1 /*
2 * Copyright (c) 2013, 2017, Red Hat, Inc. and/or its affiliates.
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 #include "classfile/stringTable.hpp"
26 #include "gc/shared/gcTimer.hpp"
27 #include "gc/shared/parallelCleaning.hpp"
28 #include "gc/shared/referenceProcessor.hpp"
29 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
30 #include "gc/shared/strongRootsScope.hpp"
31 #include "gc/shared/suspendibleThreadSet.hpp"
32 #include "gc/shenandoah/brooksPointer.hpp"
33 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
34 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
35 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
36 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
37 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
38 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
39 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
40 #include "gc/shenandoah/shenandoahOopClosures.hpp"
41 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
42 #include "gc/shenandoah/shenandoahUtils.hpp"
43 #include "gc/shared/weakProcessor.hpp"
44 #include "code/codeCache.hpp"
45 #include "classfile/symbolTable.hpp"
46 #include "classfile/systemDictionary.hpp"
47 #include "memory/iterator.inline.hpp"
48 #include "oops/oop.inline.hpp"
49 #include "gc/shared/taskqueue.inline.hpp"
50 #include "logging/logStream.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, false /* string 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->next_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->next_marking_context())
79 { }
80
81
82 template<UpdateRefsMode UPDATE_REFS>
83 class ShenandoahInitMarkRootsTask : public AbstractGangTask {
84 private:
85 ShenandoahRootProcessor* _rp;
86 bool _process_refs;
87 public:
88 ShenandoahInitMarkRootsTask(ShenandoahRootProcessor* 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 ShenandoahWorkerSession worker_session(worker_id);
97
98 ShenandoahHeap* heap = ShenandoahHeap::heap();
99 ShenandoahObjToScanQueueSet* queues = heap->concurrentMark()->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 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
104 CLDToOopClosure cldCl(&mark_cl);
105 MarkingCodeBlobClosure blobsCl(&mark_cl, ! CodeBlobToOopClosure::FixRelocations);
106
107 // The rationale for selecting the roots to scan is as follows:
108 // a. With unload_classes = true, we only want to scan the actual strong roots from the
109 // code cache. This will allow us to identify the dead classes, unload them, *and*
110 // invalidate the relevant code cache blobs. This could be only done together with
111 // class unloading.
112 // b. With unload_classes = false, we have to nominally retain all the references from code
113 // cache, because there could be the case of embedded class/oop in the generated code,
114 // which we will never visit during mark. Without code cache invalidation, as in (a),
115 // we risk executing that code cache blob, and crashing.
116 // c. With ShenandoahConcurrentScanCodeRoots, we avoid scanning the entire code cache here,
117 // and instead do that in concurrent phase under the relevant lock. This saves init mark
118 // pause time.
119
120 ResourceMark m;
121 if (heap->concurrentMark()->unload_classes()) {
122 _rp->process_strong_roots(&mark_cl, _process_refs ? NULL : &mark_cl, &cldCl, NULL, &blobsCl, NULL, worker_id);
123 } else {
124 if (ShenandoahConcurrentScanCodeRoots) {
125 CodeBlobClosure* code_blobs = NULL;
126 #ifdef ASSERT
127 ShenandoahAssertToSpaceClosure assert_to_space_oops;
128 CodeBlobToOopClosure assert_to_space(&assert_to_space_oops, !CodeBlobToOopClosure::FixRelocations);
129 // If conc code cache evac is disabled, code cache should have only to-space ptrs.
130 // Otherwise, it should have to-space ptrs only if mark does not update refs.
