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/g1Policy.hpp"
39 #include "gc/g1/g1StringDedup.hpp"
40 #include "gc/shared/gcTraceTime.inline.hpp"
41 #include "gc/shared/preservedMarks.hpp"
42 #include "gc/shared/referenceProcessor.hpp"
43 #include "gc/shared/weakProcessor.hpp"
44 #include "logging/log.hpp"
45 #include "runtime/biasedLocking.hpp"
46 #include "runtime/handles.inline.hpp"
47 #include "utilities/debug.hpp"
48
49 static void clear_and_activate_derived_pointers() {
50 #if COMPILER2_OR_JVMCI
51 DerivedPointerTable::clear();
52 #endif
53 }
54
55 static void deactivate_derived_pointers() {
56 #if COMPILER2_OR_JVMCI
57 DerivedPointerTable::set_active(false);
58 #endif
59 }
60
61 static void update_derived_pointers() {
62 #if COMPILER2_OR_JVMCI
63 DerivedPointerTable::update_pointers();
64 #endif
65 }
66
67 G1CMBitMap* G1FullCollector::mark_bitmap() {
68 return _heap->concurrent_mark()->next_mark_bitmap();
69 }
70
71 ReferenceProcessor* G1FullCollector::reference_processor() {
72 return _heap->ref_processor_stw();
73 }
74
75 G1FullCollector::G1FullCollector(G1CollectedHeap* heap, GCMemoryManager* memory_manager, bool explicit_gc, bool clear_soft_refs) :
76 _heap(heap),
77 _scope(memory_manager, explicit_gc, clear_soft_refs),
78 _num_workers(heap->workers()->active_workers()),
79 _oop_queue_set(_num_workers),
80 _array_queue_set(_num_workers),
81 _preserved_marks_set(true),
82 _serial_compaction_point(),
83 _is_alive(heap->concurrent_mark()->next_mark_bitmap()),
84 _is_alive_mutator(heap->ref_processor_stw(), &_is_alive),
85 _always_subject_to_discovery(),
86 _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery) {
87 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
88
89 _preserved_marks_set.init(_num_workers);
90 _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
91 _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
92 for (uint i = 0; i < _num_workers; i++) {
93 _markers[i] = new G1FullGCMarker(i, _preserved_marks_set.get(i), mark_bitmap());
94 _compaction_points[i] = new G1FullGCCompactionPoint();
95 _oop_queue_set.register_queue(i, marker(i)->oop_stack());
96 _array_queue_set.register_queue(i, marker(i)->objarray_stack());
97 }
98 }
99
100 G1FullCollector::~G1FullCollector() {
101 for (uint i = 0; i < _num_workers; i++) {
102 delete _markers[i];
103 delete _compaction_points[i];
104 }
105 FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
106 FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
107 }
108
109 void G1FullCollector::prepare_collection() {
110 _heap->g1_policy()->record_full_collection_start();
111
112 _heap->print_heap_before_gc();
113 _heap->print_heap_regions();
114
115 _heap->abort_concurrent_cycle();
116 _heap->verify_before_full_collection(scope()->is_explicit_gc());
117
118 _heap->gc_prologue(true);
119 _heap->prepare_heap_for_full_collection();
120
121 reference_processor()->enable_discovery();
122 reference_processor()->setup_policy(scope()->should_clear_soft_refs());
123
124 // When collecting the permanent generation Method*s may be moving,
125 // so we either have to flush all bcp data or convert it into bci.
126 CodeCache::gc_prologue();
127
128 // We should save the marks of the currently locked biased monitors.
129 // The marking doesn't preserve the marks of biased objects.
130 BiasedLocking::preserve_marks();
131
132 // Clear and activate derived pointer collection.
133 clear_and_activate_derived_pointers();
134 }
135
136 void G1FullCollector::collect() {
137 phase1_mark_live_objects();
138 verify_after_marking();
139
140 // Don't add any more derived pointers during later phases
141 deactivate_derived_pointers();
142
143 phase2_prepare_compaction();
144
145 phase3_adjust_pointers();
146
147 phase4_do_compaction();
148 }
149
150 void G1FullCollector::complete_collection() {
151 // Restore all marks.
152 restore_marks();
153
154 // When the pointers have been adjusted and moved, we can
155 // update the derived pointer table.
