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 true, // count liveness
210 _cm->unload_classes(),
211 _update_refs,
212 ShenandoahStringDedup::is_enabled()); // perform string dedup
213 }
214 };
215
216 class ShenandoahFinalMarkingTask : public AbstractGangTask {
217 private:
218 ShenandoahConcurrentMark* _cm;
219 ParallelTaskTerminator* _terminator;
220 bool _update_refs;
221 bool _count_live;
222 bool _unload_classes;
223 bool _dedup_string;
224
225 public:
226 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ParallelTaskTerminator* terminator, bool update_refs,
227 bool count_live, bool unload_classes, bool dedup_string = false) :
228 AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _update_refs(update_refs),
229 _count_live(count_live), _unload_classes(unload_classes), _dedup_string(dedup_string) {
230 }
231
232 void work(uint worker_id) {
233 // First drain remaining SATB buffers.
234 // Notice that this is not strictly necessary for mark-compact. But since
235 // it requires a StrongRootsScope around the task, we need to claim the
236 // threads, and performance-wise it doesn't really matter. Adds about 1ms to
237 // full-gc.
238 _cm->drain_satb_buffers(worker_id, true);
239
240 ReferenceProcessor* rp;
241 if (_cm->process_references()) {
242 rp = ShenandoahHeap::heap()->ref_processor();
243 shenandoah_assert_rp_isalive_installed();
244 } else {
245 rp = NULL;
246 }
247
248 // Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
249 // let's check here.
250 _cm->concurrent_scan_code_roots(worker_id, rp, _update_refs);
251 _cm->mark_loop(worker_id, _terminator, rp,
252 false, // not cancellable
253 false, // do not drain SATBs, already drained
254 _count_live,
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 case ShenandoahPhaseTimings::final_partial_gc_work:
314 update_code_cache = true;
315 break;
316 default:
317 ShouldNotReachHere();
318 }
319
320 ShenandoahHeap* heap = ShenandoahHeap::heap();
321
322 ShenandoahGCPhase phase(root_phase);
323
324 #if defined(COMPILER2) || INCLUDE_JVMCI
325 DerivedPointerTable::clear();
326 #endif
327
328 uint nworkers = heap->workers()->active_workers();
329
330 ShenandoahRootProcessor root_proc(heap, nworkers, root_phase);
331 ShenandoahUpdateRootsTask update_roots(&root_proc, update_code_cache);
332 heap->workers()->run_task(&update_roots);
333
334 #if defined(COMPILER2) || INCLUDE_JVMCI
335 DerivedPointerTable::update_pointers();
336 #endif
337 }
338
339 void ShenandoahConcurrentMark::initialize(uint workers) {
340 _heap = ShenandoahHeap::heap();
341
342 uint num_queues = MAX2(workers, 1U);
343
344 _task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
345
346 for (uint i = 0; i < num_queues; ++i) {
347 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
348 task_queue->initialize();
349 _task_queues->register_queue(i, task_queue);
350 }
351
352 ShenandoahBarrierSet::satb_mark_queue_set().set_buffer_size(ShenandoahSATBBufferSize);
353
354 size_t num_regions = ShenandoahHeap::heap()->num_regions();
355 _liveness_local = NEW_C_HEAP_ARRAY(jushort*, workers, mtGC);
356 for (uint worker = 0; worker < workers; worker++) {
357 _liveness_local[worker] = NEW_C_HEAP_ARRAY(jushort, num_regions, mtGC);
358 }
359 }
360
361 void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp, bool update_refs) {
362 if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
363 ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
364 if (!unload_classes()) {
365 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
366 if (update_refs) {
367 ShenandoahMarkResolveRefsClosure cl(q, rp);
368 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
369 CodeCache::blobs_do(&blobs);
370 } else {
371 ShenandoahMarkRefsClosure cl(q, rp);
372 CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
373 CodeCache::blobs_do(&blobs);
374 }
375 }
376 }
377 }
378
379 void ShenandoahConcurrentMark::mark_from_roots() {
