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/shenandoahTaskqueue.inline.hpp"
45 #include "gc/shenandoah/shenandoahTimingTracker.hpp"
46 #include "gc/shenandoah/shenandoahUtils.hpp"
47
48 #include "memory/iterator.inline.hpp"
49 #include "memory/metaspace.hpp"
50 #include "memory/resourceArea.hpp"
51 #include "oops/oop.inline.hpp"
52 #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 bool _process_refs;
88 public:
89 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp, bool process_refs) :
90 AbstractGangTask("Shenandoah init mark roots task"),
91 _rp(rp),
92 _process_refs(process_refs) {
93 }
94
95 void work(uint worker_id) {
96 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
97 ShenandoahParallelWorkerSession worker_session(worker_id);
98
99 ShenandoahHeap* heap = ShenandoahHeap::heap();
100 ShenandoahObjToScanQueueSet* queues = heap->concurrent_mark()->task_queues();
101 assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id);
102
103 ShenandoahObjToScanQueue* q = queues->queue(worker_id);
104
105 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
106 do_work(heap, &mark_cl, worker_id);
107 }
108
109 private:
110 void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) {
111 // The rationale for selecting the roots to scan is as follows:
112 // a. With unload_classes = true, we only want to scan the actual strong roots from the
113 // code cache. This will allow us to identify the dead classes, unload them, *and*
114 // invalidate the relevant code cache blobs. This could be only done together with
115 // class unloading.
116 // b. With unload_classes = false, we have to nominally retain all the references from code
117 // cache, because there could be the case of embedded class/oop in the generated code,
118 // which we will never visit during mark. Without code cache invalidation, as in (a),
119 // we risk executing that code cache blob, and crashing.
120 if (heap->unload_classes()) {
121 _rp->strong_roots_do(worker_id, oops);
122 } else {
123 _rp->roots_do(worker_id, oops);
124 }
125 }
126 };
127
128 class ShenandoahUpdateRootsTask : public AbstractGangTask {
129 private:
130 ShenandoahRootUpdater* _root_updater;
131 bool _check_alive;
132 public:
133 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater, bool check_alive) :
134 AbstractGangTask("Shenandoah update roots task"),
135 _root_updater(root_updater),
136 _check_alive(check_alive){
137 }
138
139 void work(uint worker_id) {
140 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
141 ShenandoahParallelWorkerSession worker_session(worker_id);
142
143 ShenandoahHeap* heap = ShenandoahHeap::heap();
144 ShenandoahUpdateRefsClosure cl;
145 if (_check_alive) {
146 ShenandoahForwardedIsAliveClosure is_alive;
147 _root_updater->roots_do<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>(worker_id, &is_alive, &cl);
148 } else {
149 AlwaysTrueClosure always_true;;
150 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
151 }
152 }
153 };
154
155 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
156 private:
157 ShenandoahConcurrentMark* _cm;
158 TaskTerminator* _terminator;
159
160 public:
161 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
162 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) {
163 }
164
165 void work(uint worker_id) {
166 ShenandoahHeap* heap = ShenandoahHeap::heap();
167 ShenandoahConcurrentWorkerSession worker_session(worker_id);
168 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
169 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
170 ReferenceProcessor* rp;
171 if (heap->process_references()) {
172 rp = heap->ref_processor();
173 shenandoah_assert_rp_isalive_installed();
174 } else {
175 rp = NULL;
176 }
177
178 _cm->concurrent_scan_code_roots(worker_id, rp);
179 _cm->mark_loop(worker_id, _terminator, rp,
180 true, // cancellable
181 ShenandoahStringDedup::is_enabled()); // perform string dedup
182 }
183 };
184
185 class ShenandoahSATBThreadsClosure : public ThreadClosure {
186 private:
187 ShenandoahSATBBufferClosure* _satb_cl;
188 uintx _claim_token;
189
190 public:
191 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
192 _satb_cl(satb_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 }
199 }
200 };
201
202 class ShenandoahFinalMarkingTask : public AbstractGangTask {
203 private:
204 ShenandoahConcurrentMark* _cm;
205 TaskTerminator* _terminator;
206 bool _dedup_string;
207
208 public:
209 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
210 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
211 }
212
213 void work(uint worker_id) {
214 ShenandoahHeap* heap = ShenandoahHeap::heap();
215
216 ShenandoahParallelWorkerSession worker_session(worker_id);
217 // First drain remaining SATB buffers.