131 if (!heap->has_forwarded_objects()) {
132 code_blobs = &assert_to_space;
133 }
134 #endif
135 _rp->process_all_roots(&mark_cl, _process_refs ? NULL : &mark_cl, &cldCl, code_blobs, NULL, worker_id);
136 } else {
137 _rp->process_all_roots(&mark_cl, _process_refs ? NULL : &mark_cl, &cldCl, &blobsCl, NULL, worker_id);
138 }
139 }
140 }
141 };
142
143 class ShenandoahUpdateRootsTask : public AbstractGangTask {
144 private:
145 ShenandoahRootProcessor* _rp;
146 const bool _update_code_cache;
147 public:
148 ShenandoahUpdateRootsTask(ShenandoahRootProcessor* rp, bool update_code_cache) :
149 AbstractGangTask("Shenandoah update roots task"),
150 _rp(rp),
151 _update_code_cache(update_code_cache) {
152 }
153
154 void work(uint worker_id) {
155 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
156 ShenandoahWorkerSession worker_session(worker_id);
157
158 ShenandoahHeap* heap = ShenandoahHeap::heap();
159 ShenandoahUpdateRefsClosure cl;
160 CLDToOopClosure cldCl(&cl);
161
162 CodeBlobClosure* code_blobs;
163 CodeBlobToOopClosure update_blobs(&cl, CodeBlobToOopClosure::FixRelocations);
164 #ifdef ASSERT
165 ShenandoahAssertToSpaceClosure assert_to_space_oops;
166 CodeBlobToOopClosure assert_to_space(&assert_to_space_oops, !CodeBlobToOopClosure::FixRelocations);
167 #endif
168 if (_update_code_cache) {
169 code_blobs = &update_blobs;
170 } else {
171 code_blobs =
172 DEBUG_ONLY(&assert_to_space)
173 NOT_DEBUG(NULL);
174 }
175 _rp->process_all_roots(&cl, &cl, &cldCl, code_blobs, NULL, worker_id);
176 }
177 };
178
179 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
180 private:
181 ShenandoahConcurrentMark* _cm;
182 ParallelTaskTerminator* _terminator;
183 bool _update_refs;
184
185 public:
186 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ParallelTaskTerminator* terminator, bool update_refs) :
187 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator), _update_refs(update_refs) {
188 }
189
190
191 void work(uint worker_id) {
192 ShenandoahWorkerSession worker_session(worker_id);
193 SuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
194 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
195 jushort* live_data = _cm->get_liveness(worker_id);
196 ReferenceProcessor* rp;
197 if (_cm->process_references()) {
198 rp = ShenandoahHeap::heap()->ref_processor();
199 shenandoah_assert_rp_isalive_installed();
200 } else {
201 rp = NULL;
202 }
203
204 _cm->concurrent_scan_code_roots(worker_id, rp, _update_refs);
205 _cm->mark_loop(worker_id, _terminator, rp,
206 true, // cancellable
207 _cm->unload_classes(),
208 _update_refs,
209 ShenandoahStringDedup::is_enabled()); // perform string dedup
210 }
211 };
212
213 class ShenandoahSATBThreadsClosure : public ThreadClosure {
214 ShenandoahSATBBufferClosure* _satb_cl;
215 int _thread_parity;
216
217 public:
218 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
219 _satb_cl(satb_cl),
220 _thread_parity(Threads::thread_claim_parity()) {}
221
222 void do_thread(Thread* thread) {
223 if (thread->is_Java_thread()) {
224 if (thread->claim_oops_do(true, _thread_parity)) {
225 JavaThread* jt = (JavaThread*)thread;
226 ShenandoahThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(_satb_cl);
227 }
228 } else if (thread->is_VM_thread()) {
229 if (thread->claim_oops_do(true, _thread_parity)) {
230 ShenandoahBarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(_satb_cl);
231 }
232 }
233 }
234 };
235
236 class ShenandoahFinalMarkingTask : public AbstractGangTask {
237 private:
238 ShenandoahConcurrentMark* _cm;
239 ParallelTaskTerminator* _terminator;
240 bool _update_refs;
241 bool _unload_classes;
242 bool _dedup_string;
243
244 public:
245 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ParallelTaskTerminator* terminator,
246 bool update_refs, bool unload_classes, bool dedup_string) :
247 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator),
248 _update_refs(update_refs), _unload_classes(unload_classes), _dedup_string(dedup_string) {
249 }
250
251 void work(uint worker_id) {
252 ShenandoahWorkerSession worker_session(worker_id);
253 // First drain remaining SATB buffers.
