rev 57156 : imported patch 8234796-v3
1 /*
2 * Copyright (c) 2001, 2019, 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 #include "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc/g1/g1BarrierSet.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectorState.hpp"
31 #include "gc/g1/g1ConcurrentMark.inline.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1DirtyCardQueue.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/g1ThreadLocalData.hpp"
40 #include "gc/g1/g1Trace.hpp"
41 #include "gc/g1/heapRegion.inline.hpp"
42 #include "gc/g1/heapRegionRemSet.hpp"
43 #include "gc/g1/heapRegionSet.inline.hpp"
44 #include "gc/shared/gcId.hpp"
45 #include "gc/shared/gcTimer.hpp"
46 #include "gc/shared/gcTraceTime.inline.hpp"
47 #include "gc/shared/gcVMOperations.hpp"
48 #include "gc/shared/genOopClosures.inline.hpp"
49 #include "gc/shared/referencePolicy.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/suspendibleThreadSet.hpp"
52 #include "gc/shared/taskqueue.inline.hpp"
53 #include "gc/shared/weakProcessor.inline.hpp"
54 #include "gc/shared/workerPolicy.hpp"
55 #include "include/jvm.h"
56 #include "logging/log.hpp"
57 #include "memory/allocation.hpp"
58 #include "memory/iterator.hpp"
59 #include "memory/resourceArea.hpp"
60 #include "memory/universe.hpp"
61 #include "oops/access.inline.hpp"
62 #include "oops/oop.inline.hpp"
63 #include "runtime/atomic.hpp"
64 #include "runtime/handles.inline.hpp"
65 #include "runtime/java.hpp"
66 #include "runtime/orderAccess.hpp"
67 #include "runtime/prefetch.inline.hpp"
68 #include "services/memTracker.hpp"
69 #include "utilities/align.hpp"
70 #include "utilities/growableArray.hpp"
71
72 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) {
73 assert(addr < _cm->finger(), "invariant");
74 assert(addr >= _task->finger(), "invariant");
75
76 // We move that task's local finger along.
77 _task->move_finger_to(addr);
78
79 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
80 // we only partially drain the local queue and global stack
81 _task->drain_local_queue(true);
82 _task->drain_global_stack(true);
83
84 // if the has_aborted flag has been raised, we need to bail out of
85 // the iteration
86 return !_task->has_aborted();
87 }
88
89 G1CMMarkStack::G1CMMarkStack() :
90 _max_chunk_capacity(0),
91 _base(NULL),
92 _chunk_capacity(0) {
93 set_empty();
94 }
95
96 bool G1CMMarkStack::resize(size_t new_capacity) {
97 assert(is_empty(), "Only resize when stack is empty.");
98 assert(new_capacity <= _max_chunk_capacity,
99 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
100
101 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC);
102
103 if (new_base == NULL) {
104 log_warning(gc)("Failed to reserve memory for new overflow mark stack with " SIZE_FORMAT " chunks and size " SIZE_FORMAT "B.", new_capacity, new_capacity * sizeof(TaskQueueEntryChunk));
105 return false;
106 }
107 // Release old mapping.
108 if (_base != NULL) {
109 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
110 }
111
112 _base = new_base;
113 _chunk_capacity = new_capacity;
114 set_empty();
115
116 return true;
117 }
118
119 size_t G1CMMarkStack::capacity_alignment() {
120 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
121 }
122
123 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
124 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
125
126 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
127
128 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
129 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
130
131 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
132 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
133 _max_chunk_capacity,
134 initial_chunk_capacity);
135
136 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
137 initial_chunk_capacity, _max_chunk_capacity);
138
139 return resize(initial_chunk_capacity);
140 }
141
142 void G1CMMarkStack::expand() {
143 if (_chunk_capacity == _max_chunk_capacity) {
144 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
145 return;
146 }
147 size_t old_capacity = _chunk_capacity;
148 // Double capacity if possible
149 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
150
151 if (resize(new_capacity)) {
152 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
153 old_capacity, new_capacity);
154 } else {
155 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
156 old_capacity, new_capacity);
157 }
158 }
159
160 G1CMMarkStack::~G1CMMarkStack() {
161 if (_base != NULL) {
162 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
163 }
164 }
165
166 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
167 elem->next = *list;
168 *list = elem;
169 }
170
171 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
172 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
173 add_chunk_to_list(&_chunk_list, elem);
174 _chunks_in_chunk_list++;
175 }
176
177 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
178 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
179 add_chunk_to_list(&_free_list, elem);
180 }
181
182 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
183 TaskQueueEntryChunk* result = *list;
184 if (result != NULL) {
185 *list = (*list)->next;
186 }
187 return result;
188 }
189
190 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
191 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
192 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
193 if (result != NULL) {
194 _chunks_in_chunk_list--;
195 }
196 return result;
197 }
198
199 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
200 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
201 return remove_chunk_from_list(&_free_list);
202 }
203
204 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
205 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
206 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
207 // wraparound of _hwm.
208 if (_hwm >= _chunk_capacity) {
209 return NULL;
210 }
211
212 size_t cur_idx = Atomic::add(&_hwm, 1u) - 1;
213 if (cur_idx >= _chunk_capacity) {
214 return NULL;
215 }
216
217 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
218 result->next = NULL;
219 return result;
220 }
221
222 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
223 // Get a new chunk.
224 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
225
226 if (new_chunk == NULL) {
227 // Did not get a chunk from the free list. Allocate from backing memory.
228 new_chunk = allocate_new_chunk();
229
230 if (new_chunk == NULL) {
231 return false;
232 }
233 }
234
235 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
236
237 add_chunk_to_chunk_list(new_chunk);
238
239 return true;
240 }
241
242 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
243 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
244
245 if (cur == NULL) {
246 return false;
247 }
248
249 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
250
251 add_chunk_to_free_list(cur);
252 return true;
253 }
254
255 void G1CMMarkStack::set_empty() {
256 _chunks_in_chunk_list = 0;
257 _hwm = 0;
258 _chunk_list = NULL;
259 _free_list = NULL;
260 }
261
262 G1CMRootMemRegions::G1CMRootMemRegions(uint const max_regions) :
263 _root_regions(NULL),
264 _max_regions(max_regions),
265 _num_root_regions(0),
266 _claimed_root_regions(0),
267 _scan_in_progress(false),
268 _should_abort(false) {
269 _root_regions = new MemRegion[_max_regions];
270 if (_root_regions == NULL) {
271 vm_exit_during_initialization("Could not allocate root MemRegion set.");
272 }
273 }
274
275 G1CMRootMemRegions::~G1CMRootMemRegions() {
276 delete[] _root_regions;
277 }
278
279 void G1CMRootMemRegions::reset() {
280 _num_root_regions = 0;
281 }
282
283 void G1CMRootMemRegions::add(HeapWord* start, HeapWord* end) {
284 assert_at_safepoint();
285 size_t idx = Atomic::add(&_num_root_regions, (size_t)1) - 1;
286 assert(idx < _max_regions, "Trying to add more root MemRegions than there is space " SIZE_FORMAT, _max_regions);
287 assert(start != NULL && end != NULL && start <= end, "Start (" PTR_FORMAT ") should be less or equal to "
288 "end (" PTR_FORMAT ")", p2i(start), p2i(end));
289 _root_regions[idx].set_start(start);
290 _root_regions[idx].set_end(end);
291 }
292
293 void G1CMRootMemRegions::prepare_for_scan() {
294 assert(!scan_in_progress(), "pre-condition");
295
296 _scan_in_progress = _num_root_regions > 0;
297
298 _claimed_root_regions = 0;
299 _should_abort = false;
300 }
301
302 const MemRegion* G1CMRootMemRegions::claim_next() {
303 if (_should_abort) {
304 // If someone has set the should_abort flag, we return NULL to
305 // force the caller to bail out of their loop.
306 return NULL;
307 }
308
309 if (_claimed_root_regions >= _num_root_regions) {
310 return NULL;
311 }
312
313 size_t claimed_index = Atomic::add(&_claimed_root_regions, (size_t)1) - 1;
314 if (claimed_index < _num_root_regions) {
315 return &_root_regions[claimed_index];
316 }
317 return NULL;
318 }
319
320 uint G1CMRootMemRegions::num_root_regions() const {
321 return (uint)_num_root_regions;
322 }
323
324 void G1CMRootMemRegions::notify_scan_done() {
325 MutexLocker x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
326 _scan_in_progress = false;
327 RootRegionScan_lock->notify_all();
328 }
329
330 void G1CMRootMemRegions::cancel_scan() {
331 notify_scan_done();
332 }
333
334 void G1CMRootMemRegions::scan_finished() {
335 assert(scan_in_progress(), "pre-condition");
336
337 if (!_should_abort) {
338 assert(_claimed_root_regions >= num_root_regions(),
339 "we should have claimed all root regions, claimed " SIZE_FORMAT ", length = %u",
340 _claimed_root_regions, num_root_regions());
341 }
342
343 notify_scan_done();
344 }
345
346 bool G1CMRootMemRegions::wait_until_scan_finished() {
347 if (!scan_in_progress()) {
348 return false;
349 }
350
351 {
352 MonitorLocker ml(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
353 while (scan_in_progress()) {
354 ml.wait();
355 }
356 }
357 return true;
358 }
359
360 // Returns the maximum number of workers to be used in a concurrent
361 // phase based on the number of GC workers being used in a STW
362 // phase.
363 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
364 return MAX2((num_gc_workers + 2) / 4, 1U);
365 }
366
367 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h,
368 G1RegionToSpaceMapper* prev_bitmap_storage,
369 G1RegionToSpaceMapper* next_bitmap_storage) :
370 // _cm_thread set inside the constructor
371 _g1h(g1h),
372 _completed_initialization(false),
373
374 _mark_bitmap_1(),
375 _mark_bitmap_2(),
376 _prev_mark_bitmap(&_mark_bitmap_1),
377 _next_mark_bitmap(&_mark_bitmap_2),
378
379 _heap(_g1h->reserved_region()),
380
381 _root_regions(_g1h->max_regions()),
382
383 _global_mark_stack(),
384
385 // _finger set in set_non_marking_state
386
387 _worker_id_offset(G1DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads),
388 _max_num_tasks(ParallelGCThreads),
389 // _num_active_tasks set in set_non_marking_state()
390 // _tasks set inside the constructor
391
392 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)),
393 _terminator((int) _max_num_tasks, _task_queues),
394
395 _first_overflow_barrier_sync(),
396 _second_overflow_barrier_sync(),
397
398 _has_overflown(false),
399 _concurrent(false),
400 _has_aborted(false),
401 _restart_for_overflow(false),
402 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
403 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
404
405 // _verbose_level set below
406
407 _init_times(),
408 _remark_times(),
409 _remark_mark_times(),
410 _remark_weak_ref_times(),
411 _cleanup_times(),
412 _total_cleanup_time(0.0),
413
414 _accum_task_vtime(NULL),
415
416 _concurrent_workers(NULL),
417 _num_concurrent_workers(0),
418 _max_concurrent_workers(0),
419
420 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)),
421 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC))
422 {
423 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage);
424 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage);
425
426 // Create & start ConcurrentMark thread.
427 _cm_thread = new G1ConcurrentMarkThread(this);
428 if (_cm_thread->osthread() == NULL) {
429 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
430 }
431
432 assert(CGC_lock != NULL, "CGC_lock must be initialized");
433
434 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
435 // Calculate the number of concurrent worker threads by scaling
436 // the number of parallel GC threads.
437 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
438 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num);
439 }
440
441 assert(ConcGCThreads > 0, "ConcGCThreads have been set.");
442 if (ConcGCThreads > ParallelGCThreads) {
443 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).",
444 ConcGCThreads, ParallelGCThreads);
445 return;
446 }
447
448 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset);
449 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
450
451 _num_concurrent_workers = ConcGCThreads;
452 _max_concurrent_workers = _num_concurrent_workers;
453
454 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true);
455 _concurrent_workers->initialize_workers();
456
457 if (FLAG_IS_DEFAULT(MarkStackSize)) {
458 size_t mark_stack_size =
459 MIN2(MarkStackSizeMax,
460 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE)));
461 // Verify that the calculated value for MarkStackSize is in range.
462 // It would be nice to use the private utility routine from Arguments.
463 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
464 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
465 "must be between 1 and " SIZE_FORMAT,
466 mark_stack_size, MarkStackSizeMax);
467 return;
468 }
469 FLAG_SET_ERGO(MarkStackSize, mark_stack_size);
470 } else {
471 // Verify MarkStackSize is in range.
