1 /* 2 * Copyright (c) 2013, 2018, 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.hpp" 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 36 #include "gc/shenandoah/shenandoahBarrierSet.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.hpp" 41 #include "gc/shenandoah/shenandoahOopClosures.hpp" 42 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp" 43 #include "gc/shenandoah/shenandoahTaskqueue.hpp" 44 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp" 45 #include "gc/shenandoah/shenandoahTimingTracker.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 53 template<UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP> 54 class ShenandoahInitMarkRootsClosure : public OopClosure { 55 private: 56 ShenandoahObjToScanQueue* _queue; 57 ShenandoahHeap* _heap; 58 ShenandoahMarkingContext* const _mark_context; 59 60 template <class T> 61 inline void do_oop_work(T* p) { 62 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, STRING_DEDUP>(p, _heap, _queue, _mark_context); 63 } 64 65 public: 66 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) : 67 _queue(q), 68 _heap(ShenandoahHeap::heap()), 69 _mark_context(_heap->marking_context()) {}; 70 71 void do_oop(narrowOop* p) { do_oop_work(p); } 72 void do_oop(oop* p) { do_oop_work(p); } 73 }; 74 75 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) : 76 MetadataVisitingOopIterateClosure(rp), 77 _queue(q), 78 _heap(ShenandoahHeap::heap()), 79 _mark_context(_heap->marking_context()) 80 { } 81 82 template<UpdateRefsMode UPDATE_REFS> 83 class ShenandoahInitMarkRootsTask : public AbstractGangTask { 84 private: 85 ShenandoahRootProcessor* _rp; 86 bool _process_refs; 87 public: 88 ShenandoahInitMarkRootsTask(ShenandoahRootProcessor* rp, bool process_refs) : 89 AbstractGangTask("Shenandoah init mark roots task"), 90 _rp(rp), 91 _process_refs(process_refs) { 92 } 93 94 void work(uint worker_id) { 95 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 96 ShenandoahParallelWorkerSession worker_session(worker_id); 97 98 ShenandoahHeap* heap = ShenandoahHeap::heap(); 99 ShenandoahObjToScanQueueSet* queues = heap->concurrent_mark()->task_queues(); 100 assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id); 101 102 ShenandoahObjToScanQueue* q = queues->queue(worker_id); 103 104 if (ShenandoahStringDedup::is_enabled()) { 105 ShenandoahInitMarkRootsClosure<UPDATE_REFS, ENQUEUE_DEDUP> mark_cl(q); 106 do_work(heap, &mark_cl, worker_id); 107 } else { 108 ShenandoahInitMarkRootsClosure<UPDATE_REFS, NO_DEDUP> mark_cl(q); 109 do_work(heap, &mark_cl, worker_id); 110 } 111 } 112 113 private: 114 void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) { 115 // The rationale for selecting the roots to scan is as follows: 116 // a. With unload_classes = true, we only want to scan the actual strong roots from the 117 // code cache. This will allow us to identify the dead classes, unload them, *and* 118 // invalidate the relevant code cache blobs. This could be only done together with 119 // class unloading. 120 // b. With unload_classes = false, we have to nominally retain all the references from code 121 // cache, because there could be the case of embedded class/oop in the generated code, 122 // which we will never visit during mark. Without code cache invalidation, as in (a), 123 // we risk executing that code cache blob, and crashing. 124 // c. With ShenandoahConcurrentScanCodeRoots, we avoid scanning the entire code cache here, 125 // and instead do that in concurrent phase under the relevant lock. This saves init mark 126 // pause time. 127 128 CLDToOopClosure clds_cl(oops, ClassLoaderData::_claim_strong); 129 MarkingCodeBlobClosure blobs_cl(oops, ! CodeBlobToOopClosure::FixRelocations); 130 OopClosure* weak_oops = _process_refs ? NULL : oops; 131 132 ResourceMark m; 133 if (heap->unload_classes()) { 134 _rp->process_strong_roots(oops, weak_oops, &clds_cl, NULL, &blobs_cl, NULL, worker_id); 135 } else { 136 if (ShenandoahConcurrentScanCodeRoots) { 137 CodeBlobClosure* code_blobs = NULL; 138 #ifdef ASSERT 139 ShenandoahAssertToSpaceClosure assert_to_space_oops; 140 CodeBlobToOopClosure