380 ShenandoahHeap* sh = ShenandoahHeap::heap();
381 WorkGang* workers = sh->workers();
382 uint nworkers = workers->active_workers();
383
384 bool update_refs = sh->has_forwarded_objects();
385
386 ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
387
388 if (process_references()) {
389 ReferenceProcessor* rp = sh->ref_processor();
390 rp->set_active_mt_degree(nworkers);
391
392 // enable ("weak") refs discovery
393 rp->enable_discovery(true /*verify_no_refs*/);
394 rp->setup_policy(sh->is_full_gc_in_progress()); // snapshot the soft ref policy to be used in this cycle
395 }
396
397 shenandoah_assert_rp_isalive_not_installed();
398 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), sh->is_alive_closure());
399
400 task_queues()->reserve(nworkers);
401
402 if (UseShenandoahOWST) {
403 ShenandoahTaskTerminator terminator(nworkers, task_queues());
404 ShenandoahConcurrentMarkingTask markingTask = ShenandoahConcurrentMarkingTask(this, &terminator, update_refs);
405 workers->run_task(&markingTask);
406 } else {
407 ParallelTaskTerminator terminator(nworkers, task_queues());
408 ShenandoahConcurrentMarkingTask markingTask = ShenandoahConcurrentMarkingTask(this, &terminator, update_refs);
409 workers->run_task(&markingTask);
410 }
411
412 assert(task_queues()->is_empty() || sh->cancelled_concgc(), "Should be empty when not cancelled");
413 if (! sh->cancelled_concgc()) {
414 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
415 }
416
417 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
418 }
419
420 void ShenandoahConcurrentMark::finish_mark_from_roots() {
421 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
422
423 ShenandoahHeap* sh = ShenandoahHeap::heap();
424
425 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
426
427 shared_finish_mark_from_roots(/* full_gc = */ false);
428
429 if (sh->has_forwarded_objects()) {
430 update_roots(ShenandoahPhaseTimings::update_roots);
431 }
432
433 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
434 }
435
436 void ShenandoahConcurrentMark::shared_finish_mark_from_roots(bool full_gc) {
437 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
438
439 ShenandoahHeap* sh = ShenandoahHeap::heap();
440
441 uint nworkers = sh->workers()->active_workers();
442
443 // Finally mark everything else we've got in our queues during the previous steps.
444 // It does two different things for concurrent vs. mark-compact GC:
445 // - For concurrent GC, it starts with empty task queues, drains the remaining
446 // SATB buffers, and then completes the marking closure.
447 // - For mark-compact GC, it starts out with the task queues seeded by initial
448 // root scan, and completes the closure, thus marking through all live objects
449 // The implementation is the same, so it's shared here.
450 {
451 ShenandoahGCPhase phase(full_gc ?
452 ShenandoahPhaseTimings::full_gc_mark_finish_queues :
453 ShenandoahPhaseTimings::finish_queues);
454 bool count_live = !(ShenandoahNoLivenessFullGC && full_gc); // we do not need liveness data for full GC
455 task_queues()->reserve(nworkers);
456
457 shenandoah_assert_rp_isalive_not_installed();
458 ReferenceProcessorIsAliveMutator fix_isalive(sh->ref_processor(), sh->is_alive_closure());
459
460 StrongRootsScope scope(nworkers);
461 if (UseShenandoahOWST) {
462 ShenandoahTaskTerminator terminator(nworkers, task_queues());
463 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(), count_live,
464 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
465 sh->workers()->run_task(&task);
466 } else {
467 ParallelTaskTerminator terminator(nworkers, task_queues());
468 ShenandoahFinalMarkingTask task(this, &terminator, sh->has_forwarded_objects(), count_live,
469 unload_classes(), full_gc && ShenandoahStringDedup::is_enabled());
470 sh->workers()->run_task(&task);
471 }
472 }
473
474 assert(task_queues()->is_empty(), "Should be empty");
475
476 // When we're done marking everything, we process weak references.
