1 /*
2 * Copyright (c) 2013, 2017, Red Hat, Inc. and/or its affiliates.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25 #include "classfile/stringTable.hpp"
26 #include "gc/shared/gcTimer.hpp"
27 #include "gc/shared/parallelCleaning.hpp"
28 #include "gc/shared/referenceProcessor.hpp"
29 #include "gc/shared/strongRootsScope.hpp"
30 #include "gc/shared/suspendibleThreadSet.hpp"
31 #include "gc/shenandoah/brooksPointer.hpp"
32 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
33 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
34 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
35 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
36 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
37 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
38 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
39 #include "gc/shenandoah/shenandoah_specialized_oop_closures.hpp"
40 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
41 #include "gc/shenandoah/shenandoahUtils.hpp"
42 #include "gc/shared/weakProcessor.hpp"
43 #include "code/codeCache.hpp"
44 #include "classfile/symbolTable.hpp"
45 #include "classfile/systemDictionary.hpp"
46 #include "memory/iterator.inline.hpp"
47 #include "oops/oop.inline.hpp"
48 #include "gc/shared/taskqueue.inline.hpp"
49 #include "logging/logStream.hpp"
50
51 template<UpdateRefsMode UPDATE_REFS>
52 class ShenandoahInitMarkRootsClosure : public OopClosure {
53 private:
54 ShenandoahObjToScanQueue* _queue;
55 ShenandoahHeap* _heap;
56
57 template <class T>
58 inline void do_oop_nv(T* p) {
59 ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, false /* string dedup */>(p, _heap, _queue);
60 }
61
62 public:
63 ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) :
64 _queue(q), _heap(ShenandoahHeap::heap()) {};
65
66 void do_oop(narrowOop* p) { do_oop_nv(p); }
67 void do_oop(oop* p) { do_oop_nv(p); }
68 };
69
70 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) :
71 MetadataAwareOopClosure(rp),
72 _queue(q),
73 _dedup_queue(NULL),
74 _heap(ShenandoahHeap::heap())
75 { }
76
77
78 ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ShenandoahStrDedupQueue* dq, ReferenceProcessor* rp) :
79 MetadataAwareOopClosure(rp),
80 _queue(q),
81 _dedup_queue(dq),
82 _heap(ShenandoahHeap::heap())
83 { }
84
85
86 template<UpdateRefsMode UPDATE_REFS>
87 class ShenandoahInitMarkRootsTask : public AbstractGangTask {
88 private:
89 ShenandoahRootProcessor* _rp;
90 bool _process_refs;
91 public:
92 ShenandoahInitMarkRootsTask(ShenandoahRootProcessor* rp, bool process_refs) :
93 AbstractGangTask("Shenandoah init mark roots task"),
94 _rp(rp),
95 _process_refs(process_refs) {
96 }
97
98 void work(uint worker_id) {
99 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
100
101 ShenandoahHeap* heap = ShenandoahHeap::heap();
102 ShenandoahObjToScanQueueSet* queues = heap->concurrentMark()->task_queues();
103 assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id);
104
105 ShenandoahObjToScanQueue* q = queues->queue(worker_id);
106 ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
107 CLDToOopClosure cldCl(&mark_cl);
108 MarkingCodeBlobClosure blobsCl(&mark_cl, ! CodeBlobToOopClosure::FixRelocations);
109
110 // The rationale for selecting the roots to scan is as follows:
111 // a. With unload_classes = true, we only want to scan the actual strong roots from the
112 // code cache. This will allow us to identify the dead classes, unload them, *and*
113 // invalidate the relevant code cache blobs. This could be only done together with
114 // class unloading.
115 // b. With unload_classes = false, we have to nominally retain all the references from code
116 // cache, because there could be the case of embedded class/oop in the generated code,
117 // which we will never visit during mark. Without code cache invalidation, as in (a),
118 // we risk executing that code cache blob, and crashing.
119 // c. With ShenandoahConcurrentScanCodeRoots, we avoid scanning the entire code cache here,
120 // and instead do that in concurrent phase under the relevant lock. This saves init mark
121 // pause time.
122
123 ResourceMark m;
124 if (heap->concurrentMark()->unload_classes()) {
125 _rp->process_strong_roots(&mark_cl, _process_refs ? NULL : &mark_cl, &cldCl, NULL, &blobsCl, NULL, worker_id);
126 } else {
127 if (ShenandoahConcurrentScanCodeRoots) {
128 CodeBlobClosure* code_blobs = NULL;
129 #ifdef ASSERT
130 ShenandoahAssertToSpaceClosure assert_to_space_oops;
131 CodeBlobToOopClosure assert_to_space(&assert_to_space_oops, !CodeBlobToOopClosure::FixRelocations);
132 // If conc code cache evac is disabled, code cache should have only to-space ptrs.
