1 /*
2 * Copyright (c) 2017, 2019, 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/g1FullCollector.hpp"
29 #include "gc/g1/g1FullGCAdjustTask.hpp"
30 #include "gc/g1/g1FullGCCompactTask.hpp"
31 #include "gc/g1/g1FullGCMarker.inline.hpp"
32 #include "gc/g1/g1FullGCMarkTask.hpp"
33 #include "gc/g1/g1FullGCPrepareTask.hpp"
34 #include "gc/g1/g1FullGCReferenceProcessorExecutor.hpp"
35 #include "gc/g1/g1FullGCScope.hpp"
36 #include "gc/g1/g1OopClosures.hpp"
37 #include "gc/g1/g1Policy.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/verifyOption.hpp"
43 #include "gc/shared/weakProcessor.inline.hpp"
44 #include "gc/shared/workerPolicy.hpp"
45 #include "logging/log.hpp"
46 #include "runtime/biasedLocking.hpp"
47 #include "runtime/handles.inline.hpp"
48 #include "utilities/debug.hpp"
49
clear_and_activate_derived_pointers()50 static void clear_and_activate_derived_pointers() {
51 #if COMPILER2_OR_JVMCI
52 DerivedPointerTable::clear();
53 #endif
54 }
55
deactivate_derived_pointers()56 static void deactivate_derived_pointers() {
57 #if COMPILER2_OR_JVMCI
58 DerivedPointerTable::set_active(false);
59 #endif
60 }
61
update_derived_pointers()62 static void update_derived_pointers() {
63 #if COMPILER2_OR_JVMCI
64 DerivedPointerTable::update_pointers();
65 #endif
66 }
67
mark_bitmap()68 G1CMBitMap* G1FullCollector::mark_bitmap() {
69 return _heap->concurrent_mark()->next_mark_bitmap();
70 }
71
reference_processor()72 ReferenceProcessor* G1FullCollector::reference_processor() {
73 return _heap->ref_processor_stw();
74 }
75
calc_active_workers()76 uint G1FullCollector::calc_active_workers() {
77 G1CollectedHeap* heap = G1CollectedHeap::heap();
78 uint max_worker_count = heap->workers()->total_workers();
79 // Only calculate number of workers if UseDynamicNumberOfGCThreads
80 // is enabled, otherwise use max.
81 if (!UseDynamicNumberOfGCThreads) {
82 return max_worker_count;
83 }
84
85 // Consider G1HeapWastePercent to decide max number of workers. Each worker
86 // will in average cause half a region waste.
87 uint max_wasted_regions_allowed = ((heap->num_regions() * G1HeapWastePercent) / 100);
88 uint waste_worker_count = MAX2((max_wasted_regions_allowed * 2) , 1u);
89 uint heap_waste_worker_limit = MIN2(waste_worker_count, max_worker_count);
90
91 // Also consider HeapSizePerGCThread by calling WorkerPolicy to calculate
92 // the number of workers.
93 uint current_active_workers = heap->workers()->active_workers();
94 uint active_worker_limit = WorkerPolicy::calc_active_workers(max_worker_count, current_active_workers, 0);
95
96 // Update active workers to the lower of the limits.
97 uint worker_count = MIN2(heap_waste_worker_limit, active_worker_limit);
98 log_debug(gc, task)("Requesting %u active workers for full compaction (waste limited workers: %u, adaptive workers: %u)",
99 worker_count, heap_waste_worker_limit, active_worker_limit);
100 worker_count = heap->workers()->update_active_workers(worker_count);
101 log_info(gc, task)("Using %u workers of %u for full compaction", worker_count, max_worker_count);
102
103 return worker_count;
104 }
105
G1FullCollector(G1CollectedHeap * heap,bool explicit_gc,bool clear_soft_refs)106 G1FullCollector::G1FullCollector(G1CollectedHeap* heap, bool explicit_gc, bool clear_soft_refs) :
107 _heap(heap),
108 _scope(heap->g1mm(), explicit_gc, clear_soft_refs),
109 _num_workers(calc_active_workers()),
110 _oop_queue_set(_num_workers),
111 _array_queue_set(_num_workers),
112 _preserved_marks_set(true),
113 _serial_compaction_point(),
114 _is_alive(heap->concurrent_mark()->next_mark_bitmap()),
115 _is_alive_mutator(heap->ref_processor_stw(), &_is_alive),
116 _always_subject_to_discovery(),
117 _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery) {
118 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
119
120 _preserved_marks_set.init(_num_workers);
121 _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
122 _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
123 for (uint i = 0; i < _num_workers; i++) {
124 _markers[i] = new G1FullGCMarker(i, _preserved_marks_set.get(i), mark_bitmap());
125 _compaction_points[i] = new G1FullGCCompactionPoint();
126 _oop_queue_set.register_queue(i, marker(i)->oop_stack());
127 _array_queue_set.register_queue(i, marker(i)->objarray_stack());
128 }
129 }
130
~G1FullCollector()131 G1FullCollector::~G1FullCollector() {
132 for (uint i = 0; i < _num_workers; i++) {
133 delete _markers[i];
134 delete _compaction_points[i];
135 }
136 FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
137 FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
138 }
139
prepare_collection()140 void G1FullCollector::prepare_collection() {
141 _heap->policy()->record_full_collection_start();
142
143 _heap->print_heap_before_gc();
144 _heap->print_heap_regions();
145
146 _heap->abort_concurrent_cycle();
147 _heap->verify_before_full_collection(scope()->is_explicit_gc());
148
149 _heap->gc_prologue(true);
150 _heap->prepare_heap_for_full_collection();
151
152 reference_processor()->enable_discovery();
153 reference_processor()->setup_policy(scope()->should_clear_soft_refs());
154
155 // We should save the marks of the currently locked biased monitors.