254 // Notice that this is not strictly necessary for mark-compact. But since
255 // it requires a StrongRootsScope around the task, we need to claim the
256 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
257 // full-gc.
258 {
259 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
260 ShenandoahSATBBufferClosure cl(q);
261 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
262 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
263 ShenandoahSATBThreadsClosure tc(&cl);
264 Threads::threads_do(&tc);
265 }
266
267 ReferenceProcessor* rp;
268 if (_cm->process_references()) {
269 rp = ShenandoahHeap::heap()->ref_processor();
270 shenandoah_assert_rp_isalive_installed();
271 } else {
272 rp = NULL;
273 }
274
275 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
276 // let's check here.
277 _cm->concurrent_scan_code_roots(worker_id, rp, _update_refs);
278 _cm->mark_loop(worker_id, _terminator, rp,
279 false, // not cancellable
280 _unload_classes,
281 _update_refs,
282 _dedup_string);
283
284 assert(_cm->task_queues()->is_empty(), "Should be empty");
285 }
286 };
287
288 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
289 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
290 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
291
292 ShenandoahHeap* heap = ShenandoahHeap::heap();
293
294 ShenandoahGCPhase phase(root_phase);
295
296 WorkGang* workers = heap->workers();
297 uint nworkers = workers->active_workers();
298
299 assert(nworkers <= task_queues()->size(), "Just check");
300
301 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
302 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
303 task_queues()->reserve(nworkers);
304
305 if (heap->has_forwarded_objects()) {
306 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, process_references());
307 workers->run_task(&mark_roots);
308 } else {
309 // No need to update references, which means the heap is stable.
310 // Can save time not walking through forwarding pointers.
311 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, process_references());
312 workers->run_task(&mark_roots);
313 }
314
315 if (ShenandoahConcurrentScanCodeRoots) {
316 clear_claim_codecache();
317 }
318 }
319
320 void ShenandoahConcurrentMark::init_mark_roots() {
321 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
322 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
323
324 mark_roots(ShenandoahPhaseTimings::scan_roots);
325 }
326
327 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
328 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
329
330 bool update_code_cache = true; // initialize to safer value
331 switch (root_phase) {
332 case ShenandoahPhaseTimings::update_roots:
333 case ShenandoahPhaseTimings::final_update_refs_roots:
334 update_code_cache = false;
335 break;
336 case ShenandoahPhaseTimings::full_gc_roots:
337 case ShenandoahPhaseTimings::degen_gc_update_roots:
338 update_code_cache = true;
339 break;
340 default:
341 ShouldNotReachHere();
342 }
343
344 ShenandoahHeap* heap = ShenandoahHeap::heap();
345
346 ShenandoahGCPhase phase(root_phase);
347
348 #if defined(COMPILER2) || INCLUDE_JVMCI
349 DerivedPointerTable::clear();
350 #endif
351
352 uint nworkers = heap->workers()->active_workers();
353
354 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
355 ShenandoahUpdateRootsTask update_roots(&root_proc, update_code_cache);
356 heap->workers()->run_task(&update_roots);
357
358 #if defined(COMPILER2) || INCLUDE_JVMCI
359 DerivedPointerTable::update_pointers();
360 #endif
361 }
362
363 void ShenandoahConcurrentMark::initialize(uint workers) {
364 _heap = ShenandoahHeap::heap();
365
366 uint num_queues = MAX2(workers, 1U);
367
368 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
369
370 for (uint i = 0; i < num_queues; ++i) {
371 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
372 task_queue->initialize();
373 _task_queues->register_queue(i, task_queue);
374 }
375
376 size_t num_regions = ShenandoahHeap::heap()->num_regions();
377 _liveness_local = NEW_C_HEAP_ARRAY(jushort*, workers, mtGC);
378 for (uint worker = 0; worker < workers; worker++) {
379 _liveness_local[worker] = NEW_C_HEAP_ARRAY(jushort, num_regions, mtGC);
380 }
381 }
382
383 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp, bool update_refs) {
