1 /*
2 * Copyright (c) 2013, 2021, Red Hat, Inc. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "gc/shared/satbMarkQueue.hpp"
28 #include "gc/shared/strongRootsScope.hpp"
29 #include "gc/shared/taskTerminator.hpp"
30 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
31 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
32 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
33 #include "gc/shenandoah/shenandoahGeneration.hpp"
34 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
35 #include "gc/shenandoah/shenandoahMark.inline.hpp"
36 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
37 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
38 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
39 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
40 #include "gc/shenandoah/shenandoahStringDedup.hpp"
41 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
42 #include "gc/shenandoah/shenandoahUtils.hpp"
43 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
44 #include "memory/iterator.inline.hpp"
45 #include "memory/resourceArea.hpp"
46 #include "runtime/continuation.hpp"
47 #include "runtime/threads.hpp"
48
49 template <GenerationMode GENERATION>
50 class ShenandoahConcurrentMarkingTask : public WorkerTask {
51 private:
52 ShenandoahConcurrentMark* const _cm;
53 TaskTerminator* const _terminator;
54
55 public:
56 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
57 WorkerTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
58 }
59
60 void work(uint worker_id) {
61 ShenandoahHeap* heap = ShenandoahHeap::heap();
62 ShenandoahParallelWorkerSession worker_session(worker_id);
63 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_mark, ShenandoahPhaseTimings::ParallelMark, worker_id, true);
64 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
65 ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
66 assert(rp != NULL, "need reference processor");
67 StringDedup::Requests requests;
68 _cm->mark_loop(GENERATION, worker_id, _terminator, rp,
69 true /*cancellable*/,
70 ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
71 &requests);
72 }
73 };
74
75 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
76 private:
77 SATBMarkQueueSet& _satb_qset;
78 OopClosure* const _cl;
79 uintx _claim_token;
80
81 public:
82 ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
83 _satb_qset(satb_qset),
84 _cl(cl),
85 _claim_token(Threads::thread_claim_token()) {}
86
87 void do_thread(Thread* thread) {
88 if (thread->claim_threads_do(true, _claim_token)) {
89 // Transfer any partial buffer to the qset for completed buffer processing.
90 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
91 if (thread->is_Java_thread()) {
92 if (_cl != NULL) {
93 ResourceMark rm;
94 thread->oops_do(_cl, NULL);
95 }
96 }
97 }
98 }
99 };
100
101 template<GenerationMode GENERATION>
102 class ShenandoahFinalMarkingTask : public WorkerTask {
103 private:
104 ShenandoahConcurrentMark* _cm;
105 TaskTerminator* _terminator;
106 bool _dedup_string;
107
108 public:
109 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
110 WorkerTask("Shenandoah Final Mark"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
111 }
112
113 void work(uint worker_id) {
114 ShenandoahHeap* heap = ShenandoahHeap::heap();
115
116 ShenandoahParallelWorkerSession worker_session(worker_id);
117 StringDedup::Requests requests;
118 ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
119
120 // First drain remaining SATB buffers.
121 {
122 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
123 ShenandoahObjToScanQueue* old = _cm->get_old_queue(worker_id);
124
125 ShenandoahSATBBufferClosure<GENERATION> cl(q, old);
126 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
127 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
128 assert(!heap->has_forwarded_objects(), "Not expected");
129
130 ShenandoahMarkRefsClosure<GENERATION> mark_cl(q, rp, old);
131 ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
132 ShenandoahIUBarrier ? &mark_cl : NULL);
133 Threads::threads_do(&tc);
134 }
135 _cm->mark_loop(GENERATION, worker_id, _terminator, rp,
136 false /*not cancellable*/,
137 _dedup_string ? ENQUEUE_DEDUP : NO_DEDUP,
138 &requests);
139 assert(_cm->task_queues()->is_empty(), "Should be empty");
140 }
141 };
142
143 ShenandoahConcurrentMark::ShenandoahConcurrentMark(ShenandoahGeneration* generation) :
144 ShenandoahMark(generation) {}
145
146 // Mark concurrent roots during concurrent phases
147 template<GenerationMode GENERATION>
148 class ShenandoahMarkConcurrentRootsTask : public WorkerTask {
149 private:
150 SuspendibleThreadSetJoiner _sts_joiner;
151 ShenandoahConcurrentRootScanner _root_scanner;
152 ShenandoahObjToScanQueueSet* const _queue_set;
153 ShenandoahObjToScanQueueSet* const _old_queue_set;
154 ShenandoahReferenceProcessor* const _rp;
155
156 public:
157 ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
158 ShenandoahObjToScanQueueSet* old,
159 ShenandoahReferenceProcessor* rp,
160 ShenandoahPhaseTimings::Phase phase,
161 uint nworkers);
162 void work(uint worker_id);
163 };
164
165 template<GenerationMode GENERATION>
166 ShenandoahMarkConcurrentRootsTask<GENERATION>::ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
167 ShenandoahObjToScanQueueSet* old,
168 ShenandoahReferenceProcessor* rp,
169 ShenandoahPhaseTimings::Phase phase,
170 uint nworkers) :
171 WorkerTask("Shenandoah Concurrent Mark Roots"),
172 _root_scanner(nworkers, phase),
173 _queue_set(qs),
174 _old_queue_set(old),
175 _rp(rp) {
176 assert(!ShenandoahHeap::heap()->has_forwarded_objects(), "Not expected");
177 }
178
179 template<GenerationMode GENERATION>
180 void ShenandoahMarkConcurrentRootsTask<GENERATION>::work(uint worker_id) {
181 ShenandoahConcurrentWorkerSession worker_session(worker_id);
182 ShenandoahObjToScanQueue* q = _queue_set->queue(worker_id);
183 ShenandoahObjToScanQueue* old = _old_queue_set == NULL ? NULL : _old_queue_set->queue(worker_id);
184 ShenandoahMarkRefsClosure<GENERATION> cl(q, _rp, old);
185 _root_scanner.roots_do(&cl, worker_id);
186 }
187
188 void ShenandoahConcurrentMark::mark_concurrent_roots() {
189 ShenandoahHeap* const heap = ShenandoahHeap::heap();
190 assert(!heap->has_forwarded_objects(), "Not expected");
191
192 WorkerThreads* workers = heap->workers();
193 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
194 _generation->reserve_task_queues(workers->active_workers());
195 switch (_generation->generation_mode()) {
196 case YOUNG: {
197 ShenandoahMarkConcurrentRootsTask<YOUNG> task(task_queues(), old_task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
198 workers->run_task(&task);
199 break;
200 }
201 case GLOBAL: {
202 assert(old_task_queues() == NULL, "Global mark should not have old gen mark queues.");
203 ShenandoahMarkConcurrentRootsTask<GLOBAL> task(task_queues(), old_task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
204 workers->run_task(&task);
205 break;
206 }
207 default:
208 // Intentionally haven't added OLD here. We use a YOUNG generation
209 // cycle to bootstrap concurrent old marking.
210 ShouldNotReachHere();
211 }
212 }
213
214 class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
215 private:
216 SATBMarkQueueSet& _qset;
217 public:
218 ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
219 HandshakeClosure("Shenandoah Flush SATB Handshake"),
220 _qset(qset) {}
221
222 void do_thread(Thread* thread) {
223 _qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
224 }
225 };
226
227 void ShenandoahConcurrentMark::concurrent_mark() {
228 ShenandoahHeap* const heap = ShenandoahHeap::heap();
229 WorkerThreads* workers = heap->workers();
230 uint nworkers = workers->active_workers();
231 task_queues()->reserve(nworkers);
232
233 ShenandoahSATBMarkQueueSet& qset = ShenandoahBarrierSet::satb_mark_queue_set();
234 ShenandoahFlushSATBHandshakeClosure flush_satb(qset);
235 for (uint flushes = 0; flushes < ShenandoahMaxSATBBufferFlushes; flushes++) {
236 switch (_generation->generation_mode()) {
237 case YOUNG: {
238 TaskTerminator terminator(nworkers, task_queues());
239 ShenandoahConcurrentMarkingTask<YOUNG> task(this, &terminator);
240 workers->run_task(&task);
241 break;
242 }
243 case OLD: {
244 TaskTerminator terminator(nworkers, task_queues());
245 ShenandoahConcurrentMarkingTask<OLD> task(this, &terminator);
246 workers->run_task(&task);
247 break;
248 }
249 case GLOBAL: {
250 TaskTerminator terminator(nworkers, task_queues());
251 ShenandoahConcurrentMarkingTask<GLOBAL> task(this, &terminator);
252 workers->run_task(&task);
253 break;
254 }
255 default:
256 ShouldNotReachHere();
257 }
258
259 if (heap->cancelled_gc()) {
260 // GC is cancelled, break out.
261 break;
262 }
263
264 size_t before = qset.completed_buffers_num();
265 Handshake::execute(&flush_satb);
266 size_t after = qset.completed_buffers_num();
267
268 if (before == after) {
269 // No more retries needed, break out.
270 break;
271 }
272 }
273 assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
274 }
275
276 void ShenandoahConcurrentMark::finish_mark() {
277 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
278 assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
279 finish_mark_work();
280 assert(task_queues()->is_empty(), "Should be empty");
281 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
282 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
283
284 _generation->set_concurrent_mark_in_progress(false);
285 _generation->set_mark_complete();
286
287 end_mark();
288 }
289
290 void ShenandoahConcurrentMark::finish_mark_work() {
291 // Finally mark everything else we've got in our queues during the previous steps.
292 // It does two different things for concurrent vs. mark-compact GC:
293 // - For concurrent GC, it starts with empty task queues, drains the remaining
294 // SATB buffers, and then completes the marking closure.
295 // - For mark-compact GC, it starts out with the task queues seeded by initial
296 // root scan, and completes the closure, thus marking through all live objects
297 // The implementation is the same, so it's shared here.
298 ShenandoahHeap* const heap = ShenandoahHeap::heap();
299 ShenandoahGCPhase phase(ShenandoahPhaseTimings::finish_mark);
300 uint nworkers = heap->workers()->active_workers();
301 task_queues()->reserve(nworkers);
302
303 StrongRootsScope scope(nworkers);
304 TaskTerminator terminator(nworkers, task_queues());
305
306 switch (_generation->generation_mode()) {
307 case YOUNG:{
308 ShenandoahFinalMarkingTask<YOUNG> task(this, &terminator, ShenandoahStringDedup::is_enabled());
309 heap->workers()->run_task(&task);
310 break;
311 }
312 case OLD:{
313 ShenandoahFinalMarkingTask<OLD> task(this, &terminator, ShenandoahStringDedup::is_enabled());
314 heap->workers()->run_task(&task);
315 break;
316 }
317 case GLOBAL:{
318 ShenandoahFinalMarkingTask<GLOBAL> task(this, &terminator, ShenandoahStringDedup::is_enabled());
319 heap->workers()->run_task(&task);
320 break;
321 }
322 default:
323 ShouldNotReachHere();
324 }
325
326
327 assert(task_queues()->is_empty(), "Should be empty");
328 }