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 update_code_cache = true;
338 break;
339 default:
340 ShouldNotReachHere();
341 }
342
343 ShenandoahHeap* heap = ShenandoahHeap::heap();
344
345 ShenandoahGCPhase phase(root_phase);
346
347 #if defined(COMPILER2) || INCLUDE_JVMCI
348 DerivedPointerTable::clear();
349 #endif
350
351 uint nworkers = heap->workers()->active_workers();
352
353 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
354 ShenandoahUpdateRootsTask update_roots(&root_proc, update_code_cache);
355 heap->workers()->run_task(&update_roots);
356
357 #if defined(COMPILER2) || INCLUDE_JVMCI
358 DerivedPointerTable::update_pointers();
359 #endif
360 }
361
362 void ShenandoahConcurrentMark::initialize(uint workers) {
363 _heap = ShenandoahHeap::heap();
364
365 uint num_queues = MAX2(workers, 1U);
366
367 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
368
369 for (uint i = 0; i < num_queues; ++i) {
370 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
371 task_queue->initialize();
372 _task_queues->register_queue(i, task_queue);
373 }
374
375 size_t num_regions = ShenandoahHeap::heap()->num_regions();
376 _liveness_local = NEW_C_HEAP_ARRAY(jushort*, workers, mtGC);
377 for (uint worker = 0; worker < workers; worker++) {
378 _liveness_local[worker] = NEW_C_HEAP_ARRAY(jushort, num_regions, mtGC);
379 }
380 }
381
382 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp, bool update_refs) {
383 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
384 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
385 if (!unload_classes()) {
386 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
387 if (update_refs) {
388 ShenandoahMarkResolveRefsClosure cl(q, rp);
389 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
390 CodeCache::blobs_do(&blobs);
391 } else {
392 ShenandoahMarkRefsClosure cl(q, rp);
393 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
394 CodeCache::blobs_do(&blobs);
395 }
396 }
397 }
398 }
399
400 void ShenandoahConcurrentMark::mark_from_roots() {
401 ShenandoahHeap* sh = ShenandoahHeap::heap();
402 WorkGang* workers = sh->workers();
403 uint nworkers = workers->active_workers();
404
405 bool update_refs = sh->has_forwarded_objects();
406
407 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
408
409 if (process_references()) {
410 ReferenceProcessor* rp = sh->ref_processor();
411 rp->set_active_mt_degree(nworkers);
412
413 // enable ("weak") refs discovery
414 rp->enable_discovery(true /*verify_no_refs*/);
415 rp->setup_policy(sh->soft_ref_policy()->should_clear_all_soft_refs());
416 }
417
418 shenandoah_assert_rp_isalive_not_installed();
419 ShenandoahIsAliveSelector is_alive;
420 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), is_alive.is_alive_closure());
421
422 task_queues()->reserve(nworkers);
423
424 {
425 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
426 if (UseShenandoahOWST) {
427 ShenandoahTaskTerminator terminator(nworkers, task_queues());
428 ShenandoahConcurrentMarkingTask task(this, &terminator, update_refs);
429 workers->run_task(&task);
430 } else {
431 ParallelTaskTerminator terminator(nworkers, task_queues());
432 ShenandoahConcurrentMarkingTask task(this, &terminator, update_refs);
433 workers->run_task(&task);
434 }
435 }
436
437 assert(task_queues()->is_empty() || sh->cancelled_gc(), "Should be empty when not cancelled");
438 }
439
440 void ShenandoahConcurrentMark::finish_mark_from_roots() {
441 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
442
443 ShenandoahHeap* sh = ShenandoahHeap::heap();
444
445 shared_finish_mark_from_roots(/* full_gc = */ false);
446
447 if (sh->has_forwarded_objects()) {
448 update_roots(ShenandoahPhaseTimings::update_roots);
449 }
450 }
451
452 void ShenandoahConcurrentMark::shared_finish_mark_from_roots(bool full_gc) {
453 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
454
455 ShenandoahHeap* sh = ShenandoahHeap::heap();
456
457 uint nworkers = sh->workers()->active_workers();
458
459 // Finally mark everything else we've got in our queues during the previous steps.
460 // It does two different things for concurrent vs. mark-compact GC:
461 // - For concurrent GC, it starts with empty task queues, drains the remaining
462 // SATB buffers, and then completes the marking closure.
463 // - For mark-compact GC, it starts out with the task queues seeded by initial
464 // root scan, and completes the closure, thus marking through all live objects
465 // The implementation is the same, so it's shared here.
466 {
467 ShenandoahGCPhase phase(full_gc ?
468 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
469 ShenandoahPhaseTimings::finish_queues);
470 task_queues()->reserve(nworkers);
471
472 shenandoah_assert_rp_isalive_not_installed();
473 ShenandoahIsAliveSelector is_alive;
474 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), is_alive.is_alive_closure());
475
476 ShenandoahTerminationTracker termination_tracker(full_gc ?
477 ShenandoahPhaseTimings::full_gc_mark_termination :
478 ShenandoahPhaseTimings::termination);
479
480 StrongRootsScope scope(nworkers);
481 if (UseShenandoahOWST) {
482 ShenandoahTaskTerminator terminator(nworkers, task_queues());
483 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
484 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
485 sh->workers()->run_task(&task);
486 } else {
487 ParallelTaskTerminator terminator(nworkers, task_queues());
488 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
489 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
490 sh->workers()->run_task(&task);
491 }
492 }
493
494 assert(task_queues()->is_empty(), "Should be empty");
495
496 // When we're done marking everything, we process weak references.
497 if (process_references()) {
498 weak_refs_work(full_gc);
499 }
500
501 // And finally finish class unloading
502 if (unload_classes()) {
503 sh->unload_classes_and_cleanup_tables(full_gc);
504 }
505
506 assert(task_queues()->is_empty(), "Should be empty");
507 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
508 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
509 }
510
511 // Weak Reference Closures
512 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
513 uint _worker_id;
514 ParallelTaskTerminator* _terminator;
515 bool _reset_terminator;
516
517 public:
518 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ParallelTaskTerminator* t, bool reset_terminator = false):
519 _worker_id(worker_id),
520 _terminator(t),
521 _reset_terminator(reset_terminator) {
522 }
523
524 void do_void() {
525 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
526
527 ShenandoahHeap* sh = ShenandoahHeap::heap();
528 ShenandoahConcurrentMark* scm = sh->concurrentMark();
529 assert(scm->process_references(), "why else would we be here?");
530 ReferenceProcessor* rp = sh->ref_processor();
531
532 shenandoah_assert_rp_isalive_installed();
533
534 scm->mark_loop(_worker_id, _terminator, rp,
535 false, // not cancellable
536 scm->unload_classes(),
537 sh->has_forwarded_objects(),
538 false); // do not do strdedup
539
540 if (_reset_terminator) {
541 _terminator->reset_for_reuse();
542 }
543 }
544 };
545
546
547 class ShenandoahCMKeepAliveClosure : public OopClosure {
548 private:
549 ShenandoahObjToScanQueue* _queue;
550 ShenandoahHeap* _heap;
551 ShenandoahMarkingContext* const _mark_context;
552
553 template <class T>
554 inline void do_oop_work(T* p) {
555 ShenandoahConcurrentMark::mark_through_ref<T, NONE, false /* string dedup */>(p, _heap, _queue, _mark_context);
556 }
557
558 public:
559 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
560 _queue(q),
561 _heap(ShenandoahHeap::heap()),
562 _mark_context(_heap->next_marking_context()) {}
563
564 void do_oop(narrowOop* p) { do_oop_work(p); }
565 void do_oop(oop* p) { do_oop_work(p); }
566 };
567
568 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
569 private:
570 ShenandoahObjToScanQueue* _queue;
571 ShenandoahHeap* _heap;
572 ShenandoahMarkingContext* const _mark_context;
573
574 template <class T>
575 inline void do_oop_work(T* p) {
576 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, false /* string dedup */>(p, _heap, _queue, _mark_context);
577 }
578
579 public:
580 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
581 _queue(q),
582 _heap(ShenandoahHeap::heap()),
583 _mark_context(_heap->next_marking_context()) {}
584
585 void do_oop(narrowOop* p) { do_oop_work(p); }
586 void do_oop(oop* p) { do_oop_work(p); }
587 };
588
589 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
590
591 private:
592 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
593 ParallelTaskTerminator* _terminator;
594 public:
595
596 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
597 ParallelTaskTerminator* t) :
598 AbstractGangTask("Process reference objects in parallel"),
599 _proc_task(proc_task),
600 _terminator(t) {
601 }
602
603 void work(uint worker_id) {
604 ResourceMark rm;
605 HandleMark hm;
606 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
607 ShenandoahHeap* heap = ShenandoahHeap::heap();
608 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
609 if (heap->has_forwarded_objects()) {
610 ShenandoahForwardedIsAliveClosure is_alive;
611 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
612 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
613 } else {
614 ShenandoahIsAliveClosure is_alive;
615 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
616 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
617 }
618 }
619 };
620
621 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
622
623 private:
624 WorkGang* _workers;
625
626 public:
627
628 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
629 _workers(workers) {
630 }
631
632 // Executes a task using worker threads.
633 void execute(ProcessTask& task, uint ergo_workers) {
634 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
635
636 ShenandoahHeap* heap = ShenandoahHeap::heap();
637 ShenandoahConcurrentMark* cm = heap->concurrentMark();
638 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
639 ergo_workers,
640 /* do_check = */ false);
641 uint nworkers = _workers->active_workers();
642 cm->task_queues()->reserve(nworkers);
643 if (UseShenandoahOWST) {
644 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
645 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
646 if (nworkers == 1) {
647 proc_task_proxy.work(0);
648 } else {
649 _workers->run_task(&proc_task_proxy);
650 }
651 } else {
652 ParallelTaskTerminator terminator(nworkers, cm->task_queues());
653 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
654 if (nworkers == 1) {
655 proc_task_proxy.work(0);
656 } else {
657 _workers->run_task(&proc_task_proxy);
658 }
659 }
660 }
661 };
662
663
664 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
665 assert(process_references(), "sanity");
666
667 ShenandoahHeap* sh = ShenandoahHeap::heap();
668
669 ShenandoahPhaseTimings::Phase phase_root =
670 full_gc ?
671 ShenandoahPhaseTimings::full_gc_weakrefs :
672 ShenandoahPhaseTimings::weakrefs;
673
674 ShenandoahGCPhase phase(phase_root);
675
676 ReferenceProcessor* rp = sh->ref_processor();
677
678 // NOTE: We cannot shortcut on has_discovered_references() here, because
679 // we will miss marking JNI Weak refs then, see implementation in
680 // ReferenceProcessor::process_discovered_references.
681 weak_refs_work_doit(full_gc);
682
683 rp->verify_no_references_recorded();
684 assert(!rp->discovery_enabled(), "Post condition");
685
686 }
687
688 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
689 ShenandoahHeap* sh = ShenandoahHeap::heap();
690
691 ReferenceProcessor* rp = sh->ref_processor();
692
693 ShenandoahPhaseTimings::Phase phase_process =
694 full_gc ?
695 ShenandoahPhaseTimings::full_gc_weakrefs_process :
696 ShenandoahPhaseTimings::weakrefs_process;
697
698 ShenandoahPhaseTimings::Phase phase_process_termination =
699 full_gc ?
700 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
701 ShenandoahPhaseTimings::weakrefs_termination;
702
703 shenandoah_assert_rp_isalive_not_installed();
704 ShenandoahIsAliveSelector is_alive;
705 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
706
707 WorkGang* workers = sh->workers();
708 uint nworkers = workers->active_workers();
709
710 rp->setup_policy(sh->soft_ref_policy()->should_clear_all_soft_refs());
711 rp->set_active_mt_degree(nworkers);
712
713 assert(task_queues()->is_empty(), "Should be empty");
714
715 ShenandoahRefProcTaskExecutor executor(workers);
716
717 ReferenceProcessorPhaseTimes pt(sh->gc_timer(), rp->num_queues());
718
719 {
720 ShenandoahGCPhase phase(phase_process);
721 ShenandoahTerminationTracker phase_term(phase_process_termination);
722
723 // We don't use single-threaded closures, because we distinguish this
724 // in the executor. Assert that we should never actually get there.
725 ShouldNotReachHereBoolObjectClosure should_not_reach_here_is_alive;
726 ShouldNotReachHereOopClosure should_not_reach_here_keep_alive;
727 ShouldNotReachHereVoidClosure should_not_reach_here_complete;
728 rp->process_discovered_references(&should_not_reach_here_is_alive,
729 &should_not_reach_here_keep_alive,
730 &should_not_reach_here_complete,
731 &executor, &pt);
732
733 // Closures instantiated here are only needed for the single-threaded path in WeakProcessor.
734 // They share the queue 0 for tracking work, which simplifies implementation.
735 // TODO: As soon as WeakProcessor becomes MT-capable, these closures would become
736 // unnecessary, and could be removed.
