1 /*
2 * Copyright (c) 2017, 2018, 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/adaptiveSizePolicy.hpp"
41 #include "gc/shared/gcTraceTime.inline.hpp"
42 #include "gc/shared/preservedMarks.hpp"
43 #include "gc/shared/referenceProcessor.hpp"
44 #include "gc/shared/weakProcessor.inline.hpp"
45 #include "logging/log.hpp"
46 #include "runtime/biasedLocking.hpp"
47 #include "runtime/handles.inline.hpp"
48 #include "utilities/debug.hpp"
49
50 static void clear_and_activate_derived_pointers() {
51 #if COMPILER2_OR_JVMCI
52 DerivedPointerTable::clear();
53 #endif
54 }
55
56 static void deactivate_derived_pointers() {
57 #if COMPILER2_OR_JVMCI
58 DerivedPointerTable::set_active(false);
59 #endif
60 }
61
62 static void update_derived_pointers() {
63 #if COMPILER2_OR_JVMCI
64 DerivedPointerTable::update_pointers();
65 #endif
66 }
67
68 G1CMBitMap* G1FullCollector::mark_bitmap() {
69 return _heap->concurrent_mark()->next_mark_bitmap();
70 }
71
72 ReferenceProcessor* G1FullCollector::reference_processor() {
73 return _heap->ref_processor_stw();
74 }
75
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 AdaptiveSizePolicy to calculate
92 // the number of workers.
93 uint current_active_workers = heap->workers()->active_workers();
94 uint adaptive_worker_limit = AdaptiveSizePolicy::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, adaptive_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, adaptive_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
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
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
140 void G1FullCollector::prepare_collection() {
141 _heap->g1_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 // When collecting the permanent generation Method*s may be moving,
156 // so we either have to flush all bcp data or convert it into bci.
157 CodeCache::gc_prologue();
158
159 // We should save the marks of the currently locked biased monitors.
160 // The marking doesn't preserve the marks of biased objects.
161 BiasedLocking::preserve_marks();
162
163 // Clear and activate derived pointer collection.
164 clear_and_activate_derived_pointers();
165 }
166
167 void G1FullCollector::collect() {
168 phase1_mark_live_objects();
169 verify_after_marking();
170
171 // Don't add any more derived pointers during later phases
172 deactivate_derived_pointers();
173
174 phase2_prepare_compaction();
175
176 phase3_adjust_pointers();
177
178 phase4_do_compaction();
179 }
180
181 void G1FullCollector::complete_collection() {
182 // Restore all marks.
183 restore_marks();
184
185 // When the pointers have been adjusted and moved, we can
186 // update the derived pointer table.
187 update_derived_pointers();
188
189 BiasedLocking::restore_marks();
190 CodeCache::gc_epilogue();
191 JvmtiExport::gc_epilogue();
192
193 _heap->prepare_heap_for_mutators();
194
195 _heap->g1_policy()->record_full_collection_end();
196
197 _heap->gc_epilogue(true);
198
199 _heap->verify_after_full_collection();
200
201 _heap->print_heap_after_full_collection(scope()->heap_transition());
202 }
203
204 void G1FullCollector::phase1_mark_live_objects() {
205 // Recursively traverse all live objects and mark them.
206 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
207
208 // Do the actual marking.
209 G1FullGCMarkTask marking_task(this);
210 run_task(&marking_task);
211
212 // Process references discovered during marking.
213 G1FullGCReferenceProcessingExecutor reference_processing(this);
214 reference_processing.execute(scope()->timer(), scope()->tracer());
215
216 // Weak oops cleanup.
217 {
218 GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer());
219 WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1);
220 }
221
222 // Class unloading and cleanup.
223 if (ClassUnloading) {
224 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
225 // Unload classes and purge the SystemDictionary.
226 bool purged_class = SystemDictionary::do_unloading(scope()->timer());
227 _heap->complete_cleaning(&_is_alive, purged_class);
228 } else {
229 GCTraceTime(Debug, gc, phases) debug("Phase 1: String and Symbol Tables Cleanup", scope()->timer());
230 // If no class unloading just clean out strings.
231 _heap->partial_cleaning(&_is_alive, true, G1StringDedup::is_enabled());
232 }
233
234 scope()->tracer()->report_object_count_after_gc(&_is_alive);
235 }
236
237 void G1FullCollector::phase2_prepare_compaction() {
238 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer());
239 G1FullGCPrepareTask task(this);
240 run_task(&task);
241
242 // To avoid OOM when there is memory left.
243 if (!task.has_freed_regions()) {
244 task.prepare_serial_compaction();
245 }
246 }
247
248 void G1FullCollector::phase3_adjust_pointers() {
249 // Adjust the pointers to reflect the new locations
250 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
251
252 G1FullGCAdjustTask task(this);
253 run_task(&task);
254 }
255
256 void G1FullCollector::phase4_do_compaction() {
257 // Compact the heap using the compaction queues created in phase 2.
258 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
259 G1FullGCCompactTask task(this);
260 run_task(&task);
261
262 // Serial compact to avoid OOM when very few free regions.
263 if (serial_compaction_point()->has_regions()) {
264 task.serial_compaction();
265 }
266 }
267
268 void G1FullCollector::restore_marks() {
269 SharedRestorePreservedMarksTaskExecutor task_executor(_heap->workers());
270 _preserved_marks_set.restore(&task_executor);
271 _preserved_marks_set.reclaim();
272 }
273
274 void G1FullCollector::run_task(AbstractGangTask* task) {
275 _heap->workers()->run_task(task, _num_workers);
276 }
277
278 void G1FullCollector::verify_after_marking() {
279 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
280 // Only do verification if VerifyDuringGC and G1VerifyFull is set.
281 return;
282 }
283
284 HandleMark hm; // handle scope
285 #if COMPILER2_OR_JVMCI
286 DerivedPointerTableDeactivate dpt_deact;
287 #endif
288 _heap->prepare_for_verify();
289 // Note: we can verify only the heap here. When an object is
290 // marked, the previous value of the mark word (including
291 // identity hash values, ages, etc) is preserved, and the mark
292 // word is set to markOop::marked_value - effectively removing
293 // any hash values from the mark word. These hash values are
294 // used when verifying the dictionaries and so removing them
295 // from the mark word can make verification of the dictionaries
296 // fail. At the end of the GC, the original mark word values
297 // (including hash values) are restored to the appropriate
298 // objects.
299 GCTraceTime(Info, gc, verify)("Verifying During GC (full)");
300 _heap->verify(VerifyOption_G1UseFullMarking);
301 }