477 if (process_references()) {
478 weak_refs_work(full_gc);
479 }
480
481 // And finally finish class unloading
482 if (unload_classes()) {
483 sh->unload_classes_and_cleanup_tables(full_gc);
484 }
485
486 assert(task_queues()->is_empty(), "Should be empty");
487
488 }
489
490 class ShenandoahSATBThreadsClosure : public ThreadClosure {
491 ShenandoahSATBBufferClosure* _satb_cl;
492 int _thread_parity;
493
494 public:
495 ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
496 _satb_cl(satb_cl),
497 _thread_parity(Threads::thread_claim_parity()) {}
498
499 void do_thread(Thread* thread) {
500 if (thread->is_Java_thread()) {
501 if (thread->claim_oops_do(true, _thread_parity)) {
502 JavaThread* jt = (JavaThread*)thread;
503 ShenandoahThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(_satb_cl);
504 }
505 } else if (thread->is_VM_thread()) {
506 if (thread->claim_oops_do(true, _thread_parity)) {
507 ShenandoahBarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(_satb_cl);
508 }
509 }
510 }
511 };
512
513 void ShenandoahConcurrentMark::drain_satb_buffers(uint worker_id, bool remark) {
514 ShenandoahObjToScanQueue* q = get_queue(worker_id);
515 ShenandoahSATBBufferClosure cl(q);
516
517 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
518 while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
519
520 if (remark) {
521 ShenandoahSATBThreadsClosure tc(&cl);
522 Threads::threads_do(&tc);
523 }
524 }
525
526 #if TASKQUEUE_STATS
527 void ShenandoahConcurrentMark::print_taskqueue_stats_hdr(outputStream* const st) {
528 st->print_raw_cr("GC Task Stats");
529 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
530 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
531 }
532
533 void ShenandoahConcurrentMark::print_taskqueue_stats() const {
534 if (!log_develop_is_enabled(Trace, gc, task, stats)) {
535 return;
536 }
537 Log(gc, task, stats) log;
538 ResourceMark rm;
539 LogStream ls(log.trace());
540 outputStream* st = &ls;
541 print_taskqueue_stats_hdr(st);
542
543 TaskQueueStats totals;
544 const uint n = _task_queues->size();
545 for (uint i = 0; i < n; ++i) {
546 st->print(UINT32_FORMAT_W(3), i);
547 _task_queues->queue(i)->stats.print(st);
548 st->cr();
549 totals += _task_queues->queue(i)->stats;
550 }
551 st->print("tot "); totals.print(st); st->cr();
552 DEBUG_ONLY(totals.verify());
553
554 }
555
556 void ShenandoahConcurrentMark::reset_taskqueue_stats() {
557 const uint n = task_queues()->size();
558 for (uint i = 0; i < n; ++i) {
559 task_queues()->queue(i)->stats.reset();
560 }
561 }
562 #endif // TASKQUEUE_STATS
563
564 // Weak Reference Closures
565 class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
566 uint _worker_id;
567 ParallelTaskTerminator* _terminator;
568 bool _reset_terminator;
569
570 public:
571 ShenandoahCMDrainMarkingStackClosure(uint worker_id, ParallelTaskTerminator* t, bool reset_terminator = false):
572 _worker_id(worker_id),
573 _terminator(t),
574 _reset_terminator(reset_terminator) {
575 }
576
577 void do_void() {
578 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
579
580 ShenandoahHeap* sh = ShenandoahHeap::heap();
581 ShenandoahConcurrentMark* scm = sh->concurrentMark();
582 assert(scm->process_references(), "why else would we be here?");
583 ReferenceProcessor* rp = sh->ref_processor();
584
585 shenandoah_assert_rp_isalive_installed();
586
587 scm->mark_loop(_worker_id, _terminator, rp,
588 false, // not cancellable
589 false, // do not drain SATBs
590 true, // count liveness
591 scm->unload_classes(),
592 sh->has_forwarded_objects());
593
594 if (_reset_terminator) {
595 _terminator->reset_for_reuse();
596 }
597 }
598 };
599
600
601 class ShenandoahCMKeepAliveClosure : public OopClosure {
602 private:
603 ShenandoahObjToScanQueue* _queue;
604 ShenandoahHeap* _heap;
605
606 template <class T>
607 inline void do_oop_nv(T* p) {
608 ShenandoahConcurrentMark::mark_through_ref<T, NONE, false /* string dedup */>(p, _heap, _queue);
609 }
610
611 public:
612 ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
613 _queue(q), _heap(ShenandoahHeap::heap()) {}
