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 }