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/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 #include "gc/shared/weakProcessor.hpp"
46
47 #include "memory/iterator.inline.hpp"
48 #include "memory/metaspace.hpp"
49 #include "memory/resourceArea.hpp"
50 #include "oops/oop.inline.hpp"
51
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 ShenandoahConcMarkSATBBufferClosure* _satb_cl;
179 int _thread_parity;
180
181 public:
182 ShenandoahSATBThreadsClosure(ShenandoahConcMarkSATBBufferClosure* satb_cl) :
183 _satb_cl(satb_cl),
184 _thread_parity(Threads::thread_claim_parity()) {}
185
186 void do_thread(Thread* thread) {
187 if (thread->is_Java_thread()) {
188 if (thread->claim_oops_do(true, _thread_parity)) {
189 JavaThread* jt = (JavaThread*)thread;
190 ShenandoahThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(_satb_cl);
191 }
192 } else if (thread->is_VM_thread()) {
193 if (thread->claim_oops_do(true, _thread_parity)) {
194 ShenandoahBarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(_satb_cl);
195 }
196 }
197 }
198 };
199
200 class ShenandoahFinalMarkingTask : public AbstractGangTask {
201 private:
202 ShenandoahConcurrentMark* _cm;
203 ShenandoahTaskTerminator* _terminator;
204 bool _dedup_string;
205
206 public:
207 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) :
208 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
209 }
210
211 void work(uint worker_id) {
212 ShenandoahHeap* heap = ShenandoahHeap::heap();
213
214 ShenandoahParallelWorkerSession worker_session(worker_id);
215 // First drain remaining SATB buffers.
216 // Notice that this is not strictly necessary for mark-compact. But since
217 // it requires a StrongRootsScope around the task, we need to claim the
218 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
219 // full-gc.
220 {
221 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
222 ShenandoahConcMarkSATBBufferClosure cl(q);
223 ShenandoahSATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
224 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
225 ShenandoahSATBThreadsClosure tc(&cl);
226 Threads::threads_do(&tc);
227 }
228
229 ReferenceProcessor* rp;
230 if (heap->process_references()) {
231 rp = heap->ref_processor();
232 shenandoah_assert_rp_isalive_installed();
233 } else {
234 rp = NULL;
235 }
236
237 if (heap->is_degenerated_gc_in_progress()) {
238 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
239 // let's check here.
240 _cm->concurrent_scan_code_roots(worker_id, rp);
241 }
242
243 _cm->mark_loop(worker_id, _terminator, rp,
244 false, // not cancellable
245 _dedup_string);
246
247 assert(_cm->task_queues()->is_empty(), "Should be empty");
248 }
249 };
250
251 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
252 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
253 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
254
255 ShenandoahHeap* heap = ShenandoahHeap::heap();
256
257 ShenandoahGCPhase phase(root_phase);
258
259 WorkGang* workers = heap->workers();
260 uint nworkers = workers->active_workers();
261
262 assert(nworkers <= task_queues()->size(), "Just check");
263
264 ShenandoahAllRootScanner root_proc(nworkers, root_phase);
265 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
266 task_queues()->reserve(nworkers);
267
268 if (heap->has_forwarded_objects()) {
269 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references());
270 workers->run_task(&mark_roots);
271 } else {
272 // No need to update references, which means the heap is stable.
273 // Can save time not walking through forwarding pointers.
