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