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 _cm->unload_classes(),
209 _update_refs,
210 ShenandoahStringDedup::is_enabled()); // perform string dedup
211 }
212 };
213
214 class ShenandoahFinalMarkingTask : public AbstractGangTask {
215 private:
216 ShenandoahConcurrentMark* _cm;
217 ParallelTaskTerminator* _terminator;
218 bool _update_refs;
219 bool _unload_classes;
220 bool _dedup_string;
221
222 public:
223 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ParallelTaskTerminator* terminator,
224 bool update_refs, bool unload_classes, bool dedup_string) :
225 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator),
226 _update_refs(update_refs), _unload_classes(unload_classes), _dedup_string(dedup_string) {
227 }
228
229 void work(uint worker_id) {
230 // First drain remaining SATB buffers.
231 // Notice that this is not strictly necessary for mark-compact. But since
232 // it requires a StrongRootsScope around the task, we need to claim the
233 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
234 // full-gc.
235 ShenandoahObjToScanQueue* q = get_queue(worker_id);
236 ShenandoahSATBBufferClosure cl(q);
237 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
238 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
239 ShenandoahSATBThreadsClosure tc(&cl);
240 Threads::threads_do(&tc);
241
242 ReferenceProcessor* rp;
243 if (_cm->process_references()) {
244 rp = ShenandoahHeap::heap()->ref_processor();
245 shenandoah_assert_rp_isalive_installed();
246 } else {
247 rp = NULL;
248 }
249
250 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
251 // let's check here.
252 _cm->concurrent_scan_code_roots(worker_id, rp, _update_refs);
253 _cm->mark_loop(worker_id, _terminator, rp,
254 false, // not cancellable
255 _unload_classes,
256 _update_refs,
257 _dedup_string);
258
259 assert(_cm->task_queues()->is_empty(), "Should be empty");
260 }
261 };
262
263 void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
264 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
265 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
266
267 ShenandoahHeap* heap = ShenandoahHeap::heap();
268
269 ShenandoahGCPhase phase(root_phase);
270
271 WorkGang* workers = heap->workers();
272 uint nworkers = workers->active_workers();
273
274 assert(nworkers <= task_queues()->size(), "Just check");
275
276 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
277 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
278 task_queues()->reserve(nworkers);
279
280 if (heap->has_forwarded_objects()) {
281 ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, process_references());
282 workers->run_task(&mark_roots);
283 } else {
284 // No need to update references, which means the heap is stable.
285 // Can save time not walking through forwarding pointers.
286 ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, process_references());
287 workers->run_task(&mark_roots);
288 }
289
290 if (ShenandoahConcurrentScanCodeRoots) {
291 clear_claim_codecache();
292 }
293 }
294
295 void ShenandoahConcurrentMark::init_mark_roots() {
296 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
297 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
298
299 mark_roots(ShenandoahPhaseTimings::scan_roots);
300 }
301
302 void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
303 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
304
305 bool update_code_cache = true; // initialize to safer value
306 switch (root_phase) {
307 case ShenandoahPhaseTimings::update_roots:
308 case ShenandoahPhaseTimings::final_update_refs_roots:
309 // If code cache was evacuated concurrently, we need to update code cache roots.
