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_VM_GC_G1_G1CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
27
28 #include "classfile/javaClasses.hpp"
29 #include "gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp"
30 #include "gc/g1/g1RegionToSpaceMapper.hpp"
31 #include "gc/g1/heapRegionSet.hpp"
32 #include "gc/shared/taskqueue.hpp"
33
34 class G1CollectedHeap;
35 class G1CMBitMap;
36 class G1CMTask;
37 class G1ConcurrentMark;
38 class ConcurrentGCTimer;
39 class G1OldTracer;
40 class G1SurvivorRegions;
41 typedef GenericTaskQueue<oop, mtGC> G1CMTaskQueue;
42 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
43
44 // Closure used by CM during concurrent reference discovery
45 // and reference processing (during remarking) to determine
46 // if a particular object is alive. It is primarily used
47 // to determine if referents of discovered reference objects
48 // are alive. An instance is also embedded into the
49 // reference processor as the _is_alive_non_header field
50 class G1CMIsAliveClosure: public BoolObjectClosure {
51 G1CollectedHeap* _g1;
52 public:
53 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
54
55 bool do_object_b(oop obj);
56 };
57
58 // A generic CM bit map. This is essentially a wrapper around the BitMap
59 // class, with one bit per (1<<_shifter) HeapWords.
60
61 class G1CMBitMapRO VALUE_OBJ_CLASS_SPEC {
62 protected:
63 HeapWord* _bmStartWord; // base address of range covered by map
64 size_t _bmWordSize; // map size (in #HeapWords covered)
65 const int _shifter; // map to char or bit
66 BitMapView _bm; // the bit map itself
67
68 public:
69 // constructor
70 G1CMBitMapRO(int shifter);
71
72 // inquiries
73 HeapWord* startWord() const { return _bmStartWord; }
74 // the following is one past the last word in space
75 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
76
77 // read marks
78
79 bool isMarked(HeapWord* addr) const {
80 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
81 "outside underlying space?");
82 return _bm.at(heapWordToOffset(addr));
83 }
84
85 // iteration
86 inline bool iterate(BitMapClosure* cl, MemRegion mr);
87
88 // Return the address corresponding to the next marked bit at or after
89 // "addr", and before "limit", if "limit" is non-NULL. If there is no
90 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
91 HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
92 const HeapWord* limit = NULL) const;
93
94 // conversion utilities
95 HeapWord* offsetToHeapWord(size_t offset) const {
96 return _bmStartWord + (offset << _shifter);
97 }
98 size_t heapWordToOffset(const HeapWord* addr) const {
99 return pointer_delta(addr, _bmStartWord) >> _shifter;
100 }
101
102 // The argument addr should be the start address of a valid object
103 inline HeapWord* nextObject(HeapWord* addr);
104
105 void print_on_error(outputStream* st, const char* prefix) const;
106
107 // debugging
108 NOT_PRODUCT(bool covers(MemRegion rs) const;)
109 };
110
111 class G1CMBitMapMappingChangedListener : public G1MappingChangedListener {
112 private:
113 G1CMBitMap* _bm;
114 public:
115 G1CMBitMapMappingChangedListener() : _bm(NULL) {}
116
117 void set_bitmap(G1CMBitMap* bm) { _bm = bm; }
118
119 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
120 };
121
122 class G1CMBitMap : public G1CMBitMapRO {
123 private:
124 G1CMBitMapMappingChangedListener _listener;
125
126 public:
127 static size_t compute_size(size_t heap_size);
128 // Returns the amount of bytes on the heap between two marks in the bitmap.
129 static size_t mark_distance();
130 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
131 // mark bitmap corresponds to. This is the same as the mark distance above.
132 static size_t heap_map_factor() {
133 return mark_distance();
134 }
135
136 G1CMBitMap() : G1CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
137
138 // Initializes the underlying BitMap to cover the given area.
139 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
140
141 // Write marks.
142 inline void mark(HeapWord* addr);
143 inline void clear(HeapWord* addr);
144 inline bool parMark(HeapWord* addr);
145
146 void clear_range(MemRegion mr);
147 };
148
149 // Represents the overflow mark stack used by concurrent marking.
150 //
151 // Stores oops in a huge buffer in virtual memory that is always fully committed.
152 // Resizing may only happen during a STW pause when the stack is empty.
153 //
154 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
155 // stack memory is split into evenly sized chunks of oops. Users can only
156 // add or remove entries on that basis.
157 // Chunks are filled in increasing address order. Not completely filled chunks
158 // have a NULL element as a terminating element.
159 //
160 // Every chunk has a header containing a single pointer element used for memory
161 // management. This wastes some space, but is negligible (< .1% with current sizing).
162 //
163 // Memory management is done using a mix of tracking a high water-mark indicating
164 // that all chunks at a lower address are valid chunks, and a singly linked free
165 // list connecting all empty chunks.
166 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC {
167 public:
168 // Number of oops that can fit in a single chunk.
169 static const size_t OopsPerChunk = 1024 - 1 /* One reference for the next pointer */;
170 private:
171 struct OopChunk {
172 OopChunk* next;
173 oop data[OopsPerChunk];
174 };
175
176 size_t _max_chunk_capacity; // Maximum number of OopChunk elements on the stack.
177
178 OopChunk* _base; // Bottom address of allocated memory area.
179 size_t _chunk_capacity; // Current maximum number of OopChunk elements.
180
181 char _pad0[DEFAULT_CACHE_LINE_SIZE];
182 OopChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
183 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(OopChunk*)];
184 OopChunk* volatile _chunk_list; // List of chunks currently containing data.
185 volatile size_t _chunks_in_chunk_list;
186 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(OopChunk*) - sizeof(size_t)];
187
188 volatile size_t _hwm; // High water mark within the reserved space.
189 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
190
191 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
192 // NULL if out of memory.
193 OopChunk* allocate_new_chunk();
194
195 // This is set by any task, when an overflow on the global data
196 // structures is detected
197 volatile bool _out_of_memory;
198
199 // Atomically add the given chunk to the list.
200 void add_chunk_to_list(OopChunk* volatile* list, OopChunk* elem);
201 // Atomically remove and return a chunk from the given list. Returns NULL if the
202 // list is empty.
203 OopChunk* remove_chunk_from_list(OopChunk* volatile* list);
204
205 void add_chunk_to_chunk_list(OopChunk* elem);
206 void add_chunk_to_free_list(OopChunk* elem);
207
208 OopChunk* remove_chunk_from_chunk_list();
209 OopChunk* remove_chunk_from_free_list();
210
211 bool _should_expand;
212
213 // Resizes the mark stack to the given new capacity. Releases any previous
214 // memory if successful.
215 bool resize(size_t new_capacity);
216
217 public:
218 G1CMMarkStack();
219 ~G1CMMarkStack();
220
221 // Alignment and minimum capacity of this mark stack in number of oops.
222 static size_t capacity_alignment();
223
224 // Allocate and initialize the mark stack with the given number of oops.
225 bool initialize(size_t initial_capacity, size_t max_capacity);
226
227 // Pushes the given buffer containing at most OopsPerChunk elements on the mark
228 // stack. If less than OopsPerChunk elements are to be pushed, the array must
229 // be terminated with a NULL.
230 // Returns whether the buffer contents were successfully pushed to the global mark
231 // stack.
232 bool par_push_chunk(oop* buffer);
233
234 // Pops a chunk from this mark stack, copying them into the given buffer. This
235 // chunk may contain up to OopsPerChunk elements. If there are less, the last
236 // element in the array is a NULL pointer.
237 bool par_pop_chunk(oop* buffer);
238
239 // Return whether the chunk list is empty. Racy due to unsynchronized access to
240 // _chunk_list.
241 bool is_empty() const { return _chunk_list == NULL; }
242
243 size_t capacity() const { return _chunk_capacity; }
244
245 bool is_out_of_memory() const { return _out_of_memory; }
246 void clear_out_of_memory() { _out_of_memory = false; }
247
248 bool should_expand() const { return _should_expand; }
249 void set_should_expand(bool value) { _should_expand = value; }
250
251 // Expand the stack, typically in response to an overflow condition
252 void expand();
253
254 // Return the approximate number of oops on this mark stack. Racy due to
255 // unsynchronized access to _chunks_in_chunk_list.