737 uint serial_worker_id = 0;
738 ShenandoahPushWorkerQueuesScope scope(workers, task_queues(), 1, /* do_check = */ false);
739 ShenandoahForwardedIsAliveClosure is_alive;
740 if (sh->has_forwarded_objects()) {
741 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
742 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
743 } else {
744 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
745 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
746 }
747
748 pt.print_all_references();
749
750 assert(task_queues()->is_empty(), "Should be empty");
751 }
752 }
753
754 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
755 private:
756 ShenandoahHeap* const _heap;
757 public:
758 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
759 virtual bool should_return() { return _heap->cancelled_gc(); }
760 };
761
762 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
763 public:
764 void do_void() {
765 ShenandoahHeap* sh = ShenandoahHeap::heap();
766 ShenandoahConcurrentMark* scm = sh->concurrentMark();
767 assert(scm->process_references(), "why else would we be here?");
768 ParallelTaskTerminator terminator(1, scm->task_queues());
769
770 ReferenceProcessor* rp = sh->ref_processor();
771 shenandoah_assert_rp_isalive_installed();
772
773 scm->mark_loop(0, &terminator, rp,
774 false, // not cancellable
775 scm->unload_classes(),
776 sh->has_forwarded_objects(),
777 false); // do not do strdedup
778 }
779 };
780
781 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
782 private:
783 ShenandoahObjToScanQueue* _queue;
784 ShenandoahHeap* _heap;
785 ShenandoahMarkingContext* const _mark_context;
786
787 template <class T>
788 inline void do_oop_work(T* p) {
789 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, false /* string dedup */>(p, _heap, _queue, _mark_context);
790 }
791
792 public:
793 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
794 _queue(q),
795 _heap(ShenandoahHeap::heap()),
796 _mark_context(_heap->next_marking_context()) {}
797
798 void do_oop(narrowOop* p) { do_oop_work(p); }
799 void do_oop(oop* p) { do_oop_work(p); }
800 };
801
802 void ShenandoahConcurrentMark::preclean_weak_refs() {
803 // Pre-cleaning weak references before diving into STW makes sense at the
804 // end of concurrent mark. This will filter out the references which referents
805 // are alive. Note that ReferenceProcessor already filters out these on reference
806 // discovery, and the bulk of work is done here. This phase processes leftovers
807 // that missed the initial filtering, i.e. when referent was marked alive after
808 // reference was discovered by RP.
809
810 assert(process_references(), "sanity");
811
812 ShenandoahHeap* sh = ShenandoahHeap::heap();
813 ReferenceProcessor* rp = sh->ref_processor();
814
815 // Shortcut if no references were discovered to avoid winding up threads.
816 if (!rp->has_discovered_references()) {
817 return;
818 }
819
820 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
821
822 shenandoah_assert_rp_isalive_not_installed();
823 ShenandoahIsAliveSelector is_alive;
824 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
825
826 // Interrupt on cancelled GC
827 ShenandoahCancelledGCYieldClosure yield;
828
829 assert(task_queues()->is_empty(), "Should be empty");
830
831 ShenandoahPrecleanCompleteGCClosure complete_gc;
832 if (sh->has_forwarded_objects()) {
833 ShenandoahForwardedIsAliveClosure is_alive;
834 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(get_queue(0));
835 ResourceMark rm;
836 rp->preclean_discovered_references(&is_alive, &keep_alive,
837 &complete_gc, &yield,
838 NULL);
839 } else {
840 ShenandoahIsAliveClosure is_alive;
841 ShenandoahCMKeepAliveClosure keep_alive(get_queue(0));
842 ResourceMark rm;
843 rp->preclean_discovered_references(&is_alive, &keep_alive,
844 &complete_gc, &yield,
845 NULL);
846 }
847
848 assert(task_queues()->is_empty(), "Should be empty");
849 }
850
851 void ShenandoahConcurrentMark::cancel() {
852 // Clean up marking stacks.
853 ShenandoahObjToScanQueueSet* queues = task_queues();
854 queues->clear();
855
856 // Cancel SATB buffers.