472 if (FLAG_IS_CMDLINE(MarkStackSize)) {
473 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
474 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
475 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
476 "must be between 1 and " SIZE_FORMAT,
477 MarkStackSize, MarkStackSizeMax);
478 return;
479 }
480 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
481 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
482 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
483 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
484 MarkStackSize, MarkStackSizeMax);
485 return;
486 }
487 }
488 }
489 }
490
491 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
492 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
493 }
494
495 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC);
496 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC);
497
498 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
499 _num_active_tasks = _max_num_tasks;
500
501 for (uint i = 0; i < _max_num_tasks; ++i) {
502 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
503 task_queue->initialize();
504 _task_queues->register_queue(i, task_queue);
505
506 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions());
507
508 _accum_task_vtime[i] = 0.0;
509 }
510
511 reset_at_marking_complete();
512 _completed_initialization = true;
513 }
514
515 void G1ConcurrentMark::reset() {
516 _has_aborted = false;
517
518 reset_marking_for_restart();
519
520 // Reset all tasks, since different phases will use different number of active
521 // threads. So, it's easiest to have all of them ready.
522 for (uint i = 0; i < _max_num_tasks; ++i) {
523 _tasks[i]->reset(_next_mark_bitmap);
524 }
525
526 uint max_regions = _g1h->max_regions();
527 for (uint i = 0; i < max_regions; i++) {
528 _top_at_rebuild_starts[i] = NULL;
529 _region_mark_stats[i].clear();
530 }
531 }
532
533 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) {
534 for (uint j = 0; j < _max_num_tasks; ++j) {
535 _tasks[j]->clear_mark_stats_cache(region_idx);
536 }
537 _top_at_rebuild_starts[region_idx] = NULL;
538 _region_mark_stats[region_idx].clear();
539 }
540
541 void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
542 uint const region_idx = r->hrm_index();
543 if (r->is_humongous()) {
544 assert(r->is_starts_humongous(), "Got humongous continues region here");
545 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size());
546 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
547 clear_statistics_in_region(j);
548 }
549 } else {
550 clear_statistics_in_region(region_idx);
551 }
552 }
553
554 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) {
555 if (bitmap->is_marked(addr)) {
556 bitmap->clear(addr);
557 }
558 }
559
560 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
561 assert_at_safepoint_on_vm_thread();
562
563 // Need to clear all mark bits of the humongous object.
564 clear_mark_if_set(_prev_mark_bitmap, r->bottom());
565 clear_mark_if_set(_next_mark_bitmap, r->bottom());
566
567 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
568 return;
569 }
570
571 // Clear any statistics about the region gathered so far.
572 clear_statistics(r);
573 }
574
575 void G1ConcurrentMark::reset_marking_for_restart() {
576 _global_mark_stack.set_empty();
577
578 // Expand the marking stack, if we have to and if we can.
579 if (has_overflown()) {
580 _global_mark_stack.expand();
581
582 uint max_regions = _g1h->max_regions();
583 for (uint i = 0; i < max_regions; i++) {
584 _region_mark_stats[i].clear_during_overflow();
585 }
586 }
587
588 clear_has_overflown();
589 _finger = _heap.start();
590
591 for (uint i = 0; i < _max_num_tasks; ++i) {
592 G1CMTaskQueue* queue = _task_queues->queue(i);
593 queue->set_empty();
594 }
595 }
596
597 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
598 assert(active_tasks <= _max_num_tasks, "we should not have more");
599
600 _num_active_tasks = active_tasks;
601 // Need to update the three data structures below according to the
602 // number of active threads for this phase.
603 _terminator.terminator()->reset_for_reuse((int) active_tasks);
604 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
605 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
606 }
607
608 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
609 set_concurrency(active_tasks);
610
611 _concurrent = concurrent;
612
613 if (!concurrent) {
614 // At this point we should be in a STW phase, and completed marking.
615 assert_at_safepoint_on_vm_thread();
616 assert(out_of_regions(),
617 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
618 p2i(_finger), p2i(_heap.end()));
619 }
620 }
621
622 void G1ConcurrentMark::reset_at_marking_complete() {
623 // We set the global marking state to some default values when we're
624 // not doing marking.
625 reset_marking_for_restart();
626 _num_active_tasks = 0;
627 }
628
629 G1ConcurrentMark::~G1ConcurrentMark() {
630 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts);
631 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats);
632 // The G1ConcurrentMark instance is never freed.
633 ShouldNotReachHere();
634 }
635
636 class G1ClearBitMapTask : public AbstractGangTask {
637 public:
638 static size_t chunk_size() { return M; }
639
640 private:
641 // Heap region closure used for clearing the given mark bitmap.
642 class G1ClearBitmapHRClosure : public HeapRegionClosure {
643 private:
644 G1CMBitMap* _bitmap;
645 G1ConcurrentMark* _cm;
646 public:
647 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) {
648 }
649
650 virtual bool do_heap_region(HeapRegion* r) {
651 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
652
653 HeapWord* cur = r->bottom();
654 HeapWord* const end = r->end();
655
656 while (cur < end) {
657 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
658 _bitmap->clear_range(mr);
659
660 cur += chunk_size_in_words;
661
662 // Abort iteration if after yielding the marking has been aborted.
663 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
664 return true;
665 }
666 // Repeat the asserts from before the start of the closure. We will do them
667 // as asserts here to minimize their overhead on the product. However, we
668 // will have them as guarantees at the beginning / end of the bitmap
669 // clearing to get some checking in the product.
670 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant");
671 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant");
672 }
673 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
674
675 return false;
676 }
677 };
678
679 G1ClearBitmapHRClosure _cl;
680 HeapRegionClaimer _hr_claimer;
681 bool _suspendible; // If the task is suspendible, workers must join the STS.
682
683 public:
684 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
685 AbstractGangTask("G1 Clear Bitmap"),
686 _cl(bitmap, suspendible ? cm : NULL),
687 _hr_claimer(n_workers),
688 _suspendible(suspendible)
689 { }
690
691 void work(uint worker_id) {
692 SuspendibleThreadSetJoiner sts_join(_suspendible);
693 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
694 }
695
696 bool is_complete() {
697 return _cl.is_complete();
698 }
699 };
700
701 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
702 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
703
704 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
705 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
706
707 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
708
709 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
710
711 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
712 workers->run_task(&cl, num_workers);
713 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
714 }
715
716 void G1ConcurrentMark::cleanup_for_next_mark() {
717 // Make sure that the concurrent mark thread looks to still be in
718 // the current cycle.
719 guarantee(cm_thread()->during_cycle(), "invariant");
720
721 // We are finishing up the current cycle by clearing the next
722 // marking bitmap and getting it ready for the next cycle. During
723 // this time no other cycle can start. So, let's make sure that this
724 // is the case.
725 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
726
727 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true);
728
729 // Repeat the asserts from above.
730 guarantee(cm_thread()->during_cycle(), "invariant");
731 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
732 }
733
734 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
735 assert_at_safepoint_on_vm_thread();
736 clear_bitmap(_prev_mark_bitmap, workers, false);
737 }
738
739 class NoteStartOfMarkHRClosure : public HeapRegionClosure {
740 public:
741 bool do_heap_region(HeapRegion* r) {
742 r->note_start_of_marking();
743 return false;
744 }
745 };
746
747 void G1ConcurrentMark::pre_initial_mark() {
748 assert_at_safepoint_on_vm_thread();
749
750 // Reset marking state.
751 reset();
752
753 // For each region note start of marking.
754 NoteStartOfMarkHRClosure startcl;
755 _g1h->heap_region_iterate(&startcl);
756
757 _root_regions.reset();
758 }
759
760
761 void G1ConcurrentMark::post_initial_mark() {
762 // Start Concurrent Marking weak-reference discovery.
763 ReferenceProcessor* rp = _g1h->ref_processor_cm();
764 // enable ("weak") refs discovery
765 rp->enable_discovery();
766 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
767
768 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
769 // This is the start of the marking cycle, we're expected all
770 // threads to have SATB queues with active set to false.
771 satb_mq_set.set_active_all_threads(true, /* new active value */
772 false /* expected_active */);
773
774 _root_regions.prepare_for_scan();
775
776 // update_g1_committed() will be called at the end of an evac pause
777 // when marking is on. So, it's also called at the end of the
778 // initial-mark pause to update the heap end, if the heap expands
779 // during it. No need to call it here.
780 }
781
782 /*
783 * Notice that in the next two methods, we actually leave the STS
784 * during the barrier sync and join it immediately afterwards. If we
785 * do not do this, the following deadlock can occur: one thread could
786 * be in the barrier sync code, waiting for the other thread to also
787 * sync up, whereas another one could be trying to yield, while also
788 * waiting for the other threads to sync up too.
789 *
790 * Note, however, that this code is also used during remark and in
791 * this case we should not attempt to leave / enter the STS, otherwise
792 * we'll either hit an assert (debug / fastdebug) or deadlock
793 * (product). So we should only leave / enter the STS if we are
794 * operating concurrently.
795 *
796 * Because the thread that does the sync barrier has left the STS, it
797 * is possible to be suspended for a Full GC or an evacuation pause
798 * could occur. This is actually safe, since the entering the sync
799 * barrier is one of the last things do_marking_step() does, and it
800 * doesn't manipulate any data structures afterwards.
801 */
802
803 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
804 bool barrier_aborted;
805 {
806 SuspendibleThreadSetLeaver sts_leave(concurrent());
807 barrier_aborted = !_first_overflow_barrier_sync.enter();
808 }
809
810 // at this point everyone should have synced up and not be doing any
811 // more work
812
813 if (barrier_aborted) {
814 // If the barrier aborted we ignore the overflow condition and
815 // just abort the whole marking phase as quickly as possible.
816 return;
817 }
818 }
819
820 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
821 SuspendibleThreadSetLeaver sts_leave(concurrent());
822 _second_overflow_barrier_sync.enter();
823
824 // at this point everything should be re-initialized and ready to go
825 }
826
827 class G1CMConcurrentMarkingTask : public AbstractGangTask {
828 G1ConcurrentMark* _cm;
829
830 public:
831 void work(uint worker_id) {
832 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread");
833 ResourceMark rm;
834
835 double start_vtime = os::elapsedVTime();
836
837 {
838 SuspendibleThreadSetJoiner sts_join;
839
840 assert(worker_id < _cm->active_tasks(), "invariant");
841
842 G1CMTask* task = _cm->task(worker_id);
843 task->record_start_time();
844 if (!_cm->has_aborted()) {
845 do {
846 task->do_marking_step(G1ConcMarkStepDurationMillis,
847 true /* do_termination */,
848 false /* is_serial*/);
849
850 _cm->do_yield_check();
851 } while (!_cm->has_aborted() && task->has_aborted());
852 }
853 task->record_end_time();
854 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant");
855 }
856
857 double end_vtime = os::elapsedVTime();
858 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
859 }
860
861 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) :
862 AbstractGangTask("Concurrent Mark"), _cm(cm) { }
863
864 ~G1CMConcurrentMarkingTask() { }
865 };
866
867 uint G1ConcurrentMark::calc_active_marking_workers() {
868 uint result = 0;
869 if (!UseDynamicNumberOfGCThreads ||
870 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
871 !ForceDynamicNumberOfGCThreads)) {
872 result = _max_concurrent_workers;
873 } else {
874 result =
875 WorkerPolicy::calc_default_active_workers(_max_concurrent_workers,
876 1, /* Minimum workers */
877 _num_concurrent_workers,
878 Threads::number_of_non_daemon_threads());
879 // Don't scale the result down by scale_concurrent_workers() because
880 // that scaling has already gone into "_max_concurrent_workers".
881 }
882 assert(result > 0 && result <= _max_concurrent_workers,
883 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u",
884 _max_concurrent_workers, result);
885 return result;
886 }
887
888 void G1ConcurrentMark::scan_root_region(const MemRegion* region, uint worker_id) {
889 #ifdef ASSERT
890 HeapWord* last = region->last();
891 HeapRegion* hr = _g1h->heap_region_containing(last);
892 assert(hr->is_old() || hr->next_top_at_mark_start() == hr->bottom(),
893 "Root regions must be old or survivor/eden but region %u is %s", hr->hrm_index(), hr->get_type_str());
894 assert(hr->next_top_at_mark_start() == region->start(),
895 "MemRegion start should be equal to nTAMS");
896 #endif
897
898 G1RootRegionScanClosure cl(_g1h, this, worker_id);
899
900 const uintx interval = PrefetchScanIntervalInBytes;
901 HeapWord* curr = region->start();
902 const HeapWord* end = region->end();
903 while (curr < end) {
904 Prefetch::read(curr, interval);
905 oop obj = oop(curr);
906 int size = obj->oop_iterate_size(&cl);
907 assert(size == obj->size(), "sanity");
908 curr += size;
909 }
910 }
911
912 class G1CMRootRegionScanTask : public AbstractGangTask {
913 G1ConcurrentMark* _cm;
914 public:
915 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
916 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
917
918 void work(uint worker_id) {
919 assert(Thread::current()->is_ConcurrentGC_thread(),
920 "this should only be done by a conc GC thread");
921
922 G1CMRootMemRegions* root_regions = _cm->root_regions();
923 const MemRegion* region = root_regions->claim_next();
924 while (region != NULL) {
925 _cm->scan_root_region(region, worker_id);
926 region = root_regions->claim_next();
927 }
928 }
929 };
930
931 void G1ConcurrentMark::scan_root_regions() {
932 // scan_in_progress() will have been set to true only if there was
933 // at least one root region to scan. So, if it's false, we
934 // should not attempt to do any further work.
