1 /*
2 * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29
30 #include "gc/shared/weakProcessor.inline.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/referenceProcessor.hpp"
33 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
34 #include "gc/shared/strongRootsScope.hpp"
35
36 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
37 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
38 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
39 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
40 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
41 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
42 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
43 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
44 #include "gc/shenandoah/shenandoahTimingTracker.hpp"
45 #include "gc/shenandoah/shenandoahUtils.hpp"
46
47 #include "memory/iterator.inline.hpp"
48 #include "memory/metaspace.hpp"
49 #include "memory/resourceArea.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "runtime/handles.inline.hpp"
52
53 template<UpdateRefsMode UPDATE_REFS>
54 class ShenandoahInitMarkRootsClosure : public OopClosure {
55 private:
56 ShenandoahObjToScanQueue* _queue;
57 ShenandoahHeap* _heap;
58 ShenandoahMarkingContext* const _mark_context;
59
60 template <class T>
61 inline void do_oop_work(T* p) {
62 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, NO_DEDUP>(p, _heap, _queue, _mark_context);
63 }
64
65 public:
66 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) :
67 _queue(q),
68 _heap(ShenandoahHeap::heap()),
69 _mark_context(_heap->marking_context()) {};
70
71 void do_oop(narrowOop* p) { do_oop_work(p); }
72 void do_oop(oop* p) { do_oop_work(p); }
73 };
74
75 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) :
76 MetadataVisitingOopIterateClosure(rp),
77 _queue(q),
78 _heap(ShenandoahHeap::heap()),
79 _mark_context(_heap->marking_context())
80 { }
81
82 template<UpdateRefsMode UPDATE_REFS>
83 class ShenandoahInitMarkRootsTask : public AbstractGangTask {
84 private:
85 ShenandoahAllRootScanner* _rp;
86 bool _process_refs;
87 public:
88 ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp, bool process_refs) :
89 AbstractGangTask("Shenandoah init mark roots task"),
90 _rp(rp),
91 _process_refs(process_refs) {
92 }
93
94 void work(uint worker_id) {
95 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
96 ShenandoahParallelWorkerSession worker_session(worker_id);
97
98 ShenandoahHeap* heap = ShenandoahHeap::heap();
99 ShenandoahObjToScanQueueSet* queues = heap->concurrent_mark()->task_queues();
100 assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id);
101
102 ShenandoahObjToScanQueue* q = queues->queue(worker_id);
103
104 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
105 do_work(heap, &mark_cl, worker_id);
106 }
107
108 private:
109 void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) {
110 // The rationale for selecting the roots to scan is as follows:
111 // a. With unload_classes = true, we only want to scan the actual strong roots from the
112 // code cache. This will allow us to identify the dead classes, unload them, *and*
113 // invalidate the relevant code cache blobs. This could be only done together with
114 // class unloading.
115 // b. With unload_classes = false, we have to nominally retain all the references from code
116 // cache, because there could be the case of embedded class/oop in the generated code,
117 // which we will never visit during mark. Without code cache invalidation, as in (a),
118 // we risk executing that code cache blob, and crashing.
119 if (heap->unload_classes()) {
120 _rp->strong_roots_do(worker_id, oops);
121 } else {
122 _rp->roots_do(worker_id, oops);
123 }
124 }
125 };
126
127 class ShenandoahUpdateRootsTask : public AbstractGangTask {
128 private:
129 ShenandoahRootUpdater* _root_updater;
130 public:
131 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater) :
132 AbstractGangTask("Shenandoah update roots task"),
133 _root_updater(root_updater) {
134 }
135
136 void work(uint worker_id) {
137 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
138 ShenandoahParallelWorkerSession worker_session(worker_id);
139
140 ShenandoahHeap* heap = ShenandoahHeap::heap();
141 ShenandoahUpdateRefsClosure cl;
142 AlwaysTrueClosure always_true;
143 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
144 }
145 };
146
147 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
148 private:
149 ShenandoahConcurrentMark* _cm;
150 ShenandoahTaskTerminator* _terminator;
151
152 public:
153 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator) :
154 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) {
155 }
156
157 void work(uint worker_id) {
158 ShenandoahHeap* heap = ShenandoahHeap::heap();
159 ShenandoahConcurrentWorkerSession worker_session(worker_id);
160 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
161 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
162 ReferenceProcessor* rp;
163 if (heap->process_references()) {
164 rp = heap->ref_processor();
165 shenandoah_assert_rp_isalive_installed();
166 } else {
167 rp = NULL;
168 }
169
170 _cm->concurrent_scan_code_roots(worker_id, rp);
171 _cm->mark_loop(worker_id, _terminator, rp,
172 true, // cancellable
173 ShenandoahStringDedup::is_enabled()); // perform string dedup
174 }
175 };
176
177 class ShenandoahSATBThreadsClosure : public ThreadClosure {
178 private:
179 ShenandoahSATBBufferClosure* _satb_cl;
180 uintx _claim_token;
181
182 public:
183 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
184 _satb_cl(satb_cl),
185 _claim_token(Threads::thread_claim_token()) {}
186
187 void do_thread(Thread* thread) {
188 if (thread->claim_threads_do(true, _claim_token)) {
189 ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl);
190 }
191 }
192 };
193
194 class ShenandoahFinalMarkingTask : public AbstractGangTask {
195 private:
196 ShenandoahConcurrentMark* _cm;
197 ShenandoahTaskTerminator* _terminator;
198 bool _dedup_string;
199
200 public:
201 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) :
202 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
203 }
204
205 void work(uint worker_id) {
206 ShenandoahHeap* heap = ShenandoahHeap::heap();
207
208 ShenandoahParallelWorkerSession worker_session(worker_id);
209 // First drain remaining SATB buffers.
210 // Notice that this is not strictly necessary for mark-compact. But since
211 // it requires a StrongRootsScope around the task, we need to claim the
212 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
213 // full-gc.
214 {
215 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
216 ShenandoahSATBBufferClosure cl(q);
217 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
218 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
219 ShenandoahSATBThreadsClosure tc(&cl);
220 Threads::threads_do(&tc);
221 }
222
223 ReferenceProcessor* rp;
224 if (heap->process_references()) {
225 rp = heap->ref_processor();
226 shenandoah_assert_rp_isalive_installed();
227 } else {
228 rp = NULL;
229 }
230
231 if (heap->is_degenerated_gc_in_progress()) {
232 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
233 // let's check here.
234 _cm->concurrent_scan_code_roots(worker_id, rp);
235 }
236
237 _cm->mark_loop(worker_id, _terminator, rp,
238 false, // not cancellable
239 _dedup_string);
240
241 assert(_cm->task_queues()->is_empty(), "Should be empty");
242 }
243 };
244
245 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
246 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
247 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
248
249 ShenandoahHeap* heap = ShenandoahHeap::heap();
250
251 ShenandoahGCPhase phase(root_phase);
252
253 WorkGang* workers = heap->workers();
254 uint nworkers = workers->active_workers();
255
256 assert(nworkers <= task_queues()->size(), "Just check");
257
258 ShenandoahAllRootScanner root_proc(nworkers, root_phase);
259 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
260 task_queues()->reserve(nworkers);
261
262 if (heap->has_forwarded_objects()) {
263 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references());
264 workers->run_task(&mark_roots);
265 } else {
266 // No need to update references, which means the heap is stable.
267 // Can save time not walking through forwarding pointers.
