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/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.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 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 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 } 105 106 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->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->policy()->record_full_collection_end(); 196 _heap->gc_epilogue(true); 197 198 _heap->verify_after_full_collection(); 199 200 _heap->print_heap_after_full_collection(scope()->heap_transition()); 201 } 202 203 void G1FullCollector::phase1_mark_live_objects() { 204 // Recursively traverse all live objects and mark them. 205 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer()); 206 207 // Do the actual marking. 208 G1FullGCMarkTask marking_task(this); 209 run_task(&marking_task); 210 211 // Process references discovered during marking. 212 G1FullGCReferenceProcessingExecutor reference_processing(this); 213 reference_processing.execute(scope()->timer(), scope()->tracer()); 214 215 // Weak oops cleanup. 216 { 217 GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer()); 218 WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1); 219 } 220 221 // Class unloading and cleanup. 222 if (ClassUnloading) { 223 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer()); 224 // Unload classes and purge the SystemDictionary. 225 bool purged_class = SystemDictionary::do_unloading(scope()->timer()); 226 _heap->complete_cleaning(&_is_alive, purged_class); 227 } else if (G1StringDedup::is_enabled()) { 228 GCTraceTime(Debug, gc, phases) debug("Phase 1: String Dedup Cleanup", scope()->timer()); 229 // If no class unloading just clean out string deduplication data. 230 _heap->string_dedup_cleaning(&_is_alive, NULL); 231 } 232 233 scope()->tracer()->report_object_count_after_gc(&_is_alive); 234 } 235 236 void G1FullCollector::phase2_prepare_compaction() { 237 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare for compaction", scope()->timer()); 238 G1FullGCPrepareTask task(this); 239 run_task(&task); 240 241 // To avoid OOM when there is memory left. 242 if (!task.has_freed_regions()) { 243 task.prepare_serial_compaction(); 244 } 245 } 246 247 void G1FullCollector::phase3_adjust_pointers() { 248 // Adjust the pointers to reflect the new locations 249 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer()); 250 251 G1FullGCAdjustTask task(this); 252 run_task(&task); 253 } 254 255 void G1FullCollector::phase4_do_compaction() { 256 // Compact the heap using the compaction queues created in phase 2. 257 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer()); 258 G1FullGCCompactTask task(this); 259 run_task(&task); 260 261 // Serial compact to avoid OOM when very few free regions. 262 if (serial_compaction_point()->has_regions()) { 263 task.serial_compaction(); 264 } 265 } 266 267 void G1FullCollector::restore_marks() { 268 SharedRestorePreservedMarksTaskExecutor task_executor(_heap->workers()); 269 _preserved_marks_set.restore(&task_executor); 270 _preserved_marks_set.reclaim(); 271 } 272 273 void G1FullCollector::run_task(AbstractGangTask* task) { 274 _heap->workers()->run_task(task, _num_workers); 275 } 276 277 void G1FullCollector::verify_after_marking() { 278 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) { 279 // Only do verification if VerifyDuringGC and G1VerifyFull is set. 280 return; 281 } 282 283 HandleMark hm; // handle scope 284 #if COMPILER2_OR_JVMCI 285 DerivedPointerTableDeactivate dpt_deact; 286 #endif 287 _heap->prepare_for_verify(); 288 // Note: we can verify only the heap here. When an object is 289 // marked, the previous value of the mark word (including 290 // identity hash values, ages, etc) is preserved, and the mark 291 // word is set to markOop::marked_value - effectively removing 292 // any hash values from the mark word. These hash values are 293 // used when verifying the dictionaries and so removing them 294 // from the mark word can make verification of the dictionaries 295 // fail. At the end of the GC, the original mark word values 296 // (including hash values) are restored to the appropriate 297 // objects. 298 GCTraceTime(Info, gc, verify)("Verifying During GC (full)"); 299 _heap->verify(VerifyOption_G1UseFullMarking); 300 }