1 /*
2 * Copyright (c) 2013, 2020, Red Hat, Inc. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30
31 #include "gc/shared/weakProcessor.inline.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/referenceProcessor.hpp"
34 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
35 #include "gc/shared/strongRootsScope.hpp"
36
37 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
38 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
39 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
40 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
41 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
42 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
43 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
44 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
45 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
46 #include "gc/shenandoah/shenandoahUtils.hpp"
47
48 #include "memory/iterator.inline.hpp"
49 #include "memory/metaspace.hpp"
50 #include "memory/resourceArea.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "runtime/handles.inline.hpp"
53
54 template<UpdateRefsMode UPDATE_REFS>
55 class ShenandoahInitMarkRootsClosure : public OopClosure {
56 private:
57 ShenandoahObjToScanQueue* _queue;
58 ShenandoahHeap* _heap;
59 ShenandoahMarkingContext* const _mark_context;
60
61 template <class T>
62 inline void do_oop_work(T* p) {
63 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, NO_DEDUP>(p, _heap, _queue, _mark_context);
64 }
65
66 public:
67 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) :
68 _queue(q),
69 _heap(ShenandoahHeap::heap()),
70 _mark_context(_heap->marking_context()) {};
71
72 void do_oop(narrowOop* p) { do_oop_work(p); }
73 void do_oop(oop* p) { do_oop_work(p); }
74 };
75
76 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) :
77 MetadataVisitingOopIterateClosure(rp),
78 _queue(q),
79 _heap(ShenandoahHeap::heap()),
80 _mark_context(_heap->marking_context())
81 { }
82
83 template<UpdateRefsMode UPDATE_REFS>
84 class ShenandoahInitMarkRootsTask : public AbstractGangTask {
85 private:
86 ShenandoahAllRootScanner* _rp;
87 public:
88 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp) :
89 AbstractGangTask("Shenandoah init mark roots task"),
90 _rp(rp) {
91 }
92
93 void work(uint worker_id) {
94 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
95 ShenandoahParallelWorkerSession worker_session(worker_id);
96
97 ShenandoahHeap* heap = ShenandoahHeap::heap();
98 ShenandoahObjToScanQueueSet* queues = heap->concurrent_mark()->task_queues();
99 assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id);
100
101 ShenandoahObjToScanQueue* q = queues->queue(worker_id);
102
103 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
104 do_work(heap, &mark_cl, worker_id);
105 }
106
107 private:
108 void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) {
109 // The rationale for selecting the roots to scan is as follows:
110 // a. With unload_classes = true, we only want to scan the actual strong roots from the
111 // code cache. This will allow us to identify the dead classes, unload them, *and*
112 // invalidate the relevant code cache blobs. This could be only done together with
113 // class unloading.
114 // b. With unload_classes = false, we have to nominally retain all the references from code
115 // cache, because there could be the case of embedded class/oop in the generated code,
116 // which we will never visit during mark. Without code cache invalidation, as in (a),
117 // we risk executing that code cache blob, and crashing.