935 if (root_regions()->scan_in_progress()) {
936 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
937
938 _num_concurrent_workers = MIN2(calc_active_marking_workers(),
939 // We distribute work on a per-region basis, so starting
940 // more threads than that is useless.
941 root_regions()->num_root_regions());
942 assert(_num_concurrent_workers <= _max_concurrent_workers,
943 "Maximum number of marking threads exceeded");
944
945 G1CMRootRegionScanTask task(this);
946 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
947 task.name(), _num_concurrent_workers, root_regions()->num_root_regions());
948 _concurrent_workers->run_task(&task, _num_concurrent_workers);
949
950 // It's possible that has_aborted() is true here without actually
951 // aborting the survivor scan earlier. This is OK as it's
952 // mainly used for sanity checking.
953 root_regions()->scan_finished();
954 }
955 }
956
957 void G1ConcurrentMark::concurrent_cycle_start() {
958 _gc_timer_cm->register_gc_start();
959
960 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
961
962 _g1h->trace_heap_before_gc(_gc_tracer_cm);
963 }
964
965 void G1ConcurrentMark::concurrent_cycle_end() {
966 _g1h->collector_state()->set_clearing_next_bitmap(false);
967
968 _g1h->trace_heap_after_gc(_gc_tracer_cm);
969
970 if (has_aborted()) {
971 log_info(gc, marking)("Concurrent Mark Abort");
972 _gc_tracer_cm->report_concurrent_mode_failure();
973 }
974
975 _gc_timer_cm->register_gc_end();
976
977 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
978 }
979
980 void G1ConcurrentMark::mark_from_roots() {
981 _restart_for_overflow = false;
982
983 _num_concurrent_workers = calc_active_marking_workers();
984
985 uint active_workers = MAX2(1U, _num_concurrent_workers);
986
987 // Setting active workers is not guaranteed since fewer
988 // worker threads may currently exist and more may not be
989 // available.
990 active_workers = _concurrent_workers->update_active_workers(active_workers);
991 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers());
992
993 // Parallel task terminator is set in "set_concurrency_and_phase()"
994 set_concurrency_and_phase(active_workers, true /* concurrent */);
995
996 G1CMConcurrentMarkingTask marking_task(this);
997 _concurrent_workers->run_task(&marking_task);
998 print_stats();
999 }
1000
1001 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) {
1002 G1HeapVerifier* verifier = _g1h->verifier();
1003
1004 verifier->verify_region_sets_optional();
1005
1006 if (VerifyDuringGC) {
1007 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm);
1008
1009 size_t const BufLen = 512;
1010 char buffer[BufLen];
1011
1012 jio_snprintf(buffer, BufLen, "During GC (%s)", caller);
1013 verifier->verify(type, vo, buffer);
1014 }
1015
1016 verifier->check_bitmaps(caller);
1017 }
1018
1019 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask {
1020 G1CollectedHeap* _g1h;
1021 G1ConcurrentMark* _cm;
1022 HeapRegionClaimer _hrclaimer;
1023 uint volatile _total_selected_for_rebuild;
1024
1025 G1PrintRegionLivenessInfoClosure _cl;
1026
1027 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure {
1028 G1CollectedHeap* _g1h;
1029 G1ConcurrentMark* _cm;
1030
1031 G1PrintRegionLivenessInfoClosure* _cl;
1032
1033 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild.
1034
1035 void update_remset_before_rebuild(HeapRegion* hr) {
1036 G1RemSetTrackingPolicy* tracking_policy = _g1h->policy()->remset_tracker();
1037
1038 bool selected_for_rebuild;
1039 if (hr->is_humongous()) {
1040 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0;
1041 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live);
1042 } else {
1043 size_t const live_bytes = _cm->liveness(hr->hrm_index());
1044 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes);
1045 }
1046 if (selected_for_rebuild) {
1047 _num_regions_selected_for_rebuild++;
1048 }
1049 _cm->update_top_at_rebuild_start(hr);
1050 }
1051
1052 // Distribute the given words across the humongous object starting with hr and
1053 // note end of marking.
1054 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
1055 uint const region_idx = hr->hrm_index();
1056 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size();
1057 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words);
1058
1059 // "Distributing" zero words means that we only note end of marking for these
1060 // regions.
1061 assert(marked_words == 0 || obj_size_in_words == marked_words,
1062 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT,
1063 obj_size_in_words, marked_words);
1064
1065 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
1066 HeapRegion* const r = _g1h->region_at(i);
1067 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
1068
1069 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)",
1070 words_to_add, i, r->get_type_str());
1071 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize);
1072 marked_words -= words_to_add;
1073 }
1074 assert(marked_words == 0,
1075 SIZE_FORMAT " words left after distributing space across %u regions",
1076 marked_words, num_regions_in_humongous);
1077 }
1078
1079 void update_marked_bytes(HeapRegion* hr) {
1080 uint const region_idx = hr->hrm_index();
1081 size_t const marked_words = _cm->liveness(region_idx);
1082 // The marking attributes the object's size completely to the humongous starts
1083 // region. We need to distribute this value across the entire set of regions a
1084 // humongous object spans.
1085 if (hr->is_humongous()) {
1086 assert(hr->is_starts_humongous() || marked_words == 0,
1087 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)",
1088 marked_words, region_idx, hr->get_type_str());
1089 if (hr->is_starts_humongous()) {
1090 distribute_marked_bytes(hr, marked_words);
1091 }
1092 } else {
1093 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
1094 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize);
1095 }
1096 }
1097
1098 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) {
1099 hr->add_to_marked_bytes(marked_bytes);
1100 _cl->do_heap_region(hr);
1101 hr->note_end_of_marking();
1102 }
1103
1104 public:
1105 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) :
1106 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { }
1107
1108 virtual bool do_heap_region(HeapRegion* r) {
1109 update_remset_before_rebuild(r);
1110 update_marked_bytes(r);
1111
1112 return false;
1113 }
1114
1115 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; }
1116 };
1117
1118 public:
1119 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) :
1120 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"),
1121 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { }
1122
1123 virtual void work(uint worker_id) {
1124 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl);
1125 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id);
1126 Atomic::add(&_total_selected_for_rebuild, update_cl.num_selected_for_rebuild());
1127 }
1128
1129 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; }
1130
1131 // Number of regions for which roughly one thread should be spawned for this work.
1132 static const uint RegionsPerThread = 384;
1133 };
1134
1135 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure {
1136 G1CollectedHeap* _g1h;
1137 public:
1138 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { }
1139
1140 virtual bool do_heap_region(HeapRegion* r) {
1141 _g1h->policy()->remset_tracker()->update_after_rebuild(r);
1142 return false;
1143 }
1144 };
1145
1146 void G1ConcurrentMark::remark() {
1147 assert_at_safepoint_on_vm_thread();
1148
1149 // If a full collection has happened, we should not continue. However we might
1150 // have ended up here as the Remark VM operation has been scheduled already.
1151 if (has_aborted()) {
1152 return;
1153 }
1154
1155 G1Policy* policy = _g1h->policy();
1156 policy->record_concurrent_mark_remark_start();
1157
1158 double start = os::elapsedTime();
1159
1160 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before");
1161
1162 {
1163 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm);
1164 finalize_marking();
1165 }
1166
1167 double mark_work_end = os::elapsedTime();
1168
1169 bool const mark_finished = !has_overflown();
1170 if (mark_finished) {
1171 weak_refs_work(false /* clear_all_soft_refs */);
1172
1173 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1174 // We're done with marking.
1175 // This is the end of the marking cycle, we're expected all
1176 // threads to have SATB queues with active set to true.
1177 satb_mq_set.set_active_all_threads(false, /* new active value */
1178 true /* expected_active */);
1179
1180 {
1181 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm);
1182 flush_all_task_caches();
1183 }
1184
1185 // Install newly created mark bitmap as "prev".
1186 swap_mark_bitmaps();
1187 {
1188 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm);
1189
1190 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) /
1191 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread;
1192 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity);
1193
1194 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers);
1195 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions());
1196 _g1h->workers()->run_task(&cl, num_workers);
1197
1198 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u",
1199 _g1h->num_regions(), cl.total_selected_for_rebuild());
1200 }
1201 {
1202 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm);
1203 reclaim_empty_regions();
1204 }
1205
1206 // Clean out dead classes
1207 if (ClassUnloadingWithConcurrentMark) {
1208 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm);
1209 ClassLoaderDataGraph::purge();
1210 }
1211
1212 _g1h->resize_heap_if_necessary();
1213
1214 compute_new_sizes();
1215
1216 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after");
1217
1218 assert(!restart_for_overflow(), "sanity");
1219 // Completely reset the marking state since marking completed
1220 reset_at_marking_complete();
1221 } else {
1222 // We overflowed. Restart concurrent marking.
1223 _restart_for_overflow = true;
1224
1225 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow");
1226
1227 // Clear the marking state because we will be restarting
1228 // marking due to overflowing the global mark stack.
1229 reset_marking_for_restart();
1230 }
1231
1232 {
1233 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm);
1234 report_object_count(mark_finished);
1235 }
1236
1237 // Statistics
1238 double now = os::elapsedTime();
1239 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1240 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1241 _remark_times.add((now - start) * 1000.0);
1242
1243 policy->record_concurrent_mark_remark_end();
1244 }
1245
1246 class G1ReclaimEmptyRegionsTask : public AbstractGangTask {
1247 // Per-region work during the Cleanup pause.
1248 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure {
1249 G1CollectedHeap* _g1h;
1250 size_t _freed_bytes;
1251 FreeRegionList* _local_cleanup_list;
1252 uint _old_regions_removed;
1253 uint _humongous_regions_removed;
1254
1255 public:
1256 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h,
1257 FreeRegionList* local_cleanup_list) :
1258 _g1h(g1h),
1259 _freed_bytes(0),
1260 _local_cleanup_list(local_cleanup_list),
1261 _old_regions_removed(0),
1262 _humongous_regions_removed(0) { }
1263
1264 size_t freed_bytes() { return _freed_bytes; }
1265 const uint old_regions_removed() { return _old_regions_removed; }
1266 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1267
1268 bool do_heap_region(HeapRegion *hr) {
1269 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) {
1270 _freed_bytes += hr->used();
1271 hr->set_containing_set(NULL);
1272 if (hr->is_humongous()) {
1273 _humongous_regions_removed++;
1274 _g1h->free_humongous_region(hr, _local_cleanup_list);
1275 } else {
1276 _old_regions_removed++;
1277 _g1h->free_region(hr, _local_cleanup_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
1278 }
1279 hr->clear_cardtable();
1280 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index());
1281 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom()));
1282 }
1283
1284 return false;
1285 }
1286 };
1287
1288 G1CollectedHeap* _g1h;
1289 FreeRegionList* _cleanup_list;
1290 HeapRegionClaimer _hrclaimer;
1291
1292 public:
1293 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1294 AbstractGangTask("G1 Cleanup"),
1295 _g1h(g1h),
1296 _cleanup_list(cleanup_list),
1297 _hrclaimer(n_workers) {
1298 }
1299
1300 void work(uint worker_id) {
1301 FreeRegionList local_cleanup_list("Local Cleanup List");
1302 G1ReclaimEmptyRegionsClosure cl(_g1h, &local_cleanup_list);
1303 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1304 assert(cl.is_complete(), "Shouldn't have aborted!");
1305
1306 // Now update the old/humongous region sets
1307 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed());
1308 {
1309 MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1310 _g1h->decrement_summary_bytes(cl.freed_bytes());
1311
1312 _cleanup_list->add_ordered(&local_cleanup_list);
1313 assert(local_cleanup_list.is_empty(), "post-condition");
1314 }
1315 }
1316 };
1317
1318 void G1ConcurrentMark::reclaim_empty_regions() {
1319 WorkGang* workers = _g1h->workers();
1320 FreeRegionList empty_regions_list("Empty Regions After Mark List");
1321
1322 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers());
1323 workers->run_task(&cl);
1324
1325 if (!empty_regions_list.is_empty()) {
1326 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length());
1327 // Now print the empty regions list.
1328 G1HRPrinter* hrp = _g1h->hr_printer();
1329 if (hrp->is_active()) {
1330 FreeRegionListIterator iter(&empty_regions_list);
1331 while (iter.more_available()) {
1332 HeapRegion* hr = iter.get_next();
1333 hrp->cleanup(hr);
1334 }
1335 }
1336 // And actually make them available.
1337 _g1h->prepend_to_freelist(&empty_regions_list);
1338 }
1339 }
1340
1341 void G1ConcurrentMark::compute_new_sizes() {
1342 MetaspaceGC::compute_new_size();
1343
1344 // Cleanup will have freed any regions completely full of garbage.
1345 // Update the soft reference policy with the new heap occupancy.
1346 Universe::update_heap_info_at_gc();
1347
1348 // We reclaimed old regions so we should calculate the sizes to make
1349 // sure we update the old gen/space data.
1350 _g1h->g1mm()->update_sizes();
1351 }
1352
1353 void G1ConcurrentMark::cleanup() {
1354 assert_at_safepoint_on_vm_thread();
1355
1356 // If a full collection has happened, we shouldn't do this.
1357 if (has_aborted()) {
1358 return;
1359 }
1360
1361 G1Policy* policy = _g1h->policy();
1362 policy->record_concurrent_mark_cleanup_start();
1363
1364 double start = os::elapsedTime();
1365
1366 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before");
1367
1368 {
1369 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm);
1370 G1UpdateRemSetTrackingAfterRebuild cl(_g1h);
1371 _g1h->heap_region_iterate(&cl);
1372 }
1373
1374 if (log_is_enabled(Trace, gc, liveness)) {
1375 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup");
1376 _g1h->heap_region_iterate(&cl);
1377 }
1378
1379 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after");
1380
1381 // We need to make this be a "collection" so any collection pause that
1382 // races with it goes around and waits for Cleanup to finish.
1383 _g1h->increment_total_collections();
1384
1385 // Local statistics
1386 double recent_cleanup_time = (os::elapsedTime() - start);
1387 _total_cleanup_time += recent_cleanup_time;
1388 _cleanup_times.add(recent_cleanup_time);
1389
1390 {
1391 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm);
1392 policy->record_concurrent_mark_cleanup_end();
1393 }
1394 }
1395
1396 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1397 // Uses the G1CMTask associated with a worker thread (for serial reference
1398 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1399 // trace referent objects.
1400 //
1401 // Using the G1CMTask and embedded local queues avoids having the worker
1402 // threads operating on the global mark stack. This reduces the risk
1403 // of overflowing the stack - which we would rather avoid at this late
1404 // state. Also using the tasks' local queues removes the potential
1405 // of the workers interfering with each other that could occur if
1406 // operating on the global stack.
1407
1408 class G1CMKeepAliveAndDrainClosure : public OopClosure {
1409 G1ConcurrentMark* _cm;
1410 G1CMTask* _task;
1411 uint _ref_counter_limit;
1412 uint _ref_counter;
1413 bool _is_serial;
1414 public:
1415 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1416 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval),
1417 _ref_counter(_ref_counter_limit), _is_serial(is_serial) {
1418 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1419 }
1420
1421 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1422 virtual void do_oop( oop* p) { do_oop_work(p); }
1423
1424 template <class T> void do_oop_work(T* p) {
1425 if (_cm->has_overflown()) {
1426 return;
1427 }
1428 if (!_task->deal_with_reference(p)) {
1429 // We did not add anything to the mark bitmap (or mark stack), so there is
1430 // no point trying to drain it.
1431 return;
1432 }
1433 _ref_counter--;
1434
1435 if (_ref_counter == 0) {
1436 // We have dealt with _ref_counter_limit references, pushing them
1437 // and objects reachable from them on to the local stack (and
1438 // possibly the global stack). Call G1CMTask::do_marking_step() to
1439 // process these entries.
1440 //
1441 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1442 // there's nothing more to do (i.e. we're done with the entries that
1443 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1444 // above) or we overflow.
1445 //
1446 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1447 // flag while there may still be some work to do. (See the comment at
1448 // the beginning of G1CMTask::do_marking_step() for those conditions -
1449 // one of which is reaching the specified time target.) It is only
1450 // when G1CMTask::do_marking_step() returns without setting the
1451 // has_aborted() flag that the marking step has completed.
1452 do {
1453 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1454 _task->do_marking_step(mark_step_duration_ms,
1455 false /* do_termination */,
1456 _is_serial);
1457 } while (_task->has_aborted() && !_cm->has_overflown());
1458 _ref_counter = _ref_counter_limit;
1459 }
1460 }
1461 };
1462
1463 // 'Drain' oop closure used by both serial and parallel reference processing.
1464 // Uses the G1CMTask associated with a given worker thread (for serial
1465 // reference processing the G1CMtask for worker 0 is used). Calls the
1466 // do_marking_step routine, with an unbelievably large timeout value,
1467 // to drain the marking data structures of the remaining entries
1468 // added by the 'keep alive' oop closure above.
1469
1470 class G1CMDrainMarkingStackClosure : public VoidClosure {
1471 G1ConcurrentMark* _cm;
1472 G1CMTask* _task;
1473 bool _is_serial;
1474 public:
1475 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1476 _cm(cm), _task(task), _is_serial(is_serial) {
1477 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1478 }
1479
1480 void do_void() {
1481 do {
1482 // We call G1CMTask::do_marking_step() to completely drain the local
1483 // and global marking stacks of entries pushed by the 'keep alive'
1484 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1485 //
1486 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1487 // if there's nothing more to do (i.e. we've completely drained the
1488 // entries that were pushed as a a result of applying the 'keep alive'
1489 // closure to the entries on the discovered ref lists) or we overflow
1490 // the global marking stack.
1491 //
1492 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1493 // flag while there may still be some work to do. (See the comment at
1494 // the beginning of G1CMTask::do_marking_step() for those conditions -
1495 // one of which is reaching the specified time target.) It is only
1496 // when G1CMTask::do_marking_step() returns without setting the
1497 // has_aborted() flag that the marking step has completed.
1498
1499 _task->do_marking_step(1000000000.0 /* something very large */,
1500 true /* do_termination */,
1501 _is_serial);
1502 } while (_task->has_aborted() && !_cm->has_overflown());
1503 }
1504 };
1505
1506 // Implementation of AbstractRefProcTaskExecutor for parallel
1507 // reference processing at the end of G1 concurrent marking
1508
1509 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
1510 private:
1511 G1CollectedHeap* _g1h;
1512 G1ConcurrentMark* _cm;
1513 WorkGang* _workers;
1514 uint _active_workers;
1515
1516 public:
1517 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1518 G1ConcurrentMark* cm,
1519 WorkGang* workers,
1520 uint n_workers) :
1521 _g1h(g1h), _cm(cm),
1522 _workers(workers), _active_workers(n_workers) { }
1523
1524 virtual void execute(ProcessTask& task, uint ergo_workers);
1525 };
1526
1527 class G1CMRefProcTaskProxy : public AbstractGangTask {
1528 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1529 ProcessTask& _proc_task;
1530 G1CollectedHeap* _g1h;
1531 G1ConcurrentMark* _cm;
1532
1533 public:
1534 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1535 G1CollectedHeap* g1h,
1536 G1ConcurrentMark* cm) :
1537 AbstractGangTask("Process reference objects in parallel"),
1538 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1539 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1540 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1541 }
1542
1543 virtual void work(uint worker_id) {
1544 ResourceMark rm;
1545 HandleMark hm;
1546 G1CMTask* task = _cm->task(worker_id);
1547 G1CMIsAliveClosure g1_is_alive(_g1h);
1548 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1549 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1550
1551 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1552 }
1553 };
1554
1555 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
1556 assert(_workers != NULL, "Need parallel worker threads.");
1557 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1558 assert(_workers->active_workers() >= ergo_workers,
1559 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)",
1560 ergo_workers, _workers->active_workers());
1561
1562 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1563
1564 // We need to reset the concurrency level before each
1565 // proxy task execution, so that the termination protocol
1566 // and overflow handling in G1CMTask::do_marking_step() knows
1567 // how many workers to wait for.
1568 _cm->set_concurrency(ergo_workers);
1569 _workers->run_task(&proc_task_proxy, ergo_workers);
1570 }
1571
1572 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) {
1573 ResourceMark rm;
1574 HandleMark hm;
1575
1576 // Is alive closure.
1577 G1CMIsAliveClosure g1_is_alive(_g1h);
1578
1579 // Inner scope to exclude the cleaning of the string table
1580 // from the displayed time.
1581 {
1582 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm);
1583
1584 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1585
1586 // See the comment in G1CollectedHeap::ref_processing_init()
1587 // about how reference processing currently works in G1.
1588
1589 // Set the soft reference policy
1590 rp->setup_policy(clear_all_soft_refs);
1591 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1592
1593 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1594 // in serial reference processing. Note these closures are also
1595 // used for serially processing (by the the current thread) the
1596 // JNI references during parallel reference processing.
1597 //
1598 // These closures do not need to synchronize with the worker
1599 // threads involved in parallel reference processing as these
1600 // instances are executed serially by the current thread (e.g.
1601 // reference processing is not multi-threaded and is thus
1602 // performed by the current thread instead of a gang worker).
1603 //
1604 // The gang tasks involved in parallel reference processing create
1605 // their own instances of these closures, which do their own
1606 // synchronization among themselves.
1607 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1608 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1609
1610 // We need at least one active thread. If reference processing
1611 // is not multi-threaded we use the current (VMThread) thread,
1612 // otherwise we use the work gang from the G1CollectedHeap and
1613 // we utilize all the worker threads we can.
1614 bool processing_is_mt = rp->processing_is_mt();
1615 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U);
1616 active_workers = clamp(active_workers, 1u, _max_num_tasks);
1617
1618 // Parallel processing task executor.
1619 G1CMRefProcTaskExecutor par_task_executor(_g1h, this,
1620 _g1h->workers(), active_workers);
1621 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1622
1623 // Set the concurrency level. The phase was already set prior to
1624 // executing the remark task.
1625 set_concurrency(active_workers);
1626
1627 // Set the degree of MT processing here. If the discovery was done MT,
1628 // the number of threads involved during discovery could differ from
1629 // the number of active workers. This is OK as long as the discovered
1630 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1631 rp->set_active_mt_degree(active_workers);
1632
1633 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues());
1634
1635 // Process the weak references.
1636 const ReferenceProcessorStats& stats =
1637 rp->process_discovered_references(&g1_is_alive,
1638 &g1_keep_alive,
1639 &g1_drain_mark_stack,
1640 executor,
1641 &pt);
1642 _gc_tracer_cm->report_gc_reference_stats(stats);
1643 pt.print_all_references();
1644
1645 // The do_oop work routines of the keep_alive and drain_marking_stack
1646 // oop closures will set the has_overflown flag if we overflow the
1647 // global marking stack.
1648
1649 assert(has_overflown() || _global_mark_stack.is_empty(),
1650 "Mark stack should be empty (unless it has overflown)");
1651
1652 assert(rp->num_queues() == active_workers, "why not");
1653
1654 rp->verify_no_references_recorded();
1655 assert(!rp->discovery_enabled(), "Post condition");
1656 }
1657
1658 if (has_overflown()) {
1659 // We can not trust g1_is_alive and the contents of the heap if the marking stack
1660 // overflowed while processing references. Exit the VM.
1661 fatal("Overflow during reference processing, can not continue. Please "
1662 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and "
1663 "restart.", MarkStackSizeMax);
1664 return;
1665 }
1666
1667 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1668
1669 {
1670 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm);
1671 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1);
1672 }
1673
1674 // Unload Klasses, String, Code Cache, etc.
1675 if (ClassUnloadingWithConcurrentMark) {
1676 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1677 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm);
1678 _g1h->complete_cleaning(&g1_is_alive, purged_classes);
1679 } else if (StringDedup::is_enabled()) {
1680 GCTraceTime(Debug, gc, phases) debug("String Deduplication", _gc_timer_cm);
1681 _g1h->string_dedup_cleaning(&g1_is_alive, NULL);
1682 }
1683 }
1684
1685 class G1PrecleanYieldClosure : public YieldClosure {
1686 G1ConcurrentMark* _cm;
1687
1688 public:
1689 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { }
1690
1691 virtual bool should_return() {
1692 return _cm->has_aborted();
1693 }
1694
1695 virtual bool should_return_fine_grain() {
1696 _cm->do_yield_check();
1697 return _cm->has_aborted();
1698 }
1699 };
1700
1701 void G1ConcurrentMark::preclean() {
1702 assert(G1UseReferencePrecleaning, "Precleaning must be enabled.");
1703
1704 SuspendibleThreadSetJoiner joiner;
1705
1706 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */);
1707 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */);
1708
1709 set_concurrency_and_phase(1, true);
1710
1711 G1PrecleanYieldClosure yield_cl(this);
1712
1713 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1714 // Precleaning is single threaded. Temporarily disable MT discovery.
