1 /* 2 * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. 7 * 8 * This code is distributed in the hope that it will be useful, but WITHOUT 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 11 * version 2 for more details (a copy is included in the LICENSE file that 12 * accompanied this code). 13 * 14 * You should have received a copy of the GNU General Public License version 15 * 2 along with this work; if not, write to the Free Software Foundation, 16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 19 * or visit www.oracle.com if you need additional information or have any 20 * questions. 21 * 22 */ 23 24 #include "precompiled.hpp" 25 26 #include "classfile/symbolTable.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "code/codeCache.hpp" 29 30 #include "gc/shared/weakProcessor.inline.hpp" 31 #include "gc/shared/gcTimer.hpp" 32 #include "gc/shared/referenceProcessor.hpp" 33 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 34 35 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp" 36 #include "gc/shenandoah/shenandoahClosures.inline.hpp" 37 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp" 38 #include "gc/shenandoah/shenandoahMarkCompact.hpp" 39 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 40 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp" 41 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp" 42 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp" 43 #include "gc/shenandoah/shenandoahTimingTracker.hpp" 44 #include "gc/shenandoah/shenandoahUtils.hpp" 45 46 #include "memory/iterator.inline.hpp" 47 #include "memory/metaspace.hpp" 48 #include "memory/resourceArea.hpp" 49 #include "oops/oop.inline.hpp" 50 #include "runtime/handles.inline.hpp" 51 52 template<UpdateRefsMode UPDATE_REFS> 53 class ShenandoahInitMarkRootsClosure : public OopClosure { 54 private: 55 ShenandoahObjToScanQueue* _queue; 56 ShenandoahHeap* _heap; 57 ShenandoahMarkingContext* const _mark_context; 58 59 template <class T> 60 inline void do_oop_work(T* p) { 61 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, NO_DEDUP>(p, _heap, _queue, _mark_context); 62 } 63 64 public: 65 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) : 66 _queue(q), 67 _heap(ShenandoahHeap::heap()), 68 _mark_context(_heap->marking_context()) {}; 69 70 void do_oop(narrowOop* p) { do_oop_work(p); } 71 void do_oop(oop* p) { do_oop_work(p); } 72 }; 73 74 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) : 75 MetadataVisitingOopIterateClosure(rp), 76 _queue(q), 77 _heap(ShenandoahHeap::heap()), 78 _mark_context(_heap->marking_context()) 79 { } 80 81 template<UpdateRefsMode UPDATE_REFS> 82 class ShenandoahInitMarkRootsTask : public AbstractGangTask { 83 private: 84 ShenandoahAllRootScanner* _rp; 85 bool _process_refs; 86 public: 87 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp, bool process_refs) : 88 AbstractGangTask("Shenandoah init mark roots task"), 89 _rp(rp), 90 _process_refs(process_refs) { 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 public: 130 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater) : 131 AbstractGangTask("Shenandoah update roots task"), 132 _root_updater(root_updater) { 133 } 134 135 void work(uint worker_id) { 136 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 137 ShenandoahParallelWorkerSession worker_session(worker_id); 138 139 ShenandoahHeap* heap = ShenandoahHeap::heap(); 140 ShenandoahUpdateRefsClosure cl; 141 AlwaysTrueClosure always_true; 142 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl); 143 } 144 }; 145 146 class ShenandoahConcurrentMarkingTask : public AbstractGangTask { 147 private: 148 ShenandoahConcurrentMark* _cm; 149 ShenandoahTaskTerminator* _terminator; 150 151 public: 152 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator) : 153 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) { 154 } 155 156 void work(uint worker_id) { 157 ShenandoahHeap* heap = ShenandoahHeap::heap(); 158 ShenandoahConcurrentWorkerSession worker_session(worker_id); 159 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers); 160 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id); 161 ReferenceProcessor* rp; 162 if (heap->process_references()) { 163 rp = heap->ref_processor(); 164 shenandoah_assert_rp_isalive_installed(); 165 } else { 166 rp = NULL; 167 } 168 169 _cm->concurrent_scan_code_roots(worker_id, rp); 170 _cm->mark_loop(worker_id, _terminator, rp, 171 true, // cancellable 172 ShenandoahStringDedup::is_enabled()); // perform string dedup 173 } 174 }; 175 176 