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