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/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.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, GCMemoryManager* memory_manager, bool explicit_gc, bool clear_soft_refs) :
107 _heap(heap),
108 _scope(memory_manager, 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 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
117
118 _preserved_marks_set.init(_num_workers);
119 _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC);
120 _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC);
121 for (uint i = 0; i < _num_workers; i++) {
122 _markers[i] = new G1FullGCMarker(i, _preserved_marks_set.get(i), mark_bitmap());
123 _compaction_points[i] = new G1FullGCCompactionPoint();
124 _oop_queue_set.register_queue(i, marker(i)->oop_stack());
125 _array_queue_set.register_queue(i, marker(i)->objarray_stack());
126 }
127 }
128
129 G1FullCollector::~G1FullCollector() {
130 for (uint i = 0; i < _num_workers; i++) {
131 delete _markers[i];
132 delete _compaction_points[i];
133 }
134 FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers);
135 FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points);
136 }
137
138 void G1FullCollector::prepare_collection() {
139 _heap->g1_policy()->record_full_collection_start();
140
141 _heap->print_heap_before_gc();
142 _heap->print_heap_regions();
143
144 _heap->abort_concurrent_cycle();
145 _heap->verify_before_full_collection(scope()->is_explicit_gc());
146
147 _heap->gc_prologue(true);
148 _heap->prepare_heap_for_full_collection();
149
150 reference_processor()->enable_discovery();
151 reference_processor()->setup_policy(scope()->should_clear_soft_refs());
152
153 // When collecting the permanent generation Method*s may be moving,
154 // so we either have to flush all bcp data or convert it into bci.
155 CodeCache::gc_prologue();
156
157 // We should save the marks of the currently locked biased monitors.
158 // The marking doesn't preserve the marks of biased objects.
159 BiasedLocking::preserve_marks();
160
161 // Clear and activate derived pointer collection.
162 clear_and_activate_derived_pointers();
163 }
164
165 void G1FullCollector::collect() {
166 phase1_mark_live_objects();
167 verify_after_marking();
168
169 // Don't add any more derived pointers during later phases
170 deactivate_derived_pointers();
171
172 phase2_prepare_compaction();
173
174 phase3_adjust_pointers();
175
176 phase4_do_compaction();
177 }
178
179 void G1FullCollector::complete_collection() {
180 // Restore all marks.
181 restore_marks();
182
183 // When the pointers have been adjusted and moved, we can
184 // update the derived pointer table.
185 update_derived_pointers();
186
187 BiasedLocking::restore_marks();
188 CodeCache::gc_epilogue();
189 JvmtiExport::gc_epilogue();
190
191 _heap->prepare_heap_for_mutators();
192
193 _heap->g1_policy()->record_full_collection_end();
194 _heap->gc_epilogue(true);
195
196 _heap->verify_after_full_collection();
197
198 _heap->print_heap_after_full_collection(scope()->heap_transition());
199 }
200
201 void G1FullCollector::phase1_mark_live_objects() {
202 // Recursively traverse all live objects and mark them.
203 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer());
204
205 // Do the actual marking.
206 G1FullGCMarkTask marking_task(this);
207 run_task(&marking_task);
208
209 // Process references discovered during marking.
210 G1FullGCReferenceProcessingExecutor reference_processing(this);
211 reference_processing.execute(scope()->timer(), scope()->tracer());
212
213 // Weak oops cleanup.
214 {
215 GCTraceTime(Debug, gc, phases) trace("Phase 1: Weak Processing", scope()->timer());
216 WeakProcessor::weak_oops_do(&_is_alive, &do_nothing_cl);
217 }
218
219 // Class unloading and cleanup.
220 if (ClassUnloading) {
221 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
222 // Unload classes and purge the SystemDictionary.
223 bool purged_class = SystemDictionary::do_unloading(&_is_alive, scope()->timer());
224 _heap->complete_cleaning(&_is_alive, purged_class);
225 } else {
226 GCTraceTime(Debug, gc, phases) debug("Phase 1: String and Symbol Tables Cleanup", scope()->timer());
227 // If no class unloading just clean out strings and symbols.
228 _heap->partial_cleaning(&_is_alive, true, true, G1StringDedup::is_enabled());
229 }
230
231 scope()->tracer()->report_object_count_after_gc(&_is_alive);
232 }
233
234 void G1FullCollector::phase2_prepare_compaction() {
235 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer());
236 G1FullGCPrepareTask task(this);
237 run_task(&task);
238
239 // To avoid OOM when there is memory left.
240 if (!task.has_freed_regions()) {
241 task.prepare_serial_compaction();
242 }
243 }
244
245 void G1FullCollector::phase3_adjust_pointers() {
246 // Adjust the pointers to reflect the new locations
247 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers and remembered sets", scope()->timer());
248
249 G1FullGCAdjustTask task(this);
250 run_task(&task);
251 }
252
253 void G1FullCollector::phase4_do_compaction() {
254 // Compact the heap using the compaction queues created in phase 2.
255 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer());
256 G1FullGCCompactTask task(this);
257 run_task(&task);
258
259 // Serial compact to avoid OOM when very few free regions.
260 if (serial_compaction_point()->has_regions()) {
261 task.serial_compaction();
262 }
263 }
264
265 void G1FullCollector::restore_marks() {
266 SharedRestorePreservedMarksTaskExecutor task_executor(_heap->workers());
267 _preserved_marks_set.restore(&task_executor);
268 _preserved_marks_set.reclaim();
269 }
270
271 void G1FullCollector::run_task(AbstractGangTask* task) {
272 _heap->workers()->run_task(task, _num_workers);
273 }
274
275 void G1FullCollector::verify_after_marking() {
276 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) {
277 // Only do verification if VerifyDuringGC and G1VerifyFull is set.
278 return;
279 }
280
281 HandleMark hm; // handle scope
282 #if COMPILER2_OR_JVMCI
283 DerivedPointerTableDeactivate dpt_deact;
284 #endif
285 _heap->prepare_for_verify();
286 // Note: we can verify only the heap here. When an object is
287 // marked, the previous value of the mark word (including
288 // identity hash values, ages, etc) is preserved, and the mark
289 // word is set to markOop::marked_value - effectively removing
290 // any hash values from the mark word. These hash values are
291 // used when verifying the dictionaries and so removing them
292 // from the mark word can make verification of the dictionaries
293 // fail. At the end of the GC, the original mark word values
294 // (including hash values) are restored to the appropriate
295 // objects.
296 GCTraceTime(Info, gc, verify)("Verifying During GC (full)");
297 _heap->verify(VerifyOption_G1UseFullMarking);
298 }