assert_to_space(&assert_to_space_oops, !CodeBlobToOopClosure::FixRelocations); 141 // If conc code cache evac is disabled, code cache should have only to-space ptrs. 142 // Otherwise, it should have to-space ptrs only if mark does not update refs. 143 if (!heap->has_forwarded_objects()) { 144 code_blobs = &assert_to_space; 145 } 146 #endif 147 _rp->process_all_roots(oops, weak_oops, &clds_cl, code_blobs, NULL, worker_id); 148 } else { 149 _rp->process_all_roots(oops, weak_oops, &clds_cl, &blobs_cl, NULL, worker_id); 150 } 151 } 152 } 153 }; 154 155 class ShenandoahUpdateRootsTask : public AbstractGangTask { 156 private: 157 ShenandoahRootProcessor* _rp; 158 const bool _update_code_cache; 159 public: 160 ShenandoahUpdateRootsTask(ShenandoahRootProcessor* rp, bool update_code_cache) : 161 AbstractGangTask("Shenandoah update roots task"), 162 _rp(rp), 163 _update_code_cache(update_code_cache) { 164 } 165 166 void work(uint worker_id) { 167 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 168 ShenandoahParallelWorkerSession worker_session(worker_id); 169 170 ShenandoahHeap* heap = ShenandoahHeap::heap(); 171 ShenandoahUpdateRefsClosure cl; 172 CLDToOopClosure cldCl(&cl, ClassLoaderData::_claim_strong); 173 174 CodeBlobClosure* code_blobs; 175 CodeBlobToOopClosure update_blobs(&cl, CodeBlobToOopClosure::FixRelocations); 176 #ifdef ASSERT 177 ShenandoahAssertToSpaceClosure assert_to_space_oops; 178 CodeBlobToOopClosure assert_to_space(&assert_to_space_oops, !CodeBlobToOopClosure::FixRelocations); 179 #endif 180 if (_update_code_cache) { 181 code_blobs = &update_blobs; 182 } else { 183 code_blobs = 184 DEBUG_ONLY(&assert_to_space) 185 NOT_DEBUG(NULL); 186 } 187 _rp->process_all_roots(&cl, &cl, &cldCl, code_blobs, NULL, worker_id); 188 } 189 }; 190 191 class ShenandoahConcurrentMarkingTask : public AbstractGangTask { 192 private: 193 ShenandoahConcurrentMark* _cm; 194 ShenandoahTaskTerminator* _terminator; 195 196 public: 197 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator) : 198 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) { 199 } 200 201 void work(uint worker_id) { 202 ShenandoahHeap* heap = ShenandoahHeap::heap(); 203 ShenandoahConcurrentWorkerSession worker_session(worker_id); 204 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers); 205 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id); 206 ReferenceProcessor* rp; 207 if (heap->process_references()) { 208 rp = heap->ref_processor(); 209 shenandoah_assert_rp_isalive_installed(); 210 } else { 211 rp = NULL; 212 } 213 214 _cm->concurrent_scan_code_roots(worker_id, rp); 215 _cm->mark_loop(worker_id, _terminator, rp, 216 true, // cancellable 217 ShenandoahStringDedup::is_enabled()); // perform string dedup 218 } 219 }; 220 221 class ShenandoahSATBThreadsClosure : public ThreadClosure { 222 private: 223 ShenandoahSATBBufferClosure* _satb_cl; 224 int _thread_parity; 225 226 public: 227 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) : 228 _satb_cl(satb_cl), 229 _thread_parity(Threads::thread_claim_parity()) {} 230 231 void do_thread(Thread* thread) { 232 if (thread->is_Java_thread()) { 233 if (thread->claim_oops_do(true, _thread_parity)) { 234 JavaThread* jt = (JavaThread*)thread; 235 ShenandoahThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(_satb_cl); 236 } 237 } else if (thread->is_VM_thread()) { 238 if (thread->claim_oops_do(true, _thread_parity)) { 239 ShenandoahBarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(_satb_cl); 240 } 241 } 242 } 243 }; 244 245 class ShenandoahFinalMarkingTask : public AbstractGangTask { 246 private: 247 ShenandoahConcurrentMark* _cm; 248 ShenandoahTaskTerminator* _terminator; 249 bool _dedup_string; 250 251 public: 252 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) : 253 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) { 254 } 255 256 void work(uint worker_id) { 257 ShenandoahHeap* heap = ShenandoahHeap::heap(); 258 259 ShenandoahParallelWorkerSession worker_session(worker_id); 260 // First drain remaining SATB buffers. 