118 if (heap->unload_classes()) {
119 _rp->strong_roots_do(worker_id, oops);
120 } else {
121 _rp->roots_do(worker_id, oops);
122 }
123 }
124 };
125
126 class ShenandoahUpdateRootsTask : public AbstractGangTask {
127 private:
128 ShenandoahRootUpdater* _root_updater;
129 bool _check_alive;
130 public:
131 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater, bool check_alive) :
132 AbstractGangTask("Shenandoah update roots task"),
133 _root_updater(root_updater),
134 _check_alive(check_alive){
135 }
136
137 void work(uint worker_id) {
138 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
139 ShenandoahParallelWorkerSession worker_session(worker_id);
140
141 ShenandoahHeap* heap = ShenandoahHeap::heap();
142 ShenandoahUpdateRefsClosure cl;
143 if (_check_alive) {
144 ShenandoahForwardedIsAliveClosure is_alive;
145 _root_updater->roots_do<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>(worker_id, &is_alive, &cl);
146 } else {
147 AlwaysTrueClosure always_true;;
148 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
149 }
150 }
151 };
152
153 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
154 private:
155 ShenandoahConcurrentMark* _cm;
156 TaskTerminator* _terminator;
157
158 public:
159 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
160 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) {
161 }
162
163 void work(uint worker_id) {
164 ShenandoahHeap* heap = ShenandoahHeap::heap();
165 ShenandoahConcurrentWorkerSession worker_session(worker_id);
166 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
167 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
168 ReferenceProcessor* rp;
169 if (heap->process_references()) {
170 rp = heap->ref_processor();
171 shenandoah_assert_rp_isalive_installed();
172 } else {
173 rp = NULL;
174 }
175
176 _cm->concurrent_scan_code_roots(worker_id, rp);
177 _cm->mark_loop(worker_id, _terminator, rp,
178 true, // cancellable
179 ShenandoahStringDedup::is_enabled()); // perform string dedup
180 }
181 };
182
183 class ShenandoahSATBAndRemarkCodeRootsThreadsClosure : public ThreadClosure {
184 private:
185 ShenandoahSATBBufferClosure* const _satb_cl;
186 OopClosure* const _cl;
187 MarkingCodeBlobClosure* const _code_cl;
188 uintx _claim_token;
189 public:
190 ShenandoahSATBAndRemarkCodeRootsThreadsClosure(ShenandoahSATBBufferClosure* satb_cl,
191 OopClosure* cl, MarkingCodeBlobClosure* code_cl) :
192 _satb_cl(satb_cl), _cl(cl), _code_cl(code_cl),
193 _claim_token(Threads::thread_claim_token()) {}
194
195 void do_thread(Thread* thread) {
196 if (thread->claim_threads_do(true, _claim_token)) {
197 ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl);
198 if (_cl != NULL) {
199 // This doesn't appear to add very much to final-mark latency. If that ever becomes a problem,
200 // we can attempt to trim it to only scan actual thread-stacks (and avoid stuff like handles, monitors, etc)
201 // and there only compiled frames. We can also make thread-scans templatized to avoid virtual calls and
202 // instead inline the closures.
203 ResourceMark rm;
204 thread->oops_do(_cl, _code_cl);
205 } else if (_code_cl != NULL && thread->is_Java_thread()) {
206 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
207 // however the liveness of oops reachable from nmethods have very complex lifecycles:
208 // * Alive if on the stack of an executing method
209 // * Weakly reachable otherwise
210 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
211 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
212 JavaThread* jt = (JavaThread*)thread;
213 jt->nmethods_do(_code_cl);
214 }
215 }
216 }
217 };
218
219 class ShenandoahFinalMarkingTask : public AbstractGangTask {
220 private:
221 ShenandoahConcurrentMark* _cm;
222 TaskTerminator* _terminator;
223 bool _dedup_string;
224
225 public:
226 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
227 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
228 }
229
230 void work(uint worker_id) {
231 ShenandoahHeap* heap = ShenandoahHeap::heap();
232
233 ShenandoahParallelWorkerSession worker_session(worker_id);
234 ReferenceProcessor* rp;
235 if (heap->process_references()) {
236 rp = heap->ref_processor();
237 shenandoah_assert_rp_isalive_installed();
238 } else {
239 rp = NULL;
240 }
241
242 // First drain remaining SATB buffers.
243 // Notice that this is not strictly necessary for mark-compact. But since
244 // it requires a StrongRootsScope around the task, we need to claim the
245 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
246 // full-gc.
247 {
248 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
249
250 ShenandoahSATBBufferClosure cl(q);
251 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
252 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
253
254 bool do_nmethods = heap->unload_classes() && !ShenandoahConcurrentRoots::can_do_concurrent_class_unloading();
255 if (heap->has_forwarded_objects()) {
256 ShenandoahMarkResolveRefsClosure resolve_mark_cl(q, rp);
257 MarkingCodeBlobClosure blobsCl(&resolve_mark_cl, !CodeBlobToOopClosure::FixRelocations);
258 ShenandoahSATBAndRemarkCodeRootsThreadsClosure tc(&cl,
259 ShenandoahAggressiveReferenceDiscovery ? &resolve_mark_cl : NULL,
260 do_nmethods ? &blobsCl : NULL);
261 Threads::threads_do(&tc);
262 } else {
263 ShenandoahMarkRefsClosure mark_cl(q, rp);
264 MarkingCodeBlobClosure blobsCl(&mark_cl, !CodeBlobToOopClosure::FixRelocations);
265 ShenandoahSATBAndRemarkCodeRootsThreadsClosure tc(&cl,
266 ShenandoahAggressiveReferenceDiscovery ? &mark_cl : NULL,
267 do_nmethods ? &blobsCl : NULL);
268 Threads::threads_do(&tc);
269 }
270 }
271
272 if (heap->is_degenerated_gc_in_progress()) {
273 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
274 // let's check here.