133 // Otherwise, it should have to-space ptrs only if mark does not update refs.
134 if (!ShenandoahConcurrentEvacCodeRoots && !heap->has_forwarded_objects()) {
135 code_blobs = &assert_to_space;
136 }
137 #endif
138 _rp->process_all_roots(&mark_cl, _process_refs ? NULL : &mark_cl, &cldCl, code_blobs, NULL, worker_id);
139 } else {
140 _rp->process_all_roots(&mark_cl, _process_refs ? NULL : &mark_cl, &cldCl, &blobsCl, NULL, worker_id);
141 }
142 }
143 }
144 };
145
146 class ShenandoahUpdateRootsTask : public AbstractGangTask {
147 private:
148 ShenandoahRootProcessor* _rp;
149 const bool _update_code_cache;
150 public:
151 ShenandoahUpdateRootsTask(ShenandoahRootProcessor* rp, bool update_code_cache) :
152 AbstractGangTask("Shenandoah update roots task"),
153 _rp(rp),
154 _update_code_cache(update_code_cache) {
155 }
156
157 void work(uint worker_id) {
158 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
159
160 ShenandoahHeap* heap = ShenandoahHeap::heap();
161 ShenandoahUpdateRefsClosure cl;
162 CLDToOopClosure cldCl(&cl);
163
164 CodeBlobClosure* code_blobs;
165 CodeBlobToOopClosure update_blobs(&cl, CodeBlobToOopClosure::FixRelocations);
166 #ifdef ASSERT
167 ShenandoahAssertToSpaceClosure assert_to_space_oops;
168 CodeBlobToOopClosure assert_to_space(&assert_to_space_oops, !CodeBlobToOopClosure::FixRelocations);
169 #endif
170 if (_update_code_cache) {
171 code_blobs = &update_blobs;
172 } else {
173 code_blobs =
174 DEBUG_ONLY(&assert_to_space)
175 NOT_DEBUG(NULL);
176 }
177 _rp->process_all_roots(&cl, &cl, &cldCl, code_blobs, NULL, worker_id);
178 }
179 };
180
181 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
182 private:
183 ShenandoahConcurrentMark* _cm;
184 ParallelTaskTerminator* _terminator;
185 bool _update_refs;
186
187 public:
188 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ParallelTaskTerminator* terminator, bool update_refs) :
189 AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator), _update_refs(update_refs) {
190 }
191
192
193 void work(uint worker_id) {
194 SuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
195 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
196 jushort* live_data = _cm->get_liveness(worker_id);
197 ReferenceProcessor* rp;
198 if (_cm->process_references()) {
199 rp = ShenandoahHeap::heap()->ref_processor();
200 shenandoah_assert_rp_isalive_installed();
201 } else {
202 rp = NULL;
203 }
204
205 _cm->concurrent_scan_code_roots(worker_id, rp, _update_refs);
206 _cm->mark_loop(worker_id, _terminator, rp,
207 true, // cancellable
208 true, // drain SATBs as we go
209 _cm->unload_classes(),
210 _update_refs,
211 ShenandoahStringDedup::is_enabled()); // perform string dedup
212 }
213 };
214
215 class ShenandoahFinalMarkingTask : public AbstractGangTask {
216 private:
217 ShenandoahConcurrentMark* _cm;
218 ParallelTaskTerminator* _terminator;
219 bool _update_refs;
220 bool _unload_classes;
221 bool _dedup_string;
222
223 public:
224 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ParallelTaskTerminator* terminator,
225 bool update_refs, bool unload_classes, bool dedup_string) :
226 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator),
227 _update_refs(update_refs), _unload_classes(unload_classes), _dedup_string(dedup_string) {
228 }
229
230 void work(uint worker_id) {
231 // First drain remaining SATB buffers.
232 // Notice that this is not strictly necessary for mark-compact. But since
233 // it requires a StrongRootsScope around the task, we need to claim the
234 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
235 // full-gc.
236 _cm->drain_satb_buffers(worker_id, true);
237
238 ReferenceProcessor* rp;
239 if (_cm->process_references()) {
240 rp = ShenandoahHeap::heap()->ref_processor();
241 shenandoah_assert_rp_isalive_installed();
242 } else {
243 rp = NULL;
244 }
245
246 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
247 // let's check here.
