1 /*
2 * Copyright (c) 2001, 2017, 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
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24
25 #ifndef SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
27
28 #include "classfile/javaClasses.hpp"
29 #include "gc/g1/g1ConcurrentMarkBitMap.hpp"
30 #include "gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp"
31 #include "gc/g1/g1RegionToSpaceMapper.hpp"
32 #include "gc/g1/heapRegionSet.hpp"
33 #include "gc/shared/taskqueue.hpp"
34
35 class G1CollectedHeap;
36 class G1CMBitMap;
37 class G1CMTask;
38 class G1ConcurrentMark;
39 class ConcurrentGCTimer;
40 class G1OldTracer;
41 class G1SurvivorRegions;
42
43 #ifdef _MSC_VER
44 #pragma warning(push)
45 // warning C4522: multiple assignment operators specified
46 #pragma warning(disable:4522)
47 #endif
48
49 // This is a container class for either an oop or a continuation address for
50 // mark stack entries. Both are pushed onto the mark stack.
51 class G1TaskQueueEntry VALUE_OBJ_CLASS_SPEC {
52 private:
53 void* _holder;
54
55 static const uintptr_t ArraySliceBit = 1;
56
57 G1TaskQueueEntry(oop obj) : _holder(obj) {
58 assert(_holder != NULL, "Not allowed to set NULL task queue element");
59 }
60 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { }
61 public:
62 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; }
63 G1TaskQueueEntry() : _holder(NULL) { }
64
65 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); }
66 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); }
67
68 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) {
69 _holder = t._holder;
70 return *this;
71 }
72
73 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile {
74 _holder = t._holder;
75 return *this;
76 }
77
78 oop obj() const {
79 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder));
80 return (oop)_holder;
81 }
82
83 HeapWord* slice() const {
84 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder));
85 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit);
86 }
87
88 bool is_oop() const { return !is_array_slice(); }
89 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; }
90 bool is_null() const { return _holder == NULL; }
91 };
92
93 #ifdef _MSC_VER
94 #pragma warning(pop)
95 #endif
96
97 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue;
98 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
99
100 // Closure used by CM during concurrent reference discovery
101 // and reference processing (during remarking) to determine
102 // if a particular object is alive. It is primarily used
103 // to determine if referents of discovered reference objects
104 // are alive. An instance is also embedded into the
105 // reference processor as the _is_alive_non_header field
106 class G1CMIsAliveClosure: public BoolObjectClosure {
107 G1CollectedHeap* _g1;
108 public:
109 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
110
111 bool do_object_b(oop obj);
112 };
113
114 // Represents the overflow mark stack used by concurrent marking.
115 //
116 // Stores oops in a huge buffer in virtual memory that is always fully committed.
117 // Resizing may only happen during a STW pause when the stack is empty.
118 //
119 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
120 // stack memory is split into evenly sized chunks of oops. Users can only
121 // add or remove entries on that basis.
122 // Chunks are filled in increasing address order. Not completely filled chunks
123 // have a NULL element as a terminating element.
124 //
125 // Every chunk has a header containing a single pointer element used for memory
126 // management. This wastes some space, but is negligible (< .1% with current sizing).
127 //
128 // Memory management is done using a mix of tracking a high water-mark indicating
129 // that all chunks at a lower address are valid chunks, and a singly linked free
130 // list connecting all empty chunks.
131 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC {
132 public:
133 // Number of TaskQueueEntries that can fit in a single chunk.
134 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */;
135 private:
136 struct TaskQueueEntryChunk {
137 TaskQueueEntryChunk* next;
138 G1TaskQueueEntry data[EntriesPerChunk];
139 };
140
141 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack.
142
143 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area.
144 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements.
145
146 char _pad0[DEFAULT_CACHE_LINE_SIZE];
147 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
148 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)];
149 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data.
150 volatile size_t _chunks_in_chunk_list;
151 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)];
152
153 volatile size_t _hwm; // High water mark within the reserved space.
