1 /*
  2  * Copyright (c) 2021, 2022, 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 
 26 #include "precompiled.hpp"
 27 
 28 #include "gc/shared/strongRootsScope.hpp"
 29 #include "gc/shared/taskTerminator.hpp"
 30 #include "gc/shared/workerThread.hpp"
 31 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
 32 #include "gc/shenandoah/shenandoahGeneration.hpp"
 33 #include "gc/shenandoah/shenandoahMark.inline.hpp"
 34 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
 35 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
 36 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
 37 #include "gc/shenandoah/shenandoahSTWMark.hpp"
 38 #include "gc/shenandoah/shenandoahVerifier.hpp"
 39 
 40 template<GenerationMode GENERATION>
 41 class ShenandoahInitMarkRootsClosure : public OopClosure {
 42  private:
 43   ShenandoahObjToScanQueue* const _queue;
 44   ShenandoahMarkingContext* const _mark_context;
 45 
 46   template <class T>
 47     inline void do_oop_work(T* p);
 48 
 49  public:
 50   ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q);
 51 
 52   void do_oop(narrowOop* p) { do_oop_work(p); }
 53   void do_oop(oop* p)       { do_oop_work(p); }
 54 };
 55 
 56 template<GenerationMode GENERATION>
 57 ShenandoahInitMarkRootsClosure<GENERATION>::ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) :
 58 _queue(q),
 59 _mark_context(ShenandoahHeap::heap()->marking_context()) {
 60 }
 61 
 62 template <GenerationMode GENERATION>
 63 template <class T>
 64 void ShenandoahInitMarkRootsClosure<GENERATION>::do_oop_work(T* p) {
 65   // Only called from STW mark, should not be used to bootstrap old generation marking.
 66   ShenandoahMark::mark_through_ref<T, GENERATION>(p, _queue, nullptr, _mark_context, false);
 67 }
 68 
 69 class ShenandoahSTWMarkTask : public WorkerTask {
 70 private:
 71   ShenandoahSTWMark* const _mark;
 72 
 73 public:
 74   ShenandoahSTWMarkTask(ShenandoahSTWMark* mark);
 75   void work(uint worker_id);
 76 };
 77 
 78 ShenandoahSTWMarkTask::ShenandoahSTWMarkTask(ShenandoahSTWMark* mark) :
 79   WorkerTask("Shenandoah STW mark"),
 80   _mark(mark) {
 81 }
 82 
 83 void ShenandoahSTWMarkTask::work(uint worker_id) {
 84   ShenandoahParallelWorkerSession worker_session(worker_id);
 85   _mark->mark_roots(worker_id);
 86   _mark->finish_mark(worker_id);
 87 }
 88 
 89 ShenandoahSTWMark::ShenandoahSTWMark(ShenandoahGeneration* generation, bool full_gc) :
 90   ShenandoahMark(generation),
 91   _root_scanner(full_gc ? ShenandoahPhaseTimings::full_gc_mark : ShenandoahPhaseTimings::degen_gc_stw_mark),
 92   _terminator(ShenandoahHeap::heap()->workers()->active_workers(), task_queues()),
 93   _full_gc(full_gc) {
 94   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a Shenandoah safepoint");
 95 }
 96 
 97 void ShenandoahSTWMark::mark() {
 98   // Weak reference processing
 99   ShenandoahHeap* const heap = ShenandoahHeap::heap();
100   ShenandoahReferenceProcessor* rp = heap->active_generation()->ref_processor();
101   rp->reset_thread_locals();
102   rp->set_soft_reference_policy(heap->soft_ref_policy()->should_clear_all_soft_refs());
103 
104   // Init mark, do not expect forwarded pointers in roots
105   if (ShenandoahVerify) {
106     assert(Thread::current()->is_VM_thread(), "Must be");
107     heap->verifier()->verify_roots_no_forwarded();
108   }
109 
110   start_mark();
111 
112   uint nworkers = heap->workers()->active_workers();
113   task_queues()->reserve(nworkers);
114 
115   TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
116 
117   {
118     // Mark
119     if (_generation->generation_mode() == YOUNG) {
120       // But only scan the remembered set for young generation.
121       _generation->scan_remembered_set(false /* is_concurrent */);
122     }
123 
124     StrongRootsScope scope(nworkers);
125     ShenandoahSTWMarkTask task(this);
126     heap->workers()->run_task(&task);
127 
128     assert(task_queues()->is_empty(), "Should be empty");
129   }
130 
131   _generation->set_mark_complete();
132   end_mark();
133 
134   assert(task_queues()->is_empty(), "Should be empty");
135   TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
136   TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
137 }
138 
139 void ShenandoahSTWMark::mark_roots(uint worker_id) {
140   switch (_generation->generation_mode()) {
141     case GLOBAL: {
142       ShenandoahInitMarkRootsClosure<GLOBAL> init_mark(task_queues()->queue(worker_id));
143       _root_scanner.roots_do(&init_mark, worker_id);
144       break;
145     }
146     case YOUNG: {
147       ShenandoahInitMarkRootsClosure<YOUNG> init_mark(task_queues()->queue(worker_id));
148       _root_scanner.roots_do(&init_mark, worker_id);
149       break;
150     }
151     default:
152       ShouldNotReachHere();
153   }
154 }
155 
156 void ShenandoahSTWMark::finish_mark(uint worker_id) {
157   ShenandoahPhaseTimings::Phase phase = _full_gc ? ShenandoahPhaseTimings::full_gc_mark : ShenandoahPhaseTimings::degen_gc_stw_mark;
158   ShenandoahWorkerTimingsTracker timer(phase, ShenandoahPhaseTimings::ParallelMark, worker_id);
159   ShenandoahReferenceProcessor* rp = ShenandoahHeap::heap()->active_generation()->ref_processor();
160   StringDedup::Requests requests;
161 
162   mark_loop(_generation->generation_mode(),
163             worker_id, &_terminator, rp,
164             false /* not cancellable */,
165             ShenandoahStringDedup::is_enabled() ? ALWAYS_DEDUP : NO_DEDUP, &requests);
166 }
167