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 #include "gc/shared/strongRootsScope.hpp"
35
36 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
37 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
38 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
39 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
40 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
41 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
42 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
43 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
44 #include "gc/shenandoah/shenandoahTimingTracker.hpp"
45 #include "gc/shenandoah/shenandoahUtils.hpp"
46
47 #include "memory/iterator.inline.hpp"
48 #include "memory/metaspace.hpp"
49 #include "memory/resourceArea.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "runtime/handles.inline.hpp"
52
53 template<UpdateRefsMode UPDATE_REFS>
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, NO_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 ShenandoahAllRootScanner* _rp;
86 bool _process_refs;
87 public:
88 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* 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 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
105 do_work(heap, &mark_cl, worker_id);
106 }
107
108 private:
109 void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) {
110 // The rationale for selecting the roots to scan is as follows:
111 // a. With unload_classes = true, we only want to scan the actual strong roots from the
112 // code cache. This will allow us to identify the dead classes, unload them, *and*
113 // invalidate the relevant code cache blobs. This could be only done together with
114 // class unloading.
115 // b. With unload_classes = false, we have to nominally retain all the references from code
116 // cache, because there could be the case of embedded class/oop in the generated code,
117 // which we will never visit during mark. Without code cache invalidation, as in (a),
118 // we risk executing that code cache blob, and crashing.
119 if (heap->unload_classes()) {
120 _rp->strong_roots_do(worker_id, oops);
121 } else {
122 _rp->roots_do(worker_id, oops);
123 }
124 }
125 };
126
127 class ShenandoahUpdateRootsTask : public AbstractGangTask {
128 private:
129 ShenandoahRootUpdater* _root_updater;
130 public:
131 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater) :
132 AbstractGangTask("Shenandoah update roots task"),
133 _root_updater(root_updater) {
134 }
135
136 void work(uint worker_id) {
137 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
138 ShenandoahParallelWorkerSession worker_session(worker_id);
139
140 ShenandoahHeap* heap = ShenandoahHeap::heap();
141 ShenandoahUpdateRefsClosure cl;
142 AlwaysTrueClosure always_true;
143 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
144 }
145 };
146
147 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
148 private:
149 ShenandoahConcurrentMark* _cm;
150 ShenandoahTaskTerminator* _terminator;
151
152 public:
153 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator) :
154 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) {
155 }
156
157 void work(uint worker_id) {
158 ShenandoahHeap* heap = ShenandoahHeap::heap();
159 ShenandoahConcurrentWorkerSession worker_session(worker_id);
160 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
161 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
162 ReferenceProcessor* rp;
163 if (heap->process_references()) {
164 rp = heap->ref_processor();
165 shenandoah_assert_rp_isalive_installed();
166 } else {
167 rp = NULL;
168 }
169
170 _cm->concurrent_scan_code_roots(worker_id, rp);
171 _cm->mark_loop(worker_id, _terminator, rp,
172 true, // cancellable
173 ShenandoahStringDedup::is_enabled()); // perform string dedup
174 }
175 };
176
177 class ShenandoahSATBThreadsClosure : public ThreadClosure {
178 private:
179 ShenandoahSATBBufferClosure* _satb_cl;
180 uintx _claim_token;
181
182 public:
183 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
184 _satb_cl(satb_cl),
185 _claim_token(Threads::thread_claim_token()) {}
186
187 void do_thread(Thread* thread) {
188 if (thread->claim_threads_do(true, _claim_token)) {
189 ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl);
190 }
191 }
192 };
193
194 class ShenandoahFinalMarkingTask : public AbstractGangTask {
195 private:
196 ShenandoahConcurrentMark* _cm;
197 ShenandoahTaskTerminator* _terminator;
198 bool _dedup_string;
199
200 public:
201 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) :
202 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
203 }
204
205 void work(uint worker_id) {
206 ShenandoahHeap* heap = ShenandoahHeap::heap();
207
208 ShenandoahParallelWorkerSession worker_session(worker_id);
209 // First drain remaining SATB buffers.
210 // Notice that this is not strictly necessary for mark-compact. But since
211 // it requires a StrongRootsScope around the task, we need to claim the
212 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
213 // full-gc.