154 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
155
156 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
157 // NULL if out of memory.
158 TaskQueueEntryChunk* allocate_new_chunk();
159
160 // Atomically add the given chunk to the list.
161 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem);
162 // Atomically remove and return a chunk from the given list. Returns NULL if the
163 // list is empty.
164 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list);
165
166 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem);
167 void add_chunk_to_free_list(TaskQueueEntryChunk* elem);
168
169 TaskQueueEntryChunk* remove_chunk_from_chunk_list();
170 TaskQueueEntryChunk* remove_chunk_from_free_list();
171
172 // Resizes the mark stack to the given new capacity. Releases any previous
173 // memory if successful.
174 bool resize(size_t new_capacity);
175
176 public:
177 G1CMMarkStack();
178 ~G1CMMarkStack();
179
180 // Alignment and minimum capacity of this mark stack in number of oops.
181 static size_t capacity_alignment();
182
183 // Allocate and initialize the mark stack with the given number of oops.
184 bool initialize(size_t initial_capacity, size_t max_capacity);
185
186 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark
187 // stack. If less than EntriesPerChunk elements are to be pushed, the array must
188 // be terminated with a NULL.
189 // Returns whether the buffer contents were successfully pushed to the global mark
190 // stack.
191 bool par_push_chunk(G1TaskQueueEntry* buffer);
192
193 // Pops a chunk from this mark stack, copying them into the given buffer. This
194 // chunk may contain up to EntriesPerChunk elements. If there are less, the last
195 // element in the array is a NULL pointer.
196 bool par_pop_chunk(G1TaskQueueEntry* buffer);
197
198 // Return whether the chunk list is empty. Racy due to unsynchronized access to
199 // _chunk_list.
200 bool is_empty() const { return _chunk_list == NULL; }
201
202 size_t capacity() const { return _chunk_capacity; }
203
204 // Expand the stack, typically in response to an overflow condition
205 void expand();
206
207 // Return the approximate number of oops on this mark stack. Racy due to
208 // unsynchronized access to _chunks_in_chunk_list.
209 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; }
210
211 void set_empty();
212
213 // Apply Fn to every oop on the mark stack. The mark stack must not
214 // be modified while iterating.
215 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
216 };
217
218 // Root Regions are regions that are not empty at the beginning of a
219 // marking cycle and which we might collect during an evacuation pause
220 // while the cycle is active. Given that, during evacuation pauses, we
221 // do not copy objects that are explicitly marked, what we have to do
222 // for the root regions is to scan them and mark all objects reachable
223 // from them. According to the SATB assumptions, we only need to visit
224 // each object once during marking. So, as long as we finish this scan
225 // before the next evacuation pause, we can copy the objects from the
226 // root regions without having to mark them or do anything else to them.
227 //
228 // Currently, we only support root region scanning once (at the start
229 // of the marking cycle) and the root regions are all the survivor
230 // regions populated during the initial-mark pause.
231 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC {
232 private:
233 const G1SurvivorRegions* _survivors;
234 G1ConcurrentMark* _cm;
235
236 volatile bool _scan_in_progress;
237 volatile bool _should_abort;
238 volatile int _claimed_survivor_index;
239
240 void notify_scan_done();
241
242 public:
243 G1CMRootRegions();
244 // We actually do most of the initialization in this method.
245 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm);
246
247 // Reset the claiming / scanning of the root regions.
248 void prepare_for_scan();
249
250 // Forces get_next() to return NULL so that the iteration aborts early.
251 void abort() { _should_abort = true; }
252
253 // Return true if the CM thread are actively scanning root regions,
254 // false otherwise.
255 bool scan_in_progress() { return _scan_in_progress; }
256
257 // Claim the next root region to scan atomically, or return NULL if
258 // all have been claimed.
259 HeapRegion* claim_next();
260
261 // The number of root regions to scan.
262 uint num_root_regions() const;
263
264 void cancel_scan();
265
266 // Flag that we're done with root region scanning and notify anyone
267 // who's waiting on it. If aborted is false, assume that all regions
268 // have been claimed.