310 update_code_cache = ShenandoahConcurrentEvacCodeRoots;
311 break;
312 case ShenandoahPhaseTimings::full_gc_roots:
313 update_code_cache = true;
314 break;
315 default:
316 ShouldNotReachHere();
317 }
318
319 ShenandoahHeap* heap = ShenandoahHeap::heap();
320
321 ShenandoahGCPhase phase(root_phase);
322
323 #if defined(COMPILER2) || INCLUDE_JVMCI
324 DerivedPointerTable::clear();
325 #endif
326
327 uint nworkers = heap->workers()->active_workers();
328
329 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
330 ShenandoahUpdateRootsTask update_roots(&root_proc, update_code_cache);
331 heap->workers()->run_task(&update_roots);
332
333 #if defined(COMPILER2) || INCLUDE_JVMCI
334 DerivedPointerTable::update_pointers();
335 #endif
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 ShenandoahBarrierSet::satb_mark_queue_set().set_buffer_size(ShenandoahSATBBufferSize);
352
353 size_t num_regions = ShenandoahHeap::heap()->num_regions();
354 _liveness_local = NEW_C_HEAP_ARRAY(jushort*, workers, mtGC);
355 for (uint worker = 0; worker < workers; worker++) {
356 _liveness_local[worker] = NEW_C_HEAP_ARRAY(jushort, num_regions, mtGC);
357 }
358 }
359
360 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp, bool update_refs) {
361 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
362 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
363 if (!unload_classes()) {
364 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
365 if (update_refs) {
366 ShenandoahMarkResolveRefsClosure cl(q, rp);
367 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
368 CodeCache::blobs_do(&blobs);
369 } else {
370 ShenandoahMarkRefsClosure cl(q, rp);
371 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
372 CodeCache::blobs_do(&blobs);
373 }
374 }
375 }
376 }
377
378 void ShenandoahConcurrentMark::mark_from_roots() {
379 ShenandoahHeap* sh = ShenandoahHeap::heap();
380 WorkGang* workers = sh->workers();
381 uint nworkers = workers->active_workers();
382
383 bool update_refs = sh->has_forwarded_objects();
384
385 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
386
387 if (process_references()) {
388 ReferenceProcessor* rp = sh->ref_processor();
389 rp->set_active_mt_degree(nworkers);
390
391 // enable ("weak") refs discovery
392 rp->enable_discovery(true /*verify_no_refs*/);
393 rp->setup_policy(sh->is_full_gc_in_progress()); // snapshot the soft ref policy to be used in this cycle
394 }
395
396 shenandoah_assert_rp_isalive_not_installed();
397 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), sh->is_alive_closure());
398
399 task_queues()->reserve(nworkers);
400
401 if (UseShenandoahOWST) {
402 ShenandoahTaskTerminator terminator(nworkers, task_queues());
403 ShenandoahConcurrentMarkingTask markingTask = ShenandoahConcurrentMarkingTask(this, &terminator, update_refs);
404 workers->run_task(&markingTask);
405 } else {
406 ParallelTaskTerminator terminator(nworkers, task_queues());
407 ShenandoahConcurrentMarkingTask markingTask = ShenandoahConcurrentMarkingTask(this, &terminator, update_refs);
408 workers->run_task(&markingTask);
409 }
410
411 assert(task_queues()->is_empty() || sh->cancelled_gc(), "Should be empty when not cancelled");
412 }
413
414 void ShenandoahConcurrentMark::finish_mark_from_roots() {
415 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
416
417 ShenandoahHeap* sh = ShenandoahHeap::heap();
418
419 shared_finish_mark_from_roots(/* full_gc = */ false);
420
421 if (sh->has_forwarded_objects()) {
422 update_roots(ShenandoahPhaseTimings::update_roots);
423 }
424
425 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
426 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
427 }
428
429 void ShenandoahConcurrentMark::shared_finish_mark_from_roots(bool full_gc) {
430 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
431
432 ShenandoahHeap* sh = ShenandoahHeap::heap();
433
434 uint nworkers = sh->workers()->active_workers();
435
436 // Finally mark everything else we've got in our queues during the previous steps.
437 // It does two different things for concurrent vs. mark-compact GC:
438 // - For concurrent GC, it starts with empty task queues, drains the remaining
439 // SATB buffers, and then completes the marking closure.
440 // - For mark-compact GC, it starts out with the task queues seeded by initial
441 // root scan, and completes the closure, thus marking through all live objects
442 // The implementation is the same, so it's shared here.
443 {
444 ShenandoahGCPhase phase(full_gc ?
445 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
446 ShenandoahPhaseTimings::finish_queues);
447 task_queues()->reserve(nworkers);
448
449 shenandoah_assert_rp_isalive_not_installed();
450 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), sh->is_alive_closure());
451
452 StrongRootsScope scope(nworkers);
453 if (UseShenandoahOWST) {
454 ShenandoahTaskTerminator terminator(nworkers, task_queues());
455 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
456 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
457 sh->workers()->run_task(&task);
458 } else {
459 ParallelTaskTerminator terminator(nworkers, task_queues());
460 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(),
461 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
462 sh->workers()->run_task(&task);
463 }
464 }
465
466 assert(task_queues()->is_empty(), "Should be empty");
467
468 // When we're done marking everything, we process weak references.
469 if (process_references()) {
470 weak_refs_work(full_gc);
471 }
472
473 // And finally finish class unloading
474 if (unload_classes()) {
475 sh->unload_classes_and_cleanup_tables(full_gc);
476 }
477
478 assert(task_queues()->is_empty(), "Should be empty");
479
480 }
481
482 class ShenandoahSATBThreadsClosure : public ThreadClosure {
483 ShenandoahSATBBufferClosure* _satb_cl;
484 int _thread_parity;
485
486 public:
487 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
488 _satb_cl(satb_cl),
489 _thread_parity(Threads::thread_claim_parity()) {}
490
491 void do_thread(Thread* thread) {
492 if (thread->is_Java_thread()) {
493 if (thread->claim_oops_do(true, _thread_parity)) {
494 JavaThread* jt = (JavaThread*)thread;
495 ShenandoahThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(_satb_cl);
496 }
497 } else if (thread->is_VM_thread()) {
498 if (thread->claim_oops_do(true, _thread_parity)) {
499 ShenandoahBarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(_satb_cl);
500 }
501 }
502 }
503 };
504
505 #if TASKQUEUE_STATS
506 void ShenandoahConcurrentMark::print_taskqueue_stats_hdr(outputStream* const st) {
507 st->print_raw_cr("GC Task Stats");
508 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
509 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
510 }
511
512 void ShenandoahConcurrentMark::print_taskqueue_stats() const {
513 if (!log_develop_is_enabled(Trace, gc, task, stats)) {
514 return;
515 }
516 Log(gc, task, stats) log;
517 ResourceMark rm;
518 LogStream ls(log.trace());
519 outputStream* st = &ls;
520 print_taskqueue_stats_hdr(st);
521
522 TaskQueueStats totals;
523 const uint n = _task_queues->size();
524 for (uint i = 0; i < n; ++i) {
525 st->print(UINT32_FORMAT_W(3), i);
526 _task_queues->queue(i)->stats.print(st);
527 st->cr();
528 totals += _task_queues->queue(i)->stats;
529 }
530 st->print("tot "); totals.print(st); st->cr();
531 DEBUG_ONLY(totals.verify());
532
533 }
534
535 void ShenandoahConcurrentMark::reset_taskqueue_stats() {
536 const uint n = task_queues()->size();
537 for (uint i = 0; i < n; ++i) {
538 task_queues()->queue(i)->stats.reset();
539 }
540 }
541 #endif // TASKQUEUE_STATS
542
543 // Weak Reference Closures
544 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
545 uint _worker_id;
546 ParallelTaskTerminator* _terminator;
547 bool _reset_terminator;
548
549 public:
550 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ParallelTaskTerminator* t, bool reset_terminator = false):
551 _worker_id(worker_id),
552 _terminator(t),
553 _reset_terminator(reset_terminator) {
554 }
555
556 void do_void() {
557 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
558
559 ShenandoahHeap* sh = ShenandoahHeap::heap();
560 ShenandoahConcurrentMark* scm = sh->concurrentMark();
561 assert(scm->process_references(), "why else would we be here?");
562 ReferenceProcessor* rp = sh->ref_processor();
563
564 shenandoah_assert_rp_isalive_installed();
565
566 scm->mark_loop(_worker_id, _terminator, rp,
567 false, // not cancellable
568 scm->unload_classes(),
569 sh->has_forwarded_objects(),
570 false); // do not do strdedup
571
572 if (_reset_terminator) {
573 _terminator->reset_for_reuse();
574 }
575 }
576 };
577
578
579 class ShenandoahCMKeepAliveClosure : public OopClosure {
580 private:
581 ShenandoahObjToScanQueue* _queue;
582 ShenandoahHeap* _heap;
583
584 template <class T>
585 inline void do_oop_nv(T* p) {
586 ShenandoahConcurrentMark::mark_through_ref<T, NONE, false /* string dedup */>(p, _heap, _queue);
587 }
588
589 public:
590 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
591 _queue(q), _heap(ShenandoahHeap::heap()) {}
592
593 void do_oop(narrowOop* p) { do_oop_nv(p); }
594 void do_oop(oop* p) { do_oop_nv(p); }
595 };
596
597 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
598 private:
599 ShenandoahObjToScanQueue* _queue;
600 ShenandoahHeap* _heap;
601
602 template <class T>
603 inline void do_oop_nv(T* p) {
604 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, false /* string dedup */>(p, _heap, _queue);
605 }
606
607 public:
608 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
609 _queue(q), _heap(ShenandoahHeap::heap()) {}
610
611 void do_oop(narrowOop* p) { do_oop_nv(p); }
612 void do_oop(oop* p) { do_oop_nv(p); }
613 };
614
615 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
616
617 private:
618 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
619 ParallelTaskTerminator* _terminator;
620 public:
621
622 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
623 ParallelTaskTerminator* t) :
624 AbstractGangTask("Process reference objects in parallel"),
625 _proc_task(proc_task),
626 _terminator(t) {
627 }
628
629 void work(uint worker_id) {
630 ResourceMark rm;
631 HandleMark hm;
632 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
633 ShenandoahHeap* heap = ShenandoahHeap::heap();
634 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
635 if (heap->has_forwarded_objects()) {
636 ShenandoahForwardedIsAliveClosure is_alive;
637 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
638 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
639 } else {
640 ShenandoahIsAliveClosure is_alive;
641 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
642 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
643 }
644 }
645 };
646
647 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
648
649 private:
650 WorkGang* _workers;
651
652 public:
653
654 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
655 _workers(workers) {
656 }
657
658 // Executes a task using worker threads.