class ShenandoahSATBThreadsClosure : public ThreadClosure { 177 private: 178 ShenandoahSATBBufferClosure* _satb_cl; 179 uintx _claim_token; 180 181 public: 182 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) : 183 _satb_cl(satb_cl), 184 _claim_token(Threads::thread_claim_token()) {} 185 186 void do_thread(Thread* thread) { 187 if (thread->claim_threads_do(true, _claim_token)) { 188 ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl); 189 } 190 } 191 }; 192 193 class ShenandoahFinalMarkingTask : public AbstractGangTask { 194 private: 195 ShenandoahConcurrentMark* _cm; 196 ShenandoahTaskTerminator* _terminator; 197 bool _dedup_string; 198 199 public: 200 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) : 201 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) { 202 } 203 204 void work(uint worker_id) { 205 ShenandoahHeap* heap = ShenandoahHeap::heap(); 206 207 ShenandoahParallelWorkerSession worker_session(worker_id); 208 // First drain remaining SATB buffers. 209 // Notice that this is not strictly necessary for mark-compact. But since 210 // it requires a StrongRootsScope around the task, we need to claim the 211 // threads, and performance-wise it doesn't really matter. Adds about 1ms to 212 // full-gc. 213 { 214 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id); 215 ShenandoahSATBBufferClosure cl(q); 216 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set(); 217 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)); 218 ShenandoahSATBThreadsClosure tc(&cl); 219 Threads::threads_do(&tc); 220 } 221 222 ReferenceProcessor* rp; 223 if (heap->process_references()) { 224 rp = heap->ref_processor(); 225 shenandoah_assert_rp_isalive_installed(); 226 } else { 227 rp = NULL; 228 } 229 230 if (heap->is_degenerated_gc_in_progress()) { 231 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned, 232 // let's check here. 233 _cm->concurrent_scan_code_roots(worker_id, rp); 234 } 235 236 _cm->mark_loop(worker_id, _terminator, rp, 237 false, // not cancellable 238 _dedup_string); 239 240 assert(_cm->task_queues()->is_empty(), "Should be empty"); 241 } 242 }; 243 244 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) { 245 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread"); 246 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 247 248 ShenandoahHeap* heap = ShenandoahHeap::heap(); 249 250 ShenandoahGCPhase phase(root_phase); 251 252 WorkGang* workers = heap->workers(); 253 uint nworkers = workers->active_workers(); 254 255 assert(nworkers <= task_queues()->size(), "Just check"); 256 257 ShenandoahAllRootScanner root_proc(nworkers, root_phase); 258 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats()); 259 task_queues()->reserve(nworkers); 260 261 if (heap->has_forwarded_objects()) { 262 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references()); 263 workers->run_task(&mark_roots); 264 } else { 265 // No need to update references, which means the heap is stable. 266 // Can save time not walking through forwarding pointers. 267 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references()); 268 workers->run_task(&mark_roots); 269 } 270 271 if (ShenandoahConcurrentScanCodeRoots) { 272 clear_claim_codecache(); 273 } 274 } 275 276 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) { 277 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 278 279 bool update_code_cache = true; // initialize to safer value 280 switch (root_phase) { 281 case ShenandoahPhaseTimings::update_roots: 282 case ShenandoahPhaseTimings::final_update_refs_roots: 283 update_code_cache = false; 284 break; 285 case ShenandoahPhaseTimings::full_gc_roots: 286 case ShenandoahPhaseTimings::degen_gc_update_roots: 287 update_code_cache = true; 288 break; 289 default: 290 ShouldNotReachHere(); 291 } 292 293 ShenandoahGCPhase phase(root_phase); 294 295 #if COMPILER2_OR_JVMCI 296 DerivedPointerTable::clear(); 297 #endif 298 299 uint nworkers = _heap->workers()->active_workers(); 300 301 ShenandoahRootUpdater root_updater(nworkers, root_phase, update_code_cache); 302 ShenandoahUpdateRootsTask update_roots(&root_updater); 303 _heap->workers()->run_task(&update_roots); 304 305 #if COMPILER2_OR_JVMCI 306 DerivedPointerTable::update_pointers(); 307 #endif 308 } 309 310 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask { 311 private: 312 ShenandoahThreadRoots _thread_roots; 313 ShenandoahPhaseTimings::Phase _phase; 314 public: 315 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) : 316 AbstractGangTask("Shenandoah Update