384 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
385 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
386 if (!unload_classes()) {
387 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
388 if (update_refs) {
389 ShenandoahMarkResolveRefsClosure cl(q, rp);
390 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
391 CodeCache::blobs_do(&blobs);
392 } else {
393 ShenandoahMarkRefsClosure cl(q, rp);
394 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
395 CodeCache::blobs_do(&blobs);
396 }
397 }
398 }
399 }
400
401 void ShenandoahConcurrentMark::mark_from_roots() {
402 ShenandoahHeap* sh = ShenandoahHeap::heap();
403 WorkGang* workers = sh->workers();
404 uint nworkers = workers->active_workers();
405
406 bool update_refs = sh->has_forwarded_objects();
407
408 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
409
410 if (process_references()) {
411 ReferenceProcessor* rp = sh->ref_processor();
412 rp->set_active_mt_degree(nworkers);
413
414 // enable ("weak") refs discovery
415 rp->enable_discovery(true /*verify_no_refs*/);
416 rp->setup_policy(sh->soft_ref_policy()->should_clear_all_soft_refs());
417 }
418
419 shenandoah_assert_rp_isalive_not_installed();
420 ShenandoahIsAliveSelector is_alive;
421 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), is_alive.is_alive_closure());
422
423 task_queues()->reserve(nworkers);
424
425 {
426 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
427 if (UseShenandoahOWST) {
428 ShenandoahTaskTerminator terminator(nworkers, task_queues());
429 ShenandoahConcurrentMarkingTask task(this, &terminator, update_refs);
430 workers->run_task(&task);
431 } else {
432 ParallelTaskTerminator terminator(nworkers, task_queues());
433 ShenandoahConcurrentMarkingTask task(this, &terminator, update_refs);
434 workers->run_task(&task);
435 }
436 }
437
438 assert(task_queues()->is_empty() || sh->cancelled_gc(), "Should be empty when not cancelled");
439 }
440
441 void ShenandoahConcurrentMark::finish_mark_from_roots() {
442 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
443
444 ShenandoahHeap* sh = ShenandoahHeap::heap();
445
446 shared_finish_mark_from_roots(/* full_gc = */ false);
447
448 if (sh->has_forwarded_objects()) {
449 update_roots(ShenandoahPhaseTimings::update_roots);
450 }
451 }
452
453 void ShenandoahConcurrentMark::shared_finish_mark_from_roots(bool full_gc) {
454 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
455
456 ShenandoahHeap* sh = ShenandoahHeap::heap();
457
458 uint nworkers = sh->workers()->active_workers();
459
460 // Finally mark everything else we've got in our queues during the previous steps.
461 // It does two different things for concurrent vs. mark-compact GC:
462 // - For concurrent GC, it starts with empty task queues, drains the remaining
463 // SATB buffers, and then completes the marking closure.
464 // - For mark-compact GC, it starts out with the task queues seeded by initial
465 // root scan, and completes the closure, thus marking through all live objects
466 // The implementation is the same, so it's shared here.
467 {
468 ShenandoahGCPhase phase(full_gc ?
469 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
470 ShenandoahPhaseTimings::finish_queues);
471 task_queues()->reserve(nworkers);
472
473 shenandoah_assert_rp_isalive_not_installed();
474 ShenandoahIsAliveSelector is_alive;
475 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), is_alive.is_alive_closure());
476
477 ShenandoahTerminationTracker termination_tracker(full_gc ?
478 ShenandoahPhaseTimings::full_gc_mark_termination :
479 ShenandoahPhaseTimings::termination);
480
481 StrongRootsScope scope(nworkers);
482 if (UseShenandoahOWST) {
483 ShenandoahTaskTerminator terminator(nworkers, task_queues());
484 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
485 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
486 sh->workers()->run_task(&task);
487 } else {
488 ParallelTaskTerminator terminator(nworkers, task_queues());
489 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
490 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
491 sh->workers()->run_task(&task);
492 }
493 }
494
495 assert(task_queues()->is_empty(), "Should be empty");
496
497 // When we're done marking everything, we process weak references.
498 if (process_references()) {
499 weak_refs_work(full_gc);
500 }
501
502 // And finally finish class unloading
503 if (unload_classes()) {
504 sh->unload_classes_and_cleanup_tables(full_gc);
505 }
506
507 assert(task_queues()->is_empty(), "Should be empty");
508 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
509 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
510 }
511
512 // Weak Reference Closures
513 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
514 uint _worker_id;
515 ParallelTaskTerminator* _terminator;
516 bool _reset_terminator;
517
518 public:
519 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ParallelTaskTerminator* t, bool reset_terminator = false):
520 _worker_id(worker_id),
521 _terminator(t),
522 _reset_terminator(reset_terminator) {
523 }
524
525 void do_void() {
526 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
527
528 ShenandoahHeap* sh = ShenandoahHeap::heap();
529 ShenandoahConcurrentMark* scm = sh->concurrentMark();
530 assert(scm->process_references(), "why else would we be here?");
531 ReferenceProcessor* rp = sh->ref_processor();
532
533 shenandoah_assert_rp_isalive_installed();
534
535 scm->mark_loop(_worker_id, _terminator, rp,
536 false, // not cancellable
537 scm->unload_classes(),
538 sh->has_forwarded_objects(),
539 false); // do not do strdedup
540
541 if (_reset_terminator) {
542 _terminator->reset_for_reuse();
543 }
544 }
545 };
546
547
548 class ShenandoahCMKeepAliveClosure : public OopClosure {
549 private:
550 ShenandoahObjToScanQueue* _queue;
551 ShenandoahHeap* _heap;
552 ShenandoahMarkingContext* const _mark_context;
553
554 template <class T>
555 inline void do_oop_work(T* p) {
556 ShenandoahConcurrentMark::mark_through_ref<T, NONE, false /* string dedup */>(p, _heap, _queue, _mark_context);
557 }
558
559 public:
560 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
561 _queue(q),
562 _heap(ShenandoahHeap::heap()),
563 _mark_context(_heap->next_marking_context()) {}
564
565 void do_oop(narrowOop* p) { do_oop_work(p); }
566 void do_oop(oop* p) { do_oop_work(p); }
567 };
568
569 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
570 private:
571 ShenandoahObjToScanQueue* _queue;
572 ShenandoahHeap* _heap;
573 ShenandoahMarkingContext* const _mark_context;
574
575 template <class T>
576 inline void do_oop_work(T* p) {
577 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, false /* string dedup */>(p, _heap, _queue, _mark_context);
578 }
579
580 public:
581 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
582 _queue(q),
583 _heap(ShenandoahHeap::heap()),
584 _mark_context(_heap->next_marking_context()) {}
585
586 void do_oop(narrowOop* p) { do_oop_work(p); }
587 void do_oop(oop* p) { do_oop_work(p); }
588 };
589
590 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
591
592 private:
593 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
594 ParallelTaskTerminator* _terminator;
595 public:
596
597 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
598 ParallelTaskTerminator* t) :
599 AbstractGangTask("Process reference objects in parallel"),
600 _proc_task(proc_task),
601 _terminator(t) {
602 }
603
604 void work(uint worker_id) {
605 ResourceMark rm;
606 HandleMark hm;
607 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
608 ShenandoahHeap* heap = ShenandoahHeap::heap();
609 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
610 if (heap->has_forwarded_objects()) {
611 ShenandoahForwardedIsAliveClosure is_alive;
612 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
613 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
614 } else {
615 ShenandoahIsAliveClosure is_alive;
616 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
617 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
618 }
619 }
620 };
621
622 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
623
624 private:
625 WorkGang* _workers;
626
627 public:
628
629 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
630 _workers(workers) {
631 }
632
633 // Executes a task using worker threads.
