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/symbolTable.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/g1/g1Log.hpp" 33 #include "gc_implementation/g1/g1MarkSweep.hpp" 34 #include "gc_implementation/g1/g1RootProcessor.hpp" 35 #include "gc_implementation/g1/g1StringDedup.hpp" 36 #include "gc_implementation/shared/markSweep.inline.hpp" 37 #include "gc_implementation/shared/gcHeapSummary.hpp" 38 #include "gc_implementation/shared/gcTimer.hpp" 39 #include "gc_implementation/shared/gcTrace.hpp" 40 #include "gc_implementation/shared/gcTraceTime.hpp" 41 #include "memory/gcLocker.hpp" 42 #include "memory/genCollectedHeap.hpp" 43 #include "memory/modRefBarrierSet.hpp" 44 #include "memory/referencePolicy.hpp" 45 #include "memory/space.hpp" 46 #include "oops/instanceRefKlass.hpp" 47 #include "oops/oop.inline.hpp" 48 #include "prims/jvmtiExport.hpp" 49 #include "runtime/atomic.inline.hpp" 50 #include "runtime/biasedLocking.hpp" 51 #include "runtime/fprofiler.hpp" 52 #include "runtime/synchronizer.hpp" 53 #include "runtime/thread.hpp" 54 #include "runtime/vmThread.hpp" 55 #include "utilities/copy.hpp" 56 #include "utilities/events.hpp" 57 58 class HeapRegion; 59 60 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 61 bool clear_all_softrefs) { 62 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 63 64 #ifdef ASSERT 65 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) { 66 assert(clear_all_softrefs, "Policy should have been checked earler"); 67 } 68 #endif 69 // hook up weak ref data so it can be used during Mark-Sweep 70 assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); 71 assert(rp != NULL, "should be non-NULL"); 72 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition"); 73 74 GenMarkSweep::_ref_processor = rp; 75 rp->setup_policy(clear_all_softrefs); 76 77 // When collecting the permanent generation Method*s may be moving, 78 // so we either have to flush all bcp data or convert it into bci. 79 CodeCache::gc_prologue(); 80 81 bool marked_for_unloading = false; 82 83 allocate_stacks(); 84 85 // We should save the marks of the currently locked biased monitors. 86 // The marking doesn't preserve the marks of biased objects. 87 BiasedLocking::preserve_marks(); 88 89 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); 90 91 mark_sweep_phase2(); 92 93 // Don't add any more derived pointers during phase3 94 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 95 96 mark_sweep_phase3(); 97 98 mark_sweep_phase4(); 99 100 GenMarkSweep::restore_marks(); 101 BiasedLocking::restore_marks(); 102 GenMarkSweep::deallocate_stacks(); 103 104 CodeCache::gc_epilogue(); 105 JvmtiExport::gc_epilogue(); 106 107 // refs processing: clean slate 108 GenMarkSweep::_ref_processor = NULL; 109 } 110 111 112 void G1MarkSweep::allocate_stacks() { 113 GenMarkSweep::_preserved_count_max = 0; 114 GenMarkSweep::_preserved_marks = NULL; 115 GenMarkSweep::_preserved_count = 0; 116 } 117 118 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, 119 bool clear_all_softrefs) { 120 // Recursively traverse all live objects and mark them 121 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 122 GenMarkSweep::trace(" 1"); 123 124 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 125 126 // Need cleared claim bits for the roots processing 127 ClassLoaderDataGraph::clear_claimed_marks(); 128 129 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations); 130 { 131 G1RootProcessor root_processor(g1h); 132 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, 133 &GenMarkSweep::follow_cld_closure, 134 &follow_code_closure); 135 } 136 137 // Process reference objects found during marking 138 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 139 assert(rp == g1h->ref_processor_stw(), "Sanity"); 140 141 rp->setup_policy(clear_all_softrefs); 142 const ReferenceProcessorStats& stats = 143 rp->process_discovered_references(&GenMarkSweep::is_alive, 144 &GenMarkSweep::keep_alive, 145 &GenMarkSweep::follow_stack_closure, 146 NULL, 147 gc_timer(), 148 gc_tracer()->gc_id()); 149 gc_tracer()->report_gc_reference_stats(stats); 150 151 152 // This is the point where the entire marking should have completed. 153 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); 154 155 // Unload classes and purge the SystemDictionary. 156 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 157 158 // Unload nmethods. 159 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); 160 161 // Prune dead klasses from subklass/sibling/implementor lists. 162 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); 163 164 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table. 165 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); 166 167 if (VerifyDuringGC) { 168 HandleMark hm; // handle scope 169 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); 170 g1h->prepare_for_verify(); 171 // Note: we can verify only the heap here. When an object is 172 // marked, the previous value of the mark word (including 173 // identity hash values, ages, etc) is preserved, and the mark 174 // word is set to markOop::marked_value - effectively removing 175 // any hash values from the mark word. These hash values are 176 // used when verifying the dictionaries and so removing them 177 // from the mark word can make verification of the dictionaries 178 // fail. At the end of the GC, the original mark word values 179 // (including hash values) are restored to the appropriate 180 // objects. 