Thread Roots"), 317 _thread_roots(is_par), 318 _phase(phase) { 319 ShenandoahHeap::heap()->phase_timings()->record_workers_start(_phase); 320 } 321 322 ~ShenandoahUpdateThreadRootsTask() { 323 ShenandoahHeap::heap()->phase_timings()->record_workers_end(_phase); 324 } 325 void work(uint worker_id) { 326 ShenandoahUpdateRefsClosure cl; 327 _thread_roots.oops_do(&cl, NULL, worker_id); 328 } 329 }; 330 331 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) { 332 WorkGang* workers = _heap->workers(); 333 bool is_par = workers->active_workers() > 1; 334 #if COMPILER2_OR_JVMCI 335 DerivedPointerTable::clear(); 336 #endif 337 ShenandoahUpdateThreadRootsTask task(is_par, root_phase); 338 workers->run_task(&task); 339 #if COMPILER2_OR_JVMCI 340 DerivedPointerTable::update_pointers(); 341 #endif 342 } 343 344 void ShenandoahConcurrentMark::initialize(uint workers) { 345 _heap = ShenandoahHeap::heap(); 346 347 uint num_queues = MAX2(workers, 1U); 348 349 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues); 350 351 for (uint i = 0; i < num_queues; ++i) { 352 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue(); 353 task_queue->initialize(); 354 _task_queues->register_queue(i, task_queue); 355 } 356 } 357 358 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) { 359 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) { 360 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id); 361 if (!_heap->unload_classes()) { 362 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 363 // TODO: We can not honor StringDeduplication here, due to lock ranking 364 // inversion. So, we may miss some deduplication candidates. 365 if (_heap->has_forwarded_objects()) { 366 ShenandoahMarkResolveRefsClosure cl(q, rp); 367 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations); 368 CodeCache::blobs_do(&blobs); 369 } else { 370 ShenandoahMarkRefsClosure cl(q, rp); 371 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations); 372 CodeCache::blobs_do(&blobs); 373 } 374 } 375 } 376 } 377 378 void ShenandoahConcurrentMark::mark_from_roots() { 379 WorkGang* workers = _heap->workers(); 380 uint nworkers = workers->active_workers(); 381 382 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark); 383 384 if (_heap->process_references()) { 385 ReferenceProcessor* rp = _heap->ref_processor(); 386 rp->set_active_mt_degree(nworkers); 387 388 // enable ("weak") refs discovery 389 rp->enable_discovery(true /*verify_no_refs*/); 390 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs()); 391 } 392 393 shenandoah_assert_rp_isalive_not_installed(); 394 ShenandoahIsAliveSelector is_alive; 395 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure()); 396 397 task_queues()->reserve(nworkers); 398 399 { 400 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination); 401 ShenandoahTaskTerminator terminator(nworkers, task_queues()); 402 ShenandoahConcurrentMarkingTask task(this, &terminator); 403 workers->run_task(&task); 404 } 405 406 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled"); 407 } 408 409 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) { 410 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 411 412 uint nworkers = _heap->workers()->active_workers(); 413 414 // Finally mark everything else we've got in our queues during the previous steps. 415 // It does two different things for concurrent vs. mark-compact GC: 416 // - For concurrent GC, it starts with empty task queues, drains the remaining 417 // SATB buffers, and then completes the marking closure. 418 // - For mark-compact GC, it starts out with the task queues seeded by initial 419 // root scan, and completes the closure, thus marking through all live objects 420 // The implementation is the same, so it's shared here. 421 { 422 ShenandoahGCPhase phase(full_gc ? 423 ShenandoahPhaseTimings::full_gc_mark_finish_queues : 424 ShenandoahPhaseTimings::finish_queues); 425 task_queues()->reserve(nworkers); 426 427 shenandoah_assert_rp_isalive_not_installed(); 428 ShenandoahIsAliveSelector is_alive; 429 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure()); 430 431 ShenandoahTerminationTracker termination_tracker(full_gc ? 432 ShenandoahPhaseTimings::full_gc_mark_termination : 433 ShenandoahPhaseTimings::termination); 434 435 StrongRootsScope scope(nworkers); 436 ShenandoahTaskTerminator terminator(nworkers, task_queues()); 437 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled()); 438 _heap->workers()->run_task(&task); 439 } 440 441 assert(task_queues()->is_empty(), "Should be empty"); 442 443 // When we're done marking everything, we process weak references. 