156 // The marking doesn't preserve the marks of biased objects.
157 BiasedLocking::preserve_marks();
158
159 // Clear and activate derived pointer collection.
160 clear_and_activate_derived_pointers();
161 }
162
collect()163 void G1FullCollector::collect() {
164 phase1_mark_live_objects();
165 verify_after_marking();
166
167 // Don't add any more derived pointers during later phases
168 deactivate_derived_pointers();
169
170 phase2_prepare_compaction();
171
172 phase3_adjust_pointers();
173
174 phase4_do_compaction();
175 }
176
complete_collection()177 void G1FullCollector::complete_collection() {
178 // Restore all marks.
179 restore_marks();
180
181 // When the pointers have been adjusted and moved, we can
182 // update the derived pointer table.
183 update_derived_pointers();
184
185 BiasedLocking::restore_marks();
186 JvmtiExport::gc_epilogue();
187
188 _heap->prepare_heap_for_mutators();
189
190 _heap->policy()->record_full_collection_end();
191 _heap->gc_epilogue(true);
192
193 _heap->verify_after_full_collection();
194
195 _heap->print_heap_after_full_collection(scope()->heap_transition());
196 }
197
phase1_mark_live_objects()198 void G1FullCollector::phase1_mark_live_objects() {
199 // Recursively traverse all live objects and mark them.
200 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
201
202 // Do the actual marking.
203 G1FullGCMarkTask marking_task(this);
204 run_task(&marking_task);
205
206 // Process references discovered during marking.
207 G1FullGCReferenceProcessingExecutor reference_processing(this);
208 reference_processing.execute(scope()->timer(), scope()->tracer());
209
210 // Weak oops cleanup.
211 {
212 GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
213 WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
214 }
215
216 // Class unloading and cleanup.
217 if (ClassUnloading) {
218 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
219 // Unload classes and purge the SystemDictionary.
220 bool purged_class = SystemDictionary::do_unloading(scope()->timer());
221 _heap->complete_cleaning(&_is_alive, purged_class);
222 } else if (G1StringDedup::is_enabled()) {
223 GCTraceTime(Debug, gc, phases) debug("Phase 1: String Dedup Cleanup", scope()->timer());
224 // If no class unloading just clean out string deduplication data.
225 _heap->string_dedup_cleaning(&_is_alive, NULL);
226 }
227
228 scope()->tracer()->report_object_count_after_gc(&_is_alive);
229 }
230
phase2_prepare_compaction()231 void G1FullCollector::phase2_prepare_compaction() {
232 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer());
233 G1FullGCPrepareTask task(this);
234 run_task(&task);
235
236 // To avoid OOM when there is memory left.
237 if (!task.has_freed_regions()) {
238 task.prepare_serial_compaction();
239 }
240 }
241
phase3_adjust_pointers()242 void G1FullCollector::phase3_adjust_pointers() {
243 // Adjust the pointers to reflect the new locations
244 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
245
246 G1FullGCAdjustTask task(this);
247 run_task(&task);
248 }
249
phase4_do_compaction()250 void G1FullCollector::phase4_do_compaction() {
251 // Compact the heap using the compaction queues created in phase 2.
252 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
253 G1FullGCCompactTask task(this);
254 run_task(&task);
255
256 // Serial compact to avoid OOM when very few free regions.
257 if (serial_compaction_point()->has_regions()) {
258 task.serial_compaction();
259 }
260 }
261
restore_marks()262 void G1FullCollector::restore_marks() {
263 SharedRestorePreservedMarksTaskExecutor task_executor(_heap->workers());
264 _preserved_marks_set.restore(&task_executor);
265 _preserved_marks_set.reclaim();
266 }
267
run_task(AbstractGangTask * task)268 void G1FullCollector::run_task(AbstractGangTask* task) {
269 _heap->workers()->run_task(task, _num_workers);
270 }
271
verify_after_marking()272 void G1FullCollector::verify_after_marking() {
273 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
274 // Only do verification if VerifyDuringGC and G1VerifyFull is set.
275 return;
276 }
277
278 HandleMark hm; // handle scope
279 #if COMPILER2_OR_JVMCI
280 DerivedPointerTableDeactivate dpt_deact;
281 #endif
282 _heap->prepare_for_verify();
283 // Note: we can verify only the heap here. When an object is
284 // marked, the previous value of the mark word (including
285 // identity hash values, ages, etc) is preserved, and the mark
286 // word is set to markOop::marked_value - effectively removing
287 // any hash values from the mark word. These hash values are
288 // used when verifying the dictionaries and so removing them
289 // from the mark word can make verification of the dictionaries
290 // fail. At the end of the GC, the original mark word values
291 // (including hash values) are restored to the appropriate
292 // objects.
293 GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)");
294 _heap->verify(VerifyOption_G1UseFullMarking);
295 }
296