269 void scan_finished();
270
271 // If CM threads are still scanning root regions, wait until they
272 // are done. Return true if we had to wait, false otherwise.
273 bool wait_until_scan_finished();
274 };
275
276 class ConcurrentMarkThread;
277
278 class G1ConcurrentMark: public CHeapObj<mtGC> {
279 friend class ConcurrentMarkThread;
280 friend class G1ParNoteEndTask;
281 friend class G1VerifyLiveDataClosure;
282 friend class G1CMRefProcTaskProxy;
283 friend class G1CMRefProcTaskExecutor;
284 friend class G1CMKeepAliveAndDrainClosure;
285 friend class G1CMDrainMarkingStackClosure;
286 friend class G1CMBitMapClosure;
287 friend class G1CMConcurrentMarkingTask;
288 friend class G1CMRemarkTask;
289 friend class G1CMTask;
290
291 protected:
292 ConcurrentMarkThread* _cmThread; // The thread doing the work
293 G1CollectedHeap* _g1h; // The heap
294 uint _parallel_marking_threads; // The number of marking
295 // threads we're using
296 uint _max_parallel_marking_threads; // Max number of marking
297 // threads we'll ever use
298 double _sleep_factor; // How much we have to sleep, with
299 // respect to the work we just did, to
300 // meet the marking overhead goal
301 double _marking_task_overhead; // Marking target overhead for
302 // a single task
303
304 FreeRegionList _cleanup_list;
305
306 // Concurrent marking support structures
307 G1CMBitMap _markBitMap1;
308 G1CMBitMap _markBitMap2;
309 G1CMBitMap* _prevMarkBitMap; // Completed mark bitmap
310 G1CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
311
312 // Heap bounds
313 HeapWord* _heap_start;
314 HeapWord* _heap_end;
315
316 // Root region tracking and claiming
317 G1CMRootRegions _root_regions;
318
319 // For gray objects
320 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
321 HeapWord* volatile _finger; // The global finger, region aligned,
322 // always points to the end of the
323 // last claimed region
324
325 // Marking tasks
326 uint _max_worker_id;// Maximum worker id
327 uint _active_tasks; // Task num currently active
328 G1CMTask** _tasks; // Task queue array (max_worker_id len)
329 G1CMTaskQueueSet* _task_queues; // Task queue set
330 ParallelTaskTerminator _terminator; // For termination
331
332 // Two sync barriers that are used to synchronize tasks when an
333 // overflow occurs. The algorithm is the following. All tasks enter
334 // the first one to ensure that they have all stopped manipulating
335 // the global data structures. After they exit it, they re-initialize
336 // their data structures and task 0 re-initializes the global data
337 // structures. Then, they enter the second sync barrier. This
338 // ensure, that no task starts doing work before all data
339 // structures (local and global) have been re-initialized. When they
340 // exit it, they are free to start working again.
341 WorkGangBarrierSync _first_overflow_barrier_sync;
342 WorkGangBarrierSync _second_overflow_barrier_sync;
343
344 // This is set by any task, when an overflow on the global data
345 // structures is detected
346 volatile bool _has_overflown;
347 // True: marking is concurrent, false: we're in remark
348 volatile bool _concurrent;
349 // Set at the end of a Full GC so that marking aborts
350 volatile bool _has_aborted;
351
352 // Used when remark aborts due to an overflow to indicate that
353 // another concurrent marking phase should start
354 volatile bool _restart_for_overflow;
355
356 // This is true from the very start of concurrent marking until the
357 // point when all the tasks complete their work. It is really used
358 // to determine the points between the end of concurrent marking and
359 // time of remark.