275 _cm->concurrent_scan_code_roots(worker_id, rp);
276 }
277
278 _cm->mark_loop(worker_id, _terminator, rp,
279 false, // not cancellable
280 _dedup_string);
281
282 assert(_cm->task_queues()->is_empty(), "Should be empty");
283 }
284 };
285
286 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
287 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
288 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
289
290 ShenandoahHeap* heap = ShenandoahHeap::heap();
291
292 ShenandoahGCPhase phase(root_phase);
293
294 WorkGang* workers = heap->workers();
295 uint nworkers = workers->active_workers();
296
297 assert(nworkers <= task_queues()->size(), "Just check");
298
299 ShenandoahAllRootScanner root_proc(nworkers, root_phase);
300 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
301 task_queues()->reserve(nworkers);
302
303 if (heap->has_forwarded_objects()) {
304 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc);
305 workers->run_task(&mark_roots);
306 } else {
307 // No need to update references, which means the heap is stable.
308 // Can save time not walking through forwarding pointers.
309 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc);
310 workers->run_task(&mark_roots);
311 }
312
313 if (ShenandoahConcurrentScanCodeRoots) {
314 clear_claim_codecache();
315 }
316 }
317
318 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
319 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
320 assert(root_phase == ShenandoahPhaseTimings::full_gc_roots ||
321 root_phase == ShenandoahPhaseTimings::degen_gc_update_roots,
322 "Only for these phases");
323
324 ShenandoahGCPhase phase(root_phase);
325
326 bool check_alive = root_phase == ShenandoahPhaseTimings::degen_gc_update_roots;
327
328 #if COMPILER2_OR_JVMCI
329 DerivedPointerTable::clear();
330 #endif
331
332 uint nworkers = _heap->workers()->active_workers();
333
334 ShenandoahRootUpdater root_updater(nworkers, root_phase);
335 ShenandoahUpdateRootsTask update_roots(&root_updater, check_alive);
336 _heap->workers()->run_task(&update_roots);
337
338 #if COMPILER2_OR_JVMCI
339 DerivedPointerTable::update_pointers();
340 #endif
341 }
342
343 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask {
344 private:
345 ShenandoahThreadRoots _thread_roots;
346 ShenandoahPhaseTimings::Phase _phase;
347 ShenandoahGCWorkerPhase _worker_phase;
348 public:
349 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) :
350 AbstractGangTask("Shenandoah Update Thread Roots"),
351 _thread_roots(is_par),
352 _phase(phase),
353 _worker_phase(phase) {}
354
355 void work(uint worker_id) {
356 ShenandoahUpdateRefsClosure cl;
357 _thread_roots.oops_do(&cl, NULL, worker_id);
358 }
359 };
360
361 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) {
362 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
363
364 ShenandoahGCPhase phase(root_phase);
365
366 #if COMPILER2_OR_JVMCI
367 DerivedPointerTable::clear();
368 #endif
369
370 WorkGang* workers = _heap->workers();
371 bool is_par = workers->active_workers() > 1;
372
373 ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
374 workers->run_task(&task);
375
376 #if COMPILER2_OR_JVMCI
377 DerivedPointerTable::update_pointers();
378 #endif
379 }
380
381 void ShenandoahConcurrentMark::initialize(uint workers) {
382 _heap = ShenandoahHeap::heap();
383
384 uint num_queues = MAX2(workers, 1U);
385
386 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
387
388 for (uint i = 0; i < num_queues; ++i) {
389 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
390 task_queue->initialize();
391 _task_queues->register_queue(i, task_queue);
392 }
393 }
394
395 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
396 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
397 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
398 if (!_heap->unload_classes()) {
399 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
400 // TODO: We can not honor StringDeduplication here, due to lock ranking
401 // inversion. So, we may miss some deduplication candidates.