218 // Notice that this is not strictly necessary for mark-compact. But since
219 // it requires a StrongRootsScope around the task, we need to claim the
220 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
221 // full-gc.
222 {
223 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
224 ShenandoahSATBBufferClosure cl(q);
225 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
226 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
227 ShenandoahSATBThreadsClosure tc(&cl);
228 Threads::threads_do(&tc);
229 }
230
231 ReferenceProcessor* rp;
232 if (heap->process_references()) {
233 rp = heap->ref_processor();
234 shenandoah_assert_rp_isalive_installed();
235 } else {
236 rp = NULL;
237 }
238
239 if (heap->is_degenerated_gc_in_progress()) {
240 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
241 // let's check here.
242 _cm->concurrent_scan_code_roots(worker_id, rp);
243 }
244
245 _cm->mark_loop(worker_id, _terminator, rp,
246 false, // not cancellable
247 _dedup_string);
248
249 assert(_cm->task_queues()->is_empty(), "Should be empty");
250 }
251 };
252
253 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
254 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
255 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
256
257 ShenandoahHeap* heap = ShenandoahHeap::heap();
258
259 ShenandoahGCPhase phase(root_phase);
260
261 WorkGang* workers = heap->workers();
262 uint nworkers = workers->active_workers();
263
264 assert(nworkers <= task_queues()->size(), "Just check");
265
266 ShenandoahAllRootScanner root_proc(nworkers, root_phase);
267 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
268 task_queues()->reserve(nworkers);
269
270 if (heap->has_forwarded_objects()) {
271 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references());
272 workers->run_task(&mark_roots);
273 } else {
274 // No need to update references, which means the heap is stable.
275 // Can save time not walking through forwarding pointers.
276 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references());
277 workers->run_task(&mark_roots);
278 }
279
280 if (ShenandoahConcurrentScanCodeRoots) {
281 clear_claim_codecache();
282 }
283 }
284
285 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
286 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
287 assert(root_phase == ShenandoahPhaseTimings::full_gc_roots ||
288 root_phase == ShenandoahPhaseTimings::degen_gc_update_roots,
289 "Only for these phases");
290
291 ShenandoahGCPhase phase(root_phase);
292
293 bool check_alive = root_phase == ShenandoahPhaseTimings::degen_gc_update_roots;
294
295 #if COMPILER2_OR_JVMCI
296 DerivedPointerTable::clear();
297 #endif
298
299 uint nworkers = _heap->workers()->active_workers();
300
301 ShenandoahRootUpdater root_updater(nworkers, root_phase);
302 ShenandoahUpdateRootsTask update_roots(&root_updater, check_alive);
303 _heap->workers()->run_task(&update_roots);
304
305 #if COMPILER2_OR_JVMCI
306 DerivedPointerTable::update_pointers();
307 #endif
308 }
309
310 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask {
311 private:
312 ShenandoahThreadRoots _thread_roots;
313 ShenandoahPhaseTimings::Phase _phase;
314 public:
315 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) :
316 AbstractGangTask("Shenandoah Update Thread Roots"),
317 _thread_roots(is_par),
318 _phase(phase) {
319 ShenandoahHeap::heap()->phase_timings()->record_workers_start(_phase);
320 }
321
322 ~ShenandoahUpdateThreadRootsTask() {
323 ShenandoahHeap::heap()->phase_timings()->record_workers_end(_phase);
324 }
325 void work(uint worker_id) {
326 ShenandoahUpdateRefsClosure cl;
327 _thread_roots.oops_do(&cl, NULL, worker_id);
328 }
329 };
330
331 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) {
332 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
333
334 ShenandoahGCPhase phase(root_phase);
335
336 #if COMPILER2_OR_JVMCI
337 DerivedPointerTable::clear();
338 #endif
339
340 WorkGang* workers = _heap->workers();
341 bool is_par = workers->active_workers() > 1;
342
343 ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
344 workers->run_task(&task);
345
346 #if COMPILER2_OR_JVMCI
347 DerivedPointerTable::update_pointers();
348 #endif
349 }
350
351 void ShenandoahConcurrentMark::initialize(uint workers) {
352 _heap = ShenandoahHeap::heap();
353
354 uint num_queues = MAX2(workers, 1U);
355
356 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
357
358 for (uint i = 0; i < num_queues; ++i) {
359 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
360 task_queue->initialize();
361 _task_queues->register_queue(i, task_queue);
362 }
363 }
364
365 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
366 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
367 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
368 if (!_heap->unload_classes()) {
369 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
370 // TODO: We can not honor StringDeduplication here, due to lock ranking
371 // inversion. So, we may miss some deduplication candidates.
372 if (_heap->has_forwarded_objects()) {
373 ShenandoahMarkResolveRefsClosure cl(q, rp);
374 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
375 CodeCache::blobs_do(&blobs);
376 } else {
377 ShenandoahMarkRefsClosure cl(q, rp);
378 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
379 CodeCache::blobs_do(&blobs);
380 }
381 }
382 }
383 }
384
385 void ShenandoahConcurrentMark::mark_from_roots() {
386 WorkGang* workers = _heap->workers();
387 uint nworkers = workers->active_workers();
388
389 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
390
391 if (_heap->process_references()) {
392 ReferenceProcessor* rp = _heap->ref_processor();
393 rp->set_active_mt_degree(nworkers);
394
395 // enable ("weak") refs discovery
396 rp->enable_discovery(true /*verify_no_refs*/);
397 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
398 }
399
400 shenandoah_assert_rp_isalive_not_installed();
401 ShenandoahIsAliveSelector is_alive;
402 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
403
404 task_queues()->reserve(nworkers);
405
406 {
407 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
408 TaskTerminator terminator(nworkers, task_queues());
409 ShenandoahConcurrentMarkingTask task(this, &terminator);
410 workers->run_task(&task);
411 }
412
413 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
414 }
415
416 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
417 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
418
419 uint nworkers = _heap->workers()->active_workers();
420
421 // Finally mark everything else we've got in our queues during the previous steps.
422 // It does two different things for concurrent vs. mark-compact GC:
423 // - For concurrent GC, it starts with empty task queues, drains the remaining
424 // SATB buffers, and then completes the marking closure.
425 // - For mark-compact GC, it starts out with the task queues seeded by initial
426 // root scan, and completes the closure, thus marking through all live objects
427 // The implementation is the same, so it's shared here.
428 {
429 ShenandoahGCPhase phase(full_gc ?
430 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
431 ShenandoahPhaseTimings::finish_queues);
432 task_queues()->reserve(nworkers);
433
434 shenandoah_assert_rp_isalive_not_installed();
435 ShenandoahIsAliveSelector is_alive;
436 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
437
438 ShenandoahTerminationTracker termination_tracker(full_gc ?
439 ShenandoahPhaseTimings::full_gc_mark_termination :
440 ShenandoahPhaseTimings::termination);
441
442 StrongRootsScope scope(nworkers);
443 TaskTerminator terminator(nworkers, task_queues());
444 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
445 _heap->workers()->run_task(&task);
446 }
447
448 assert(task_queues()->is_empty(), "Should be empty");
449
450 // When we're done marking everything, we process weak references.
451 if (_heap->process_references()) {
452 weak_refs_work(full_gc);
453 }
454
455 assert(task_queues()->is_empty(), "Should be empty");
456 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
457 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
458 }
459
460 // Weak Reference Closures
461 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
462 uint _worker_id;
463 TaskTerminator* _terminator;
464 bool _reset_terminator;
465
466 public:
467 ShenandoahCMDrainMarkingStackClosure(uint worker_id, TaskTerminator* t, bool reset_terminator = false):
468 _worker_id(worker_id),
469 _terminator(t),
470 _reset_terminator(reset_terminator) {
471 }
472
473 void do_void() {
474 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
475
476 ShenandoahHeap* sh = ShenandoahHeap::heap();
477 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
478 assert(sh->process_references(), "why else would we be here?");
479 ReferenceProcessor* rp = sh->ref_processor();
480
481 shenandoah_assert_rp_isalive_installed();
482
483 scm->mark_loop(_worker_id, _terminator, rp,
484 false, // not cancellable
485 false); // do not do strdedup
486
487 if (_reset_terminator) {
488 _terminator->reset_for_reuse();
489 }
490 }
491 };
492
493 class ShenandoahCMKeepAliveClosure : public OopClosure {
494 private:
495 ShenandoahObjToScanQueue* _queue;
496 ShenandoahHeap* _heap;
497 ShenandoahMarkingContext* const _mark_context;
498
499 template <class T>
500 inline void do_oop_work(T* p) {
501 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
502 }
503
504 public:
505 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
506 _queue(q),
507 _heap(ShenandoahHeap::heap()),
508 _mark_context(_heap->marking_context()) {}
509
510 void do_oop(narrowOop* p) { do_oop_work(p); }
511 void do_oop(oop* p) { do_oop_work(p); }
512 };
513
514 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
515 private:
516 ShenandoahObjToScanQueue* _queue;
517 ShenandoahHeap* _heap;
518 ShenandoahMarkingContext* const _mark_context;
519
520 template <class T>
521 inline void do_oop_work(T* p) {
522 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
523 }
524
525 public:
526 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
527 _queue(q),
528 _heap(ShenandoahHeap::heap()),
529 _mark_context(_heap->marking_context()) {}
530
531 void do_oop(narrowOop* p) { do_oop_work(p); }
532 void do_oop(oop* p) { do_oop_work(p); }
533 };
534
535 class ShenandoahWeakUpdateClosure : public OopClosure {
536 private:
537 ShenandoahHeap* const _heap;
538
539 template <class T>
540 inline void do_oop_work(T* p) {
541 oop o = _heap->maybe_update_with_forwarded(p);
542 shenandoah_assert_marked_except(p, o, o == NULL);
543 }
544
545 public:
546 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
547
548 void do_oop(narrowOop* p) { do_oop_work(p); }
549 void do_oop(oop* p) { do_oop_work(p); }
550 };
551
552 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
553 private:
554 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
555 TaskTerminator* _terminator;
556
557 public:
558 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
559 TaskTerminator* t) :
560 AbstractGangTask("Process reference objects in parallel"),
561 _proc_task(proc_task),
562 _terminator(t) {
563 }
564
565 void work(uint worker_id) {
566 ResourceMark rm;
567 HandleMark hm;
568 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
569 ShenandoahHeap* heap = ShenandoahHeap::heap();
570 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
571 if (heap->has_forwarded_objects()) {
572 ShenandoahForwardedIsAliveClosure is_alive;
573 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
574 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
575 } else {
576 ShenandoahIsAliveClosure is_alive;
577 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
578 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
579 }
580 }
581 };
582
583 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
584 private:
585 WorkGang* _workers;
586
587 public:
588 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
589 _workers(workers) {
590 }
591
592 // Executes a task using worker threads.
593 void execute(ProcessTask& task, uint ergo_workers) {
594 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
595
596 ShenandoahHeap* heap = ShenandoahHeap::heap();
597 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
598 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
599 ergo_workers,
600 /* do_check = */ false);
601 uint nworkers = _workers->active_workers();
602 cm->task_queues()->reserve(nworkers);
603 TaskTerminator terminator(nworkers, cm->task_queues());
604 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
605 _workers->run_task(&proc_task_proxy);
606 }
607 };
608
609 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
610 assert(_heap->process_references(), "sanity");
611
612 ShenandoahPhaseTimings::Phase phase_root =
613 full_gc ?
614 ShenandoahPhaseTimings::full_gc_weakrefs :
615 ShenandoahPhaseTimings::weakrefs;
616
617 ShenandoahGCPhase phase(phase_root);
618
619 ReferenceProcessor* rp = _heap->ref_processor();
620
621 // NOTE: We cannot shortcut on has_discovered_references() here, because
622 // we will miss marking JNI Weak refs then, see implementation in
623 // ReferenceProcessor::process_discovered_references.
624 weak_refs_work_doit(full_gc);
625
626 rp->verify_no_references_recorded();
627 assert(!rp->discovery_enabled(), "Post condition");
628
629 }
630
631 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
632 ReferenceProcessor* rp = _heap->ref_processor();
633
634 ShenandoahPhaseTimings::Phase phase_process =
635 full_gc ?
636 ShenandoahPhaseTimings::full_gc_weakrefs_process :
637 ShenandoahPhaseTimings::weakrefs_process;
638
639 ShenandoahPhaseTimings::Phase phase_process_termination =
640 full_gc ?
641 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
642 ShenandoahPhaseTimings::weakrefs_termination;
643
644 shenandoah_assert_rp_isalive_not_installed();
645 ShenandoahIsAliveSelector is_alive;
646 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
647
648 WorkGang* workers = _heap->workers();
649 uint nworkers = workers->active_workers();
650
651 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
652 rp->set_active_mt_degree(nworkers);
653
654 assert(task_queues()->is_empty(), "Should be empty");
655
656 // complete_gc and keep_alive closures instantiated here are only needed for
657 // single-threaded path in RP. They share the queue 0 for tracking work, which
658 // simplifies implementation. Since RP may decide to call complete_gc several
659 // times, we need to be able to reuse the terminator.
660 uint serial_worker_id = 0;
661 TaskTerminator terminator(1, task_queues());
662 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
663
664 ShenandoahRefProcTaskExecutor executor(workers);
665
666 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
667
668 {
669 ShenandoahGCPhase phase(phase_process);
670 ShenandoahTerminationTracker phase_term(phase_process_termination);
671
672 if (_heap->has_forwarded_objects()) {
673 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
674 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
675 &complete_gc, &executor,
676 &pt);
677
678 } else {
679 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
680 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
681 &complete_gc, &executor,
682 &pt);
683
684 }
685
686 pt.print_all_references();
687
688 assert(task_queues()->is_empty(), "Should be empty");
689 }
690 }
691
692 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
693 private:
694 ShenandoahHeap* const _heap;
695 public:
696 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
697 virtual bool should_return() { return _heap->cancelled_gc(); }
698 };
699
700 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
701 public:
702 void do_void() {
703 ShenandoahHeap* sh = ShenandoahHeap::heap();
704 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
705 assert(sh->process_references(), "why else would we be here?");
706 TaskTerminator terminator(1, scm->task_queues());
707
708 ReferenceProcessor* rp = sh->ref_processor();
709 shenandoah_assert_rp_isalive_installed();
710
711 scm->mark_loop(0, &terminator, rp,
712 false, // not cancellable
713 false); // do not do strdedup
714 }
715 };
716
717 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
718 private:
719 ShenandoahObjToScanQueue* _queue;
720 ShenandoahHeap* _heap;
721 ShenandoahMarkingContext* const _mark_context;
722
723 template <class T>
724 inline void do_oop_work(T* p) {
725 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context);
726 }
727
728 public:
729 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
730 _queue(q),
731 _heap(ShenandoahHeap::heap()),
732 _mark_context(_heap->marking_context()) {}
733
734 void do_oop(narrowOop* p) { do_oop_work(p); }
735 void do_oop(oop* p) { do_oop_work(p); }
736 };
737
738 class ShenandoahPrecleanTask : public AbstractGangTask {
739 private:
740 ReferenceProcessor* _rp;
741
742 public:
743 ShenandoahPrecleanTask(ReferenceProcessor* rp) :
744 AbstractGangTask("Precleaning task"),
745 _rp(rp) {}
746
747 void work(uint worker_id) {
748 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
749 ShenandoahParallelWorkerSession worker_session(worker_id);
750
751 ShenandoahHeap* sh = ShenandoahHeap::heap();
752
753 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
754
755 ShenandoahCancelledGCYieldClosure yield;
756 ShenandoahPrecleanCompleteGCClosure complete_gc;
757
758 if (sh->has_forwarded_objects()) {
759 ShenandoahForwardedIsAliveClosure is_alive;
760 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q);
761 ResourceMark rm;
762 _rp->preclean_discovered_references(&is_alive, &keep_alive,
763 &complete_gc, &yield,
764 NULL);
765 } else {
766 ShenandoahIsAliveClosure is_alive;
767 ShenandoahCMKeepAliveClosure keep_alive(q);
768 ResourceMark rm;
769 _rp->preclean_discovered_references(&is_alive, &keep_alive,
770 &complete_gc, &yield,
771 NULL);
772 }
773 }
774 };
775
776 void ShenandoahConcurrentMark::preclean_weak_refs() {
777 // Pre-cleaning weak references before diving into STW makes sense at the
778 // end of concurrent mark. This will filter out the references which referents
779 // are alive. Note that ReferenceProcessor already filters out these on reference
780 // discovery, and the bulk of work is done here. This phase processes leftovers
781 // that missed the initial filtering, i.e. when referent was marked alive after
782 // reference was discovered by RP.
783
784 assert(_heap->process_references(), "sanity");
785
786 // Shortcut if no references were discovered to avoid winding up threads.
787 ReferenceProcessor* rp = _heap->ref_processor();
788 if (!rp->has_discovered_references()) {
789 return;
790 }
791
792 assert(task_queues()->is_empty(), "Should be empty");
793
794 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
795
796 shenandoah_assert_rp_isalive_not_installed();
797 ShenandoahIsAliveSelector is_alive;
798 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
799
800 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup
801 // queues and other goodies. When upstream ReferenceProcessor starts supporting
802 // parallel precleans, we can extend this to more threads.
803 WorkGang* workers = _heap->workers();
804 uint nworkers = workers->active_workers();
805 assert(nworkers == 1, "This code uses only a single worker");
806 task_queues()->reserve(nworkers);
807
808 ShenandoahPrecleanTask task(rp);
809 workers->run_task(&task);
810
811 assert(task_queues()->is_empty(), "Should be empty");
812 }
813
814 void ShenandoahConcurrentMark::cancel() {
815 // Clean up marking stacks.
816 ShenandoahObjToScanQueueSet* queues = task_queues();
817 queues->clear();
818
819 // Cancel SATB buffers.
820 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
821 }
822
823 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
824 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
825 return _task_queues->queue(worker_id);
826 }
827
828 template <bool CANCELLABLE>
829 void ShenandoahConcurrentMark::mark_loop_prework(uint w, TaskTerminator *t, ReferenceProcessor *rp,
830 bool strdedup) {
831 ShenandoahObjToScanQueue* q = get_queue(w);
832
833 jushort* ld = _heap->get_liveness_cache(w);
834
835 // TODO: We can clean up this if we figure out how to do templated oop closures that
836 // play nice with specialized_oop_iterators.
837 if (_heap->unload_classes()) {
838 if (_heap->has_forwarded_objects()) {
839 if (strdedup) {
840 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
841 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
842 } else {
843 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
844 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
845 }
846 } else {
847 if (strdedup) {
848 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
849 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
850 } else {
851 ShenandoahMarkRefsMetadataClosure cl(q, rp);
852 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
853 }
854 }
855 } else {
856 if (_heap->has_forwarded_objects()) {
857 if (strdedup) {
858 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
859 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
860 } else {
861 ShenandoahMarkUpdateRefsClosure cl(q, rp);
862 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
863 }
864 } else {
865 if (strdedup) {
866 ShenandoahMarkRefsDedupClosure cl(q, rp);
867 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
868 } else {
869 ShenandoahMarkRefsClosure cl(q, rp);
870 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
871 }
872 }
873 }
874
875 _heap->flush_liveness_cache(w);
876 }
877
878 template <class T, bool CANCELLABLE>
879 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, TaskTerminator *terminator) {
880 uintx stride = ShenandoahMarkLoopStride;
881
882 ShenandoahHeap* heap = ShenandoahHeap::heap();
883 ShenandoahObjToScanQueueSet* queues = task_queues();
884 ShenandoahObjToScanQueue* q;
885 ShenandoahMarkTask t;
886
887 /*
888 * Process outstanding queues, if any.
889 *
890 * There can be more queues than workers. To deal with the imbalance, we claim
891 * extra queues first. Since marking can push new tasks into the queue associated
892 * with this worker id, we come back to process this queue in the normal loop.
893 */
894 assert(queues->get_reserved() == heap->workers()->active_workers(),
895 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
896
897 q = queues->claim_next();
898 while (q != NULL) {
899 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
900 return;
901 }
902
903 for (uint i = 0; i < stride; i++) {
904 if (q->pop(t)) {
905 do_task<T>(q, cl, live_data, &t);
906 } else {
907 assert(q->is_empty(), "Must be empty");
908 q = queues->claim_next();
909 break;
910 }
911 }
912 }
913 q = get_queue(worker_id);
914
915 ShenandoahSATBBufferClosure drain_satb(q);
916 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
917
918 /*
919 * Normal marking loop:
920 */
921 while (true) {
922 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
923 return;
924 }
925
926 while (satb_mq_set.completed_buffers_num() > 0) {
927 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
928 }
929
930 uint work = 0;
931 for (uint i = 0; i < stride; i++) {
932 if (q->pop(t) ||
933 queues->steal(worker_id, t)) {
934 do_task<T>(q, cl, live_data, &t);
935 work++;
936 } else {
937 break;
938 }
939 }
940
941 if (work == 0) {
942 // No work encountered in current stride, try to terminate.
943 // Need to leave the STS here otherwise it might block safepoints.
944 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
945 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
946 ShenandoahTerminatorTerminator tt(heap);
947 if (terminator->offer_termination(&tt)) return;
948 }
949 }
950 }
951
952 bool ShenandoahConcurrentMark::claim_codecache() {
953 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
954 return _claimed_codecache.try_set();
955 }
956
957 void ShenandoahConcurrentMark::clear_claim_codecache() {
958 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
959 _claimed_codecache.unset();
960 }