1 /* 2 * Copyright (c) 2017, 2023, 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 "classfile/classLoaderDataGraph.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "code/codeCache.hpp" 29 #include "compiler/oopMap.hpp" 30 #include "gc/g1/g1CollectedHeap.hpp" 31 #include "gc/g1/g1FullCollector.inline.hpp" 32 #include "gc/g1/g1FullGCAdjustTask.hpp" 33 #include "gc/g1/g1FullGCCompactTask.hpp" 34 #include "gc/g1/g1FullGCMarker.inline.hpp" 35 #include "gc/g1/g1FullGCMarkTask.hpp" 36 #include "gc/g1/g1FullGCPrepareTask.inline.hpp" 37 #include "gc/g1/g1FullGCResetMetadataTask.hpp" 38 #include "gc/g1/g1FullGCScope.hpp" 39 #include "gc/g1/g1OopClosures.hpp" 40 #include "gc/g1/g1Policy.hpp" 41 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp" 42 #include "gc/shared/gcTraceTime.inline.hpp" 43 #include "gc/shared/preservedMarks.hpp" 44 #include "gc/shared/referenceProcessor.hpp" 45 #include "gc/shared/verifyOption.hpp" 46 #include "gc/shared/weakProcessor.inline.hpp" 47 #include "gc/shared/workerPolicy.hpp" 48 #include "logging/log.hpp" 49 #include "runtime/handles.inline.hpp" 50 #include "utilities/debug.hpp" 51 52 static void clear_and_activate_derived_pointers() { 53 #if COMPILER2_OR_JVMCI 54 DerivedPointerTable::clear(); 55 #endif 56 } 57 58 static void deactivate_derived_pointers() { 59 #if COMPILER2_OR_JVMCI 60 DerivedPointerTable::set_active(false); 61 #endif 62 } 63 64 static void update_derived_pointers() { 65 #if COMPILER2_OR_JVMCI 66 DerivedPointerTable::update_pointers(); 67 #endif 68 } 69 70 G1CMBitMap* G1FullCollector::mark_bitmap() { 71 return _heap->concurrent_mark()->mark_bitmap(); 72 } 73 74 ReferenceProcessor* G1FullCollector::reference_processor() { 75 return _heap->ref_processor_stw(); 76 } 77 78 uint G1FullCollector::calc_active_workers() { 79 G1CollectedHeap* heap = G1CollectedHeap::heap(); 80 uint max_worker_count = heap->workers()->max_workers(); 81 // Only calculate number of workers if UseDynamicNumberOfGCThreads 82 // is enabled, otherwise use max. 83 if (!UseDynamicNumberOfGCThreads) { 84 return max_worker_count; 85 } 86 87 // Consider G1HeapWastePercent to decide max number of workers. Each worker 88 // will in average cause half a region waste. 89 uint max_wasted_regions_allowed = ((heap->num_regions() * G1HeapWastePercent) / 100); 90 uint waste_worker_count = MAX2((max_wasted_regions_allowed * 2) , 1u); 91 uint heap_waste_worker_limit = MIN2(waste_worker_count, max_worker_count); 92 93 // Also consider HeapSizePerGCThread by calling WorkerPolicy to calculate 94 // the number of workers. 95 uint current_active_workers = heap->workers()->active_workers(); 96 uint active_worker_limit = WorkerPolicy::calc_active_workers(max_worker_count, current_active_workers, 0); 97 98 // Finally consider the amount of used regions. 99 uint used_worker_limit = heap->num_used_regions(); 100 assert(used_worker_limit > 0, "Should never have zero used regions."); 101 102 // Update active workers to the lower of the limits. 103 uint worker_count = MIN3(heap_waste_worker_limit, active_worker_limit, used_worker_limit); 104 log_debug(gc, task)("Requesting %u active workers for full compaction (waste limited workers: %u, " 105 "adaptive workers: %u, used limited workers: %u)", 106 worker_count, heap_waste_worker_limit, active_worker_limit, used_worker_limit); 107 worker_count = heap->workers()->set_active_workers(worker_count); 108 log_info(gc, task)("Using %u workers of %u for full compaction", worker_count, max_worker_count); 109 110 return worker_count; 111 } 112 113 G1FullCollector::G1FullCollector(G1CollectedHeap* heap, 114 bool explicit_gc, 115 bool clear_soft_refs, 116 bool do_maximal_compaction, 117 G1FullGCTracer* tracer) : 118 _heap(heap), 119 _scope(heap->monitoring_support(), explicit_gc, clear_soft_refs, do_maximal_compaction, tracer), 120 _num_workers(calc_active_workers()), 121 _has_compaction_targets(false), 122 _oop_queue_set(_num_workers), 123 _array_queue_set(_num_workers), 124 _preserved_marks_set(true), 125 _serial_compaction_point(this), 126 _is_alive(this, heap->concurrent_mark()->mark_bitmap()), 127 _is_alive_mutator(heap->ref_processor_stw(), &_is_alive), 128 _always_subject_to_discovery(), 129 _is_subject_mutator(heap->ref_processor_stw(), &_always_subject_to_discovery), 130 _region_attr_table() { 131 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 132 133 _preserved_marks_set.init(_num_workers); 134 _markers = NEW_C_HEAP_ARRAY(G1FullGCMarker*, _num_workers, mtGC); 135 _compaction_points = NEW_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _num_workers, mtGC); 136 137 _live_stats = NEW_C_HEAP_ARRAY(G1RegionMarkStats, _heap->max_regions(), mtGC); 138 _compaction_tops = NEW_C_HEAP_ARRAY(HeapWord*, _heap->max_regions(), mtGC); 139 for (uint j = 0; j < heap->max_regions(); j++) { 140 _live_stats[j].clear(); 141 _compaction_tops[j] = nullptr; 142 } 143 144 for (uint i = 0; i < _num_workers; i++) { 145 _markers[i] = new G1FullGCMarker(this, i, _preserved_marks_set.get(i), _live_stats); 146 _compaction_points[i] = new G1FullGCCompactionPoint(this); 147 _oop_queue_set.register_queue(i, marker(i)->oop_stack()); 148 _array_queue_set.register_queue(i, marker(i)->objarray_stack()); 149 } 150 _region_attr_table.initialize(heap->reserved(), HeapRegion::GrainBytes); 151 } 152 153 G1FullCollector::~G1FullCollector() { 154 for (uint i = 0; i < _num_workers; i++) { 155 delete _markers[i]; 156 delete _compaction_points[i]; 157 } 158 FREE_C_HEAP_ARRAY(G1FullGCMarker*, _markers); 159 FREE_C_HEAP_ARRAY(G1FullGCCompactionPoint*, _compaction_points); 160 FREE_C_HEAP_ARRAY(HeapWord*, _compaction_tops); 161 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _live_stats); 162 } 163 164 class PrepareRegionsClosure : public HeapRegionClosure { 165 G1FullCollector* _collector; 166 167 public: 168 PrepareRegionsClosure(G1FullCollector* collector) : _collector(collector) { } 169 170 bool do_heap_region(HeapRegion* hr) { 171 G1CollectedHeap::heap()->prepare_region_for_full_compaction(hr); 172 _collector->before_marking_update_attribute_table(hr); 173 return false; 174 } 175 }; 176 177 void G1FullCollector::prepare_collection() { 178 _heap->policy()->record_full_collection_start(); 179 180 // Verification needs the bitmap, so we should clear the bitmap only later. 181 bool in_concurrent_cycle = _heap->abort_concurrent_cycle(); 182 _heap->verify_before_full_collection(scope()->is_explicit_gc()); 183 if (in_concurrent_cycle) { 184 GCTraceTime(Debug, gc) debug("Clear Bitmap"); 185 _heap->concurrent_mark()->clear_bitmap(_heap->workers()); 186 } 187 188 _heap->gc_prologue(true); 189 _heap->retire_tlabs(); 190 _heap->prepare_heap_for_full_collection(); 191 192 PrepareRegionsClosure cl(this); 193 _heap->heap_region_iterate(&cl); 194 195 reference_processor()->start_discovery(scope()->should_clear_soft_refs()); 196 197 // Clear and activate derived pointer collection. 