1 /*
2 * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29
30 #include "gc/shared/weakProcessor.inline.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/referenceProcessor.hpp"
33 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
34
35 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
36 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
37 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
38 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
39 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
40 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
41 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
42 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
43 #include "gc/shenandoah/shenandoahTimingTracker.hpp"
44 #include "gc/shenandoah/shenandoahUtils.hpp"
45
46 #include "memory/iterator.inline.hpp"
47 #include "memory/metaspace.hpp"
48 #include "memory/resourceArea.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "runtime/handles.inline.hpp"
51
52 template<UpdateRefsMode UPDATE_REFS>
53 class ShenandoahInitMarkRootsClosure : public OopClosure {
54 private:
55 ShenandoahObjToScanQueue* _queue;
56 ShenandoahHeap* _heap;
57 ShenandoahMarkingContext* const _mark_context;
58
59 template <class T>
60 inline void do_oop_work(T* p) {
61 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, NO_DEDUP>(p, _heap, _queue, _mark_context);
62 }
63
64 public:
65 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) :
66 _queue(q),
67 _heap(ShenandoahHeap::heap()),
68 _mark_context(_heap->marking_context()) {};
69
70 void do_oop(narrowOop* p) { do_oop_work(p); }
71 void do_oop(oop* p) { do_oop_work(p); }
72 };
73
74 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) :
75 MetadataVisitingOopIterateClosure(rp),
76 _queue(q),
77 _heap(ShenandoahHeap::heap()),
78 _mark_context(_heap->marking_context())
79 { }
80
81 template<UpdateRefsMode UPDATE_REFS>
82 class ShenandoahInitMarkRootsTask : public AbstractGangTask {
83 private:
84 ShenandoahAllRootScanner* _rp;
85 bool _process_refs;
86 public:
87 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp, bool process_refs) :
88 AbstractGangTask("Shenandoah init mark roots task"),
89 _rp(rp),
90 _process_refs(process_refs) {
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 public:
130 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater) :
131 AbstractGangTask("Shenandoah update roots task"),
132 _root_updater(root_updater) {
133 }
134
135 void work(uint worker_id) {
136 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
137 ShenandoahParallelWorkerSession worker_session(worker_id);
138
139 ShenandoahHeap* heap = ShenandoahHeap::heap();
140 ShenandoahUpdateRefsClosure cl;
141 AlwaysTrueClosure always_true;
142 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
143 }
144 };
145
146 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
147 private:
148 ShenandoahConcurrentMark* _cm;
149 ShenandoahTaskTerminator* _terminator;
150
151 public:
152 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator) :
153 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) {
154 }
155
156 void work(uint worker_id) {
157 ShenandoahHeap* heap = ShenandoahHeap::heap();
158 ShenandoahConcurrentWorkerSession worker_session(worker_id);
159 ShenandoahSuspendibleThreadSetJoiner stsj;
160 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
161 ReferenceProcessor* rp;
162 if (heap->process_references()) {
163 rp = heap->ref_processor();
164 shenandoah_assert_rp_isalive_installed();
165 } else {
166 rp = NULL;
167 }
168
169 _cm->concurrent_scan_code_roots(worker_id, rp);
170 _cm->mark_loop(worker_id, _terminator, rp,
171 true, // cancellable
172 ShenandoahStringDedup::is_enabled()); // perform string dedup
173 }
174 };
175
176 class ShenandoahSATBThreadsClosure : public ThreadClosure {
177 private:
178 ShenandoahSATBBufferClosure* _satb_cl;
179 uintx _claim_token;
180
181 public:
182 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
183 _satb_cl(satb_cl),
184 _claim_token(Threads::thread_claim_token()) {}
185
186 void do_thread(Thread* thread) {
187 if (thread->claim_threads_do(true, _claim_token)) {
188 ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl);
189 }
190 }
191 };
192
193 class ShenandoahFinalMarkingTask : public AbstractGangTask {
194 private:
195 ShenandoahConcurrentMark* _cm;
196 ShenandoahTaskTerminator* _terminator;
197 bool _dedup_string;
198
199 public:
200 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) :
201 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
202 }
203
204 void work(uint worker_id) {
205 ShenandoahHeap* heap = ShenandoahHeap::heap();
206
207 ShenandoahParallelWorkerSession worker_session(worker_id);
208 // First drain remaining SATB buffers.
209 // Notice that this is not strictly necessary for mark-compact. But since
210 // it requires a StrongRootsScope around the task, we need to claim the
211 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
212 // full-gc.