360 volatile bool _concurrent_marking_in_progress;
361
362 ConcurrentGCTimer* _gc_timer_cm;
363
364 G1OldTracer* _gc_tracer_cm;
365
366 // All of these times are in ms
367 NumberSeq _init_times;
368 NumberSeq _remark_times;
369 NumberSeq _remark_mark_times;
370 NumberSeq _remark_weak_ref_times;
371 NumberSeq _cleanup_times;
372 double _total_counting_time;
373 double _total_rs_scrub_time;
374
375 double* _accum_task_vtime; // Accumulated task vtime
376
377 WorkGang* _parallel_workers;
378
379 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
380 void weakRefsWork(bool clear_all_soft_refs);
381
382 void swapMarkBitMaps();
383
384 // It resets the global marking data structures, as well as the
385 // task local ones; should be called during initial mark.
386 void reset();
387
388 // Resets all the marking data structures. Called when we have to restart
389 // marking or when marking completes (via set_non_marking_state below).
390 void reset_marking_state();
391
392 // We do this after we're done with marking so that the marking data
393 // structures are initialized to a sensible and predictable state.
394 void set_non_marking_state();
395
396 // Called to indicate how many threads are currently active.
397 void set_concurrency(uint active_tasks);
398
399 // It should be called to indicate which phase we're in (concurrent
400 // mark or remark) and how many threads are currently active.
401 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
402
403 // Prints all gathered CM-related statistics
404 void print_stats();
405
406 bool cleanup_list_is_empty() {
407 return _cleanup_list.is_empty();
408 }
409
410 // Accessor methods
411 uint parallel_marking_threads() const { return _parallel_marking_threads; }
412 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
413 double sleep_factor() { return _sleep_factor; }
414 double marking_task_overhead() { return _marking_task_overhead;}
415
416 HeapWord* finger() { return _finger; }
417 bool concurrent() { return _concurrent; }
418 uint active_tasks() { return _active_tasks; }
419 ParallelTaskTerminator* terminator() { return &_terminator; }
420
421 // It claims the next available region to be scanned by a marking
422 // task/thread. It might return NULL if the next region is empty or
423 // we have run out of regions. In the latter case, out_of_regions()
424 // determines whether we've really run out of regions or the task
425 // should call claim_region() again. This might seem a bit
426 // awkward. Originally, the code was written so that claim_region()
427 // either successfully returned with a non-empty region or there
428 // were no more regions to be claimed. The problem with this was
429 // that, in certain circumstances, it iterated over large chunks of
430 // the heap finding only empty regions and, while it was working, it
431 // was preventing the calling task to call its regular clock
432 // method. So, this way, each task will spend very little time in
433 // claim_region() and is allowed to call the regular clock method
434 // frequently.
435 HeapRegion* claim_region(uint worker_id);
436
437 // It determines whether we've run out of regions to scan. Note that
438 // the finger can point past the heap end in case the heap was expanded
439 // to satisfy an allocation without doing a GC. This is fine, because all
440 // objects in those regions will be considered live anyway because of
441 // SATB guarantees (i.e. their TAMS will be equal to bottom).
442 bool out_of_regions() { return _finger >= _heap_end; }
443
444 // Returns the task with the given id
445 G1CMTask* task(int id) {
446 assert(0 <= id && id < (int) _active_tasks,
447 "task id not within active bounds");
448 return _tasks[id];
449 }
450
451 // Returns the task queue with the given id
452 G1CMTaskQueue* task_queue(int id) {
453 assert(0 <= id && id < (int) _active_tasks,
454 "task queue id not within active bounds");
455 return (G1CMTaskQueue*) _task_queues->queue(id);
456 }
457
458 // Returns the task queue set
459 G1CMTaskQueueSet* task_queues() { return _task_queues; }
460
461 // Access / manipulation of the overflow flag which is set to
462 // indicate that the global stack has overflown
463 bool has_overflown() { return _has_overflown; }
464 void set_has_overflown() { _has_overflown = true; }
465 void clear_has_overflown() { _has_overflown = false; }
466 bool restart_for_overflow() { return _restart_for_overflow; }
467
468 // Methods to enter the two overflow sync barriers
469 void enter_first_sync_barrier(uint worker_id);
470 void enter_second_sync_barrier(uint worker_id);
471
472 // Card index of the bottom of the G1 heap. Used for biasing indices into
473 // the card bitmaps.