198 clear_and_activate_derived_pointers(); 199 } 200 201 void G1FullCollector::collect() { 202 G1CollectedHeap::start_codecache_marking_cycle_if_inactive(false /* concurrent_mark_start */); 203 204 phase1_mark_live_objects(); 205 verify_after_marking(); 206 207 // Don't add any more derived pointers during later phases 208 deactivate_derived_pointers(); 209 210 phase2_prepare_compaction(); 211 212 if (has_compaction_targets()) { 213 phase3_adjust_pointers(); 214 215 phase4_do_compaction(); 216 } else { 217 // All regions have a high live ratio thus will not be compacted. 218 // The live ratio is only considered if do_maximal_compaction is false. 219 log_info(gc, phases) ("No Regions selected for compaction. Skipping Phase 3: Adjust pointers and Phase 4: Compact heap"); 220 } 221 222 phase5_reset_metadata(); 223 224 G1CollectedHeap::finish_codecache_marking_cycle(); 225 } 226 227 void G1FullCollector::complete_collection() { 228 // Restore all marks. 229 restore_marks(); 230 231 // When the pointers have been adjusted and moved, we can 232 // update the derived pointer table. 233 update_derived_pointers(); 234 235 // Need completely cleared claim bits for the next concurrent marking or full gc. 236 ClassLoaderDataGraph::clear_claimed_marks(); 237 238 // Prepare the bitmap for the next (potentially concurrent) marking. 239 _heap->concurrent_mark()->clear_bitmap(_heap->workers()); 240 241 _heap->prepare_for_mutator_after_full_collection(); 242 243 _heap->resize_all_tlabs(); 244 245 _heap->policy()->record_full_collection_end(); 246 _heap->gc_epilogue(true); 247 248 _heap->verify_after_full_collection(); 249 } 250 251 void G1FullCollector::before_marking_update_attribute_table(HeapRegion* hr) { 252 if (hr->is_free()) { 253 _region_attr_table.set_free(hr->hrm_index()); 254 } else if (hr->is_closed_archive()) { 255 _region_attr_table.set_skip_marking(hr->hrm_index()); 256 } else if (hr->is_pinned()) { 257 _region_attr_table.set_skip_compacting(hr->hrm_index()); 258 } else { 259 // Everything else should be compacted. 260 _region_attr_table.set_compacting(hr->hrm_index()); 261 } 262 } 263 264 class G1FullGCRefProcProxyTask : public RefProcProxyTask { 265 G1FullCollector& _collector; 266 267 public: 268 G1FullGCRefProcProxyTask(G1FullCollector &collector, uint max_workers) 269 : RefProcProxyTask("G1FullGCRefProcProxyTask", max_workers), 270 _collector(collector) {} 271 272 void work(uint worker_id) override { 273 assert(worker_id < _max_workers, "sanity"); 274 G1IsAliveClosure is_alive(&_collector); 275 uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id; 276 G1FullKeepAliveClosure keep_alive(_collector.marker(index)); 277 BarrierEnqueueDiscoveredFieldClosure enqueue; 278 G1FollowStackClosure* complete_gc = _collector.marker(index)->stack_closure(); 279 _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, complete_gc); 280 } 281 }; 282 283 void G1FullCollector::phase1_mark_live_objects() { 284 // Recursively traverse all live objects and mark them. 285 GCTraceTime(Info, gc, phases) info("Phase 1: Mark live objects", scope()->timer()); 286 287 { 288 // Do the actual marking. 289 G1FullGCMarkTask marking_task(this); 290 run_task(&marking_task); 291 } 292 293 { 294 uint old_active_mt_degree = reference_processor()->num_queues(); 295 reference_processor()->set_active_mt_degree(workers()); 296 GCTraceTime(Debug, gc, phases) debug("Phase 1: Reference Processing", scope()->timer()); 297 // Process reference objects found during marking. 