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