1 /*
2 * Copyright (c) 2015, 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 #include "precompiled.hpp"
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "gc/z/zBarrier.inline.hpp"
27 #include "gc/z/zMark.inline.hpp"
28 #include "gc/z/zMarkCache.inline.hpp"
29 #include "gc/z/zMarkStack.inline.hpp"
30 #include "gc/z/zMarkTerminate.inline.hpp"
31 #include "gc/z/zOopClosures.inline.hpp"
32 #include "gc/z/zPage.hpp"
33 #include "gc/z/zPageTable.inline.hpp"
34 #include "gc/z/zRootsIterator.hpp"
35 #include "gc/z/zStat.hpp"
36 #include "gc/z/zTask.hpp"
37 #include "gc/z/zThread.inline.hpp"
38 #include "gc/z/zThreadLocalAllocBuffer.hpp"
39 #include "gc/z/zUtils.inline.hpp"
40 #include "gc/z/zWorkers.inline.hpp"
41 #include "logging/log.hpp"
42 #include "memory/iterator.inline.hpp"
43 #include "oops/objArrayOop.inline.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "runtime/atomic.hpp"
46 #include "runtime/handshake.hpp"
47 #include "runtime/orderAccess.hpp"
48 #include "runtime/prefetch.inline.hpp"
49 #include "runtime/thread.hpp"
50 #include "utilities/align.hpp"
51 #include "utilities/globalDefinitions.hpp"
52 #include "utilities/ticks.hpp"
53
54 static const ZStatSubPhase ZSubPhaseConcurrentMark("Concurrent Mark");
55 static const ZStatSubPhase ZSubPhaseConcurrentMarkTryFlush("Concurrent Mark Try Flush");
56 static const ZStatSubPhase ZSubPhaseConcurrentMarkIdle("Concurrent Mark Idle");
57 static const ZStatSubPhase ZSubPhaseConcurrentMarkTryTerminate("Concurrent Mark Try Terminate");
58 static const ZStatSubPhase ZSubPhaseMarkTryComplete("Pause Mark Try Complete");
59
60 ZMark::ZMark(ZWorkers* workers, ZPageTable* page_table) :
61 _workers(workers),
62 _page_table(page_table),
63 _allocator(),
64 _stripes(),
65 _terminate(),
66 _work_terminateflush(true),
67 _work_nproactiveflush(0),
68 _work_nterminateflush(0),
69 _nproactiveflush(0),
70 _nterminateflush(0),
71 _ntrycomplete(0),
72 _ncontinue(0),
73 _nworkers(0) {}
74
75 bool ZMark::is_initialized() const {
76 return _allocator.is_initialized();
77 }
78
79 size_t ZMark::calculate_nstripes(uint nworkers) const {
80 // Calculate the number of stripes from the number of workers we use,
81 // where the number of stripes must be a power of two and we want to
82 // have at least one worker per stripe.
83 const size_t nstripes = ZUtils::round_down_power_of_2(nworkers);
84 return MIN2(nstripes, ZMarkStripesMax);
85 }
86
87 void ZMark::prepare_mark() {
88 // Increment global sequence number to invalidate
89 // marking information for all pages.
90 ZGlobalSeqNum++;
91
92 // Reset flush/continue counters
93 _nproactiveflush = 0;
94 _nterminateflush = 0;
95 _ntrycomplete = 0;
96 _ncontinue = 0;
97
98 // Set number of workers to use
99 _nworkers = _workers->nconcurrent();
100
101 // Set number of mark stripes to use, based on number
102 // of workers we will use in the concurrent mark phase.
103 const size_t nstripes = calculate_nstripes(_nworkers);
104 _stripes.set_nstripes(nstripes);
105
106 // Update statistics
107 ZStatMark::set_at_mark_start(nstripes);
108
109 // Print worker/stripe distribution
110 LogTarget(Debug, gc, marking) log;
111 if (log.is_enabled()) {
112 log.print("Mark Worker/Stripe Distribution");
113 for (uint worker_id = 0; worker_id < _nworkers; worker_id++) {
114 const ZMarkStripe* const stripe = _stripes.stripe_for_worker(_nworkers, worker_id);
115 const size_t stripe_id = _stripes.stripe_id(stripe);
116 log.print(" Worker %u(%u) -> Stripe " SIZE_FORMAT "(" SIZE_FORMAT ")",
117 worker_id, _nworkers, stripe_id, nstripes);
118 }
119 }
120 }
121
122 class ZMarkRootsIteratorClosure : public ZRootsIteratorClosure {
123 public:
124 ZMarkRootsIteratorClosure() {
125 ZThreadLocalAllocBuffer::reset_statistics();
126 }
127
128 ~ZMarkRootsIteratorClosure() {
129 ZThreadLocalAllocBuffer::publish_statistics();
130 }
131
132 virtual void do_thread(Thread* thread) {
133 // Update thread local address bad mask
134 ZThreadLocalData::set_address_bad_mask(thread, ZAddressBadMask);
135
136 // Mark invisible root
137 ZThreadLocalData::do_invisible_root(thread, ZBarrier::mark_barrier_on_invisible_root_oop_field);
138
139 // Retire TLAB
140 ZThreadLocalAllocBuffer::retire(thread);
141 }
142
143 virtual void do_oop(oop* p) {
144 ZBarrier::mark_barrier_on_root_oop_field(p);
145 }
146
147 virtual void do_oop(narrowOop* p) {
148 ShouldNotReachHere();
149 }
150 };
151
152 class ZMarkRootsTask : public ZTask {
153 private:
154 ZMark* const _mark;
155 ZRootsIterator _roots;
156 ZMarkRootsIteratorClosure _cl;
157
158 public:
159 ZMarkRootsTask(ZMark* mark) :
160 ZTask("ZMarkRootsTask"),
161 _mark(mark),
162 _roots(false /* visit_jvmti_weak_export */, true /* disarm_nmethods */) {}
163
164 virtual void work() {
165 _roots.oops_do(&_cl);
166
167 // Flush and free worker stacks. Needed here since
168 // the set of workers executing during root scanning
169 // can be different from the set of workers executing
170 // during mark.
171 _mark->flush_and_free();
172 }
173 };
174
175 void ZMark::start() {
176 // Verification
177 if (ZVerifyMarking) {
178 verify_all_stacks_empty();
179 }
180
181 // Prepare for concurrent mark
182 prepare_mark();
183
184 // Mark roots
185 ZMarkRootsTask task(this);
186 _workers->run_parallel(&task);
187 }
188
189 void ZMark::prepare_work() {
190 assert(_nworkers == _workers->nconcurrent(), "Invalid number of workers");
191
192 // Set number of active workers
193 _terminate.reset(_nworkers);
194
195 // Reset flush counters
196 _work_nproactiveflush = _work_nterminateflush = 0;
197 _work_terminateflush = true;
198 }
199
200 void ZMark::finish_work() {
201 // Accumulate proactive/terminate flush counters
202 _nproactiveflush += _work_nproactiveflush;
203 _nterminateflush += _work_nterminateflush;
204 }
205
206 bool ZMark::is_array(uintptr_t addr) const {
207 return ZOop::from_address(addr)->is_objArray();
208 }
209
210 void ZMark::push_partial_array(uintptr_t addr, size_t size, bool finalizable) {
211 assert(is_aligned(addr, ZMarkPartialArrayMinSize), "Address misaligned");
212 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(Thread::current());
213 ZMarkStripe* const stripe = _stripes.stripe_for_addr(addr);
214 const uintptr_t offset = ZAddress::offset(addr) >> ZMarkPartialArrayMinSizeShift;
215 const uintptr_t length = size / oopSize;
216 const ZMarkStackEntry entry(offset, length, finalizable);
217
218 log_develop_trace(gc, marking)("Array push partial: " PTR_FORMAT " (" SIZE_FORMAT "), stripe: " SIZE_FORMAT,
219 addr, size, _stripes.stripe_id(stripe));
220
221 stacks->push(&_allocator, &_stripes, stripe, entry, false /* publish */);
222 }
223
224 void ZMark::follow_small_array(uintptr_t addr, size_t size, bool finalizable) {
225 assert(size <= ZMarkPartialArrayMinSize, "Too large, should be split");
226 const size_t length = size / oopSize;
227
228 log_develop_trace(gc, marking)("Array follow small: " PTR_FORMAT " (" SIZE_FORMAT ")", addr, size);
229
230 ZBarrier::mark_barrier_on_oop_array((oop*)addr, length, finalizable);
231 }
232
233 void ZMark::follow_large_array(uintptr_t addr, size_t size, bool finalizable) {
234 assert(size <= (size_t)arrayOopDesc::max_array_length(T_OBJECT) * oopSize, "Too large");
235 assert(size > ZMarkPartialArrayMinSize, "Too small, should not be split");
236 const uintptr_t start = addr;
237 const uintptr_t end = start + size;
238
239 // Calculate the aligned middle start/end/size, where the middle start
240 // should always be greater than the start (hence the +1 below) to make
241 // sure we always do some follow work, not just split the array into pieces.
242 const uintptr_t middle_start = align_up(start + 1, ZMarkPartialArrayMinSize);
243 const size_t middle_size = align_down(end - middle_start, ZMarkPartialArrayMinSize);
244 const uintptr_t middle_end = middle_start + middle_size;
245
246 log_develop_trace(gc, marking)("Array follow large: " PTR_FORMAT "-" PTR_FORMAT" (" SIZE_FORMAT "), "
247 "middle: " PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT ")",
248 start, end, size, middle_start, middle_end, middle_size);
249
250 // Push unaligned trailing part
251 if (end > middle_end) {
252 const uintptr_t trailing_addr = middle_end;
253 const size_t trailing_size = end - middle_end;
254 push_partial_array(trailing_addr, trailing_size, finalizable);
255 }
256
257 // Push aligned middle part(s)
258 uintptr_t partial_addr = middle_end;
259 while (partial_addr > middle_start) {
260 const size_t parts = 2;
261 const size_t partial_size = align_up((partial_addr - middle_start) / parts, ZMarkPartialArrayMinSize);
262 partial_addr -= partial_size;
263 push_partial_array(partial_addr, partial_size, finalizable);
264 }
265
266 // Follow leading part
267 assert(start < middle_start, "Miscalculated middle start");
268 const uintptr_t leading_addr = start;
269 const size_t leading_size = middle_start - start;
270 follow_small_array(leading_addr, leading_size, finalizable);
271 }
272
273 void ZMark::follow_array(uintptr_t addr, size_t size, bool finalizable) {
274 if (size <= ZMarkPartialArrayMinSize) {
275 follow_small_array(addr, size, finalizable);
276 } else {
277 follow_large_array(addr, size, finalizable);
278 }
279 }
280
281 void ZMark::follow_partial_array(ZMarkStackEntry entry, bool finalizable) {
282 const uintptr_t addr = ZAddress::good(entry.partial_array_offset() << ZMarkPartialArrayMinSizeShift);
283 const size_t size = entry.partial_array_length() * oopSize;
284
285 follow_array(addr, size, finalizable);
286 }
287
288 void ZMark::follow_array_object(objArrayOop obj, bool finalizable) {
289 if (finalizable) {
290 ZMarkBarrierOopClosure<true /* finalizable */> cl;
291 cl.do_klass(obj->klass());
292 } else {
293 ZMarkBarrierOopClosure<false /* finalizable */> cl;
294 cl.do_klass(obj->klass());
295 }
296
297 const uintptr_t addr = (uintptr_t)obj->base();
298 const size_t size = (size_t)obj->length() * oopSize;
299
300 follow_array(addr, size, finalizable);
301 }
302
303 void ZMark::follow_object(oop obj, bool finalizable) {
304 if (finalizable) {
305 ZMarkBarrierOopClosure<true /* finalizable */> cl;
306 obj->oop_iterate(&cl);
307 } else {
308 ZMarkBarrierOopClosure<false /* finalizable */> cl;
309 obj->oop_iterate(&cl);
310 }
311 }
312
313 bool ZMark::try_mark_object(ZMarkCache* cache, uintptr_t addr, bool finalizable) {
314 ZPage* const page = _page_table->get(addr);
315 if (page->is_allocating()) {
316 // Newly allocated objects are implicitly marked
317 return false;
318 }
319
320 // Try mark object
321 bool inc_live = false;
322 const bool success = page->mark_object(addr, finalizable, inc_live);
323 if (inc_live) {
324 // Update live objects/bytes for page. We use the aligned object
325 // size since that is the actual number of bytes used on the page
326 // and alignment paddings can never be reclaimed.
327 const size_t size = ZUtils::object_size(addr);
328 const size_t aligned_size = align_up(size, page->object_alignment());
329 cache->inc_live(page, aligned_size);
330 }
331
332 return success;
333 }
334
335 void ZMark::mark_and_follow(ZMarkCache* cache, ZMarkStackEntry entry) {
336 // Decode flags
337 const bool finalizable = entry.finalizable();
338 const bool partial_array = entry.partial_array();
339
340 if (partial_array) {
341 follow_partial_array(entry, finalizable);
342 return;
343 }
344
345 // Decode object address and follow flag
346 const uintptr_t addr = entry.object_address();
347
348 if (!try_mark_object(cache, addr, finalizable)) {
349 // Already marked
350 return;
351 }
352
353 if (is_array(addr)) {
354 // Decode follow flag
355 const bool follow = entry.follow();
356
357 // The follow flag is currently only relevant for object arrays
358 if (follow) {
359 follow_array_object(objArrayOop(ZOop::from_address(addr)), finalizable);
360 }
361 } else {
362 follow_object(ZOop::from_address(addr), finalizable);
363 }
364 }
365
366 template <typename T>
367 bool ZMark::drain(ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks, ZMarkCache* cache, T* timeout) {
368 ZMarkStackEntry entry;
369
370 // Drain stripe stacks
371 while (stacks->pop(&_allocator, &_stripes, stripe, entry)) {
372 mark_and_follow(cache, entry);
373
374 // Check timeout
375 if (timeout->has_expired()) {
376 // Timeout
377 return false;
378 }
379 }
380
381 // Success
382 return true;
383 }
384
385 template <typename T>
386 bool ZMark::drain_and_flush(ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks, ZMarkCache* cache, T* timeout) {
387 const bool success = drain(stripe, stacks, cache, timeout);
388
389 // Flush and publish worker stacks
390 stacks->flush(&_allocator, &_stripes);
391
392 return success;
393 }
394
395 bool ZMark::try_steal(ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks) {
396 // Try to steal a stack from another stripe
397 for (ZMarkStripe* victim_stripe = _stripes.stripe_next(stripe);
398 victim_stripe != stripe;
399 victim_stripe = _stripes.stripe_next(victim_stripe)) {
400 ZMarkStack* const stack = victim_stripe->steal_stack();
401 if (stack != NULL) {
402 // Success, install the stolen stack
403 stacks->install(&_stripes, stripe, stack);
404 return true;
405 }
406 }
407
408 // Nothing to steal
409 return false;
410 }
411
412 void ZMark::idle() const {
413 ZStatTimer timer(ZSubPhaseConcurrentMarkIdle);
414 os::naked_short_sleep(1);
415 }
416
417 class ZMarkFlushAndFreeStacksClosure : public ThreadClosure {
418 private:
419 ZMark* const _mark;
420 bool _flushed;
421
422 public:
423 ZMarkFlushAndFreeStacksClosure(ZMark* mark) :
424 _mark(mark),
425 _flushed(false) {}
426
427 void do_thread(Thread* thread) {
428 if (_mark->flush_and_free(thread)) {
429 _flushed = true;
430 }
431 }
432
433 bool flushed() const {
434 return _flushed;
435 }
436 };
437
438 bool ZMark::flush(bool at_safepoint) {
439 ZMarkFlushAndFreeStacksClosure cl(this);
440 if (at_safepoint) {
441 Threads::threads_do(&cl);
442 } else {
443 Handshake::execute(&cl);
444 }
445
446 // Returns true if more work is available
447 return cl.flushed() || !_stripes.is_empty();
448 }
449
450 bool ZMark::try_flush(volatile size_t* nflush) {
451 // Only flush if handshakes are enabled
452 if (!ThreadLocalHandshakes) {
453 return false;
454 }
455
456 Atomic::inc(nflush);
457
458 ZStatTimer timer(ZSubPhaseConcurrentMarkTryFlush);
459 return flush(false /* at_safepoint */);
460 }
461
462 bool ZMark::try_proactive_flush() {
463 // Only do proactive flushes from worker 0
464 if (ZThread::worker_id() != 0) {
465 return false;
466 }
467
468 if (Atomic::load(&_work_nproactiveflush) == ZMarkProactiveFlushMax ||
469 Atomic::load(&_work_nterminateflush) != 0) {
470 // Limit reached or we're trying to terminate
471 return false;
472 }
473
474 return try_flush(&_work_nproactiveflush);
475 }
476
477 bool ZMark::try_terminate() {
478 ZStatTimer timer(ZSubPhaseConcurrentMarkTryTerminate);
479
480 if (_terminate.enter_stage0()) {
481 // Last thread entered stage 0, flush
482 if (Atomic::load(&_work_terminateflush) &&
483 Atomic::load(&_work_nterminateflush) != ZMarkTerminateFlushMax) {
484 // Exit stage 0 to allow other threads to continue marking
485 _terminate.exit_stage0();
486
487 // Flush before termination
488 if (!try_flush(&_work_nterminateflush)) {
489 // No more work available, skip further flush attempts
490 Atomic::store(false, &_work_terminateflush);
491 }
492
493 // Don't terminate, regardless of whether we successfully
494 // flushed out more work or not. We've already exited
495 // termination stage 0, to allow other threads to continue
496 // marking, so this thread has to return false and also
497 // make another round of attempted marking.
498 return false;
499 }
500 }
501
502 for (;;) {
503 if (_terminate.enter_stage1()) {
504 // Last thread entered stage 1, terminate
505 return true;
506 }
507
508 // Idle to give the other threads
509 // a chance to enter termination.
510 idle();
511
512 if (!_terminate.try_exit_stage1()) {
513 // All workers in stage 1, terminate
514 return true;
515 }
516
517 if (_terminate.try_exit_stage0()) {
518 // More work available, don't terminate
519 return false;
520 }
521 }
522 }
523
524 class ZMarkNoTimeout : public StackObj {
525 public:
526 bool has_expired() {
527 return false;
528 }
529 };
530
531 void ZMark::work_without_timeout(ZMarkCache* cache, ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks) {
532 ZStatTimer timer(ZSubPhaseConcurrentMark);
533 ZMarkNoTimeout no_timeout;
534
535 for (;;) {
536 drain_and_flush(stripe, stacks, cache, &no_timeout);
537
538 if (try_steal(stripe, stacks)) {
539 // Stole work
540 continue;
541 }
542
543 if (try_proactive_flush()) {
544 // Work available
545 continue;
546 }
547
548 if (try_terminate()) {
549 // Terminate
550 break;
551 }
552 }
553 }
554
555 class ZMarkTimeout : public StackObj {
556 private:
557 const Ticks _start;
558 const uint64_t _timeout;
559 const uint64_t _check_interval;
560 uint64_t _check_at;
561 uint64_t _check_count;
562 bool _expired;
563
564 public:
565 ZMarkTimeout(uint64_t timeout_in_millis) :
566 _start(Ticks::now()),
567 _timeout(_start.value() + TimeHelper::millis_to_counter(timeout_in_millis)),
568 _check_interval(200),
569 _check_at(_check_interval),
570 _check_count(0),
571 _expired(false) {}
572
573 ~ZMarkTimeout() {
574 const Tickspan duration = Ticks::now() - _start;
575 log_debug(gc, marking)("Mark With Timeout (%s): %s, " UINT64_FORMAT " oops, %.3fms",
576 ZThread::name(), _expired ? "Expired" : "Completed",
577 _check_count, TimeHelper::counter_to_millis(duration.value()));
578 }
579
580 bool has_expired() {
581 if (++_check_count == _check_at) {
582 _check_at += _check_interval;
583 if ((uint64_t)Ticks::now().value() >= _timeout) {
584 // Timeout
585 _expired = true;
586 }
587 }
588
589 return _expired;
590 }
591 };
592
593 void ZMark::work_with_timeout(ZMarkCache* cache, ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks, uint64_t timeout_in_millis) {
594 ZStatTimer timer(ZSubPhaseMarkTryComplete);
595 ZMarkTimeout timeout(timeout_in_millis);
596
597 for (;;) {
598 if (!drain_and_flush(stripe, stacks, cache, &timeout)) {
599 // Timed out
600 break;
601 }
602
603 if (try_steal(stripe, stacks)) {
604 // Stole work
605 continue;
606 }
607
608 // Terminate
609 break;
610 }
611 }
612
613 void ZMark::work(uint64_t timeout_in_millis) {
614 ZMarkCache cache(_stripes.nstripes());
615 ZMarkStripe* const stripe = _stripes.stripe_for_worker(_nworkers, ZThread::worker_id());
616 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(Thread::current());
617
618 if (timeout_in_millis == 0) {
619 work_without_timeout(&cache, stripe, stacks);
620 } else {
621 work_with_timeout(&cache, stripe, stacks, timeout_in_millis);
622 }
623
624 // Make sure stacks have been flushed
625 assert(stacks->is_empty(&_stripes), "Should be empty");
626
627 // Free remaining stacks
628 stacks->free(&_allocator);
629 }
630
631 class ZMarkConcurrentRootsIteratorClosure : public ZRootsIteratorClosure {
632 public:
633 virtual void do_oop(oop* p) {
634 ZBarrier::mark_barrier_on_oop_field(p, false /* finalizable */);
635 }
636
637 virtual void do_oop(narrowOop* p) {
638 ShouldNotReachHere();
639 }
640 };
641
642
643 class ZMarkConcurrentRootsTask : public ZTask {
644 private:
645 SuspendibleThreadSetJoiner _sts_joiner;
646 ZConcurrentRootsIteratorClaimStrong _roots;
647 ZMarkConcurrentRootsIteratorClosure _cl;
648
649 public:
650 ZMarkConcurrentRootsTask(ZMark* mark) :
651 ZTask("ZMarkConcurrentRootsTask"),
652 _sts_joiner(),
653 _roots(),
654 _cl() {
655 ClassLoaderDataGraph_lock->lock();
656 }
657
658 ~ZMarkConcurrentRootsTask() {
659 ClassLoaderDataGraph_lock->unlock();
660 }
661
662 virtual void work() {
663 _roots.oops_do(&_cl);
664 }
665 };
666
667 class ZMarkTask : public ZTask {
668 private:
669 ZMark* const _mark;
670 const uint64_t _timeout_in_millis;
671
672 public:
673 ZMarkTask(ZMark* mark, uint64_t timeout_in_millis = 0) :
674 ZTask("ZMarkTask"),
675 _mark(mark),
676 _timeout_in_millis(timeout_in_millis) {
677 _mark->prepare_work();
678 }
679
680 ~ZMarkTask() {
681 _mark->finish_work();
682 }
683
684 virtual void work() {
685 _mark->work(_timeout_in_millis);
686 }
687 };
688
689 void ZMark::mark(bool initial) {
690 if (initial) {
691 ZMarkConcurrentRootsTask task(this);
692 _workers->run_concurrent(&task);
693 }
694
695 ZMarkTask task(this);
696 _workers->run_concurrent(&task);
697 }
698
699 bool ZMark::try_complete() {
700 _ntrycomplete++;
701
702 // Use nconcurrent number of worker threads to maintain the
703 // worker/stripe distribution used during concurrent mark.
704 ZMarkTask task(this, ZMarkCompleteTimeout);
705 _workers->run_concurrent(&task);
706
707 // Successful if all stripes are empty
708 return _stripes.is_empty();
709 }
710
711 bool ZMark::try_end() {
712 // Flush all mark stacks
713 if (!flush(true /* at_safepoint */)) {
714 // Mark completed
715 return true;
716 }
717
718 // Try complete marking by doing a limited
719 // amount of mark work in this phase.
720 return try_complete();
721 }
722
723 bool ZMark::end() {
724 // Try end marking
725 if (!try_end()) {
726 // Mark not completed
727 _ncontinue++;
728 return false;
729 }
730
731 // Verification
732 if (ZVerifyMarking) {
733 verify_all_stacks_empty();
734 }
735
736 // Update statistics
737 ZStatMark::set_at_mark_end(_nproactiveflush, _nterminateflush, _ntrycomplete, _ncontinue);
738
739 // Mark completed
740 return true;
741 }
742
743 void ZMark::flush_and_free() {
744 Thread* const thread = Thread::current();
745 flush_and_free(thread);
746 }
747
748 bool ZMark::flush_and_free(Thread* thread) {
749 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(thread);
750 const bool flushed = stacks->flush(&_allocator, &_stripes);
751 stacks->free(&_allocator);
752 return flushed;
753 }
754
755 class ZVerifyMarkStacksEmptyClosure : public ThreadClosure {
756 private:
757 const ZMarkStripeSet* const _stripes;
758
759 public:
760 ZVerifyMarkStacksEmptyClosure(const ZMarkStripeSet* stripes) :
761 _stripes(stripes) {}
762
763 void do_thread(Thread* thread) {
764 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(thread);
765 guarantee(stacks->is_empty(_stripes), "Should be empty");
766 }
767 };
768
769 void ZMark::verify_all_stacks_empty() const {
770 // Verify thread stacks
771 ZVerifyMarkStacksEmptyClosure cl(&_stripes);
772 Threads::threads_do(&cl);
773
774 // Verify stripe stacks
775 guarantee(_stripes.is_empty(), "Should be empty");
776 }