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.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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
42 // This is a container class for either an oop or a continuation address for
43 // mark stack entries. Both are pushed onto the mark stack.
44 class G1TaskQueueEntry VALUE_OBJ_CLASS_SPEC {
45 private:
46 void* _holder;
47
48 static const uintptr_t ArraySliceBit = 1;
49
50 G1TaskQueueEntry(oop obj) : _holder(obj) {
51 assert(_holder != NULL, "Not allowed to set NULL task queue element");
52 }
53 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { }
54 public:
55 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; }
56 G1TaskQueueEntry() : _holder(NULL) { }
57
58 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); }
59 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); }
60
61 void assign(const G1TaskQueueEntry& t) {
62 _holder = t._holder;
63 }
64
65 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile {
66 _holder = t._holder;
67 return *this;
68 }
69
70 oop obj() const {
71 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder));
72 return (oop)_holder;
73 }
74
75 HeapWord* slice() const {
76 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder));
77 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit);
78 }
79
80 bool is_oop() const { return !is_array_slice(); }
81 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; }
82 bool is_null() const { return _holder == NULL; }
83 };
84
85 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue;
86 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
87
88 // Closure used by CM during concurrent reference discovery
89 // and reference processing (during remarking) to determine
90 // if a particular object is alive. It is primarily used
91 // to determine if referents of discovered reference objects
92 // are alive. An instance is also embedded into the
93 // reference processor as the _is_alive_non_header field
94 class G1CMIsAliveClosure: public BoolObjectClosure {
95 G1CollectedHeap* _g1;
96 public:
97 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
98
99 bool do_object_b(oop obj);
100 };
101
102 // A generic CM bit map. This is essentially a wrapper around the BitMap
103 // class, with one bit per (1<<_shifter) HeapWords.
104
105 class G1CMBitMapRO VALUE_OBJ_CLASS_SPEC {
106 protected:
107 HeapWord* _bmStartWord; // base address of range covered by map
108 size_t _bmWordSize; // map size (in #HeapWords covered)
109 const int _shifter; // map to char or bit
110 BitMapView _bm; // the bit map itself
111
112 public:
113 // constructor
114 G1CMBitMapRO(int shifter);
115
116 // inquiries
117 HeapWord* startWord() const { return _bmStartWord; }
118 // the following is one past the last word in space
119 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
120
121 // read marks
122
123 bool isMarked(HeapWord* addr) const {
124 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
125 "outside underlying space?");
126 return _bm.at(heapWordToOffset(addr));
127 }
128
129 // iteration
130 inline bool iterate(BitMapClosure* cl, MemRegion mr);
131
132 // Return the address corresponding to the next marked bit at or after
133 // "addr", and before "limit", if "limit" is non-NULL. If there is no
134 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
135 HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
136 const HeapWord* limit = NULL) const;
137
138 // conversion utilities
139 HeapWord* offsetToHeapWord(size_t offset) const {
140 return _bmStartWord + (offset << _shifter);
141 }
142 size_t heapWordToOffset(const HeapWord* addr) const {
143 return pointer_delta(addr, _bmStartWord) >> _shifter;
144 }
145
146 // The argument addr should be the start address of a valid object
147 inline HeapWord* nextObject(HeapWord* addr);
148
149 void print_on_error(outputStream* st, const char* prefix) const;
150
151 // debugging
152 NOT_PRODUCT(bool covers(MemRegion rs) const;)
153 };
154
155 class G1CMBitMapMappingChangedListener : public G1MappingChangedListener {
156 private:
157 G1CMBitMap* _bm;
158 public:
159 G1CMBitMapMappingChangedListener() : _bm(NULL) {}
160
161 void set_bitmap(G1CMBitMap* bm) { _bm = bm; }
162
163 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
164 };
165
166 class G1CMBitMap : public G1CMBitMapRO {
167 private:
168 G1CMBitMapMappingChangedListener _listener;
169
170 public:
171 static size_t compute_size(size_t heap_size);
172 // Returns the amount of bytes on the heap between two marks in the bitmap.
173 static size_t mark_distance();
174 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
175 // mark bitmap corresponds to. This is the same as the mark distance above.
176 static size_t heap_map_factor() {
177 return mark_distance();
178 }
179
180 G1CMBitMap() : G1CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
181
182 // Initializes the underlying BitMap to cover the given area.