1715 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false);
1716 rp->preclean_discovered_references(rp->is_alive_non_header(),
1717 &keep_alive,
1718 &drain_mark_stack,
1719 &yield_cl,
1720 _gc_timer_cm);
1721 }
1722
1723 // When sampling object counts, we already swapped the mark bitmaps, so we need to use
1724 // the prev bitmap determining liveness.
1725 class G1ObjectCountIsAliveClosure: public BoolObjectClosure {
1726 G1CollectedHeap* _g1h;
1727 public:
1728 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
1729
1730 bool do_object_b(oop obj) {
1731 HeapWord* addr = (HeapWord*)obj;
1732 return addr != NULL &&
1733 (!_g1h->is_in_g1_reserved(addr) || !_g1h->is_obj_dead(obj));
1734 }
1735 };
1736
1737 void G1ConcurrentMark::report_object_count(bool mark_completed) {
1738 // Depending on the completion of the marking liveness needs to be determined
1739 // using either the next or prev bitmap.
1740 if (mark_completed) {
1741 G1ObjectCountIsAliveClosure is_alive(_g1h);
1742 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1743 } else {
1744 G1CMIsAliveClosure is_alive(_g1h);
1745 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1746 }
1747 }
1748
1749
1750 void G1ConcurrentMark::swap_mark_bitmaps() {
1751 G1CMBitMap* temp = _prev_mark_bitmap;
1752 _prev_mark_bitmap = _next_mark_bitmap;
1753 _next_mark_bitmap = temp;
1754 _g1h->collector_state()->set_clearing_next_bitmap(true);
1755 }
1756
1757 // Closure for marking entries in SATB buffers.
1758 class G1CMSATBBufferClosure : public SATBBufferClosure {
1759 private:
1760 G1CMTask* _task;
1761 G1CollectedHeap* _g1h;
1762
1763 // This is very similar to G1CMTask::deal_with_reference, but with
1764 // more relaxed requirements for the argument, so this must be more
1765 // circumspect about treating the argument as an object.
1766 void do_entry(void* entry) const {
1767 _task->increment_refs_reached();
1768 oop const obj = static_cast<oop>(entry);
1769 _task->make_reference_grey(obj);
1770 }
1771
1772 public:
1773 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1774 : _task(task), _g1h(g1h) { }
1775
1776 virtual void do_buffer(void** buffer, size_t size) {
1777 for (size_t i = 0; i < size; ++i) {
1778 do_entry(buffer[i]);
1779 }
1780 }
1781 };
1782
1783 class G1RemarkThreadsClosure : public ThreadClosure {
1784 G1CMSATBBufferClosure _cm_satb_cl;
1785 G1CMOopClosure _cm_cl;
1786 MarkingCodeBlobClosure _code_cl;
1787 uintx _claim_token;
1788
1789 public:
1790 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1791 _cm_satb_cl(task, g1h),
1792 _cm_cl(g1h, task),
1793 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1794 _claim_token(Threads::thread_claim_token()) {}
1795
1796 void do_thread(Thread* thread) {
1797 if (thread->claim_threads_do(true, _claim_token)) {
1798 SATBMarkQueue& queue = G1ThreadLocalData::satb_mark_queue(thread);
1799 queue.apply_closure_and_empty(&_cm_satb_cl);
1800 if (thread->is_Java_thread()) {
1801 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1802 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1803 // * Alive if on the stack of an executing method
1804 // * Weakly reachable otherwise
1805 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1806 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1807 JavaThread* jt = (JavaThread*)thread;
1808 jt->nmethods_do(&_code_cl);
1809 }
1810 }
1811 }
1812 };
1813
1814 class G1CMRemarkTask : public AbstractGangTask {
1815 G1ConcurrentMark* _cm;
1816 public:
1817 void work(uint worker_id) {
1818 G1CMTask* task = _cm->task(worker_id);
1819 task->record_start_time();
1820 {
1821 ResourceMark rm;
1822 HandleMark hm;
1823
1824 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1825 Threads::threads_do(&threads_f);
1826 }
1827
1828 do {
1829 task->do_marking_step(1000000000.0 /* something very large */,
1830 true /* do_termination */,
1831 false /* is_serial */);
1832 } while (task->has_aborted() && !_cm->has_overflown());
1833 // If we overflow, then we do not want to restart. We instead
1834 // want to abort remark and do concurrent marking again.
1835 task->record_end_time();
1836 }
1837
1838 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1839 AbstractGangTask("Par Remark"), _cm(cm) {
1840 _cm->terminator()->reset_for_reuse(active_workers);
1841 }
1842 };
1843
1844 void G1ConcurrentMark::finalize_marking() {
1845 ResourceMark rm;
1846 HandleMark hm;
1847
1848 _g1h->ensure_parsability(false);
1849
1850 // this is remark, so we'll use up all active threads
1851 uint active_workers = _g1h->workers()->active_workers();
1852 set_concurrency_and_phase(active_workers, false /* concurrent */);
1853 // Leave _parallel_marking_threads at it's
1854 // value originally calculated in the G1ConcurrentMark
1855 // constructor and pass values of the active workers
1856 // through the gang in the task.
1857
1858 {
1859 StrongRootsScope srs(active_workers);
1860
1861 G1CMRemarkTask remarkTask(this, active_workers);
1862 // We will start all available threads, even if we decide that the
1863 // active_workers will be fewer. The extra ones will just bail out
1864 // immediately.
1865 _g1h->workers()->run_task(&remarkTask);
1866 }
1867
1868 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1869 guarantee(has_overflown() ||
1870 satb_mq_set.completed_buffers_num() == 0,
1871 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1872 BOOL_TO_STR(has_overflown()),
1873 satb_mq_set.completed_buffers_num());
1874
1875 print_stats();
1876 }
1877
1878 void G1ConcurrentMark::flush_all_task_caches() {
1879 size_t hits = 0;
1880 size_t misses = 0;
1881 for (uint i = 0; i < _max_num_tasks; i++) {
1882 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache();
1883 hits += stats.first;
1884 misses += stats.second;
1885 }
1886 size_t sum = hits + misses;
1887 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf",
1888 hits, misses, percent_of(hits, sum));
1889 }
1890
1891 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) {
1892 _prev_mark_bitmap->clear_range(mr);
1893 }
1894
1895 HeapRegion*
1896 G1ConcurrentMark::claim_region(uint worker_id) {
1897 // "checkpoint" the finger
1898 HeapWord* finger = _finger;
1899
1900 while (finger < _heap.end()) {
1901 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1902
1903 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1904 // Make sure that the reads below do not float before loading curr_region.
1905 OrderAccess::loadload();
1906 // Above heap_region_containing may return NULL as we always scan claim
1907 // until the end of the heap. In this case, just jump to the next region.
1908 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1909
1910 // Is the gap between reading the finger and doing the CAS too long?
1911 HeapWord* res = Atomic::cmpxchg(&_finger, finger, end);
1912 if (res == finger && curr_region != NULL) {
1913 // we succeeded
1914 HeapWord* bottom = curr_region->bottom();
1915 HeapWord* limit = curr_region->next_top_at_mark_start();
1916
1917 // notice that _finger == end cannot be guaranteed here since,
1918 // someone else might have moved the finger even further
1919 assert(_finger >= end, "the finger should have moved forward");
1920
1921 if (limit > bottom) {
1922 return curr_region;
1923 } else {
1924 assert(limit == bottom,
1925 "the region limit should be at bottom");
1926 // we return NULL and the caller should try calling
1927 // claim_region() again.
1928 return NULL;
1929 }
1930 } else {
1931 assert(_finger > finger, "the finger should have moved forward");
1932 // read it again
1933 finger = _finger;
1934 }
1935 }
1936
1937 return NULL;
1938 }
1939
1940 #ifndef PRODUCT
1941 class VerifyNoCSetOops {
1942 G1CollectedHeap* _g1h;
1943 const char* _phase;
1944 int _info;
1945
1946 public:
1947 VerifyNoCSetOops(const char* phase, int info = -1) :
1948 _g1h(G1CollectedHeap::heap()),
1949 _phase(phase),
1950 _info(info)
1951 { }
1952
1953 void operator()(G1TaskQueueEntry task_entry) const {
1954 if (task_entry.is_array_slice()) {
1955 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1956 return;
1957 }
1958 guarantee(oopDesc::is_oop(task_entry.obj()),
1959 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1960 p2i(task_entry.obj()), _phase, _info);
1961 HeapRegion* r = _g1h->heap_region_containing(task_entry.obj());
1962 guarantee(!(r->in_collection_set() || r->has_index_in_opt_cset()),
1963 "obj " PTR_FORMAT " from %s (%d) in region %u in (optional) collection set",
1964 p2i(task_entry.obj()), _phase, _info, r->hrm_index());
1965 }
1966 };
1967
1968 void G1ConcurrentMark::verify_no_collection_set_oops() {
1969 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1970 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
1971 return;
1972 }
1973
1974 // Verify entries on the global mark stack
1975 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
1976
1977 // Verify entries on the task queues
1978 for (uint i = 0; i < _max_num_tasks; ++i) {
1979 G1CMTaskQueue* queue = _task_queues->queue(i);
1980 queue->iterate(VerifyNoCSetOops("Queue", i));
1981 }
1982
1983 // Verify the global finger
1984 HeapWord* global_finger = finger();
1985 if (global_finger != NULL && global_finger < _heap.end()) {
1986 // Since we always iterate over all regions, we might get a NULL HeapRegion
1987 // here.
1988 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
1989 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
1990 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
1991 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
1992 }
1993
1994 // Verify the task fingers
1995 assert(_num_concurrent_workers <= _max_num_tasks, "sanity");
1996 for (uint i = 0; i < _num_concurrent_workers; ++i) {
1997 G1CMTask* task = _tasks[i];
1998 HeapWord* task_finger = task->finger();
1999 if (task_finger != NULL && task_finger < _heap.end()) {
2000 // See above note on the global finger verification.
2001 HeapRegion* r = _g1h->heap_region_containing(task_finger);
2002 guarantee(r == NULL || task_finger == r->bottom() ||
2003 !r->in_collection_set() || !r->has_index_in_opt_cset(),
2004 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2005 p2i(task_finger), HR_FORMAT_PARAMS(r));
2006 }
2007 }
2008 }
2009 #endif // PRODUCT
2010
2011 void G1ConcurrentMark::rebuild_rem_set_concurrently() {
2012 _g1h->rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset);
2013 }
2014
2015 void G1ConcurrentMark::print_stats() {
2016 if (!log_is_enabled(Debug, gc, stats)) {
2017 return;
2018 }
2019 log_debug(gc, stats)("---------------------------------------------------------------------");
2020 for (size_t i = 0; i < _num_active_tasks; ++i) {
2021 _tasks[i]->print_stats();
2022 log_debug(gc, stats)("---------------------------------------------------------------------");
2023 }
2024 }
2025
2026 void G1ConcurrentMark::concurrent_cycle_abort() {
2027 if (!cm_thread()->during_cycle() || _has_aborted) {
2028 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2029 return;
2030 }
2031
2032 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2033 // concurrent bitmap clearing.
2034 {
2035 GCTraceTime(Debug, gc) debug("Clear Next Bitmap");
2036 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false);
2037 }
2038 // Note we cannot clear the previous marking bitmap here
2039 // since VerifyDuringGC verifies the objects marked during
2040 // a full GC against the previous bitmap.
2041
2042 // Empty mark stack
2043 reset_marking_for_restart();
2044 for (uint i = 0; i < _max_num_tasks; ++i) {
2045 _tasks[i]->clear_region_fields();
2046 }
2047 _first_overflow_barrier_sync.abort();
2048 _second_overflow_barrier_sync.abort();
2049 _has_aborted = true;
2050
2051 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2052 satb_mq_set.abandon_partial_marking();
2053 // This can be called either during or outside marking, we'll read
2054 // the expected_active value from the SATB queue set.