156 update_derived_pointers();
157
158 BiasedLocking::restore_marks();
159 CodeCache::gc_epilogue();
160 JvmtiExport::gc_epilogue();
161
162 _heap->prepare_heap_for_mutators();
163
164 _heap->g1_policy()->record_full_collection_end();
165 _heap->gc_epilogue(true);
166
167 _heap->verify_after_full_collection();
168
169 _heap->print_heap_after_full_collection(scope()->heap_transition());
170 }
171
172 void G1FullCollector::phase1_mark_live_objects() {
173 // Recursively traverse all live objects and mark them.
174 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
175
176 // Do the actual marking.
177 G1FullGCMarkTask marking_task(this);
178 run_task(&marking_task);
179
180 // Process references discovered during marking.
181 G1FullGCReferenceProcessingExecutor reference_processing(this);
182 reference_processing.execute(scope()->timer(), scope()->tracer());
183
184 // Weak oops cleanup.
185 {
186 GCTraceTime(Debug, gc, phases) trace("Phase 1: Weak Processing", scope()->timer());
187 WeakProcessor::weak_oops_do(&_is_alive, &do_nothing_cl);
188 }
189
190 // Class unloading and cleanup.
191 if (ClassUnloading) {
192 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
193 // Unload classes and purge the SystemDictionary.
194 bool purged_class = SystemDictionary::do_unloading(&_is_alive, scope()->timer());
195 _heap->complete_cleaning(&_is_alive, purged_class);
196 } else {
197 GCTraceTime(Debug, gc, phases) debug("Phase 1: String and Symbol Tables Cleanup", scope()->timer());
198 // If no class unloading just clean out strings and symbols.
199 _heap->partial_cleaning(&_is_alive, true, true, G1StringDedup::is_enabled());
200 }
201
202 scope()->tracer()->report_object_count_after_gc(&_is_alive);
203 }
204
205 void G1FullCollector::phase2_prepare_compaction() {
206 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer());
207 G1FullGCPrepareTask task(this);
208 run_task(&task);
209
210 // To avoid OOM when there is memory left.
211 if (!task.has_freed_regions()) {
212 task.prepare_serial_compaction();
213 }
214 }
215
216 void G1FullCollector::phase3_adjust_pointers() {
217 // Adjust the pointers to reflect the new locations
218 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
219
220 G1FullGCAdjustTask task(this);
221 run_task(&task);
222 }
223
224 void G1FullCollector::phase4_do_compaction() {
225 // Compact the heap using the compaction queues created in phase 2.
226 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
227 G1FullGCCompactTask task(this);
228 run_task(&task);
229
230 // Serial compact to avoid OOM when very few free regions.
231 if (serial_compaction_point()->has_regions()) {
232 task.serial_compaction();
233 }
234 }
235
236 void G1FullCollector::restore_marks() {
237 SharedRestorePreservedMarksTaskExecutor task_executor(_heap->workers());
238 _preserved_marks_set.restore(&task_executor);
239 _preserved_marks_set.reclaim();
240 }
241
242 void G1FullCollector::run_task(AbstractGangTask* task) {
243 _heap->workers()->run_task(task, _num_workers);
244 }
245
246 void G1FullCollector::verify_after_marking() {
247 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
248 // Only do verification if VerifyDuringGC and G1VerifyFull is set.
249 return;
250 }
251
252 HandleMark hm; // handle scope
253 #if COMPILER2_OR_JVMCI
254 DerivedPointerTableDeactivate dpt_deact;
255 #endif
256 _heap->prepare_for_verify();
257 // Note: we can verify only the heap here. When an object is
258 // marked, the previous value of the mark word (including
259 // identity hash values, ages, etc) is preserved, and the mark
260 // word is set to markOop::marked_value - effectively removing
261 // any hash values from the mark word. These hash values are
262 // used when verifying the dictionaries and so removing them
263 // from the mark word can make verification of the dictionaries
264 // fail. At the end of the GC, the original mark word values
265 // (including hash values) are restored to the appropriate
266 // objects.
267 GCTraceTime(Info, gc, verify)("Verifying During GC (full)");
268 _heap->verify(VerifyOption_G1UseFullMarking);
269 }