402 if (_heap->has_forwarded_objects()) {
403 ShenandoahMarkResolveRefsClosure cl(q, rp);
404 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
405 CodeCache::blobs_do(&blobs);
406 } else {
407 ShenandoahMarkRefsClosure cl(q, rp);
408 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
409 CodeCache::blobs_do(&blobs);
410 }
411 }
412 }
413 }
414
415 void ShenandoahConcurrentMark::mark_from_roots() {
416 WorkGang* workers = _heap->workers();
417 uint nworkers = workers->active_workers();
418
419 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
420
421 if (_heap->process_references()) {
422 ReferenceProcessor* rp = _heap->ref_processor();
423 rp->set_active_mt_degree(nworkers);
424
425 // enable ("weak") refs discovery
426 rp->enable_discovery(true /*verify_no_refs*/);
427 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
428 }
429
430 shenandoah_assert_rp_isalive_not_installed();
431 ShenandoahIsAliveSelector is_alive;
432 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
433
434 task_queues()->reserve(nworkers);
435
436 {
437 TaskTerminator terminator(nworkers, task_queues());
438 ShenandoahConcurrentMarkingTask task(this, &terminator);
439 workers->run_task(&task);
440 }
441
442 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
443 }
444
445 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
446 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
447
448 uint nworkers = _heap->workers()->active_workers();
449
450 // Finally mark everything else we've got in our queues during the previous steps.
451 // It does two different things for concurrent vs. mark-compact GC:
452 // - For concurrent GC, it starts with empty task queues, drains the remaining
453 // SATB buffers, and then completes the marking closure.
454 // - For mark-compact GC, it starts out with the task queues seeded by initial
455 // root scan, and completes the closure, thus marking through all live objects
456 // The implementation is the same, so it's shared here.
457 {
458 ShenandoahGCPhase phase(full_gc ?
459 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
460 ShenandoahPhaseTimings::finish_queues);
461 task_queues()->reserve(nworkers);
462
463 shenandoah_assert_rp_isalive_not_installed();
464 ShenandoahIsAliveSelector is_alive;
465 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
466
467 StrongRootsScope scope(nworkers);
468 TaskTerminator terminator(nworkers, task_queues());
469 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
470 _heap->workers()->run_task(&task);
471 }
472
473 assert(task_queues()->is_empty(), "Should be empty");
474
475 // When we're done marking everything, we process weak references.
476 if (_heap->process_references()) {
477 weak_refs_work(full_gc);
478 }
479
480 assert(task_queues()->is_empty(), "Should be empty");
481 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
482 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
483 }
484
485 // Weak Reference Closures
486 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
487 uint _worker_id;
488 TaskTerminator* _terminator;
489 bool _reset_terminator;
490
491 public:
492 ShenandoahCMDrainMarkingStackClosure(uint worker_id, TaskTerminator* t, bool reset_terminator = false):
493 _worker_id(worker_id),
494 _terminator(t),
495 _reset_terminator(reset_terminator) {
496 }
497
498 void do_void() {
499 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
500
501 ShenandoahHeap* sh = ShenandoahHeap::heap();
502 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
503 assert(sh->process_references(), "why else would we be here?");
504 ReferenceProcessor* rp = sh->ref_processor();
505
506 shenandoah_assert_rp_isalive_installed();
507
508 scm->mark_loop(_worker_id, _terminator, rp,
509 false, // not cancellable
510 false); // do not do strdedup
511
512 if (_reset_terminator) {
513 _terminator->reset_for_reuse();
514 }
515 }
516 };
517
518 class ShenandoahCMKeepAliveClosure : public OopClosure {
519 private:
520 ShenandoahObjToScanQueue* _queue;
521 ShenandoahHeap* _heap;
522 ShenandoahMarkingContext* const _mark_context;
523
524 template <class T>
525 inline void do_oop_work(T* p) {