634 void execute(ProcessTask& task, uint ergo_workers) {
635 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
636
637 ShenandoahHeap* heap = ShenandoahHeap::heap();
638 ShenandoahConcurrentMark* cm = heap->concurrentMark();
639 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
640 ergo_workers,
641 /* do_check = */ false);
642 uint nworkers = _workers->active_workers();
643 cm->task_queues()->reserve(nworkers);
644 if (UseShenandoahOWST) {
645 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
646 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
647 if (nworkers == 1) {
648 proc_task_proxy.work(0);
649 } else {
650 _workers->run_task(&proc_task_proxy);
651 }
652 } else {
653 ParallelTaskTerminator terminator(nworkers, cm->task_queues());
654 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
655 if (nworkers == 1) {
656 proc_task_proxy.work(0);
657 } else {
658 _workers->run_task(&proc_task_proxy);
659 }
660 }
661 }
662 };
663
664
665 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
666 assert(process_references(), "sanity");
667
668 ShenandoahHeap* sh = ShenandoahHeap::heap();
669
670 ShenandoahPhaseTimings::Phase phase_root =
671 full_gc ?
672 ShenandoahPhaseTimings::full_gc_weakrefs :
673 ShenandoahPhaseTimings::weakrefs;
674
675 ShenandoahGCPhase phase(phase_root);
676
677 ReferenceProcessor* rp = sh->ref_processor();
678
679 // NOTE: We cannot shortcut on has_discovered_references() here, because
680 // we will miss marking JNI Weak refs then, see implementation in
681 // ReferenceProcessor::process_discovered_references.
682 weak_refs_work_doit(full_gc);
683
684 rp->verify_no_references_recorded();
685 assert(!rp->discovery_enabled(), "Post condition");
686
687 }
688
689 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
690 ShenandoahHeap* sh = ShenandoahHeap::heap();
691
692 ReferenceProcessor* rp = sh->ref_processor();
693
694 ShenandoahPhaseTimings::Phase phase_process =
695 full_gc ?
696 ShenandoahPhaseTimings::full_gc_weakrefs_process :
697 ShenandoahPhaseTimings::weakrefs_process;
698
699 ShenandoahPhaseTimings::Phase phase_process_termination =
700 full_gc ?
701 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
702 ShenandoahPhaseTimings::weakrefs_termination;
703
704 shenandoah_assert_rp_isalive_not_installed();
705 ShenandoahIsAliveSelector is_alive;
706 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
707
708 WorkGang* workers = sh->workers();
709 uint nworkers = workers->active_workers();
710
711 rp->setup_policy(sh->soft_ref_policy()->should_clear_all_soft_refs());
712 rp->set_active_mt_degree(nworkers);
713
714 assert(task_queues()->is_empty(), "Should be empty");
715
716 ShenandoahRefProcTaskExecutor executor(workers);
717
718 ReferenceProcessorPhaseTimes pt(sh->gc_timer(), rp->num_queues());
719
720 {
721 ShenandoahGCPhase phase(phase_process);
722 ShenandoahTerminationTracker phase_term(phase_process_termination);
723
724 // We don't use single-threaded closures, because we distinguish this
725 // in the executor. Assert that we should never actually get there.
726 ShouldNotReachHereBoolObjectClosure should_not_reach_here_is_alive;
727 ShouldNotReachHereOopClosure should_not_reach_here_keep_alive;
728 ShouldNotReachHereVoidClosure should_not_reach_here_complete;
729 rp->process_discovered_references(&should_not_reach_here_is_alive,
730 &should_not_reach_here_keep_alive,
731 &should_not_reach_here_complete,
732 &executor, &pt);
733
734 // Closures instantiated here are only needed for the single-threaded path in WeakProcessor.
735 // They share the queue 0 for tracking work, which simplifies implementation.
736 // TODO: As soon as WeakProcessor becomes MT-capable, these closures would become
737 // unnecessary, and could be removed.
738 uint serial_worker_id = 0;
739 ShenandoahPushWorkerQueuesScope scope(workers, task_queues(), 1, /* do_check = */ false);
740 ShenandoahForwardedIsAliveClosure is_alive;
741 if (sh->has_forwarded_objects()) {
742 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
743 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
744 } else {
745 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
746 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
747 }
748
749 pt.print_all_references();
750
751 assert(task_queues()->is_empty(), "Should be empty");
752 }
753 }
754
755 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
756 private:
757 ShenandoahHeap* const _heap;
758 public:
759 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
760 virtual bool should_return() { return _heap->cancelled_gc(); }
761 };
762
763 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
764 public:
765 void do_void() {
766 ShenandoahHeap* sh = ShenandoahHeap::heap();
767 ShenandoahConcurrentMark* scm = sh->concurrentMark();
768 assert(scm->process_references(), "why else would we be here?");
769 ParallelTaskTerminator terminator(1, scm->task_queues());
770
771 ReferenceProcessor* rp = sh->ref_processor();
772 shenandoah_assert_rp_isalive_installed();
773
774 scm->mark_loop(0, &terminator, rp,
775 false, // not cancellable
776 scm->unload_classes(),
777 sh->has_forwarded_objects(),
778 false); // do not do strdedup
779 }
780 };
781
782 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
783 private:
784 ShenandoahObjToScanQueue* _queue;
785 ShenandoahHeap* _heap;
786 ShenandoahMarkingContext* const _mark_context;
787
788 template <class T>
789 inline void do_oop_work(T* p) {
790 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, false /* string dedup */>(p, _heap, _queue, _mark_context);
791 }
792
793 public:
794 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
795 _queue(q),
796 _heap(ShenandoahHeap::heap()),
797 _mark_context(_heap->next_marking_context()) {}
798
799 void do_oop(narrowOop* p) { do_oop_work(p); }
800 void do_oop(oop* p) { do_oop_work(p); }
801 };
802
803 void ShenandoahConcurrentMark::preclean_weak_refs() {
804 // Pre-cleaning weak references before diving into STW makes sense at the
805 // end of concurrent mark. This will filter out the references which referents
806 // are alive. Note that ReferenceProcessor already filters out these on reference
807 // discovery, and the bulk of work is done here. This phase processes leftovers
808 // that missed the initial filtering, i.e. when referent was marked alive after
809 // reference was discovered by RP.
810
811 assert(process_references(), "sanity");
812
813 ShenandoahHeap* sh = ShenandoahHeap::heap();
814 ReferenceProcessor* rp = sh->ref_processor();
815
816 // Shortcut if no references were discovered to avoid winding up threads.
817 if (!rp->has_discovered_references()) {
818 return;
819 }
820
821 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
822
823 shenandoah_assert_rp_isalive_not_installed();
824 ShenandoahIsAliveSelector is_alive;
825 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
826
827 // Interrupt on cancelled GC
828 ShenandoahCancelledGCYieldClosure yield;
829
830 assert(task_queues()->is_empty(), "Should be empty");
831
832 ShenandoahPrecleanCompleteGCClosure complete_gc;
833 if (sh->has_forwarded_objects()) {
834 ShenandoahForwardedIsAliveClosure is_alive;
835 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(get_queue(0));
836 ResourceMark rm;
837 rp->preclean_discovered_references(&is_alive, &keep_alive,
838 &complete_gc, &yield,
839 NULL);
840 } else {
841 ShenandoahIsAliveClosure is_alive;
842 ShenandoahCMKeepAliveClosure keep_alive(get_queue(0));
843 ResourceMark rm;
844 rp->preclean_discovered_references(&is_alive, &keep_alive,
845 &complete_gc, &yield,
846 NULL);
847 }
848
849 assert(task_queues()->is_empty(), "Should be empty");
850 }
851
852 void ShenandoahConcurrentMark::cancel() {
853 // Clean up marking stacks.
854 ShenandoahObjToScanQueueSet* queues = task_queues();
855 queues->clear();
856
857 // Cancel SATB buffers.
858 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
859 }
860
861 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
862 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
863 return _task_queues->queue(worker_id);
864 }
865
866 void ShenandoahConcurrentMark::clear_queue(ShenandoahObjToScanQueue *q) {
867 q->set_empty();
868 q->overflow_stack()->clear();
869 q->clear_buffer();
870 }
871
872 template <bool CANCELLABLE>
873 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ParallelTaskTerminator *t, ReferenceProcessor *rp,
874 bool class_unload, bool update_refs, bool strdedup) {
875 ShenandoahObjToScanQueue* q = get_queue(w);
876
877 jushort* ld = get_liveness(w);
878 Copy::fill_to_bytes(ld, _heap->num_regions() * sizeof(jushort));
879
880 // TODO: We can clean up this if we figure out how to do templated oop closures that
881 // play nice with specialized_oop_iterators.
