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
45 class ShenandoahUpdateRootsTask : public AbstractGangTask {
46 private:
47 ShenandoahRootUpdater* _root_updater;
48 bool _check_alive;
49 public:
50 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater, bool check_alive) :
51 AbstractGangTask("Shenandoah Update Roots"),
52 _root_updater(root_updater),
53 _check_alive(check_alive){
54 }
55
56 void work(uint worker_id) {
57 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
58 ShenandoahParallelWorkerSession worker_session(worker_id);
59
60 ShenandoahHeap* heap = ShenandoahHeap::heap();
61 ShenandoahUpdateRefsClosure cl;
62 if (_check_alive) {
63 ShenandoahForwardedIsAliveClosure is_alive;
64 _root_updater->roots_do<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>(worker_id, &is_alive, &cl);
65 } else {
66 AlwaysTrueClosure always_true;;
67 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
68 }
69 }
70 };
71
72 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
73 private:
74 ShenandoahConcurrentMark* const _cm;
75 TaskTerminator* const _terminator;
76
77 public:
78 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
79 AbstractGangTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
80 }
81
82 void work(uint worker_id) {
83 ShenandoahHeap* heap = ShenandoahHeap::heap();
84 ShenandoahConcurrentWorkerSession worker_session(worker_id);
85 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
86 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
87 ShenandoahReferenceProcessor* rp = heap->ref_processor();
88 assert(rp != NULL, "need reference processor");
89 StringDedup::Requests requests;
90 _cm->mark_loop(worker_id, _terminator, rp,
91 true /*cancellable*/,
92 ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
93 &requests);
94 }
95 };
96
97 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
98 private:
99 SATBMarkQueueSet& _satb_qset;
100 OopClosure* const _cl;
101 uintx _claim_token;
102
103 public:
104 ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
105 _satb_qset(satb_qset),
106 _cl(cl),
107 _claim_token(Threads::thread_claim_token()) {}
108
109 void do_thread(Thread* thread) {
110 if (thread->claim_threads_do(true, _claim_token)) {
111 // Transfer any partial buffer to the qset for completed buffer processing.
112 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
113 if (thread->is_Java_thread()) {
114 if (_cl != NULL) {
115 ResourceMark rm;
116 thread->oops_do(_cl, NULL);
117 }
118 }
119 }
120 }
121 };
122
123 class ShenandoahFinalMarkingTask : public AbstractGangTask {
124 private:
125 ShenandoahConcurrentMark* _cm;
126 TaskTerminator* _terminator;
127 bool _dedup_string;
128
129 public:
130 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
131 AbstractGangTask("Shenandoah Final Mark"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
132 }
133
134 void work(uint worker_id) {
135 ShenandoahHeap* heap = ShenandoahHeap::heap();
136
137 ShenandoahParallelWorkerSession worker_session(worker_id);
138 ShenandoahReferenceProcessor* rp = heap->ref_processor();
139 StringDedup::Requests requests;
140
141 // First drain remaining SATB buffers.
142 {
143 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
144
145 ShenandoahSATBBufferClosure cl(q);
146 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
147 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
148 assert(!heap->has_forwarded_objects(), "Not expected");
149
150 ShenandoahMarkRefsClosure mark_cl(q, rp);
151 ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
152 ShenandoahIUBarrier ? &mark_cl : NULL);
153 Threads::threads_do(&tc);
154 }
155 _cm->mark_loop(worker_id, _terminator, rp,
156 false /*not cancellable*/,
157 _dedup_string ? ENQUEUE_DEDUP : NO_DEDUP,
158 &requests);
159 assert(_cm->task_queues()->is_empty(), "Should be empty");
160 }
161 };
162
163 ShenandoahConcurrentMark::ShenandoahConcurrentMark() :
164 ShenandoahMark() {}
165
166 // Mark concurrent roots during concurrent phases
167 class ShenandoahMarkConcurrentRootsTask : public AbstractGangTask {
168 private:
169 SuspendibleThreadSetJoiner _sts_joiner;
170 ShenandoahConcurrentRootScanner _root_scanner;
171 ShenandoahObjToScanQueueSet* const _queue_set;
172 ShenandoahReferenceProcessor* const _rp;
173
174 public:
175 ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
176 ShenandoahReferenceProcessor* rp,
177 ShenandoahPhaseTimings::Phase phase,
178 uint nworkers);
179 void work(uint worker_id);
180 };
181
182 ShenandoahMarkConcurrentRootsTask::ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
183 ShenandoahReferenceProcessor* rp,
184 ShenandoahPhaseTimings::Phase phase,
185 uint nworkers) :
186 AbstractGangTask("Shenandoah Concurrent Mark Roots"),
187 _root_scanner(nworkers, phase),
188 _queue_set(qs),
189 _rp(rp) {
190 assert(!ShenandoahHeap::heap()->has_forwarded_objects(), "Not expected");
191 }
192
193 void ShenandoahMarkConcurrentRootsTask::work(uint worker_id) {
194 ShenandoahConcurrentWorkerSession worker_session(worker_id);
195 ShenandoahObjToScanQueue* q = _queue_set->queue(worker_id);
196 ShenandoahMarkRefsClosure cl(q, _rp);
197 _root_scanner.roots_do(&cl, worker_id);
198 }
199
200 void ShenandoahConcurrentMark::mark_concurrent_roots() {
201 ShenandoahHeap* const heap = ShenandoahHeap::heap();
202 assert(!heap->has_forwarded_objects(), "Not expected");
203
204 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
205
206 WorkGang* workers = heap->workers();
207 ShenandoahReferenceProcessor* rp = heap->ref_processor();
208 task_queues()->reserve(workers->active_workers());
209 ShenandoahMarkConcurrentRootsTask task(task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
210
211 workers->run_task(&task);
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 WorkGang* 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 TaskTerminator terminator(nworkers, task_queues());
237 ShenandoahConcurrentMarkingTask task(this, &terminator);
238 workers->run_task(&task);
239
240 if (heap->cancelled_gc()) {
241 // GC is cancelled, break out.
242 break;
243 }
244
245 size_t before = qset.completed_buffers_num();
246 Handshake::execute(&flush_satb);
247 size_t after = qset.completed_buffers_num();
248
249 if (before == after) {
250 // No more retries needed, break out.
251 break;
252 }
253 }
254 assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
255 }
256
257 void ShenandoahConcurrentMark::finish_mark() {
258 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
259 assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
260 finish_mark_work();
261 assert(task_queues()->is_empty(), "Should be empty");
262 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
263 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
264
265 ShenandoahHeap* const heap = ShenandoahHeap::heap();
266 heap->set_concurrent_mark_in_progress(false);
267 heap->mark_complete_marking_context();
268 }
269
270 void ShenandoahConcurrentMark::finish_mark_work() {
271 // Finally mark everything else we've got in our queues during the previous steps.
272 // It does two different things for concurrent vs. mark-compact GC:
273 // - For concurrent GC, it starts with empty task queues, drains the remaining
274 // SATB buffers, and then completes the marking closure.
275 // - For mark-compact GC, it starts out with the task queues seeded by initial
276 // root scan, and completes the closure, thus marking through all live objects
277 // The implementation is the same, so it's shared here.
278 ShenandoahHeap* const heap = ShenandoahHeap::heap();
279 ShenandoahGCPhase phase(ShenandoahPhaseTimings::finish_mark);
280 uint nworkers = heap->workers()->active_workers();
281 task_queues()->reserve(nworkers);
282
283 StrongRootsScope scope(nworkers);
284 TaskTerminator terminator(nworkers, task_queues());
285 ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
286 heap->workers()->run_task(&task);
287
288 assert(task_queues()->is_empty(), "Should be empty");
289 }
290
291
292 void ShenandoahConcurrentMark::cancel() {
293 clear();
294 ShenandoahReferenceProcessor* rp = ShenandoahHeap::heap()->ref_processor();
295 rp->abandon_partial_discovery();
296 }