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/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
31 #include "gc/shenandoah/shenandoahOldGC.hpp"
32 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
33 #include "gc/shenandoah/shenandoahGeneration.hpp"
34 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
35 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
36 #include "prims/jvmtiTagMap.hpp"
37 #include "utilities/events.hpp"
38
39
40
41
42 ShenandoahOldGC::ShenandoahOldGC(ShenandoahGeneration* generation, ShenandoahSharedFlag& allow_preemption) :
43 ShenandoahConcurrentGC(generation, false), _allow_preemption(allow_preemption) {
44 }
45
46 // Final mark for old-gen is different than for young or old, so we
47 // override the implementation.
48 void ShenandoahOldGC::op_final_mark() {
49
50 ShenandoahHeap* const heap = ShenandoahHeap::heap();
51 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
52 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
53
54 if (ShenandoahVerify) {
55 heap->verifier()->verify_roots_no_forwarded();
56 }
57
58 if (!heap->cancelled_gc()) {
59 assert(_mark.generation()->is_old(), "Generation of Old-Gen GC should be OLD");
60 _mark.finish_mark();
61 assert(!heap->cancelled_gc(), "STW mark cannot OOM");
62
63 // Old collection is complete, the young generation no longer needs this
64 // reference to the old concurrent mark so clean it up.
65 heap->young_generation()->set_old_gen_task_queues(nullptr);
66
67 // We need to do this because weak root cleaning reports the number of dead handles
68 JvmtiTagMap::set_needs_cleaning();
69
70 _generation->prepare_regions_and_collection_set(true);
71
72 heap->set_unload_classes(false);
73 heap->prepare_concurrent_roots();
74
75 // Believe verification following old-gen concurrent mark needs to be different than verification following
76 // young-gen concurrent mark, so am commenting this out for now:
77 // if (ShenandoahVerify) {
78 // heap->verifier()->verify_after_concmark();
79 // }
80
81 if (VerifyAfterGC) {
82 Universe::verify();
83 }
84 }
85 }
86
87 bool ShenandoahOldGC::collect(GCCause::Cause cause) {
88 ShenandoahHeap* heap = ShenandoahHeap::heap();
89 assert(!heap->doing_mixed_evacuations(), "Should not start an old gc with pending mixed evacuations");
90 assert(!heap->is_prepare_for_old_mark_in_progress(), "Old regions need to be parseable during concurrent mark.");
91
92 // Enable preemption of old generation mark.
93 _allow_preemption.set();
94
95 // Continue concurrent mark, do not reset regions, do not mark roots, do not collect $200.
96 entry_mark();
97
98 // If we failed to unset the preemption flag, it means another thread has already unset it.
99 if (!_allow_preemption.try_unset()) {
100 // The regulator thread has unset the preemption guard. That thread will shortly cancel
101 // the gc, but the control thread is now racing it. Wait until this thread sees the
102 // cancellation.
103 while (!heap->cancelled_gc()) {
104 SpinPause();
105 }
106 }
107
108 if (heap->cancelled_gc()) {
109 return false;
110 }
111
112 // Complete marking under STW
113 vmop_entry_final_mark();
114
115 // We aren't dealing with old generation evacuation yet. Our heuristic
116 // should not have built a cset in final mark.
117 assert(!heap->is_evacuation_in_progress(), "Old gen evacuations are not supported");
118
119 // Process weak roots that might still point to regions that would be broken by cleanup
120 if (heap->is_concurrent_weak_root_in_progress()) {
121 entry_weak_refs();
122 entry_weak_roots();
123 }
124
125 // Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
126 // the space. This would be the last action if there is nothing to evacuate.
127 entry_cleanup_early();
128
129 {
130 ShenandoahHeapLocker locker(heap->lock());
131 heap->free_set()->log_status();
132 }
133
134
135 // TODO: Old marking doesn't support class unloading yet
136 // Perform concurrent class unloading
137 // if (heap->unload_classes() &&
138 // heap->is_concurrent_weak_root_in_progress()) {
139 // entry_class_unloading();
140 // }
141
142
143 assert(!heap->is_concurrent_strong_root_in_progress(), "No evacuations during old gc.");
144
145 // We must execute this vm operation if we completed final mark. We cannot
146 // return from here with weak roots in progress. This is not a valid gc state
147 // for any young collections (or allocation failures) that interrupt the old
148 // collection.
149 vmop_entry_final_roots();
150
151 // We do not rebuild_free following increments of old marking because memory has not been reclaimed.. However, we may
152 // need to transfer memory to OLD in order to efficiently support the mixed evacuations that might immediately follow.
153 size_t allocation_runway = heap->young_heuristics()->bytes_of_allocation_runway_before_gc_trigger(0);
154 heap->adjust_generation_sizes_for_next_cycle(allocation_runway, 0, 0);
155
156 bool success;
157 size_t region_xfer;
158 const char* region_destination;
159 ShenandoahYoungGeneration* young_gen = heap->young_generation();
160 ShenandoahGeneration* old_gen = heap->old_generation();
161 {
162 ShenandoahHeapLocker locker(heap->lock());
163
164 size_t old_region_surplus = heap->get_old_region_surplus();
165 size_t old_region_deficit = heap->get_old_region_deficit();
166 if (old_region_surplus) {
167 success = heap->generation_sizer()->transfer_to_young(old_region_surplus);
168 region_destination = "young";
169 region_xfer = old_region_surplus;
170 } else if (old_region_deficit) {
171 success = heap->generation_sizer()->transfer_to_old(old_region_deficit);
172 region_destination = "old";
173 region_xfer = old_region_deficit;
174 if (!success) {
175 ((ShenandoahOldHeuristics *) old_gen->heuristics())->trigger_cannot_expand();
176 }
177 } else {
178 region_destination = "none";
179 region_xfer = 0;
180 success = true;
181 }
182 heap->set_old_region_surplus(0);
183 heap->set_old_region_deficit(0);
184 }
185
186 // Report outside the heap lock
187 size_t young_available = young_gen->available();
188 size_t old_available = old_gen->available();
189 log_info(gc, ergo)("After old marking finished, %s " SIZE_FORMAT " regions to %s to prepare for next gc, old available: "
190 SIZE_FORMAT "%s, young_available: " SIZE_FORMAT "%s",
191 success? "successfully transferred": "failed to transfer", region_xfer, region_destination,
192 byte_size_in_proper_unit(old_available), proper_unit_for_byte_size(old_available),
193 byte_size_in_proper_unit(young_available), proper_unit_for_byte_size(young_available));
194 return true;
195 }