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
47 class ShenandoahUpdateRootsTask : public AbstractGangTask {
48 private:
49 ShenandoahRootUpdater* _root_updater;
50 bool _check_alive;
51 public:
52 ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater, bool check_alive) :
53 AbstractGangTask("Shenandoah Update Roots"),
54 _root_updater(root_updater),
55 _check_alive(check_alive){
56 }
57
58 void work(uint worker_id) {
59 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
60 ShenandoahParallelWorkerSession worker_session(worker_id);
61
62 ShenandoahHeap* heap = ShenandoahHeap::heap();
63 ShenandoahUpdateRefsClosure cl;
64 if (_check_alive) {
65 ShenandoahForwardedIsAliveClosure is_alive;
66 _root_updater->roots_do<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>(worker_id, &is_alive, &cl);
67 } else {
68 AlwaysTrueClosure always_true;;
69 _root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
70 }
71 }
72 };
73
74 template <GenerationMode GENERATION>
75 class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
76 private:
77 ShenandoahConcurrentMark* const _cm;
78 TaskTerminator* const _terminator;
79
80 public:
81 ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
82 AbstractGangTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
83 }
84
85 void work(uint worker_id) {
86 ShenandoahHeap* heap = ShenandoahHeap::heap();
87 ShenandoahConcurrentWorkerSession worker_session(worker_id);
88 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
89 ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
90 assert(rp != NULL, "need reference processor");
91 StringDedup::Requests requests;
92 _cm->mark_loop(GENERATION, worker_id, _terminator, rp,
93 true /*cancellable*/,
94 ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
95 &requests);
96 }
97 };
98
99 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
100 private:
101 SATBMarkQueueSet& _satb_qset;
102 OopClosure* const _cl;
103 uintx _claim_token;
104
105 public:
106 ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
107 _satb_qset(satb_qset),
108 _cl(cl),
109 _claim_token(Threads::thread_claim_token()) {}
110
111 void do_thread(Thread* thread) {
112 if (thread->claim_threads_do(true, _claim_token)) {
113 // Transfer any partial buffer to the qset for completed buffer processing.
114 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
115 if (thread->is_Java_thread()) {
116 if (_cl != NULL) {
117 ResourceMark rm;
118 thread->oops_do(_cl, NULL);
119 }
120 }
121 }
122 }
123 };
124
125 template<GenerationMode GENERATION>
126 class ShenandoahFinalMarkingTask : public AbstractGangTask {
127 private:
128 ShenandoahConcurrentMark* _cm;
129 TaskTerminator* _terminator;
130 bool _dedup_string;
131
132 public:
133 ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
134 AbstractGangTask("Shenandoah Final Mark"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
135 }
136
137 void work(uint worker_id) {
138 ShenandoahHeap* heap = ShenandoahHeap::heap();
139
140 ShenandoahParallelWorkerSession worker_session(worker_id);
141 StringDedup::Requests requests;
142 ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
143
144 // First drain remaining SATB buffers.
145 {
146 ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
147 ShenandoahObjToScanQueue* old = _cm->get_old_queue(worker_id);
148
149 ShenandoahSATBBufferClosure<GENERATION> cl(q, old);
150 SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
151 while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
152 assert(!heap->has_forwarded_objects(), "Not expected");
153
154 ShenandoahMarkRefsClosure<GENERATION> mark_cl(q, rp, old);
155 ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
156 ShenandoahIUBarrier ? &mark_cl : NULL);
157 Threads::threads_do(&tc);
158 }
159 _cm->mark_loop(GENERATION, worker_id, _terminator, rp,
160 false /*not cancellable*/,
161 _dedup_string ? ENQUEUE_DEDUP : NO_DEDUP,
162 &requests);
163 assert(_cm->task_queues()->is_empty(), "Should be empty");
164 }
165 };
166
167 ShenandoahConcurrentMark::ShenandoahConcurrentMark(ShenandoahGeneration* generation) :
168 ShenandoahMark(generation) {}
169
170 // Mark concurrent roots during concurrent phases
171 template<GenerationMode GENERATION>
172 class ShenandoahMarkConcurrentRootsTask : public AbstractGangTask {
173 private:
174 SuspendibleThreadSetJoiner _sts_joiner;
175 ShenandoahConcurrentRootScanner _root_scanner;
176 ShenandoahObjToScanQueueSet* const _queue_set;
177 ShenandoahObjToScanQueueSet* const _old_queue_set;
178 ShenandoahReferenceProcessor* const _rp;
179
180 public:
181 ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
182 ShenandoahObjToScanQueueSet* old,
183 ShenandoahReferenceProcessor* rp,
184 ShenandoahPhaseTimings::Phase phase,
185 uint nworkers);
186 void work(uint worker_id);
187 };
188
189 template<GenerationMode GENERATION>
190 ShenandoahMarkConcurrentRootsTask<GENERATION>::ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
191 ShenandoahObjToScanQueueSet* old,
192 ShenandoahReferenceProcessor* rp,
193 ShenandoahPhaseTimings::Phase phase,
194 uint nworkers) :
195 AbstractGangTask("Shenandoah Concurrent Mark Roots"),
196 _root_scanner(nworkers, phase),
197 _queue_set(qs),
198 _old_queue_set(old),
199 _rp(rp) {
200 assert(!ShenandoahHeap::heap()->has_forwarded_objects(), "Not expected");
201 }
202
203 template<GenerationMode GENERATION>
204 void ShenandoahMarkConcurrentRootsTask<GENERATION>::work(uint worker_id) {
205 ShenandoahConcurrentWorkerSession worker_session(worker_id);
206 ShenandoahObjToScanQueue* q = _queue_set->queue(worker_id);
207 ShenandoahObjToScanQueue* old = _old_queue_set == NULL ? NULL : _old_queue_set->queue(worker_id);
208 ShenandoahMarkRefsClosure<GENERATION> cl(q, _rp, old);
209 _root_scanner.roots_do(&cl, worker_id);
210 }
211
212 void ShenandoahConcurrentMark::mark_concurrent_roots() {
213 ShenandoahHeap* const heap = ShenandoahHeap::heap();
214 assert(!heap->has_forwarded_objects(), "Not expected");
215
216 WorkGang* workers = heap->workers();
217 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
218 _generation->reserve_task_queues(workers->active_workers());
219 switch (_generation->generation_mode()) {
220 case YOUNG: {
221 ShenandoahMarkConcurrentRootsTask<YOUNG> task(task_queues(), old_task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
222 workers->run_task(&task);
223 break;
224 }
225 case GLOBAL: {
226 assert(old_task_queues() == NULL, "Global mark should not have old gen mark queues.");
227 ShenandoahMarkConcurrentRootsTask<GLOBAL> task(task_queues(), old_task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
228 workers->run_task(&task);
229 break;
230 }
231 default:
232 // Intentionally haven't added OLD here. We use a YOUNG generation
233 // cycle to bootstrap concurrent old marking.
234 ShouldNotReachHere();
235 }
236 }
237
238 class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
239 private:
240 SATBMarkQueueSet& _qset;
241 public:
242 ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
243 HandshakeClosure("Shenandoah Flush SATB Handshake"),
244 _qset(qset) {}
245
246 void do_thread(Thread* thread) {
247 _qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
248 }
249 };
250
251 void ShenandoahConcurrentMark::concurrent_mark() {
252 ShenandoahHeap* const heap = ShenandoahHeap::heap();
253 WorkGang* workers = heap->workers();
254 uint nworkers = workers->active_workers();
255 task_queues()->reserve(nworkers);
256
257 ShenandoahSATBMarkQueueSet& qset = ShenandoahBarrierSet::satb_mark_queue_set();
258 ShenandoahFlushSATBHandshakeClosure flush_satb(qset);
259 for (uint flushes = 0; flushes < ShenandoahMaxSATBBufferFlushes; flushes++) {
260 switch (_generation->generation_mode()) {
261 case YOUNG: {
262 TaskTerminator terminator(nworkers, task_queues());
263 ShenandoahConcurrentMarkingTask<YOUNG> task(this, &terminator);
264 workers->run_task(&task);
265 break;
266 }
267 case OLD: {
268 TaskTerminator terminator(nworkers, task_queues());
269 ShenandoahConcurrentMarkingTask<OLD> task(this, &terminator);
270 workers->run_task(&task);
271 break;
272 }
273 case GLOBAL: {
274 TaskTerminator terminator(nworkers, task_queues());
275 ShenandoahConcurrentMarkingTask<GLOBAL> task(this, &terminator);
276 workers->run_task(&task);
277 break;
278 }
279 default:
280 ShouldNotReachHere();
281 }
282
283 if (heap->cancelled_gc()) {
284 // GC is cancelled, break out.
285 break;
286 }
287
288 size_t before = qset.completed_buffers_num();
289 Handshake::execute(&flush_satb);
290 size_t after = qset.completed_buffers_num();
291
292 if (before == after) {
293 // No more retries needed, break out.
294 break;
295 }
296 }
297 assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
298 }
299
300 void ShenandoahConcurrentMark::finish_mark() {
301 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
302 assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
303 finish_mark_work();
304 assert(task_queues()->is_empty(), "Should be empty");
305 TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
306 TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
307
308 _generation->set_concurrent_mark_in_progress(false);
309 _generation->set_mark_complete();
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->generation_mode()) {
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 default:
345 ShouldNotReachHere();
346 }
347
348
349 assert(task_queues()->is_empty(), "Should be empty");
350 }