659 void execute(ProcessTask& task) {
660 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
661
662 // Shortcut execution if task is empty.
663 // This should be replaced with the generic ReferenceProcessor shortcut,
664 // see JDK-8181214, JDK-8043575, JDK-6938732.
665 if (task.is_empty()) {
666 return;
667 }
668
669 ShenandoahHeap* heap = ShenandoahHeap::heap();
670 ShenandoahConcurrentMark* cm = heap->concurrentMark();
671 uint nworkers = _workers->active_workers();
672 cm->task_queues()->reserve(nworkers);
673 if (UseShenandoahOWST) {
674 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
675 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
676 _workers->run_task(&proc_task_proxy);
677 } else {
678 ParallelTaskTerminator terminator(nworkers, cm->task_queues());
679 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
680 _workers->run_task(&proc_task_proxy);
681 }
682 }
683 };
684
685
686 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
687 assert(process_references(), "sanity");
688
689 ShenandoahHeap* sh = ShenandoahHeap::heap();
690
691 ShenandoahPhaseTimings::Phase phase_root =
692 full_gc ?
693 ShenandoahPhaseTimings::full_gc_weakrefs :
694 ShenandoahPhaseTimings::weakrefs;
695
696 ShenandoahGCPhase phase(phase_root);
697
698 ReferenceProcessor* rp = sh->ref_processor();
699
700 // NOTE: We cannot shortcut on has_discovered_references() here, because
701 // we will miss marking JNI Weak refs then, see implementation in
702 // ReferenceProcessor::process_discovered_references.
703 weak_refs_work_doit(full_gc);
704
705 rp->verify_no_references_recorded();
706 assert(!rp->discovery_enabled(), "Post condition");
707
708 }
709
710 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
711 ShenandoahHeap* sh = ShenandoahHeap::heap();
712
713 ReferenceProcessor* rp = sh->ref_processor();
714
715 ShenandoahPhaseTimings::Phase phase_process =
716 full_gc ?
717 ShenandoahPhaseTimings::full_gc_weakrefs_process :
718 ShenandoahPhaseTimings::weakrefs_process;
719
720 shenandoah_assert_rp_isalive_not_installed();
721 ReferenceProcessorIsAliveMutator fix_isalive(rp, sh->is_alive_closure());
722
723 WorkGang* workers = sh->workers();
724 uint nworkers = workers->active_workers();
725
726 // Setup collector policy for softref cleaning.
727 bool clear_soft_refs = sh->soft_ref_policy()->use_should_clear_all_soft_refs(true /* bogus arg*/);
728 log_develop_debug(gc, ref)("clearing soft refs: %s", BOOL_TO_STR(clear_soft_refs));
729 rp->setup_policy(clear_soft_refs);
730 rp->set_active_mt_degree(nworkers);
731
732 assert(task_queues()->is_empty(), "Should be empty");
733
734 // complete_gc and keep_alive closures instantiated here are only needed for
735 // single-threaded path in RP. They share the queue 0 for tracking work, which
736 // simplifies implementation. Since RP may decide to call complete_gc several
737 // times, we need to be able to reuse the terminator.
738 uint serial_worker_id = 0;
739 ParallelTaskTerminator terminator(1, task_queues());
740 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
741
742 ShenandoahRefProcTaskExecutor executor(workers);
743
744 ReferenceProcessorPhaseTimes pt(sh->gc_timer(), rp->num_queues());
745
746 {
747 ShenandoahGCPhase phase(phase_process);
748
749 if (sh->has_forwarded_objects()) {
750 ShenandoahForwardedIsAliveClosure is_alive;
751 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
752 rp->process_discovered_references(&is_alive, &keep_alive,
753 &complete_gc, &executor,
754 &pt);
755
756 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
757 } else {
758 ShenandoahIsAliveClosure is_alive;
759 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
760 rp->process_discovered_references(&is_alive, &keep_alive,
761 &complete_gc, &executor,
762 &pt);
763
764 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
765 }
766 pt.print_all_references();
767
768 assert(task_queues()->is_empty(), "Should be empty");
769 }
770 }
771
772 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
773 private:
774 ShenandoahHeap* const _heap;
775 public:
776 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
777 virtual bool should_return() { return _heap->cancelled_gc(); }
778 };
779
780 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
781 public:
782 void do_void() {
783 ShenandoahHeap* sh = ShenandoahHeap::heap();
784 ShenandoahConcurrentMark* scm = sh->concurrentMark();
785 assert(scm->process_references(), "why else would we be here?");
786 ParallelTaskTerminator terminator(1, scm->task_queues());
787
788 ReferenceProcessor* rp = sh->ref_processor();
789 shenandoah_assert_rp_isalive_installed();
790
791 scm->mark_loop(0, &terminator, rp,
792 false, // not cancellable
793 scm->unload_classes(),
794 sh->has_forwarded_objects(),
795 false); // do not do strdedup
796 }
797 };
798
799 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
800 private:
801 ShenandoahObjToScanQueue* _queue;
802 ShenandoahHeap* _heap;
803
804 template <class T>
805 inline void do_oop_nv(T* p) {
806 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, false /* string dedup */>(p, _heap, _queue);
807 }
808
809 public:
810 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
811 _queue(q), _heap(ShenandoahHeap::heap()) {}
812
813 void do_oop(narrowOop* p) { do_oop_nv(p); }
814 void do_oop(oop* p) { do_oop_nv(p); }
815 };
816
817 void ShenandoahConcurrentMark::preclean_weak_refs() {
818 // Pre-cleaning weak references before diving into STW makes sense at the
819 // end of concurrent mark. This will filter out the references which referents
820 // are alive. Note that ReferenceProcessor already filters out these on reference
821 // discovery, and the bulk of work is done here. This phase processes leftovers
822 // that missed the initial filtering, i.e. when referent was marked alive after
823 // reference was discovered by RP.
824
825 assert(process_references(), "sanity");
826
827 ShenandoahHeap* sh = ShenandoahHeap::heap();
828 ReferenceProcessor* rp = sh->ref_processor();
829
830 // Shortcut if no references were discovered to avoid winding up threads.
831 if (!rp->has_discovered_references()) {
832 return;
833 }
834
835 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
836
837 shenandoah_assert_rp_isalive_not_installed();
838 ReferenceProcessorIsAliveMutator fix_isalive(rp, sh->is_alive_closure());
839
840 // Interrupt on cancelled GC
841 ShenandoahCancelledGCYieldClosure yield;
842
843 assert(task_queues()->is_empty(), "Should be empty");
844
845 ShenandoahPrecleanCompleteGCClosure complete_gc;
846 if (sh->has_forwarded_objects()) {
847 ShenandoahForwardedIsAliveClosure is_alive;
848 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(get_queue(0));
849 ResourceMark rm;
850 rp->preclean_discovered_references(&is_alive, &keep_alive,
851 &complete_gc, &yield,
852 NULL);
853 } else {
854 ShenandoahIsAliveClosure is_alive;
855 ShenandoahCMKeepAliveClosure keep_alive(get_queue(0));
856 ResourceMark rm;
857 rp->preclean_discovered_references(&is_alive, &keep_alive,
858 &complete_gc, &yield,
859 NULL);
860 }
861
862 assert(task_queues()->is_empty(), "Should be empty");
863 }
864
865 void ShenandoahConcurrentMark::cancel() {
866 // Clean up marking stacks.
867 ShenandoahObjToScanQueueSet* queues = task_queues();
868 queues->clear();
869
870 // Cancel SATB buffers.
871 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
872 }
873
874 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
875 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
876 return _task_queues->queue(worker_id);
877 }
878
879 void ShenandoahConcurrentMark::clear_queue(ShenandoahObjToScanQueue *q) {
880 q->set_empty();
881 q->overflow_stack()->clear();
882 q->clear_buffer();
883 }
884
885 template <bool CANCELLABLE>
886 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ParallelTaskTerminator *t, ReferenceProcessor *rp,
887 bool class_unload, bool update_refs, bool strdedup) {
888 ShenandoahObjToScanQueue* q = get_queue(w);
889
890 jushort* ld = get_liveness(w);
891 Copy::fill_to_bytes(ld, _heap->num_regions() * sizeof(jushort));
892
893 // TODO: We can clean up this if we figure out how to do templated oop closures that
894 // play nice with specialized_oop_iterators.
895 if (class_unload) {
896 if (update_refs) {
897 if (strdedup) {
898 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
899 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, dq, rp);
900 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
901 } else {
902 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
903 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
904 }
905 } else {
906 if (strdedup) {
907 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
908 ShenandoahMarkRefsMetadataDedupClosure cl(q, dq, 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 (update_refs) {
917 if (strdedup) {
918 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
919 ShenandoahMarkUpdateRefsDedupClosure cl(q, dq, rp);
920 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
921 } else {
922 ShenandoahMarkUpdateRefsClosure cl(q, rp);
923 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
924 }
925 } else {
926 if (strdedup) {
927 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
928 ShenandoahMarkRefsDedupClosure cl(q, dq, rp);
929 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
930 } else {
931 ShenandoahMarkRefsClosure cl(q, rp);
932 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
933 }
934 }
935 }
936
937
938 for (uint i = 0; i < _heap->num_regions(); i++) {
939 ShenandoahHeapRegion* r = _heap->get_region(i);
940 jushort live = ld[i];
941 if (live > 0) {
942 r->increase_live_data_gc_words(live);
943 }
944 }
945 }
946
947 template <class T, bool CANCELLABLE>
948 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator *terminator) {
949 int seed = 17;
950 uintx stride = CANCELLABLE ? ShenandoahMarkLoopStride : 1;
951
952 ShenandoahHeap* heap = ShenandoahHeap::heap();
953 ShenandoahObjToScanQueueSet* queues = task_queues();
954 ShenandoahObjToScanQueue* q;
955 ShenandoahMarkTask t;
956
957 /*
958 * Process outstanding queues, if any.
959 *
960 * There can be more queues than workers. To deal with the imbalance, we claim
961 * extra queues first. Since marking can push new tasks into the queue associated
962 * with this worker id, we come back to process this queue in the normal loop.
963 */
964 assert(queues->get_reserved() == heap->workers()->active_workers(),
965 "Need to reserve proper number of queues");
966
967 q = queues->claim_next();
968 while (q != NULL) {
969 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
970 ShenandoahCancelledTerminatorTerminator tt;
971 while (!terminator->offer_termination(&tt));
972 return;
973 }
974
975 for (uint i = 0; i < stride; i++) {
976 if (try_queue(q, t)) {
977 do_task<T>(q, cl, live_data, &t);
978 } else {
979 assert(q->is_empty(), "Must be empty");
980 q = queues->claim_next();
981 break;
982 }
983 }
984 }
985 q = get_queue(worker_id);
986
987 ShenandoahSATBBufferClosure drain_satb(q);
988 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
989
990 /*
991 * Normal marking loop:
992 */
993 while (true) {
994 if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
995 ShenandoahCancelledTerminatorTerminator tt;
996 while (!terminator->offer_termination(&tt));
997 return;
998 }
999
1000 while (satb_mq_set.completed_buffers_num() > 0) {
1001 satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
1002 }
1003
1004 uint work = 0;
1005 for (uint i = 0; i < stride; i++) {
1006 if (try_queue(q, t) ||
1007 queues->steal(worker_id, &seed, t)) {
1008 do_task<T>(q, cl, live_data, &t);
1009 work++;
1010 } else {
1011 break;
1012 }
1013 }
1014
1015 if (work == 0) {
1016 // No work encountered in current stride, try to terminate.
1017 // Need to leave the STS here otherwise it might block safepoints.
1018 SuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
1019 if (terminator->offer_termination()) return;
1020 }
1021 }
1022 }
1023
1024 bool ShenandoahConcurrentMark::process_references() const {
1025 return _heap->process_references();
1026 }
1027
1028 bool ShenandoahConcurrentMark::unload_classes() const {
1029 return _heap->unload_classes();
1030 }
1031
1032 bool ShenandoahConcurrentMark::claim_codecache() {
1033 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1034 return _claimed_codecache.try_set();
1035 }
1036
1037 void ShenandoahConcurrentMark::clear_claim_codecache() {
1038 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1039 _claimed_codecache.unset();
1040 }
1041
1042 jushort* ShenandoahConcurrentMark::get_liveness(uint worker_id) {
1043 return _liveness_local[worker_id];
1044 }
1045
1046 // Generate Shenandoah specialized oop_oop_iterate functions.
1047 SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_SHENANDOAH(ALL_KLASS_OOP_OOP_ITERATE_DEFN)