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 ShenandoahConcurrentMarkingTask : public WorkerTask {
 46 private:
 47   ShenandoahConcurrentMark* const _cm;
 48   TaskTerminator* const           _terminator;
 49 
 50 public:
 51   ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
 52     WorkerTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
 53   }
 54 
 55   void work(uint worker_id) {
 56     ShenandoahHeap* heap = ShenandoahHeap::heap();
 57     ShenandoahConcurrentWorkerSession worker_session(worker_id);
 58     ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 59     ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
 60     ShenandoahReferenceProcessor* rp = heap->ref_processor();
 61     assert(rp != NULL, "need reference processor");
 62     StringDedup::Requests requests;
 63     _cm->mark_loop(worker_id, _terminator, rp,
 64                    true /*cancellable*/,
 65                    ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
 66                    &requests);
 67   }
 68 };
 69 
 70 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
 71 private:
 72   SATBMarkQueueSet& _satb_qset;
 73   OopClosure* const _cl;
 74   uintx _claim_token;
 75 
 76 public:
 77   ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
 78     _satb_qset(satb_qset),
 79     _cl(cl),
 80     _claim_token(Threads::thread_claim_token()) {}
 81 
 82   void do_thread(Thread* thread) {
 83     if (thread->claim_threads_do(true, _claim_token)) {
 84       // Transfer any partial buffer to the qset for completed buffer processing.
 85       _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
 86       if (thread->is_Java_thread()) {
 87         if (_cl != NULL) {
 88           ResourceMark rm;
 89           thread->oops_do(_cl, NULL);
 90         }
 91       }
 92     }
 93   }
 94 };
 95 
 96 class ShenandoahFinalMarkingTask : public WorkerTask {
 97 private:
 98   ShenandoahConcurrentMark* _cm;
 99   TaskTerminator*           _terminator;
100   bool                      _dedup_string;
101 
102 public:
103   ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
104     WorkerTask("Shenandoah Final Mark"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
105   }
106 
107   void work(uint worker_id) {
108     ShenandoahHeap* heap = ShenandoahHeap::heap();
109 
110     ShenandoahParallelWorkerSession worker_session(worker_id);
111     ShenandoahReferenceProcessor* rp = heap->ref_processor();
112     StringDedup::Requests requests;
113 
114     // First drain remaining SATB buffers.
115     {
116       ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
117 
118       ShenandoahSATBBufferClosure cl(q);
119       SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
120       while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
121       assert(!heap->has_forwarded_objects(), "Not expected");
122 
123       ShenandoahMarkRefsClosure             mark_cl(q, rp);
124       ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
125                                                ShenandoahIUBarrier ? &mark_cl : NULL);
126       Threads::threads_do(&tc);
127     }
128     _cm->mark_loop(worker_id, _terminator, rp,
129                    false /*not cancellable*/,
130                    _dedup_string ? ENQUEUE_DEDUP : NO_DEDUP,
131                    &requests);
132     assert(_cm->task_queues()->is_empty(), "Should be empty");
133   }
134 };
135 
136 ShenandoahConcurrentMark::ShenandoahConcurrentMark() :
137   ShenandoahMark() {}
138 
139 // Mark concurrent roots during concurrent phases
140 class ShenandoahMarkConcurrentRootsTask : public WorkerTask {
141 private:
142   SuspendibleThreadSetJoiner          _sts_joiner;
143   ShenandoahConcurrentRootScanner     _root_scanner;
144   ShenandoahObjToScanQueueSet* const  _queue_set;
145   ShenandoahReferenceProcessor* const _rp;
146 
147 public:
148   ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
149                                     ShenandoahReferenceProcessor* rp,
150                                     ShenandoahPhaseTimings::Phase phase,
151                                     uint nworkers);
152   void work(uint worker_id);
153 };
154 
155 ShenandoahMarkConcurrentRootsTask::ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
156                                                                      ShenandoahReferenceProcessor* rp,
157                                                                      ShenandoahPhaseTimings::Phase phase,
158                                                                      uint nworkers) :
159   WorkerTask("Shenandoah Concurrent Mark Roots"),
160   _root_scanner(nworkers, phase),
161   _queue_set(qs),
162   _rp(rp) {
163   assert(!ShenandoahHeap::heap()->has_forwarded_objects(), "Not expected");
164 }
165 
166 void ShenandoahMarkConcurrentRootsTask::work(uint worker_id) {
167   ShenandoahConcurrentWorkerSession worker_session(worker_id);
168   ShenandoahObjToScanQueue* q = _queue_set->queue(worker_id);
169   ShenandoahMarkRefsClosure cl(q, _rp);
170   _root_scanner.roots_do(&cl, worker_id);
171 }
172 
173 void ShenandoahConcurrentMark::mark_concurrent_roots() {
174   ShenandoahHeap* const heap = ShenandoahHeap::heap();
175   assert(!heap->has_forwarded_objects(), "Not expected");
176 
177   TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
178 
179   WorkerThreads* workers = heap->workers();
180   ShenandoahReferenceProcessor* rp = heap->ref_processor();
181   task_queues()->reserve(workers->active_workers());
182   ShenandoahMarkConcurrentRootsTask task(task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
183 
184   workers->run_task(&task);
185 }
186 
187 class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
188 private:
189   SATBMarkQueueSet& _qset;
190 public:
191   ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
192     HandshakeClosure("Shenandoah Flush SATB Handshake"),
193     _qset(qset) {}
194 
195   void do_thread(Thread* thread) {
196     _qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
197   }
198 };
199 
200 void ShenandoahConcurrentMark::concurrent_mark() {
201   ShenandoahHeap* const heap = ShenandoahHeap::heap();
202   WorkerThreads* workers = heap->workers();
203   uint nworkers = workers->active_workers();
204   task_queues()->reserve(nworkers);
205 
206   ShenandoahSATBMarkQueueSet& qset = ShenandoahBarrierSet::satb_mark_queue_set();
207   ShenandoahFlushSATBHandshakeClosure flush_satb(qset);
208   for (uint flushes = 0; flushes < ShenandoahMaxSATBBufferFlushes; flushes++) {
209     TaskTerminator terminator(nworkers, task_queues());
210     ShenandoahConcurrentMarkingTask task(this, &terminator);
211     workers->run_task(&task);
212 
213     if (heap->cancelled_gc()) {
214       // GC is cancelled, break out.
215       break;
216     }
217 
218     size_t before = qset.completed_buffers_num();
219     Handshake::execute(&flush_satb);
220     size_t after = qset.completed_buffers_num();
221 
222     if (before == after) {
223       // No more retries needed, break out.
224       break;
225     }
226   }
227   assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
228 }
229 
230 void ShenandoahConcurrentMark::finish_mark() {
231   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
232   assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
233   finish_mark_work();
234   assert(task_queues()->is_empty(), "Should be empty");
235   TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
236   TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
237 
238   ShenandoahHeap* const heap = ShenandoahHeap::heap();
239   heap->set_concurrent_mark_in_progress(false);
240   heap->mark_complete_marking_context();
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 }