanned_limit;
668
669 // Number of references this task has visited
670 size_t _refs_reached;
671 // When _refs_reached reaches this limit, the regular clock is
672 // called. Notice this this might be decreased under certain
673 // circumstances (i.e. when we believe that we did an expensive
674 // operation).
675 size_t _refs_reached_limit;
676 // Initial value of _refs_reached_limit (i.e. what it was before
677 // it was decreased).
678 size_t _real_refs_reached_limit;
679
680 // Used by the work stealing
681 int _hash_seed;
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 // True when the task is during a concurrent phase, false when it is
701 // in the remark phase (so, in the latter case, we do not have to
702 // check all the things that we have to check during the concurrent
703 // phase, i.e. SATB buffer availability...)
704 bool _concurrent;
705
706 TruncatedSeq _marking_step_diffs_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 void regular_clock_call();
734
735 // Test whether obj might have already been passed over by the
736 // mark bitmap scan, and so needs to be pushed onto the mark stack.
737 bool is_below_finger(oop obj, HeapWord* global_finger) const;
738
739 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
740 public:
741 // Apply the closure on the given area of the objArray. Return the number of words
742 // scanned.
743 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
744 // Resets the task; should be called right at the beginning of a marking phase.
745 void reset(G1CMBitMap* next_mark_bitmap);
746 // Clears all the fields that correspond to a claimed region.
747 void clear_region_fields();
748
749 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
750
751 // The main method of this class which performs a marking step
752 // trying not to exceed the given duration. However, it might exit
753 // prematurely, according to some conditions (i.e. SATB buffers are
754 // available for processing).
755 void do_marking_step(double target_ms,
756 bool do_termination,
757 bool is_serial);
758
759 // These two calls start and stop the timer
760 void record_start_time() {
761 _elapsed_time_ms = os::elapsedTime() * 1000.0;
762 }
763 void record_end_time() {
764 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
765 }
766
767 // Returns the worker ID associated with this task.
768 uint worker_id() { return _worker_id; }
769
770 // From TerminatorTerminator. It determines whether this task should
771 // exit the termination protocol after it's entered it.
772 virtual bool should_exit_termination();
773
774 // Resets the local region fields after a task has finished scanning a
775 // region; or when they have become stale as a result of the region
776 // being evacuated.
777 void giveup_current_region();
778
779 HeapWord* finger() { return _finger; }
780
781 bool has_aborted() { return _has_aborted; }
782 void set_has_aborted() { _has_aborted = true; }
783 void clear_has_aborted() { _has_aborted = false; }
784
785 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
786
787 // Increment the number of references this task has visited.
788 void increment_refs_reached() { ++_refs_reached; }
789
790 // Grey the object by marking it. If not already marked, push it on
791 // the local queue if below the finger.
792 // obj is below its region's NTAMS.
793 inline void make_reference_grey(oop obj);
794
795 // Grey the object (by calling make_grey_reference) if required,
796 // e.g. obj is below its containing region's NTAMS.
797 // Precondition: obj is a valid heap object.
798 template <class T>
799 inline void 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 private:
853 // Accumulators for these values.
854 size_t _total_used_bytes;
855 size_t _total_capacity_bytes;
856 size_t _total_prev_live_bytes;
857 size_t _total_next_live_bytes;
858
859 // Accumulator for the remembered set size
860 size_t _total_remset_bytes;
861
862 // Accumulator for strong code roots memory size
863 size_t _total_strong_code_roots_bytes;
864
865 static double bytes_to_mb(size_t val) {
866 return (double) val / (double) M;
867 }
868
869 public:
870 // The header and footer are printed in the constructor and
871 // destructor respectively.
872 G1PrintRegionLivenessInfoClosure(const char* phase_name);
873 virtual bool do_heap_region(HeapRegion* r);
874 ~G1PrintRegionLivenessInfoClosure();
875 };
876
877 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP