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 template <GenerationMode GENERATION>
 48 class ShenandoahConcurrentMarkingTask : public WorkerTask {
 49 private:
 50   ShenandoahConcurrentMark* const _cm;
 51   TaskTerminator* const           _terminator;
 52 
 53 public:
 54   ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator) :
 55     WorkerTask("Shenandoah Concurrent Mark"), _cm(cm), _terminator(terminator) {
 56   }
 57 
 58   void work(uint worker_id) {
 59     ShenandoahHeap* heap = ShenandoahHeap::heap();
 60     ShenandoahParallelWorkerSession worker_session(worker_id);
 61     ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_mark, ShenandoahPhaseTimings::ParallelMark, worker_id, true);
 62     ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
 63     ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
 64     assert(rp != NULL, "need reference processor");
 65     StringDedup::Requests requests;
 66     _cm->mark_loop(GENERATION, worker_id, _terminator, rp,
 67                    true /*cancellable*/,
 68                    ShenandoahStringDedup::is_enabled() ? ENQUEUE_DEDUP : NO_DEDUP,
 69                    &requests);
 70   }
 71 };
 72 
 73 class ShenandoahSATBAndRemarkThreadsClosure : public ThreadClosure {
 74 private:
 75   SATBMarkQueueSet& _satb_qset;
 76   OopClosure* const _cl;
 77   uintx _claim_token;
 78 
 79 public:
 80   ShenandoahSATBAndRemarkThreadsClosure(SATBMarkQueueSet& satb_qset, OopClosure* cl) :
 81     _satb_qset(satb_qset),
 82     _cl(cl),
 83     _claim_token(Threads::thread_claim_token()) {}
 84 
 85   void do_thread(Thread* thread) {
 86     if (thread->claim_threads_do(true, _claim_token)) {
 87       // Transfer any partial buffer to the qset for completed buffer processing.
 88       _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
 89       if (thread->is_Java_thread()) {
 90         if (_cl != NULL) {
 91           ResourceMark rm;
 92           thread->oops_do(_cl, NULL);
 93         }
 94       }
 95     }
 96   }
 97 };
 98 
 99 template<GenerationMode GENERATION>
100 class ShenandoahFinalMarkingTask : public WorkerTask {
101 private:
102   ShenandoahConcurrentMark* _cm;
103   TaskTerminator*           _terminator;
104   bool                      _dedup_string;
105 
106 public:
107   ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, TaskTerminator* terminator, bool dedup_string) :
108     WorkerTask("Shenandoah Final Mark"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
109   }
110 
111   void work(uint worker_id) {
112     ShenandoahHeap* heap = ShenandoahHeap::heap();
113 
114     ShenandoahParallelWorkerSession worker_session(worker_id);
115     StringDedup::Requests requests;
116     ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
117 
118     // First drain remaining SATB buffers.
119     {
120       ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
121       ShenandoahObjToScanQueue* old = _cm->get_old_queue(worker_id);
122 
123       ShenandoahSATBBufferClosure<GENERATION> cl(q, old);
124       SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
125       while (satb_mq_set.apply_closure_to_completed_buffer(&cl)) {}
126       assert(!heap->has_forwarded_objects(), "Not expected");
127 
128       ShenandoahMarkRefsClosure<GENERATION> mark_cl(q, rp, old);
129       ShenandoahSATBAndRemarkThreadsClosure tc(satb_mq_set,
130                                                ShenandoahIUBarrier ? &mark_cl : NULL);
131       Threads::threads_do(&tc);
132     }
133     _cm->mark_loop(GENERATION, worker_id, _terminator, rp,
134                    false /*not cancellable*/,
135                    _dedup_string ? ENQUEUE_DEDUP : NO_DEDUP,
136                    &requests);
137     assert(_cm->task_queues()->is_empty(), "Should be empty");
138   }
139 };
140 
141 ShenandoahConcurrentMark::ShenandoahConcurrentMark(ShenandoahGeneration* generation) :
142   ShenandoahMark(generation) {}
143 
144 // Mark concurrent roots during concurrent phases
145 template<GenerationMode GENERATION>
146 class ShenandoahMarkConcurrentRootsTask : public WorkerTask {
147 private:
148   SuspendibleThreadSetJoiner          _sts_joiner;
149   ShenandoahConcurrentRootScanner     _root_scanner;
150   ShenandoahObjToScanQueueSet* const  _queue_set;
151   ShenandoahObjToScanQueueSet* const  _old_queue_set;
152   ShenandoahReferenceProcessor* const _rp;
153 
154 public:
155   ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
156                                     ShenandoahObjToScanQueueSet* old,
157                                     ShenandoahReferenceProcessor* rp,
158                                     ShenandoahPhaseTimings::Phase phase,
159                                     uint nworkers);
160   void work(uint worker_id);
161 };
162 
163 template<GenerationMode GENERATION>
164 ShenandoahMarkConcurrentRootsTask<GENERATION>::ShenandoahMarkConcurrentRootsTask(ShenandoahObjToScanQueueSet* qs,
165                                                                                  ShenandoahObjToScanQueueSet* old,
166                                                                                  ShenandoahReferenceProcessor* rp,
167                                                                                  ShenandoahPhaseTimings::Phase phase,
168                                                                                  uint nworkers) :
169   WorkerTask("Shenandoah Concurrent Mark Roots"),
170   _root_scanner(nworkers, phase),
171   _queue_set(qs),
172   _old_queue_set(old),
173   _rp(rp) {
174   assert(!ShenandoahHeap::heap()->has_forwarded_objects(), "Not expected");
175 }
176 
177 template<GenerationMode GENERATION>
178 void ShenandoahMarkConcurrentRootsTask<GENERATION>::work(uint worker_id) {
179   ShenandoahConcurrentWorkerSession worker_session(worker_id);
180   ShenandoahObjToScanQueue* q = _queue_set->queue(worker_id);
181   ShenandoahObjToScanQueue* old = _old_queue_set == NULL ? NULL : _old_queue_set->queue(worker_id);
182   ShenandoahMarkRefsClosure<GENERATION> cl(q, _rp, old);
183   _root_scanner.roots_do(&cl, worker_id);
184 }
185 
186 void ShenandoahConcurrentMark::mark_concurrent_roots() {
187   ShenandoahHeap* const heap = ShenandoahHeap::heap();
188   assert(!heap->has_forwarded_objects(), "Not expected");
189 
190   WorkerThreads* workers = heap->workers();
191   ShenandoahReferenceProcessor* rp = _generation->ref_processor();
192   _generation->reserve_task_queues(workers->active_workers());
193   switch (_generation->generation_mode()) {
194     case YOUNG: {
195       ShenandoahMarkConcurrentRootsTask<YOUNG> task(task_queues(), old_task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
196       workers->run_task(&task);
197       break;
198     }
199     case GLOBAL: {
200       assert(old_task_queues() == NULL, "Global mark should not have old gen mark queues.");
201       ShenandoahMarkConcurrentRootsTask<GLOBAL> task(task_queues(), old_task_queues(), rp, ShenandoahPhaseTimings::conc_mark_roots, workers->active_workers());
202       workers->run_task(&task);
203       break;
204     }
205     default:
206       // Intentionally haven't added OLD here. We use a YOUNG generation
207       // cycle to bootstrap concurrent old marking.
208       ShouldNotReachHere();
209   }
210 }
211 
212 class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
213 private:
214   SATBMarkQueueSet& _qset;
215 public:
216   ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
217     HandshakeClosure("Shenandoah Flush SATB Handshake"),
218     _qset(qset) {}
219 
220   void do_thread(Thread* thread) {
221     _qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
222   }
223 };
224 
225 void ShenandoahConcurrentMark::concurrent_mark() {
226   ShenandoahHeap* const heap = ShenandoahHeap::heap();
227   WorkerThreads* workers = heap->workers();
228   uint nworkers = workers->active_workers();
229   task_queues()->reserve(nworkers);
230 
231   ShenandoahSATBMarkQueueSet& qset = ShenandoahBarrierSet::satb_mark_queue_set();
232   ShenandoahFlushSATBHandshakeClosure flush_satb(qset);
233   for (uint flushes = 0; flushes < ShenandoahMaxSATBBufferFlushes; flushes++) {
234     switch (_generation->generation_mode()) {
235       case YOUNG: {
236         TaskTerminator terminator(nworkers, task_queues());
237         ShenandoahConcurrentMarkingTask<YOUNG> task(this, &terminator);
238         workers->run_task(&task);
239         break;
240       }
241       case OLD: {
242         TaskTerminator terminator(nworkers, task_queues());
243         ShenandoahConcurrentMarkingTask<OLD> task(this, &terminator);
244         workers->run_task(&task);
245         break;
246       }
247       case GLOBAL: {
248         TaskTerminator terminator(nworkers, task_queues());
249         ShenandoahConcurrentMarkingTask<GLOBAL> task(this, &terminator);
250         workers->run_task(&task);
251         break;
252       }
253       default:
254         ShouldNotReachHere();
255     }
256 
257     if (heap->cancelled_gc()) {
258       // GC is cancelled, break out.
259       break;
260     }
261 
262     size_t before = qset.completed_buffers_num();
263     Handshake::execute(&flush_satb);
264     size_t after = qset.completed_buffers_num();
265 
266     if (before == after) {
267       // No more retries needed, break out.
268       break;
269     }
270   }
271   assert(task_queues()->is_empty() || heap->cancelled_gc(), "Should be empty when not cancelled");
272 }
273 
274 void ShenandoahConcurrentMark::finish_mark() {
275   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
276   assert(Thread::current()->is_VM_thread(), "Must by VM Thread");
277   finish_mark_work();
278   assert(task_queues()->is_empty(), "Should be empty");
279   TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
280   TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
281 
282   _generation->set_concurrent_mark_in_progress(false);
283   _generation->set_mark_complete();
284 }
285 
286 void ShenandoahConcurrentMark::finish_mark_work() {
287   // Finally mark everything else we've got in our queues during the previous steps.
288   // It does two different things for concurrent vs. mark-compact GC:
289   // - For concurrent GC, it starts with empty task queues, drains the remaining
290   //   SATB buffers, and then completes the marking closure.
291   // - For mark-compact GC, it starts out with the task queues seeded by initial
292   //   root scan, and completes the closure, thus marking through all live objects
293   // The implementation is the same, so it's shared here.
294   ShenandoahHeap* const heap = ShenandoahHeap::heap();
295   ShenandoahGCPhase phase(ShenandoahPhaseTimings::finish_mark);
296   uint nworkers = heap->workers()->active_workers();
297   task_queues()->reserve(nworkers);
298 
299   StrongRootsScope scope(nworkers);
300   TaskTerminator terminator(nworkers, task_queues());
301 
302   switch (_generation->generation_mode()) {
303     case YOUNG:{
304       ShenandoahFinalMarkingTask<YOUNG> task(this, &terminator, ShenandoahStringDedup::is_enabled());
305       heap->workers()->run_task(&task);
306       break;
307     }
308     case OLD:{
309       ShenandoahFinalMarkingTask<OLD> task(this, &terminator, ShenandoahStringDedup::is_enabled());
310       heap->workers()->run_task(&task);
311       break;
312     }
313     case GLOBAL:{
314       ShenandoahFinalMarkingTask<GLOBAL> task(this, &terminator, ShenandoahStringDedup::is_enabled());
315       heap->workers()->run_task(&task);
316       break;
317     }
318     default:
319       ShouldNotReachHere();
320   }
321 
322 
323   assert(task_queues()->is_empty(), "Should be empty");
324 }