214 {
215 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
216 ShenandoahSATBBufferClosure cl(q);
217 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
218 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
219 ShenandoahSATBThreadsClosure tc(&cl);
220 Threads::threads_do(&tc);
221 }
222
223 ReferenceProcessor* rp;
224 if (heap->process_references()) {
225 rp = heap->ref_processor();
226 shenandoah_assert_rp_isalive_installed();
227 } else {
228 rp = NULL;
229 }
230
231 if (heap->is_degenerated_gc_in_progress()) {
232 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
233 // let's check here.
234 _cm->concurrent_scan_code_roots(worker_id, rp);
235 }
236
237 _cm->mark_loop(worker_id, _terminator, rp,
238 false, // not cancellable
239 _dedup_string);
240
241 assert(_cm->task_queues()->is_empty(), "Should be empty");
242 }
243 };
244
245 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
246 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
247 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
248
249 ShenandoahHeap* heap = ShenandoahHeap::heap();
250
251 ShenandoahGCPhase phase(root_phase);
252
253 WorkGang* workers = heap->workers();
254 uint nworkers = workers->active_workers();
255
256 assert(nworkers <= task_queues()->size(), "Just check");
257
258 ShenandoahAllRootScanner root_proc(nworkers, root_phase);
259 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
260 task_queues()->reserve(nworkers);
261
262 if (heap->has_forwarded_objects()) {
263 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references());
264 workers->run_task(&mark_roots);
265 } else {
266 // No need to update references, which means the heap is stable.
267 // Can save time not walking through forwarding pointers.
268 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references());
269 workers->run_task(&mark_roots);
270 }
271
272 if (ShenandoahConcurrentScanCodeRoots) {
273 clear_claim_codecache();
274 }
275 }
276
277 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
278 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
279 assert(root_phase == ShenandoahPhaseTimings::full_gc_roots ||
280 root_phase == ShenandoahPhaseTimings::degen_gc_update_roots,
281 "Only for these phases");
282
283 ShenandoahGCPhase phase(root_phase);
284
285 #if COMPILER2_OR_JVMCI
286 DerivedPointerTable::clear();
287 #endif
288
289 uint nworkers = _heap->workers()->active_workers();
290
291 ShenandoahRootUpdater root_updater(nworkers, root_phase);
292 ShenandoahUpdateRootsTask update_roots(&root_updater);
293 _heap->workers()->run_task(&update_roots);
294
295 #if COMPILER2_OR_JVMCI
296 DerivedPointerTable::update_pointers();
297 #endif
298 }
299
300 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask {
301 private:
302 ShenandoahThreadRoots _thread_roots;
303 ShenandoahPhaseTimings::Phase _phase;
304 public:
305 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) :
306 AbstractGangTask("Shenandoah Update Thread Roots"),
307 _thread_roots(is_par),
308 _phase(phase) {
309 ShenandoahHeap::heap()->phase_timings()->record_workers_start(_phase);
310 }
311
312 ~ShenandoahUpdateThreadRootsTask() {
313 ShenandoahHeap::heap()->phase_timings()->record_workers_end(_phase);
314 }
315 void work(uint worker_id) {
316 ShenandoahUpdateRefsClosure cl;
317 _thread_roots.oops_do(&cl, NULL, worker_id);
318 }
319 };
320
321 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) {
322 WorkGang* workers = _heap->workers();
323 bool is_par = workers->active_workers() > 1;
324 #if COMPILER2_OR_JVMCI
325 DerivedPointerTable::clear();
326 #endif
327 ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
328 workers->run_task(&task);
329 #if COMPILER2_OR_JVMCI
330 DerivedPointerTable::update_pointers();
331 #endif
332 }
333
334 void ShenandoahConcurrentMark::initialize(uint workers) {
335 _heap = ShenandoahHeap::heap();
336
337 uint num_queues = MAX2(workers, 1U);
338
339 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
340
341 for (uint i = 0; i < num_queues; ++i) {
342 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
343 task_queue->initialize();
344 _task_queues->register_queue(i, task_queue);
345 }
346 }
347
348 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
349 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
350 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
351 if (!_heap->unload_classes()) {
352 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
353 // TODO: We can not honor StringDeduplication here, due to lock ranking
354 // inversion. So, we may miss some deduplication candidates.