526 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
527 }
528
529 public:
530 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
531 _queue(q),
532 _heap(ShenandoahHeap::heap()),
533 _mark_context(_heap->marking_context()) {}
534
535 void do_oop(narrowOop* p) { do_oop_work(p); }
536 void do_oop(oop* p) { do_oop_work(p); }
537 };
538
539 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
540 private:
541 ShenandoahObjToScanQueue* _queue;
542 ShenandoahHeap* _heap;
543 ShenandoahMarkingContext* const _mark_context;
544
545 template <class T>
546 inline void do_oop_work(T* p) {
547 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
548 }
549
550 public:
551 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
552 _queue(q),
553 _heap(ShenandoahHeap::heap()),
554 _mark_context(_heap->marking_context()) {}
555
556 void do_oop(narrowOop* p) { do_oop_work(p); }
557 void do_oop(oop* p) { do_oop_work(p); }
558 };
559
560 class ShenandoahWeakUpdateClosure : public OopClosure {
561 private:
562 ShenandoahHeap* const _heap;
563
564 template <class T>
565 inline void do_oop_work(T* p) {
566 oop o = _heap->maybe_update_with_forwarded(p);
567 shenandoah_assert_marked_except(p, o, o == NULL);
568 }
569
570 public:
571 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
572
573 void do_oop(narrowOop* p) { do_oop_work(p); }
574 void do_oop(oop* p) { do_oop_work(p); }
575 };
576
577 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
578 private:
579 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
580 TaskTerminator* _terminator;
581
582 public:
583 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
584 TaskTerminator* t) :
585 AbstractGangTask("Process reference objects in parallel"),
586 _proc_task(proc_task),
587 _terminator(t) {
588 }
589
590 void work(uint worker_id) {
591 ResourceMark rm;
592 HandleMark hm;
593 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
594 ShenandoahHeap* heap = ShenandoahHeap::heap();
595 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
596 if (heap->has_forwarded_objects()) {
597 ShenandoahForwardedIsAliveClosure is_alive;
598 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
599 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
600 } else {
601 ShenandoahIsAliveClosure is_alive;
602 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
603 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
604 }
605 }
606 };
607
608 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
609 private:
610 WorkGang* _workers;
611
612 public:
613 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
614 _workers(workers) {
615 }
616
617 // Executes a task using worker threads.
618 void execute(ProcessTask& task, uint ergo_workers) {
619 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
620
621 ShenandoahHeap* heap = ShenandoahHeap::heap();
622 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
623 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
624 ergo_workers,
625 /* do_check = */ false);
626 uint nworkers = _workers->active_workers();
627 cm->task_queues()->reserve(nworkers);
628 TaskTerminator terminator(nworkers, cm->task_queues());
629 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
630 _workers->run_task(&proc_task_proxy);
631 }
632 };
633
634 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
635 assert(_heap->process_references(), "sanity");
636
637 ShenandoahPhaseTimings::Phase phase_root =
638 full_gc ?
639 ShenandoahPhaseTimings::full_gc_weakrefs :
640 ShenandoahPhaseTimings::weakrefs;
641
642 ShenandoahGCPhase phase(phase_root);
643
644 ReferenceProcessor* rp = _heap->ref_processor();
645
646 // NOTE: We cannot shortcut on has_discovered_references() here, because
647 // we will miss marking JNI Weak refs then, see implementation in
648 // ReferenceProcessor::process_discovered_references.
649 weak_refs_work_doit(full_gc);
650
651 rp->verify_no_references_recorded();
652 assert(!rp->discovery_enabled(), "Post condition");
653
654 }
655
656 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
657 ReferenceProcessor* rp = _heap->ref_processor();
658
659 ShenandoahPhaseTimings::Phase phase_process =
660 full_gc ?
661 ShenandoahPhaseTimings::full_gc_weakrefs_process :
662 ShenandoahPhaseTimings::weakrefs_process;
663
664 shenandoah_assert_rp_isalive_not_installed();
665 ShenandoahIsAliveSelector is_alive;
666 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
667
668 WorkGang* workers = _heap->workers();
669 uint nworkers = workers->active_workers();
670
671 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
672 rp->set_active_mt_degree(nworkers);
673
674 assert(task_queues()->is_empty(), "Should be empty");
675
676 // complete_gc and keep_alive closures instantiated here are only needed for
677 // single-threaded path in RP. They share the queue 0 for tracking work, which
678 // simplifies implementation. Since RP may decide to call complete_gc several
679 // times, we need to be able to reuse the terminator.
680 uint serial_worker_id = 0;
681 TaskTerminator terminator(1, task_queues());
682 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
683
684 ShenandoahRefProcTaskExecutor executor(workers);
685
686 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
687
688 {
689 ShenandoahGCPhase phase(phase_process);
690
691 if (_heap->has_forwarded_objects()) {
692 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
693 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
694 &complete_gc, &executor,
695 &pt);
696
697 } else {
698 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
699 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
700 &complete_gc, &executor,
701 &pt);
702
703 }
704
705 pt.print_all_references();
706
707 assert(task_queues()->is_empty(), "Should be empty");
708 }
709 }
710
711 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
712 private:
713 ShenandoahHeap* const _heap;
714 public:
715 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
716 virtual bool should_return() { return _heap->cancelled_gc(); }
717 };
718
719 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
720 public:
721 void do_void() {
722 ShenandoahHeap* sh = ShenandoahHeap::heap();
723 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
724 assert(sh->process_references(), "why else would we be here?");
725 TaskTerminator terminator(1, scm->task_queues());
726
727 ReferenceProcessor* rp = sh->ref_processor();
728 shenandoah_assert_rp_isalive_installed();
729
730 scm->mark_loop(0, &terminator, rp,
731 false, // not cancellable
732 false); // do not do strdedup
733 }
734 };
735
736 class ShenandoahPrecleanTask : public AbstractGangTask {
737 private:
738 ReferenceProcessor* _rp;
739
740 public:
741 ShenandoahPrecleanTask(ReferenceProcessor* rp) :
742 AbstractGangTask("Precleaning task"),
743 _rp(rp) {}
744
745 void work(uint worker_id) {
746 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
747 ShenandoahParallelWorkerSession worker_session(worker_id);
748
749 ShenandoahHeap* sh = ShenandoahHeap::heap();
750 assert(!sh->has_forwarded_objects(), "No forwarded objects expected here");
751
752 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
753
754 ShenandoahCancelledGCYieldClosure yield;
755 ShenandoahPrecleanCompleteGCClosure complete_gc;
756
757 ShenandoahIsAliveClosure is_alive;
758 ShenandoahCMKeepAliveClosure keep_alive(q);
759 ResourceMark rm;
760 _rp->preclean_discovered_references(&is_alive, &keep_alive,
761 &complete_gc, &yield,
762 NULL);
763 }
764 };
765
766 void ShenandoahConcurrentMark::preclean_weak_refs() {
767 // Pre-cleaning weak references before diving into STW makes sense at the
768 // end of concurrent mark. This will filter out the references which referents
769 // are alive. Note that ReferenceProcessor already filters out these on reference
770 // discovery, and the bulk of work is done here. This phase processes leftovers
771 // that missed the initial filtering, i.e. when referent was marked alive after
772 // reference was discovered by RP.
773
774 assert(_heap->process_references(), "sanity");
775
776 // Shortcut if no references were discovered to avoid winding up threads.
777 ReferenceProcessor* rp = _heap->ref_processor();
778 if (!rp->has_discovered_references()) {
779 return;
780 }
781
782 assert(task_queues()->is_empty(), "Should be empty");
783
784 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
785
786 shenandoah_assert_rp_isalive_not_installed();
787 ShenandoahIsAliveSelector is_alive;
788 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
789
790 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup
791 // queues and other goodies. When upstream ReferenceProcessor starts supporting
792 // parallel precleans, we can extend this to more threads.
793 WorkGang* workers = _heap->workers();
794 uint nworkers = workers->active_workers();
795 assert(nworkers == 1, "This code uses only a single worker");
796 task_queues()->reserve(nworkers);
797
798 ShenandoahPrecleanTask task(rp);
799 workers->run_task(&task);
800
801 assert(task_queues()->is_empty(), "Should be empty");
802 }
803
804 void ShenandoahConcurrentMark::cancel() {
805 // Clean up marking stacks.
806 ShenandoahObjToScanQueueSet* queues = task_queues();
807 queues->clear();
808
809 // Cancel SATB buffers.
810 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
811 }
812
813 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
814 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
815 return _task_queues->queue(worker_id);
816 }
817
818 template <bool CANCELLABLE>
819 void ShenandoahConcurrentMark::mark_loop_prework(uint w, TaskTerminator *t, ReferenceProcessor *rp,
820 bool strdedup) {
821 ShenandoahObjToScanQueue* q = get_queue(w);
822
823 jushort* ld = _heap->get_liveness_cache(w);
824
825 // TODO: We can clean up this if we figure out how to do templated oop closures that
826 // play nice with specialized_oop_iterators.
827 if (_heap->unload_classes()) {
828 if (_heap->has_forwarded_objects()) {
829 if (strdedup) {
830 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
831 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
832 } else {
833 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
834 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
835 }
836 } else {
837 if (strdedup) {
838 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
839 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
840 } else {
841 ShenandoahMarkRefsMetadataClosure cl(q, rp);
842 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
843 }
844 }
845 } else {
846 if (_heap->has_forwarded_objects()) {
847 if (strdedup) {
848 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
849 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
850 } else {
851 ShenandoahMarkUpdateRefsClosure cl(q, rp);
852 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
853 }
854 } else {
855 if (strdedup) {
856 ShenandoahMarkRefsDedupClosure cl(q, rp);
857 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
858 } else {
859 ShenandoahMarkRefsClosure cl(q, rp);
860 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
861 }
862 }
863 }
864
865 _heap->flush_liveness_cache(w);
866 }
867
868 template <class T, bool CANCELLABLE>
869 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, TaskTerminator *terminator) {
870 uintx stride = ShenandoahMarkLoopStride;
871
872 ShenandoahHeap* heap = ShenandoahHeap::heap();
873 ShenandoahObjToScanQueueSet* queues = task_queues();
874 ShenandoahObjToScanQueue* q;
875 ShenandoahMarkTask t;
876
877 /*
878 * Process outstanding queues, if any.
879 *
880 * There can be more queues than workers. To deal with the imbalance, we claim
881 * extra queues first. Since marking can push new tasks into the queue associated
882 * with this worker id, we come back to process this queue in the normal loop.
883 */
884 assert(queues->get_reserved() == heap->workers()->active_workers(),
885 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
886
887 q = queues->claim_next();
888 while (q != NULL) {
889 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
890 return;
891 }
892
893 for (uint i = 0; i < stride; i++) {
894 if (q->pop(t)) {
895 do_task<T>(q, cl, live_data, &t);
896 } else {
897 assert(q->is_empty(), "Must be empty");
898 q = queues->claim_next();
899 break;
900 }
901 }
902 }
903 q = get_queue(worker_id);
904
905 ShenandoahSATBBufferClosure drain_satb(q);
906 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
907
908 /*
909 * Normal marking loop:
910 */
911 while (true) {
912 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
913 return;
914 }
915
916 while (satb_mq_set.completed_buffers_num() > 0) {
917 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
918 }
919
920 uint work = 0;
921 for (uint i = 0; i < stride; i++) {
922 if (q->pop(t) ||
923 queues->steal(worker_id, t)) {
924 do_task<T>(q, cl, live_data, &t);
925 work++;
926 } else {
927 break;
928 }
929 }
930
931 if (work == 0) {
932 // No work encountered in current stride, try to terminate.
933 // Need to leave the STS here otherwise it might block safepoints.
934 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
935 ShenandoahTerminatorTerminator tt(heap);
936 if (terminator->offer_termination(&tt)) return;
937 }
938 }
939 }
940
941 bool ShenandoahConcurrentMark::claim_codecache() {
942 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
943 return _claimed_codecache.try_set();
944 }
945
946 void ShenandoahConcurrentMark::clear_claim_codecache() {
947 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
948 _claimed_codecache.unset();
949 }