1 /*
2 * Copyright Amazon.com Inc. or its affiliates. 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/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
28 #include "gc/shenandoah/shenandoahFreeSet.hpp"
29 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
31 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
32 #include "gc/shenandoah/shenandoahOldGC.hpp"
33 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
34 #include "gc/shenandoah/shenandoahGeneration.hpp"
35 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
36 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
37 #include "prims/jvmtiTagMap.hpp"
38 #include "utilities/events.hpp"
39
40
41 ShenandoahOldGC::ShenandoahOldGC(ShenandoahOldGeneration* generation, ShenandoahSharedFlag& allow_preemption) :
42 ShenandoahConcurrentGC(generation, false), _old_generation(generation), _allow_preemption(allow_preemption) {
43 }
44
45 // Final mark for old-gen is different than for young or old, so we
46 // override the implementation.
47 void ShenandoahOldGC::op_final_mark() {
48
49 ShenandoahGenerationalHeap* const heap = ShenandoahGenerationalHeap::heap();
50 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
51 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
52
53 if (ShenandoahVerify) {
54 heap->verifier()->verify_roots_no_forwarded();
55 }
56
57 if (!heap->cancelled_gc()) {
58 assert(_mark.generation()->is_old(), "Generation of Old-Gen GC should be OLD");
59 _mark.finish_mark();
60 assert(!heap->cancelled_gc(), "STW mark cannot OOM");
61
62 // Old collection is complete, the young generation no longer needs this
63 // reference to the old concurrent mark so clean it up.
64 heap->young_generation()->set_old_gen_task_queues(nullptr);
65
66 // We need to do this because weak root cleaning reports the number of dead handles
67 JvmtiTagMap::set_needs_cleaning();
68
69 _generation->prepare_regions_and_collection_set(true);
70
71 heap->set_unload_classes(false);
72 heap->prepare_concurrent_roots();
73
74 // Believe verification following old-gen concurrent mark needs to be different than verification following
75 // young-gen concurrent mark, so am commenting this out for now:
76 // if (ShenandoahVerify) {
77 // heap->verifier()->verify_after_concmark();
78 // }
79
80 if (VerifyAfterGC) {
81 Universe::verify();
82 }
83 }
84 }
85
86 bool ShenandoahOldGC::collect(GCCause::Cause cause) {
87 auto heap = ShenandoahGenerationalHeap::heap();
88 assert(!_old_generation->is_doing_mixed_evacuations(), "Should not start an old gc with pending mixed evacuations");
89 assert(!_old_generation->is_preparing_for_mark(), "Old regions need to be parsable during concurrent mark.");
90
91 // Enable preemption of old generation mark.
92 _allow_preemption.set();
93
94 // Continue concurrent mark, do not reset regions, do not mark roots, do not collect $200.
95 entry_mark();
96
97 // If we failed to unset the preemption flag, it means another thread has already unset it.
98 if (!_allow_preemption.try_unset()) {
99 // The regulator thread has unset the preemption guard. That thread will shortly cancel
100 // the gc, but the control thread is now racing it. Wait until this thread sees the
101 // cancellation.
102 while (!heap->cancelled_gc()) {
103 SpinPause();
104 }
105 }
106
107 if (heap->cancelled_gc()) {
108 return false;
109 }
110
111 // Complete marking under STW
112 vmop_entry_final_mark();
113
114 if (_generation->is_concurrent_mark_in_progress()) {
115 assert(heap->cancelled_gc(), "Safepoint operation observed gc cancellation");
116 // GC may have been cancelled before final mark, but after the preceding cancellation check.
117 return false;
118 }
119
120 // We aren't dealing with old generation evacuation yet. Our heuristic
121 // should not have built a cset in final mark.
122 assert(!heap->is_evacuation_in_progress(), "Old gen evacuations are not supported");
123
124 // Process weak roots that might still point to regions that would be broken by cleanup
125 if (heap->is_concurrent_weak_root_in_progress()) {
126 entry_weak_refs();
127 entry_weak_roots();
128 }
129
130 // Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
131 // the space. This would be the last action if there is nothing to evacuate.
132 entry_cleanup_early();
133
134 heap->free_set()->log_status_under_lock();
135
136 assert(!heap->is_concurrent_strong_root_in_progress(), "No evacuations during old gc.");
137
138 // We must execute this vm operation if we completed final mark. We cannot
139 // return from here with weak roots in progress. This is not a valid gc state
140 // for any young collections (or allocation failures) that interrupt the old
141 // collection.
142 vmop_entry_final_roots();
143
144 // We do not rebuild_free following increments of old marking because memory has not been reclaimed. However, we may
145 // need to transfer memory to OLD in order to efficiently support the mixed evacuations that might immediately follow.
146 size_t allocation_runway = heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(0);
147 heap->compute_old_generation_balance(allocation_runway, 0);
148
149 ShenandoahGenerationalHeap::TransferResult result;
150 {
151 ShenandoahHeapLocker locker(heap->lock());
152 result = heap->balance_generations();
153 }
154
155 LogTarget(Info, gc, ergo) lt;
156 if (lt.is_enabled()) {
157 LogStream ls(lt);
158 result.print_on("Old Mark", &ls);
159 }
160 return true;
161 }