248 _cm->concurrent_scan_code_roots(worker_id, rp, _update_refs);
249 _cm->mark_loop(worker_id, _terminator, rp,
250 false, // not cancellable
251 false, // do not drain SATBs, already drained
252 _unload_classes,
253 _update_refs,
254 _dedup_string);
255
256 assert(_cm->task_queues()->is_empty(), "Should be empty");
257 }
258 };
259
260 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
261 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
262 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
263
264 ShenandoahHeap* heap = ShenandoahHeap::heap();
265
266 ShenandoahGCPhase phase(root_phase);
267
268 WorkGang* workers = heap->workers();
269 uint nworkers = workers->active_workers();
270
271 assert(nworkers <= task_queues()->size(), "Just check");
272
273 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
274 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
275 task_queues()->reserve(nworkers);
276
277 if (heap->has_forwarded_objects()) {
278 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, process_references());
279 workers->run_task(&mark_roots);
280 } else {
281 // No need to update references, which means the heap is stable.
282 // Can save time not walking through forwarding pointers.
283 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, process_references());
284 workers->run_task(&mark_roots);
285 }
286
287 if (ShenandoahConcurrentScanCodeRoots) {
288 clear_claim_codecache();
289 }
290 }
291
292 void ShenandoahConcurrentMark::init_mark_roots() {
293 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
294 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
295
296 mark_roots(ShenandoahPhaseTimings::scan_roots);
297 }
298
299 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
300 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
301
302 bool update_code_cache = true; // initialize to safer value
303 switch (root_phase) {
304 case ShenandoahPhaseTimings::update_roots:
305 case ShenandoahPhaseTimings::final_update_refs_roots:
306 // If code cache was evacuated concurrently, we need to update code cache roots.
307 update_code_cache = ShenandoahConcurrentEvacCodeRoots;
308 break;
309 case ShenandoahPhaseTimings::full_gc_roots:
310 update_code_cache = true;
311 break;
312 default:
313 ShouldNotReachHere();
314 }
315
316 ShenandoahHeap* heap = ShenandoahHeap::heap();
317
318 ShenandoahGCPhase phase(root_phase);
319
320 #if defined(COMPILER2) || INCLUDE_JVMCI
321 DerivedPointerTable::clear();
322 #endif
323
324 uint nworkers = heap->workers()->active_workers();
325
326 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
327 ShenandoahUpdateRootsTask update_roots(&root_proc, update_code_cache);
328 heap->workers()->run_task(&update_roots);
329
330 #if defined(COMPILER2) || INCLUDE_JVMCI
331 DerivedPointerTable::update_pointers();
332 #endif
333 }
334
335 void ShenandoahConcurrentMark::initialize(uint workers) {
336 _heap = ShenandoahHeap::heap();
337
338 uint num_queues = MAX2(workers, 1U);
339
340 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
341
342 for (uint i = 0; i < num_queues; ++i) {
343 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
344 task_queue->initialize();
345 _task_queues->register_queue(i, task_queue);
346 }
347
348 ShenandoahBarrierSet::satb_mark_queue_set().set_buffer_size(ShenandoahSATBBufferSize);
349
350 size_t num_regions = ShenandoahHeap::heap()->num_regions();
351 _liveness_local = NEW_C_HEAP_ARRAY(jushort*, workers, mtGC);
352 for (uint worker = 0; worker < workers; worker++) {
353 _liveness_local[worker] = NEW_C_HEAP_ARRAY(jushort, num_regions, mtGC);
354 }
355 }
356
357 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp, bool update_refs) {
358 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
359 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
360 if (!unload_classes()) {
361 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
362 if (update_refs) {
363 ShenandoahMarkResolveRefsClosure cl(q, rp);
364 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
365 CodeCache::blobs_do(&blobs);
366 } else {
367 ShenandoahMarkRefsClosure cl(q, rp);
368 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
369 CodeCache::blobs_do(&blobs);
370 }
371 }
372 }
373 }
374
375 void ShenandoahConcurrentMark::mark_from_roots() {
376 ShenandoahHeap* sh = ShenandoahHeap::heap();
377 WorkGang* workers = sh->workers();
378 uint nworkers = workers->active_workers();
379
380 bool update_refs = sh->has_forwarded_objects();
381
382 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
383
384 if (process_references()) {
385 ReferenceProcessor* rp = sh->ref_processor();
386 rp->set_active_mt_degree(nworkers);
387
388 // enable ("weak") refs discovery
389 rp->enable_discovery(true /*verify_no_refs*/);
390 rp->setup_policy(sh->is_full_gc_in_progress()); // snapshot the soft ref policy to be used in this cycle
391 }
392
393 shenandoah_assert_rp_isalive_not_installed();
394 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), sh->is_alive_closure());
395
396 task_queues()->reserve(nworkers);
397
398 if (UseShenandoahOWST) {
399 ShenandoahTaskTerminator terminator(nworkers, task_queues());
400 ShenandoahConcurrentMarkingTask markingTask = ShenandoahConcurrentMarkingTask(this, &terminator, update_refs);
401 workers->run_task(&markingTask);
402 } else {
403 ParallelTaskTerminator terminator(nworkers, task_queues());
404 ShenandoahConcurrentMarkingTask markingTask = ShenandoahConcurrentMarkingTask(this, &terminator, update_refs);
405 workers->run_task(&markingTask);
406 }
407
408 assert(task_queues()->is_empty() || sh->cancelled_gc(), "Should be empty when not cancelled");
409 }
410
411 void ShenandoahConcurrentMark::finish_mark_from_roots() {
412 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
413
414 ShenandoahHeap* sh = ShenandoahHeap::heap();
415
416 shared_finish_mark_from_roots(/* full_gc = */ false);
417
418 if (sh->has_forwarded_objects()) {
419 update_roots(ShenandoahPhaseTimings::update_roots);
420 }
421
422 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
423 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
424 }
425
426 void ShenandoahConcurrentMark::shared_finish_mark_from_roots(bool full_gc) {
427 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
428
429 ShenandoahHeap* sh = ShenandoahHeap::heap();
430
431 uint nworkers = sh->workers()->active_workers();
432
433 // Finally mark everything else we've got in our queues during the previous steps.
434 // It does two different things for concurrent vs. mark-compact GC:
435 // - For concurrent GC, it starts with empty task queues, drains the remaining
436 // SATB buffers, and then completes the marking closure.
437 // - For mark-compact GC, it starts out with the task queues seeded by initial
438 // root scan, and completes the closure, thus marking through all live objects
439 // The implementation is the same, so it's shared here.
440 {
441 ShenandoahGCPhase phase(full_gc ?
442 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
443 ShenandoahPhaseTimings::finish_queues);
444 task_queues()->reserve(nworkers);
445
446 shenandoah_assert_rp_isalive_not_installed();
447 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), sh->is_alive_closure());
448
449 StrongRootsScope scope(nworkers);
450 if (UseShenandoahOWST) {
451 ShenandoahTaskTerminator terminator(nworkers, task_queues());
452 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
453 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
454 sh->workers()->run_task(&task);
455 } else {
456 ParallelTaskTerminator terminator(nworkers, task_queues());
457 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
458 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
459 sh->workers()->run_task(&task);
460 }
461 }
462
463 assert(task_queues()->is_empty(), "Should be empty");
464
465 // When we're done marking everything, we process weak references.
466 if (process_references()) {
467 weak_refs_work(full_gc);
468 }
469
470 // And finally finish class unloading
471 if (unload_classes()) {
472 sh->unload_classes_and_cleanup_tables(full_gc);
473 }
474
475 assert(task_queues()->is_empty(), "Should be empty");
476
477 }
478
479 class ShenandoahSATBThreadsClosure : public ThreadClosure {
480 ShenandoahSATBBufferClosure* _satb_cl;
481 int _thread_parity;
482
483 public:
484 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
485 _satb_cl(satb_cl),
486 _thread_parity(Threads::thread_claim_parity()) {}
487
488 void do_thread(Thread* thread) {
489 if (thread->is_Java_thread()) {
490 if (thread->claim_oops_do(true, _thread_parity)) {
491 JavaThread* jt = (JavaThread*)thread;
492 ShenandoahThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(_satb_cl);
493 }
494 } else if (thread->is_VM_thread()) {
495 if (thread->claim_oops_do(true, _thread_parity)) {
496 ShenandoahBarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(_satb_cl);
497 }
498 }
499 }
500 };
501
502 void ShenandoahConcurrentMark::drain_satb_buffers(uint worker_id, bool remark) {
503 ShenandoahObjToScanQueue* q = get_queue(worker_id);
504 ShenandoahSATBBufferClosure cl(q);
505
506 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
507 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
508
509 if (remark) {
510 ShenandoahSATBThreadsClosure tc(&cl);
511 Threads::threads_do(&tc);
512 }
513 }
514
515 #if TASKQUEUE_STATS
516 void ShenandoahConcurrentMark::print_taskqueue_stats_hdr(outputStream* const st) {
517 st->print_raw_cr("GC Task Stats");
518 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
519 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
520 }
521
522 void ShenandoahConcurrentMark::print_taskqueue_stats() const {
523 if (!log_develop_is_enabled(Trace, gc, task, stats)) {
524 return;
525 }
526 Log(gc, task, stats) log;
527 ResourceMark rm;
528 LogStream ls(log.trace());
529 outputStream* st = &ls;
530 print_taskqueue_stats_hdr(st);
531
532 TaskQueueStats totals;
533 const uint n = _task_queues->size();
534 for (uint i = 0; i < n; ++i) {
535 st->print(UINT32_FORMAT_W(3), i);
536 _task_queues->queue(i)->stats.print(st);
537 st->cr();
538 totals += _task_queues->queue(i)->stats;
539 }
540 st->print("tot "); totals.print(st); st->cr();
541 DEBUG_ONLY(totals.verify());
542
543 }
544
545 void ShenandoahConcurrentMark::reset_taskqueue_stats() {
546 const uint n = task_queues()->size();
547 for (uint i = 0; i < n; ++i) {
548 task_queues()->queue(i)->stats.reset();
549 }
550 }
551 #endif // TASKQUEUE_STATS
552
553 // Weak Reference Closures
554 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
555 uint _worker_id;
556 ParallelTaskTerminator* _terminator;
557 bool _reset_terminator;
558
559 public:
560 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ParallelTaskTerminator* t, bool reset_terminator = false):
561 _worker_id(worker_id),
562 _terminator(t),
563 _reset_terminator(reset_terminator) {
564 }
565
566 void do_void() {
567 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
568
569 ShenandoahHeap* sh = ShenandoahHeap::heap();
570 ShenandoahConcurrentMark* scm = sh->concurrentMark();
571 assert(scm->process_references(), "why else would we be here?");
572 ReferenceProcessor* rp = sh->ref_processor();
573
574 shenandoah_assert_rp_isalive_installed();
575
576 scm->mark_loop(_worker_id, _terminator, rp,
577 false, // not cancellable
578 false, // do not drain SATBs
579 scm->unload_classes(),
580 sh->has_forwarded_objects(),
581 false); // do not do strdedup
582
583 if (_reset_terminator) {
584 _terminator->reset_for_reuse();
585 }
586 }
587 };
588
589
590 class ShenandoahCMKeepAliveClosure : public OopClosure {
591 private:
592 ShenandoahObjToScanQueue* _queue;
593 ShenandoahHeap* _heap;
594
595 template <class T>
596 inline void do_oop_nv(T* p) {
597 ShenandoahConcurrentMark::mark_through_ref<T, NONE, false /* string dedup */>(p, _heap, _queue);
598 }
599
600 public:
601 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
602 _queue(q), _heap(ShenandoahHeap::heap()) {}
603
604 void do_oop(narrowOop* p) { do_oop_nv(p); }
605 void do_oop(oop* p) { do_oop_nv(p); }
606 };
607
608 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
609 private:
610 ShenandoahObjToScanQueue* _queue;
611 ShenandoahHeap* _heap;
612
613 template <class T>
614 inline void do_oop_nv(T* p) {
615 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, false /* string dedup */>(p, _heap, _queue);
616 }
617
618 public:
619 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
620 _queue(q), _heap(ShenandoahHeap::heap()) {}
621
622 void do_oop(narrowOop* p) { do_oop_nv(p); }
623 void do_oop(oop* p) { do_oop_nv(p); }
624 };
625
626 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
627
628 private:
629 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
630 ParallelTaskTerminator* _terminator;
631 public:
632
633 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
634 ParallelTaskTerminator* t) :
635 AbstractGangTask("Process reference objects in parallel"),
636 _proc_task(proc_task),
637 _terminator(t) {
638 }
639
640 void work(uint worker_id) {
641 ResourceMark rm;
642 HandleMark hm;
643 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
644 ShenandoahHeap* heap = ShenandoahHeap::heap();
645 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
646 if (heap->has_forwarded_objects()) {
647 ShenandoahForwardedIsAliveClosure is_alive;
648 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
649 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
650 } else {
651 ShenandoahIsAliveClosure is_alive;
652 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
653 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
654 }
655 }
656 };
657
658 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
659
660 private:
661 WorkGang* _workers;
662
663 public:
664
665 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
666 _workers(workers) {
667 }
668
669 // Executes a task using worker threads.
670 void execute(ProcessTask& task) {
671 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
672
673 // Shortcut execution if task is empty.
674 // This should be replaced with the generic ReferenceProcessor shortcut,
675 // see JDK-8181214, JDK-8043575, JDK-6938732.
676 if (task.is_empty()) {
677 return;
678 }
679
680 ShenandoahHeap* heap = ShenandoahHeap::heap();
681 ShenandoahConcurrentMark* cm = heap->concurrentMark();
682 uint nworkers = _workers->active_workers();
683 cm->task_queues()->reserve(nworkers);
684 if (UseShenandoahOWST) {
685 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
686 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
687 _workers->run_task(&proc_task_proxy);
688 } else {
689 ParallelTaskTerminator terminator(nworkers, cm->task_queues());
690 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
691 _workers->run_task(&proc_task_proxy);
692 }
693 }
694 };
695
696
697 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
698 assert(process_references(), "sanity");
699
700 ShenandoahHeap* sh = ShenandoahHeap::heap();
701
702 ShenandoahPhaseTimings::Phase phase_root =
703 full_gc ?
704 ShenandoahPhaseTimings::full_gc_weakrefs :
705 ShenandoahPhaseTimings::weakrefs;
706
707 ShenandoahGCPhase phase(phase_root);
708
709 ReferenceProcessor* rp = sh->ref_processor();
710
711 // NOTE: We cannot shortcut on has_discovered_references() here, because
712 // we will miss marking JNI Weak refs then, see implementation in
713 // ReferenceProcessor::process_discovered_references.
714 weak_refs_work_doit(full_gc);
715
716 rp->verify_no_references_recorded();
717 assert(!rp->discovery_enabled(), "Post condition");
718
719 }
720
721 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
722 ShenandoahHeap* sh = ShenandoahHeap::heap();
723
724 ReferenceProcessor* rp = sh->ref_processor();
725
726 ShenandoahPhaseTimings::Phase phase_process =
727 full_gc ?
728 ShenandoahPhaseTimings::full_gc_weakrefs_process :
729 ShenandoahPhaseTimings::weakrefs_process;
730
731 shenandoah_assert_rp_isalive_not_installed();
732 ReferenceProcessorIsAliveMutator fix_isalive(rp, sh->is_alive_closure());
733
734 WorkGang* workers = sh->workers();
735 uint nworkers = workers->active_workers();
736
737 // Setup collector policy for softref cleaning.
738 bool clear_soft_refs = sh->soft_ref_policy()->use_should_clear_all_soft_refs(true /* bogus arg*/);
739 log_develop_debug(gc, ref)("clearing soft refs: %s", BOOL_TO_STR(clear_soft_refs));
740 rp->setup_policy(clear_soft_refs);
741 rp->set_active_mt_degree(nworkers);
742
743 assert(task_queues()->is_empty(), "Should be empty");
744
745 // complete_gc and keep_alive closures instantiated here are only needed for
746 // single-threaded path in RP. They share the queue 0 for tracking work, which
747 // simplifies implementation. Since RP may decide to call complete_gc several
748 // times, we need to be able to reuse the terminator.