183 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
184
185 // Write marks.
186 inline void mark(HeapWord* addr);
187 inline void clear(HeapWord* addr);
188 inline bool parMark(HeapWord* addr);
189
190 void clear_range(MemRegion mr);
191 };
192
193 // Represents the overflow mark stack used by concurrent marking.
194 //
195 // Stores oops in a huge buffer in virtual memory that is always fully committed.
196 // Resizing may only happen during a STW pause when the stack is empty.
197 //
198 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
199 // stack memory is split into evenly sized chunks of oops. Users can only
200 // add or remove entries on that basis.
201 // Chunks are filled in increasing address order. Not completely filled chunks
202 // have a NULL element as a terminating element.
203 //
204 // Every chunk has a header containing a single pointer element used for memory
205 // management. This wastes some space, but is negligible (< .1% with current sizing).
206 //
207 // Memory management is done using a mix of tracking a high water-mark indicating
208 // that all chunks at a lower address are valid chunks, and a singly linked free
209 // list connecting all empty chunks.
210 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC {
211 public:
212 // Number of oops that can fit in a single chunk.
213 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */;
214 private:
215 struct TaskQueueEntryChunk {
216 TaskQueueEntryChunk* next;
217 G1TaskQueueEntry data[EntriesPerChunk];
218 };
219
220 size_t _max_chunk_capacity; // Maximum number of OopChunk elements on the stack.
221
222 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area.
223 size_t _chunk_capacity; // Current maximum number of OopChunk elements.
224
225 char _pad0[DEFAULT_CACHE_LINE_SIZE];
226 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
227 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)];
228 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data.
229 volatile size_t _chunks_in_chunk_list;
230 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)];
231
232 volatile size_t _hwm; // High water mark within the reserved space.
233 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
234
235 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
236 // NULL if out of memory.
237 TaskQueueEntryChunk* allocate_new_chunk();
238
239 volatile bool _out_of_memory;
240
241 // Atomically add the given chunk to the list.
242 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem);
243 // Atomically remove and return a chunk from the given list. Returns NULL if the
244 // list is empty.
245 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list);
246
247 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem);
248 void add_chunk_to_free_list(TaskQueueEntryChunk* elem);
249
250 TaskQueueEntryChunk* remove_chunk_from_chunk_list();
251 TaskQueueEntryChunk* remove_chunk_from_free_list();
252
253 bool _should_expand;
254
255 // Resizes the mark stack to the given new capacity. Releases any previous
256 // memory if successful.
257 bool resize(size_t new_capacity);
258
259 public:
260 G1CMMarkStack();
261 ~G1CMMarkStack();
262
263 // Alignment and minimum capacity of this mark stack in number of oops.
264 static size_t capacity_alignment();
265
266 // Allocate and initialize the mark stack with the given number of oops.
267 bool initialize(size_t initial_capacity, size_t max_capacity);
268
269 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark
270 // stack. If less than EntriesPerChunk elements are to be pushed, the array must
271 // be terminated with a NULL.
272 // Returns whether the buffer contents were successfully pushed to the global mark
273 // stack.
274 bool par_push_chunk(G1TaskQueueEntry* buffer);
275
276 // Pops a chunk from this mark stack, copying them into the given buffer. This
277 // chunk may contain up to EntriesPerChunk elements. If there are less, the last
278 // element in the array is a NULL pointer.
279 bool par_pop_chunk(G1TaskQueueEntry* buffer);
280
281 // Return whether the chunk list is empty. Racy due to unsynchronized access to
282 // _chunk_list.
283 bool is_empty() const { return _chunk_list == NULL; }
284
285 size_t capacity() const { return _chunk_capacity; }
286
287 bool is_out_of_memory() const { return _out_of_memory; }
288 void clear_out_of_memory() { _out_of_memory = false; }
289
290 bool should_expand() const { return _should_expand; }
291 void set_should_expand(bool value) { _should_expand = value; }
292
293 // Expand the stack, typically in response to an overflow condition
294 void expand();
295
296 // Return the approximate number of oops on this mark stack. Racy due to
297 // unsynchronized access to _chunks_in_chunk_list.
298 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; }
299
300 void set_empty();
301
302 // Apply Fn to every oop on the mark stack. The mark stack must not
303 // be modified while iterating.
304 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
305 };
306
307 // Root Regions are regions that are not empty at the beginning of a
308 // marking cycle and which we might collect during an evacuation pause
309 // while the cycle is active. Given that, during evacuation pauses, we
310 // do not copy objects that are explicitly marked, what we have to do
311 // for the root regions is to scan them and mark all objects reachable
312 // from them. According to the SATB assumptions, we only need to visit
313 // each object once during marking. So, as long as we finish this scan
314 // before the next evacuation pause, we can copy the objects from the
315 // root regions without having to mark them or do anything else to them.
316 //
317 // Currently, we only support root region scanning once (at the start
318 // of the marking cycle) and the root regions are all the survivor
319 // regions populated during the initial-mark pause.
320 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC {
321 private:
322 const G1SurvivorRegions* _survivors;
323 G1ConcurrentMark* _cm;
324
325 volatile bool _scan_in_progress;
326 volatile bool _should_abort;
327 volatile int _claimed_survivor_index;
328
329 void notify_scan_done();
330
331 public:
332 G1CMRootRegions();
333 // We actually do most of the initialization in this method.
334 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm);
335
336 // Reset the claiming / scanning of the root regions.
337 void prepare_for_scan();
338
339 // Forces get_next() to return NULL so that the iteration aborts early.
340 void abort() { _should_abort = true; }
341
342 // Return true if the CM thread are actively scanning root regions,
343 // false otherwise.
344 bool scan_in_progress() { return _scan_in_progress; }
345
346 // Claim the next root region to scan atomically, or return NULL if
347 // all have been claimed.
348 HeapRegion* claim_next();
349
350 // The number of root regions to scan.
351 uint num_root_regions() const;
352
353 void cancel_scan();
354
355 // Flag that we're done with root region scanning and notify anyone
356 // who's waiting on it. If aborted is false, assume that all regions
357 // have been claimed.
358 void scan_finished();
359
360 // If CM threads are still scanning root regions, wait until they
361 // are done. Return true if we had to wait, false otherwise.
362 bool wait_until_scan_finished();
363 };
364
365 class ConcurrentMarkThread;
366
367 class G1ConcurrentMark: public CHeapObj<mtGC> {
368 friend class ConcurrentMarkThread;
369 friend class G1ParNoteEndTask;
370 friend class G1VerifyLiveDataClosure;
371 friend class G1CMRefProcTaskProxy;
372 friend class G1CMRefProcTaskExecutor;
373 friend class G1CMKeepAliveAndDrainClosure;
374 friend class G1CMDrainMarkingStackClosure;
375 friend class G1CMBitMapClosure;
376 friend class G1CMConcurrentMarkingTask;
377 friend class G1CMRemarkTask;
378 friend class G1CMTask;
379
380 protected:
381 ConcurrentMarkThread* _cmThread; // The thread doing the work
382 G1CollectedHeap* _g1h; // The heap
383 uint _parallel_marking_threads; // The number of marking
384 // threads we're using
385 uint _max_parallel_marking_threads; // Max number of marking
386 // threads we'll ever use
387 double _sleep_factor; // How much we have to sleep, with
388 // respect to the work we just did, to
389 // meet the marking overhead goal
390 double _marking_task_overhead; // Marking target overhead for
391 // a single task
392
393 FreeRegionList _cleanup_list;
394
395 // Concurrent marking support structures
396 G1CMBitMap _markBitMap1;
397 G1CMBitMap _markBitMap2;
398 G1CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap
399 G1CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
400
401 // Heap bounds
402 HeapWord* _heap_start;
403 HeapWord* _heap_end;
404
405 // Root region tracking and claiming
406 G1CMRootRegions _root_regions;
407
408 // For gray objects
409 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
410 HeapWord* volatile _finger; // The global finger, region aligned,
411 // always points to the end of the
412 // last claimed region
413
414 // Marking tasks
415 uint _max_worker_id;// Maximum worker id
416 uint _active_tasks; // Task num currently active
417 G1CMTask** _tasks; // Task queue array (max_worker_id len)
418 G1CMTaskQueueSet* _task_queues; // Task queue set
419 ParallelTaskTerminator _terminator; // For termination
420
421 // Two sync barriers that are used to synchronize tasks when an
422 // overflow occurs. The algorithm is the following. All tasks enter
423 // the first one to ensure that they have all stopped manipulating
424 // the global data structures. After they exit it, they re-initialize
425 // their data structures and task 0 re-initializes the global data
426 // structures. Then, they enter the second sync barrier. This
427 // ensure, that no task starts doing work before all data
428 // structures (local and global) have been re-initialized. When they
429 // exit it, they are free to start working again.