256 size_t size() const { return _chunks_in_chunk_list * OopsPerChunk; }
257
258 void set_empty();
259
260 // Apply Fn to every oop on the mark stack. The mark stack must not
261 // be modified while iterating.
262 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
263 };
264
265 // Root Regions are regions that are not empty at the beginning of a
266 // marking cycle and which we might collect during an evacuation pause
267 // while the cycle is active. Given that, during evacuation pauses, we
268 // do not copy objects that are explicitly marked, what we have to do
269 // for the root regions is to scan them and mark all objects reachable
270 // from them. According to the SATB assumptions, we only need to visit
271 // each object once during marking. So, as long as we finish this scan
272 // before the next evacuation pause, we can copy the objects from the
273 // root regions without having to mark them or do anything else to them.
274 //
275 // Currently, we only support root region scanning once (at the start
276 // of the marking cycle) and the root regions are all the survivor
277 // regions populated during the initial-mark pause.
278 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC {
279 private:
280 const G1SurvivorRegions* _survivors;
281 G1ConcurrentMark* _cm;
282
283 volatile bool _scan_in_progress;
284 volatile bool _should_abort;
285 volatile int _claimed_survivor_index;
286
287 void notify_scan_done();
288
289 public:
290 G1CMRootRegions();
291 // We actually do most of the initialization in this method.
292 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm);
293
294 // Reset the claiming / scanning of the root regions.
295 void prepare_for_scan();
296
297 // Forces get_next() to return NULL so that the iteration aborts early.
298 void abort() { _should_abort = true; }
299
300 // Return true if the CM thread are actively scanning root regions,
301 // false otherwise.
302 bool scan_in_progress() { return _scan_in_progress; }
303
304 // Claim the next root region to scan atomically, or return NULL if
305 // all have been claimed.
306 HeapRegion* claim_next();
307
308 // The number of root regions to scan.
309 uint num_root_regions() const;
310
311 void cancel_scan();
312
313 // Flag that we're done with root region scanning and notify anyone
314 // who's waiting on it. If aborted is false, assume that all regions
315 // have been claimed.
316 void scan_finished();
317
318 // If CM threads are still scanning root regions, wait until they
319 // are done. Return true if we had to wait, false otherwise.
320 bool wait_until_scan_finished();
321 };
322
323 class ConcurrentMarkThread;
324
325 class G1ConcurrentMark: public CHeapObj<mtGC> {
326 friend class ConcurrentMarkThread;
327 friend class G1ParNoteEndTask;
328 friend class G1VerifyLiveDataClosure;
329 friend class G1CMRefProcTaskProxy;
330 friend class G1CMRefProcTaskExecutor;
331 friend class G1CMKeepAliveAndDrainClosure;
332 friend class G1CMDrainMarkingStackClosure;
333 friend class G1CMBitMapClosure;
334 friend class G1CMConcurrentMarkingTask;
335 friend class G1CMRemarkTask;
336 friend class G1CMTask;
337
338 protected:
339 ConcurrentMarkThread* _cmThread; // The thread doing the work
340 G1CollectedHeap* _g1h; // The heap
341 uint _parallel_marking_threads; // The number of marking
342 // threads we're using
343 uint _max_parallel_marking_threads; // Max number of marking
344 // threads we'll ever use
345 double _sleep_factor; // How much we have to sleep, with
346 // respect to the work we just did, to
347 // meet the marking overhead goal
348 double _marking_task_overhead; // Marking target overhead for
349 // a single task
350
351 FreeRegionList _cleanup_list;
352
353 // Concurrent marking support structures
354 G1CMBitMap _markBitMap1;
355 G1CMBitMap _markBitMap2;
356 G1CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap
357 G1CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
358
359 // Heap bounds
360 HeapWord* _heap_start;
361 HeapWord* _heap_end;
362
363 // Root region tracking and claiming
364 G1CMRootRegions _root_regions;
365
366 // For gray objects
367 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
368 HeapWord* volatile _finger; // The global finger, region aligned,
369 // always points to the end of the
370 // last claimed region
371
372 // Marking tasks
373 uint _max_worker_id;// Maximum worker id
374 uint _active_tasks; // Task num currently active
375 G1CMTask** _tasks; // Task queue array (max_worker_id len)
376 G1CMTaskQueueSet* _task_queues; // Task queue set
377 ParallelTaskTerminator _terminator; // For termination
378
379 // Two sync barriers that are used to synchronize tasks when an
380 // overflow occurs. The algorithm is the following. All tasks enter
381 // the first one to ensure that they have all stopped manipulating
382 // the global data structures. After they exit it, they re-initialize
383 // their data structures and task 0 re-initializes the global data
384 // structures. Then, they enter the second sync barrier. This
385 // ensure, that no task starts doing work before all data
386 // structures (local and global) have been re-initialized. When they
387 // exit it, they are free to start working again.
388 WorkGangBarrierSync _first_overflow_barrier_sync;
389 WorkGangBarrierSync _second_overflow_barrier_sync;
390
391 // True: marking is concurrent, false: we're in remark
392 volatile bool _concurrent;
393 // Set at the end of a Full GC so that marking aborts
394 volatile bool _has_aborted;
395
396 // Used when remark aborts due to an overflow to indicate that
397 // another concurrent marking phase should start
398 volatile bool _restart_for_overflow;
399
400 // This is true from the very start of concurrent marking until the
401 // point when all the tasks complete their work. It is really used
402 // to determine the points between the end of concurrent marking and
403 // time of remark.
404 volatile bool _concurrent_marking_in_progress;
405
406 ConcurrentGCTimer* _gc_timer_cm;
407
408 G1OldTracer* _gc_tracer_cm;
409
410 // All of these times are in ms
411 NumberSeq _init_times;
412 NumberSeq _remark_times;
413 NumberSeq _remark_mark_times;
414 NumberSeq _remark_weak_ref_times;
415 NumberSeq _cleanup_times;
416 double _total_counting_time;
417 double _total_rs_scrub_time;
418
419 double* _accum_task_vtime; // Accumulated task vtime
420
421 WorkGang* _parallel_workers;
422
423 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
424 void weakRefsWork(bool clear_all_soft_refs);
425
426 void swapMarkBitMaps();
427
428 // It resets the global marking data structures, as well as the
429 // task local ones; should be called during initial mark.
430 void reset();
431
432 // Resets all the marking data structures. Called when we have to restart
433 // marking or when marking completes (via set_non_marking_state below).
434 void reset_marking_state();
435
436 // We do this after we're done with marking so that the marking data
437 // structures are initialized to a sensible and predictable state.
438 void set_non_marking_state();
439
440 // Called to indicate how many threads are currently active.
441 void set_concurrency(uint active_tasks);
442
443 // It should be called to indicate which phase we're in (concurrent
444 // mark or remark) and how many threads are currently active.
445 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
446
447 // Prints all gathered CM-related statistics
448 void print_stats();
449
450 bool cleanup_list_is_empty() {
451 return _cleanup_list.is_empty();
452 }
453
454 // Accessor methods
455 uint parallel_marking_threads() const { return _parallel_marking_threads; }
456 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
457 double sleep_factor() { return _sleep_factor; }
458 double marking_task_overhead() { return _marking_task_overhead;}
459
460 HeapWord* finger() { return _finger; }
461 bool concurrent() { return _concurrent; }
462 uint active_tasks() { return _active_tasks; }
463 ParallelTaskTerminator* terminator() { return &_terminator; }
464
465 // It claims the next available region to be scanned by a marking
466 // task/thread. It might return NULL if the next region is empty or
467 // we have run out of regions. In the latter case, out_of_regions()
468 // determines whether we've really run out of regions or the task
469 // should call claim_region() again. This might seem a bit
470 // awkward. Originally, the code was written so that claim_region()
471 // either successfully returned with a non-empty region or there
472 // were no more regions to be claimed. The problem with this was
473 // that, in certain circumstances, it iterated over large chunks of
474 // the heap finding only empty regions and, while it was working, it
475 // was preventing the calling task to call its regular clock
476 // method. So, this way, each task will spend very little time in
477 // claim_region() and is allowed to call the regular clock method
478 // frequently.
479 HeapRegion* claim_region(uint worker_id);
480
481 // It determines whether we've run out of regions to scan. Note that
482 // the finger can point past the heap end in case the heap was expanded
483 // to satisfy an allocation without doing a GC. This is fine, because all
484 // objects in those regions will be considered live anyway because of
485 // SATB guarantees (i.e. their TAMS will be equal to bottom).
486 bool out_of_regions() { return _finger >= _heap_end; }
487
488 // Returns the task with the given id
489 G1CMTask* task(int id) {
490 assert(0 <= id && id < (int) _active_tasks,
491 "task id not within active bounds");
492 return _tasks[id];
493 }
494
495 // Returns the task queue with the given id
496 G1CMTaskQueue* task_queue(int id) {
497 assert(0 <= id && id < (int) _active_tasks,
498 "task queue id not within active bounds");
499 return (G1CMTaskQueue*) _task_queues->queue(id);
500 }
501
502 // Returns the task queue set
503 G1CMTaskQueueSet* task_queues() { return _task_queues; }
504
505 // Access / manipulation of the overflow flag which is set to
506 // indicate that the global stack has overflown
507 bool has_overflown() { return _global_mark_stack.is_out_of_memory(); }
508 void clear_has_overflown() { _global_mark_stack.clear_out_of_memory(); }
509 bool restart_for_overflow() { return _restart_for_overflow; }
510
511 // Methods to enter the two overflow sync barriers
512 void enter_first_sync_barrier(uint worker_id);
513 void enter_second_sync_barrier(uint worker_id);
514
515 // Card index of the bottom of the G1 heap. Used for biasing indices into
516 // the card bitmaps.
517 intptr_t _heap_bottom_card_num;
518
519 // Set to true when initialization is complete
520 bool _completed_initialization;
521
522 // end_timer, true to end gc timer after ending concurrent phase.
523 void register_concurrent_phase_end_common(bool end_timer);
524
525 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
526 // true, periodically insert checks to see if this method should exit prematurely.
527 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
528 public:
529 // Manipulation of the global mark stack.
530 // The push and pop operations are used by tasks for transfers
531 // between task-local queues and the global mark stack.
532 bool mark_stack_push(oop* arr) {
533 return _global_mark_stack.par_push_chunk(arr);
534 }
535 bool mark_stack_pop(oop* arr) {
536 return _global_mark_stack.par_pop_chunk(arr);
537 }
538 size_t mark_stack_size() { return _global_mark_stack.size(); }
539 size_t partial_mark_stack_size_target() { return _global_mark_stack.capacity()/3; }
540 bool mark_stack_empty() { return _global_mark_stack.is_empty(); }
541
542 G1CMRootRegions* root_regions() { return &_root_regions; }
543
544 bool concurrent_marking_in_progress() {
545 return _concurrent_marking_in_progress;
546 }
547 void set_concurrent_marking_in_progress() {
548 _concurrent_marking_in_progress = true;
549 }
550 void clear_concurrent_marking_in_progress() {
551 _concurrent_marking_in_progress = false;
552 }
553
554 void concurrent_cycle_start();
555 void concurrent_cycle_end();
556
557 void update_accum_task_vtime(int i, double vtime) {
558 _accum_task_vtime[i] += vtime;
559 }
560
561 double all_task_accum_vtime() {
562 double ret = 0.0;
563 for (uint i = 0; i < _max_worker_id; ++i)
564 ret += _accum_task_vtime[i];
565 return ret;
566 }
567
568 // Attempts to steal an object from the task queues of other tasks
569 bool try_stealing(uint worker_id, int* hash_seed, oop& obj);
570
571 G1ConcurrentMark(G1CollectedHeap* g1h,
572 G1RegionToSpaceMapper* prev_bitmap_storage,
573 G1RegionToSpaceMapper* next_bitmap_storage);
574 ~G1ConcurrentMark();
575
576 ConcurrentMarkThread* cmThread() { return _cmThread; }
577
578 G1CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
579 G1CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
580
581 // Returns the number of GC threads to be used in a concurrent
582 // phase based on the number of GC threads being used in a STW
583 // phase.
584 uint scale_parallel_threads(uint n_par_threads);
585
586 // Calculates the number of GC threads to be used in a concurrent phase.
587 uint calc_parallel_marking_threads();
588
589 // The following three are interaction between CM and
590 // G1CollectedHeap
591
592 // This notifies CM that a root during initial-mark needs to be
593 // grayed. It is MT-safe. hr is the region that
594 // contains the object and it's passed optionally from callers who
595 // might already have it (no point in recalculating it).
596 inline void grayRoot(oop obj,
597 HeapRegion* hr = NULL);
598
599 // Prepare internal data structures for the next mark cycle. This includes clearing
600 // the next mark bitmap and some internal data structures. This method is intended
601 // to be called concurrently to the mutator. It will yield to safepoint requests.
602 void cleanup_for_next_mark();
603
604 // Clear the previous marking bitmap during safepoint.
605 void clear_prev_bitmap(WorkGang* workers);
606
607 // Return whether the next mark bitmap has no marks set. To be used for assertions
608 // only. Will not yield to pause requests.
609 bool nextMarkBitmapIsClear();
610
611 // These two do the work that needs to be done before and after the
612 // initial root checkpoint. Since this checkpoint can be done at two
613 // different points (i.e. an explicit pause or piggy-backed on a
614 // young collection), then it's nice to be able to easily share the
615 // pre/post code. It might be the case that we can put everything in
616 // the post method. TP
617 void checkpointRootsInitialPre();
618 void checkpointRootsInitialPost();
619
620 // Scan all the root regions and mark everything reachable from
621 // them.
622 void scan_root_regions();
623
624 // Scan a single root region and mark everything reachable from it.
625 void scanRootRegion(HeapRegion* hr);
626
627 // Do concurrent phase of marking, to a tentative transitive closure.
628 void mark_from_roots();
629
630 void checkpointRootsFinal(bool clear_all_soft_refs);
631 void checkpointRootsFinalWork();
632 void cleanup();
633 void complete_cleanup();
634
635 // Mark in the previous bitmap. NB: this is usually read-only, so use
636 // this carefully!
637 inline void markPrev(oop p);
638
639 // Clears marks for all objects in the given range, for the prev or
640 // next bitmaps. NB: the previous bitmap is usually
641 // read-only, so use this carefully!
642 void clearRangePrevBitmap(MemRegion mr);
643
644 // Verify that there are no CSet oops on the stacks (taskqueues /
645 // global mark stack) and fingers (global / per-task).
646 // If marking is not in progress, it's a no-op.
647 void verify_no_cset_oops() PRODUCT_RETURN;
648
649 inline bool isPrevMarked(oop p) const;
650
651 inline bool do_yield_check();
652
653 // Abandon current marking iteration due to a Full GC.
654 void abort();
655
656 bool has_aborted() { return _has_aborted; }
657
658 void print_summary_info();
659
660 void print_worker_threads_on(outputStream* st) const;
661 void threads_do(ThreadClosure* tc) const;
662
663 void print_on_error(outputStream* st) const;
664
665 // Attempts to mark the given object on the next mark bitmap.
666 inline bool par_mark(oop obj);
667
668 // Returns true if initialization was successfully completed.
669 bool completed_initialization() const {
670 return _completed_initialization;
671 }
672
673 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
674 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
675
676 private:
677 // Clear (Reset) all liveness count data.
678 void clear_live_data(WorkGang* workers);
679
680 #ifdef ASSERT
681 // Verify all of the above data structures that they are in initial state.
682 void verify_live_data_clear();
683 #endif
684
685 // Aggregates the per-card liveness data based on the current marking. Also sets
686 // the amount of marked bytes for each region.
687 void create_live_data();
688
689 void finalize_live_data();
690
691 void verify_live_data();
692 };
693
694 // A class representing a marking task.
695 class G1CMTask : public TerminatorTerminator {
696 private:
697 enum PrivateConstants {
698 // The regular clock call is called once the scanned words reaches
699 // this limit
700 words_scanned_period = 12*1024,
701 // The regular clock call is called once the number of visited
702 // references reaches this limit
703 refs_reached_period = 1024,
704 // Initial value for the hash seed, used in the work stealing code
705 init_hash_seed = 17
706 };
707
708 G1CMObjArrayProcessor _objArray_processor;
709
710 uint _worker_id;
711 G1CollectedHeap* _g1h;
712 G1ConcurrentMark* _cm;
713 G1CMBitMap* _nextMarkBitMap;
714 // the task queue of this task
715 G1CMTaskQueue* _task_queue;
716 private:
717 // the task queue set---needed for stealing
718 G1CMTaskQueueSet* _task_queues;
719 // indicates whether the task has been claimed---this is only for
720 // debugging purposes
721 bool _claimed;
722
723 // number of calls to this task
724 int _calls;
725
726 // when the virtual timer reaches this time, the marking step should
727 // exit
728 double _time_target_ms;
729 // the start time of the current marking step
730 double _start_time_ms;
731
732 // the oop closure used for iterations over oops
733 G1CMOopClosure* _cm_oop_closure;
734
735 // the region this task is scanning, NULL if we're not scanning any
736 HeapRegion* _curr_region;
737 // the local finger of this task, NULL if we're not scanning a region
738 HeapWord* _finger;
739 // limit of the region this task is scanning, NULL if we're not scanning one
740 HeapWord* _region_limit;
741
742 // the number of words this task has scanned
743 size_t _words_scanned;
744 // When _words_scanned reaches this limit, the regular clock is
745 // called. Notice that this might be decreased under certain
746 // circumstances (i.e. when we believe that we did an expensive
747 // operation).
748 size_t _words_scanned_limit;
749 // the initial value of _words_scanned_limit (i.e. what it was
750 // before it was decreased).
751 size_t _real_words_scanned_limit;
752
753 // the number of references this task has visited
754 size_t _refs_reached;
755 // When _refs_reached reaches this limit, the regular clock is
756 // called. Notice this this might be decreased under certain
757 // circumstances (i.e. when we believe that we did an expensive
758 // operation).
759 size_t _refs_reached_limit;
760 // the initial value of _refs_reached_limit (i.e. what it was before
761 // it was decreased).
762 size_t _real_refs_reached_limit;
763
764 // used by the work stealing stuff
765 int _hash_seed;
766 // if this is true, then the task has aborted for some reason
767 bool _has_aborted;
768 // set when the task aborts because it has met its time quota
769 bool _has_timed_out;
770 // true when we're draining SATB buffers; this avoids the task
771 // aborting due to SATB buffers being available (as we're already
772 // dealing with them)
773 bool _draining_satb_buffers;
774
775 // number sequence of past step times
776 NumberSeq _step_times_ms;
777 // elapsed time of this task
778 double _elapsed_time_ms;
779 // termination time of this task
780 double _termination_time_ms;
781 // when this task got into the termination protocol
782 double _termination_start_time_ms;
783
784 // true when the task is during a concurrent phase, false when it is
785 // in the remark phase (so, in the latter case, we do not have to
786 // check all the things that we have to check during the concurrent
787 // phase, i.e. SATB buffer availability...)
788 bool _concurrent;
789
790 TruncatedSeq _marking_step_diffs_ms;
791
792 // it updates the local fields after this task has claimed
793 // a new region to scan
794 void setup_for_region(HeapRegion* hr);
795 // it brings up-to-date the limit of the region
796 void update_region_limit();
797
798 // called when either the words scanned or the refs visited limit
799 // has been reached
800 void reached_limit();
801 // recalculates the words scanned and refs visited limits
802 void recalculate_limits();
803 // decreases the words scanned and refs visited limits when we reach
804 // an expensive operation
805 void decrease_limits();
806 // it checks whether the words scanned or refs visited reached their
807 // respective limit and calls reached_limit() if they have
808 void check_limits() {
809 if (_words_scanned >= _words_scanned_limit ||
810 _refs_reached >= _refs_reached_limit) {
811 reached_limit();
812 }
813 }
814 // this is supposed to be called regularly during a marking step as
815 // it checks a bunch of conditions that might cause the marking step
816 // to abort
817 void regular_clock_call();
818 bool concurrent() { return _concurrent; }
819
820 // Test whether obj might have already been passed over by the
821 // mark bitmap scan, and so needs to be pushed onto the mark stack.
822 bool is_below_finger(oop obj, HeapWord* global_finger) const;
823
824 template<bool scan> void process_grey_object(oop obj);
825 public:
826 // Apply the closure on the given area of the objArray. Return the number of words
827 // scanned.
828 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
829 // It resets the task; it should be called right at the beginning of
830 // a marking phase.
831 void reset(G1CMBitMap* _nextMarkBitMap);
832 // it clears all the fields that correspond to a claimed region.
833 void clear_region_fields();
834
835 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
836
837 // The main method of this class which performs a marking step
838 // trying not to exceed the given duration. However, it might exit
839 // prematurely, according to some conditions (i.e. SATB buffers are
840 // available for processing).
841 void do_marking_step(double target_ms,
842 bool do_termination,
843 bool is_serial);
844
845 // These two calls start and stop the timer
846 void record_start_time() {
847 _elapsed_time_ms = os::elapsedTime() * 1000.0;
848 }
849 void record_end_time() {
850 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
851 }
852
853 // returns the worker ID associated with this task.
854 uint worker_id() { return _worker_id; }
855
856 // From TerminatorTerminator. It determines whether this task should
857 // exit the termination protocol after it's entered it.
858 virtual bool should_exit_termination();
859
860 // Resets the local region fields after a task has finished scanning a
861 // region; or when they have become stale as a result of the region
862 // being evacuated.
863 void giveup_current_region();
864
865 HeapWord* finger() { return _finger; }
866
867 bool has_aborted() { return _has_aborted; }
868 void set_has_aborted() { _has_aborted = true; }
869 void clear_has_aborted() { _has_aborted = false; }
870 bool has_timed_out() { return _has_timed_out; }
871 bool claimed() { return _claimed; }
872
873 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
874
875 // Increment the number of references this task has visited.
876 void increment_refs_reached() { ++_refs_reached; }
877
878 // Grey the object by marking it. If not already marked, push it on
879 // the local queue if below the finger.
880 // obj is below its region's NTAMS.
881 inline void make_reference_grey(oop obj);
882
883 // Grey the object (by calling make_grey_reference) if required,
884 // e.g. obj is below its containing region's NTAMS.
885 // Precondition: obj is a valid heap object.
886 inline void deal_with_reference(oop obj);
887
888 // It scans an object and visits its children.
889 inline void scan_object(oop obj);
890
891 // It pushes an object on the local queue.
892 inline void push(oop obj);
893
894 // Move entries to the global stack.
895 void move_entries_to_global_stack();
896 // Move entries from the global stack, return true if we were successful to do so.
897 bool get_entries_from_global_stack();
898
899 // It pops and scans objects from the local queue. If partially is
900 // true, then it stops when the queue size is of a given limit. If
901 // partially is false, then it stops when the queue is empty.
902 void drain_local_queue(bool partially);
903 // It moves entries from the global stack to the local queue and
904 // drains the local queue. If partially is true, then it stops when
905 // both the global stack and the local queue reach a given size. If
906 // partially if false, it tries to empty them totally.
907 void drain_global_stack(bool partially);
908 // It keeps picking SATB buffers and processing them until no SATB
909 // buffers are available.
910 void drain_satb_buffers();
911
912 // moves the local finger to a new location
913 inline void move_finger_to(HeapWord* new_finger) {
914 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
915 _finger = new_finger;
916 }
917
918 G1CMTask(uint worker_id,
919 G1ConcurrentMark *cm,
920 G1CMTaskQueue* task_queue,
921 G1CMTaskQueueSet* task_queues);
922
923 // it prints statistics associated with this task
924 void print_stats();
925 };
926
927 // Class that's used to to print out per-region liveness
928 // information. It's currently used at the end of marking and also
929 // after we sort the old regions at the end of the cleanup operation.
930 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
931 private:
932 // Accumulators for these values.
933 size_t _total_used_bytes;
934 size_t _total_capacity_bytes;
935 size_t _total_prev_live_bytes;
936 size_t _total_next_live_bytes;
937
938 // Accumulator for the remembered set size
939 size_t _total_remset_bytes;
940
941 // Accumulator for strong code roots memory size
942 size_t _total_strong_code_roots_bytes;
943
944 static double perc(size_t val, size_t total) {
945 if (total == 0) {
946 return 0.0;
947 } else {
948 return 100.0 * ((double) val / (double) total);
949 }
950 }
951
952 static double bytes_to_mb(size_t val) {
953 return (double) val / (double) M;
954 }
955
956 public:
957 // The header and footer are printed in the constructor and
958 // destructor respectively.
959 G1PrintRegionLivenessInfoClosure(const char* phase_name);
960 virtual bool doHeapRegion(HeapRegion* r);
961 ~G1PrintRegionLivenessInfoClosure();
962 };
963
964 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP