1 /*
2 * Copyright (c) 2015, 2018, 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 "gc/z/zBarrier.inline.hpp"
26 #include "gc/z/zMark.inline.hpp"
27 #include "gc/z/zMarkCache.inline.hpp"
28 #include "gc/z/zMarkStack.inline.hpp"
29 #include "gc/z/zMarkTerminate.inline.hpp"
30 #include "gc/z/zOopClosures.inline.hpp"
31 #include "gc/z/zPage.hpp"
32 #include "gc/z/zPageTable.inline.hpp"
33 #include "gc/z/zRootsIterator.hpp"
34 #include "gc/z/zStat.hpp"
35 #include "gc/z/zTask.hpp"
36 #include "gc/z/zThread.hpp"
37 #include "gc/z/zUtils.inline.hpp"
38 #include "gc/z/zWorkers.inline.hpp"
39 #include "logging/log.hpp"
40 #include "memory/iterator.inline.hpp"
41 #include "oops/objArrayOop.inline.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "runtime/atomic.hpp"
44 #include "runtime/handshake.hpp"
45 #include "runtime/orderAccess.hpp"
46 #include "runtime/prefetch.inline.hpp"
47 #include "runtime/thread.hpp"
48 #include "utilities/align.hpp"
49 #include "utilities/globalDefinitions.hpp"
50 #include "utilities/ticks.hpp"
51
52 static const ZStatSubPhase ZSubPhaseConcurrentMark("Concurrent Mark");
53 static const ZStatSubPhase ZSubPhaseConcurrentMarkTryFlush("Concurrent Mark Try Flush");
54 static const ZStatSubPhase ZSubPhaseConcurrentMarkIdle("Concurrent Mark Idle");
55 static const ZStatSubPhase ZSubPhaseConcurrentMarkTryTerminate("Concurrent Mark Try Terminate");
56 static const ZStatSubPhase ZSubPhaseMarkTryComplete("Pause Mark Try Complete");
57
58 ZMark::ZMark(ZWorkers* workers, ZPageTable* pagetable) :
59 _workers(workers),
60 _pagetable(pagetable),
61 _allocator(),
62 _stripes(),
63 _terminate(),
64 _work_terminateflush(true),
65 _work_nproactiveflush(0),
66 _work_nterminateflush(0),
67 _nproactiveflush(0),
68 _nterminateflush(0),
69 _ntrycomplete(0),
70 _ncontinue(0),
71 _nworkers(0) {}
72
73 bool ZMark::is_initialized() const {
74 return _allocator.is_initialized();
75 }
76
77 size_t ZMark::calculate_nstripes(uint nworkers) const {
78 // Calculate the number of stripes from the number of workers we use,
79 // where the number of stripes must be a power of two and we want to
80 // have at least one worker per stripe.
81 const size_t nstripes = ZUtils::round_down_power_of_2(nworkers);
82 return MIN2(nstripes, ZMarkStripesMax);
83 }
84
85 void ZMark::prepare_mark() {
86 // Increment global sequence number to invalidate
87 // marking information for all pages.
88 ZGlobalSeqNum++;
89
90 // Reset flush/continue counters
91 _nproactiveflush = 0;
92 _nterminateflush = 0;
93 _ntrycomplete = 0;
94 _ncontinue = 0;
95
96 // Set number of workers to use
97 _nworkers = _workers->nconcurrent();
98
99 // Set number of mark stripes to use, based on number
100 // of workers we will use in the concurrent mark phase.
101 const size_t nstripes = calculate_nstripes(_nworkers);
102 _stripes.set_nstripes(nstripes);
103
104 // Update statistics
105 ZStatMark::set_at_mark_start(nstripes);
106
107 // Print worker/stripe distribution
108 LogTarget(Debug, gc, marking) log;
109 if (log.is_enabled()) {
110 log.print("Mark Worker/Stripe Distribution");
111 for (uint worker_id = 0; worker_id < _nworkers; worker_id++) {
112 const ZMarkStripe* const stripe = _stripes.stripe_for_worker(_nworkers, worker_id);
113 const size_t stripe_id = _stripes.stripe_id(stripe);
114 log.print(" Worker %u(%u) -> Stripe " SIZE_FORMAT "(" SIZE_FORMAT ")",
115 worker_id, _nworkers, stripe_id, nstripes);
116 }
117 }
118 }
119
120 class ZMarkRootsIteratorClosure : public ZRootsIteratorClosure {
121 public:
122 virtual void do_thread(Thread* thread) {
123 ZRootsIteratorClosure::do_thread(thread);
124
125 // Update thread local address bad mask
126 ZThreadLocalData::set_address_bad_mask(thread, ZAddressBadMask);
127 }
128
129 virtual void do_oop(oop* p) {
130 ZBarrier::mark_barrier_on_root_oop_field(p);
131 }
132
133 virtual void do_oop(narrowOop* p) {
134 ShouldNotReachHere();
135 }
136 };
137
138 class ZMarkRootsTask : public ZTask {
139 private:
140 ZMark* const _mark;
141 ZRootsIterator _roots;
142
143 public:
144 ZMarkRootsTask(ZMark* mark) :
145 ZTask("ZMarkRootsTask"),
146 _mark(mark),
147 _roots() {}
148
149 virtual void work() {
150 ZMarkRootsIteratorClosure cl;
151 _roots.oops_do(&cl);
152
153 // Flush and free worker stacks. Needed here since
154 // the set of workers executing during root scanning
155 // can be different from the set of workers executing
156 // during mark.
157 _mark->flush_and_free();
158 }
159 };
160
161 void ZMark::start() {
162 // Verification
163 if (ZVerifyMarking) {
164 verify_all_stacks_empty();
165 }
166
167 // Prepare for concurrent mark
168 prepare_mark();
169
170 // Mark roots
171 ZMarkRootsTask task(this);
172 _workers->run_parallel(&task);
173 }
174
175 void ZMark::prepare_work() {
176 assert(_nworkers == _workers->nconcurrent(), "Invalid number of workers");
177
178 // Set number of active workers
179 _terminate.reset(_nworkers);
180
181 // Reset flush counters
182 _work_nproactiveflush = _work_nterminateflush = 0;
183 _work_terminateflush = true;
184 }
185
186 void ZMark::finish_work() {
187 // Accumulate proactive/terminate flush counters
188 _nproactiveflush += _work_nproactiveflush;
189 _nterminateflush += _work_nterminateflush;
190 }
191
192 bool ZMark::is_array(uintptr_t addr) const {
193 return ZOop::to_oop(addr)->is_objArray();
194 }
195
196 void ZMark::push_partial_array(uintptr_t addr, size_t size, bool finalizable) {
197 assert(is_aligned(addr, ZMarkPartialArrayMinSize), "Address misaligned");
198 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(Thread::current());
199 ZMarkStripe* const stripe = _stripes.stripe_for_addr(addr);
200 const uintptr_t offset = ZAddress::offset(addr) >> ZMarkPartialArrayMinSizeShift;
201 const uintptr_t length = size / oopSize;
202 const ZMarkStackEntry entry(offset, length, finalizable);
203
204 log_develop_trace(gc, marking)("Array push partial: " PTR_FORMAT " (" SIZE_FORMAT "), stripe: " SIZE_FORMAT,
205 addr, size, _stripes.stripe_id(stripe));
206
207 stacks->push(&_allocator, &_stripes, stripe, entry, false /* publish */);
208 }
209
210 void ZMark::follow_small_array(uintptr_t addr, size_t size, bool finalizable) {
211 assert(size <= ZMarkPartialArrayMinSize, "Too large, should be split");
212 const size_t length = size / oopSize;
213
214 log_develop_trace(gc, marking)("Array follow small: " PTR_FORMAT " (" SIZE_FORMAT ")", addr, size);
215
216 ZBarrier::mark_barrier_on_oop_array((oop*)addr, length, finalizable);
217 }
218
219 void ZMark::follow_large_array(uintptr_t addr, size_t size, bool finalizable) {
220 assert(size <= (size_t)arrayOopDesc::max_array_length(T_OBJECT) * oopSize, "Too large");
221 assert(size > ZMarkPartialArrayMinSize, "Too small, should not be split");
222 const uintptr_t start = addr;
223 const uintptr_t end = start + size;
224
225 // Calculate the aligned middle start/end/size, where the middle start
226 // should always be greater than the start (hence the +1 below) to make
227 // sure we always do some follow work, not just split the array into pieces.