749 uint serial_worker_id = 0;
750 ParallelTaskTerminator terminator(1, task_queues());
751 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
752
753 ShenandoahRefProcTaskExecutor executor(workers);
754
755 ReferenceProcessorPhaseTimes pt(sh->gc_timer(), rp->num_queues());
756
757 {
758 ShenandoahGCPhase phase(phase_process);
759
760 if (sh->has_forwarded_objects()) {
761 ShenandoahForwardedIsAliveClosure is_alive;
762 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
763 rp->process_discovered_references(&is_alive, &keep_alive,
764 &complete_gc, &executor,
765 &pt);
766
767 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
768 } else {
769 ShenandoahIsAliveClosure is_alive;
770 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
771 rp->process_discovered_references(&is_alive, &keep_alive,
772 &complete_gc, &executor,
773 &pt);
774
775 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
776 }
777 pt.print_all_references();
778
779 assert(task_queues()->is_empty(), "Should be empty");
780 }
781 }
782
783 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
784 private:
785 ShenandoahHeap* const _heap;
786 public:
787 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
788 virtual bool should_return() { return _heap->cancelled_gc(); }
789 };
790
791 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
792 public:
793 void do_void() {
794 ShenandoahHeap* sh = ShenandoahHeap::heap();
795 ShenandoahConcurrentMark* scm = sh->concurrentMark();
796 assert(scm->process_references(), "why else would we be here?");
797 ParallelTaskTerminator terminator(1, scm->task_queues());
798
799 ReferenceProcessor* rp = sh->ref_processor();
800 shenandoah_assert_rp_isalive_installed();
801
802 scm->mark_loop(0, &terminator, rp,
803 false, // not cancellable
804 true, // drain SATBs
805 scm->unload_classes(),
806 sh->has_forwarded_objects(),
807 false); // do not do strdedup
808 }
809 };
810
811 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
812 private:
813 ShenandoahObjToScanQueue* _queue;
814 ShenandoahHeap* _heap;
815
816 template <class T>
817 inline void do_oop_nv(T* p) {
818 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, false /* string dedup */>(p, _heap, _queue);
819 }
820
821 public:
822 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
823 _queue(q), _heap(ShenandoahHeap::heap()) {}
824
825 void do_oop(narrowOop* p) { do_oop_nv(p); }
826 void do_oop(oop* p) { do_oop_nv(p); }
827 };
828
829 void ShenandoahConcurrentMark::preclean_weak_refs() {
830 // Pre-cleaning weak references before diving into STW makes sense at the
831 // end of concurrent mark. This will filter out the references which referents
832 // are alive. Note that ReferenceProcessor already filters out these on reference
833 // discovery, and the bulk of work is done here. This phase processes leftovers
834 // that missed the initial filtering, i.e. when referent was marked alive after
835 // reference was discovered by RP.
836
837 assert(process_references(), "sanity");
838
839 ShenandoahHeap* sh = ShenandoahHeap::heap();
840 ReferenceProcessor* rp = sh->ref_processor();
841
842 // Shortcut if no references were discovered to avoid winding up threads.
843 if (!rp->has_discovered_references()) {
844 return;
845 }
846
847 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
848
849 shenandoah_assert_rp_isalive_not_installed();
850 ReferenceProcessorIsAliveMutator fix_isalive(rp, sh->is_alive_closure());
851
852 // Interrupt on cancelled GC
853 ShenandoahCancelledGCYieldClosure yield;
854
855 assert(task_queues()->is_empty(), "Should be empty");
856
857 ShenandoahPrecleanCompleteGCClosure complete_gc;
858 if (sh->has_forwarded_objects()) {
859 ShenandoahForwardedIsAliveClosure is_alive;
860 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(get_queue(0));
861 ResourceMark rm;
862 rp->preclean_discovered_references(&is_alive, &keep_alive,
863 &complete_gc, &yield,
864 NULL);
865 } else {
866 ShenandoahIsAliveClosure is_alive;
867 ShenandoahCMKeepAliveClosure keep_alive(get_queue(0));
868 ResourceMark rm;
869 rp->preclean_discovered_references(&is_alive, &keep_alive,
870 &complete_gc, &yield,
871 NULL);
872 }
873
874 assert(task_queues()->is_empty(), "Should be empty");
875 }
876
877 void ShenandoahConcurrentMark::cancel() {
878 // Clean up marking stacks.
879 ShenandoahObjToScanQueueSet* queues = task_queues();
880 queues->clear();
881
882 // Cancel SATB buffers.
883 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
884 }
885
886 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
887 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
888 return _task_queues->queue(worker_id);
889 }
890
891 void ShenandoahConcurrentMark::clear_queue(ShenandoahObjToScanQueue *q) {
892 q->set_empty();
893 q->overflow_stack()->clear();
894 q->clear_buffer();
895 }
896
897 template <bool CANCELLABLE, bool DRAIN_SATB>
898 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ParallelTaskTerminator *t, ReferenceProcessor *rp,
899 bool class_unload, bool update_refs, bool strdedup) {
900 ShenandoahObjToScanQueue* q = get_queue(w);
901
902 jushort* ld = get_liveness(w);
903 Copy::fill_to_bytes(ld, _heap->num_regions() * sizeof(jushort));
904
905 // TODO: We can clean up this if we figure out how to do templated oop closures that
906 // play nice with specialized_oop_iterators.
