1 /*
2 * Copyright (c) 2013, 2021, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27
28 #include "gc/shared/satbMarkQueue.hpp"
29 #include "gc/shared/strongRootsScope.hpp"
30 #include "gc/shared/taskTerminator.hpp"
31 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
32 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
33 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
34 #include "gc/shenandoah/shenandoahGeneration.hpp"
35 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
36 #include "gc/shenandoah/shenandoahMark.inline.hpp"
37 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
38 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
39 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
40 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
41 #include "gc/shenandoah/shenandoahStringDedup.hpp"
42 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
43 #include "gc/shenandoah/shenandoahUtils.hpp"
44 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
45 #include "memory/iterator.inline.hpp"
46 #include "memory/resourceArea.hpp"
47 #include "runtime/continuation.hpp"
48 #include "runtime/threads.hpp"
49
50 template <ShenandoahGenerationType GENERATION>
51 class ShenandoahConcurrentMarkingTask : public WorkerTask {
52 private:
53 ShenandoahConcurrentMark* const _cm;
54 TaskTerminator* const _terminator;
55
56 public:
57 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
58 WorkerTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
59 }
60
61 void work(uint worker_id) {
62 ShenandoahHeap* heap = ShenandoahHeap::heap();
63 ShenandoahConcurrentWorkerSession worker_session(worker_id);
64 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_mark, ShenandoahPhaseTimings::ParallelMark, worker_id, true);
65 ShenandoahSuspendibleThreadSetJoiner stsj;
66 // Do not use active_generation() : we must use the gc_generation() set by
67 // ShenandoahGCScope on the ControllerThread's stack; no safepoint may
68 // intervene to update active_generation, so we can't
69 // shenandoah_assert_generations_reconciled() here.
70 ShenandoahReferenceProcessor* rp = heap->gc_generation()->ref_processor();
71 assert(rp != nullptr, "need reference processor");
72 StringDedup::Requests requests;
73 _cm->mark_loop(worker_id, _terminator, rp, GENERATION, true /*cancellable*/,
74 ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
75 &requests);
76 }
77 };
78
79 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
80 private:
81 SATBMarkQueueSet& _satb_qset;
82 OopClosure* const _cl;
83
84 public:
85 ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
86 _satb_qset(satb_qset),
87 _cl(cl) {}
88
89 void do_thread(Thread* thread) {
90 // Transfer any partial buffer to the qset for completed buffer processing.
91 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
92 if (thread->is_Java_thread()) {
93 if (_cl != nullptr) {
94 ResourceMark rm;
95 thread->oops_do(_cl, nullptr);
96 }
97 }
98 }
99 };
100
101 template <ShenandoahGenerationType 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->gc_generation()->ref_processor();
119 shenandoah_assert_generations_reconciled();
120
121 // First drain remaining SATB buffers.
122 {
123 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
124 ShenandoahObjToScanQueue* old_q = _cm->get_old_queue(worker_id);
125
126 ShenandoahSATBBufferClosure<GENERATION> cl(q, old_q);
127 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
128 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
129 assert(!heap->has_forwarded_objects(), "Not expected");
130
131 ShenandoahMarkRefsClosure<GENERATION> mark_cl(q, rp, old_q);
132 ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
133 ShenandoahIUBarrier ? &mark_cl : nullptr);
134 Threads::possibly_parallel_threads_do(true /* is_par */, &tc);
135 }
136 _cm->mark_loop(worker_id, _terminator, rp, GENERATION, 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 <ShenandoahGenerationType 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 <ShenandoahGenerationType 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 <ShenandoahGenerationType 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_q = (_old_queue_set == nullptr) ?
184 nullptr : _old_queue_set->queue(worker_id);
185 ShenandoahMarkRefsClosure<GENERATION> cl(q, _rp, old_q);
186 _root_scanner.roots_do(&cl, worker_id);
187 }
188
189 void ShenandoahConcurrentMark::mark_concurrent_roots() {
190 ShenandoahHeap* const heap = ShenandoahHeap::heap();
191 assert(!heap->has_forwarded_objects(), "Not expected");
192
193 WorkerThreads* workers = heap->workers();
194 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
195 _generation->reserve_task_queues(workers->active_workers());
196 switch (_generation->type()) {
197 case YOUNG: {
198 ShenandoahMarkConcurrentRootsTask<YOUNG> task(task_queues(), old_task_queues(), rp,
199 ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
200 workers->run_task(&task);
201 break;
202 }
203 case GLOBAL: {
204 assert(old_task_queues() == nullptr, "Global mark should not have old gen mark queues");
205 ShenandoahMarkConcurrentRootsTask<GLOBAL> task(task_queues(), nullptr, rp,
206 ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
207 workers->run_task(&task);
208 break;
209 }
210 case NON_GEN: {
211 assert(old_task_queues() == nullptr, "Non-generational mark should not have old gen mark queues");
212 ShenandoahMarkConcurrentRootsTask<NON_GEN> task(task_queues(), nullptr, rp,
213 ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
214 workers->run_task(&task);
215 break;
216 }
217 case OLD: {
218 // We use a YOUNG generation cycle to bootstrap concurrent old marking.