228 const uintptr_t middle_start = align_up(start + 1, ZMarkPartialArrayMinSize);
229 const size_t middle_size = align_down(end - middle_start, ZMarkPartialArrayMinSize);
230 const uintptr_t middle_end = middle_start + middle_size;
231
232 log_develop_trace(gc, marking)("Array follow large: " PTR_FORMAT "-" PTR_FORMAT" (" SIZE_FORMAT "), "
233 "middle: " PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT ")",
234 start, end, size, middle_start, middle_end, middle_size);
235
236 // Push unaligned trailing part
237 if (end > middle_end) {
238 const uintptr_t trailing_addr = middle_end;
239 const size_t trailing_size = end - middle_end;
240 push_partial_array(trailing_addr, trailing_size, finalizable);
241 }
242
243 // Push aligned middle part(s)
244 uintptr_t partial_addr = middle_end;
245 while (partial_addr > middle_start) {
246 const size_t parts = 2;
247 const size_t partial_size = align_up((partial_addr - middle_start) / parts, ZMarkPartialArrayMinSize);
248 partial_addr -= partial_size;
249 push_partial_array(partial_addr, partial_size, finalizable);
250 }
251
252 // Follow leading part
253 assert(start < middle_start, "Miscalculated middle start");
254 const uintptr_t leading_addr = start;
255 const size_t leading_size = middle_start - start;
256 follow_small_array(leading_addr, leading_size, finalizable);
257 }
258
259 void ZMark::follow_array(uintptr_t addr, size_t size, bool finalizable) {
260 if (size <= ZMarkPartialArrayMinSize) {
261 follow_small_array(addr, size, finalizable);
262 } else {
263 follow_large_array(addr, size, finalizable);
264 }
265 }
266
267 void ZMark::follow_partial_array(ZMarkStackEntry entry, bool finalizable) {
268 const uintptr_t addr = ZAddress::good(entry.partial_array_offset() << ZMarkPartialArrayMinSizeShift);
269 const size_t size = entry.partial_array_length() * oopSize;
270
271 follow_array(addr, size, finalizable);
272 }
273
274 void ZMark::follow_array_object(objArrayOop obj, bool finalizable) {
275 const uintptr_t addr = (uintptr_t)obj->base();
276 const size_t size = (size_t)obj->length() * oopSize;
277
278 follow_array(addr, size, finalizable);
279 }
280
281 void ZMark::follow_object(oop obj, bool finalizable) {
282 if (finalizable) {
283 ZMarkBarrierOopClosure<true /* finalizable */> cl;
284 obj->oop_iterate(&cl);
285 } else {
286 ZMarkBarrierOopClosure<false /* finalizable */> cl;
287 obj->oop_iterate(&cl);
288 }
289 }
290
291 bool ZMark::try_mark_object(ZMarkCache* cache, uintptr_t addr, bool finalizable) {
292 ZPage* const page = _pagetable->get(addr);
293 if (page->is_allocating()) {
294 // Newly allocated objects are implicitly marked
295 return false;
296 }
297
298 // Try mark object
299 bool inc_live = false;
300 const bool success = page->mark_object(addr, finalizable, inc_live);
301 if (inc_live) {
302 // Update live objects/bytes for page. We use the aligned object
303 // size since that is the actual number of bytes used on the page
304 // and alignment paddings can never be reclaimed.