444 if (_heap->process_references()) { 445 weak_refs_work(full_gc); 446 } 447 448 weak_roots_work(); 449 450 // And finally finish class unloading 451 if (_heap->unload_classes()) { 452 _heap->unload_classes_and_cleanup_tables(full_gc); 453 } else if (ShenandoahStringDedup::is_enabled()) { 454 ShenandoahIsAliveSelector alive; 455 BoolObjectClosure* is_alive = alive.is_alive_closure(); 456 ShenandoahStringDedup::unlink_or_oops_do(is_alive, NULL, false); 457 } 458 assert(task_queues()->is_empty(), "Should be empty"); 459 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats()); 460 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats()); 461 462 // Resize Metaspace 463 MetaspaceGC::compute_new_size(); 464 } 465 466 // Weak Reference Closures 467 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure { 468 uint _worker_id; 469 ShenandoahTaskTerminator* _terminator; 470 bool _reset_terminator; 471 472 public: 473 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false): 474 _worker_id(worker_id), 475 _terminator(t), 476 _reset_terminator(reset_terminator) { 477 } 478 479 void do_void() { 480 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 481 482 ShenandoahHeap* sh = ShenandoahHeap::heap(); 483 ShenandoahConcurrentMark* scm = sh->concurrent_mark(); 484 assert(sh->process_references(), "why else would we be here?"); 485 ReferenceProcessor* rp = sh->ref_processor(); 486 487 shenandoah_assert_rp_isalive_installed(); 488 489 scm->mark_loop(_worker_id, _terminator, rp, 490 false, // not cancellable 491 false); // do not do strdedup 492 493 if (_reset_terminator) { 494 _terminator->reset_for_reuse(); 495 } 496 } 497 }; 498 499 class ShenandoahCMKeepAliveClosure : public OopClosure { 500 private: 501 ShenandoahObjToScanQueue* _queue; 502 ShenandoahHeap* _heap; 503 ShenandoahMarkingContext* const _mark_context; 504 505 template <class T> 506 inline void do_oop_work(T* p) { 507 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context); 508 } 509 510 public: 511 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) : 512 _queue(q), 513 _heap(ShenandoahHeap::heap()), 514 _mark_context(_heap->marking_context()) {} 515 516 void do_oop(narrowOop* p) { do_oop_work(p); } 517 void do_oop(oop* p) { do_oop_work(p); } 518 }; 519 520 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure { 521 private: 522 ShenandoahObjToScanQueue* _queue; 523 ShenandoahHeap* _heap; 524 ShenandoahMarkingContext* const _mark_context; 525 526 template <class T> 527 inline void do_oop_work(T* p) { 528 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context); 529 } 530 531 public: 532 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) : 533 _queue(q), 534 _heap(ShenandoahHeap::heap()), 535 _mark_context(_heap->marking_context()) {} 536 537 void do_oop(narrowOop* p) { do_oop_work(p); } 538 void do_oop(oop* p) { do_oop_work(p); } 539 }; 540 541 class ShenandoahWeakUpdateClosure : public OopClosure { 542 private: 543 ShenandoahHeap* const _heap; 544 545 template <class T> 546 inline void do_oop_work(T* p) { 547 oop o = _heap->maybe_update_with_forwarded(p); 548 shenandoah_assert_marked_except(p, o, o == NULL); 549 } 550 551 public: 552 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {} 553 554 void do_oop(narrowOop* p) { do_oop_work(p); } 555 void do_oop(oop* p) { do_oop_work(p); } 556 }; 557 558 class ShenandoahWeakAssertNotForwardedClosure : public OopClosure { 559 private: 560 template <class T> 561 inline void do_oop_work(T* p) { 562 #ifdef ASSERT 563 T o = RawAccess<>::oop_load(p); 564 if (!CompressedOops::is_null(o)) { 565 oop obj = CompressedOops::decode_not_null(o); 566 shenandoah_assert_not_forwarded(p, obj); 567 } 568 #endif 569 } 570 571 public: 572 ShenandoahWeakAssertNotForwardedClosure() {} 573 574 void do_oop(narrowOop* p) { do_oop_work(p); } 575 void do_oop(oop* p) { do_oop_work(p); } 576 }; 577 578 class ShenandoahRefProcTaskProxy : public AbstractGangTask { 579 private: 580 AbstractRefProcTaskExecutor::ProcessTask& _proc_task; 581 ShenandoahTaskTerminator* _terminator; 582 583 public: 584 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task, 585 ShenandoahTaskTerminator* t) : 586 AbstractGangTask("Process reference objects in parallel"), 587 _proc_task(proc_task), 588 _terminator(t) { 589 } 590 591 void work(uint worker_id) { 592 ResourceMark rm; 593 HandleMark hm; 594 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 595 ShenandoahHeap* heap = ShenandoahHeap::heap(); 596 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator); 597 if (heap->has_forwarded_objects()) { 598 ShenandoahForwardedIsAliveClosure is_alive; 599 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id)); 600 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc); 601 } else { 602 ShenandoahIsAliveClosure is_alive; 603 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id)); 604 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc); 605 } 606 } 607 }; 608 609 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor { 610 private: 611 WorkGang* _workers; 612 613 public: 614 ShenandoahRefProcTaskExecutor(WorkGang* workers) : 615 _workers(workers) { 616 } 617 618 // Executes a task using worker threads. 619 void execute(ProcessTask& task, uint ergo_workers) { 620 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 621 622 ShenandoahHeap* heap = ShenandoahHeap::heap(); 623 ShenandoahConcurrentMark* cm = heap->concurrent_mark(); 624 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(), 625 ergo_workers, 626 /* do_check = */ false); 627 uint nworkers = _workers->active_workers(); 628 cm->task_queues()->reserve(nworkers); 629 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues()); 630 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator); 631 _workers->run_task(&proc_task_proxy); 632 } 633 }; 634 635 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) { 636 assert(_heap->process_references(), "sanity"); 637 638 ShenandoahPhaseTimings::Phase phase_root = 639 full_gc ? 640 ShenandoahPhaseTimings::full_gc_weakrefs : 641 ShenandoahPhaseTimings::weakrefs; 642 643 ShenandoahGCPhase phase(phase_root); 644 645 ReferenceProcessor* rp = _heap->ref_processor(); 646 647 // NOTE: We cannot shortcut on has_discovered_references() here, because 648 // we will miss marking JNI Weak refs then, see implementation in 649 // ReferenceProcessor::process_discovered_references. 650 weak_refs_work_doit(full_gc); 651 652 rp->verify_no_references_recorded(); 653 assert(!rp->discovery_enabled(), "Post condition"); 654 655 } 656 657 // Process leftover weak oops: update them, if needed or assert they do not 658 // need updating otherwise. 659 // Weak processor API requires us to visit the oops, even if we are not doing 660 // anything to them. 661 void ShenandoahConcurrentMark::weak_roots_work() { 662 WorkGang* workers = _heap->workers(); 663 OopClosure* keep_alive = &do_nothing_cl; 664 #ifdef ASSERT 665 ShenandoahWeakAssertNotForwardedClosure verify_cl; 666 keep_alive = &verify_cl; 667 #endif 668 ShenandoahIsAliveClosure is_alive; 669 WeakProcessor::weak_oops_do(workers, &is_alive, keep_alive, 1); 670 } 671 672 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) { 673 ReferenceProcessor* rp = _heap->ref_processor(); 674 675 ShenandoahPhaseTimings::Phase phase_process = 676 full_gc ? 677 ShenandoahPhaseTimings::full_gc_weakrefs_process : 678 ShenandoahPhaseTimings::weakrefs_process; 679 680 ShenandoahPhaseTimings::Phase phase_process_termination = 681 full_gc ? 682 ShenandoahPhaseTimings::full_gc_weakrefs_termination : 683 ShenandoahPhaseTimings::weakrefs_termination; 684 685 shenandoah_assert_rp_isalive_not_installed(); 686 ShenandoahIsAliveSelector is_alive; 687 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure()); 688 689 WorkGang* workers = _heap->workers(); 690 uint nworkers = workers->active_workers(); 691 692 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs()); 693 rp->set_active_mt_degree(nworkers); 694 695 assert(task_queues()->is_empty(), "Should be empty"); 696 697 // complete_gc and keep_alive closures instantiated here are only needed for 698 // single-threaded path in RP. They share the queue 0 for tracking work, which 699 // simplifies implementation. Since RP may decide to call complete_gc several 700 // times, we need to be able to reuse the terminator. 