1 /* 2 * Copyright (c) 2001, 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 "classfile/classLoaderDataGraph.hpp" 27 #include "classfile/javaClasses.hpp" 28 #include "classfile/stringTable.hpp" 29 #include "classfile/symbolTable.hpp" 30 #include "classfile/systemDictionary.hpp" 31 #include "classfile/vmSymbols.hpp" 32 #include "code/codeCache.hpp" 33 #include "code/icBuffer.hpp" 34 #include "gc/serial/genMarkSweep.hpp" 35 #include "gc/shared/collectedHeap.inline.hpp" 36 #include "gc/shared/gcHeapSummary.hpp" 37 #include "gc/shared/gcTimer.hpp" 38 #include "gc/shared/gcTrace.hpp" 39 #include "gc/shared/gcTraceTime.inline.hpp" 40 #include "gc/shared/genCollectedHeap.hpp" 41 #include "gc/shared/generation.hpp" 42 #include "gc/shared/genOopClosures.inline.hpp" 43 #include "gc/shared/modRefBarrierSet.hpp" 44 #include "gc/shared/referencePolicy.hpp" 45 #include "gc/shared/referenceProcessorPhaseTimes.hpp" 46 #include "gc/shared/space.hpp" 47 #include "gc/shared/strongRootsScope.hpp" 48 #include "gc/shared/weakProcessor.hpp" 49 #include "memory/universe.hpp" 50 #include "oops/instanceRefKlass.hpp" 51 #include "oops/oop.inline.hpp" 52 #include "prims/jvmtiExport.hpp" 53 #include "runtime/handles.inline.hpp" 54 #include "runtime/synchronizer.hpp" 55 #include "runtime/thread.inline.hpp" 56 #include "runtime/vmThread.hpp" 57 #include "utilities/copy.hpp" 58 #include "utilities/events.hpp" 59 #include "utilities/stack.inline.hpp" 60 #if INCLUDE_JVMCI 61 #include "jvmci/jvmci.hpp" 62 #endif 63 64 void GenMarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, bool clear_all_softrefs) { 65 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 66 67 GenCollectedHeap* gch = GenCollectedHeap::heap(); 68 #ifdef ASSERT 69 if (gch->soft_ref_policy()->should_clear_all_soft_refs()) { 70 assert(clear_all_softrefs, "Policy should have been checked earlier"); 71 } 72 #endif 73 74 // hook up weak ref data so it can be used during Mark-Sweep 75 assert(ref_processor() == NULL, "no stomping"); 76 assert(rp != NULL, "should be non-NULL"); 77 set_ref_processor(rp); 78 rp->setup_policy(clear_all_softrefs); 79 80 gch->trace_heap_before_gc(_gc_tracer); 81 82 // Increment the invocation count 83 _total_invocations++; 84 85 // Capture used regions for each generation that will be 86 // subject to collection, so that card table adjustments can 87 // be made intelligently (see clear / invalidate further below). 88 gch->save_used_regions(); 89 90 allocate_stacks(); 91 92 mark_sweep_phase1(clear_all_softrefs); 93 94 mark_sweep_phase2(); 95 96 // Don't add any more derived pointers during phase3 97 #if COMPILER2_OR_JVMCI 98 assert(DerivedPointerTable::is_active(), "Sanity"); 99 DerivedPointerTable::set_active(false); 100 #endif 101 102 mark_sweep_phase3(); 103 104 mark_sweep_phase4(); 105 106 restore_marks(); 107 108 // Set saved marks for allocation profiler (and other things? -- dld) 109 // (Should this be in general part?) 110 gch->save_marks(); 111 112 deallocate_stacks(); 113 114 // If compaction completely evacuated the young generation then we 115 // can clear the card table. Otherwise, we must invalidate 116 // it (consider all cards dirty). In the future, we might consider doing 117 // compaction within generations only, and doing card-table sliding. 118 CardTableRS* rs = gch->rem_set(); 119 Generation* old_gen = gch->old_gen(); 120 121 // Clear/invalidate below make use of the "prev_used_regions" saved earlier. 122 if (gch->young_gen()->used() == 0) { 123 // We've evacuated the young generation. 124 rs->clear_into_younger(old_gen); 125 } else { 126 // Invalidate the cards corresponding to the currently used 127 // region and clear those corresponding to the evacuated region. 128 rs->invalidate_or_clear(old_gen); 129 } 130 131 gch->prune_scavengable_nmethods(); 132 133 // refs processing: clean slate 134 set_ref_processor(NULL); 135 136 // Update heap occupancy information which is used as 137 // input to soft ref clearing policy at the next gc. 138 Universe::update_heap_info_at_gc(); 139 140 Universe::heap()->next_whole_heap_examined(); 141 142 gch->trace_heap_after_gc(_gc_tracer); 143 } 144 145 void GenMarkSweep::allocate_stacks() { 146 GenCollectedHeap* gch = GenCollectedHeap::heap(); 147 // Scratch request on behalf of old generation; will do no allocation. 148 ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0); 149 150 // $$$ To cut a corner, we'll only use the first scratch block, and then 151 // revert to malloc. 152 if (scratch != NULL) { 153 _preserved_count_max = 154 scratch->num_words * HeapWordSize / sizeof(PreservedMark); 155 } else { 156 _preserved_count_max = 0; 157 } 158 159 _preserved_marks = (PreservedMark*)scratch; 160 _preserved_count = 0; 161 } 162 163 164 void GenMarkSweep::deallocate_stacks() { 165 GenCollectedHeap* gch = GenCollectedHeap::heap(); 166 gch->release_scratch(); 167 168 _preserved_mark_stack.clear(true); 169 _preserved_oop_stack.clear(true); 170 _marking_stack.clear(); 171 _objarray_stack.clear(true); 172 } 173 174 void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) { 175 // Recursively traverse all live objects and mark them 176 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer); 177 178 GenCollectedHeap* gch = GenCollectedHeap::heap(); 179 180 // Because follow_root_closure is created statically, cannot 181 // use OopsInGenClosure constructor which takes a generation, 182 // as the Universe has not been created when the static constructors 183 // are run. 184 follow_root_closure.set_orig_generation(gch->old_gen()); 185 186 // Need new claim bits before marking starts. 