2055 satb_mq_set.set_active_all_threads(
2056 false, /* new active value */
2057 satb_mq_set.is_active() /* expected_active */);
2058 }
2059
2060 static void print_ms_time_info(const char* prefix, const char* name,
2061 NumberSeq& ns) {
2062 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2063 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2064 if (ns.num() > 0) {
2065 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2066 prefix, ns.sd(), ns.maximum());
2067 }
2068 }
2069
2070 void G1ConcurrentMark::print_summary_info() {
2071 Log(gc, marking) log;
2072 if (!log.is_trace()) {
2073 return;
2074 }
2075
2076 log.trace(" Concurrent marking:");
2077 print_ms_time_info(" ", "init marks", _init_times);
2078 print_ms_time_info(" ", "remarks", _remark_times);
2079 {
2080 print_ms_time_info(" ", "final marks", _remark_mark_times);
2081 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2082
2083 }
2084 print_ms_time_info(" ", "cleanups", _cleanup_times);
2085 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2086 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2087 log.trace(" Total stop_world time = %8.2f s.",
2088 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2089 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2090 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum());
2091 }
2092
2093 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2094 _concurrent_workers->print_worker_threads_on(st);
2095 }
2096
2097 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2098 _concurrent_workers->threads_do(tc);
2099 }
2100
2101 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2102 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2103 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap));
2104 _prev_mark_bitmap->print_on_error(st, " Prev Bits: ");
2105 _next_mark_bitmap->print_on_error(st, " Next Bits: ");
2106 }
2107
2108 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2109 ReferenceProcessor* result = g1h->ref_processor_cm();
2110 assert(result != NULL, "CM reference processor should not be NULL");
2111 return result;
2112 }
2113
2114 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2115 G1CMTask* task)
2116 : MetadataVisitingOopIterateClosure(get_cm_oop_closure_ref_processor(g1h)),
2117 _g1h(g1h), _task(task)
2118 { }
2119
2120 void G1CMTask::setup_for_region(HeapRegion* hr) {
2121 assert(hr != NULL,
2122 "claim_region() should have filtered out NULL regions");
2123 _curr_region = hr;
2124 _finger = hr->bottom();
2125 update_region_limit();
2126 }
2127
2128 void G1CMTask::update_region_limit() {
2129 HeapRegion* hr = _curr_region;
2130 HeapWord* bottom = hr->bottom();
2131 HeapWord* limit = hr->next_top_at_mark_start();
2132
2133 if (limit == bottom) {
2134 // The region was collected underneath our feet.
2135 // We set the finger to bottom to ensure that the bitmap
2136 // iteration that will follow this will not do anything.
2137 // (this is not a condition that holds when we set the region up,
2138 // as the region is not supposed to be empty in the first place)
2139 _finger = bottom;
2140 } else if (limit >= _region_limit) {
2141 assert(limit >= _finger, "peace of mind");
2142 } else {
2143 assert(limit < _region_limit, "only way to get here");
2144 // This can happen under some pretty unusual circumstances. An
2145 // evacuation pause empties the region underneath our feet (NTAMS
2146 // at bottom). We then do some allocation in the region (NTAMS
2147 // stays at bottom), followed by the region being used as a GC
2148 // alloc region (NTAMS will move to top() and the objects
2149 // originally below it will be grayed). All objects now marked in
2150 // the region are explicitly grayed, if below the global finger,
2151 // and we do not need in fact to scan anything else. So, we simply
2152 // set _finger to be limit to ensure that the bitmap iteration
2153 // doesn't do anything.
2154 _finger = limit;
2155 }
2156
2157 _region_limit = limit;
2158 }
2159
2160 void G1CMTask::giveup_current_region() {
2161 assert(_curr_region != NULL, "invariant");
2162 clear_region_fields();
2163 }
2164
2165 void G1CMTask::clear_region_fields() {
2166 // Values for these three fields that indicate that we're not
2167 // holding on to a region.
2168 _curr_region = NULL;
2169 _finger = NULL;
2170 _region_limit = NULL;
2171 }
2172
2173 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2174 if (cm_oop_closure == NULL) {
2175 assert(_cm_oop_closure != NULL, "invariant");
2176 } else {
2177 assert(_cm_oop_closure == NULL, "invariant");
2178 }
2179 _cm_oop_closure = cm_oop_closure;
2180 }
2181
2182 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) {
2183 guarantee(next_mark_bitmap != NULL, "invariant");
2184 _next_mark_bitmap = next_mark_bitmap;
2185 clear_region_fields();
2186
2187 _calls = 0;
2188 _elapsed_time_ms = 0.0;
2189 _termination_time_ms = 0.0;
2190 _termination_start_time_ms = 0.0;
2191
2192 _mark_stats_cache.reset();
2193 }
2194
2195 bool G1CMTask::should_exit_termination() {
2196 if (!regular_clock_call()) {
2197 return true;
2198 }
2199
2200 // This is called when we are in the termination protocol. We should
2201 // quit if, for some reason, this task wants to abort or the global
2202 // stack is not empty (this means that we can get work from it).
2203 return !_cm->mark_stack_empty() || has_aborted();
2204 }
2205
2206 void G1CMTask::reached_limit() {
2207 assert(_words_scanned >= _words_scanned_limit ||
2208 _refs_reached >= _refs_reached_limit ,
2209 "shouldn't have been called otherwise");
2210 abort_marking_if_regular_check_fail();
2211 }
2212
2213 bool G1CMTask::regular_clock_call() {
2214 if (has_aborted()) {
2215 return false;
2216 }
2217
2218 // First, we need to recalculate the words scanned and refs reached
2219 // limits for the next clock call.
2220 recalculate_limits();
2221
2222 // During the regular clock call we do the following
2223
2224 // (1) If an overflow has been flagged, then we abort.
2225 if (_cm->has_overflown()) {
2226 return false;
2227 }
2228
2229 // If we are not concurrent (i.e. we're doing remark) we don't need
2230 // to check anything else. The other steps are only needed during
2231 // the concurrent marking phase.
2232 if (!_cm->concurrent()) {
2233 return true;
2234 }
2235
2236 // (2) If marking has been aborted for Full GC, then we also abort.
2237 if (_cm->has_aborted()) {
2238 return false;
2239 }
2240
2241 double curr_time_ms = os::elapsedVTime() * 1000.0;
2242
2243 // (4) We check whether we should yield. If we have to, then we abort.
2244 if (SuspendibleThreadSet::should_yield()) {
2245 // We should yield. To do this we abort the task. The caller is
2246 // responsible for yielding.
2247 return false;
2248 }
2249
2250 // (5) We check whether we've reached our time quota. If we have,
2251 // then we abort.
2252 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2253 if (elapsed_time_ms > _time_target_ms) {
2254 _has_timed_out = true;
2255 return false;
2256 }
2257
2258 // (6) Finally, we check whether there are enough completed STAB
2259 // buffers available for processing. If there are, we abort.
2260 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2261 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2262 // we do need to process SATB buffers, we'll abort and restart
2263 // the marking task to do so
2264 return false;
2265 }
2266 return true;
2267 }
2268
2269 void G1CMTask::recalculate_limits() {
2270 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2271 _words_scanned_limit = _real_words_scanned_limit;
2272
2273 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2274 _refs_reached_limit = _real_refs_reached_limit;
2275 }
2276
2277 void G1CMTask::decrease_limits() {
2278 // This is called when we believe that we're going to do an infrequent
2279 // operation which will increase the per byte scanned cost (i.e. move
2280 // entries to/from the global stack). It basically tries to decrease the
2281 // scanning limit so that the clock is called earlier.
2282
2283 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4;
2284 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4;
2285 }
2286
2287 void G1CMTask::move_entries_to_global_stack() {
2288 // Local array where we'll store the entries that will be popped
2289 // from the local queue.
2290 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2291
2292 size_t n = 0;
2293 G1TaskQueueEntry task_entry;
2294 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2295 buffer[n] = task_entry;
2296 ++n;
2297 }
2298 if (n < G1CMMarkStack::EntriesPerChunk) {
2299 buffer[n] = G1TaskQueueEntry();
2300 }
2301
2302 if (n > 0) {
2303 if (!_cm->mark_stack_push(buffer)) {
2304 set_has_aborted();
2305 }
2306 }
2307
2308 // This operation was quite expensive, so decrease the limits.
2309 decrease_limits();
2310 }
2311
2312 bool G1CMTask::get_entries_from_global_stack() {
2313 // Local array where we'll store the entries that will be popped
2314 // from the global stack.
2315 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2316
2317 if (!_cm->mark_stack_pop(buffer)) {
2318 return false;
2319 }
2320
2321 // We did actually pop at least one entry.
2322 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) {
2323 G1TaskQueueEntry task_entry = buffer[i];
2324 if (task_entry.is_null()) {
2325 break;
2326 }
2327 assert(task_entry.is_array_slice() || oopDesc::is_oop(task_entry.obj()), "Element " PTR_FORMAT " must be an array slice or oop", p2i(task_entry.obj()));
2328 bool success = _task_queue->push(task_entry);
2329 // We only call this when the local queue is empty or under a
2330 // given target limit. So, we do not expect this push to fail.
2331 assert(success, "invariant");
2332 }
2333
2334 // This operation was quite expensive, so decrease the limits
2335 decrease_limits();
2336 return true;
2337 }
2338
2339 void G1CMTask::drain_local_queue(bool partially) {
2340 if (has_aborted()) {
2341 return;
2342 }
2343
2344 // Decide what the target size is, depending whether we're going to
2345 // drain it partially (so that other tasks can steal if they run out
2346 // of things to do) or totally (at the very end).
2347 size_t target_size;
2348 if (partially) {
2349 target_size = MIN2((size_t)_task_queue->max_elems()/3, (size_t)GCDrainStackTargetSize);
2350 } else {
2351 target_size = 0;
2352 }
2353
2354 if (_task_queue->size() > target_size) {
2355 G1TaskQueueEntry entry;
2356 bool ret = _task_queue->pop_local(entry);
2357 while (ret) {
2358 scan_task_entry(entry);
2359 if (_task_queue->size() <= target_size || has_aborted()) {
2360 ret = false;
2361 } else {
2362 ret = _task_queue->pop_local(entry);
2363 }
2364 }
2365 }
2366 }
2367
2368 void G1CMTask::drain_global_stack(bool partially) {
2369 if (has_aborted()) {
2370 return;
2371 }
2372
2373 // We have a policy to drain the local queue before we attempt to
2374 // drain the global stack.
2375 assert(partially || _task_queue->size() == 0, "invariant");
2376
2377 // Decide what the target size is, depending whether we're going to
2378 // drain it partially (so that other tasks can steal if they run out
2379 // of things to do) or totally (at the very end).
2380 // Notice that when draining the global mark stack partially, due to the racyness
2381 // of the mark stack size update we might in fact drop below the target. But,
2382 // this is not a problem.
2383 // In case of total draining, we simply process until the global mark stack is
2384 // totally empty, disregarding the size counter.
2385 if (partially) {
2386 size_t const target_size = _cm->partial_mark_stack_size_target();
2387 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2388 if (get_entries_from_global_stack()) {
2389 drain_local_queue(partially);
2390 }
2391 }
2392 } else {
2393 while (!has_aborted() && get_entries_from_global_stack()) {
2394 drain_local_queue(partially);
2395 }
2396 }
2397 }
2398
2399 // SATB Queue has several assumptions on whether to call the par or
2400 // non-par versions of the methods. this is why some of the code is
2401 // replicated. We should really get rid of the single-threaded version
2402 // of the code to simplify things.
2403 void G1CMTask::drain_satb_buffers() {
2404 if (has_aborted()) {
2405 return;
2406 }
2407
2408 // We set this so that the regular clock knows that we're in the
2409 // middle of draining buffers and doesn't set the abort flag when it
2410 // notices that SATB buffers are available for draining. It'd be
2411 // very counter productive if it did that. :-)
2412 _draining_satb_buffers = true;
2413
2414 G1CMSATBBufferClosure satb_cl(this, _g1h);
2415 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2416
2417 // This keeps claiming and applying the closure to completed buffers
2418 // until we run out of buffers or we need to abort.
2419 while (!has_aborted() &&
2420 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2421 abort_marking_if_regular_check_fail();
2422 }
2423
2424 // Can't assert qset is empty here, even if not aborted. If concurrent,
2425 // some other thread might be adding to the queue. If not concurrent,
2426 // some other thread might have won the race for the last buffer, but
2427 // has not yet decremented the count.