261 // Notice that this is not strictly necessary for mark-compact. But since 262 // it requires a StrongRootsScope around the task, we need to claim the 263 // threads, and performance-wise it doesn't really matter. Adds about 1ms to 264 // full-gc. 265 { 266 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id); 267 ShenandoahSATBBufferClosure cl(q); 268 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set(); 269 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)); 270 ShenandoahSATBThreadsClosure tc(&cl); 271 Threads::threads_do(&tc); 272 } 273 274 ReferenceProcessor* rp; 275 if (heap->process_references()) { 276 rp = heap->ref_processor(); 277 shenandoah_assert_rp_isalive_installed(); 278 } else { 279 rp = NULL; 280 } 281 282 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned, 283 // let's check here. 284 _cm->concurrent_scan_code_roots(worker_id, rp); 285 _cm->mark_loop(worker_id, _terminator, rp, 286 false, // not cancellable 287 _dedup_string); 288 289 assert(_cm->task_queues()->is_empty(), "Should be empty"); 290 } 291 }; 292 293 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) { 294 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread"); 295 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 296 297 ShenandoahHeap* heap = ShenandoahHeap::heap(); 298 299 ShenandoahGCPhase phase(root_phase); 300 301 WorkGang* workers = heap->workers(); 302 uint nworkers = workers->active_workers(); 303 304 assert(nworkers <= task_queues()->size(), "Just check"); 305 306 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase); 307 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats()); 308 task_queues()->reserve(nworkers); 309 310 if (heap->has_forwarded_objects()) { 311 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references()); 312 workers->run_task(&mark_roots); 313 } else { 314 // No need to update references, which means the heap is stable. 315 // Can save time not walking through forwarding pointers. 316 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references()); 317 workers->run_task(&mark_roots); 318 } 319 320 if (ShenandoahConcurrentScanCodeRoots) { 321 clear_claim_codecache(); 322 } 323 } 324 325 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) { 326 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 327 328 bool update_code_cache = true; // initialize to safer value 329 switch (root_phase) { 330 case ShenandoahPhaseTimings::update_roots: 331 case ShenandoahPhaseTimings::final_update_refs_roots: 332 update_code_cache = false; 333 break; 334 case ShenandoahPhaseTimings::full_gc_roots: 335 case ShenandoahPhaseTimings::degen_gc_update_roots: 336 update_code_cache = true; 337 break; 338 default: 339 ShouldNotReachHere(); 340 } 341 342 ShenandoahGCPhase phase(root_phase); 343 344 #if defined(COMPILER2) || INCLUDE_JVMCI 345 DerivedPointerTable::clear(); 346 #endif 347 348 uint nworkers = _heap->workers()->active_workers(); 349 350 ShenandoahRootProcessor root_proc(_heap, nworkers, root_phase); 351 ShenandoahUpdateRootsTask update_roots(&root_proc, update_code_cache); 352 _heap->workers()->run_task(&update_roots); 353 354 #if defined(COMPILER2) || INCLUDE_JVMCI 355 DerivedPointerTable::update_pointers(); 356 #endif 357 } 358 359 void ShenandoahConcurrentMark::initialize(uint workers) { 360 _heap = ShenandoahHeap::heap(); 361 362 uint num_queues = MAX2(workers, 1U); 363 364 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues); 365 366 for (uint i = 0; i < num_queues; ++i) { 367 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue(); 368 task_queue->initialize(); 369 _task_queues->register_queue(i, task_queue); 370 } 371 } 372 373 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) { 374 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) { 375 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id); 376 if (!_heap->unload_classes()) { 377 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 378 // TODO: We can not honor StringDeduplication here, due to lock ranking 379 // inversion. So, we may miss some deduplication candidates. 