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