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/shenandoahHeap.inline.hpp"
34 #include "gc/shenandoah/shenandoahMark.inline.hpp"
35 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
36 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
37 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
38 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
39 #include "gc/shenandoah/shenandoahStringDedup.hpp"
40 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
41 #include "gc/shenandoah/shenandoahUtils.hpp"
42 #include "memory/iterator.inline.hpp"
43 #include "memory/resourceArea.hpp"
44 #include "runtime/continuation.hpp"
45 #include "runtime/threads.hpp"
46
47 class ShenandoahConcurrentMarkingTask : public WorkerTask {
48 private:
49 ShenandoahConcurrentMark* const _cm;
50 TaskTerminator* const _terminator;
51
52 public:
53 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
54 WorkerTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
55 }
56
57 void work(uint worker_id) {
58 ShenandoahHeap* heap = ShenandoahHeap::heap();
59 ShenandoahConcurrentWorkerSession worker_session(worker_id);
60 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
61 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
62 ShenandoahReferenceProcessor* rp = heap->ref_processor();
63 assert(rp != NULL, "need reference processor");
64 StringDedup::Requests requests;
65 _cm->mark_loop(worker_id, _terminator, rp,
66 true /*cancellable*/,
67 ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
68 &requests);
69 }
70 };
71
72 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
73 private:
74 SATBMarkQueueSet& _satb_qset;
75 OopClosure* const _cl;
76 uintx _claim_token;
77
78 public:
79 ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
80 _satb_qset(satb_qset),
81 _cl(cl),
82 _claim_token(Threads::thread_claim_token()) {}
83
84 void do_thread(Thread* thread) {
85 if (thread->claim_threads_do(true, _claim_token)) {
86 // Transfer any partial buffer to the qset for completed buffer processing.
87 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
88 if (thread->is_Java_thread()) {
89 if (_cl != NULL) {
90 ResourceMark rm;
91 thread->oops_do(_cl, NULL);
92 }
93 }
94 }
95 }
96 };
97
98 class ShenandoahFinalMarkingTask : public WorkerTask {
99 private:
100 ShenandoahConcurrentMark* _cm;
101 TaskTerminator* _terminator;
102 bool _dedup_string;
103
104 public:
105 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
106 WorkerTask("Shenandoah Final Mark"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
107 }
108
109 void work(uint worker_id) {
110 ShenandoahHeap* heap = ShenandoahHeap::heap();
111
112 ShenandoahParallelWorkerSession worker_session(worker_id);
113 ShenandoahReferenceProcessor* rp = heap->ref_processor();
114 StringDedup::Requests requests;
115
116 // First drain remaining SATB buffers.
117 {
118 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
119
120 ShenandoahSATBBufferClosure cl(q);
121 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
122 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
123 assert(!heap->has_forwarded_objects(), "Not expected");
124
125 ShenandoahMarkRefsClosure mark_cl(q, rp);
126 ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
127 ShenandoahIUBarrier ? &mark_cl : NULL);
128 Threads::threads_do(&tc);
129 }
130 _cm->mark_loop(worker_id, _terminator, rp,
131 false /*not cancellable*/,
132 _dedup_string ? ENQUEUE_DEDUP : NO_DEDUP,
133 &requests);
134 assert(_cm->task_queues()->is_empty(), "Should be empty");
135 }
136 };
137
138 ShenandoahConcurrentMark::ShenandoahConcurrentMark() :
139 ShenandoahMark() {}
140
141 // Mark concurrent roots during concurrent phases
142 class ShenandoahMarkConcurrentRootsTask : public WorkerTask {
143 private:
144 SuspendibleThreadSetJoiner _sts_joiner;
145 ShenandoahConcurrentRootScanner _root_scanner;
146 ShenandoahObjToScanQueueSet* const _queue_set;
147 ShenandoahReferenceProcessor* const _rp;
148
149 public:
150 ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
151 ShenandoahReferenceProcessor* rp,
152 ShenandoahPhaseTimings::Phase phase,
153 uint nworkers);
154 void work(uint worker_id);
155 };
156
157 ShenandoahMarkConcurrentRootsTask::ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
158 ShenandoahReferenceProcessor* rp,
159 ShenandoahPhaseTimings::Phase phase,
160 uint nworkers) :
161 WorkerTask("Shenandoah Concurrent Mark Roots"),
162 _root_scanner(nworkers, phase),
163 _queue_set(qs),
164 _rp(rp) {
165 assert(!ShenandoahHeap::heap()->has_forwarded_objects(), "Not expected");
166 }
167
168 void ShenandoahMarkConcurrentRootsTask::work(uint worker_id) {
169 ShenandoahConcurrentWorkerSession worker_session(worker_id);
170 ShenandoahObjToScanQueue* q = _queue_set->queue(worker_id);
171 ShenandoahMarkRefsClosure cl(q, _rp);
172 _root_scanner.roots_do(&cl, worker_id);
173 }
174
175 void ShenandoahConcurrentMark::mark_concurrent_roots() {
176 ShenandoahHeap* const heap = ShenandoahHeap::heap();
177 assert(!heap->has_forwarded_objects(), "Not expected");
178
179 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
180
181 WorkerThreads* workers = heap->workers();
182 ShenandoahReferenceProcessor* rp = heap->ref_processor();
183 task_queues()->reserve(workers->active_workers());
184 ShenandoahMarkConcurrentRootsTask task(task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
185
186 workers->run_task(&task);
187 }
188
189 class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
190 private:
191 SATBMarkQueueSet& _qset;
192 public:
193 ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
194 HandshakeClosure("Shenandoah Flush SATB Handshake"),
195 _qset(qset) {}
196
197 void do_thread(Thread* thread) {
198 _qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
199 }
200 };
201
202 void ShenandoahConcurrentMark::concurrent_mark() {
203 ShenandoahHeap* const heap = ShenandoahHeap::heap();
204 WorkerThreads* workers = heap->workers();
205 uint nworkers = workers->active_workers();
206 task_queues()->reserve(nworkers);
207
208 ShenandoahSATBMarkQueueSet& qset = ShenandoahBarrierSet::satb_mark_queue_set();
209 ShenandoahFlushSATBHandshakeClosure flush_satb(qset);
210 for (uint flushes = 0; flushes < ShenandoahMaxSATBBufferFlushes; flushes++) {
211 TaskTerminator terminator(nworkers, task_queues());
212 ShenandoahConcurrentMarkingTask task(this, &terminator);
213 workers->run_task(&task);
214
215 if (heap->cancelled_gc()) {
216 // GC is cancelled, break out.
217 break;
218 }
219
220 size_t before = qset.completed_buffers_num();
221 Handshake::execute(&flush_satb);
222 size_t after = qset.completed_buffers_num();
223
224 if (before == after) {
225 // No more retries needed, break out.
226 break;
227 }
228 }
229 assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
230 }
231
232 void ShenandoahConcurrentMark::finish_mark() {
233 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
234 assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
235 finish_mark_work();
236 assert(task_queues()->is_empty(), "Should be empty");
237 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
238 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
239
240 ShenandoahHeap* const heap = ShenandoahHeap::heap();
241 heap->set_concurrent_mark_in_progress(false);
242 heap->mark_complete_marking_context();
243
244 end_mark();
245 }
246
247 void ShenandoahConcurrentMark::finish_mark_work() {
248 // Finally mark everything else we've got in our queues during the previous steps.
249 // It does two different things for concurrent vs. mark-compact GC:
250 // - For concurrent GC, it starts with empty task queues, drains the remaining
251 // SATB buffers, and then completes the marking closure.
252 // - For mark-compact GC, it starts out with the task queues seeded by initial
253 // root scan, and completes the closure, thus marking through all live objects
254 // The implementation is the same, so it's shared here.
255 ShenandoahHeap* const heap = ShenandoahHeap::heap();
256 ShenandoahGCPhase phase(ShenandoahPhaseTimings::finish_mark);
257 uint nworkers = heap->workers()->active_workers();
258 task_queues()->reserve(nworkers);
259
260 StrongRootsScope scope(nworkers);
261 TaskTerminator terminator(nworkers, task_queues());
262 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
263 heap->workers()->run_task(&task);
264
265 assert(task_queues()->is_empty(), "Should be empty");
266 }
267
268
269 void ShenandoahConcurrentMark::cancel() {
270 clear();
271 ShenandoahReferenceProcessor* rp = ShenandoahHeap::heap()->ref_processor();
272 rp->abandon_partial_discovery();
273 }