1 /* 2 * Copyright (c) 2001, 2015, 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/javaClasses.hpp" 27 #include "classfile/stringTable.hpp" 28 #include "classfile/systemDictionary.hpp" 29 #include "classfile/vmSymbols.hpp" 30 #include "code/codeCache.hpp" 31 #include "code/icBuffer.hpp" 32 #include "gc_implementation/shared/gcHeapSummary.hpp" 33 #include "gc_implementation/shared/gcTimer.hpp" 34 #include "gc_implementation/shared/gcTrace.hpp" 35 #include "gc_implementation/shared/gcTraceTime.hpp" 36 #include "gc_interface/collectedHeap.inline.hpp" 37 #include "memory/genCollectedHeap.hpp" 38 #include "memory/genMarkSweep.hpp" 39 #include "memory/genOopClosures.inline.hpp" 40 #include "memory/generation.hpp" 41 #include "memory/modRefBarrierSet.hpp" 42 #include "memory/referencePolicy.hpp" 43 #include "memory/space.hpp" 44 #include "oops/instanceRefKlass.hpp" 45 #include "oops/oop.inline.hpp" 46 #include "prims/jvmtiExport.hpp" 47 #include "runtime/fprofiler.hpp" 48 #include "runtime/handles.inline.hpp" 49 #include "runtime/synchronizer.hpp" 50 #include "runtime/thread.inline.hpp" 51 #include "runtime/vmThread.hpp" 52 #include "utilities/copy.hpp" 53 #include "utilities/events.hpp" 54 #include "utilities/stack.inline.hpp" 55 56 void GenMarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, bool clear_all_softrefs) { 57 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 58 59 GenCollectedHeap* gch = GenCollectedHeap::heap(); 60 #ifdef ASSERT 61 if (gch->collector_policy()->should_clear_all_soft_refs()) { 62 assert(clear_all_softrefs, "Policy should have been checked earlier"); 63 } 64 #endif 65 66 // hook up weak ref data so it can be used during Mark-Sweep 67 assert(ref_processor() == NULL, "no stomping"); 68 assert(rp != NULL, "should be non-NULL"); 69 _ref_processor = rp; 70 rp->setup_policy(clear_all_softrefs); 71 72 GCTraceTime t1(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, _gc_tracer->gc_id()); 73 74 gch->trace_heap_before_gc(_gc_tracer); 75 76 // When collecting the permanent generation Method*s may be moving, 77 // so we either have to flush all bcp data or convert it into bci. 78 CodeCache::gc_prologue(); 79 80 // Increment the invocation count 81 _total_invocations++; 82 83 // Capture heap size before collection for printing. 84 size_t gch_prev_used = gch->used(); 85 86 // Capture used regions for each generation that will be 87 // subject to collection, so that card table adjustments can 88 // be made intelligently (see clear / invalidate further below). 89 gch->save_used_regions(); 90 91 allocate_stacks(); 92 93 mark_sweep_phase1(clear_all_softrefs); 94 95 mark_sweep_phase2(); 96 97 // Don't add any more derived pointers during phase3 98 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); 99 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 100 101 mark_sweep_phase3(); 102 103 mark_sweep_phase4(); 104 105 restore_marks(); 106 107 // Set saved marks for allocation profiler (and other things? -- dld) 108 // (Should this be in general part?) 109 gch->save_marks(); 110 111 deallocate_stacks(); 112 113 // If compaction completely evacuated the young generation then we 114 // can clear the card table. Otherwise, we must invalidate 115 // it (consider all cards dirty). In the future, we might consider doing 116 // compaction within generations only, and doing card-table sliding. 117 GenRemSet* rs = gch->rem_set(); 118 Generation* old_gen = gch->old_gen(); 119 120 // Clear/invalidate below make use of the "prev_used_regions" saved earlier. 121 if (gch->young_gen()->used() == 0) { 122 // We've evacuated the young generation. 123 rs->clear_into_younger(old_gen); 124 } else { 125 // Invalidate the cards corresponding to the currently used 126 // region and clear those corresponding to the evacuated region. 127 rs->invalidate_or_clear(old_gen); 128 } 129 130 CodeCache::gc_epilogue(); 131 JvmtiExport::gc_epilogue(); 132 133 if (PrintGC && !PrintGCDetails) { 134 gch->print_heap_change(gch_prev_used); 135 } 136 137 // refs processing: clean slate 138 _ref_processor = NULL; 139 140 // Update heap occupancy information which is used as 141 // input to soft ref clearing policy at the next gc. 142 Universe::update_heap_info_at_gc(); 143 144 // Update time of last gc for all generations we collected 145 // (which currently is all the generations in the heap). 146 // We need to use a monotonically non-decreasing time in ms 147 // or we will see time-warp warnings and os::javaTimeMillis() 148 // does not guarantee monotonicity. 149 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 150 gch->update_time_of_last_gc(now); 151 152 gch->trace_heap_after_gc(_gc_tracer); 153 } 154 155 void GenMarkSweep::allocate_stacks() { 156 GenCollectedHeap* gch = GenCollectedHeap::heap(); 157 // Scratch request on behalf of old generation; will do no allocation. 158 ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0); 159 160 // $$$ To cut a corner, we'll only use the first scratch block, and then 161 // revert to malloc. 