882 if (class_unload) {
883 if (update_refs) {
884 if (strdedup) {
885 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
886 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
887 } else {
888 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
889 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
890 }
891 } else {
892 if (strdedup) {
893 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
894 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
895 } else {
896 ShenandoahMarkRefsMetadataClosure cl(q, rp);
897 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
898 }
899 }
900 } else {
901 if (update_refs) {
902 if (strdedup) {
903 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
904 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
905 } else {
906 ShenandoahMarkUpdateRefsClosure cl(q, rp);
907 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
908 }
909 } else {
910 if (strdedup) {
911 ShenandoahMarkRefsDedupClosure cl(q, rp);
912 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
913 } else {
914 ShenandoahMarkRefsClosure cl(q, rp);
915 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
916 }
917 }
918 }
919
920
921 for (uint i = 0; i < _heap->num_regions(); i++) {
922 ShenandoahHeapRegion* r = _heap->get_region(i);
923 jushort live = ld[i];
924 if (live > 0) {
925 r->increase_live_data_gc_words(live);
926 }
927 }
928 }
929
930 template <class T, bool CANCELLABLE>
931 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator *terminator) {
932 uintx stride = ShenandoahMarkLoopStride;
933
934 ShenandoahHeap* heap = ShenandoahHeap::heap();
935 ShenandoahObjToScanQueueSet* queues = task_queues();
936 ShenandoahObjToScanQueue* q;
937 ShenandoahMarkTask t;
938
939 /*
940 * Process outstanding queues, if any.
941 *
942 * There can be more queues than workers. To deal with the imbalance, we claim
943 * extra queues first. Since marking can push new tasks into the queue associated
944 * with this worker id, we come back to process this queue in the normal loop.
945 */
946 assert(queues->get_reserved() == heap->workers()->active_workers(),
947 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
948
949 q = queues->claim_next();
950 while (q != NULL) {
951 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
952 ShenandoahCancelledTerminatorTerminator tt;
953 while (!terminator->offer_termination(&tt));
954 return;
955 }
956
957 for (uint i = 0; i < stride; i++) {
958 if (try_queue(q, t)) {
959 do_task<T>(q, cl, live_data, &t);
960 } else {
961 assert(q->is_empty(), "Must be empty");
962 q = queues->claim_next();
963 break;
964 }
965 }
966 }
967 q = get_queue(worker_id);
968
969 ShenandoahSATBBufferClosure drain_satb(q);
970 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
971
972 /*
973 * Normal marking loop:
974 */
975 while (true) {
976 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
977 ShenandoahCancelledTerminatorTerminator tt;
978 while (!terminator->offer_termination(&tt));
979 return;
980 }
981
982 while (satb_mq_set.completed_buffers_num() > 0) {
983 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
984 }
985
986 uint work = 0;
987 for (uint i = 0; i < stride; i++) {
988 if (try_queue(q, t) ||
989 queues->steal(worker_id, t)) {
990 do_task<T>(q, cl, live_data, &t);
991 work++;
992 } else {
993 break;
994 }
995 }
996
997 if (work == 0) {
998 // No work encountered in current stride, try to terminate.
999 // Need to leave the STS here otherwise it might block safepoints.
1000 SuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
1001 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
1002 if (terminator->offer_termination()) return;
1003 }
1004 }
1005 }
1006
1007 bool ShenandoahConcurrentMark::process_references() const {
1008 return _heap->process_references();
1009 }
1010
1011 bool ShenandoahConcurrentMark::unload_classes() const {
1012 return _heap->unload_classes();
1013 }
1014
1015 bool ShenandoahConcurrentMark::claim_codecache() {
1016 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1017 return _claimed_codecache.try_set();
1018 }
1019
1020 void ShenandoahConcurrentMark::clear_claim_codecache() {
1021 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1022 _claimed_codecache.unset();
1023 }
1024
1025 jushort* ShenandoahConcurrentMark::get_liveness(uint worker_id) {
1026 return _liveness_local[worker_id];
1027 }
1028