907 if (class_unload) {
908 if (update_refs) {
909 if (strdedup) {
910 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
911 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, dq, rp);
912 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
913 } else {
914 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
915 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
916 }
917 } else {
918 if (strdedup) {
919 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
920 ShenandoahMarkRefsMetadataDedupClosure cl(q, dq, rp);
921 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
922 } else {
923 ShenandoahMarkRefsMetadataClosure cl(q, rp);
924 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
925 }
926 }
927 } else {
928 if (update_refs) {
929 if (strdedup) {
930 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
931 ShenandoahMarkUpdateRefsDedupClosure cl(q, dq, rp);
932 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
933 } else {
934 ShenandoahMarkUpdateRefsClosure cl(q, rp);
935 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
936 }
937 } else {
938 if (strdedup) {
939 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
940 ShenandoahMarkRefsDedupClosure cl(q, dq, rp);
941 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
942 } else {
943 ShenandoahMarkRefsClosure cl(q, rp);
944 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE, DRAIN_SATB>(&cl, ld, w, t);
945 }
946 }
947 }
948
949
950 for (uint i = 0; i < _heap->num_regions(); i++) {
951 ShenandoahHeapRegion* r = _heap->get_region(i);
952 jushort live = ld[i];
953 if (live > 0) {
954 r->increase_live_data_gc_words(live);
955 }
956 }
957 }
958
959 template <class T, bool CANCELLABLE, bool DRAIN_SATB>
960 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator *terminator) {
961 int seed = 17;
962 uintx stride = CANCELLABLE ? ShenandoahMarkLoopStride : 1;
963
964 ShenandoahHeap* heap = ShenandoahHeap::heap();
965 ShenandoahObjToScanQueueSet* queues = task_queues();
966 ShenandoahObjToScanQueue* q;
967 ShenandoahMarkTask t;
968
969 /*
970 * Process outstanding queues, if any.
971 *
972 * There can be more queues than workers. To deal with the imbalance, we claim
973 * extra queues first. Since marking can push new tasks into the queue associated
974 * with this worker id, we come back to process this queue in the normal loop.
975 */
976 assert(queues->get_reserved() == heap->workers()->active_workers(),
977 "Need to reserve proper number of queues");
978
979 q = queues->claim_next();
980 while (q != NULL) {
981 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
982 ShenandoahCancelledTerminatorTerminator tt;
983 while (!terminator->offer_termination(&tt));
984 return;
985 }
986
987 for (uint i = 0; i < stride; i++) {
988 if (try_queue(q, t)) {
989 do_task<T>(q, cl, live_data, &t);
990 } else {
991 assert(q->is_empty(), "Must be empty");
992 q = queues->claim_next();
993 break;
994 }
995 }
996 }
997 q = get_queue(worker_id);
998
999 ShenandoahSATBBufferClosure drain_satb(q);
1000 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
1001
1002 /*
1003 * Normal marking loop:
1004 */
1005 while (true) {
1006 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
1007 ShenandoahCancelledTerminatorTerminator tt;
1008 while (!terminator->offer_termination(&tt));
1009 return;
1010 }
1011
1012 if (DRAIN_SATB) {
1013 while (satb_mq_set.completed_buffers_num() > 0) {
1014 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
1015 }
1016 }
1017
1018 uint work = 0;
1019 for (uint i = 0; i < stride; i++) {
1020 if (try_queue(q, t) ||
1021 queues->steal(worker_id, &seed, t)) {
1022 do_task<T>(q, cl, live_data, &t);
1023 work++;
1024 } else {
1025 break;
1026 }
1027 }
1028
1029 if (work == 0) {
1030 // No work encountered in current stride, try to terminate.
1031 // Need to leave the STS here otherwise it might block safepoints.
1032 SuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
1033 if (terminator->offer_termination()) return;
1034 }
1035 }
1036 }
1037
1038 bool ShenandoahConcurrentMark::process_references() const {
1039 return _heap->process_references();
1040 }
1041
1042 bool ShenandoahConcurrentMark::unload_classes() const {
1043 return _heap->unload_classes();
1044 }
1045
1046 bool ShenandoahConcurrentMark::claim_codecache() {
1047 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1048 return _claimed_codecache.try_set();
1049 }
1050
1051 void ShenandoahConcurrentMark::clear_claim_codecache() {
1052 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1053 _claimed_codecache.unset();
1054 }
1055
1056 jushort* ShenandoahConcurrentMark::get_liveness(uint worker_id) {
1057 return _liveness_local[worker_id];
1058 }
1059
1060 // Generate Shenandoah specialized oop_oop_iterate functions.
1061 SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_SHENANDOAH(ALL_KLASS_OOP_OOP_ITERATE_DEFN)