380 if (_heap->has_forwarded_objects()) { 381 ShenandoahMarkResolveRefsClosure cl(q, rp); 382 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations); 383 CodeCache::blobs_do(&blobs); 384 } else { 385 ShenandoahMarkRefsClosure cl(q, rp); 386 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations); 387 CodeCache::blobs_do(&blobs); 388 } 389 } 390 } 391 } 392 393 void ShenandoahConcurrentMark::mark_from_roots() { 394 WorkGang* workers = _heap->workers(); 395 uint nworkers = workers->active_workers(); 396 397 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark); 398 399 if (_heap->process_references()) { 400 ReferenceProcessor* rp = _heap->ref_processor(); 401 rp->set_active_mt_degree(nworkers); 402 403 // enable ("weak") refs discovery 404 rp->enable_discovery(true /*verify_no_refs*/); 405 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs()); 406 } 407 408 shenandoah_assert_rp_isalive_not_installed(); 409 ShenandoahIsAliveSelector is_alive; 410 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure()); 411 412 task_queues()->reserve(nworkers); 413 414 { 415 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination); 416 ShenandoahTaskTerminator terminator(nworkers, task_queues()); 417 ShenandoahConcurrentMarkingTask task(this, &terminator); 418 workers->run_task(&task); 419 } 420 421 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled"); 422 } 423 424 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) { 425 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 426 427 uint nworkers = _heap->workers()->active_workers(); 428 429 // Finally mark everything else we've got in our queues during the previous steps. 430 // It does two different things for concurrent vs. mark-compact GC: 431 // - For concurrent GC, it starts with empty task queues, drains the remaining 432 // SATB buffers, and then completes the marking closure. 433 // - For mark-compact GC, it starts out with the task queues seeded by initial 434 // root scan, and completes the closure, thus marking through all live objects 435 // The implementation is the same, so it's shared here. 436 { 437 ShenandoahGCPhase phase(full_gc ? 438 ShenandoahPhaseTimings::full_gc_mark_finish_queues : 439 ShenandoahPhaseTimings::finish_queues); 440 task_queues()->reserve(nworkers); 441 442 shenandoah_assert_rp_isalive_not_installed(); 443 ShenandoahIsAliveSelector is_alive; 444 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure()); 445 446 ShenandoahTerminationTracker termination_tracker(full_gc ? 447 ShenandoahPhaseTimings::full_gc_mark_termination : 448 ShenandoahPhaseTimings::termination); 449 450 StrongRootsScope scope(nworkers); 451 ShenandoahTaskTerminator terminator(nworkers, task_queues()); 452 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled()); 453 _heap->workers()->run_task(&task); 454 } 455 456 assert(task_queues()->is_empty(), "Should be empty"); 457 458 // When we're done marking everything, we process weak references. 459 if (_heap->process_references()) { 460 weak_refs_work(full_gc); 461 } 462 463 // And finally finish class unloading 464 if (_heap->unload_classes()) { 465 _heap->unload_classes_and_cleanup_tables(full_gc); 466 } 467 468 assert(task_queues()->is_empty(), "Should be empty"); 469 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats()); 470 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats()); 471 472 // Resize Metaspace 473 MetaspaceGC::compute_new_size(); 474 } 475 476 // Weak Reference Closures 477 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure { 478 uint _worker_id; 479 ShenandoahTaskTerminator* _terminator; 480 bool _reset_terminator; 481 482 public: 483 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false): 484 _worker_id(worker_id), 485 _terminator(t), 486 _reset_terminator(reset_terminator) { 487 } 488 489 void do_void() { 490 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 491 492 ShenandoahHeap* sh = ShenandoahHeap::heap(); 493 ShenandoahConcurrentMark* scm = sh->concurrent_mark(); 494 assert(sh->process_references(), "why else would we be here?"); 495 ReferenceProcessor* rp = sh->ref_processor(); 496 497 shenandoah_assert_rp_isalive_installed(); 498 499 scm->mark_loop(_worker_id, _terminator, rp, 500 false, // not cancellable 501 false); // do not do strdedup 502 503 if (_reset_terminator) { 504 _terminator->reset_for_reuse(); 505 } 506 } 507 }; 508 509 class ShenandoahCMKeepAliveClosure : public OopClosure { 510 private: 511 ShenandoahObjToScanQueue* _queue; 512 ShenandoahHeap* _heap; 513 ShenandoahMarkingContext* const _mark_context; 514 515 template <class T> 516 inline void do_oop_work(T* p) { 517 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context); 518 } 519 520 public: 521 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) : 522 _queue(q), 523 _heap(ShenandoahHeap::heap()), 524 _mark_context(_heap->marking_context()) {} 525 526 void do_oop(narrowOop* p) { do_oop_work(p); } 527 void do_oop(oop* p) { do_oop_work(p); } 528 }; 529 530 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure { 531 private: 532 ShenandoahObjToScanQueue* _queue; 533 ShenandoahHeap* _heap; 534 ShenandoahMarkingContext* const _mark_context; 535 536 template <class T> 537 inline void do_oop_work(T* p) { 538 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context); 539 } 540 541 public: 542 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) : 543 _queue(q), 544 _heap(ShenandoahHeap::heap()), 545 _mark_context(_heap->marking_context()) {} 546 547 void do_oop(narrowOop* p) { do_oop_work(p); } 548 void do_oop(oop* p) { do_oop_work(p); } 549 }; 550 551 class ShenandoahWeakUpdateClosure : public OopClosure { 552 private: 553 ShenandoahHeap* const _heap; 554 555 template <class T> 556 inline void do_oop_work(T* p) { 557 oop o = _heap->maybe_update_with_forwarded(p); 558 shenandoah_assert_marked_except(p, o, o == NULL); 559 } 560 561 public: 562 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {} 563 564 void do_oop(narrowOop* p) { do_oop_work(p); } 565 void do_oop(oop* p) { do_oop_work(p); } 566 }; 567 568 class ShenandoahWeakAssertNotForwardedClosure : public OopClosure { 569 private: 570 template <class T> 571 inline void do_oop_work(T* p) { 572 T o = RawAccess<>::oop_load(p); 573 if (!CompressedOops::is_null(o)) { 574 oop obj = CompressedOops::decode_not_null(o); 575 shenandoah_assert_not_forwarded(p, obj); 576 } 577 } 578 579 public: 580 ShenandoahWeakAssertNotForwardedClosure() {} 581 582 void do_oop(narrowOop* p) { do_oop_work(p); } 583 void do_oop(oop* p) { do_oop_work(p); } 584 }; 585 586 class ShenandoahRefProcTaskProxy : public AbstractGangTask { 587 private: 588 AbstractRefProcTaskExecutor::ProcessTask& _proc_task; 589 ShenandoahTaskTerminator* _terminator; 590 591 public: 592 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task, 593 ShenandoahTaskTerminator* t) : 594 AbstractGangTask("Process reference objects in parallel"), 595 _proc_task(proc_task), 596 _terminator(t) { 597 } 598 599 void work(uint worker_id) { 600 ResourceMark rm; 601 HandleMark hm; 602 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 603 ShenandoahHeap* heap = ShenandoahHeap::heap(); 604 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator); 605 if (heap->has_forwarded_objects()) { 606 ShenandoahForwardedIsAliveClosure is_alive; 607 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id)); 608 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc); 609 } else { 610 ShenandoahIsAliveClosure is_alive; 611 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id)); 612 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc); 613 } 614 } 615 }; 616 617 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor { 618 private: 619 WorkGang* _workers; 620 621 public: 622 ShenandoahRefProcTaskExecutor(WorkGang* workers) : 623 _workers(workers) { 624 } 625 626 // Executes a task using worker threads. 627 void execute(ProcessTask& task, uint ergo_workers) { 628 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 629 630 ShenandoahHeap* heap = ShenandoahHeap::heap(); 631 ShenandoahConcurrentMark* cm = heap->concurrent_mark(); 632 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(), 633 ergo_workers, 634 /* do_check = */ false); 635 uint nworkers = _workers->active_workers(); 636 cm->task_queues()->reserve(nworkers); 637 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues()); 638 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator); 639 _workers->run_task(&proc_task_proxy); 640 } 641 }; 642 643 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) { 644 assert(_heap->process_references(), "sanity"); 645 646 ShenandoahPhaseTimings::Phase phase_root = 647 full_gc ? 