2428
2429 _draining_satb_buffers = false;
2430
2431 // again, this was a potentially expensive operation, decrease the
2432 // limits to get the regular clock call early
2433 decrease_limits();
2434 }
2435
2436 void G1CMTask::clear_mark_stats_cache(uint region_idx) {
2437 _mark_stats_cache.reset(region_idx);
2438 }
2439
2440 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() {
2441 return _mark_stats_cache.evict_all();
2442 }
2443
2444 void G1CMTask::print_stats() {
2445 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls);
2446 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2447 _elapsed_time_ms, _termination_time_ms);
2448 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms",
2449 _step_times_ms.num(),
2450 _step_times_ms.avg(),
2451 _step_times_ms.sd(),
2452 _step_times_ms.maximum(),
2453 _step_times_ms.sum());
2454 size_t const hits = _mark_stats_cache.hits();
2455 size_t const misses = _mark_stats_cache.misses();
2456 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f",
2457 hits, misses, percent_of(hits, hits + misses));
2458 }
2459
2460 bool G1ConcurrentMark::try_stealing(uint worker_id, G1TaskQueueEntry& task_entry) {
2461 return _task_queues->steal(worker_id, task_entry);
2462 }
2463
2464 /*****************************************************************************
2465
2466 The do_marking_step(time_target_ms, ...) method is the building
2467 block of the parallel marking framework. It can be called in parallel
2468 with other invocations of do_marking_step() on different tasks
2469 (but only one per task, obviously) and concurrently with the
2470 mutator threads, or during remark, hence it eliminates the need
2471 for two versions of the code. When called during remark, it will
2472 pick up from where the task left off during the concurrent marking
2473 phase. Interestingly, tasks are also claimable during evacuation
2474 pauses too, since do_marking_step() ensures that it aborts before
2475 it needs to yield.
2476
2477 The data structures that it uses to do marking work are the
2478 following:
2479
2480 (1) Marking Bitmap. If there are gray objects that appear only
2481 on the bitmap (this happens either when dealing with an overflow
2482 or when the initial marking phase has simply marked the roots
2483 and didn't push them on the stack), then tasks claim heap
2484 regions whose bitmap they then scan to find gray objects. A
2485 global finger indicates where the end of the last claimed region
2486 is. A local finger indicates how far into the region a task has
2487 scanned. The two fingers are used to determine how to gray an
2488 object (i.e. whether simply marking it is OK, as it will be
2489 visited by a task in the future, or whether it needs to be also
2490 pushed on a stack).
2491
2492 (2) Local Queue. The local queue of the task which is accessed
2493 reasonably efficiently by the task. Other tasks can steal from
2494 it when they run out of work. Throughout the marking phase, a
2495 task attempts to keep its local queue short but not totally
2496 empty, so that entries are available for stealing by other
2497 tasks. Only when there is no more work, a task will totally
2498 drain its local queue.
2499
2500 (3) Global Mark Stack. This handles local queue overflow. During
2501 marking only sets of entries are moved between it and the local
2502 queues, as access to it requires a mutex and more fine-grain
2503 interaction with it which might cause contention. If it
2504 overflows, then the marking phase should restart and iterate
2505 over the bitmap to identify gray objects. Throughout the marking
2506 phase, tasks attempt to keep the global mark stack at a small
2507 length but not totally empty, so that entries are available for
2508 popping by other tasks. Only when there is no more work, tasks
2509 will totally drain the global mark stack.
2510
2511 (4) SATB Buffer Queue. This is where completed SATB buffers are
2512 made available. Buffers are regularly removed from this queue
2513 and scanned for roots, so that the queue doesn't get too
2514 long. During remark, all completed buffers are processed, as
2515 well as the filled in parts of any uncompleted buffers.
2516
2517 The do_marking_step() method tries to abort when the time target
2518 has been reached. There are a few other cases when the
2519 do_marking_step() method also aborts:
2520
2521 (1) When the marking phase has been aborted (after a Full GC).
2522
2523 (2) When a global overflow (on the global stack) has been
2524 triggered. Before the task aborts, it will actually sync up with
2525 the other tasks to ensure that all the marking data structures
2526 (local queues, stacks, fingers etc.) are re-initialized so that
2527 when do_marking_step() completes, the marking phase can
2528 immediately restart.
2529
2530 (3) When enough completed SATB buffers are available. The
2531 do_marking_step() method only tries to drain SATB buffers right
2532 at the beginning. So, if enough buffers are available, the
2533 marking step aborts and the SATB buffers are processed at
2534 the beginning of the next invocation.
2535
2536 (4) To yield. when we have to yield then we abort and yield
2537 right at the end of do_marking_step(). This saves us from a lot
2538 of hassle as, by yielding we might allow a Full GC. If this
2539 happens then objects will be compacted underneath our feet, the
2540 heap might shrink, etc. We save checking for this by just
2541 aborting and doing the yield right at the end.
2542
2543 From the above it follows that the do_marking_step() method should
2544 be called in a loop (or, otherwise, regularly) until it completes.
2545
2546 If a marking step completes without its has_aborted() flag being
2547 true, it means it has completed the current marking phase (and
2548 also all other marking tasks have done so and have all synced up).
2549
2550 A method called regular_clock_call() is invoked "regularly" (in
2551 sub ms intervals) throughout marking. It is this clock method that
2552 checks all the abort conditions which were mentioned above and
2553 decides when the task should abort. A work-based scheme is used to
2554 trigger this clock method: when the number of object words the
2555 marking phase has scanned or the number of references the marking
2556 phase has visited reach a given limit. Additional invocations to
2557 the method clock have been planted in a few other strategic places
2558 too. The initial reason for the clock method was to avoid calling
2559 vtime too regularly, as it is quite expensive. So, once it was in
2560 place, it was natural to piggy-back all the other conditions on it
2561 too and not constantly check them throughout the code.
2562
2563 If do_termination is true then do_marking_step will enter its
2564 termination protocol.
2565
2566 The value of is_serial must be true when do_marking_step is being
2567 called serially (i.e. by the VMThread) and do_marking_step should
2568 skip any synchronization in the termination and overflow code.
2569 Examples include the serial remark code and the serial reference
2570 processing closures.
2571
2572 The value of is_serial must be false when do_marking_step is
2573 being called by any of the worker threads in a work gang.
2574 Examples include the concurrent marking code (CMMarkingTask),
2575 the MT remark code, and the MT reference processing closures.
2576
2577 *****************************************************************************/
2578
2579 void G1CMTask::do_marking_step(double time_target_ms,
2580 bool do_termination,
2581 bool is_serial) {
2582 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2583
2584 _start_time_ms = os::elapsedVTime() * 1000.0;
2585
2586 // If do_stealing is true then do_marking_step will attempt to
2587 // steal work from the other G1CMTasks. It only makes sense to
2588 // enable stealing when the termination protocol is enabled
2589 // and do_marking_step() is not being called serially.
2590 bool do_stealing = do_termination && !is_serial;
2591
2592 G1Predictions const& predictor = _g1h->policy()->predictor();
2593 double diff_prediction_ms = predictor.get_new_lower_zero_bound_prediction(&_marking_step_diff_ms);
2594 _time_target_ms = time_target_ms - diff_prediction_ms;
2595
2596 // set up the variables that are used in the work-based scheme to
2597 // call the regular clock method
2598 _words_scanned = 0;
2599 _refs_reached = 0;
2600 recalculate_limits();
2601
2602 // clear all flags
2603 clear_has_aborted();
2604 _has_timed_out = false;
2605 _draining_satb_buffers = false;
2606
2607 ++_calls;
2608
2609 // Set up the bitmap and oop closures. Anything that uses them is
2610 // eventually called from this method, so it is OK to allocate these
2611 // statically.
2612 G1CMBitMapClosure bitmap_closure(this, _cm);
2613 G1CMOopClosure cm_oop_closure(_g1h, this);
2614 set_cm_oop_closure(&cm_oop_closure);
2615
2616 if (_cm->has_overflown()) {
2617 // This can happen if the mark stack overflows during a GC pause
2618 // and this task, after a yield point, restarts. We have to abort
2619 // as we need to get into the overflow protocol which happens
2620 // right at the end of this task.
2621 set_has_aborted();
2622 }
2623
2624 // First drain any available SATB buffers. After this, we will not
2625 // look at SATB buffers before the next invocation of this method.
2626 // If enough completed SATB buffers are queued up, the regular clock
2627 // will abort this task so that it restarts.
2628 drain_satb_buffers();
2629 // ...then partially drain the local queue and the global stack
2630 drain_local_queue(true);
2631 drain_global_stack(true);
2632
2633 do {
2634 if (!has_aborted() && _curr_region != NULL) {
2635 // This means that we're already holding on to a region.
2636 assert(_finger != NULL, "if region is not NULL, then the finger "
2637 "should not be NULL either");
2638
2639 // We might have restarted this task after an evacuation pause
2640 // which might have evacuated the region we're holding on to
2641 // underneath our feet. Let's read its limit again to make sure
2642 // that we do not iterate over a region of the heap that
2643 // contains garbage (update_region_limit() will also move
2644 // _finger to the start of the region if it is found empty).
2645 update_region_limit();
2646 // We will start from _finger not from the start of the region,
2647 // as we might be restarting this task after aborting half-way
2648 // through scanning this region. In this case, _finger points to
2649 // the address where we last found a marked object. If this is a
2650 // fresh region, _finger points to start().
2651 MemRegion mr = MemRegion(_finger, _region_limit);
2652
2653 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2654 "humongous regions should go around loop once only");
2655
2656 // Some special cases:
2657 // If the memory region is empty, we can just give up the region.
2658 // If the current region is humongous then we only need to check
2659 // the bitmap for the bit associated with the start of the object,
2660 // scan the object if it's live, and give up the region.
2661 // Otherwise, let's iterate over the bitmap of the part of the region
2662 // that is left.
2663 // If the iteration is successful, give up the region.
2664 if (mr.is_empty()) {
2665 giveup_current_region();
2666 abort_marking_if_regular_check_fail();
2667 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2668 if (_next_mark_bitmap->is_marked(mr.start())) {
2669 // The object is marked - apply the closure
2670 bitmap_closure.do_addr(mr.start());
2671 }
2672 // Even if this task aborted while scanning the humongous object
2673 // we can (and should) give up the current region.
2674 giveup_current_region();
2675 abort_marking_if_regular_check_fail();
2676 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) {
2677 giveup_current_region();
2678 abort_marking_if_regular_check_fail();
2679 } else {
2680 assert(has_aborted(), "currently the only way to do so");
2681 // The only way to abort the bitmap iteration is to return
2682 // false from the do_bit() method. However, inside the
2683 // do_bit() method we move the _finger to point to the
2684 // object currently being looked at. So, if we bail out, we
2685 // have definitely set _finger to something non-null.
2686 assert(_finger != NULL, "invariant");
2687
2688 // Region iteration was actually aborted. So now _finger
2689 // points to the address of the object we last scanned. If we
2690 // leave it there, when we restart this task, we will rescan
2691 // the object. It is easy to avoid this. We move the finger by
2692 // enough to point to the next possible object header.
2693 assert(_finger < _region_limit, "invariant");
2694 HeapWord* const new_finger = _finger + ((oop)_finger)->size();
2695 // Check if bitmap iteration was aborted while scanning the last object
2696 if (new_finger >= _region_limit) {
2697 giveup_current_region();
2698 } else {
2699 move_finger_to(new_finger);
2700 }
2701 }
2702 }
2703 // At this point we have either completed iterating over the
2704 // region we were holding on to, or we have aborted.
2705
2706 // We then partially drain the local queue and the global stack.
2707 // (Do we really need this?)
2708 drain_local_queue(true);
2709 drain_global_stack(true);
2710
2711 // Read the note on the claim_region() method on why it might
2712 // return NULL with potentially more regions available for
2713 // claiming and why we have to check out_of_regions() to determine
2714 // whether we're done or not.
2715 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2716 // We are going to try to claim a new region. We should have
2717 // given up on the previous one.
2718 // Separated the asserts so that we know which one fires.
2719 assert(_curr_region == NULL, "invariant");
2720 assert(_finger == NULL, "invariant");
2721 assert(_region_limit == NULL, "invariant");
2722 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2723 if (claimed_region != NULL) {
2724 // Yes, we managed to claim one
2725 setup_for_region(claimed_region);
2726 assert(_curr_region == claimed_region, "invariant");
2727 }
2728 // It is important to call the regular clock here. It might take
2729 // a while to claim a region if, for example, we hit a large
2730 // block of empty regions. So we need to call the regular clock
2731 // method once round the loop to make sure it's called
2732 // frequently enough.
2733 abort_marking_if_regular_check_fail();
2734 }
2735
2736 if (!has_aborted() && _curr_region == NULL) {
2737 assert(_cm->out_of_regions(),
2738 "at this point we should be out of regions");
2739 }
2740 } while ( _curr_region != NULL && !has_aborted());
2741
2742 if (!has_aborted()) {
2743 // We cannot check whether the global stack is empty, since other
2744 // tasks might be pushing objects to it concurrently.
2745 assert(_cm->out_of_regions(),
2746 "at this point we should be out of regions");
2747 // Try to reduce the number of available SATB buffers so that
2748 // remark has less work to do.
2749 drain_satb_buffers();
2750 }
2751
2752 // Since we've done everything else, we can now totally drain the
2753 // local queue and global stack.