305 const size_t size = ZUtils::object_size(addr);
306 const size_t aligned_size = align_up(size, page->object_alignment());
307 cache->inc_live(page, aligned_size);
308 }
309
310 return success;
311 }
312
313 void ZMark::mark_and_follow(ZMarkCache* cache, ZMarkStackEntry entry) {
314 // Decode flags
315 const bool finalizable = entry.finalizable();
316 const bool partial_array = entry.partial_array();
317
318 if (partial_array) {
319 follow_partial_array(entry, finalizable);
320 return;
321 }
322
323 // Decode object address
324 const uintptr_t addr = entry.object_address();
325
326 if (!try_mark_object(cache, addr, finalizable)) {
327 // Already marked
328 return;
329 }
330
331 if (is_array(addr)) {
332 follow_array_object(objArrayOop(ZOop::to_oop(addr)), finalizable);
333 } else {
334 follow_object(ZOop::to_oop(addr), finalizable);
335 }
336 }
337
338 template <typename T>
339 bool ZMark::drain(ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks, ZMarkCache* cache, T* timeout) {
340 ZMarkStackEntry entry;
341
342 // Drain stripe stacks
343 while (stacks->pop(&_allocator, &_stripes, stripe, entry)) {
344 mark_and_follow(cache, entry);
345
346 // Check timeout
347 if (timeout->has_expired()) {
348 // Timeout
349 return false;
350 }
351 }
352
353 // Success
354 return true;
355 }
356
357 template <typename T>
358 bool ZMark::drain_and_flush(ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks, ZMarkCache* cache, T* timeout) {
359 const bool success = drain(stripe, stacks, cache, timeout);
360
361 // Flush and publish worker stacks
362 stacks->flush(&_allocator, &_stripes);
363
364 return success;
365 }
366
367 bool ZMark::try_steal(ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks) {
368 // Try to steal a stack from another stripe
369 for (ZMarkStripe* victim_stripe = _stripes.stripe_next(stripe);
370 victim_stripe != stripe;
371 victim_stripe = _stripes.stripe_next(victim_stripe)) {
372 ZMarkStack* const stack = victim_stripe->steal_stack();
373 if (stack != NULL) {
374 // Success, install the stolen stack
375 stacks->install(&_stripes, stripe, stack);
376 return true;
377 }
378 }
379
380 // Nothing to steal
381 return false;
382 }
383
384 void ZMark::idle() const {
385 ZStatTimer timer(ZSubPhaseConcurrentMarkIdle);
386 os::naked_short_sleep(1);
387 }
388
389 class ZMarkFlushAndFreeStacksClosure : public ThreadClosure {
390 private:
391 ZMark* const _mark;
392 bool _flushed;
393
394 public:
395 ZMarkFlushAndFreeStacksClosure(ZMark* mark) :
396 _mark(mark),
397 _flushed(false) {}
398
399 void do_thread(Thread* thread) {
400 if (_mark->flush_and_free(thread)) {
401 _flushed = true;
402 }
403 }
404
405 bool flushed() const {
406 return _flushed;
407 }
408 };
409
410 bool ZMark::flush(bool at_safepoint) {
411 ZMarkFlushAndFreeStacksClosure cl(this);
412 if (at_safepoint) {
413 Threads::threads_do(&cl);
414 } else {
415 Handshake::execute(&cl);
416 }
417
418 // Returns true if more work is available
419 return cl.flushed() || !_stripes.is_empty();
420 }
421
422 bool ZMark::try_flush(volatile size_t* nflush) {
423 // Only flush if handshakes are enabled
424 if (!ThreadLocalHandshakes) {
425 return false;
426 }
427
428 Atomic::inc(nflush);
429
430 ZStatTimer timer(ZSubPhaseConcurrentMarkTryFlush);
431 return flush(false /* at_safepoint */);
432 }
433
434 bool ZMark::try_proactive_flush() {
435 // Only do proactive flushes from worker 0
436 if (ZThread::worker_id() != 0) {
437 return false;
438 }
439
440 if (Atomic::load(&_work_nproactiveflush) == ZMarkProactiveFlushMax ||
441 Atomic::load(&_work_nterminateflush) != 0) {
442 // Limit reached or we're trying to terminate
443 return false;
444 }
445
446 return try_flush(&_work_nproactiveflush);
447 }
448
449 bool ZMark::try_terminate() {
450 ZStatTimer timer(ZSubPhaseConcurrentMarkTryTerminate);
451
452 if (_terminate.enter_stage0()) {
453 // Last thread entered stage 0, flush
454 if (Atomic::load(&_work_terminateflush) &&
455 Atomic::load(&_work_nterminateflush) != ZMarkTerminateFlushMax) {
456 // Exit stage 0 to allow other threads to continue marking
457 _terminate.exit_stage0();
458
459 // Flush before termination
460 if (!try_flush(&_work_nterminateflush)) {
461 // No more work available, skip further flush attempts
462 Atomic::store(false, &_work_terminateflush);
463 }
464
465 // Don't terminate, regardless of whether we successfully
466 // flushed out more work or not. We've already exited
467 // termination stage 0, to allow other threads to continue
468 // marking, so this thread has to return false and also
469 // make another round of attempted marking.
470 return false;
471 }
472 }
473
474 for (;;) {
475 if (_terminate.enter_stage1()) {
476 // Last thread entered stage 1, terminate
477 return true;
478 }
479
480 // Idle to give the other threads
481 // a chance to enter termination.
482 idle();
483
484 if (!_terminate.try_exit_stage1()) {
485 // All workers in stage 1, terminate
486 return true;
487 }
488
489 if (_terminate.try_exit_stage0()) {
490 // More work available, don't terminate
491 return false;
492 }
493 }
494 }
495
496 class ZMarkNoTimeout : public StackObj {
497 public:
498 bool has_expired() {
499 return false;
500 }
501 };
502
503 void ZMark::work_without_timeout(ZMarkCache* cache, ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks) {
504 ZStatTimer timer(ZSubPhaseConcurrentMark);
505 ZMarkNoTimeout no_timeout;
506
507 for (;;) {
508 drain_and_flush(stripe, stacks, cache, &no_timeout);
509
510 if (try_steal(stripe, stacks)) {
511 // Stole work
512 continue;
513 }
514
515 if (try_proactive_flush()) {
516 // Work available
517 continue;
518 }
519
520 if (try_terminate()) {
521 // Terminate
522 break;
523 }
524 }
525 }
526
527 class ZMarkTimeout : public StackObj {
528 private:
529 const Ticks _start;
530 const uint64_t _timeout;
531 const uint64_t _check_interval;
532 uint64_t _check_at;
533 uint64_t _check_count;
534 bool _expired;
535
536 public:
537 ZMarkTimeout(uint64_t timeout_in_millis) :
538 _start(Ticks::now()),
539 _timeout(_start.value() + TimeHelper::millis_to_counter(timeout_in_millis)),
540 _check_interval(200),
541 _check_at(_check_interval),
542 _check_count(0),
543 _expired(false) {}
544
545 ~ZMarkTimeout() {
546 const Tickspan duration = Ticks::now() - _start;
547 log_debug(gc, marking)("Mark With Timeout (%s): %s, " UINT64_FORMAT " oops, %.3fms",
548 ZThread::name(), _expired ? "Expired" : "Completed",
549 _check_count, TimeHelper::counter_to_millis(duration.value()));
550 }
551
552 bool has_expired() {
553 if (++_check_count == _check_at) {
554 _check_at += _check_interval;
555 if ((uint64_t)Ticks::now().value() >= _timeout) {
556 // Timeout
557 _expired = true;
558 }
559 }
560
561 return _expired;
562 }
563 };
564
565 void ZMark::work_with_timeout(ZMarkCache* cache, ZMarkStripe* stripe, ZMarkThreadLocalStacks* stacks, uint64_t timeout_in_millis) {
566 ZStatTimer timer(ZSubPhaseMarkTryComplete);
567 ZMarkTimeout timeout(timeout_in_millis);
568
569 for (;;) {
570 if (!drain_and_flush(stripe, stacks, cache, &timeout)) {
571 // Timed out
572 break;
573 }
574
575 if (try_steal(stripe, stacks)) {
576 // Stole work
577 continue;
578 }
579
580 // Terminate
581 break;
582 }
583 }
584
585 void ZMark::work(uint64_t timeout_in_millis) {
586 ZMarkCache cache(_stripes.nstripes());
587 ZMarkStripe* const stripe = _stripes.stripe_for_worker(_nworkers, ZThread::worker_id());
588 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(Thread::current());
589
590 if (timeout_in_millis == 0) {
591 work_without_timeout(&cache, stripe, stacks);
592 } else {
593 work_with_timeout(&cache, stripe, stacks, timeout_in_millis);
594 }
595
596 // Make sure stacks have been flushed
597 assert(stacks->is_empty(&_stripes), "Should be empty");
598
599 // Free remaining stacks
600 stacks->free(&_allocator);
601 }
602
603 class ZMarkTask : public ZTask {
604 private:
605 ZMark* const _mark;
606 const uint64_t _timeout_in_millis;
607
608 public:
609 ZMarkTask(ZMark* mark, uint64_t timeout_in_millis = 0) :
610 ZTask("ZMarkTask"),
611 _mark(mark),
612 _timeout_in_millis(timeout_in_millis) {
613 _mark->prepare_work();
614 }
615
616 ~ZMarkTask() {
617 _mark->finish_work();
618 }
619
620 virtual void work() {
621 _mark->work(_timeout_in_millis);
622 }
623 };
624
625 void ZMark::mark() {
626 ZMarkTask task(this);
627 _workers->run_concurrent(&task);
628 }
629
630 bool ZMark::try_complete() {
631 _ntrycomplete++;
632
633 // Use nconcurrent number of worker threads to maintain the
634 // worker/stripe distribution used during concurrent mark.
635 ZMarkTask task(this, ZMarkCompleteTimeout);
636 _workers->run_concurrent(&task);
637
638 // Successful if all stripes are empty
639 return _stripes.is_empty();
640 }
641
642 bool ZMark::try_end() {
643 // Flush all mark stacks
644 if (!flush(true /* at_safepoint */)) {
645 // Mark completed
646 return true;
647 }
648
649 // Try complete marking by doing a limited
650 // amount of mark work in this phase.
651 return try_complete();
652 }
653
654 bool ZMark::end() {
655 // Try end marking
656 if (!try_end()) {
657 // Mark not completed
658 _ncontinue++;
659 return false;
660 }
661
662 // Verification
663 if (ZVerifyMarking) {
664 verify_all_stacks_empty();
665 }
666
667 // Update statistics
668 ZStatMark::set_at_mark_end(_nproactiveflush, _nterminateflush, _ntrycomplete, _ncontinue);
669
670 // Mark completed
671 return true;
672 }
673
674 void ZMark::flush_and_free() {
675 Thread* const thread = Thread::current();
676 flush_and_free(thread);
677 }
678
679 bool ZMark::flush_and_free(Thread* thread) {
680 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(thread);
681 const bool flushed = stacks->flush(&_allocator, &_stripes);
682 stacks->free(&_allocator);
683 return flushed;
684 }
685
686 class ZVerifyMarkStacksEmptyClosure : public ThreadClosure {
687 private:
688 const ZMarkStripeSet* const _stripes;
689
690 public:
691 ZVerifyMarkStacksEmptyClosure(const ZMarkStripeSet* stripes) :
692 _stripes(stripes) {}
693
694 void do_thread(Thread* thread) {
695 ZMarkThreadLocalStacks* const stacks = ZThreadLocalData::stacks(thread);
696 guarantee(stacks->is_empty(_stripes), "Should be empty");
697 }
698 };
699
700 void ZMark::verify_all_stacks_empty() const {
701 // Verify thread stacks
702 ZVerifyMarkStacksEmptyClosure cl(&_stripes);
703 Threads::threads_do(&cl);
704
705 // Verify stripe stacks
706 guarantee(_stripes.is_empty(), "Should be empty");
707 }