274 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references());
275 workers->run_task(&mark_roots);
276 }
277
278 if (ShenandoahConcurrentScanCodeRoots) {
279 clear_claim_codecache();
280 }
281 }
282
283 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
284 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
285
286 bool update_code_cache = true; // initialize to safer value
287 switch (root_phase) {
288 case ShenandoahPhaseTimings::update_roots:
289 case ShenandoahPhaseTimings::final_update_refs_roots:
290 update_code_cache = false;
291 break;
292 case ShenandoahPhaseTimings::full_gc_roots:
293 case ShenandoahPhaseTimings::degen_gc_update_roots:
294 update_code_cache = true;
295 break;
296 default:
297 ShouldNotReachHere();
298 }
299
300 ShenandoahGCPhase phase(root_phase);
301
302 #if COMPILER2_OR_JVMCI
303 DerivedPointerTable::clear();
304 #endif
305
306 uint nworkers = _heap->workers()->active_workers();
307
308 ShenandoahRootUpdater root_updater(nworkers, root_phase, update_code_cache);
309 ShenandoahUpdateRootsTask update_roots(&root_updater);
310 _heap->workers()->run_task(&update_roots);
311
312 #if COMPILER2_OR_JVMCI
313 DerivedPointerTable::update_pointers();
314 #endif
315 }
316
317 class ShenandoahUpdateThreadRootsTask : public AbstractGangTask {
318 private:
319 ShenandoahThreadRoots _thread_roots;
320 ShenandoahPhaseTimings::Phase _phase;
321 public:
322 ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) :
323 AbstractGangTask("Shenandoah Update Thread Roots"),
324 _thread_roots(is_par),
325 _phase(phase) {
326 ShenandoahHeap::heap()->phase_timings()->record_workers_start(_phase);
327 }
328
329 ~ShenandoahUpdateThreadRootsTask() {
330 ShenandoahHeap::heap()->phase_timings()->record_workers_end(_phase);
331 }
332 void work(uint worker_id) {
333 ShenandoahUpdateRefsClosure cl;
334 _thread_roots.oops_do(&cl, NULL, worker_id);
335 }
336 };
337
338 void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) {
339 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
340
341 ShenandoahGCPhase phase(root_phase);
342
343 #if COMPILER2_OR_JVMCI
344 DerivedPointerTable::clear();
345 #endif
346
347 WorkGang* workers = _heap->workers();
348 bool is_par = workers->active_workers() > 1;
349
350 ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
351 workers->run_task(&task);
352
353 #if COMPILER2_OR_JVMCI
354 DerivedPointerTable::update_pointers();
355 #endif
356 }
357
358 void ShenandoahConcurrentMark::initialize(uint workers) {
359 _heap = ShenandoahHeap::heap();
360
361 uint num_queues = MAX2(workers, 1U);
362
363 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
364
365 for (uint i = 0; i < num_queues; ++i) {
366 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
367 task_queue->initialize();
368 _task_queues->register_queue(i, task_queue);
369 }
370
371 ShenandoahBarrierSet::satb_mark_queue_set().set_buffer_size(ShenandoahSATBBufferSize);
372 }
373
374 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
375 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
376 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
377 if (!_heap->unload_classes()) {
378 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
379 // TODO: We can not honor StringDeduplication here, due to lock ranking
380 // inversion. So, we may miss some deduplication candidates.
381 if (_heap->has_forwarded_objects()) {
382 ShenandoahMarkResolveRefsClosure cl(q, rp);
383 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
384 CodeCache::blobs_do(&blobs);
385 } else {
386 ShenandoahMarkRefsClosure cl(q, rp);
387 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
388 CodeCache::blobs_do(&blobs);
389 }
390 }
391 }
392 }
393
394 void ShenandoahConcurrentMark::mark_from_roots() {
395 WorkGang* workers = _heap->workers();
396 uint nworkers = workers->active_workers();
397
398 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
399
400 if (_heap->process_references()) {
401 ReferenceProcessor* rp = _heap->ref_processor();
402 rp->set_active_mt_degree(nworkers);
403
404 // enable ("weak") refs discovery
405 rp->enable_discovery(true /*verify_no_refs*/);
406 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
407 }
408
409 shenandoah_assert_rp_isalive_not_installed();
410 ShenandoahIsAliveSelector is_alive;
411 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
412
413 task_queues()->reserve(nworkers);
414
415 {
416 ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
417 ShenandoahTaskTerminator terminator(nworkers, task_queues());
418 ShenandoahConcurrentMarkingTask task(this, &terminator);
419 workers->run_task(&task);
420 }
421
422 assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
423 }
424
425 void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
426 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
427
428 uint nworkers = _heap->workers()->active_workers();
429
430 // Finally mark everything else we've got in our queues during the previous steps.
431 // It does two different things for concurrent vs. mark-compact GC:
432 // - For concurrent GC, it starts with empty task queues, drains the remaining
433 // SATB buffers, and then completes the marking closure.
434 // - For mark-compact GC, it starts out with the task queues seeded by initial
435 // root scan, and completes the closure, thus marking through all live objects
436 // The implementation is the same, so it's shared here.