268 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references());
269 workers->run_task(&mark_roots);
270 }
271
272 if (ShenandoahConcurrentScanCodeRoots) {
273 clear_claim_codecache();
274 }
275 }
276
277 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
278 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
279
280 bool update_code_cache = true; // initialize to safer value
281 switch (root_phase) {
282 case ShenandoahPhaseTimings::update_roots:
283 case ShenandoahPhaseTimings::final_update_refs_roots:
284 update_code_cache = false;
285 break;
286 case ShenandoahPhaseTimings::full_gc_roots:
287 case ShenandoahPhaseTimings::degen_gc_update_roots:
288 update_code_cache = true;
289 break;
290 default:
291 ShouldNotReachHere();
292 }
293
294 ShenandoahGCPhase phase(root_phase);
295
296 #if COMPILER2_OR_JVMCI
297 DerivedPointerTable::clear();
298 #endif
299
300 uint nworkers = _heap->workers()->active_workers();
301
302 ShenandoahRootUpdater root_updater(nworkers, root_phase, update_code_cache);
303 ShenandoahUpdateRootsTask update_roots(&root_updater);
304 _heap->workers()->run_task(&update_roots);
305
306 #if COMPILER2_OR_JVMCI
307 DerivedPointerTable::update_pointers();
308 #endif
309 }
310
311 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask {
312 private:
313 ShenandoahThreadRoots _thread_roots;
314 ShenandoahPhaseTimings::Phase _phase;
315 public:
316 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) :
317 AbstractGangTask("Shenandoah Update Thread Roots"),
318 _thread_roots(is_par),
319 _phase(phase) {
320 ShenandoahHeap::heap()->phase_timings()->record_workers_start(_phase);
321 }
322
323 ~ShenandoahUpdateThreadRootsTask() {
324 ShenandoahHeap::heap()->phase_timings()->record_workers_end(_phase);
325 }
326 void work(uint worker_id) {
327 ShenandoahUpdateRefsClosure cl;
328 _thread_roots.oops_do(&cl, NULL, worker_id);
329 }
330 };
331
332 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) {
333 WorkGang* workers = _heap->workers();
334 bool is_par = workers->active_workers() > 1;
335 #if COMPILER2_OR_JVMCI
336 DerivedPointerTable::clear();
337 #endif
338 ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
339 workers->run_task(&task);
340 #if COMPILER2_OR_JVMCI
341 DerivedPointerTable::update_pointers();
342 #endif
343 }
344
345 void ShenandoahConcurrentMark::initialize(uint workers) {
346 _heap = ShenandoahHeap::heap();
347
348 uint num_queues = MAX2(workers, 1U);
349
350 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
351
352 for (uint i = 0; i < num_queues; ++i) {
353 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
354 task_queue->initialize();
355 _task_queues->register_queue(i, task_queue);
356 }
357 }
358
359 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
360 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
361 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
362 if (!_heap->unload_classes()) {
363 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
364 // TODO: We can not honor StringDeduplication here, due to lock ranking
365 // inversion. So, we may miss some deduplication candidates.
366 if (_heap->has_forwarded_objects()) {
367 ShenandoahMarkResolveRefsClosure cl(q, rp);
368 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
369 CodeCache::blobs_do(&blobs);
370 } else {
371 ShenandoahMarkRefsClosure cl(q, rp);
372 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
373 CodeCache::blobs_do(&blobs);
374 }
375 }
376 }
377 }
378
379 void ShenandoahConcurrentMark::mark_from_roots() {
380 WorkGang* workers = _heap->workers();
381 uint nworkers = workers->active_workers();
382
383 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
384
385 if (_heap->process_references()) {
386 ReferenceProcessor* rp = _heap->ref_processor();
387 rp->set_active_mt_degree(nworkers);
388
389 // enable ("weak") refs discovery
390 rp->enable_discovery(true /*verify_no_refs*/);
391 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
392 }
393
394 shenandoah_assert_rp_isalive_not_installed();
395 ShenandoahIsAliveSelector is_alive;
396 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
397
398 task_queues()->reserve(nworkers);
399
400 {
401 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
402 ShenandoahTaskTerminator terminator(nworkers, task_queues());
403 ShenandoahConcurrentMarkingTask task(this, &terminator);
404 workers->run_task(&task);
405 }
406
407 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
408 }
409
410 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
411 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
412
413 uint nworkers = _heap->workers()->active_workers();
414
415 // Finally mark everything else we've got in our queues during the previous steps.
416 // It does two different things for concurrent vs. mark-compact GC:
417 // - For concurrent GC, it starts with empty task queues, drains the remaining
418 // SATB buffers, and then completes the marking closure.
419 // - For mark-compact GC, it starts out with the task queues seeded by initial
420 // root scan, and completes the closure, thus marking through all live objects
421 // The implementation is the same, so it's shared here.
422 {
423 ShenandoahGCPhase phase(full_gc ?
424 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
425 ShenandoahPhaseTimings::finish_queues);
426 task_queues()->reserve(nworkers);
427
428 shenandoah_assert_rp_isalive_not_installed();
429 ShenandoahIsAliveSelector is_alive;
430 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
431
432 ShenandoahTerminationTracker termination_tracker(full_gc ?
433 ShenandoahPhaseTimings::full_gc_mark_termination :
434 ShenandoahPhaseTimings::termination);
435
436 StrongRootsScope scope(nworkers);
437 ShenandoahTaskTerminator terminator(nworkers, task_queues());
438 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
439 _heap->workers()->run_task(&task);
440 }
441
442 assert(task_queues()->is_empty(), "Should be empty");
443
444 // When we're done marking everything, we process weak references.