298 ReferenceProcessorPhaseTimes pt(scope()->timer(), reference_processor()->max_num_queues()); 299 G1FullGCRefProcProxyTask task(*this, reference_processor()->max_num_queues()); 300 const ReferenceProcessorStats& stats = reference_processor()->process_discovered_references(task, pt); 301 scope()->tracer()->report_gc_reference_stats(stats); 302 pt.print_all_references(); 303 assert(marker(0)->oop_stack()->is_empty(), "Should be no oops on the stack"); 304 305 reference_processor()->set_active_mt_degree(old_active_mt_degree); 306 } 307 308 // Weak oops cleanup. 309 { 310 GCTraceTime(Debug, gc, phases) debug("Phase 1: Weak Processing", scope()->timer()); 311 WeakProcessor::weak_oops_do(_heap->workers(), &_is_alive, &do_nothing_cl, 1); 312 } 313 314 // Class unloading and cleanup. 315 if (ClassUnloading) { 316 GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer()); 317 CodeCache::UnloadingScope unloading_scope(&_is_alive); 318 // Unload classes and purge the SystemDictionary. 319 bool purged_class = SystemDictionary::do_unloading(scope()->timer()); 320 _heap->complete_cleaning(purged_class); 321 } 322 323 scope()->tracer()->report_object_count_after_gc(&_is_alive); 324 #if TASKQUEUE_STATS 325 oop_queue_set()->print_and_reset_taskqueue_stats("Oop Queue"); 326 array_queue_set()->print_and_reset_taskqueue_stats("ObjArrayOop Queue"); 327 #endif 328 } 329 330 void G1FullCollector::phase2_prepare_compaction() { 331 GCTraceTime(Info, gc, phases) info("Phase 2: Prepare compaction", scope()->timer()); 332 333 phase2a_determine_worklists(); 334 335 if (!has_compaction_targets()) { 336 return; 337 } 338 339 bool has_free_compaction_targets = phase2b_forward_oops(); 340 341 // Try to avoid OOM immediately after Full GC in case there are no free regions 342 // left after determining the result locations (i.e. this phase). Prepare to 343 // maximally compact the tail regions of the compaction queues serially. 344 if (scope()->do_maximal_compaction() || !has_free_compaction_targets) { 345 phase2c_prepare_serial_compaction(); 346 } 347 } 348 349 void G1FullCollector::phase2a_determine_worklists() { 350 GCTraceTime(Debug, gc, phases) debug("Phase 2: Determine work lists", scope()->timer()); 351 352 G1DetermineCompactionQueueClosure cl(this); 353 _heap->heap_region_iterate(&cl); 354 } 355 356 bool G1FullCollector::phase2b_forward_oops() { 357 GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare parallel compaction", scope()->timer()); 358 359 G1FullGCPrepareTask task(this); 360 run_task(&task); 361 362 return task.has_free_compaction_targets(); 363 } 364 365 uint G1FullCollector::truncate_parallel_cps() { 366 uint lowest_current = (uint)-1; 367 for (uint i = 0; i < workers(); i++) { 368 G1FullGCCompactionPoint* cp = compaction_point(i); 369 if (cp->has_regions()) { 370 lowest_current = MIN2(lowest_current, cp->current_region()->hrm_index()); 371 } 372 } 373 374 for (uint i = 0; i < workers(); i++) { 375 G1FullGCCompactionPoint* cp = compaction_point(i); 376 if (cp->has_regions()) { 377 cp->remove_at_or_above(lowest_current); 378 } 379 } 380 return lowest_current; 381 } 382 383 void G1FullCollector::phase2c_prepare_serial_compaction() { 384 GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare serial compaction", scope()->timer()); 385 // At this point, we know that after parallel compaction there will be regions that 386 // are partially compacted into. Thus, the last compaction region of all 387 // compaction queues still have space in them. We try to re-compact these regions 388 // in serial to avoid a premature OOM when the mutator wants to allocate the first 389 // eden region after gc. 390 391 // For maximum compaction, we need to re-prepare all objects above the lowest 392 // region among the current regions for all thread compaction points. It may 393 // happen that due to the uneven distribution of objects to parallel threads, holes 394 // have been created as threads compact to different target regions between the 395 // lowest and the highest region in the tails of the compaction points. 