430 WorkGangBarrierSync _first_overflow_barrier_sync;
431 WorkGangBarrierSync _second_overflow_barrier_sync;
432
433 // This is set by any task, when an overflow on the global data
434 // structures is detected
435 volatile bool _has_overflown;
436 // True: marking is concurrent, false: we're in remark
437 volatile bool _concurrent;
438 // Set at the end of a Full GC so that marking aborts
439 volatile bool _has_aborted;
440
441 // Used when remark aborts due to an overflow to indicate that
442 // another concurrent marking phase should start
443 volatile bool _restart_for_overflow;
444
445 // This is true from the very start of concurrent marking until the
446 // point when all the tasks complete their work. It is really used
447 // to determine the points between the end of concurrent marking and
448 // time of remark.
449 volatile bool _concurrent_marking_in_progress;
450
451 ConcurrentGCTimer* _gc_timer_cm;
452
453 G1OldTracer* _gc_tracer_cm;
454
455 // All of these times are in ms
456 NumberSeq _init_times;
457 NumberSeq _remark_times;
458 NumberSeq _remark_mark_times;
459 NumberSeq _remark_weak_ref_times;
460 NumberSeq _cleanup_times;
461 double _total_counting_time;
462 double _total_rs_scrub_time;
463
464 double* _accum_task_vtime; // Accumulated task vtime
465
466 WorkGang* _parallel_workers;
467
468 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
469 void weakRefsWork(bool clear_all_soft_refs);
470
471 void swapMarkBitMaps();
472
473 // It resets the global marking data structures, as well as the
474 // task local ones; should be called during initial mark.
475 void reset();
476
477 // Resets all the marking data structures. Called when we have to restart
478 // marking or when marking completes (via set_non_marking_state below).
479 void reset_marking_state(bool clear_overflow = true);
480
481 // We do this after we're done with marking so that the marking data
482 // structures are initialized to a sensible and predictable state.
483 void set_non_marking_state();
484
485 // Called to indicate how many threads are currently active.
486 void set_concurrency(uint active_tasks);
487
488 // It should be called to indicate which phase we're in (concurrent
489 // mark or remark) and how many threads are currently active.
490 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
491
492 // Prints all gathered CM-related statistics
493 void print_stats();
494
495 bool cleanup_list_is_empty() {
496 return _cleanup_list.is_empty();
497 }
498
499 // Accessor methods
500 uint parallel_marking_threads() const { return _parallel_marking_threads; }
501 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
502 double sleep_factor() { return _sleep_factor; }
503 double marking_task_overhead() { return _marking_task_overhead;}
504
505 HeapWord* finger() { return _finger; }
506 bool concurrent() { return _concurrent; }
507 uint active_tasks() { return _active_tasks; }
508 ParallelTaskTerminator* terminator() { return &_terminator; }
509
510 // It claims the next available region to be scanned by a marking
511 // task/thread. It might return NULL if the next region is empty or
512 // we have run out of regions. In the latter case, out_of_regions()
513 // determines whether we've really run out of regions or the task
514 // should call claim_region() again. This might seem a bit
515 // awkward. Originally, the code was written so that claim_region()
516 // either successfully returned with a non-empty region or there
517 // were no more regions to be claimed. The problem with this was
518 // that, in certain circumstances, it iterated over large chunks of
519 // the heap finding only empty regions and, while it was working, it
520 // was preventing the calling task to call its regular clock
521 // method. So, this way, each task will spend very little time in
522 // claim_region() and is allowed to call the regular clock method
523 // frequently.
524 HeapRegion* claim_region(uint worker_id);
525
526 // It determines whether we've run out of regions to scan. Note that
527 // the finger can point past the heap end in case the heap was expanded
528 // to satisfy an allocation without doing a GC. This is fine, because all
529 // objects in those regions will be considered live anyway because of
530 // SATB guarantees (i.e. their TAMS will be equal to bottom).
531 bool out_of_regions() { return _finger >= _heap_end; }
532
533 // Returns the task with the given id
534 G1CMTask* task(int id) {
535 assert(0 <= id && id < (int) _active_tasks,
536 "task id not within active bounds");
537 return _tasks[id];
538 }
539
540 // Returns the task queue with the given id
541 G1CMTaskQueue* task_queue(int id) {
542 assert(0 <= id && id < (int) _active_tasks,
543 "task queue id not within active bounds");
544 return (G1CMTaskQueue*) _task_queues->queue(id);
545 }
546
547 // Returns the task queue set
548 G1CMTaskQueueSet* task_queues() { return _task_queues; }
549
550 // Access / manipulation of the overflow flag which is set to
551 // indicate that the global stack has overflown
552 bool has_overflown() { return _has_overflown; }
553 void set_has_overflown() { _has_overflown = true; }
554 void clear_has_overflown() { _has_overflown = false; }
555 bool restart_for_overflow() { return _restart_for_overflow; }
556
557 // Methods to enter the two overflow sync barriers
558 void enter_first_sync_barrier(uint worker_id);
559 void enter_second_sync_barrier(uint worker_id);
560
561 // Card index of the bottom of the G1 heap. Used for biasing indices into
562 // the card bitmaps.
563 intptr_t _heap_bottom_card_num;
564
565 // Set to true when initialization is complete
566 bool _completed_initialization;
567
568 // end_timer, true to end gc timer after ending concurrent phase.
569 void register_concurrent_phase_end_common(bool end_timer);
570
571 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
572 // true, periodically insert checks to see if this method should exit prematurely.
573 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
574 public:
575 // Manipulation of the global mark stack.
576 // The push and pop operations are used by tasks for transfers
577 // between task-local queues and the global mark stack.
578 bool mark_stack_push(G1TaskQueueEntry* arr) {
579 if (!_global_mark_stack.par_push_chunk(arr)) {
580 set_has_overflown();
581 return false;
582 }
583 return true;
584 }
585 bool mark_stack_pop(G1TaskQueueEntry* arr) {
586 return _global_mark_stack.par_pop_chunk(arr);
587 }
588 size_t mark_stack_size() { return _global_mark_stack.size(); }
589 size_t partial_mark_stack_size_target() { return _global_mark_stack.capacity()/3; }
590 bool mark_stack_overflow() { return _global_mark_stack.is_out_of_memory(); }
591 bool mark_stack_empty() { return _global_mark_stack.is_empty(); }
592
593 G1CMRootRegions* root_regions() { return &_root_regions; }
594
595 bool concurrent_marking_in_progress() {
596 return _concurrent_marking_in_progress;
597 }
598 void set_concurrent_marking_in_progress() {
599 _concurrent_marking_in_progress = true;
600 }
601 void clear_concurrent_marking_in_progress() {
602 _concurrent_marking_in_progress = false;
603 }
604
605 void concurrent_cycle_start();
606 void concurrent_cycle_end();
607
608 void update_accum_task_vtime(int i, double vtime) {
609 _accum_task_vtime[i] += vtime;
610 }
611
612 double all_task_accum_vtime() {
613 double ret = 0.0;
614 for (uint i = 0; i < _max_worker_id; ++i)
615 ret += _accum_task_vtime[i];
616 return ret;
617 }
618
619 // Attempts to steal an object from the task queues of other tasks
620 bool try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry);
621
622 G1ConcurrentMark(G1CollectedHeap* g1h,
623 G1RegionToSpaceMapper* prev_bitmap_storage,
624 G1RegionToSpaceMapper* next_bitmap_storage);
625 ~G1ConcurrentMark();
626
627 ConcurrentMarkThread* cmThread() { return _cmThread; }
628
629 G1CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
630 G1CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
631
632 // Returns the number of GC threads to be used in a concurrent
633 // phase based on the number of GC threads being used in a STW
634 // phase.
635 uint scale_parallel_threads(uint n_par_threads);
636
637 // Calculates the number of GC threads to be used in a concurrent phase.
638 uint calc_parallel_marking_threads();
639
640 // The following three are interaction between CM and
641 // G1CollectedHeap
642
643 // This notifies CM that a root during initial-mark needs to be
644 // grayed. It is MT-safe. hr is the region that
645 // contains the object and it's passed optionally from callers who
646 // might already have it (no point in recalculating it).