614
615 void do_oop(narrowOop* p) { do_oop_nv(p); }
616 void do_oop(oop* p) { do_oop_nv(p); }
617 };
618
619 class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
620 private:
621 ShenandoahObjToScanQueue* _queue;
622 ShenandoahHeap* _heap;
623
624 template <class T>
625 inline void do_oop_nv(T* p) {
626 ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, false /* string dedup */>(p, _heap, _queue);
627 }
628
629 public:
630 ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
631 _queue(q), _heap(ShenandoahHeap::heap()) {}
632
633 void do_oop(narrowOop* p) { do_oop_nv(p); }
634 void do_oop(oop* p) { do_oop_nv(p); }
635 };
636
637 class ShenandoahRefProcTaskProxy : public AbstractGangTask {
638
639 private:
640 AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
641 ParallelTaskTerminator* _terminator;
642 public:
643
644 ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
645 ParallelTaskTerminator* t) :
646 AbstractGangTask("Process reference objects in parallel"),
647 _proc_task(proc_task),
648 _terminator(t) {
649 }
650
651 void work(uint worker_id) {
652 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
653 ShenandoahHeap* heap = ShenandoahHeap::heap();
654 ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
655 if (heap->has_forwarded_objects()) {
656 ShenandoahForwardedIsAliveClosure is_alive;
657 ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
658 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
659 } else {
660 ShenandoahIsAliveClosure is_alive;
661 ShenandoahCMKeepAliveClosure keep_alive(heap->concurrentMark()->get_queue(worker_id));
662 _proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
663 }
664 }
665 };
666
667 class ShenandoahRefEnqueueTaskProxy : public AbstractGangTask {
668
669 private:
670 AbstractRefProcTaskExecutor::EnqueueTask& _enqueue_task;
671
672 public:
673
674 ShenandoahRefEnqueueTaskProxy(AbstractRefProcTaskExecutor::EnqueueTask& enqueue_task) :
675 AbstractGangTask("Enqueue reference objects in parallel"),
676 _enqueue_task(enqueue_task) {
677 }
678
679 void work(uint worker_id) {
680 _enqueue_task.work(worker_id);
681 }
682 };
683
684 class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
685
686 private:
687 WorkGang* _workers;
688
689 public:
690
691 ShenandoahRefProcTaskExecutor(WorkGang* workers) :
692 _workers(workers) {
693 }
694
695 // Executes a task using worker threads.
696 void execute(ProcessTask& task) {
697 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
698
699 // Shortcut execution if task is empty.
700 // This should be replaced with the generic ReferenceProcessor shortcut,
701 // see JDK-8181214, JDK-8043575, JDK-6938732.
702 if (task.is_empty()) {
703 return;
704 }
705
706 ShenandoahHeap* heap = ShenandoahHeap::heap();
707 ShenandoahConcurrentMark* cm = heap->concurrentMark();
708 uint nworkers = _workers->active_workers();
709 cm->task_queues()->reserve(nworkers);
710 if (UseShenandoahOWST) {
711 ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
712 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
713 _workers->run_task(&proc_task_proxy);
714 } else {
715 ParallelTaskTerminator terminator(nworkers, cm->task_queues());
716 ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
717 _workers->run_task(&proc_task_proxy);
718 }
719 }
720
721 void execute(EnqueueTask& task) {
722 ShenandoahRefEnqueueTaskProxy enqueue_task_proxy(task);
723 _workers->run_task(&enqueue_task_proxy);
724 }
725 };
726
727
728 void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
729 assert(process_references(), "sanity");
730
731 ShenandoahHeap* sh = ShenandoahHeap::heap();
732
733 ShenandoahPhaseTimings::Phase phase_root =
734 full_gc ?
735 ShenandoahPhaseTimings::full_gc_weakrefs :
736 ShenandoahPhaseTimings::weakrefs;
737
738 ShenandoahGCPhase phase(phase_root);
739
740 ReferenceProcessor* rp = sh->ref_processor();
741
742 // NOTE: We cannot shortcut on has_discovered_references() here, because
743 // we will miss marking JNI Weak refs then, see implementation in
744 // ReferenceProcessor::process_discovered_references.