437 {
438 ShenandoahGCPhase phase(full_gc ?
439 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
440 ShenandoahPhaseTimings::finish_queues);
441 task_queues()->reserve(nworkers);
442
443 shenandoah_assert_rp_isalive_not_installed();
444 ShenandoahIsAliveSelector is_alive;
445 ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
446
447 ShenandoahTerminationTracker termination_tracker(full_gc ?
448 ShenandoahPhaseTimings::full_gc_mark_termination :
449 ShenandoahPhaseTimings::termination);
450
451 StrongRootsScope scope(nworkers);
452 ShenandoahTaskTerminator terminator(nworkers, task_queues());
453 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
454 _heap->workers()->run_task(&task);
455 }
456
457 assert(task_queues()->is_empty(), "Should be empty");
458
459 // When we're done marking everything, we process weak references.
460 if (_heap->process_references()) {
461 weak_refs_work(full_gc);
462 }
463
464 weak_roots_work();
465
466 // And finally finish class unloading
467 if (_heap->unload_classes()) {
468 _heap->unload_classes_and_cleanup_tables(full_gc);
469 } else {
470 ShenandoahIsAliveSelector alive;
471 StringTable::unlink(alive.is_alive_closure());
472 }
473 if (ShenandoahStringDedup::is_enabled()) {
474 ShenandoahIsAliveSelector alive;
475 BoolObjectClosure* is_alive = alive.is_alive_closure();
476 ShenandoahStringDedup::unlink_or_oops_do(is_alive, NULL, false);
477 }
478 assert(task_queues()->is_empty(), "Should be empty");
479 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
480 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
481
482 // Resize Metaspace
483 MetaspaceGC::compute_new_size();
484 }
485
486 // Weak Reference Closures
487 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
488 uint _worker_id;
489 ShenandoahTaskTerminator* _terminator;
490 bool _reset_terminator;
491
492 public:
493 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false):
494 _worker_id(worker_id),
495 _terminator(t),
496 _reset_terminator(reset_terminator) {
497 }
498
499 void do_void() {
500 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
501
502 ShenandoahHeap* sh = ShenandoahHeap::heap();
503 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
504 assert(sh->process_references(), "why else would we be here?");
505 ReferenceProcessor* rp = sh->ref_processor();
506
507 shenandoah_assert_rp_isalive_installed();
508
509 scm->mark_loop(_worker_id, _terminator, rp,
510 false, // not cancellable
511 false); // do not do strdedup
512
513 if (_reset_terminator) {
514 _terminator->reset_for_reuse();
515 }
516 }
517 };
518
519 class ShenandoahCMKeepAliveClosure : public OopClosure {
520 private:
521 ShenandoahObjToScanQueue* _queue;
522 ShenandoahHeap* _heap;
523 ShenandoahMarkingContext* const _mark_context;
524
525 template <class T>
526 inline void do_oop_work(T* p) {
527 ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
528 }
529
530 public:
531 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
532 _queue(q),
533 _heap(ShenandoahHeap::heap()),
534 _mark_context(_heap->marking_context()) {}
535
536 void do_oop(narrowOop* p) { do_oop_work(p); }
537 void do_oop(oop* p) { do_oop_work(p); }
538 };
539
540 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
541 private:
542 ShenandoahObjToScanQueue* _queue;
543 ShenandoahHeap* _heap;
544 ShenandoahMarkingContext* const _mark_context;
545
546 template <class T>
547 inline void do_oop_work(T* p) {
548 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
549 }
550
551 public:
552 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
553 _queue(q),
554 _heap(ShenandoahHeap::heap()),
555 _mark_context(_heap->marking_context()) {}
556
557 void do_oop(narrowOop* p) { do_oop_work(p); }
558 void do_oop(oop* p) { do_oop_work(p); }
559 };
560
561 class ShenandoahWeakUpdateClosure : public OopClosure {
562 private:
563 ShenandoahHeap* const _heap;
564
565 template <class T>
566 inline void do_oop_work(T* p) {
567 oop o = _heap->maybe_update_with_forwarded(p);
568 shenandoah_assert_marked_except(p, o, o == NULL);
569 }
570
571 public:
572 ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
573
574 void do_oop(narrowOop* p) { do_oop_work(p); }
575 void do_oop(oop* p) { do_oop_work(p); }
576 };
577
578 class ShenandoahWeakAssertNotForwardedClosure : public OopClosure {
579 private:
580 template <class T>
581 inline void do_oop_work(T* p) {
582 #ifdef ASSERT
583 T o = RawAccess<>::oop_load(p);
584 if (!CompressedOops::is_null(o)) {
585 oop obj = CompressedOops::decode_not_null(o);
586 shenandoah_assert_not_forwarded(p, obj);
587 }
588 #endif
589 }
590
591 public:
592 ShenandoahWeakAssertNotForwardedClosure() {}
593
594 void do_oop(narrowOop* p) { do_oop_work(p); }
595 void do_oop(oop* p) { do_oop_work(p); }
596 };
597
598 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
599 private:
600 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
601 ShenandoahTaskTerminator* _terminator;
602
603 public:
604 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
605 ShenandoahTaskTerminator* t) :
606 AbstractGangTask("Process reference objects in parallel"),
607 _proc_task(proc_task),
608 _terminator(t) {
609 }
610
611 void work(uint worker_id) {
612 ResourceMark rm;
613 HandleMark hm;
614 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
615 ShenandoahHeap* heap = ShenandoahHeap::heap();
616 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
617 if (heap->has_forwarded_objects()) {
618 ShenandoahForwardedIsAliveClosure is_alive;
619 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
620 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
621 } else {
622 ShenandoahIsAliveClosure is_alive;
623 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
624 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
625 }
626 }
627 };
628
629 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
630 private:
631 WorkGang* _workers;
632
633 public:
634 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
635 _workers(workers) {
636 }
637
638 // Executes a task using worker threads.
639 void execute(ProcessTask& task, uint ergo_workers) {
640 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
641
642 ShenandoahHeap* heap = ShenandoahHeap::heap();
643 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
644 ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
645 ergo_workers,
646 /* do_check = */ false);
647 uint nworkers = _workers->active_workers();
648 cm->task_queues()->reserve(nworkers);
649 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
650 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
651 _workers->run_task(&proc_task_proxy);
652 }
653 };
654
655 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
656 assert(_heap->process_references(), "sanity");
657
658 ShenandoahPhaseTimings::Phase phase_root =
659 full_gc ?
660 ShenandoahPhaseTimings::full_gc_weakrefs :
661 ShenandoahPhaseTimings::weakrefs;
662
663 ShenandoahGCPhase phase(phase_root);
664
665 ReferenceProcessor* rp = _heap->ref_processor();
666
667 // NOTE: We cannot shortcut on has_discovered_references() here, because
668 // we will miss marking JNI Weak refs then, see implementation in
669 // ReferenceProcessor::process_discovered_references.
670 weak_refs_work_doit(full_gc);
671
672 rp->verify_no_references_recorded();
673 assert(!rp->discovery_enabled(), "Post condition");
674
675 }
676
677 // Process leftover weak oops: update them, if needed or assert they do not
678 // need updating otherwise.
679 // Weak processor API requires us to visit the oops, even if we are not doing
680 // anything to them.
681 void ShenandoahConcurrentMark::weak_roots_work() {
682 OopClosure* keep_alive = &do_nothing_cl;
683 #ifdef ASSERT
684 ShenandoahWeakAssertNotForwardedClosure verify_cl;
685 keep_alive = &verify_cl;
686 #endif
687 ShenandoahIsAliveClosure is_alive;
688 WeakProcessor::weak_oops_do(&is_alive, keep_alive);
689 }
690
691 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
692 ReferenceProcessor* rp = _heap->ref_processor();
693
694 ShenandoahPhaseTimings::Phase phase_process =
695 full_gc ?
696 ShenandoahPhaseTimings::full_gc_weakrefs_process :
697 ShenandoahPhaseTimings::weakrefs_process;
698
699 ShenandoahPhaseTimings::Phase phase_process_termination =
700 full_gc ?
701 ShenandoahPhaseTimings::full_gc_weakrefs_termination :
702 ShenandoahPhaseTimings::weakrefs_termination;
703
704 shenandoah_assert_rp_isalive_not_installed();
705 ShenandoahIsAliveSelector is_alive;
706 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
707
708 WorkGang* workers = _heap->workers();
709 uint nworkers = workers->active_workers();
710
711 rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
712 rp->set_active_mt_degree(nworkers);
713
714 assert(task_queues()->is_empty(), "Should be empty");
715
716 // complete_gc and keep_alive closures instantiated here are only needed for
717 // single-threaded path in RP. They share the queue 0 for tracking work, which
718 // simplifies implementation. Since RP may decide to call complete_gc several
719 // times, we need to be able to reuse the terminator.