187 ClassLoaderDataGraph::clear_claimed_marks(); 188 189 { 190 StrongRootsScope srs(1); 191 192 gch->full_process_roots(&srs, 193 false, // not the adjust phase 194 GenCollectedHeap::SO_None, 195 ClassUnloading, // only strong roots if ClassUnloading 196 // is enabled 197 &follow_root_closure, 198 &follow_cld_closure); 199 } 200 201 // Process reference objects found during marking 202 { 203 GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer()); 204 205 ref_processor()->setup_policy(clear_all_softrefs); 206 ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues()); 207 const ReferenceProcessorStats& stats = 208 ref_processor()->process_discovered_references( 209 &is_alive, &keep_alive, &follow_stack_closure, NULL, &pt); 210 pt.print_all_references(); 211 gc_tracer()->report_gc_reference_stats(stats); 212 } 213 214 // This is the point where the entire marking should have completed. 215 assert(_marking_stack.is_empty(), "Marking should have completed"); 216 217 { 218 GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer()); 219 WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl); 220 } 221 222 { 223 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer()); 224 225 // Unload classes and purge the SystemDictionary. 226 bool purged_class = SystemDictionary::do_unloading(gc_timer()); 227 228 // Unload nmethods. 229 CodeCache::do_unloading(&is_alive, purged_class); 230 231 // Prune dead klasses from subklass/sibling/implementor lists. 232 Klass::clean_weak_klass_links(purged_class); 233 234 // Clean JVMCI metadata handles. 235 JVMCI_ONLY(JVMCI::do_unloading(purged_class)); 236 } 237 238 gc_tracer()->report_object_count_after_gc(&is_alive); 239 } 240 241 242 void GenMarkSweep::mark_sweep_phase2() { 243 // Now all live objects are marked, compute the new object addresses. 244 245 // It is imperative that we traverse perm_gen LAST. If dead space is 246 // allowed a range of dead object may get overwritten by a dead int 247 // array. If perm_gen is not traversed last a Klass* may get 248 // overwritten. This is fine since it is dead, but if the class has dead 249 // instances we have to skip them, and in order to find their size we 250 // need the Klass*! 251 // 252 // It is not required that we traverse spaces in the same order in 253 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 254 // tracking expects us to do so. See comment under phase4. 255 256 GenCollectedHeap* gch = GenCollectedHeap::heap(); 257 258 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer); 259 260 gch->prepare_for_compaction(); 261 } 262 263 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure { 264 public: 265 void do_generation(Generation* gen) { 266 gen->adjust_pointers(); 267 } 268 }; 269 270 void GenMarkSweep::mark_sweep_phase3() { 271 GenCollectedHeap* gch = GenCollectedHeap::heap(); 272 273 // Adjust the pointers to reflect the new locations 274 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer()); 275 276 // Need new claim bits for the pointer adjustment tracing. 277 ClassLoaderDataGraph::clear_claimed_marks(); 278 279 // Because the closure below is created statically, we cannot 280 // use OopsInGenClosure constructor which takes a generation, 281 // as the Universe has not been created when the static constructors 282 // are run. 283 adjust_pointer_closure.set_orig_generation(gch->old_gen()); 284 285 { 286 StrongRootsScope srs(1); 287 288 gch->full_process_roots(&srs, 289 true, // this is the adjust phase 290 GenCollectedHeap::SO_AllCodeCache, 291 false, // all roots 292 &adjust_pointer_closure, 293 &adjust_cld_closure); 294 } 295 296 gch->gen_process_weak_roots(&adjust_pointer_closure); 297 298 adjust_marks(); 299 GenAdjustPointersClosure blk; 300 gch->generation_iterate(&blk, true); 301 } 302 303 class GenCompactClosure: public GenCollectedHeap::GenClosure { 304 public: 305 void do_generation(Generation* gen) { 306 gen->compact(); 307 } 308 }; 309 310 void GenMarkSweep::mark_sweep_phase4() { 311 // All pointers are now adjusted, move objects accordingly 312 313 // It is imperative that we traverse perm_gen first in phase4. All 314 // classes must be allocated earlier than their instances, and traversing 315 // perm_gen first makes sure that all Klass*s have moved to their new 316 // location before any instance does a dispatch through it's klass! 317 318 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 319 // in the same order in phase2, phase3 and phase4. We don't quite do that 320 // here (perm_gen first rather than last), so we tell the validate code 321 // to use a higher index (saved from phase2) when verifying perm_gen. 322 GenCollectedHeap* gch = GenCollectedHeap::heap(); 323 324 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer); 325 326 GenCompactClosure blk; 327 gch->generation_iterate(&blk, true); 328 }