445 if (_heap->process_references()) {
446 weak_refs_work(full_gc);
447 }
448
449 weak_roots_work();
450
451 // And finally finish class unloading
452 if (_heap->unload_classes()) {
453 _heap->unload_classes_and_cleanup_tables(full_gc);
454 } else if (ShenandoahStringDedup::is_enabled()) {
455 ShenandoahIsAliveSelector alive;
456 BoolObjectClosure* is_alive = alive.is_alive_closure();
457 ShenandoahStringDedup::unlink_or_oops_do(is_alive, NULL, false);
458 }
459 assert(task_queues()->is_empty(), "Should be empty");
460 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
461 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
462
463 // Resize Metaspace
464 MetaspaceGC::compute_new_size();
465 }
466
467 // Weak Reference Closures
468 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
469 uint _worker_id;
470 ShenandoahTaskTerminator* _terminator;
471 bool _reset_terminator;
472
473 public:
474 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false):
475 _worker_id(worker_id),
476 _terminator(t),
477 _reset_terminator(reset_terminator) {
478 }
479
480 void do_void() {
481 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
482
483 ShenandoahHeap* sh = ShenandoahHeap::heap();
484 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
485 assert(sh->process_references(), "why else would we be here?");
486 ReferenceProcessor* rp = sh->ref_processor();
487
488 shenandoah_assert_rp_isalive_installed();
489
490 scm->mark_loop(_worker_id, _terminator, rp,
491 false, // not cancellable
492 false); // do not do strdedup
493
494 if (_reset_terminator) {
495 _terminator->reset_for_reuse();
496 }
497 }
498 };
499
500 class ShenandoahCMKeepAliveClosure : public OopClosure {
501 private:
502 ShenandoahObjToScanQueue* _queue;
503 ShenandoahHeap* _heap;
504 ShenandoahMarkingContext* const _mark_context;
505
506 template <class T>
507 inline void do_oop_work(T* p) {
508 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
509 }
510
511 public:
512 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
513 _queue(q),
514 _heap(ShenandoahHeap::heap()),
515 _mark_context(_heap->marking_context()) {}
516
517 void do_oop(narrowOop* p) { do_oop_work(p); }
518 void do_oop(oop* p) { do_oop_work(p); }
519 };
520
521 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
522 private:
523 ShenandoahObjToScanQueue* _queue;
524 ShenandoahHeap* _heap;
525 ShenandoahMarkingContext* const _mark_context;
526
527 template <class T>
528 inline void do_oop_work(T* p) {
529 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
530 }
531
532 public:
533 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
534 _queue(q),
535 _heap(ShenandoahHeap::heap()),
536 _mark_context(_heap->marking_context()) {}
537
538 void do_oop(narrowOop* p) { do_oop_work(p); }
539 void do_oop(oop* p) { do_oop_work(p); }
540 };
541
542 class ShenandoahWeakUpdateClosure : public OopClosure {
543 private:
544 ShenandoahHeap* const _heap;
545
546 template <class T>
547 inline void do_oop_work(T* p) {
548 oop o = _heap->maybe_update_with_forwarded(p);
549 shenandoah_assert_marked_except(p, o, o == NULL);
550 }
551
552 public:
553 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
554
555 void do_oop(narrowOop* p) { do_oop_work(p); }
556 void do_oop(oop* p) { do_oop_work(p); }
557 };
558
559 class ShenandoahWeakAssertNotForwardedClosure : public OopClosure {
560 private:
561 template <class T>
562 inline void do_oop_work(T* p) {
563 #ifdef ASSERT
564 T o = RawAccess<>::oop_load(p);
565 if (!CompressedOops::is_null(o)) {
566 oop obj = CompressedOops::decode_not_null(o);
567 shenandoah_assert_not_forwarded(p, obj);
568 }
569 #endif
570 }
571
572 public:
573 ShenandoahWeakAssertNotForwardedClosure() {}
574
575 void do_oop(narrowOop* p) { do_oop_work(p); }
576 void do_oop(oop* p) { do_oop_work(p); }
577 };
578
579 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
580 private:
581 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
582 ShenandoahTaskTerminator* _terminator;
583
584 public:
585 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
586 ShenandoahTaskTerminator* t) :
587 AbstractGangTask("Process reference objects in parallel"),
588 _proc_task(proc_task),
589 _terminator(t) {
590 }
591
592 void work(uint worker_id) {
593 ResourceMark rm;
594 HandleMark hm;
595 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
596 ShenandoahHeap* heap = ShenandoahHeap::heap();
597 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
598 if (heap->has_forwarded_objects()) {
599 ShenandoahForwardedIsAliveClosure is_alive;
600 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
601 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
602 } else {
603 ShenandoahIsAliveClosure is_alive;
604 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
605 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
606 }
607 }
608 };
609
610 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
611 private:
612 WorkGang* _workers;
613
614 public:
615 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
616 _workers(workers) {
617 }
618
619 // Executes a task using worker threads.
620 void execute(ProcessTask& task, uint ergo_workers) {
621 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
622
623 ShenandoahHeap* heap = ShenandoahHeap::heap();
624 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
625 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
626 ergo_workers,
627 /* do_check = */ false);
628 uint nworkers = _workers->active_workers();
629 cm->task_queues()->reserve(nworkers);
630 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
631 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
632 _workers->run_task(&proc_task_proxy);
633 }
634 };
635
636 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
637 assert(_heap->process_references(), "sanity");
638
639 ShenandoahPhaseTimings::Phase phase_root =
640 full_gc ?
641 ShenandoahPhaseTimings::full_gc_weakrefs :
642 ShenandoahPhaseTimings::weakrefs;
643
644 ShenandoahGCPhase phase(phase_root);
645
646 ReferenceProcessor* rp = _heap->ref_processor();
647
648 // NOTE: We cannot shortcut on has_discovered_references() here, because
649 // we will miss marking JNI Weak refs then, see implementation in
650 // ReferenceProcessor::process_discovered_references.
651 weak_refs_work_doit(full_gc);
652
653 rp->verify_no_references_recorded();
654 assert(!rp->discovery_enabled(), "Post condition");
655
656 }
657
658 // Process leftover weak oops: update them, if needed or assert they do not
659 // need updating otherwise.
660 // Weak processor API requires us to visit the oops, even if we are not doing
661 // anything to them.
662 void ShenandoahConcurrentMark::weak_roots_work() {
663 WorkGang* workers = _heap->workers();
664 OopClosure* keep_alive = &do_nothing_cl;
665 #ifdef ASSERT
666 ShenandoahWeakAssertNotForwardedClosure verify_cl;
667 keep_alive = &verify_cl;
668 #endif
669 ShenandoahIsAliveClosure is_alive;
670 WeakProcessor::weak_oops_do(workers, &is_alive, keep_alive, 1);
671 }
672
673 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
674 ReferenceProcessor* rp = _heap->ref_processor();
675
676 ShenandoahPhaseTimings::Phase phase_process =
677 full_gc ?
678 ShenandoahPhaseTimings::full_gc_weakrefs_process :
679 ShenandoahPhaseTimings::weakrefs_process;
680
681 ShenandoahPhaseTimings::Phase phase_process_termination =
682 full_gc ?
683 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
684 ShenandoahPhaseTimings::weakrefs_termination;
685
686 shenandoah_assert_rp_isalive_not_installed();
687 ShenandoahIsAliveSelector is_alive;
688 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
689
690 WorkGang* workers = _heap->workers();
691 uint nworkers = workers->active_workers();
692
693 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
694 rp->set_active_mt_degree(nworkers);
695
696 assert(task_queues()->is_empty(), "Should be empty");
697
698 // complete_gc and keep_alive closures instantiated here are only needed for
699 // single-threaded path in RP. They share the queue 0 for tracking work, which
700 // simplifies implementation. Since RP may decide to call complete_gc several
701 // times, we need to be able to reuse the terminator.
702 uint serial_worker_id = 0;
703 ShenandoahTaskTerminator terminator(1, task_queues());
704 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
705
706 ShenandoahRefProcTaskExecutor executor(workers);
707
708 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
709
710 {
711 ShenandoahGCPhase phase(phase_process);
712 ShenandoahTerminationTracker phase_term(phase_process_termination);
713
714 if (_heap->has_forwarded_objects()) {
715 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
716 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
717 &complete_gc, &executor,
718 &pt);
719
720 } else {
721 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
722 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
723 &complete_gc, &executor,
724 &pt);
725
726 }
727
728 pt.print_all_references();
729
730 assert(task_queues()->is_empty(), "Should be empty");
731 }
732 }
733
734 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
735 private:
736 ShenandoahHeap* const _heap;
737 public:
738 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
739 virtual bool should_return() { return _heap->cancelled_gc(); }
740 };
741
742 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
743 public:
744 void do_void() {
745 ShenandoahHeap* sh = ShenandoahHeap::heap();
746 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
747 assert(sh->process_references(), "why else would we be here?");
748 ShenandoahTaskTerminator terminator(1, scm->task_queues());
749
750 ReferenceProcessor* rp = sh->ref_processor();
751 shenandoah_assert_rp_isalive_installed();
752
753 scm->mark_loop(0, &terminator, rp,
754 false, // not cancellable
755 false); // do not do strdedup
756 }
757 };
758
759 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
760 private:
761 ShenandoahObjToScanQueue* _queue;
762 ShenandoahHeap* _heap;
763 ShenandoahMarkingContext* const _mark_context;
764
765 template <class T>
766 inline void do_oop_work(T* p) {
767 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context);
768 }
769
770 public:
771 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
772 _queue(q),
773 _heap(ShenandoahHeap::heap()),
774 _mark_context(_heap->marking_context()) {}
775
776 void do_oop(narrowOop* p) { do_oop_work(p); }
777 void do_oop(oop* p) { do_oop_work(p); }
778 };
779
780 class ShenandoahPrecleanTask : public AbstractGangTask {
781 private:
782 ReferenceProcessor* _rp;
783
784 public:
785 ShenandoahPrecleanTask(ReferenceProcessor* rp) :
786 AbstractGangTask("Precleaning task"),
787 _rp(rp) {}
788
789 void work(uint worker_id) {
790 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
791 ShenandoahParallelWorkerSession worker_session(worker_id);
792
793 ShenandoahHeap* sh = ShenandoahHeap::heap();
794
795 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
796
797 ShenandoahCancelledGCYieldClosure yield;
798 ShenandoahPrecleanCompleteGCClosure complete_gc;
799
800 if (sh->has_forwarded_objects()) {
801 ShenandoahForwardedIsAliveClosure is_alive;
802 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q);
803 ResourceMark rm;
804 _rp->preclean_discovered_references(&is_alive, &keep_alive,
805 &complete_gc, &yield,
806 NULL);
807 } else {
808 ShenandoahIsAliveClosure is_alive;
809 ShenandoahCMKeepAliveClosure keep_alive(q);
810 ResourceMark rm;
811 _rp->preclean_discovered_references(&is_alive, &keep_alive,
812 &complete_gc, &yield,
813 NULL);
814 }
815 }
816 };
817
818 void ShenandoahConcurrentMark::preclean_weak_refs() {
819 // Pre-cleaning weak references before diving into STW makes sense at the
820 // end of concurrent mark. This will filter out the references which referents
821 // are alive. Note that ReferenceProcessor already filters out these on reference
822 // discovery, and the bulk of work is done here. This phase processes leftovers
823 // that missed the initial filtering, i.e. when referent was marked alive after
824 // reference was discovered by RP.
825
826 assert(_heap->process_references(), "sanity");
827
828 // Shortcut if no references were discovered to avoid winding up threads.
829 ReferenceProcessor* rp = _heap->ref_processor();
830 if (!rp->has_discovered_references()) {
831 return;
832 }
833
834 assert(task_queues()->is_empty(), "Should be empty");
835
836 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
837
838 shenandoah_assert_rp_isalive_not_installed();
839 ShenandoahIsAliveSelector is_alive;
840 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
841
842 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup
843 // queues and other goodies. When upstream ReferenceProcessor starts supporting
844 // parallel precleans, we can extend this to more threads.
845 WorkGang* workers = _heap->workers();
846 uint nworkers = workers->active_workers();
847 assert(nworkers == 1, "This code uses only a single worker");
848 task_queues()->reserve(nworkers);
849
850 ShenandoahPrecleanTask task(rp);
851 workers->run_task(&task);
852
853 assert(task_queues()->is_empty(), "Should be empty");
854 }
855
856 void ShenandoahConcurrentMark::cancel() {
857 // Clean up marking stacks.
858 ShenandoahObjToScanQueueSet* queues = task_queues();
859 queues->clear();
860
861 // Cancel SATB buffers.
862 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
863 }
864
865 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
866 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
867 return _task_queues->queue(worker_id);
868 }
869
870 template <bool CANCELLABLE>
871 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp,
872 bool strdedup) {
873 ShenandoahObjToScanQueue* q = get_queue(w);
874
875 jushort* ld = _heap->get_liveness_cache(w);
876
877 // TODO: We can clean up this if we figure out how to do templated oop closures that
878 // play nice with specialized_oop_iterators.
879 if (_heap->unload_classes()) {
880 if (_heap->has_forwarded_objects()) {
881 if (strdedup) {
882 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
883 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
884 } else {
885 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
886 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
887 }
888 } else {
889 if (strdedup) {
890 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
891 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
892 } else {
893 ShenandoahMarkRefsMetadataClosure cl(q, rp);
894 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
895 }
896 }
897 } else {
898 if (_heap->has_forwarded_objects()) {
899 if (strdedup) {
900 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
901 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
902 } else {
903 ShenandoahMarkUpdateRefsClosure cl(q, rp);
904 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
905 }
906 } else {
907 if (strdedup) {
908 ShenandoahMarkRefsDedupClosure cl(q, rp);
909 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
910 } else {
911 ShenandoahMarkRefsClosure cl(q, rp);
912 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
913 }
914 }
915 }
916
917 _heap->flush_liveness_cache(w);
918 }
919
920 template <class T, bool CANCELLABLE>
921 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) {
922 uintx stride = ShenandoahMarkLoopStride;
923
924 ShenandoahHeap* heap = ShenandoahHeap::heap();
925 ShenandoahObjToScanQueueSet* queues = task_queues();
926 ShenandoahObjToScanQueue* q;
927 ShenandoahMarkTask t;
928
929 /*
930 * Process outstanding queues, if any.
931 *
932 * There can be more queues than workers. To deal with the imbalance, we claim
933 * extra queues first. Since marking can push new tasks into the queue associated
934 * with this worker id, we come back to process this queue in the normal loop.
935 */
936 assert(queues->get_reserved() == heap->workers()->active_workers(),
937 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
938
939 q = queues->claim_next();
940 while (q != NULL) {
941 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
942 return;
943 }
944
945 for (uint i = 0; i < stride; i++) {
946 if (q->pop(t)) {
947 do_task<T>(q, cl, live_data, &t);
948 } else {
949 assert(q->is_empty(), "Must be empty");
950 q = queues->claim_next();
951 break;
952 }
953 }
954 }
955 q = get_queue(worker_id);
956
957 ShenandoahSATBBufferClosure drain_satb(q);
958 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
959
960 /*
961 * Normal marking loop:
962 */
963 while (true) {
964 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
965 return;
966 }
967
968 while (satb_mq_set.completed_buffers_num() > 0) {
969 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
970 }
971
972 uint work = 0;
973 for (uint i = 0; i < stride; i++) {
974 if (q->pop(t) ||
975 queues->steal(worker_id, t)) {
976 do_task<T>(q, cl, live_data, &t);
977 work++;
978 } else {
979 break;
980 }
981 }
982
983 if (work == 0) {
984 // No work encountered in current stride, try to terminate.
985 // Need to leave the STS here otherwise it might block safepoints.
986 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
987 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
988 ShenandoahTerminatorTerminator tt(heap);
989 if (terminator->offer_termination(&tt)) return;
990 }
991 }
992 }
993
994 bool ShenandoahConcurrentMark::claim_codecache() {
995 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
996 return _claimed_codecache.try_set();
997 }
998
999 void ShenandoahConcurrentMark::clear_claim_codecache() {
1000 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1001 _claimed_codecache.unset();
1002 }