162 if (scratch != NULL) { 163 _preserved_count_max = 164 scratch->num_words * HeapWordSize / sizeof(PreservedMark); 165 } else { 166 _preserved_count_max = 0; 167 } 168 169 _preserved_marks = (PreservedMark*)scratch; 170 _preserved_count = 0; 171 } 172 173 174 void GenMarkSweep::deallocate_stacks() { 175 if (!UseG1GC) { 176 GenCollectedHeap* gch = GenCollectedHeap::heap(); 177 gch->release_scratch(); 178 } 179 180 _preserved_mark_stack.clear(true); 181 _preserved_oop_stack.clear(true); 182 _marking_stack.clear(); 183 _objarray_stack.clear(true); 184 } 185 186 void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) { 187 // Recursively traverse all live objects and mark them 188 GCTraceTime tm("phase 1", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 189 190 GenCollectedHeap* gch = GenCollectedHeap::heap(); 191 192 // Because follow_root_closure is created statically, cannot 193 // use OopsInGenClosure constructor which takes a generation, 194 // as the Universe has not been created when the static constructors 195 // are run. 196 follow_root_closure.set_orig_generation(gch->old_gen()); 197 198 // Need new claim bits before marking starts. 199 ClassLoaderDataGraph::clear_claimed_marks(); 200 201 gch->gen_process_roots(Generation::Old, 202 false, // Younger gens are not roots. 203 true, // activate StrongRootsScope 204 GenCollectedHeap::SO_None, 205 GenCollectedHeap::StrongRootsOnly, 206 &follow_root_closure, 207 &follow_root_closure, 208 &follow_cld_closure); 209 210 // Process reference objects found during marking 211 { 212 ref_processor()->setup_policy(clear_all_softrefs); 213 const ReferenceProcessorStats& stats = 214 ref_processor()->process_discovered_references( 215 &is_alive, &keep_alive, &follow_stack_closure, NULL, _gc_timer, _gc_tracer->gc_id()); 216 gc_tracer()->report_gc_reference_stats(stats); 217 } 218 219 // This is the point where the entire marking should have completed. 220 assert(_marking_stack.is_empty(), "Marking should have completed"); 221 222 // Unload classes and purge the SystemDictionary. 223 bool purged_class = SystemDictionary::do_unloading(&is_alive); 224 225 // Unload nmethods. 226 CodeCache::do_unloading(&is_alive, purged_class); 227 228 // Prune dead klasses from subklass/sibling/implementor lists. 229 Klass::clean_weak_klass_links(&is_alive); 230 231 // Delete entries for dead interned strings. 232 StringTable::unlink(&is_alive); 233 234 // Clean up unreferenced symbols in symbol table. 235 SymbolTable::unlink(); 236 237 gc_tracer()->report_object_count_after_gc(&is_alive); 238 } 239 240 241 void GenMarkSweep::mark_sweep_phase2() { 242 // Now all live objects are marked, compute the new object addresses. 243 244 // It is imperative that we traverse perm_gen LAST. If dead space is 245 // allowed a range of dead object may get overwritten by a dead int 246 // array. If perm_gen is not traversed last a Klass* may get 247 // overwritten. This is fine since it is dead, but if the class has dead 248 // instances we have to skip them, and in order to find their size we 249 // need the Klass*! 250 // 251 // It is not required that we traverse spaces in the same order in 252 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 253 // tracking expects us to do so. See comment under phase4. 254 255 GenCollectedHeap* gch = GenCollectedHeap::heap(); 256 257 GCTraceTime tm("phase 2", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 258 259 gch->prepare_for_compaction(); 260 } 261 262 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure { 263 public: 264 void do_generation(Generation* gen) { 265 gen->adjust_pointers(); 266 } 267 }; 268 269 void GenMarkSweep::mark_sweep_phase3() { 270 GenCollectedHeap* gch = GenCollectedHeap::heap(); 271 272 // Adjust the pointers to reflect the new locations 273 GCTraceTime tm("phase 3", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 274 275 // Need new claim bits for the pointer adjustment tracing. 276 ClassLoaderDataGraph::clear_claimed_marks(); 277 278 // Because the closure below is created statically, we cannot 279 // use OopsInGenClosure constructor which takes a generation, 280 // as the Universe has not been created when the static constructors 281 // are run. 282 adjust_pointer_closure.set_orig_generation(gch->old_gen()); 283 284 gch->gen_process_roots(Generation::Old, 285 false, // Younger gens are not roots. 286 true, // activate StrongRootsScope 287 GenCollectedHeap::SO_AllCodeCache, 288 GenCollectedHeap::StrongAndWeakRoots, 289 &adjust_pointer_closure, 290 &adjust_pointer_closure, 291 &adjust_cld_closure); 292 293 gch->gen_process_weak_roots(&adjust_pointer_closure); 294 295 adjust_marks(); 296 GenAdjustPointersClosure blk; 297 gch->generation_iterate(&blk, true); 298 } 299 300 class GenCompactClosure: public GenCollectedHeap::GenClosure { 301 public: 302 void do_generation(Generation* gen) { 303 gen->compact(); 304 } 305 }; 306 307 void GenMarkSweep::mark_sweep_phase4() { 308 // All pointers are now adjusted, move objects accordingly 309 310 // It is imperative that we traverse perm_gen first in phase4. All 311 // classes must be allocated earlier than their instances, and traversing 312 // perm_gen first makes sure that all Klass*s have moved to their new 313 // location before any instance does a dispatch through it's klass! 314 315 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 316 // in the same order in phase2, phase3 and phase4. We don't quite do that 317 // here (perm_gen first rather than last), so we tell the validate code 318 // to use a higher index (saved from phase2) when verifying perm_gen. 319 GenCollectedHeap* gch = GenCollectedHeap::heap(); 320 321 GCTraceTime tm("phase 4", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 322 323 GenCompactClosure blk; 324 gch->generation_iterate(&blk, true); 325 }