720 uint serial_worker_id = 0;
721 ShenandoahTaskTerminator terminator(1, task_queues());
722 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
723
724 ShenandoahRefProcTaskExecutor executor(workers);
725
726 ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
727
728 {
729 ShenandoahGCPhase phase(phase_process);
730 ShenandoahTerminationTracker phase_term(phase_process_termination);
731
732 if (_heap->has_forwarded_objects()) {
733 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
734 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
735 &complete_gc, &executor,
736 &pt);
737
738 } else {
739 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
740 rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
741 &complete_gc, &executor,
742 &pt);
743
744 }
745
746 pt.print_all_references();
747
748 assert(task_queues()->is_empty(), "Should be empty");
749 }
750 }
751
752 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
753 private:
754 ShenandoahHeap* const _heap;
755 public:
756 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
757 virtual bool should_return() { return _heap->cancelled_gc(); }
758 };
759
760 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
761 public:
762 void do_void() {
763 ShenandoahHeap* sh = ShenandoahHeap::heap();
764 ShenandoahConcurrentMark* scm = sh->concurrent_mark();
765 assert(sh->process_references(), "why else would we be here?");
766 ShenandoahTaskTerminator terminator(1, scm->task_queues());
767
768 ReferenceProcessor* rp = sh->ref_processor();
769 shenandoah_assert_rp_isalive_installed();
770
771 scm->mark_loop(0, &terminator, rp,
772 false, // not cancellable
773 false); // do not do strdedup
774 }
775 };
776
777 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
778 private:
779 ShenandoahObjToScanQueue* _queue;
780 ShenandoahHeap* _heap;
781 ShenandoahMarkingContext* const _mark_context;
782
783 template <class T>
784 inline void do_oop_work(T* p) {
785 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context);
786 }
787
788 public:
789 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
790 _queue(q),
791 _heap(ShenandoahHeap::heap()),
792 _mark_context(_heap->marking_context()) {}
793
794 void do_oop(narrowOop* p) { do_oop_work(p); }
795 void do_oop(oop* p) { do_oop_work(p); }
796 };
797
798 class ShenandoahPrecleanTask : public AbstractGangTask {
799 private:
800 ReferenceProcessor* _rp;
801
802 public:
803 ShenandoahPrecleanTask(ReferenceProcessor* rp) :
804 AbstractGangTask("Precleaning task"),
805 _rp(rp) {}
806
807 void work(uint worker_id) {
808 assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
809 ShenandoahParallelWorkerSession worker_session(worker_id);
810
811 ShenandoahHeap* sh = ShenandoahHeap::heap();
812
813 ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
814
815 ShenandoahCancelledGCYieldClosure yield;
816 ShenandoahPrecleanCompleteGCClosure complete_gc;
817
818 if (sh->has_forwarded_objects()) {
819 ShenandoahForwardedIsAliveClosure is_alive;
820 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q);
821 ResourceMark rm;
822 _rp->preclean_discovered_references(&is_alive, &keep_alive,
823 &complete_gc, &yield,
824 NULL);
825 } else {
826 ShenandoahIsAliveClosure is_alive;
827 ShenandoahCMKeepAliveClosure keep_alive(q);
828 ResourceMark rm;
829 _rp->preclean_discovered_references(&is_alive, &keep_alive,
830 &complete_gc, &yield,
831 NULL);
832 }
833 }
834 };
835
836 void ShenandoahConcurrentMark::preclean_weak_refs() {
837 // Pre-cleaning weak references before diving into STW makes sense at the
838 // end of concurrent mark. This will filter out the references which referents
839 // are alive. Note that ReferenceProcessor already filters out these on reference
840 // discovery, and the bulk of work is done here. This phase processes leftovers
841 // that missed the initial filtering, i.e. when referent was marked alive after
842 // reference was discovered by RP.
843
844 assert(_heap->process_references(), "sanity");
845
846 // Shortcut if no references were discovered to avoid winding up threads.
847 ReferenceProcessor* rp = _heap->ref_processor();
848 if (!rp->has_discovered_references()) {
849 return;
850 }
851
852 assert(task_queues()->is_empty(), "Should be empty");
853
854 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
855
856 shenandoah_assert_rp_isalive_not_installed();
857 ShenandoahIsAliveSelector is_alive;
858 ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
859
860 // Execute precleaning in the worker thread: it will give us GCLABs, String dedup
861 // queues and other goodies. When upstream ReferenceProcessor starts supporting
862 // parallel precleans, we can extend this to more threads.