745 weak_refs_work_doit(full_gc);
746
747 rp->verify_no_references_recorded();
748 assert(!rp->discovery_enabled(), "Post condition");
749
750 }
751
752 void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
753 ShenandoahHeap* sh = ShenandoahHeap::heap();
754
755 assert(!sh->is_concurrent_partial_in_progress(), "cannot process weakrefs during conc-partial yet");
756
757 ReferenceProcessor* rp = sh->ref_processor();
758
759 ShenandoahPhaseTimings::Phase phase_process =
760 full_gc ?
761 ShenandoahPhaseTimings::full_gc_weakrefs_process :
762 ShenandoahPhaseTimings::weakrefs_process;
763
764 ShenandoahPhaseTimings::Phase phase_enqueue =
765 full_gc ?
766 ShenandoahPhaseTimings::full_gc_weakrefs_enqueue :
767 ShenandoahPhaseTimings::weakrefs_enqueue;
768
769 shenandoah_assert_rp_isalive_not_installed();
770 ReferenceProcessorIsAliveMutator fix_isalive(rp, sh->is_alive_closure());
771
772 WorkGang* workers = sh->workers();
773 uint nworkers = workers->active_workers();
774
775 // Setup collector policy for softref cleaning.
776 bool clear_soft_refs = sh->soft_ref_policy()->use_should_clear_all_soft_refs(true /* bogus arg*/);
777 log_develop_debug(gc, ref)("clearing soft refs: %s", BOOL_TO_STR(clear_soft_refs));
778 rp->setup_policy(clear_soft_refs);
779 rp->set_active_mt_degree(nworkers);
780
781 assert(task_queues()->is_empty(), "Should be empty");
782
783 // complete_gc and keep_alive closures instantiated here are only needed for
784 // single-threaded path in RP. They share the queue 0 for tracking work, which
785 // simplifies implementation. Since RP may decide to call complete_gc several
786 // times, we need to be able to reuse the terminator.
787 uint serial_worker_id = 0;
788 ParallelTaskTerminator terminator(1, task_queues());
789 ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
790
791 ShenandoahRefProcTaskExecutor executor(workers);
792
793 ReferenceProcessorPhaseTimes pt(sh->gc_timer(), rp->num_q());
794
795 {
796 ShenandoahGCPhase phase(phase_process);
797
798 if (sh->has_forwarded_objects()) {
799 ShenandoahForwardedIsAliveClosure is_alive;
800 ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
801 rp->process_discovered_references(&is_alive, &keep_alive,
802 &complete_gc, &executor,
803 &pt);
804
805 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
806 } else {
807 ShenandoahIsAliveClosure is_alive;
808 ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
809 rp->process_discovered_references(&is_alive, &keep_alive,
810 &complete_gc, &executor,
811 &pt);
812
813 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
814 }
815 pt.print_all_references();
816
817 assert(task_queues()->is_empty(), "Should be empty");
818 }
819
820 {
821 ShenandoahGCPhase phase(phase_enqueue);
822 rp->enqueue_discovered_references(&executor, &pt);
823 pt.print_enqueue_phase();
824 }
825 }
826
827 class ShenandoahCancelledGCYieldClosure : public YieldClosure {
828 private:
829 ShenandoahHeap* const _heap;
830 public:
831 ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
832 virtual bool should_return() { return _heap->cancelled_concgc(); }
833 };
834
835 class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
836 public:
837 void do_void() {
838 ShenandoahHeap* sh = ShenandoahHeap::heap();
839 ShenandoahConcurrentMark* scm = sh->concurrentMark();
840 assert(scm->process_references(), "why else would we be here?");
841 ParallelTaskTerminator terminator(1, scm->task_queues());
842
843 ReferenceProcessor* rp = sh->ref_processor();
844 shenandoah_assert_rp_isalive_installed();
845
846 scm->mark_loop(0, &terminator, rp,
847 false, // not cancellable
848 true, // drain SATBs
849 true, // count liveness
850 scm->unload_classes(),
851 sh->has_forwarded_objects());
852 }
853 };
854
855 class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
856 private:
857 ShenandoahObjToScanQueue* _queue;
858 ShenandoahHeap* _heap;
859
860 template <class T>
861 inline void do_oop_nv(T* p) {
862 ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, false /* string dedup */>(p, _heap, _queue);
863 }
864
865 public:
866 ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
867 _queue(q), _heap(ShenandoahHeap::heap()) {}
868
869 void do_oop(narrowOop* p) { do_oop_nv(p); }
870 void do_oop(oop* p) { do_oop_nv(p); }
871 };
872
873 void ShenandoahConcurrentMark::preclean_weak_refs() {
874 // Pre-cleaning weak references before diving into STW makes sense at the
875 // end of concurrent mark. This will filter out the references which referents
876 // are alive. Note that ReferenceProcessor already filters out these on reference
877 // discovery, and the bulk of work is done here. This phase processes leftovers
878 // that missed the initial filtering, i.e. when referent was marked alive after
879 // reference was discovered by RP.
880
881 assert(process_references(), "sanity");
882
883 ShenandoahHeap* sh = ShenandoahHeap::heap();
884 ReferenceProcessor* rp = sh->ref_processor();
885
886 // Shortcut if no references were discovered to avoid winding up threads.
887 if (!rp->has_discovered_references()) {
888 return;
889 }
890
891 ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
892
893 shenandoah_assert_rp_isalive_not_installed();
894 ReferenceProcessorIsAliveMutator fix_isalive(rp, sh->is_alive_closure());
895
896 // Interrupt on cancelled GC
897 ShenandoahCancelledGCYieldClosure yield;
898
899 assert(task_queues()->is_empty(), "Should be empty");
900
901 ShenandoahPrecleanCompleteGCClosure complete_gc;
902 if (sh->has_forwarded_objects()) {
903 ShenandoahForwardedIsAliveClosure is_alive;
904 ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(get_queue(0));
905 ResourceMark rm;
906 rp->preclean_discovered_references(&is_alive, &keep_alive,
907 &complete_gc, &yield,
908 NULL);
909 } else {
910 ShenandoahIsAliveClosure is_alive;
911 ShenandoahCMKeepAliveClosure keep_alive(get_queue(0));
912 ResourceMark rm;
913 rp->preclean_discovered_references(&is_alive, &keep_alive,
914 &complete_gc, &yield,
915 NULL);
916 }
917
918 assert(task_queues()->is_empty(), "Should be empty");
919 }
920
921 void ShenandoahConcurrentMark::cancel() {
922 // Clean up marking stacks.
923 ShenandoahObjToScanQueueSet* queues = task_queues();
924 queues->clear();
925
926 // Cancel SATB buffers.
927 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
928 }
929
930 ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
931 assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
932 return _task_queues->queue(worker_id);
933 }
934
935 void ShenandoahConcurrentMark::clear_queue(ShenandoahObjToScanQueue *q) {
936 q->set_empty();
937 q->overflow_stack()->clear();
938 q->clear_buffer();
939 }
940
941 template <bool CANCELLABLE, bool DRAIN_SATB, bool COUNT_LIVENESS>
942 void ShenandoahConcurrentMark::mark_loop_prework(uint w, ParallelTaskTerminator *t, ReferenceProcessor *rp, bool class_unload, bool update_refs, bool strdedup) {
943 ShenandoahObjToScanQueue* q = get_queue(w);
944
945 jushort* ld;
946 if (COUNT_LIVENESS) {
947 ld = get_liveness(w);
948 Copy::fill_to_bytes(ld, _heap->num_regions() * sizeof(jushort));
949 } else {
950 ld = NULL;
951 }
952
953 // TODO: We can clean up this if we figure out how to do templated oop closures that
954 // play nice with specialized_oop_iterators.
955 if (class_unload) {
956 if (update_refs) {
957 if (strdedup) {
958 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
959 ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, dq, rp);
960 mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
961 } else {
962 ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
963 mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
964 }
965 } else {
966 if (strdedup) {
967 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
968 ShenandoahMarkRefsMetadataDedupClosure cl(q, dq, rp);
969 mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
970 } else {
971 ShenandoahMarkRefsMetadataClosure cl(q, rp);
972 mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
973 }
974 }
975 } else {
976 if (update_refs) {
977 if (strdedup) {
978 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
979 ShenandoahMarkUpdateRefsDedupClosure cl(q, dq, rp);
980 mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
981 } else {
982 ShenandoahMarkUpdateRefsClosure cl(q, rp);
983 mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
984 }
985 } else {
986 if (strdedup) {
987 ShenandoahStrDedupQueue* dq = ShenandoahStringDedup::queue(w);
988 ShenandoahMarkRefsDedupClosure cl(q, dq, rp);
989 mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
990 } else {
991 ShenandoahMarkRefsClosure cl(q, rp);
992 mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE, DRAIN_SATB, COUNT_LIVENESS>(&cl, ld, w, t);
993 }
994 }
995 }
996 if (COUNT_LIVENESS) {
997 for (uint i = 0; i < _heap->num_regions(); i++) {
998 ShenandoahHeapRegion* r = _heap->get_region(i);
999 jushort live = ld[i];
1000 if (live > 0) {
1001 r->increase_live_data_gc_words(live);
1002 }
1003 }
1004 }
1005 }
1006
1007 template <class T, bool CANCELLABLE, bool DRAIN_SATB, bool COUNT_LIVENESS>
1008 void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator *terminator) {
1009 int seed = 17;
1010 uintx stride = CANCELLABLE ? ShenandoahMarkLoopStride : 1;
1011
1012 ShenandoahHeap* heap = ShenandoahHeap::heap();
1013 ShenandoahObjToScanQueueSet* queues = task_queues();
1014 ShenandoahObjToScanQueue* q;
1015 ShenandoahMarkTask t;
1016
1017 /*
1018 * Process outstanding queues, if any.
1019 *
1020 * There can be more queues than workers. To deal with the imbalance, we claim
1021 * extra queues first. Since marking can push new tasks into the queue associated
1022 * with this worker id, we come back to process this queue in the normal loop.
1023 */
1024 assert(queues->get_reserved() == heap->workers()->active_workers(),
1025 "Need to reserve proper number of queues");
1026
1027 q = queues->claim_next();
1028 while (q != NULL) {
1029 if (CANCELLABLE && heap->check_cancelled_concgc_and_yield()) {
1030 ShenandoahCancelledTerminatorTerminator tt;
1031 while (!terminator->offer_termination(&tt));
1032 return;
1033 }
1034
1035 for (uint i = 0; i < stride; i++) {
1036 if (try_queue(q, t)) {
1037 do_task<T, COUNT_LIVENESS>(q, cl, live_data, &t);
1038 } else {
1039 assert(q->is_empty(), "Must be empty");
1040 q = queues->claim_next();
1041 break;
1042 }
1043 }
1044 }
1045 q = get_queue(worker_id);
1046
1047 /*
1048 * Normal marking loop:
1049 */
1050 while (true) {
1051 if (CANCELLABLE && heap->check_cancelled_concgc_and_yield()) {
1052 ShenandoahCancelledTerminatorTerminator tt;
1053 while (!terminator->offer_termination(&tt));
1054 return;
1055 }
1056
1057 for (uint i = 0; i < stride; i++) {
1058 if (try_queue(q, t) ||
1059 (DRAIN_SATB && try_draining_satb_buffer(q, t)) ||
1060 queues->steal(worker_id, &seed, t)) {
1061 do_task<T, COUNT_LIVENESS>(q, cl, live_data, &t);
1062 } else {
1063 // Need to leave the STS here otherwise it might block safepoints.
1064 SuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
1065 if (terminator->offer_termination()) return;
1066 }
1067 }
1068 }
1069 }
1070
1071 bool ShenandoahConcurrentMark::process_references() const {
1072 return _heap->process_references();
1073 }
1074
1075 bool ShenandoahConcurrentMark::unload_classes() const {
1076 return _heap->unload_classes();
1077 }
1078
1079 bool ShenandoahConcurrentMark::claim_codecache() {
1080 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1081 return _claimed_codecache.try_set();
1082 }
1083
1084 void ShenandoahConcurrentMark::clear_claim_codecache() {
1085 assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
1086 _claimed_codecache.unset();
1087 }
1088
1089 jushort* ShenandoahConcurrentMark::get_liveness(uint worker_id) {
1090 return _liveness_local[worker_id];
1091 }
1092
1093 // Generate Shenandoah specialized oop_oop_iterate functions.
1094 SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_SHENANDOAH(ALL_KLASS_OOP_OOP_ITERATE_DEFN)