857 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
858 }
859
860 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
861 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
862 return _task_queues->queue(worker_id);
863 }
864
865 void ShenandoahConcurrentMark::clear_queue(ShenandoahObjToScanQueue *q) {
866 q->set_empty();
867 q->overflow_stack()->clear();
868 q->clear_buffer();
869 }
870
871 template <bool CANCELLABLE>
872 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ParallelTaskTerminator *t, ReferenceProcessor *rp,
873 bool class_unload, bool update_refs, bool strdedup) {
874 ShenandoahObjToScanQueue* q = get_queue(w);
875
876 jushort* ld = get_liveness(w);
877 Copy::fill_to_bytes(ld, _heap->num_regions() * sizeof(jushort));
878
879 // TODO: We can clean up this if we figure out how to do templated oop closures that
880 // play nice with specialized_oop_iterators.
881 if (class_unload) {
882 if (update_refs) {
883 if (strdedup) {
884 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
885 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
886 } else {
887 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
888 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
889 }
890 } else {
891 if (strdedup) {
892 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
893 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
894 } else {
895 ShenandoahMarkRefsMetadataClosure cl(q, rp);
896 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
897 }
898 }
899 } else {
900 if (update_refs) {
901 if (strdedup) {
902 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
903 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
904 } else {
905 ShenandoahMarkUpdateRefsClosure cl(q, rp);
906 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
907 }
908 } else {
909 if (strdedup) {
910 ShenandoahMarkRefsDedupClosure cl(q, rp);
911 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
912 } else {
913 ShenandoahMarkRefsClosure cl(q, rp);
914 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
915 }
916 }
917 }
918
919
920 for (uint i = 0; i < _heap->num_regions(); i++) {
921 ShenandoahHeapRegion* r = _heap->get_region(i);
922 jushort live = ld[i];
923 if (live > 0) {
924 r->increase_live_data_gc_words(live);
925 }
926 }
927 }
928
929 template <class T, bool CANCELLABLE>
930 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator *terminator) {
931 uintx stride = ShenandoahMarkLoopStride;
932
933 ShenandoahHeap* heap = ShenandoahHeap::heap();
934 ShenandoahObjToScanQueueSet* queues = task_queues();
935 ShenandoahObjToScanQueue* q;
936 ShenandoahMarkTask t;
937
938 /*
939 * Process outstanding queues, if any.
940 *
941 * There can be more queues than workers. To deal with the imbalance, we claim
942 * extra queues first. Since marking can push new tasks into the queue associated
943 * with this worker id, we come back to process this queue in the normal loop.
944 */
945 assert(queues->get_reserved() == heap->workers()->active_workers(),
946 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
947
948 q = queues->claim_next();
949 while (q != NULL) {
950 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
951 ShenandoahCancelledTerminatorTerminator tt;
952 while (!terminator->offer_termination(&tt));
953 return;
954 }
955
956 for (uint i = 0; i < stride; i++) {
957 if (try_queue(q, t)) {
958 do_task<T>(q, cl, live_data, &t);
959 } else {
960 assert(q->is_empty(), "Must be empty");
961 q = queues->claim_next();
962 break;
963 }
964 }
965 }
966 q = get_queue(worker_id);
967
968 ShenandoahSATBBufferClosure drain_satb(q);
969 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
970
971 /*
972 * Normal marking loop:
973 */
974 while (true) {
975 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
976 ShenandoahCancelledTerminatorTerminator tt;
977 while (!terminator->offer_termination(&tt));
978 return;
979 }
980
981 while (satb_mq_set.completed_buffers_num() > 0) {
982 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
983 }
984
985 uint work = 0;
986 for (uint i = 0; i < stride; i++) {
987 if (try_queue(q, t) ||
988 queues->steal(worker_id, t)) {
989 do_task<T>(q, cl, live_data, &t);
990 work++;
991 } else {
992 break;
993 }
994 }
995
996 if (work == 0) {
997 // No work encountered in current stride, try to terminate.
998 // Need to leave the STS here otherwise it might block safepoints.
999 SuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
1000 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
1001 if (terminator->offer_termination()) return;
1002 }
1003 }
1004 }
1005
1006 bool ShenandoahConcurrentMark::process_references() const {
1007 return _heap->process_references();
1008 }
1009
1010 bool ShenandoahConcurrentMark::unload_classes() const {
1011 return _heap->unload_classes();
1012 }
1013
1014 bool ShenandoahConcurrentMark::claim_codecache() {
1015 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1016 return _claimed_codecache.try_set();
1017 }
1018
1019 void ShenandoahConcurrentMark::clear_claim_codecache() {
1020 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1021 _claimed_codecache.unset();
1022 }
1023
1024 jushort* ShenandoahConcurrentMark::get_liveness(uint worker_id) {
1025 return _liveness_local[worker_id];
1026 }
1027