213 {
214 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
215 ShenandoahSATBBufferClosure cl(q);
216 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
217 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
218 ShenandoahSATBThreadsClosure tc(&cl);
219 Threads::threads_do(&tc);
220 }
221
222 ReferenceProcessor* rp;
223 if (heap->process_references()) {
224 rp = heap->ref_processor();
225 shenandoah_assert_rp_isalive_installed();
226 } else {
227 rp = NULL;
228 }
229
230 if (heap->is_degenerated_gc_in_progress()) {
231 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
232 // let's check here.
233 _cm->concurrent_scan_code_roots(worker_id, rp);
234 }
235
236 _cm->mark_loop(worker_id, _terminator, rp,
237 false, // not cancellable
238 _dedup_string);
239
240 assert(_cm->task_queues()->is_empty(), "Should be empty");
241 }
242 };
243
244 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
245 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
246 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
247
248 ShenandoahHeap* heap = ShenandoahHeap::heap();
249
250 ShenandoahGCPhase phase(root_phase);
251
252 WorkGang* workers = heap->workers();
253 uint nworkers = workers->active_workers();
254
255 assert(nworkers <= task_queues()->size(), "Just check");
256
257 ShenandoahAllRootScanner root_proc(nworkers, root_phase);
258 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
259 task_queues()->reserve(nworkers);
260
261 if (heap->has_forwarded_objects()) {
262 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references());
263 workers->run_task(&mark_roots);
264 } else {
265 // No need to update references, which means the heap is stable.
266 // Can save time not walking through forwarding pointers.
267 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references());
268 workers->run_task(&mark_roots);
269 }
270
271 if (ShenandoahConcurrentScanCodeRoots) {
272 clear_claim_codecache();
273 }
274 }
275
276 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
277 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
278
279 bool update_code_cache = true; // initialize to safer value
280 switch (root_phase) {
281 case ShenandoahPhaseTimings::update_roots:
282 case ShenandoahPhaseTimings::final_update_refs_roots:
283 update_code_cache = false;
284 break;
285 case ShenandoahPhaseTimings::full_gc_roots:
286 case ShenandoahPhaseTimings::degen_gc_update_roots:
287 update_code_cache = true;
288 break;
289 default:
290 ShouldNotReachHere();
291 }
292
293 ShenandoahGCPhase phase(root_phase);
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, update_code_cache);
302 ShenandoahUpdateRootsTask update_roots(&root_updater);
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 WorkGang* workers = _heap->workers();
333 bool is_par = workers->active_workers() > 1;
334 #if COMPILER2_OR_JVMCI
335 DerivedPointerTable::clear();
336 #endif
337 ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
338 workers->run_task(&task);
339 #if COMPILER2_OR_JVMCI
340 DerivedPointerTable::update_pointers();
341 #endif
342 }
343
344 void ShenandoahConcurrentMark::initialize(uint workers) {
345 _heap = ShenandoahHeap::heap();
346
347 uint num_queues = MAX2(workers, 1U);
348
349 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
350
351 for (uint i = 0; i < num_queues; ++i) {
352 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
353 task_queue->initialize();
354 _task_queues->register_queue(i, task_queue);
355 }
356 }
357
358 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
359 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
360 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
361 if (!_heap->unload_classes()) {
362 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
363 // TODO: We can not honor StringDeduplication here, due to lock ranking
364 // inversion. So, we may miss some deduplication candidates.
365 if (_heap->has_forwarded_objects()) {
366 ShenandoahMarkResolveRefsClosure cl(q, rp);
367 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
368 CodeCache::blobs_do(&blobs);
369 } else {
370 ShenandoahMarkRefsClosure cl(q, rp);
371 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
372 CodeCache::blobs_do(&blobs);
373 }
374 }
375 }
376 }
377
378 void ShenandoahConcurrentMark::mark_from_roots() {
379 WorkGang* workers = _heap->workers();
380 uint nworkers = workers->active_workers();
381
382 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
383
384 if (_heap->process_references()) {
385 ReferenceProcessor* rp = _heap->ref_processor();
386 rp->set_active_mt_degree(nworkers);
387
388 // enable ("weak") refs discovery
389 rp->enable_discovery(true /*verify_no_refs*/);
390 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
391 }
392
393 shenandoah_assert_rp_isalive_not_installed();
394 ShenandoahIsAliveSelector is_alive;
395 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
396
397 task_queues()->reserve(nworkers);
398
399 {
400 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
401 ShenandoahTaskTerminator terminator(nworkers, task_queues());
402 ShenandoahConcurrentMarkingTask task(this, &terminator);
403 workers->run_task(&task);
404 }
405
406 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
407 }
408
409 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
410 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
411
412 uint nworkers = _heap->workers()->active_workers();
413
414 // Finally mark everything else we've got in our queues during the previous steps.
415 // It does two different things for concurrent vs. mark-compact GC:
416 // - For concurrent GC, it starts with empty task queues, drains the remaining
417 // SATB buffers, and then completes the marking closure.
418 // - For mark-compact GC, it starts out with the task queues seeded by initial
419 // root scan, and completes the closure, thus marking through all live objects
420 // The implementation is the same, so it's shared here.
421 {
422 ShenandoahGCPhase phase(full_gc ?
423 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
424 ShenandoahPhaseTimings::finish_queues);
425 task_queues()->reserve(nworkers);
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 ShenandoahTerminationTracker termination_tracker(full_gc ?
432 ShenandoahPhaseTimings::full_gc_mark_termination :
433 ShenandoahPhaseTimings::termination);
434
435 StrongRootsScope scope(nworkers);
436 ShenandoahTaskTerminator terminator(nworkers, task_queues());
437 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
438 _heap->workers()->run_task(&task);
439 }
440
441 assert(task_queues()->is_empty(), "Should be empty");
442
443 // When we're done marking everything, we process weak references.
444 if (_heap->process_references()) {
445 weak_refs_work(full_gc);
446 }
447
448 weak_roots_work();
449
450 // And finally finish class unloading
451 if (_heap->unload_classes()) {
452 _heap->unload_classes_and_cleanup_tables(full_gc);
453 } else if (ShenandoahStringDedup::is_enabled()) {
454 ShenandoahIsAliveSelector alive;
455 BoolObjectClosure* is_alive = alive.is_alive_closure();
456 ShenandoahStringDedup::unlink_or_oops_do(is_alive, NULL, false);
457 }
458 assert(task_queues()->is_empty(), "Should be empty");
459 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
460 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
461
462 // Resize Metaspace
463 MetaspaceGC::compute_new_size();
464 }
465
466 // Weak Reference Closures
467 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
468 uint _worker_id;
469 ShenandoahTaskTerminator* _terminator;
470 bool _reset_terminator;
471
472 public:
473 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false):
474 _worker_id(worker_id),
475 _terminator(t),
476 _reset_terminator(reset_terminator) {
477 }
478
479 void do_void() {
480 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
481
482 ShenandoahHeap* sh = ShenandoahHeap::heap();
483 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
484 assert(sh->process_references(), "why else would we be here?");
485 ReferenceProcessor* rp = sh->ref_processor();
486
487 shenandoah_assert_rp_isalive_installed();
488
489 scm->mark_loop(_worker_id, _terminator, rp,
490 false, // not cancellable
491 false); // do not do strdedup
492
493 if (_reset_terminator) {
494 _terminator->reset_for_reuse();
495 }
496 }
497 };
498
499 class ShenandoahCMKeepAliveClosure : public OopClosure {
500 private:
501 ShenandoahObjToScanQueue* _queue;
502 ShenandoahHeap* _heap;
503 ShenandoahMarkingContext* const _mark_context;
504
505 template <class T>
506 inline void do_oop_work(T* p) {
507 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
508 }
509
510 public:
511 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
512 _queue(q),
513 _heap(ShenandoahHeap::heap()),
514 _mark_context(_heap->marking_context()) {}
515
516 void do_oop(narrowOop* p) { do_oop_work(p); }
517 void do_oop(oop* p) { do_oop_work(p); }
518 };
519
520 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
521 private:
522 ShenandoahObjToScanQueue* _queue;
523 ShenandoahHeap* _heap;
524 ShenandoahMarkingContext* const _mark_context;
525
526 template <class T>
527 inline void do_oop_work(T* p) {
528 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
529 }
530
531 public:
532 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
533 _queue(q),
534 _heap(ShenandoahHeap::heap()),
535 _mark_context(_heap->marking_context()) {}
536
537 void do_oop(narrowOop* p) { do_oop_work(p); }
538 void do_oop(oop* p) { do_oop_work(p); }
539 };
540
541 class ShenandoahWeakUpdateClosure : public OopClosure {
542 private:
543 ShenandoahHeap* const _heap;
544
545 template <class T>
546 inline void do_oop_work(T* p) {
547 oop o = _heap->maybe_update_with_forwarded(p);
548 shenandoah_assert_marked_except(p, o, o == NULL);
549 }
550
551 public:
552 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
553
554 void do_oop(narrowOop* p) { do_oop_work(p); }
555 void do_oop(oop* p) { do_oop_work(p); }
556 };
557
558 class ShenandoahWeakAssertNotForwardedClosure : public OopClosure {
559 private:
560 template <class T>
561 inline void do_oop_work(T* p) {
562 #ifdef ASSERT
563 T o = RawAccess<>::oop_load(p);
564 if (!CompressedOops::is_null(o)) {
565 oop obj = CompressedOops::decode_not_null(o);
566 shenandoah_assert_not_forwarded(p, obj);
567 }
568 #endif
569 }
570
571 public:
572 ShenandoahWeakAssertNotForwardedClosure() {}
573
574 void do_oop(narrowOop* p) { do_oop_work(p); }
575 void do_oop(oop* p) { do_oop_work(p); }
576 };
577
578 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
579 private:
580 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
581 ShenandoahTaskTerminator* _terminator;
582
583 public:
584 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
585 ShenandoahTaskTerminator* t) :
586 AbstractGangTask("Process reference objects in parallel"),
587 _proc_task(proc_task),
588 _terminator(t) {
589 }
590
591 void work(uint worker_id) {
592 ResourceMark rm;
593 HandleMark hm;
594 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
595 ShenandoahHeap* heap = ShenandoahHeap::heap();
596 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
597 if (heap->has_forwarded_objects()) {
598 ShenandoahForwardedIsAliveClosure is_alive;
599 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
600 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
601 } else {
602 ShenandoahIsAliveClosure is_alive;
603 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
604 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
605 }
606 }
607 };
608
609 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
610 private:
611 WorkGang* _workers;
612
613 public:
614 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
615 _workers(workers) {
616 }
617
618 // Executes a task using worker threads.
619 void execute(ProcessTask& task, uint ergo_workers) {
620 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
621
622 ShenandoahHeap* heap = ShenandoahHeap::heap();
623 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
624 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
625 ergo_workers,
626 /* do_check = */ false);
627 uint nworkers = _workers->active_workers();
628 cm->task_queues()->reserve(nworkers);
629 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
630 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
631 _workers->run_task(&proc_task_proxy);
632 }
633 };
634
635 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
636 assert(_heap->process_references(), "sanity");
637
638 ShenandoahPhaseTimings::Phase phase_root =
639 full_gc ?
640 ShenandoahPhaseTimings::full_gc_weakrefs :
641 ShenandoahPhaseTimings::weakrefs;
642
643 ShenandoahGCPhase phase(phase_root);
644
645 ReferenceProcessor* rp = _heap->ref_processor();
646
647 // NOTE: We cannot shortcut on has_discovered_references() here, because
648 // we will miss marking JNI Weak refs then, see implementation in
649 // ReferenceProcessor::process_discovered_references.
650 weak_refs_work_doit(full_gc);
651
652 rp->verify_no_references_recorded();
653 assert(!rp->discovery_enabled(), "Post condition");
654
655 }
656
657 // Process leftover weak oops: update them, if needed or assert they do not
658 // need updating otherwise.
659 // Weak processor API requires us to visit the oops, even if we are not doing
660 // anything to them.
661 void ShenandoahConcurrentMark::weak_roots_work() {
662 WorkGang* workers = _heap->workers();
663 OopClosure* keep_alive = &do_nothing_cl;
664 #ifdef ASSERT
665 ShenandoahWeakAssertNotForwardedClosure verify_cl;
666 keep_alive = &verify_cl;
667 #endif
668 ShenandoahIsAliveClosure is_alive;
669 WeakProcessor::weak_oops_do(workers, &is_alive, keep_alive, 1);
670 }
671
672 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
673 ReferenceProcessor* rp = _heap->ref_processor();
674
675 ShenandoahPhaseTimings::Phase phase_process =
676 full_gc ?
677 ShenandoahPhaseTimings::full_gc_weakrefs_process :
678 ShenandoahPhaseTimings::weakrefs_process;
679
680 ShenandoahPhaseTimings::Phase phase_process_termination =
681 full_gc ?
682 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
683 ShenandoahPhaseTimings::weakrefs_termination;
684
685 shenandoah_assert_rp_isalive_not_installed();
686 ShenandoahIsAliveSelector is_alive;
687 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
688
689 WorkGang* workers = _heap->workers();
690 uint nworkers = workers->active_workers();
691
692 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
693 rp->set_active_mt_degree(nworkers);
694
695 assert(task_queues()->is_empty(), "Should be empty");
696
697 // complete_gc and keep_alive closures instantiated here are only needed for
698 // single-threaded path in RP. They share the queue 0 for tracking work, which
699 // simplifies implementation. Since RP may decide to call complete_gc several
700 // times, we need to be able to reuse the terminator.
701 uint serial_worker_id = 0;
702 ShenandoahTaskTerminator terminator(1, task_queues());
703 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
704
705 ShenandoahRefProcTaskExecutor executor(workers);
706
707 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
708
709 {
710 ShenandoahGCPhase phase(phase_process);
711 ShenandoahTerminationTracker phase_term(phase_process_termination);
712
713 if (_heap->has_forwarded_objects()) {
714 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
715 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
716 &complete_gc, &executor,
717 &pt);
718
719 } else {
720 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
721 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
722 &complete_gc, &executor,
723 &pt);
724
725 }
726
727 pt.print_all_references();
728
729 assert(task_queues()->is_empty(), "Should be empty");
730 }
731 }
732
733 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
734 private:
735 ShenandoahHeap* const _heap;
736 public:
737 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
738 virtual bool should_return() { return _heap->cancelled_gc(); }
739 };
740
741 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
742 public:
743 void do_void() {
744 ShenandoahHeap* sh = ShenandoahHeap::heap();
745 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
746 assert(sh->process_references(), "why else would we be here?");
747 ShenandoahTaskTerminator terminator(1, scm->task_queues());
748
749 ReferenceProcessor* rp = sh->ref_processor();
750 shenandoah_assert_rp_isalive_installed();
751
752 scm->mark_loop(0, &terminator, rp,
753 false, // not cancellable
754 false); // do not do strdedup
755 }
756 };
757
758 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
759 private:
760 ShenandoahObjToScanQueue* _queue;
761 ShenandoahHeap* _heap;
762 ShenandoahMarkingContext* const _mark_context;
763
764 template <class T>
765 inline void do_oop_work(T* p) {
766 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context);
767 }
768
769 public:
770 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
771 _queue(q),
772 _heap(ShenandoahHeap::heap()),
773 _mark_context(_heap->marking_context()) {}
774
775 void do_oop(narrowOop* p) { do_oop_work(p); }
776 void do_oop(oop* p) { do_oop_work(p); }
777 };
778
779 class ShenandoahPrecleanTask : public AbstractGangTask {
780 private:
781 ReferenceProcessor* _rp;
782
783 public:
784 ShenandoahPrecleanTask(ReferenceProcessor* rp) :
785 AbstractGangTask("Precleaning task"),
786 _rp(rp) {}
787
788 void work(uint worker_id) {
789 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
790 ShenandoahParallelWorkerSession worker_session(worker_id);
791
792 ShenandoahHeap* sh = ShenandoahHeap::heap();
793
794 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
795
796 ShenandoahCancelledGCYieldClosure yield;
797 ShenandoahPrecleanCompleteGCClosure complete_gc;
798
799 if (sh->has_forwarded_objects()) {
800 ShenandoahForwardedIsAliveClosure is_alive;
801 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q);
802 ResourceMark rm;
803 _rp->preclean_discovered_references(&is_alive, &keep_alive,
804 &complete_gc, &yield,
805 NULL);
806 } else {
807 ShenandoahIsAliveClosure is_alive;
808 ShenandoahCMKeepAliveClosure keep_alive(q);
809 ResourceMark rm;
810 _rp->preclean_discovered_references(&is_alive, &keep_alive,
811 &complete_gc, &yield,
812 NULL);
813 }
814 }
815 };
816
817 void ShenandoahConcurrentMark::preclean_weak_refs() {
818 // Pre-cleaning weak references before diving into STW makes sense at the
819 // end of concurrent mark. This will filter out the references which referents
820 // are alive. Note that ReferenceProcessor already filters out these on reference
821 // discovery, and the bulk of work is done here. This phase processes leftovers
822 // that missed the initial filtering, i.e. when referent was marked alive after
823 // reference was discovered by RP.
824
825 assert(_heap->process_references(), "sanity");
826
827 // Shortcut if no references were discovered to avoid winding up threads.
828 ReferenceProcessor* rp = _heap->ref_processor();
829 if (!rp->has_discovered_references()) {
830 return;
831 }
832
833 assert(task_queues()->is_empty(), "Should be empty");
834
835 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
836
837 shenandoah_assert_rp_isalive_not_installed();
838 ShenandoahIsAliveSelector is_alive;
839 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
840
841 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup
842 // queues and other goodies. When upstream ReferenceProcessor starts supporting
843 // parallel precleans, we can extend this to more threads.
844 WorkGang* workers = _heap->workers();
845 uint nworkers = workers->active_workers();
846 assert(nworkers == 1, "This code uses only a single worker");
847 task_queues()->reserve(nworkers);
848
849 ShenandoahPrecleanTask task(rp);
850 workers->run_task(&task);
851
852 assert(task_queues()->is_empty(), "Should be empty");
853 }
854
855 void ShenandoahConcurrentMark::cancel() {
856 // Clean up marking stacks.
857 ShenandoahObjToScanQueueSet* queues = task_queues();
858 queues->clear();
859
860 // Cancel SATB buffers.
861 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
862 }
863
864 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
865 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
866 return _task_queues->queue(worker_id);
867 }
868
869 template <bool CANCELLABLE>
870 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp,
871 bool strdedup) {
872 ShenandoahObjToScanQueue* q = get_queue(w);
873
874 jushort* ld = _heap->get_liveness_cache(w);
875
876 // TODO: We can clean up this if we figure out how to do templated oop closures that
877 // play nice with specialized_oop_iterators.
878 if (_heap->unload_classes()) {
879 if (_heap->has_forwarded_objects()) {
880 if (strdedup) {
881 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
882 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
883 } else {
884 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
885 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
886 }
887 } else {
888 if (strdedup) {
889 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
890 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
891 } else {
892 ShenandoahMarkRefsMetadataClosure cl(q, rp);
893 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
894 }
895 }
896 } else {
897 if (_heap->has_forwarded_objects()) {
898 if (strdedup) {
899 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
900 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
901 } else {
902 ShenandoahMarkUpdateRefsClosure cl(q, rp);
903 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
904 }
905 } else {
906 if (strdedup) {
907 ShenandoahMarkRefsDedupClosure cl(q, rp);
908 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
909 } else {
910 ShenandoahMarkRefsClosure cl(q, rp);
911 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
912 }
913 }
914 }
915
916 _heap->flush_liveness_cache(w);
917 }
918
919 template <class T, bool CANCELLABLE>
920 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) {
921 uintx stride = ShenandoahMarkLoopStride;
922
923 ShenandoahHeap* heap = ShenandoahHeap::heap();
924 ShenandoahObjToScanQueueSet* queues = task_queues();
925 ShenandoahObjToScanQueue* q;
926 ShenandoahMarkTask t;
927
928 /*
929 * Process outstanding queues, if any.
930 *
931 * There can be more queues than workers. To deal with the imbalance, we claim
932 * extra queues first. Since marking can push new tasks into the queue associated
933 * with this worker id, we come back to process this queue in the normal loop.
934 */
935 assert(queues->get_reserved() == heap->workers()->active_workers(),
936 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
937
938 q = queues->claim_next();
939 while (q != NULL) {
940 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
941 return;
942 }
943
944 for (uint i = 0; i < stride; i++) {
945 if (q->pop(t)) {
946 do_task<T>(q, cl, live_data, &t);
947 } else {
948 assert(q->is_empty(), "Must be empty");
949 q = queues->claim_next();
950 break;
951 }
952 }
953 }
954 q = get_queue(worker_id);
955
956 ShenandoahSATBBufferClosure drain_satb(q);
957 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
958
959 /*
960 * Normal marking loop:
961 */
962 while (true) {
963 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
964 return;
965 }
966
967 while (satb_mq_set.completed_buffers_num() > 0) {
968 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
969 }
970
971 uint work = 0;
972 for (uint i = 0; i < stride; i++) {
973 if (q->pop(t) ||
974 queues->steal(worker_id, t)) {
975 do_task<T>(q, cl, live_data, &t);
976 work++;
977 } else {
978 break;
979 }
980 }
981
982 if (work == 0) {
983 // No work encountered in current stride, try to terminate.
984 // Need to leave the STS here otherwise it might block safepoints.
985 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE);
986 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
987 ShenandoahTerminatorTerminator tt(heap);
988 if (terminator->offer_termination(&tt)) return;
989 }
990 }
991 }
992
993 bool ShenandoahConcurrentMark::claim_codecache() {
994 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
995 return _claimed_codecache.try_set();
996 }
997
998 void ShenandoahConcurrentMark::clear_claim_codecache() {
999 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1000 _claimed_codecache.unset();
1001 }