648 ShenandoahPhaseTimings::full_gc_weakrefs : 649 ShenandoahPhaseTimings::weakrefs; 650 651 ShenandoahGCPhase phase(phase_root); 652 653 ReferenceProcessor* rp = _heap->ref_processor(); 654 655 // NOTE: We cannot shortcut on has_discovered_references() here, because 656 // we will miss marking JNI Weak refs then, see implementation in 657 // ReferenceProcessor::process_discovered_references. 658 weak_refs_work_doit(full_gc); 659 660 rp->verify_no_references_recorded(); 661 assert(!rp->discovery_enabled(), "Post condition"); 662 663 } 664 665 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) { 666 ReferenceProcessor* rp = _heap->ref_processor(); 667 668 ShenandoahPhaseTimings::Phase phase_process = 669 full_gc ? 670 ShenandoahPhaseTimings::full_gc_weakrefs_process : 671 ShenandoahPhaseTimings::weakrefs_process; 672 673 ShenandoahPhaseTimings::Phase phase_process_termination = 674 full_gc ? 675 ShenandoahPhaseTimings::full_gc_weakrefs_termination : 676 ShenandoahPhaseTimings::weakrefs_termination; 677 678 shenandoah_assert_rp_isalive_not_installed(); 679 ShenandoahIsAliveSelector is_alive; 680 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure()); 681 682 WorkGang* workers = _heap->workers(); 683 uint nworkers = workers->active_workers(); 684 685 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs()); 686 rp->set_active_mt_degree(nworkers); 687 688 assert(task_queues()->is_empty(), "Should be empty"); 689 690 // complete_gc and keep_alive closures instantiated here are only needed for 691 // single-threaded path in RP. They share the queue 0 for tracking work, which 692 // simplifies implementation. Since RP may decide to call complete_gc several 693 // times, we need to be able to reuse the terminator. 694 uint serial_worker_id = 0; 695 ShenandoahTaskTerminator terminator(1, task_queues()); 696 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true); 697 698 ShenandoahRefProcTaskExecutor executor(workers); 699 700 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues()); 701 702 { 703 ShenandoahGCPhase phase(phase_process); 704 ShenandoahTerminationTracker phase_term(phase_process_termination); 705 706 // Process leftover weak oops: update them, if needed (using parallel version), 707 // or assert they do not need updating (using serial version) otherwise. 708 // Weak processor API requires us to visit the oops, even if we are not doing 709 // anything to them. 710 if (_heap->has_forwarded_objects()) { 711 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id)); 712 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive, 713 &complete_gc, &executor, 714 &pt); 715 716 ShenandoahWeakUpdateClosure cl; 717 WeakProcessor::weak_oops_do(workers, is_alive.is_alive_closure(), &cl, 1); 718 } else { 719 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id)); 720 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive, 721 &complete_gc, &executor, 722 &pt); 723 724 ShenandoahWeakAssertNotForwardedClosure cl; 725 WeakProcessor::weak_oops_do(is_alive.is_alive_closure(), &cl); 726 } 727 728 pt.print_all_references(); 729 730 assert(task_queues()->is_empty(), "Should be empty"); 731 } 732 } 733 734 class ShenandoahCancelledGCYieldClosure : public YieldClosure { 735 private: 736 ShenandoahHeap* const _heap; 737 public: 738 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {}; 739 virtual bool should_return() { return _heap->cancelled_gc(); } 740 }; 741 742 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure { 743 public: 744 void do_void() { 745 ShenandoahHeap* sh = ShenandoahHeap::heap(); 746 ShenandoahConcurrentMark* scm = sh->concurrent_mark(); 747 assert(sh->process_references(), "why else would we be here?"); 748 ShenandoahTaskTerminator terminator(1, scm->task_queues()); 749 750 ReferenceProcessor* rp = sh->ref_processor(); 751 shenandoah_assert_rp_isalive_installed(); 752 753 scm->mark_loop(0, &terminator, rp, 754 false, // not cancellable 