863 WorkGang* workers = _heap->workers();
864 uint nworkers = workers->active_workers();
865 assert(nworkers == 1, "This code uses only a single worker");
866 task_queues()->reserve(nworkers);
867
868 ShenandoahPrecleanTask task(rp);
869 workers->run_task(&task);
870
871 assert(task_queues()->is_empty(), "Should be empty");
872 }
873
874 void ShenandoahConcurrentMark::cancel() {
875 // Clean up marking stacks.
876 ShenandoahObjToScanQueueSet* queues = task_queues();
877 queues->clear();
878
879 // Cancel SATB buffers.
880 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
881 }
882
883 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
884 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
885 return _task_queues->queue(worker_id);
886 }
887
888 template <bool CANCELLABLE>
889 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp,
890 bool strdedup) {
891 ShenandoahObjToScanQueue* q = get_queue(w);
892
893 jushort* ld = _heap->get_liveness_cache(w);
894
895 // TODO: We can clean up this if we figure out how to do templated oop closures that
896 // play nice with specialized_oop_iterators.
897 if (_heap->unload_classes()) {
898 if (_heap->has_forwarded_objects()) {
899 if (strdedup) {
900 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
901 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
902 } else {
903 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
904 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
905 }
906 } else {
907 if (strdedup) {
908 ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
909 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
910 } else {
911 ShenandoahMarkRefsMetadataClosure cl(q, rp);
912 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
913 }
914 }
915 } else {
916 if (_heap->has_forwarded_objects()) {
917 if (strdedup) {
918 ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
919 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
920 } else {
921 ShenandoahMarkUpdateRefsClosure cl(q, rp);
922 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
923 }
924 } else {
925 if (strdedup) {
926 ShenandoahMarkRefsDedupClosure cl(q, rp);
927 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
928 } else {
929 ShenandoahMarkRefsClosure cl(q, rp);
930 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
931 }
932 }
933 }
934
935 _heap->flush_liveness_cache(w);
936 }
937
938 template <class T, bool CANCELLABLE>
939 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) {
940 int seed = 17;
941 uintx stride = ShenandoahMarkLoopStride;
942
943 ShenandoahHeap* heap = ShenandoahHeap::heap();
944 ShenandoahObjToScanQueueSet* queues = task_queues();
945 ShenandoahObjToScanQueue* q;
946 ShenandoahMarkTask t;
947
948 /*
949 * Process outstanding queues, if any.
950 *
951 * There can be more queues than workers. To deal with the imbalance, we claim
952 * extra queues first. Since marking can push new tasks into the queue associated
953 * with this worker id, we come back to process this queue in the normal loop.
954 */
955 assert(queues->get_reserved() == heap->workers()->active_workers(),
956 "Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
957
958 q = queues->claim_next();
959 while (q != NULL) {
960 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
961 return;
962 }
963
964 for (uint i = 0; i < stride; i++) {
965 if (q->pop(t)) {
966 do_task<T>(q, cl, live_data, &t);
967 } else {
968 assert(q->is_empty(), "Must be empty");
969 q = queues->claim_next();
970 break;
971 }
972 }
973 }
974 q = get_queue(worker_id);
975
976 ShenandoahConcMarkSATBBufferClosure drain_satb(q);
977 ShenandoahSATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
978
979 /*
980 * Normal marking loop:
981 */
982 while (true) {
983 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
984 return;
985 }
986
987 while (satb_mq_set.completed_buffers_num() > 0) {
988 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
989 }
990
991 uint work = 0;
992 for (uint i = 0; i < stride; i++) {
993 if (q->pop(t) ||
994 queues->steal(worker_id, &seed, t)) {
995 do_task<T>(q, cl, live_data, &t);
996 work++;
997 } else {
998 break;
999 }
1000 }
1001
1002 if (work == 0) {
1003 // No work encountered in current stride, try to terminate.
1004 // Need to leave the STS here otherwise it might block safepoints.
1005 ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
1006 ShenandoahTerminationTimingsTracker term_tracker(worker_id);
1007 ShenandoahTerminatorTerminator tt(heap);
1008 if (terminator->offer_termination(&tt)) return;
1009 }
1010 }
1011 }
1012
1013 bool ShenandoahConcurrentMark::claim_codecache() {
1014 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1015 return _claimed_codecache.try_set();
1016 }
1017
1018 void ShenandoahConcurrentMark::clear_claim_codecache() {
1019 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1020 _claimed_codecache.unset();
1021 }