647 inline void grayRoot(oop obj,
648 HeapRegion* hr = NULL);
649
650 // Prepare internal data structures for the next mark cycle. This includes clearing
651 // the next mark bitmap and some internal data structures. This method is intended
652 // to be called concurrently to the mutator. It will yield to safepoint requests.
653 void cleanup_for_next_mark();
654
655 // Clear the previous marking bitmap during safepoint.
656 void clear_prev_bitmap(WorkGang* workers);
657
658 // Return whether the next mark bitmap has no marks set. To be used for assertions
659 // only. Will not yield to pause requests.
660 bool nextMarkBitmapIsClear();
661
662 // These two do the work that needs to be done before and after the
663 // initial root checkpoint. Since this checkpoint can be done at two
664 // different points (i.e. an explicit pause or piggy-backed on a
665 // young collection), then it's nice to be able to easily share the
666 // pre/post code. It might be the case that we can put everything in
667 // the post method. TP
668 void checkpointRootsInitialPre();
669 void checkpointRootsInitialPost();
670
671 // Scan all the root regions and mark everything reachable from
672 // them.
673 void scan_root_regions();
674
675 // Scan a single root region and mark everything reachable from it.
676 void scanRootRegion(HeapRegion* hr);
677
678 // Do concurrent phase of marking, to a tentative transitive closure.
679 void mark_from_roots();
680
681 void checkpointRootsFinal(bool clear_all_soft_refs);
682 void checkpointRootsFinalWork();
683 void cleanup();
684 void complete_cleanup();
685
686 // Mark in the previous bitmap. NB: this is usually read-only, so use
687 // this carefully!
688 inline void markPrev(oop p);
689
690 // Clears marks for all objects in the given range, for the prev or
691 // next bitmaps. NB: the previous bitmap is usually
692 // read-only, so use this carefully!
693 void clearRangePrevBitmap(MemRegion mr);
694
695 // Verify that there are no CSet oops on the stacks (taskqueues /
696 // global mark stack) and fingers (global / per-task).
697 // If marking is not in progress, it's a no-op.
698 void verify_no_cset_oops() PRODUCT_RETURN;
699
700 inline bool isPrevMarked(oop p) const;
701
702 inline bool do_yield_check();
703
704 // Abandon current marking iteration due to a Full GC.
705 void abort();
706
707 bool has_aborted() { return _has_aborted; }
708
709 void print_summary_info();
710
711 void print_worker_threads_on(outputStream* st) const;
712 void threads_do(ThreadClosure* tc) const;
713
714 void print_on_error(outputStream* st) const;
715
716 // Attempts to mark the given object on the next mark bitmap.
717 inline bool par_mark(oop obj);
718
719 // Returns true if initialization was successfully completed.
720 bool completed_initialization() const {
721 return _completed_initialization;
722 }
723
724 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
725 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
726
727 private:
728 // Clear (Reset) all liveness count data.
729 void clear_live_data(WorkGang* workers);
730
731 #ifdef ASSERT
732 // Verify all of the above data structures that they are in initial state.
733 void verify_live_data_clear();
734 #endif
735
736 // Aggregates the per-card liveness data based on the current marking. Also sets
737 // the amount of marked bytes for each region.
738 void create_live_data();
739
740 void finalize_live_data();
741
742 void verify_live_data();
743 };
744
745 // A class representing a marking task.
746 class G1CMTask : public TerminatorTerminator {
747 private:
748 enum PrivateConstants {
749 // The regular clock call is called once the scanned words reaches
750 // this limit
751 words_scanned_period = 12*1024,
752 // The regular clock call is called once the number of visited
753 // references reaches this limit
754 refs_reached_period = 1024,
755 // Initial value for the hash seed, used in the work stealing code
756 init_hash_seed = 17
757 };
758
759 G1CMObjArrayProcessor _objArray_processor;
760
761 uint _worker_id;
762 G1CollectedHeap* _g1h;
763 G1ConcurrentMark* _cm;
764 G1CMBitMap* _nextMarkBitMap;
765 // the task queue of this task
766 G1CMTaskQueue* _task_queue;
767 private:
768 // the task queue set---needed for stealing
769 G1CMTaskQueueSet* _task_queues;
770 // indicates whether the task has been claimed---this is only for
771 // debugging purposes
772 bool _claimed;
773
774 // number of calls to this task
775 int _calls;
776
777 // when the virtual timer reaches this time, the marking step should
778 // exit
779 double _time_target_ms;
780 // the start time of the current marking step
781 double _start_time_ms;
782
783 // the oop closure used for iterations over oops
784 G1CMOopClosure* _cm_oop_closure;
785
786 // the region this task is scanning, NULL if we're not scanning any
787 HeapRegion* _curr_region;
788 // the local finger of this task, NULL if we're not scanning a region
789 HeapWord* _finger;
790 // limit of the region this task is scanning, NULL if we're not scanning one
791 HeapWord* _region_limit;
792
793 // the number of words this task has scanned
794 size_t _words_scanned;
795 // When _words_scanned reaches this limit, the regular clock is
796 // called. Notice that this might be decreased under certain
797 // circumstances (i.e. when we believe that we did an expensive
798 // operation).
799 size_t _words_scanned_limit;
800 // the initial value of _words_scanned_limit (i.e. what it was
801 // before it was decreased).
802 size_t _real_words_scanned_limit;
803
804 // the number of references this task has visited
805 size_t _refs_reached;
806 // When _refs_reached reaches this limit, the regular clock is
807 // called. Notice this this might be decreased under certain
808 // circumstances (i.e. when we believe that we did an expensive
809 // operation).
810 size_t _refs_reached_limit;
811 // the initial value of _refs_reached_limit (i.e. what it was before
812 // it was decreased).
813 size_t _real_refs_reached_limit;
814
815 // used by the work stealing stuff
816 int _hash_seed;
817 // if this is true, then the task has aborted for some reason
818 bool _has_aborted;
819 // set when the task aborts because it has met its time quota
820 bool _has_timed_out;
821 // true when we're draining SATB buffers; this avoids the task
822 // aborting due to SATB buffers being available (as we're already
823 // dealing with them)
824 bool _draining_satb_buffers;
825
826 // number sequence of past step times
827 NumberSeq _step_times_ms;
828 // elapsed time of this task
829 double _elapsed_time_ms;
830 // termination time of this task
831 double _termination_time_ms;
832 // when this task got into the termination protocol
833 double _termination_start_time_ms;
834
835 // true when the task is during a concurrent phase, false when it is
836 // in the remark phase (so, in the latter case, we do not have to
837 // check all the things that we have to check during the concurrent
838 // phase, i.e. SATB buffer availability...)
839 bool _concurrent;
840
841 TruncatedSeq _marking_step_diffs_ms;
842
843 // it updates the local fields after this task has claimed
844 // a new region to scan
845 void setup_for_region(HeapRegion* hr);
846 // it brings up-to-date the limit of the region
847 void update_region_limit();
848
849 // called when either the words scanned or the refs visited limit
850 // has been reached
851 void reached_limit();
852 // recalculates the words scanned and refs visited limits
853 void recalculate_limits();
854 // decreases the words scanned and refs visited limits when we reach
855 // an expensive operation
856 void decrease_limits();
857 // it checks whether the words scanned or refs visited reached their
858 // respective limit and calls reached_limit() if they have
859 void check_limits() {
860 if (_words_scanned >= _words_scanned_limit ||
861 _refs_reached >= _refs_reached_limit) {
862 reached_limit();
863 }
864 }
865 // this is supposed to be called regularly during a marking step as
866 // it checks a bunch of conditions that might cause the marking step
867 // to abort
868 void regular_clock_call();
869 bool concurrent() { return _concurrent; }
870
871 // Test whether obj might have already been passed over by the
872 // mark bitmap scan, and so needs to be pushed onto the mark stack.
873 bool is_below_finger(oop obj, HeapWord* global_finger) const;
874
875 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
876 public:
877 // Apply the closure on the given area of the objArray. Return the number of words
878 // scanned.
879 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
880 // It resets the task; it should be called right at the beginning of
881 // a marking phase.
882 void reset(G1CMBitMap* _nextMarkBitMap);
883 // it clears all the fields that correspond to a claimed region.
884 void clear_region_fields();
885
886 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
887
888 // The main method of this class which performs a marking step
889 // trying not to exceed the given duration. However, it might exit
890 // prematurely, according to some conditions (i.e. SATB buffers are
891 // available for processing).