474 intptr_t _heap_bottom_card_num;
475
476 // Set to true when initialization is complete
477 bool _completed_initialization;
478
479 // end_timer, true to end gc timer after ending concurrent phase.
480 void register_concurrent_phase_end_common(bool end_timer);
481
482 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
483 // true, periodically insert checks to see if this method should exit prematurely.
484 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
485 public:
486 // Manipulation of the global mark stack.
487 // The push and pop operations are used by tasks for transfers
488 // between task-local queues and the global mark stack.
489 bool mark_stack_push(G1TaskQueueEntry* arr) {
490 if (!_global_mark_stack.par_push_chunk(arr)) {
491 set_has_overflown();
492 return false;
493 }
494 return true;
495 }
496 bool mark_stack_pop(G1TaskQueueEntry* arr) {
497 return _global_mark_stack.par_pop_chunk(arr);
498 }
499 size_t mark_stack_size() { return _global_mark_stack.size(); }
500 size_t partial_mark_stack_size_target() { return _global_mark_stack.capacity()/3; }
501 bool mark_stack_empty() { return _global_mark_stack.is_empty(); }
502
503 G1CMRootRegions* root_regions() { return &_root_regions; }
504
505 bool concurrent_marking_in_progress() {
506 return _concurrent_marking_in_progress;
507 }
508 void set_concurrent_marking_in_progress() {
509 _concurrent_marking_in_progress = true;
510 }
511 void clear_concurrent_marking_in_progress() {
512 _concurrent_marking_in_progress = false;
513 }
514
515 void concurrent_cycle_start();
516 void concurrent_cycle_end();
517
518 void update_accum_task_vtime(int i, double vtime) {
519 _accum_task_vtime[i] += vtime;
520 }
521
522 double all_task_accum_vtime() {
523 double ret = 0.0;
524 for (uint i = 0; i < _max_worker_id; ++i)
525 ret += _accum_task_vtime[i];
526 return ret;
527 }
528
529 // Attempts to steal an object from the task queues of other tasks
530 bool try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry);
531
532 G1ConcurrentMark(G1CollectedHeap* g1h,
533 G1RegionToSpaceMapper* prev_bitmap_storage,
534 G1RegionToSpaceMapper* next_bitmap_storage);
535 ~G1ConcurrentMark();
536
537 ConcurrentMarkThread* cmThread() { return _cmThread; }
538
539 G1CMBitMapRO prevMarkBitMap() const { return G1CMBitMapRO(_prevMarkBitMap); }
540 G1CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
541
542 // Returns the number of GC threads to be used in a concurrent
543 // phase based on the number of GC threads being used in a STW
544 // phase.
545 uint scale_parallel_threads(uint n_par_threads);
546
547 // Calculates the number of GC threads to be used in a concurrent phase.
548 uint calc_parallel_marking_threads();
549
550 // The following three are interaction between CM and
551 // G1CollectedHeap
552
553 // This notifies CM that a root during initial-mark needs to be
554 // grayed. It is MT-safe. hr is the region that
555 // contains the object and it's passed optionally from callers who
556 // might already have it (no point in recalculating it).
557 inline void grayRoot(oop obj,
558 HeapRegion* hr = NULL);
559
560 // Prepare internal data structures for the next mark cycle. This includes clearing
561 // the next mark bitmap and some internal data structures. This method is intended
562 // to be called concurrently to the mutator. It will yield to safepoint requests.
563 void cleanup_for_next_mark();
564
565 // Clear the previous marking bitmap during safepoint.
566 void clear_prev_bitmap(WorkGang* workers);
567
568 // Return whether the next mark bitmap has no marks set. To be used for assertions
569 // only. Will not yield to pause requests.
570 bool nextMarkBitmapIsClear();
571
572 // These two do the work that needs to be done before and after the
573 // initial root checkpoint. Since this checkpoint can be done at two
574 // different points (i.e. an explicit pause or piggy-backed on a
575 // young collection), then it's nice to be able to easily share the
576 // pre/post code. It might be the case that we can put everything in
577 // the post method. TP
578 void checkpointRootsInitialPre();
579 void checkpointRootsInitialPost();
580
581 // Scan all the root regions and mark everything reachable from
582 // them.
583 void scan_root_regions();
584
585 // Scan a single root region and mark everything reachable from it.
586 void scanRootRegion(HeapRegion* hr);
587
588 // Do concurrent phase of marking, to a tentative transitive closure.
589 void mark_from_roots();
590
591 void checkpointRootsFinal(bool clear_all_soft_refs);
592 void checkpointRootsFinalWork();
593 void cleanup();
594 void complete_cleanup();
595
596 // Mark in the previous bitmap. NB: this is usually read-only, so use
597 // this carefully!
598 inline void markPrev(oop p);
599
600 // Clears marks for all objects in the given range, for the prev or
601 // next bitmaps. NB: the previous bitmap is usually
602 // read-only, so use this carefully!
603 void clearRangePrevBitmap(MemRegion mr);
604
605 // Verify that there are no CSet oops on the stacks (taskqueues /
606 // global mark stack) and fingers (global / per-task).
607 // If marking is not in progress, it's a no-op.
608 void verify_no_cset_oops() PRODUCT_RETURN;
609
610 inline bool isPrevMarked(oop p) const;
611
612 inline bool do_yield_check();
613
614 // Abandon current marking iteration due to a Full GC.
615 void abort();
616
617 bool has_aborted() { return _has_aborted; }
618
619 void print_summary_info();
620
621 void print_worker_threads_on(outputStream* st) const;
622 void threads_do(ThreadClosure* tc) const;
623
624 void print_on_error(outputStream* st) const;
625
626 // Attempts to mark the given object on the next mark bitmap.
627 inline bool par_mark(oop obj);
628
629 // Returns true if initialization was successfully completed.
630 bool completed_initialization() const {
631 return _completed_initialization;
632 }
633
634 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
635 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
636
637 private:
638 // Clear (Reset) all liveness count data.
639 void clear_live_data(WorkGang* workers);
640
641 #ifdef ASSERT
642 // Verify all of the above data structures that they are in initial state.
643 void verify_live_data_clear();
644 #endif
645
646 // Aggregates the per-card liveness data based on the current marking. Also sets
647 // the amount of marked bytes for each region.
648 void create_live_data();
649
650 void finalize_live_data();
651
652 void verify_live_data();
653 };
654
655 // A class representing a marking task.
656 class G1CMTask : public TerminatorTerminator {
657 private:
658 enum PrivateConstants {
659 // The regular clock call is called once the scanned words reaches
660 // this limit
661 words_scanned_period = 12*1024,
662 // The regular clock call is called once the number of visited
663 // references reaches this limit
664 refs_reached_period = 1024,
665 // Initial value for the hash seed, used in the work stealing code
666 init_hash_seed = 17
667 };
668
669 G1CMObjArrayProcessor _objArray_processor;
670
671 uint _worker_id;
672 G1CollectedHeap* _g1h;
673 G1ConcurrentMark* _cm;
674 G1CMBitMap* _nextMarkBitMap;
675 // the task queue of this task
676 G1CMTaskQueue* _task_queue;
677 private:
678 // the task queue set---needed for stealing
679 G1CMTaskQueueSet* _task_queues;
680 // indicates whether the task has been claimed---this is only for
681 // debugging purposes
682 bool _claimed;
683
684 // number of calls to this task
685 int _calls;
686
687 // when the virtual timer reaches this time, the marking step should
688 // exit
689 double _time_target_ms;
690 // the start time of the current marking step
691 double _start_time_ms;
692
693 // the oop closure used for iterations over oops
694 G1CMOopClosure* _cm_oop_closure;
695
696 // the region this task is scanning, NULL if we're not scanning any
697 HeapRegion* _curr_region;
698 // the local finger of this task, NULL if we're not scanning a region
699 HeapWord* _finger;
700 // limit of the region this task is scanning, NULL if we're not scanning one
701 HeapWord* _region_limit;
702
703 // the number of words this task has scanned
704 size_t _words_scanned;
705 // When _words_scanned reaches this limit, the regular clock is
706 // called. Notice that this might be decreased under certain
707 // circumstances (i.e. when we believe that we did an expensive
708 // operation).
709 size_t _words_scanned_limit;
710 // the initial value of _words_scanned_limit (i.e. what it was
711 // before it was decreased).
712 size_t _real_words_scanned_limit;
713
714 // the number of references this task has visited
715 size_t _refs_reached;
716 // When _refs_reached reaches this limit, the regular clock is
717 // called. Notice this this might be decreased under certain
718 // circumstances (i.e. when we believe that we did an expensive
719 // operation).
720 size_t _refs_reached_limit;
721 // the initial value of _refs_reached_limit (i.e. what it was before
722 // it was decreased).
723 size_t _real_refs_reached_limit;
724
725 // used by the work stealing stuff
726 int _hash_seed;
727 // if this is true, then the task has aborted for some reason
728 bool _has_aborted;
729 // set when the task aborts because it has met its time quota
730 bool _has_timed_out;
731 // true when we're draining SATB buffers; this avoids the task
732 // aborting due to SATB buffers being available (as we're already
733 // dealing with them)
734 bool _draining_satb_buffers;
735
736 // number sequence of past step times
737 NumberSeq _step_times_ms;
738 // elapsed time of this task
739 double _elapsed_time_ms;
740 // termination time of this task
741 double _termination_time_ms;
742 // when this task got into the termination protocol
743 double _termination_start_time_ms;
744
745 // true when the task is during a concurrent phase, false when it is
746 // in the remark phase (so, in the latter case, we do not have to
747 // check all the things that we have to check during the concurrent
748 // phase, i.e. SATB buffer availability...)
749 bool _concurrent;
750
751 TruncatedSeq _marking_step_diffs_ms;
752
753 // it updates the local fields after this task has claimed
754 // a new region to scan
755 void setup_for_region(HeapRegion* hr);
756 // it brings up-to-date the limit of the region
757 void update_region_limit();
758
759 // called when either the words scanned or the refs visited limit
760 // has been reached
761 void reached_limit();
762 // recalculates the words scanned and refs visited limits
763 void recalculate_limits();
764 // decreases the words scanned and refs visited limits when we reach
765 // an expensive operation
766 void decrease_limits();
767 // it checks whether the words scanned or refs visited reached their
768 // respective limit and calls reached_limit() if they have
769 void check_limits() {
770 if (_words_scanned >= _words_scanned_limit ||
771 _refs_reached >= _refs_reached_limit) {
772 reached_limit();
773 }
774 }
775 // this is supposed to be called regularly during a marking step as
776 // it checks a bunch of conditions that might cause the marking step
777 // to abort
778 void regular_clock_call();
779 bool concurrent() { return _concurrent; }
780
781 // Test whether obj might have already been passed over by the
782 // mark bitmap scan, and so needs to be pushed onto the mark stack.
783 bool is_below_finger(oop obj, HeapWord* global_finger) const;
784
785 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
786 public:
787 // Apply the closure on the given area of the objArray. Return the number of words
788 // scanned.
789 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
790 // It resets the task; it should be called right at the beginning of
791 // a marking phase.
792 void reset(G1CMBitMap* _nextMarkBitMap);
793 // it clears all the fields that correspond to a claimed region.
794 void clear_region_fields();
795
796 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
797
798 // The main method of this class which performs a marking step
799 // trying not to exceed the given duration. However, it might exit
800 // prematurely, according to some conditions (i.e. SATB buffers are
801 // available for processing).
802 void do_marking_step(double target_ms,
803 bool do_termination,
804 bool is_serial);
805
806 // These two calls start and stop the timer
807 void record_start_time() {
808 _elapsed_time_ms = os::elapsedTime() * 1000.0;
809 }
810 void record_end_time() {
811 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
812 }
813
814 // returns the worker ID associated with this task.
815 uint worker_id() { return _worker_id; }
816
817 // From TerminatorTerminator. It determines whether this task should
818 // exit the termination protocol after it's entered it.
819 virtual bool should_exit_termination();
820
821 // Resets the local region fields after a task has finished scanning a
822 // region; or when they have become stale as a result of the region
823 // being evacuated.
824 void giveup_current_region();
825
826 HeapWord* finger() { return _finger; }
827
828 bool has_aborted() { return _has_aborted; }
829 void set_has_aborted() { _has_aborted = true; }
830 void clear_has_aborted() { _has_aborted = false; }
831 bool has_timed_out() { return _has_timed_out; }
832 bool claimed() { return _claimed; }
833
834 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
835
836 // Increment the number of references this task has visited.
837 void increment_refs_reached() { ++_refs_reached; }
838
839 // Grey the object by marking it. If not already marked, push it on
840 // the local queue if below the finger.
841 // obj is below its region's NTAMS.
842 inline void make_reference_grey(oop obj);
843
844 // Grey the object (by calling make_grey_reference) if required,
845 // e.g. obj is below its containing region's NTAMS.
846 // Precondition: obj is a valid heap object.
847 inline void deal_with_reference(oop obj);
848
849 // It scans an object and visits its children.
850 inline void scan_task_entry(G1TaskQueueEntry task_entry);
851
852 // It pushes an object on the local queue.
853 inline void push(G1TaskQueueEntry task_entry);
854
855 // Move entries to the global stack.
856 void move_entries_to_global_stack();
857 // Move entries from the global stack, return true if we were successful to do so.
858 bool get_entries_from_global_stack();
859
860 // It pops and scans objects from the local queue. If partially is
861 // true, then it stops when the queue size is of a given limit. If
862 // partially is false, then it stops when the queue is empty.
863 void drain_local_queue(bool partially);
864 // It moves entries from the global stack to the local queue and
865 // drains the local queue. If partially is true, then it stops when
866 // both the global stack and the local queue reach a given size. If
867 // partially if false, it tries to empty them totally.
868 void drain_global_stack(bool partially);
869 // It keeps picking SATB buffers and processing them until no SATB
870 // buffers are available.
871 void drain_satb_buffers();
872
873 // moves the local finger to a new location
874 inline void move_finger_to(HeapWord* new_finger) {
875 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
876 _finger = new_finger;
877 }
878
879 G1CMTask(uint worker_id,
880 G1ConcurrentMark *cm,
881 G1CMTaskQueue* task_queue,
882 G1CMTaskQueueSet* task_queues);
883
884 // it prints statistics associated with this task
885 void print_stats();
886 };
887
888 // Class that's used to to print out per-region liveness
889 // information. It's currently used at the end of marking and also
890 // after we sort the old regions at the end of the cleanup operation.
891 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
892 private:
893 // Accumulators for these values.
894 size_t _total_used_bytes;
895 size_t _total_capacity_bytes;
896 size_t _total_prev_live_bytes;
897 size_t _total_next_live_bytes;
898
899 // Accumulator for the remembered set size
900 size_t _total_remset_bytes;
901
902 // Accumulator for strong code roots memory size
903 size_t _total_strong_code_roots_bytes;
904
905 static double perc(size_t val, size_t total) {
906 if (total == 0) {
907 return 0.0;
908 } else {
909 return 100.0 * ((double) val / (double) total);
910 }
911 }
912
913 static double bytes_to_mb(size_t val) {
914 return (double) val / (double) M;
915 }
916
917 public:
918 // The header and footer are printed in the constructor and
919 // destructor respectively.
920 G1PrintRegionLivenessInfoClosure(const char* phase_name);
921 virtual bool doHeapRegion(HeapRegion* r);
922 ~G1PrintRegionLivenessInfoClosure();
923 };
924
925 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP