1 /*
2 * Copyright (c) 2017, Oracle and/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 #include "code/codeCache.hpp"
27 #include "gc/g1/g1CollectedHeap.hpp"
28 #include "gc/g1/g1CollectorPolicy.hpp"
29 #include "gc/g1/g1FullCollector.hpp"
30 #include "gc/g1/g1FullGCAdjustTask.hpp"
31 #include "gc/g1/g1FullGCCompactTask.hpp"
32 #include "gc/g1/g1FullGCMarker.inline.hpp"
33 #include "gc/g1/g1FullGCMarkTask.hpp"
34 #include "gc/g1/g1FullGCPrepareTask.hpp"
35 #include "gc/g1/g1FullGCReferenceProcessorExecutor.hpp"
36 #include "gc/g1/g1FullGCScope.hpp"
37 #include "gc/g1/g1OopClosures.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/shared/gcTraceTime.inline.hpp"
40 #include "gc/shared/preservedMarks.hpp"
41 #include "gc/shared/referenceProcessor.hpp"
42 #include "gc/shared/weakProcessor.hpp"
43 #include "logging/log.hpp"
44 #include "runtime/biasedLocking.hpp"
45 #include "utilities/debug.hpp"
46
47 static void clear_and_activate_derived_pointers() {
48 #if COMPILER2_OR_JVMCI
49 DerivedPointerTable::clear();
50 #endif
51 }
52
53 static void deactivate_derived_pointers() {
54 #if COMPILER2_OR_JVMCI
55 DerivedPointerTable::set_active(false);
56 #endif
57 }
58
59 static void update_derived_pointers() {
60 #if COMPILER2_OR_JVMCI
61 DerivedPointerTable::update_pointers();
62 #endif
63 }
64
65 G1FullCollector::G1FullCollector(G1FullGCScope* scope,
66 ReferenceProcessor* reference_processor,
67 G1CMBitMap* bitmap,
68 uint workers) :
69 _scope(scope),
70 _num_workers(workers),
71 _mark_bitmap(bitmap),
72 _oop_queue_set(_num_workers),
73 _array_queue_set(_num_workers),
74 _preserved_marks_set(true),
75 _reference_processor(reference_processor),
76 _serial_compaction_point(),
77 _is_alive(_mark_bitmap),
78 _is_alive_mutator(_reference_processor, &_is_alive) {
79 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
80
81 _preserved_marks_set.init(_num_workers);
82 _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
83 _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
84 for (uint i = 0; i < _num_workers; i++) {
85 _markers[i] = new G1FullGCMarker(i, _preserved_marks_set.get(i), mark_bitmap());
86 _compaction_points[i] = new G1FullGCCompactionPoint();
87 _oop_queue_set.register_queue(i, marker(i)->oop_stack());
88 _array_queue_set.register_queue(i, marker(i)->objarray_stack());
89 }
90 }
91
92 G1FullCollector::~G1FullCollector() {
93 for (uint i = 0; i < _num_workers; i++) {
94 delete _markers[i];
95 delete _compaction_points[i];
96 }
97 FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
98 FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
99 }
100
101 void G1FullCollector::prepare_collection() {
102 _reference_processor->enable_discovery();
103 _reference_processor->setup_policy(scope()->should_clear_soft_refs());
104
105 // When collecting the permanent generation Method*s may be moving,
106 // so we either have to flush all bcp data or convert it into bci.
107 CodeCache::gc_prologue();
108
109 // We should save the marks of the currently locked biased monitors.
110 // The marking doesn't preserve the marks of biased objects.
111 BiasedLocking::preserve_marks();
112
113 // Clear and activate derived pointer collection.
114 clear_and_activate_derived_pointers();
115 }
116
117 void G1FullCollector::collect() {
118 phase1_mark_live_objects();
119 verify_after_marking();
120
121 // Don't add any more derived pointers during later phases
122 deactivate_derived_pointers();
123
124 phase2_prepare_compaction();
125
126 phase3_adjust_pointers();
127
128 phase4_do_compaction();
129 }
130
131 void G1FullCollector::complete_collection() {
132 // Restore all marks.
133 restore_marks();
134
135 // When the pointers have been adjusted and moved, we can
136 // update the derived pointer table.
137 update_derived_pointers();
138
139 BiasedLocking::restore_marks();
140 CodeCache::gc_epilogue();
141 JvmtiExport::gc_epilogue();
142 }
143
144 void G1FullCollector::phase1_mark_live_objects() {
145 // Recursively traverse all live objects and mark them.
146 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
147
148 // Do the actual marking.
149 G1FullGCMarkTask marking_task(this);
150 run_task(&marking_task);
151
152 // Process references discovered during marking.
153 G1FullGCReferenceProcessingExecutor reference_processing(this);
154 reference_processing.execute(scope()->timer(), scope()->tracer());
155
156 // Weak oops cleanup.
157 {
158 GCTraceTime(Debug, gc, phases) trace("Phase 1: Weak Processing", scope()->timer());
159 WeakProcessor::weak_oops_do(&_is_alive, &do_nothing_cl);
160 }
161
162 // Class unloading and cleanup.
163 if (ClassUnloading) {
164 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
165 // Unload classes and purge the SystemDictionary.
166 bool purged_class = SystemDictionary::do_unloading(&_is_alive, scope()->timer());
167 G1CollectedHeap::heap()->complete_cleaning(&_is_alive, purged_class);
168 } else {
169 GCTraceTime(Debug, gc, phases) debug("Phase 1: String and Symbol Tables Cleanup", scope()->timer());
170 // If no class unloading just clean out strings and symbols.
171 G1CollectedHeap::heap()->partial_cleaning(&_is_alive, true, true, G1StringDedup::is_enabled());
172 }
173
174 scope()->tracer()->report_object_count_after_gc(&_is_alive);
175 }
176
177 void G1FullCollector::prepare_compaction_common() {
178 G1FullGCPrepareTask task(this);
179 run_task(&task);
180
181 // To avoid OOM when there is memory left.
182 if (!task.has_freed_regions()) {
183 task.prepare_serial_compaction();
184 }
185 }
186
187 void G1FullCollector::phase2_prepare_compaction() {
188 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer());
189 prepare_compaction_ext(); // Will call prepare_compaction_common() above.
190 }
191
192 void G1FullCollector::phase3_adjust_pointers() {
193 // Adjust the pointers to reflect the new locations
194 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers and remembered sets", scope()->timer());
195
196 G1FullGCAdjustTask task(this);
197 run_task(&task);
198 }
199
200 void G1FullCollector::phase4_do_compaction() {
201 // Compact the heap using the compaction queues created in phase 2.
202 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
203 G1FullGCCompactTask task(this);
204 run_task(&task);
205
206 // Serial compact to avoid OOM when very few free regions.
207 if (serial_compaction_point()->has_regions()) {
208 task.serial_compaction();
209 }
210 }
211
212 void G1FullCollector::restore_marks() {
213 SharedRestorePreservedMarksTaskExecutor task_executor(G1CollectedHeap::heap()->workers());
214 _preserved_marks_set.restore(&task_executor);
215 _preserved_marks_set.reclaim();
216 }
217
218 void G1FullCollector::run_task(AbstractGangTask* task) {
219 G1CollectedHeap::heap()->workers()->run_task(task, _num_workers);
220 }
221
222 void G1FullCollector::verify_after_marking() {
223 if (!VerifyDuringGC) {
224 //Only do verification if VerifyDuringGC is set.
225 return;
226 }
227
228 HandleMark hm; // handle scope
229 #if COMPILER2_OR_JVMCI
230 DerivedPointerTableDeactivate dpt_deact;
231 #endif
232 G1CollectedHeap::heap()->prepare_for_verify();
233 // Note: we can verify only the heap here. When an object is
234 // marked, the previous value of the mark word (including
235 // identity hash values, ages, etc) is preserved, and the mark
236 // word is set to markOop::marked_value - effectively removing
237 // any hash values from the mark word. These hash values are
238 // used when verifying the dictionaries and so removing them
239 // from the mark word can make verification of the dictionaries
240 // fail. At the end of the GC, the original mark word values
241 // (including hash values) are restored to the appropriate
242 // objects.
243 GCTraceTime(Info, gc, verify)("During GC (full)");
244 G1CollectedHeap::heap()->verify(VerifyOption_G1UseFullMarking);
245 }