755 false); // do not do strdedup 756 } 757 }; 758 759 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure { 760 private: 761 ShenandoahObjToScanQueue* _queue; 762 ShenandoahHeap* _heap; 763 ShenandoahMarkingContext* const _mark_context; 764 765 template <class T> 766 inline void do_oop_work(T* p) { 767 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context); 768 } 769 770 public: 771 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) : 772 _queue(q), 773 _heap(ShenandoahHeap::heap()), 774 _mark_context(_heap->marking_context()) {} 775 776 void do_oop(narrowOop* p) { do_oop_work(p); } 777 void do_oop(oop* p) { do_oop_work(p); } 778 }; 779 780 class ShenandoahPrecleanTask : public AbstractGangTask { 781 private: 782 ReferenceProcessor* _rp; 783 784 public: 785 ShenandoahPrecleanTask(ReferenceProcessor* rp) : 786 AbstractGangTask("Precleaning task"), 787 _rp(rp) {} 788 789 void work(uint worker_id) { 790 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected"); 791 ShenandoahParallelWorkerSession worker_session(worker_id); 792 793 ShenandoahHeap* sh = ShenandoahHeap::heap(); 794 795 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id); 796 797 ShenandoahCancelledGCYieldClosure yield; 798 ShenandoahPrecleanCompleteGCClosure complete_gc; 799 800 if (sh->has_forwarded_objects()) { 801 ShenandoahForwardedIsAliveClosure is_alive; 802 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q); 803 ResourceMark rm; 804 _rp->preclean_discovered_references(&is_alive, &keep_alive, 805 &complete_gc, &yield, 806 NULL); 807 } else { 808 ShenandoahIsAliveClosure is_alive; 809 ShenandoahCMKeepAliveClosure keep_alive(q); 810 ResourceMark rm; 811 _rp->preclean_discovered_references(&is_alive, &keep_alive, 812 &complete_gc, &yield, 813 NULL); 814 } 815 } 816 }; 817 818 void ShenandoahConcurrentMark::preclean_weak_refs() { 819 // Pre-cleaning weak references before diving into STW makes sense at the 820 // end of concurrent mark. This will filter out the references which referents 821 // are alive. Note that ReferenceProcessor already filters out these on reference 822 // discovery, and the bulk of work is done here. This phase processes leftovers 823 // that missed the initial filtering, i.e. when referent was marked alive after 824 // reference was discovered by RP. 825 826 assert(_heap->process_references(), "sanity"); 827 828 // Shortcut if no references were discovered to avoid winding up threads. 829 ReferenceProcessor* rp = _heap->ref_processor(); 830 if (!rp->has_discovered_references()) { 831 return; 832 } 833 834 assert(task_queues()->is_empty(), "Should be empty"); 835 836 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false); 837 838 shenandoah_assert_rp_isalive_not_installed(); 839 ShenandoahIsAliveSelector is_alive; 840 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure()); 841 842 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup 843 // queues and other goodies. When upstream ReferenceProcessor starts supporting 844 // parallel precleans, we can extend this to more threads. 845 WorkGang* workers = _heap->workers(); 846 uint nworkers = workers->active_workers(); 847 assert(nworkers == 1, "This code uses only a single worker"); 848 task_queues()->reserve(nworkers); 849 850 ShenandoahPrecleanTask task(rp); 851 workers->run_task(&task); 852 853 assert(task_queues()->is_empty(), "Should be empty"); 854 } 855 856 void ShenandoahConcurrentMark::cancel() { 857 // Clean up marking stacks. 858 ShenandoahObjToScanQueueSet* queues = task_queues(); 859 queues->clear(); 860 861 // Cancel SATB buffers. 862 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking(); 863 } 864 865 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) { 866 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id); 867 return _task_queues->queue(worker_id); 868 } 869 870 template <bool CANCELLABLE> 871 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp, 872 bool strdedup) { 873 ShenandoahObjToScanQueue* q = get_queue(w); 874 875 jushort* ld = _heap->get_liveness_cache(w); 876 877 // TODO: We can clean up this if we figure out how to do templated oop closures that 878 // play nice with specialized_oop_iterators. 879 if (_heap->unload_classes()) { 880 if (_heap->has_forwarded_objects()) { 881 if (strdedup) { 882 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp); 883 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t); 884 } else { 885 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp); 886 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t); 887 } 888 } else { 889 if (strdedup) { 890 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp); 891 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t); 892 } else { 893 ShenandoahMarkRefsMetadataClosure cl(q, rp); 894 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t); 895 } 896 } 897 } else { 898 if (_heap->has_forwarded_objects()) { 899 if (strdedup) { 900 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp); 901 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t); 902 } else { 903 ShenandoahMarkUpdateRefsClosure cl(q, rp); 904 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t); 905 } 906 } else { 907 if (strdedup) { 908 ShenandoahMarkRefsDedupClosure cl(q, rp); 909 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t); 910 } else { 911 ShenandoahMarkRefsClosure cl(q, rp); 912 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t); 913 } 914 } 915 } 916 917 _heap->flush_liveness_cache(w); 918 } 919 920 template <class T, bool CANCELLABLE> 921 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) { 922 uintx stride = ShenandoahMarkLoopStride; 923 924 ShenandoahHeap* heap = ShenandoahHeap::heap(); 925 ShenandoahObjToScanQueueSet* queues = task_queues(); 926 ShenandoahObjToScanQueue* q; 927 ShenandoahMarkTask t; 928 929 /* 930 * Process outstanding queues, if any. 931 * 932 * There can be more queues than workers. To deal with the imbalance, we claim 933 * extra queues first. Since marking can push new tasks into the queue associated 934 * with this worker id, we come back to process this queue in the normal loop. 935 */ 936 assert(queues->get_reserved() == heap->workers()->active_workers(), 937 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers()); 938 939 q = queues->claim_next(); 940 while (q != NULL) { 941 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) { 942 ShenandoahCancelledTerminatorTerminator tt; 943 ShenandoahSuspendibleThreadSetLeaver stsl(ShenandoahSuspendibleWorkers); 944 while (!terminator->offer_termination(&tt)); 945 return; 946 } 947 948 for (uint i = 0; i < stride; i++) { 949 if (q->pop(t)) { 950 do_task<T>(q, cl, live_data, &t); 951 } else { 952 assert(q->is_empty(), "Must be empty"); 953 q = queues->claim_next(); 954 break; 955 } 956 } 957 } 958 q = get_queue(worker_id); 959 960 ShenandoahSATBBufferClosure drain_satb(q); 961 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set(); 962 963 /* 964 * Normal marking loop: 965 */ 966 while (true) { 967 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) { 968 ShenandoahCancelledTerminatorTerminator tt; 969 ShenandoahSuspendibleThreadSetLeaver stsl(ShenandoahSuspendibleWorkers); 970 while (!terminator->offer_termination(&tt)); 971 return; 972 } 973 974 while (satb_mq_set.completed_buffers_num() > 0) { 975 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb); 976 } 977 978 uint work = 0; 979 for (uint i = 0; i < stride; i++) { 980 if (q->pop(t) || 981 queues->steal(worker_id, t)) { 982 do_task<T>(q, cl, live_data, &t); 983 work++; 984 } else { 985 break; 986 } 987 } 988 989 if (work == 0) { 990 // No work encountered in current stride, try to terminate. 991 // Need to leave the STS here otherwise it might block safepoints. 992 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers); 993 ShenandoahTerminationTimingsTracker term_tracker(worker_id); 994 if (terminator->offer_termination()) return; 995 } 996 } 997 } 998 999 bool ShenandoahConcurrentMark::claim_codecache() { 1000 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise"); 1001 return _claimed_codecache.try_set(); 1002 } 1003 1004 void ShenandoahConcurrentMark::clear_claim_codecache() { 1005 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise"); 1006 _claimed_codecache.unset(); 1007 }