892 void do_marking_step(double target_ms,
893 bool do_termination,
894 bool is_serial);
895
896 // These two calls start and stop the timer
897 void record_start_time() {
898 _elapsed_time_ms = os::elapsedTime() * 1000.0;
899 }
900 void record_end_time() {
901 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
902 }
903
904 // returns the worker ID associated with this task.
905 uint worker_id() { return _worker_id; }
906
907 // From TerminatorTerminator. It determines whether this task should
908 // exit the termination protocol after it's entered it.
909 virtual bool should_exit_termination();
910
911 // Resets the local region fields after a task has finished scanning a
912 // region; or when they have become stale as a result of the region
913 // being evacuated.
914 void giveup_current_region();
915
916 HeapWord* finger() { return _finger; }
917
918 bool has_aborted() { return _has_aborted; }
919 void set_has_aborted() { _has_aborted = true; }
920 void clear_has_aborted() { _has_aborted = false; }
921 bool has_timed_out() { return _has_timed_out; }
922 bool claimed() { return _claimed; }
923
924 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
925
926 // Increment the number of references this task has visited.
927 void increment_refs_reached() { ++_refs_reached; }
928
929 // Grey the object by marking it. If not already marked, push it on
930 // the local queue if below the finger.
931 // obj is below its region's NTAMS.
932 inline void make_reference_grey(oop obj);
933
934 // Grey the object (by calling make_grey_reference) if required,
935 // e.g. obj is below its containing region's NTAMS.
936 // Precondition: obj is a valid heap object.
937 inline void deal_with_reference(oop obj);
938
939 // It scans an object and visits its children.
940 inline void scan_task_entry(G1TaskQueueEntry task_entry);
941
942 // It pushes an object on the local queue.
943 inline void push(G1TaskQueueEntry task_entry);
944
945 // Move entries to the global stack.
946 void move_entries_to_global_stack();
947 // Move entries from the global stack, return true if we were successful to do so.
948 bool get_entries_from_global_stack();
949
950 // It pops and scans objects from the local queue. If partially is
951 // true, then it stops when the queue size is of a given limit. If
952 // partially is false, then it stops when the queue is empty.
953 void drain_local_queue(bool partially);
954 // It moves entries from the global stack to the local queue and
955 // drains the local queue. If partially is true, then it stops when
956 // both the global stack and the local queue reach a given size. If
957 // partially if false, it tries to empty them totally.
958 void drain_global_stack(bool partially);
959 // It keeps picking SATB buffers and processing them until no SATB
960 // buffers are available.
961 void drain_satb_buffers();
962
963 // moves the local finger to a new location
964 inline void move_finger_to(HeapWord* new_finger) {
965 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
966 _finger = new_finger;
967 }
968
969 G1CMTask(uint worker_id,
970 G1ConcurrentMark *cm,
971 G1CMTaskQueue* task_queue,
972 G1CMTaskQueueSet* task_queues);
973
974 // it prints statistics associated with this task
975 void print_stats();
976 };
977
978 // Class that's used to to print out per-region liveness
979 // information. It's currently used at the end of marking and also
980 // after we sort the old regions at the end of the cleanup operation.
981 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
982 private:
983 // Accumulators for these values.
984 size_t _total_used_bytes;
985 size_t _total_capacity_bytes;
986 size_t _total_prev_live_bytes;
987 size_t _total_next_live_bytes;
988
989 // Accumulator for the remembered set size
990 size_t _total_remset_bytes;
991
992 // Accumulator for strong code roots memory size
993 size_t _total_strong_code_roots_bytes;
994
995 static double perc(size_t val, size_t total) {
996 if (total == 0) {
997 return 0.0;
998 } else {
999 return 100.0 * ((double) val / (double) total);
1000 }
1001 }
1002
1003 static double bytes_to_mb(size_t val) {
1004 return (double) val / (double) M;
1005 }
1006
1007 public:
1008 // The header and footer are printed in the constructor and
1009 // destructor respectively.
1010 G1PrintRegionLivenessInfoClosure(const char* phase_name);
1011 virtual bool doHeapRegion(HeapRegion* r);
1012 ~G1PrintRegionLivenessInfoClosure();
1013 };
1014
1015 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP