1 /* 2 * Copyright (c) 2013, 2020, Red Hat, Inc. 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 27 #include "classfile/symbolTable.hpp" 28 #include "classfile/systemDictionary.hpp" 29 #include "code/codeCache.hpp" 30 31 #include "gc/shared/weakProcessor.inline.hpp" 32 #include "gc/shared/gcTimer.hpp" 33 #include "gc/shared/referenceProcessor.hpp" 34 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 35 #include "gc/shared/strongRootsScope.hpp" 36 37 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp" 38 #include "gc/shenandoah/shenandoahClosures.inline.hpp" 39 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp" 40 #include "gc/shenandoah/shenandoahMarkCompact.hpp" 41 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 42 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp" 43 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp" 44 #include "gc/shenandoah/shenandoahPhaseTimings.hpp" 45 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp" 46 #include "gc/shenandoah/shenandoahUtils.hpp" 47 48 #include "memory/iterator.inline.hpp" 49 #include "memory/metaspace.hpp" 50 #include "memory/resourceArea.hpp" 51 #include "oops/oop.inline.hpp" 52 #include "runtime/handles.inline.hpp" 53 54 template<UpdateRefsMode UPDATE_REFS> 55 class ShenandoahInitMarkRootsClosure : public OopClosure { 56 private: 57 ShenandoahObjToScanQueue* _queue; 58 ShenandoahHeap* _heap; 59 ShenandoahMarkingContext* const _mark_context; 60 61 template <class T> 62 inline void do_oop_work(T* p) { 63 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, NO_DEDUP>(p, _heap, _queue, _mark_context); 64 } 65 66 public: 67 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) : 68 _queue(q), 69 _heap(ShenandoahHeap::heap()), 70 _mark_context(_heap->marking_context()) {}; 71 72 void do_oop(narrowOop* p) { do_oop_work(p); } 73 void do_oop(oop* p) { do_oop_work(p); } 74 }; 75 76 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) : 77 MetadataVisitingOopIterateClosure(rp), 78 _queue(q), 79 _heap(ShenandoahHeap::heap()), 80 _mark_context(_heap->marking_context()) 81 { } 82 83 template<UpdateRefsMode UPDATE_REFS> 84 class ShenandoahInitMarkRootsTask : public AbstractGangTask { 85 private: 86 ShenandoahAllRootScanner* _rp; 87 public: 88 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp) : 89 AbstractGangTask("Shenandoah init mark roots task"), 90 _rp(rp) { 91 } 92 93 void work(uint worker_id) { 94 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 95 ShenandoahParallelWorkerSession worker_session(worker_id); 96 97 ShenandoahHeap* heap = ShenandoahHeap::heap(); 98 ShenandoahObjToScanQueueSet* queues = heap->concurrent_mark()->task_queues(); 99 assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id); 100 101 ShenandoahObjToScanQueue* q = queues->queue(worker_id); 102 103 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q); 104 do_work(heap, &mark_cl, worker_id); 105 } 106 107 private: 108 void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) { 109 // The rationale for selecting the roots to scan is as follows: 110 // a. With unload_classes = true, we only want to scan the actual strong roots from the 111 // code cache. This will allow us to identify the dead classes, unload them, *and* 112 // invalidate the relevant code cache blobs. This could be only done together with 113 // class unloading. 114 // b. With unload_classes = false, we have to nominally retain all the references from code 115 // cache, because there could be the case of embedded class/oop in the generated code, 116 // which we will never visit during mark. Without code cache invalidation, as in (a), 117 // we risk executing that code cache blob, and crashing. 118 if (heap->unload_classes()) { 119 _rp->strong_roots_do(worker_id, oops); 120 } else { 121 _rp->roots_do(worker_id, oops); 122 } 123 } 124 }; 125 126 class ShenandoahUpdateRootsTask : public AbstractGangTask { 127 private: 128 ShenandoahRootUpdater* _root_updater; 129 bool _check_alive; 130 public: 131 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater, bool check_alive) : 132 AbstractGangTask("Shenandoah update roots task"), 133 _root_updater(root_updater), 134 _check_alive(check_alive){ 135 } 136 137 void work(uint worker_id) { 138 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 139 ShenandoahParallelWorkerSession worker_session(worker_id); 140 141 ShenandoahHeap* heap = ShenandoahHeap::heap(); 142 ShenandoahUpdateRefsClosure cl; 143 if (_check_alive) { 144 ShenandoahForwardedIsAliveClosure is_alive; 145 _root_updater->roots_do<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>(worker_id, &is_alive, &cl); 146 } else { 147 AlwaysTrueClosure always_true;; 148 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl); 149 } 150 } 151 }; 152 153 class ShenandoahConcurrentMarkingTask : public AbstractGangTask { 154 private: 155 ShenandoahConcurrentMark* _cm; 156 TaskTerminator* _terminator; 157 158 public: 159 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) : 160 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) { 161 } 162 163 void work(uint worker_id) { 164 ShenandoahHeap* heap = ShenandoahHeap::heap(); 165 ShenandoahConcurrentWorkerSession worker_session(worker_id); 166 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers); 167 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id); 168 ReferenceProcessor* rp; 169 if (heap->process_references()) { 170 rp = heap->ref_processor(); 171 shenandoah_assert_rp_isalive_installed(); 172 } else { 173 rp = NULL; 174 } 175 176 _cm->concurrent_scan_code_roots(worker_id, rp); 177 _cm->mark_loop(worker_id, _terminator, rp, 178 true, // cancellable 179 ShenandoahStringDedup::is_enabled()); // perform string dedup 180 } 181 }; 182 183 class ShenandoahSATBAndRemarkCodeRootsThreadsClosure : public ThreadClosure { 184 private: 185 ShenandoahSATBBufferClosure* _satb_cl; 186 MarkingCodeBlobClosure* _code_cl; 187 uintx _claim_token; 188 189 public: 190 ShenandoahSATBAndRemarkCodeRootsThreadsClosure(ShenandoahSATBBufferClosure* satb_cl, MarkingCodeBlobClosure* code_cl) : 191 _satb_cl(satb_cl), _code_cl(code_cl), 192 _claim_token(Threads::thread_claim_token()) {} 193 194 void do_thread(Thread* thread) { 195 if (thread->claim_threads_do(true, _claim_token)) { 196 ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl); 197 if (_code_cl != NULL && thread->is_Java_thread()) { 198 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 199 // however the liveness of oops reachable from nmethods have very complex lifecycles: 200 // * Alive if on the stack of an executing method 201 // * Weakly reachable otherwise 202 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 203 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 204 JavaThread* jt = (JavaThread*)thread; 205 jt->nmethods_do(_code_cl); 206 } 207 } 208 } 209 }; 210 211 class ShenandoahFinalMarkingTask : public AbstractGangTask { 212 private: 213 ShenandoahConcurrentMark* _cm; 214 TaskTerminator* _terminator; 215 bool _dedup_string; 216 217 public: 218 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) : 219 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) { 220 } 221 222 void work(uint worker_id) { 223 ShenandoahHeap* heap = ShenandoahHeap::heap(); 224 225 ShenandoahParallelWorkerSession worker_session(worker_id); 226 ReferenceProcessor* rp; 227 if (heap->process_references()) { 228 rp = heap->ref_processor(); 229 shenandoah_assert_rp_isalive_installed(); 230 } else { 231 rp = NULL; 232 } 233 234 // First drain remaining SATB buffers. 235 // Notice that this is not strictly necessary for mark-compact. But since 236 // it requires a StrongRootsScope around the task, we need to claim the 237 // threads, and performance-wise it doesn't really matter. Adds about 1ms to 238 // full-gc. 239 { 240 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id); 241 242 ShenandoahSATBBufferClosure cl(q); 243 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set(); 244 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)); 245 246 if (heap->unload_classes() && !ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) { 247 if (heap->has_forwarded_objects()) { 248 ShenandoahMarkResolveRefsClosure resolve_mark_cl(q, rp); 249 MarkingCodeBlobClosure blobsCl(&resolve_mark_cl, !CodeBlobToOopClosure::FixRelocations); 250 ShenandoahSATBAndRemarkCodeRootsThreadsClosure tc(&cl, &blobsCl); 251 Threads::threads_do(&tc); 252 } else { 253 ShenandoahMarkRefsClosure mark_cl(q, rp); 254 MarkingCodeBlobClosure blobsCl(&mark_cl, !CodeBlobToOopClosure::FixRelocations); 255 ShenandoahSATBAndRemarkCodeRootsThreadsClosure tc(&cl, &blobsCl); 256 Threads::threads_do(&tc); 257 } 258 } else { 259 ShenandoahSATBAndRemarkCodeRootsThreadsClosure tc(&cl, NULL); 260 Threads::threads_do(&tc); 261 } 262 } 263 264 if (heap->is_degenerated_gc_in_progress()) { 265 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned, 266 // let's check here. 267 _cm->concurrent_scan_code_roots(worker_id, rp); 268 } 269 270 _cm->mark_loop(worker_id, _terminator, rp, 271 false, // not cancellable 272 _dedup_string); 273 274 assert(_cm->task_queues()->is_empty(), "Should be empty"); 275 } 276 }; 277 278 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) { 279 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread"); 280 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 281 282 ShenandoahHeap* heap = ShenandoahHeap::heap(); 283 284 ShenandoahGCPhase phase(root_phase); 285 286 WorkGang* workers = heap->workers(); 287 uint nworkers = workers->active_workers(); 288 289 assert(nworkers <= task_queues()->size(), "Just check"); 290 291 ShenandoahAllRootScanner root_proc(nworkers, root_phase); 292 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats()); 293 task_queues()->reserve(nworkers); 294 295 if (heap->has_forwarded_objects()) { 296 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc); 297 workers->run_task(&mark_roots); 298 } else { 299 // No need to update references, which means the heap is stable. 300 // Can save time not walking through forwarding pointers. 301 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc); 302 workers->run_task(&mark_roots); 303 } 304 305 if (ShenandoahConcurrentScanCodeRoots) { 306 clear_claim_codecache(); 307 } 308 } 309 310 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) { 311 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 312 assert(root_phase == ShenandoahPhaseTimings::full_gc_roots || 313 root_phase == ShenandoahPhaseTimings::degen_gc_update_roots, 314 "Only for these phases"); 315 316 ShenandoahGCPhase phase(root_phase); 317 318 bool check_alive = root_phase == ShenandoahPhaseTimings::degen_gc_update_roots; 319 320 #if COMPILER2_OR_JVMCI 321 DerivedPointerTable::clear(); 322 #endif 323 324 uint nworkers = _heap->workers()->active_workers(); 325 326 ShenandoahRootUpdater root_updater(nworkers, root_phase); 327 ShenandoahUpdateRootsTask update_roots(&root_updater, check_alive); 328 _heap->workers()->run_task(&update_roots); 329 330 #if COMPILER2_OR_JVMCI 331 DerivedPointerTable::update_pointers(); 332 #endif 333 } 334 335 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask { 336 private: 337 ShenandoahThreadRoots _thread_roots; 338 ShenandoahPhaseTimings::Phase _phase; 339 ShenandoahGCWorkerPhase _worker_phase; 340 public: 341 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) : 342 AbstractGangTask("Shenandoah Update Thread Roots"), 343 _thread_roots(is_par), 344 _phase(phase), 345 _worker_phase(phase) {} 346 347 void work(uint worker_id) { 348 ShenandoahUpdateRefsClosure cl; 349 _thread_roots.oops_do(&cl, NULL, worker_id); 350 } 351 }; 352 353 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) { 354 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 355 356 ShenandoahGCPhase phase(root_phase); 357 358 #if COMPILER2_OR_JVMCI 359 DerivedPointerTable::clear(); 360 #endif 361 362 WorkGang* workers = _heap->workers(); 363 bool is_par = workers->active_workers() > 1; 364 365 ShenandoahUpdateThreadRootsTask task(is_par, root_phase); 366 workers->run_task(&task); 367 368 #if COMPILER2_OR_JVMCI 369 DerivedPointerTable::update_pointers(); 370 #endif 371 } 372 373 void ShenandoahConcurrentMark::initialize(uint workers) { 374 _heap = ShenandoahHeap::heap(); 375 376 uint num_queues = MAX2(workers, 1U); 377 378 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues); 379 380 for (uint i = 0; i < num_queues; ++i) { 381 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue(); 382 task_queue->initialize(); 383 _task_queues->register_queue(i, task_queue); 384 } 385 } 386 387 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) { 388 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) { 389 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id); 390 if (!_heap->unload_classes()) { 391 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 392 // TODO: We can not honor StringDeduplication here, due to lock ranking 393 // inversion. So, we may miss some deduplication candidates. 394 if (_heap->has_forwarded_objects()) { 395 ShenandoahMarkResolveRefsClosure cl(q, rp); 396 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations); 397 CodeCache::blobs_do(&blobs); 398 } else { 399 ShenandoahMarkRefsClosure cl(q, rp); 400 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations); 401 CodeCache::blobs_do(&blobs); 402 } 403 } 404 } 405 } 406 407 void ShenandoahConcurrentMark::mark_from_roots() { 408 WorkGang* workers = _heap->workers(); 409 uint nworkers = workers->active_workers(); 410 411 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark); 412 413 if (_heap->process_references()) { 414 ReferenceProcessor* rp = _heap->ref_processor(); 415 rp->set_active_mt_degree(nworkers); 416 417 // enable ("weak") refs discovery 418 rp->enable_discovery(true /*verify_no_refs*/); 419 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs()); 420 } 421 422 shenandoah_assert_rp_isalive_not_installed(); 423 ShenandoahIsAliveSelector is_alive; 424 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure()); 425 426 task_queues()->reserve(nworkers); 427 428 { 429 TaskTerminator terminator(nworkers, task_queues()); 430 ShenandoahConcurrentMarkingTask task(this, &terminator); 431 workers->run_task(&task); 432 } 433 434 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled"); 435 } 436 437 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) { 438 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 439 440 uint nworkers = _heap->workers()->active_workers(); 441 442 // Finally mark everything else we've got in our queues during the previous steps. 443 // It does two different things for concurrent vs. mark-compact GC: 444 // - For concurrent GC, it starts with empty task queues, drains the remaining 445 // SATB buffers, and then completes the marking closure. 446 // - For mark-compact GC, it starts out with the task queues seeded by initial 447 // root scan, and completes the closure, thus marking through all live objects 448 // The implementation is the same, so it's shared here. 449 { 450 ShenandoahGCPhase phase(full_gc ? 451 ShenandoahPhaseTimings::full_gc_mark_finish_queues : 452 ShenandoahPhaseTimings::finish_queues); 453 task_queues()->reserve(nworkers); 454 455 shenandoah_assert_rp_isalive_not_installed(); 456 ShenandoahIsAliveSelector is_alive; 457 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure()); 458 459 StrongRootsScope scope(nworkers); 460 TaskTerminator terminator(nworkers, task_queues()); 461 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled()); 462 _heap->workers()->run_task(&task); 463 } 464 465 assert(task_queues()->is_empty(), "Should be empty"); 466 467 // When we're done marking everything, we process weak references. 468 if (_heap->process_references()) { 469 weak_refs_work(full_gc); 470 } 471 472 assert(task_queues()->is_empty(), "Should be empty"); 473 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats()); 474 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats()); 475 } 476 477 // Weak Reference Closures 478 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure { 479 uint _worker_id; 480 TaskTerminator* _terminator; 481 bool _reset_terminator; 482 483 public: 484 ShenandoahCMDrainMarkingStackClosure(uint worker_id, TaskTerminator* t, bool reset_terminator = false): 485 _worker_id(worker_id), 486 _terminator(t), 487 _reset_terminator(reset_terminator) { 488 } 489 490 void do_void() { 491 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 492 493 ShenandoahHeap* sh = ShenandoahHeap::heap(); 494 ShenandoahConcurrentMark* scm = sh->concurrent_mark(); 495 assert(sh->process_references(), "why else would we be here?"); 496 ReferenceProcessor* rp = sh->ref_processor(); 497 498 shenandoah_assert_rp_isalive_installed(); 499 500 scm->mark_loop(_worker_id, _terminator, rp, 501 false, // not cancellable 502 false); // do not do strdedup 503 504 if (_reset_terminator) { 505 _terminator->reset_for_reuse(); 506 } 507 } 508 }; 509 510 class ShenandoahCMKeepAliveClosure : public OopClosure { 511 private: 512 ShenandoahObjToScanQueue* _queue; 513 ShenandoahHeap* _heap; 514 ShenandoahMarkingContext* const _mark_context; 515 516 template <class T> 517 inline void do_oop_work(T* p) { 518 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context); 519 } 520 521 public: 522 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) : 523 _queue(q), 524 _heap(ShenandoahHeap::heap()), 525 _mark_context(_heap->marking_context()) {} 526 527 void do_oop(narrowOop* p) { do_oop_work(p); } 528 void do_oop(oop* p) { do_oop_work(p); } 529 }; 530 531 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure { 532 private: 533 ShenandoahObjToScanQueue* _queue; 534 ShenandoahHeap* _heap; 535 ShenandoahMarkingContext* const _mark_context; 536 537 template <class T> 538 inline void do_oop_work(T* p) { 539 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context); 540 } 541 542 public: 543 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) : 544 _queue(q), 545 _heap(ShenandoahHeap::heap()), 546 _mark_context(_heap->marking_context()) {} 547 548 void do_oop(narrowOop* p) { do_oop_work(p); } 549 void do_oop(oop* p) { do_oop_work(p); } 550 }; 551 552 class ShenandoahWeakUpdateClosure : public OopClosure { 553 private: 554 ShenandoahHeap* const _heap; 555 556 template <class T> 557 inline void do_oop_work(T* p) { 558 oop o = _heap->maybe_update_with_forwarded(p); 559 shenandoah_assert_marked_except(p, o, o == NULL); 560 } 561 562 public: 563 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {} 564 565 void do_oop(narrowOop* p) { do_oop_work(p); } 566 void do_oop(oop* p) { do_oop_work(p); } 567 }; 568 569 class ShenandoahRefProcTaskProxy : public AbstractGangTask { 570 private: 571 AbstractRefProcTaskExecutor::ProcessTask& _proc_task; 572 TaskTerminator* _terminator; 573 574 public: 575 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task, 576 TaskTerminator* t) : 577 AbstractGangTask("Process reference objects in parallel"), 578 _proc_task(proc_task), 579 _terminator(t) { 580 } 581 582 void work(uint worker_id) { 583 ResourceMark rm; 584 HandleMark hm; 585 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 586 ShenandoahHeap* heap = ShenandoahHeap::heap(); 587 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator); 588 if (heap->has_forwarded_objects()) { 589 ShenandoahForwardedIsAliveClosure is_alive; 590 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id)); 591 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc); 592 } else { 593 ShenandoahIsAliveClosure is_alive; 594 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id)); 595 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc); 596 } 597 } 598 }; 599 600 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor { 601 private: 602 WorkGang* _workers; 603 604 public: 605 ShenandoahRefProcTaskExecutor(WorkGang* workers) : 606 _workers(workers) { 607 } 608 609 // Executes a task using worker threads. 610 void execute(ProcessTask& task, uint ergo_workers) { 611 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 612 613 ShenandoahHeap* heap = ShenandoahHeap::heap(); 614 ShenandoahConcurrentMark* cm = heap->concurrent_mark(); 615 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(), 616 ergo_workers, 617 /* do_check = */ false); 618 uint nworkers = _workers->active_workers(); 619 cm->task_queues()->reserve(nworkers); 620 TaskTerminator terminator(nworkers, cm->task_queues()); 621 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator); 622 _workers->run_task(&proc_task_proxy); 623 } 624 }; 625 626 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) { 627 assert(_heap->process_references(), "sanity"); 628 629 ShenandoahPhaseTimings::Phase phase_root = 630 full_gc ? 631 ShenandoahPhaseTimings::full_gc_weakrefs : 632 ShenandoahPhaseTimings::weakrefs; 633 634 ShenandoahGCPhase phase(phase_root); 635 636 ReferenceProcessor* rp = _heap->ref_processor(); 637 638 // NOTE: We cannot shortcut on has_discovered_references() here, because 639 // we will miss marking JNI Weak refs then, see implementation in 640 // ReferenceProcessor::process_discovered_references. 641 weak_refs_work_doit(full_gc); 642 643 rp->verify_no_references_recorded(); 644 assert(!rp->discovery_enabled(), "Post condition"); 645 646 } 647 648 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) { 649 ReferenceProcessor* rp = _heap->ref_processor(); 650 651 ShenandoahPhaseTimings::Phase phase_process = 652 full_gc ? 653 ShenandoahPhaseTimings::full_gc_weakrefs_process : 654 ShenandoahPhaseTimings::weakrefs_process; 655 656 shenandoah_assert_rp_isalive_not_installed(); 657 ShenandoahIsAliveSelector is_alive; 658 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure()); 659 660 WorkGang* workers = _heap->workers(); 661 uint nworkers = workers->active_workers(); 662 663 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs()); 664 rp->set_active_mt_degree(nworkers); 665 666 assert(task_queues()->is_empty(), "Should be empty"); 667 668 // complete_gc and keep_alive closures instantiated here are only needed for 669 // single-threaded path in RP. They share the queue 0 for tracking work, which 670 // simplifies implementation. Since RP may decide to call complete_gc several 671 // times, we need to be able to reuse the terminator. 672 uint serial_worker_id = 0; 673 TaskTerminator terminator(1, task_queues()); 674 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true); 675 676 ShenandoahRefProcTaskExecutor executor(workers); 677 678 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues()); 679 680 { 681 ShenandoahGCPhase phase(phase_process); 682 683 if (_heap->has_forwarded_objects()) { 684 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id)); 685 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive, 686 &complete_gc, &executor, 687 &pt); 688 689 } else { 690 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id)); 691 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive, 692 &complete_gc, &executor, 693 &pt); 694 695 } 696 697 pt.print_all_references(); 698 699 assert(task_queues()->is_empty(), "Should be empty"); 700 } 701 } 702 703 class ShenandoahCancelledGCYieldClosure : public YieldClosure { 704 private: 705 ShenandoahHeap* const _heap; 706 public: 707 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {}; 708 virtual bool should_return() { return _heap->cancelled_gc(); } 709 }; 710 711 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure { 712 public: 713 void do_void() { 714 ShenandoahHeap* sh = ShenandoahHeap::heap(); 715 ShenandoahConcurrentMark* scm = sh->concurrent_mark(); 716 assert(sh->process_references(), "why else would we be here?"); 717 TaskTerminator terminator(1, scm->task_queues()); 718 719 ReferenceProcessor* rp = sh->ref_processor(); 720 shenandoah_assert_rp_isalive_installed(); 721 722 scm->mark_loop(0, &terminator, rp, 723 false, // not cancellable 724 false); // do not do strdedup 725 } 726 }; 727 728 class ShenandoahPrecleanTask : public AbstractGangTask { 729 private: 730 ReferenceProcessor* _rp; 731 732 public: 733 ShenandoahPrecleanTask(ReferenceProcessor* rp) : 734 AbstractGangTask("Precleaning task"), 735 _rp(rp) {} 736 737 void work(uint worker_id) { 738 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected"); 739 ShenandoahParallelWorkerSession worker_session(worker_id); 740 741 ShenandoahHeap* sh = ShenandoahHeap::heap(); 742 assert(!sh->has_forwarded_objects(), "No forwarded objects expected here"); 743 744 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id); 745 746 ShenandoahCancelledGCYieldClosure yield; 747 ShenandoahPrecleanCompleteGCClosure complete_gc; 748 749 ShenandoahIsAliveClosure is_alive; 750 ShenandoahCMKeepAliveClosure keep_alive(q); 751 ResourceMark rm; 752 _rp->preclean_discovered_references(&is_alive, &keep_alive, 753 &complete_gc, &yield, 754 NULL); 755 } 756 }; 757 758 void ShenandoahConcurrentMark::preclean_weak_refs() { 759 // Pre-cleaning weak references before diving into STW makes sense at the 760 // end of concurrent mark. This will filter out the references which referents 761 // are alive. Note that ReferenceProcessor already filters out these on reference 762 // discovery, and the bulk of work is done here. This phase processes leftovers 763 // that missed the initial filtering, i.e. when referent was marked alive after 764 // reference was discovered by RP. 765 766 assert(_heap->process_references(), "sanity"); 767 768 // Shortcut if no references were discovered to avoid winding up threads. 769 ReferenceProcessor* rp = _heap->ref_processor(); 770 if (!rp->has_discovered_references()) { 771 return; 772 } 773 774 assert(task_queues()->is_empty(), "Should be empty"); 775 776 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false); 777 778 shenandoah_assert_rp_isalive_not_installed(); 779 ShenandoahIsAliveSelector is_alive; 780 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure()); 781 782 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup 783 // queues and other goodies. When upstream ReferenceProcessor starts supporting 784 // parallel precleans, we can extend this to more threads. 785 WorkGang* workers = _heap->workers(); 786 uint nworkers = workers->active_workers(); 787 assert(nworkers == 1, "This code uses only a single worker"); 788 task_queues()->reserve(nworkers); 789 790 ShenandoahPrecleanTask task(rp); 791 workers->run_task(&task); 792 793 assert(task_queues()->is_empty(), "Should be empty"); 794 } 795 796 void ShenandoahConcurrentMark::cancel() { 797 // Clean up marking stacks. 798 ShenandoahObjToScanQueueSet* queues = task_queues(); 799 queues->clear(); 800 801 // Cancel SATB buffers. 802 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking(); 803 } 804 805 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) { 806 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id); 807 return _task_queues->queue(worker_id); 808 } 809 810 template <bool CANCELLABLE> 811 void ShenandoahConcurrentMark::mark_loop_prework(uint w, TaskTerminator *t, ReferenceProcessor *rp, 812 bool strdedup) { 813 ShenandoahObjToScanQueue* q = get_queue(w); 814 815 jushort* ld = _heap->get_liveness_cache(w); 816 817 // TODO: We can clean up this if we figure out how to do templated oop closures that 818 // play nice with specialized_oop_iterators. 819 if (_heap->unload_classes()) { 820 if (_heap->has_forwarded_objects()) { 821 if (strdedup) { 822 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp); 823 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t); 824 } else { 825 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp); 826 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t); 827 } 828 } else { 829 if (strdedup) { 830 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp); 831 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t); 832 } else { 833 ShenandoahMarkRefsMetadataClosure cl(q, rp); 834 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t); 835 } 836 } 837 } else { 838 if (_heap->has_forwarded_objects()) { 839 if (strdedup) { 840 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp); 841 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t); 842 } else { 843 ShenandoahMarkUpdateRefsClosure cl(q, rp); 844 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t); 845 } 846 } else { 847 if (strdedup) { 848 ShenandoahMarkRefsDedupClosure cl(q, rp); 849 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t); 850 } else { 851 ShenandoahMarkRefsClosure cl(q, rp); 852 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t); 853 } 854 } 855 } 856 857 _heap->flush_liveness_cache(w); 858 } 859 860 template <class T, bool CANCELLABLE> 861 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, TaskTerminator *terminator) { 862 uintx stride = ShenandoahMarkLoopStride; 863 864 ShenandoahHeap* heap = ShenandoahHeap::heap(); 865 ShenandoahObjToScanQueueSet* queues = task_queues(); 866 ShenandoahObjToScanQueue* q; 867 ShenandoahMarkTask t; 868 869 /* 870 * Process outstanding queues, if any. 871 * 872 * There can be more queues than workers. To deal with the imbalance, we claim 873 * extra queues first. Since marking can push new tasks into the queue associated 874 * with this worker id, we come back to process this queue in the normal loop. 875 */ 876 assert(queues->get_reserved() == heap->workers()->active_workers(), 877 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers()); 878 879 q = queues->claim_next(); 880 while (q != NULL) { 881 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) { 882 return; 883 } 884 885 for (uint i = 0; i < stride; i++) { 886 if (q->pop(t)) { 887 do_task<T>(q, cl, live_data, &t); 888 } else { 889 assert(q->is_empty(), "Must be empty"); 890 q = queues->claim_next(); 891 break; 892 } 893 } 894 } 895 q = get_queue(worker_id); 896 897 ShenandoahSATBBufferClosure drain_satb(q); 898 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set(); 899 900 /* 901 * Normal marking loop: 902 */ 903 while (true) { 904 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) { 905 return; 906 } 907 908 while (satb_mq_set.completed_buffers_num() > 0) { 909 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb); 910 } 911 912 uint work = 0; 913 for (uint i = 0; i < stride; i++) { 914 if (q->pop(t) || 915 queues->steal(worker_id, t)) { 916 do_task<T>(q, cl, live_data, &t); 917 work++; 918 } else { 919 break; 920 } 921 } 922 923 if (work == 0) { 924 // No work encountered in current stride, try to terminate. 925 // Need to leave the STS here otherwise it might block safepoints. 926 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers); 927 ShenandoahTerminatorTerminator tt(heap); 928 if (terminator->offer_termination(&tt)) return; 929 } 930 } 931 } 932 933 bool ShenandoahConcurrentMark::claim_codecache() { 934 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise"); 935 return _claimed_codecache.try_set(); 936 } 937 938 void ShenandoahConcurrentMark::clear_claim_codecache() { 939 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise"); 940 _claimed_codecache.unset(); 941 }