396 397 uint start_serial = truncate_parallel_cps(); 398 assert(start_serial < _heap->max_reserved_regions(), "Called on empty parallel compaction queues"); 399 400 G1FullGCCompactionPoint* serial_cp = serial_compaction_point(); 401 assert(!serial_cp->is_initialized(), "sanity!"); 402 403 HeapRegion* start_hr = _heap->region_at(start_serial); 404 serial_cp->add(start_hr); 405 serial_cp->initialize(start_hr); 406 407 HeapWord* dense_prefix_top = compaction_top(start_hr); 408 G1SerialRePrepareClosure re_prepare(serial_cp, dense_prefix_top); 409 410 for (uint i = start_serial + 1; i < _heap->max_reserved_regions(); i++) { 411 if (is_compaction_target(i)) { 412 HeapRegion* current = _heap->region_at(i); 413 set_compaction_top(current, current->bottom()); 414 serial_cp->add(current); 415 current->apply_to_marked_objects(mark_bitmap(), &re_prepare); 416 } 417 } 418 serial_cp->update(); 419 } 420 421 void G1FullCollector::phase3_adjust_pointers() { 422 // Adjust the pointers to reflect the new locations 423 GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer()); 424 425 G1FullGCAdjustTask task(this); 426 run_task(&task); 427 } 428 429 void G1FullCollector::phase4_do_compaction() { 430 // Compact the heap using the compaction queues created in phase 2. 431 GCTraceTime(Info, gc, phases) info("Phase 4: Compact heap", scope()->timer()); 432 G1FullGCCompactTask task(this); 433 run_task(&task); 434 435 // Serial compact to avoid OOM when very few free regions. 436 if (serial_compaction_point()->has_regions()) { 437 task.serial_compaction(); 438 } 439 } 440 441 void G1FullCollector::phase5_reset_metadata() { 442 // Clear region metadata that is invalid after GC for all regions. 443 GCTraceTime(Info, gc, phases) info("Phase 5: Reset Metadata", scope()->timer()); 444 G1FullGCResetMetadataTask task(this); 445 run_task(&task); 446 } 447 448 void G1FullCollector::restore_marks() { 449 _preserved_marks_set.restore(_heap->workers()); 450 _preserved_marks_set.reclaim(); 451 } 452 453 void G1FullCollector::run_task(WorkerTask* task) { 454 _heap->workers()->run_task(task, _num_workers); 455 } 456 457 void G1FullCollector::verify_after_marking() { 458 if (!VerifyDuringGC || !_heap->verifier()->should_verify(G1HeapVerifier::G1VerifyFull)) { 459 // Only do verification if VerifyDuringGC and G1VerifyFull is set. 460 return; 461 } 462 463 #if COMPILER2_OR_JVMCI 464 DerivedPointerTableDeactivate dpt_deact; 465 #endif 466 _heap->prepare_for_verify(); 467 // Note: we can verify only the heap here. When an object is 468 // marked, the previous value of the mark word (including 469 // identity hash values, ages, etc) is preserved, and the mark 470 // word is set to markWord::marked_value - effectively removing 471 // any hash values from the mark word. These hash values are 472 // used when verifying the dictionaries and so removing them 473 // from the mark word can make verification of the dictionaries 474 // fail. At the end of the GC, the original mark word values 475 // (including hash values) are restored to the appropriate 476 // objects. 477 GCTraceTime(Info, gc, verify) tm("Verifying During GC (full)"); 478 _heap->verify(VerifyOption::G1UseFullMarking); 479 }