701 uint serial_worker_id = 0; 702 ShenandoahTaskTerminator terminator(1, task_queues()); 703 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true); 704 705 ShenandoahRefProcTaskExecutor executor(workers); 706 707 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues()); 708 709 { 710 ShenandoahGCPhase phase(phase_process); 711 ShenandoahTerminationTracker phase_term(phase_process_termination); 712 713 if (_heap->has_forwarded_objects()) { 714 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id)); 715 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive, 716 &complete_gc, &executor, 717 &pt); 718 719 } else { 720 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id)); 721 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive, 722 &complete_gc, &executor, 723 &pt); 724 725 } 726 727 pt.print_all_references(); 728 729 assert(task_queues()->is_empty(), "Should be empty"); 730 } 731 } 732 733 class ShenandoahCancelledGCYieldClosure : public YieldClosure { 734 private: 735 ShenandoahHeap* const _heap; 736 public: 737 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {}; 738 virtual bool should_return() { return _heap->cancelled_gc(); } 739 }; 740 741 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure { 742 public: 743 void do_void() { 744 ShenandoahHeap* sh = ShenandoahHeap::heap(); 745 ShenandoahConcurrentMark* scm = sh->concurrent_mark(); 746 assert(sh->process_references(), "why else would we be here?"); 747 ShenandoahTaskTerminator terminator(1, scm->task_queues()); 748 749 ReferenceProcessor* rp = sh->ref_processor(); 750 shenandoah_assert_rp_isalive_installed(); 751 752 scm->mark_loop(0, &terminator, rp, 753 false, // not cancellable 754 false); // do not do strdedup 755 } 756 }; 757 758 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure { 759 private: 760 ShenandoahObjToScanQueue* _queue; 761 ShenandoahHeap* _heap; 762 ShenandoahMarkingContext* const _mark_context; 763 764 template <class T> 765 inline void do_oop_work(T* p) { 766 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context); 767 } 768 769 public: 770 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) : 771 _queue(q), 772 _heap(ShenandoahHeap::heap()), 773 _mark_context(_heap->marking_context()) {} 774 775 void do_oop(narrowOop* p) { do_oop_work(p); } 776 void do_oop(oop* p) { do_oop_work(p); } 777 }; 778 779 class ShenandoahPrecleanTask : public AbstractGangTask { 780 private: 781 ReferenceProcessor* _rp; 782 783 public: 784 ShenandoahPrecleanTask(ReferenceProcessor* rp) : 785 AbstractGangTask("Precleaning task"), 786 _rp(rp) {} 787 788 void work(uint worker_id) { 789 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected"); 790 ShenandoahParallelWorkerSession worker_session(worker_id); 791 792 ShenandoahHeap* sh = ShenandoahHeap::heap(); 793 794 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id); 795 796 ShenandoahCancelledGCYieldClosure yield; 797 ShenandoahPrecleanCompleteGCClosure complete_gc; 798 799 if (sh->has_forwarded_objects()) { 800 ShenandoahForwardedIsAliveClosure is_alive; 801 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q); 802 ResourceMark rm; 803 _rp->preclean_discovered_references(&is_alive, &keep_alive, 804 &complete_gc, &yield, 805 NULL); 806 } else { 807 ShenandoahIsAliveClosure is_alive; 808 ShenandoahCMKeepAliveClosure keep_alive(q); 809 ResourceMark rm; 810 _rp->preclean_discovered_references(&is_alive, &keep_alive, 811 &complete_gc, &yield, 812 NULL); 813 } 814 } 815 }; 816 817 void ShenandoahConcurrentMark::preclean_weak_refs() { 818 // Pre-cleaning weak references before diving into STW makes sense at the 819 // end of concurrent mark. This will filter out the references which referents 820 // are alive. Note that ReferenceProcessor already filters out these on reference 821 // discovery, and the bulk of work is done here. This phase processes leftovers 822 // that missed the initial filtering, i.e. when referent was marked alive after 823 // reference was discovered by RP. 824 825 assert(_heap->process_references(), "sanity"); 826 827 // Shortcut if no references were discovered to avoid winding up threads. 828 ReferenceProcessor* rp = _heap->ref_processor(); 829 if (!rp->has_discovered_references()) { 830 return; 831 } 832 833 assert(task_queues()->is_empty(), "Should be empty"); 834 835 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false); 836 837 shenandoah_assert_rp_isalive_not_installed(); 838 ShenandoahIsAliveSelector is_alive; 839 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure()); 840 841 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup 842 // queues and other goodies. When upstream ReferenceProcessor starts supporting 843 // parallel precleans, we can extend this to more threads. 844 WorkGang* workers = _heap->workers(); 845 uint nworkers = workers->active_workers(); 846 assert(nworkers == 1, "This code uses only a single worker"); 847 task_queues()->reserve(nworkers); 848 849 ShenandoahPrecleanTask task(rp); 850 workers->run_task(&task); 851 852 assert(task_queues()->is_empty(), "Should be empty"); 853 } 854 855 void ShenandoahConcurrentMark::cancel() { 856 // Clean up marking stacks. 857 ShenandoahObjToScanQueueSet* queues = task_queues(); 858 queues->clear(); 859 860 // Cancel SATB buffers. 861 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking(); 862 } 863 864 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) { 865 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id); 866 return _task_queues->queue(worker_id); 867 } 868 869 template <bool CANCELLABLE> 870 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp, 871 bool strdedup) { 872 ShenandoahObjToScanQueue* q = get_queue(w); 873 874 jushort* ld = _heap->get_liveness_cache(w); 875 876 // TODO: We can clean up this if we figure out how to do templated oop closures that 877 // play nice with specialized_oop_iterators. 878 if (_heap->unload_classes()) { 879 if (_heap->has_forwarded_objects()) { 880 if (strdedup) { 881 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp); 882 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t); 883 } else { 884 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp); 885 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t); 886 } 887 } else { 888 if (strdedup) { 889 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp); 890 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t); 891 } else { 892 ShenandoahMarkRefsMetadataClosure cl(q, rp); 893 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t); 894 } 895 } 896 } else { 897 if (_heap->has_forwarded_objects()) { 898 if (strdedup) { 899 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp); 900 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t); 901 } else { 902 ShenandoahMarkUpdateRefsClosure cl(q, rp); 903 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t); 904 } 905 } else { 906 if (strdedup) { 907 ShenandoahMarkRefsDedupClosure cl(q, rp); 908 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t); 909 } else { 910 ShenandoahMarkRefsClosure cl(q, rp); 911 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t); 912 } 913 } 914 } 915 916 _heap->flush_liveness_cache(w); 917 } 918 919 template <class T, bool CANCELLABLE> 920 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) { 921 uintx stride = ShenandoahMarkLoopStride; 922 923 ShenandoahHeap* heap = ShenandoahHeap::heap(); 924 ShenandoahObjToScanQueueSet* queues = task_queues(); 925 ShenandoahObjToScanQueue* q; 926 ShenandoahMarkTask t; 927 928 /* 929 * Process outstanding queues, if any. 930 * 931 * There can be more queues than workers. To deal with the imbalance, we claim 932 * extra queues first. Since marking can push new tasks into the queue associated 933 * with this worker id, we come back to process this queue in the normal loop. 934 */ 935 assert(queues->get_reserved() == heap->workers()->active_workers(), 936 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers()); 937 938 q = queues->claim_next(); 939 while (q != NULL) { 940 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) { 941 return; 942 } 943 944 for (uint i = 0; i < stride; i++) { 945 if (q->pop(t)) { 946 do_task<T>(q, cl, live_data, &t); 947 } else { 948 assert(q->is_empty(), "Must be empty"); 949 q = queues->claim_next(); 950 break; 951 } 952 } 953 } 954 q = get_queue(worker_id); 955 956 ShenandoahSATBBufferClosure drain_satb(q); 957 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set(); 958 959 /* 960 * Normal marking loop: 961 */ 962 while (true) { 963 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) { 964 return; 965 } 966 967 while (satb_mq_set.completed_buffers_num() > 0) { 968 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb); 969 } 970 971 uint work = 0; 972 for (uint i = 0; i < stride; i++) { 973 if (q->pop(t) || 974 queues->steal(worker_id, t)) { 975 do_task<T>(q, cl, live_data, &t); 976 work++; 977 } else { 978 break; 979 } 980 } 981 982 if (work == 0) { 983 // No work encountered in current stride, try to terminate. 984 // Need to leave the STS here otherwise it might block safepoints. 985 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers); 986 ShenandoahTerminationTimingsTracker term_tracker(worker_id); 987 ShenandoahTerminatorTerminator tt(heap); 988 if (terminator->offer_termination(&tt)) return; 989 } 990 } 991 } 992 993 bool ShenandoahConcurrentMark::claim_codecache() { 994 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise"); 995 return _claimed_codecache.try_set(); 996 } 997 998 void ShenandoahConcurrentMark::clear_claim_codecache() { 999 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise"); 1000 _claimed_codecache.unset(); 1001 }