219 ShouldNotReachHere();
220 break;
221 }
222 default:
223 ShouldNotReachHere();
224 }
225 }
226
227 class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
228 private:
229 SATBMarkQueueSet& _qset;
230 public:
231 ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
232 HandshakeClosure("Shenandoah Flush SATB Handshake"),
233 _qset(qset) {}
234
235 void do_thread(Thread* thread) {
236 _qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
237 }
238 };
239
240 void ShenandoahConcurrentMark::concurrent_mark() {
241 ShenandoahHeap* const heap = ShenandoahHeap::heap();
242 WorkerThreads* workers = heap->workers();
243 uint nworkers = workers->active_workers();
244 task_queues()->reserve(nworkers);
245
246 ShenandoahGenerationType gen_type = _generation->type();
247 ShenandoahSATBMarkQueueSet& qset = ShenandoahBarrierSet::satb_mark_queue_set();
248 ShenandoahFlushSATBHandshakeClosure flush_satb(qset);
249 for (uint flushes = 0; flushes < ShenandoahMaxSATBBufferFlushes; flushes++) {
250 switch (gen_type) {
251 case YOUNG: {
252 TaskTerminator terminator(nworkers, task_queues());
253 ShenandoahConcurrentMarkingTask<YOUNG> task(this, &terminator);
254 workers->run_task(&task);
255 break;
256 }
257 case OLD: {
258 TaskTerminator terminator(nworkers, task_queues());
259 ShenandoahConcurrentMarkingTask<OLD> task(this, &terminator);
260 workers->run_task(&task);
261 break;
262 }
263 case GLOBAL: {
264 TaskTerminator terminator(nworkers, task_queues());
265 ShenandoahConcurrentMarkingTask<GLOBAL> task(this, &terminator);
266 workers->run_task(&task);
267 break;
268 }
269 case NON_GEN: {
270 TaskTerminator terminator(nworkers, task_queues());
271 ShenandoahConcurrentMarkingTask<NON_GEN> task(this, &terminator);
272 workers->run_task(&task);
273 break;
274 }
275 default:
276 ShouldNotReachHere();
277 }
278
279 if (heap->cancelled_gc()) {
280 // GC is cancelled, break out.
281 break;
282 }
283
284 size_t before = qset.completed_buffers_num();
285 {
286 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_mark_satb_flush, true);
287 Handshake::execute(&flush_satb);
288 }
289 size_t after = qset.completed_buffers_num();
290
291 if (before == after) {
292 // No more retries needed, break out.
293 break;
294 }
295 }
296 assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
297 }
298
299 void ShenandoahConcurrentMark::finish_mark() {
300 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
301 assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
302 finish_mark_work();
303 assert(task_queues()->is_empty(), "Should be empty");
304 TASKQUEUE_STATS_ONLY(task_queues()->print_and_reset_taskqueue_stats(""));
305
306 _generation->set_concurrent_mark_in_progress(false);
307 _generation->set_mark_complete();
308
309 end_mark();
310 }
311
312 void ShenandoahConcurrentMark::finish_mark_work() {
313 // Finally mark everything else we've got in our queues during the previous steps.
314 // It does two different things for concurrent vs. mark-compact GC:
315 // - For concurrent GC, it starts with empty task queues, drains the remaining
316 // SATB buffers, and then completes the marking closure.
317 // - For mark-compact GC, it starts out with the task queues seeded by initial
318 // root scan, and completes the closure, thus marking through all live objects
319 // The implementation is the same, so it's shared here.
320 ShenandoahHeap* const heap = ShenandoahHeap::heap();
321 ShenandoahGCPhase phase(ShenandoahPhaseTimings::finish_mark);
322 uint nworkers = heap->workers()->active_workers();
323 task_queues()->reserve(nworkers);
324
325 StrongRootsScope scope(nworkers);
326 TaskTerminator terminator(nworkers, task_queues());
327
328 switch (_generation->type()) {
329 case YOUNG:{
330 ShenandoahFinalMarkingTask<YOUNG> task(this, &terminator, ShenandoahStringDedup::is_enabled());
331 heap->workers()->run_task(&task);
332 break;
333 }
334 case OLD:{
335 ShenandoahFinalMarkingTask<OLD> task(this, &terminator, ShenandoahStringDedup::is_enabled());
336 heap->workers()->run_task(&task);
337 break;
338 }
339 case GLOBAL:{
340 ShenandoahFinalMarkingTask<GLOBAL> task(this, &terminator, ShenandoahStringDedup::is_enabled());
341 heap->workers()->run_task(&task);
342 break;
343 }
344 case NON_GEN:{
345 ShenandoahFinalMarkingTask<NON_GEN> task(this, &terminator, ShenandoahStringDedup::is_enabled());
346 heap->workers()->run_task(&task);
347 break;
348 }
349 default:
350 ShouldNotReachHere();
351 }
352
353
354 assert(task_queues()->is_empty(), "Should be empty");
355 }