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