2754 drain_local_queue(false);
2755 drain_global_stack(false);
2756
2757 // Attempt at work stealing from other task's queues.
2758 if (do_stealing && !has_aborted()) {
2759 // We have not aborted. This means that we have finished all that
2760 // we could. Let's try to do some stealing...
2761
2762 // We cannot check whether the global stack is empty, since other
2763 // tasks might be pushing objects to it concurrently.
2764 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2765 "only way to reach here");
2766 while (!has_aborted()) {
2767 G1TaskQueueEntry entry;
2768 if (_cm->try_stealing(_worker_id, entry)) {
2769 scan_task_entry(entry);
2770
2771 // And since we're towards the end, let's totally drain the
2772 // local queue and global stack.
2773 drain_local_queue(false);
2774 drain_global_stack(false);
2775 } else {
2776 break;
2777 }
2778 }
2779 }
2780
2781 // We still haven't aborted. Now, let's try to get into the
2782 // termination protocol.
2783 if (do_termination && !has_aborted()) {
2784 // We cannot check whether the global stack is empty, since other
2785 // tasks might be concurrently pushing objects on it.
2786 // Separated the asserts so that we know which one fires.
2787 assert(_cm->out_of_regions(), "only way to reach here");
2788 assert(_task_queue->size() == 0, "only way to reach here");
2789 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2790
2791 // The G1CMTask class also extends the TerminatorTerminator class,
2792 // hence its should_exit_termination() method will also decide
2793 // whether to exit the termination protocol or not.
2794 bool finished = (is_serial ||
2795 _cm->terminator()->offer_termination(this));
2796 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2797 _termination_time_ms +=
2798 termination_end_time_ms - _termination_start_time_ms;
2799
2800 if (finished) {
2801 // We're all done.
2802
2803 // We can now guarantee that the global stack is empty, since
2804 // all other tasks have finished. We separated the guarantees so
2805 // that, if a condition is false, we can immediately find out
2806 // which one.
2807 guarantee(_cm->out_of_regions(), "only way to reach here");
2808 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2809 guarantee(_task_queue->size() == 0, "only way to reach here");
2810 guarantee(!_cm->has_overflown(), "only way to reach here");
2811 guarantee(!has_aborted(), "should never happen if termination has completed");
2812 } else {
2813 // Apparently there's more work to do. Let's abort this task. It
2814 // will restart it and we can hopefully find more things to do.
2815 set_has_aborted();
2816 }
2817 }
2818
2819 // Mainly for debugging purposes to make sure that a pointer to the
2820 // closure which was statically allocated in this frame doesn't
2821 // escape it by accident.
2822 set_cm_oop_closure(NULL);
2823 double end_time_ms = os::elapsedVTime() * 1000.0;
2824 double elapsed_time_ms = end_time_ms - _start_time_ms;
2825 // Update the step history.
2826 _step_times_ms.add(elapsed_time_ms);
2827
2828 if (has_aborted()) {
2829 // The task was aborted for some reason.
2830 if (_has_timed_out) {
2831 double diff_ms = elapsed_time_ms - _time_target_ms;
2832 // Keep statistics of how well we did with respect to hitting
2833 // our target only if we actually timed out (if we aborted for
2834 // other reasons, then the results might get skewed).
2835 _marking_step_diff_ms.add(diff_ms);
2836 }
2837
2838 if (_cm->has_overflown()) {
2839 // This is the interesting one. We aborted because a global
2840 // overflow was raised. This means we have to restart the
2841 // marking phase and start iterating over regions. However, in
2842 // order to do this we have to make sure that all tasks stop
2843 // what they are doing and re-initialize in a safe manner. We
2844 // will achieve this with the use of two barrier sync points.
2845
2846 if (!is_serial) {
2847 // We only need to enter the sync barrier if being called
2848 // from a parallel context
2849 _cm->enter_first_sync_barrier(_worker_id);
2850
2851 // When we exit this sync barrier we know that all tasks have
2852 // stopped doing marking work. So, it's now safe to
2853 // re-initialize our data structures.
2854 }
2855
2856 clear_region_fields();
2857 flush_mark_stats_cache();
2858
2859 if (!is_serial) {
2860 // If we're executing the concurrent phase of marking, reset the marking
2861 // state; otherwise the marking state is reset after reference processing,
2862 // during the remark pause.
2863 // If we reset here as a result of an overflow during the remark we will
2864 // see assertion failures from any subsequent set_concurrency_and_phase()
2865 // calls.
2866 if (_cm->concurrent() && _worker_id == 0) {
2867 // Worker 0 is responsible for clearing the global data structures because
2868 // of an overflow. During STW we should not clear the overflow flag (in
2869 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit
2870 // method to abort the pause and restart concurrent marking.
2871 _cm->reset_marking_for_restart();
2872
2873 log_info(gc, marking)("Concurrent Mark reset for overflow");
2874 }
2875
2876 // ...and enter the second barrier.
2877 _cm->enter_second_sync_barrier(_worker_id);
2878 }
2879 // At this point, if we're during the concurrent phase of
2880 // marking, everything has been re-initialized and we're
2881 // ready to restart.
2882 }
2883 }
2884 }
2885
2886 G1CMTask::G1CMTask(uint worker_id,
2887 G1ConcurrentMark* cm,
2888 G1CMTaskQueue* task_queue,
2889 G1RegionMarkStats* mark_stats,
2890 uint max_regions) :
2891 _objArray_processor(this),
2892 _worker_id(worker_id),
2893 _g1h(G1CollectedHeap::heap()),
2894 _cm(cm),
2895 _next_mark_bitmap(NULL),
2896 _task_queue(task_queue),
2897 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize),
2898 _calls(0),
2899 _time_target_ms(0.0),
2900 _start_time_ms(0.0),
2901 _cm_oop_closure(NULL),
2902 _curr_region(NULL),
2903 _finger(NULL),
2904 _region_limit(NULL),
2905 _words_scanned(0),
2906 _words_scanned_limit(0),
2907 _real_words_scanned_limit(0),
2908 _refs_reached(0),
2909 _refs_reached_limit(0),
2910 _real_refs_reached_limit(0),
2911 _has_aborted(false),
2912 _has_timed_out(false),
2913 _draining_satb_buffers(false),
2914 _step_times_ms(),
2915 _elapsed_time_ms(0.0),
2916 _termination_time_ms(0.0),
2917 _termination_start_time_ms(0.0),
2918 _marking_step_diff_ms()
2919 {
2920 guarantee(task_queue != NULL, "invariant");
2921
2922 _marking_step_diff_ms.add(0.5);
2923 }
2924
2925 // These are formatting macros that are used below to ensure
2926 // consistent formatting. The *_H_* versions are used to format the
2927 // header for a particular value and they should be kept consistent
2928 // with the corresponding macro. Also note that most of the macros add
2929 // the necessary white space (as a prefix) which makes them a bit
2930 // easier to compose.
2931
2932 // All the output lines are prefixed with this string to be able to
2933 // identify them easily in a large log file.
2934 #define G1PPRL_LINE_PREFIX "###"
2935
2936 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
2937 #ifdef _LP64
2938 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
2939 #else // _LP64
2940 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
2941 #endif // _LP64
2942
2943 // For per-region info
2944 #define G1PPRL_TYPE_FORMAT " %-4s"
2945 #define G1PPRL_TYPE_H_FORMAT " %4s"
2946 #define G1PPRL_STATE_FORMAT " %-5s"
2947 #define G1PPRL_STATE_H_FORMAT " %5s"
2948 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
2949 #define G1PPRL_BYTE_H_FORMAT " %9s"
2950 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
2951 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
2952
2953 // For summary info
2954 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
2955 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
2956 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
2957 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
2958
2959 G1PrintRegionLivenessInfoClosure::G1PrintRegionLivenessInfoClosure(const char* phase_name) :
2960 _total_used_bytes(0), _total_capacity_bytes(0),
2961 _total_prev_live_bytes(0), _total_next_live_bytes(0),
2962 _total_remset_bytes(0), _total_strong_code_roots_bytes(0)
2963 {
2964 if (!log_is_enabled(Trace, gc, liveness)) {
2965 return;
2966 }
2967
2968 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2969 MemRegion g1_reserved = g1h->g1_reserved();
2970 double now = os::elapsedTime();
2971
2972 // Print the header of the output.
2973 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
2974 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
2975 G1PPRL_SUM_ADDR_FORMAT("reserved")
2976 G1PPRL_SUM_BYTE_FORMAT("region-size"),
2977 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
2978 HeapRegion::GrainBytes);
2979 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
2980 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2981 G1PPRL_TYPE_H_FORMAT
2982 G1PPRL_ADDR_BASE_H_FORMAT
2983 G1PPRL_BYTE_H_FORMAT
2984 G1PPRL_BYTE_H_FORMAT
2985 G1PPRL_BYTE_H_FORMAT
2986 G1PPRL_DOUBLE_H_FORMAT
2987 G1PPRL_BYTE_H_FORMAT
2988 G1PPRL_STATE_H_FORMAT
2989 G1PPRL_BYTE_H_FORMAT,
2990 "type", "address-range",
2991 "used", "prev-live", "next-live", "gc-eff",
2992 "remset", "state", "code-roots");
2993 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2994 G1PPRL_TYPE_H_FORMAT
2995 G1PPRL_ADDR_BASE_H_FORMAT
2996 G1PPRL_BYTE_H_FORMAT
2997 G1PPRL_BYTE_H_FORMAT
2998 G1PPRL_BYTE_H_FORMAT
2999 G1PPRL_DOUBLE_H_FORMAT
3000 G1PPRL_BYTE_H_FORMAT
3001 G1PPRL_STATE_H_FORMAT
3002 G1PPRL_BYTE_H_FORMAT,
3003 "", "",
3004 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3005 "(bytes)", "", "(bytes)");
3006 }
3007
3008 bool G1PrintRegionLivenessInfoClosure::do_heap_region(HeapRegion* r) {
3009 if (!log_is_enabled(Trace, gc, liveness)) {
3010 return false;
3011 }
3012
3013 const char* type = r->get_type_str();
3014 HeapWord* bottom = r->bottom();
3015 HeapWord* end = r->end();
3016 size_t capacity_bytes = r->capacity();
3017 size_t used_bytes = r->used();
3018 size_t prev_live_bytes = r->live_bytes();
3019 size_t next_live_bytes = r->next_live_bytes();
3020 double gc_eff = r->gc_efficiency();
3021 size_t remset_bytes = r->rem_set()->mem_size();
3022 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3023 const char* remset_type = r->rem_set()->get_short_state_str();
3024
3025 _total_used_bytes += used_bytes;
3026 _total_capacity_bytes += capacity_bytes;
3027 _total_prev_live_bytes += prev_live_bytes;
3028 _total_next_live_bytes += next_live_bytes;
3029 _total_remset_bytes += remset_bytes;
3030 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3031
3032 // Print a line for this particular region.
3033 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3034 G1PPRL_TYPE_FORMAT
3035 G1PPRL_ADDR_BASE_FORMAT
3036 G1PPRL_BYTE_FORMAT
3037 G1PPRL_BYTE_FORMAT
3038 G1PPRL_BYTE_FORMAT
3039 G1PPRL_DOUBLE_FORMAT
3040 G1PPRL_BYTE_FORMAT
3041 G1PPRL_STATE_FORMAT
3042 G1PPRL_BYTE_FORMAT,
3043 type, p2i(bottom), p2i(end),
3044 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3045 remset_bytes, remset_type, strong_code_roots_bytes);
3046
3047 return false;
3048 }
3049
3050 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3051 if (!log_is_enabled(Trace, gc, liveness)) {
3052 return;
3053 }
3054
3055 // add static memory usages to remembered set sizes
3056 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3057 // Print the footer of the output.
3058 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3059 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3060 " SUMMARY"
3061 G1PPRL_SUM_MB_FORMAT("capacity")
3062 G1PPRL_SUM_MB_PERC_FORMAT("used")
3063 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3064 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3065 G1PPRL_SUM_MB_FORMAT("remset")
3066 G1PPRL_SUM_MB_FORMAT("code-roots"),
3067 bytes_to_mb(_total_capacity_bytes),
3068 bytes_to_mb(_total_used_bytes),
3069 percent_of(_total_used_bytes, _total_capacity_bytes),
3070 bytes_to_mb(_total_prev_live_bytes),
3071 percent_of(_total_prev_live_bytes, _total_capacity_bytes),
3072 bytes_to_mb(_total_next_live_bytes),
3073 percent_of(_total_next_live_bytes, _total_capacity_bytes),
3074 bytes_to_mb(_total_remset_bytes),
3075 bytes_to_mb(_total_strong_code_roots_bytes));
3076 }
--- EOF ---