355 if (_heap->has_forwarded_objects()) {
356 ShenandoahMarkResolveRefsClosure cl(q, rp);
357 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
358 CodeCache::blobs_do(&blobs);
359 } else {
360 ShenandoahMarkRefsClosure cl(q, rp);
361 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
362 CodeCache::blobs_do(&blobs);
363 }
364 }
365 }
366 }
367
368 void ShenandoahConcurrentMark::mark_from_roots() {
369 WorkGang* workers = _heap->workers();
370 uint nworkers = workers->active_workers();
371
372 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
373
374 if (_heap->process_references()) {
375 ReferenceProcessor* rp = _heap->ref_processor();
376 rp->set_active_mt_degree(nworkers);
377
378 // enable ("weak") refs discovery
379 rp->enable_discovery(true /*verify_no_refs*/);
380 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
381 }
382
383 shenandoah_assert_rp_isalive_not_installed();
384 ShenandoahIsAliveSelector is_alive;
385 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
386
387 task_queues()->reserve(nworkers);
388
389 {
390 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
391 ShenandoahTaskTerminator terminator(nworkers, task_queues());
392 ShenandoahConcurrentMarkingTask task(this, &terminator);
393 workers->run_task(&task);
394 }
395
396 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
397 }
398
399 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
400 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
401
402 uint nworkers = _heap->workers()->active_workers();
403
404 // Finally mark everything else we've got in our queues during the previous steps.
405 // It does two different things for concurrent vs. mark-compact GC:
406 // - For concurrent GC, it starts with empty task queues, drains the remaining
407 // SATB buffers, and then completes the marking closure.
408 // - For mark-compact GC, it starts out with the task queues seeded by initial
409 // root scan, and completes the closure, thus marking through all live objects
410 // The implementation is the same, so it's shared here.
411 {
412 ShenandoahGCPhase phase(full_gc ?
413 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
414 ShenandoahPhaseTimings::finish_queues);
415 task_queues()->reserve(nworkers);
416
417 shenandoah_assert_rp_isalive_not_installed();
418 ShenandoahIsAliveSelector is_alive;
419 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
420
421 ShenandoahTerminationTracker termination_tracker(full_gc ?
422 ShenandoahPhaseTimings::full_gc_mark_termination :
423 ShenandoahPhaseTimings::termination);
424
425 StrongRootsScope scope(nworkers);
426 ShenandoahTaskTerminator terminator(nworkers, task_queues());
427 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
428 _heap->workers()->run_task(&task);
429 }
430
431 assert(task_queues()->is_empty(), "Should be empty");
432
433 // When we're done marking everything, we process weak references.
434 if (_heap->process_references()) {
435 weak_refs_work(full_gc);
436 }
437
438 _heap->parallel_cleaning(full_gc);
439
440 assert(task_queues()->is_empty(), "Should be empty");
441 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
442 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
443 }
444
445 // Weak Reference Closures
446 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
447 uint _worker_id;
448 ShenandoahTaskTerminator* _terminator;
449 bool _reset_terminator;
450
451 public:
452 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false):
453 _worker_id(worker_id),
454 _terminator(t),
455 _reset_terminator(reset_terminator) {
456 }
457
458 void do_void() {
459 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
460
461 ShenandoahHeap* sh = ShenandoahHeap::heap();
462 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
463 assert(sh->process_references(), "why else would we be here?");
464 ReferenceProcessor* rp = sh->ref_processor();
465
466 shenandoah_assert_rp_isalive_installed();
467
468 scm->mark_loop(_worker_id, _terminator, rp,
469 false, // not cancellable
470 false); // do not do strdedup
471
472 if (_reset_terminator) {
473 _terminator->reset_for_reuse();
474 }
475 }
476 };
477
478 class ShenandoahCMKeepAliveClosure : public OopClosure {
479 private:
480 ShenandoahObjToScanQueue* _queue;
481 ShenandoahHeap* _heap;
482 ShenandoahMarkingContext* const _mark_context;
483
484 template <class T>
485 inline void do_oop_work(T* p) {
486 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
487 }
488
489 public:
490 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
491 _queue(q),
492 _heap(ShenandoahHeap::heap()),
493 _mark_context(_heap->marking_context()) {}
494
495 void do_oop(narrowOop* p) { do_oop_work(p); }
496 void do_oop(oop* p) { do_oop_work(p); }
497 };
498
499 class ShenandoahCMKeepAliveUpdateClosure : 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, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
508 }
509
510 public:
511 ShenandoahCMKeepAliveUpdateClosure(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 ShenandoahWeakUpdateClosure : public OopClosure {
521 private:
522 ShenandoahHeap* const _heap;
523
524 template <class T>
525 inline void do_oop_work(T* p) {
526 oop o = _heap->maybe_update_with_forwarded(p);
527 shenandoah_assert_marked_except(p, o, o == NULL);
528 }
529
530 public:
531 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
532
533 void do_oop(narrowOop* p) { do_oop_work(p); }
534 void do_oop(oop* p) { do_oop_work(p); }
535 };
536
537 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
538 private:
539 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
540 ShenandoahTaskTerminator* _terminator;
541
542 public:
543 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
544 ShenandoahTaskTerminator* t) :
545 AbstractGangTask("Process reference objects in parallel"),
546 _proc_task(proc_task),
547 _terminator(t) {
548 }
549
550 void work(uint worker_id) {
551 ResourceMark rm;
552 HandleMark hm;
553 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
554 ShenandoahHeap* heap = ShenandoahHeap::heap();
555 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
556 if (heap->has_forwarded_objects()) {
557 ShenandoahForwardedIsAliveClosure is_alive;
558 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
559 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
560 } else {
561 ShenandoahIsAliveClosure is_alive;
562 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
563 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
564 }
565 }
566 };
567
568 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
569 private:
570 WorkGang* _workers;
571
572 public:
573 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
574 _workers(workers) {
575 }
576
577 // Executes a task using worker threads.
578 void execute(ProcessTask& task, uint ergo_workers) {
579 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
580
581 ShenandoahHeap* heap = ShenandoahHeap::heap();
582 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
583 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
584 ergo_workers,
585 /* do_check = */ false);
586 uint nworkers = _workers->active_workers();
587 cm->task_queues()->reserve(nworkers);
588 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
589 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
590 _workers->run_task(&proc_task_proxy);
591 }
592 };
593
594 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
595 assert(_heap->process_references(), "sanity");
596
597 ShenandoahPhaseTimings::Phase phase_root =
598 full_gc ?
599 ShenandoahPhaseTimings::full_gc_weakrefs :
600 ShenandoahPhaseTimings::weakrefs;
601
602 ShenandoahGCPhase phase(phase_root);
603
604 ReferenceProcessor* rp = _heap->ref_processor();
605
606 // NOTE: We cannot shortcut on has_discovered_references() here, because
607 // we will miss marking JNI Weak refs then, see implementation in
608 // ReferenceProcessor::process_discovered_references.
609 weak_refs_work_doit(full_gc);
610
611 rp->verify_no_references_recorded();
612 assert(!rp->discovery_enabled(), "Post condition");
613
614 }
615
616 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
617 ReferenceProcessor* rp = _heap->ref_processor();
618
619 ShenandoahPhaseTimings::Phase phase_process =
620 full_gc ?
621 ShenandoahPhaseTimings::full_gc_weakrefs_process :
622 ShenandoahPhaseTimings::weakrefs_process;
623
624 ShenandoahPhaseTimings::Phase phase_process_termination =
625 full_gc ?
626 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
627 ShenandoahPhaseTimings::weakrefs_termination;
628
629 shenandoah_assert_rp_isalive_not_installed();
630 ShenandoahIsAliveSelector is_alive;
631 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
632
633 WorkGang* workers = _heap->workers();
634 uint nworkers = workers->active_workers();
635
636 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
637 rp->set_active_mt_degree(nworkers);
638
639 assert(task_queues()->is_empty(), "Should be empty");
640
641 // complete_gc and keep_alive closures instantiated here are only needed for
642 // single-threaded path in RP. They share the queue 0 for tracking work, which
643 // simplifies implementation. Since RP may decide to call complete_gc several
644 // times, we need to be able to reuse the terminator.
645 uint serial_worker_id = 0;
646 ShenandoahTaskTerminator terminator(1, task_queues());
647 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
648
649 ShenandoahRefProcTaskExecutor executor(workers);
650
651 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
652
653 {
654 ShenandoahGCPhase phase(phase_process);
655 ShenandoahTerminationTracker phase_term(phase_process_termination);
656
657 if (_heap->has_forwarded_objects()) {
658 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
659 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
660 &complete_gc, &executor,
661 &pt);
662
663 } else {
664 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
665 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
666 &complete_gc, &executor,
667 &pt);
668
669 }
670
671 pt.print_all_references();
672
673 assert(task_queues()->is_empty(), "Should be empty");
674 }
675 }
676
677 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
678 private:
679 ShenandoahHeap* const _heap;
680 public:
681 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
682 virtual bool should_return() { return _heap->cancelled_gc(); }
683 };
684
685 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
686 public:
687 void do_void() {
688 ShenandoahHeap* sh = ShenandoahHeap::heap();
689 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
690 assert(sh->process_references(), "why else would we be here?");
691 ShenandoahTaskTerminator terminator(1, scm->task_queues());
692
693 ReferenceProcessor* rp = sh->ref_processor();
694 shenandoah_assert_rp_isalive_installed();
695
696 scm->mark_loop(0, &terminator, rp,
697 false, // not cancellable
698 false); // do not do strdedup
699 }
700 };
701
702 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
703 private:
704 ShenandoahObjToScanQueue* _queue;
705 ShenandoahHeap* _heap;
706 ShenandoahMarkingContext* const _mark_context;
707
708 template <class T>
709 inline void do_oop_work(T* p) {
710 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context);
711 }
712
713 public:
714 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
715 _queue(q),
716 _heap(ShenandoahHeap::heap()),
717 _mark_context(_heap->marking_context()) {}
718
719 void do_oop(narrowOop* p) { do_oop_work(p); }
720 void do_oop(oop* p) { do_oop_work(p); }
721 };
722
723 class ShenandoahPrecleanTask : public AbstractGangTask {
724 private:
725 ReferenceProcessor* _rp;
726
727 public:
728 ShenandoahPrecleanTask(ReferenceProcessor* rp) :
729 AbstractGangTask("Precleaning task"),
730 _rp(rp) {}
731
732 void work(uint worker_id) {
733 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
734 ShenandoahParallelWorkerSession worker_session(worker_id);
735
736 ShenandoahHeap* sh = ShenandoahHeap::heap();
737
738 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
739
740 ShenandoahCancelledGCYieldClosure yield;
741 ShenandoahPrecleanCompleteGCClosure complete_gc;
742
743 if (sh->has_forwarded_objects()) {
744 ShenandoahForwardedIsAliveClosure is_alive;
745 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q);
746 ResourceMark rm;
747 _rp->preclean_discovered_references(&is_alive, &keep_alive,
748 &complete_gc, &yield,
749 NULL);
750 } else {
751 ShenandoahIsAliveClosure is_alive;
752 ShenandoahCMKeepAliveClosure keep_alive(q);
753 ResourceMark rm;
754 _rp->preclean_discovered_references(&is_alive, &keep_alive,
755 &complete_gc, &yield,
756 NULL);
757 }
758 }
759 };
760
761 void ShenandoahConcurrentMark::preclean_weak_refs() {
762 // Pre-cleaning weak references before diving into STW makes sense at the
763 // end of concurrent mark. This will filter out the references which referents
764 // are alive. Note that ReferenceProcessor already filters out these on reference
765 // discovery, and the bulk of work is done here. This phase processes leftovers
766 // that missed the initial filtering, i.e. when referent was marked alive after
767 // reference was discovered by RP.
768
769 assert(_heap->process_references(), "sanity");
770
771 // Shortcut if no references were discovered to avoid winding up threads.
772 ReferenceProcessor* rp = _heap->ref_processor();
773 if (!rp->has_discovered_references()) {
774 return;
775 }
776
777 assert(task_queues()->is_empty(), "Should be empty");
778
779 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
780
781 shenandoah_assert_rp_isalive_not_installed();
782 ShenandoahIsAliveSelector is_alive;
783 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
784
785 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup
786 // queues and other goodies. When upstream ReferenceProcessor starts supporting
787 // parallel precleans, we can extend this to more threads.
788 WorkGang* workers = _heap->workers();
789 uint nworkers = workers->active_workers();
790 assert(nworkers == 1, "This code uses only a single worker");
791 task_queues()->reserve(nworkers);
792
793 ShenandoahPrecleanTask task(rp);
794 workers->run_task(&task);
795
796 assert(task_queues()->is_empty(), "Should be empty");
797 }
798
799 void ShenandoahConcurrentMark::cancel() {
800 // Clean up marking stacks.
801 ShenandoahObjToScanQueueSet* queues = task_queues();
802 queues->clear();
803
804 // Cancel SATB buffers.
805 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
806 }
807
808 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
809 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
810 return _task_queues->queue(worker_id);
811 }
812
813 template <bool CANCELLABLE>
814 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp,
815 bool strdedup) {
816 ShenandoahObjToScanQueue* q = get_queue(w);
817
818 jushort* ld = _heap->get_liveness_cache(w);
819
820 // TODO: We can clean up this if we figure out how to do templated oop closures that
821 // play nice with specialized_oop_iterators.
822 if (_heap->unload_classes()) {
823 if (_heap->has_forwarded_objects()) {
824 if (strdedup) {
825 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
826 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
827 } else {
828 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
829 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
830 }
831 } else {
832 if (strdedup) {
833 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
834 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
835 } else {
836 ShenandoahMarkRefsMetadataClosure cl(q, rp);
837 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
838 }
839 }
840 } else {
841 if (_heap->has_forwarded_objects()) {
842 if (strdedup) {
843 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
844 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
845 } else {
846 ShenandoahMarkUpdateRefsClosure cl(q, rp);
847 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
848 }
849 } else {
850 if (strdedup) {
851 ShenandoahMarkRefsDedupClosure cl(q, rp);
852 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
853 } else {
854 ShenandoahMarkRefsClosure cl(q, rp);
855 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
856 }
857 }
858 }
859
860 _heap->flush_liveness_cache(w);
861 }
862
863 template <class T, bool CANCELLABLE>
864 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) {
865 uintx stride = ShenandoahMarkLoopStride;
866
867 ShenandoahHeap* heap = ShenandoahHeap::heap();
868 ShenandoahObjToScanQueueSet* queues = task_queues();
869 ShenandoahObjToScanQueue* q;
870 ShenandoahMarkTask t;
871
872 /*
873 * Process outstanding queues, if any.
874 *
875 * There can be more queues than workers. To deal with the imbalance, we claim
876 * extra queues first. Since marking can push new tasks into the queue associated
877 * with this worker id, we come back to process this queue in the normal loop.
878 */
879 assert(queues->get_reserved() == heap->workers()->active_workers(),
880 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
881
882 q = queues->claim_next();
883 while (q != NULL) {
884 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
885 return;
886 }
887
888 for (uint i = 0; i < stride; i++) {
889 if (q->pop(t)) {
890 do_task<T>(q, cl, live_data, &t);
891 } else {
892 assert(q->is_empty(), "Must be empty");
893 q = queues->claim_next();
894 break;
895 }
896 }
897 }
898 q = get_queue(worker_id);
899
900 ShenandoahSATBBufferClosure drain_satb(q);
901 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
902
903 /*
904 * Normal marking loop:
905 */
906 while (true) {
907 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
908 return;
909 }
910
911 while (satb_mq_set.completed_buffers_num() > 0) {
912 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
913 }
914
915 uint work = 0;
916 for (uint i = 0; i < stride; i++) {
917 if (q->pop(t) ||
918 queues->steal(worker_id, t)) {
919 do_task<T>(q, cl, live_data, &t);
920 work++;
921 } else {
922 break;
923 }
924 }
925
926 if (work == 0) {
927 // No work encountered in current stride, try to terminate.
928 // Need to leave the STS here otherwise it might block safepoints.
929 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
930 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
931 ShenandoahTerminatorTerminator tt(heap);
932 if (terminator->offer_termination(&tt)) return;
933 }
934 }
935 }
936
937 bool ShenandoahConcurrentMark::claim_codecache() {
938 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
939 return _claimed_codecache.try_set();
940 }
941
942 void ShenandoahConcurrentMark::clear_claim_codecache() {
943 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
944 _claimed_codecache.unset();
945 }