181 if (!VerifySilently) { 182 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying "); 183 } 184 g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord); 185 if (!VerifySilently) { 186 gclog_or_tty->print_cr("]"); 187 } 188 } 189 190 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); 191 } 192 193 194 void G1MarkSweep::mark_sweep_phase2() { 195 // Now all live objects are marked, compute the new object addresses. 196 197 // It is not required that we traverse spaces in the same order in 198 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 199 // tracking expects us to do so. See comment under phase4. 200 201 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 202 GenMarkSweep::trace("2"); 203 204 prepare_compaction(); 205 } 206 207 class G1AdjustPointersClosure: public HeapRegionClosure { 208 public: 209 bool doHeapRegion(HeapRegion* r) { 210 if (r->is_humongous()) { 211 if (r->is_starts_humongous()) { 212 // We must adjust the pointers on the single H object. 213 oop obj = oop(r->bottom()); 214 // point all the oops to the new location 215 MarkSweep::adjust_pointers(obj); 216 } 217 } else { 218 // This really ought to be "as_CompactibleSpace"... 219 r->adjust_pointers(); 220 } 221 return false; 222 } 223 }; 224 225 class G1AlwaysTrueClosure: public BoolObjectClosure { 226 public: 227 bool do_object_b(oop p) { return true; } 228 }; 229 static G1AlwaysTrueClosure always_true; 230 231 void G1MarkSweep::mark_sweep_phase3() { 232 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 233 234 // Adjust the pointers to reflect the new locations 235 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 236 GenMarkSweep::trace("3"); 237 238 // Need cleared claim bits for the roots processing 239 ClassLoaderDataGraph::clear_claimed_marks(); 240 241 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations); 242 { 243 G1RootProcessor root_processor(g1h); 244 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure, 245 &GenMarkSweep::adjust_cld_closure, 246 &adjust_code_closure); 247 } 248 249 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 250 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 251 252 // Now adjust pointers in remaining weak roots. (All of which should 253 // have been cleared if they pointed to non-surviving objects.) 254 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure); 255 256 if (G1StringDedup::is_enabled()) { 257 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure); 258 } 259 260 GenMarkSweep::adjust_marks(); 261 262 G1AdjustPointersClosure blk; 263 g1h->heap_region_iterate(&blk); 264 } 265 266 class G1SpaceCompactClosure: public HeapRegionClosure { 267 public: 268 G1SpaceCompactClosure() {} 269 270 bool doHeapRegion(HeapRegion* hr) { 271 if (hr->is_humongous()) { 272 if (hr->is_starts_humongous()) { 273 oop obj = oop(hr->bottom()); 274 if (obj->is_gc_marked()) { 275 obj->init_mark(); 276 } else { 277 assert(hr->is_empty(), "Should have been cleared in phase 2."); 278 } 279 hr->reset_during_compaction(); 280 } 281 } else { 282 hr->compact(); 283 } 284 return false; 285 } 286 }; 287 288 void G1MarkSweep::mark_sweep_phase4() { 289 // All pointers are now adjusted, move objects accordingly 290 291 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 292 // in the same order in phase2, phase3 and phase4. We don't quite do that 293 // here (code and comment not fixed for perm removal), so we tell the validate code 294 // to use a higher index (saved from phase2) when verifying perm_gen. 295 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 296 297 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 298 GenMarkSweep::trace("4"); 299 300 G1SpaceCompactClosure blk; 301 g1h->heap_region_iterate(&blk); 302 303 } 304 305 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) { 306 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 307 g1h->heap_region_iterate(blk); 308 blk->update_sets(); 309 } 310 311 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) { 312 HeapWord* end = hr->end(); 313 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 314 315 assert(hr->is_starts_humongous(), 316 "Only the start of a humongous region should be freed."); 317 318 hr->set_containing_set(NULL); 319 _humongous_regions_removed.increment(1u, hr->capacity()); 320 321 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */); 322 prepare_for_compaction(hr, end); 323 dummy_free_list.remove_all(); 324 } 325 326 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) { 327 // If this is the first live region that we came across which we can compact, 328 // initialize the CompactPoint. 329 if (!is_cp_initialized()) { 330 _cp.space = hr; 331 _cp.threshold = hr->initialize_threshold(); 332 } 333 prepare_for_compaction_work(&_cp, hr, end); 334 } 335 336 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp, 337 HeapRegion* hr, 338 HeapWord* end) { 339 hr->prepare_for_compaction(cp); 340 // Also clear the part of the card table that will be unused after 341 // compaction. 342 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 343 } 344 345 void G1PrepareCompactClosure::update_sets() { 346 // We'll recalculate total used bytes and recreate the free list 347 // at the end of the GC, so no point in updating those values here. 348 HeapRegionSetCount empty_set; 349 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed); 350 } 351 352 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) { 353 if (hr->is_humongous()) { 354 if (hr->is_starts_humongous()) { 355 oop obj = oop(hr->bottom()); 356 if (obj->is_gc_marked()) { 357 obj->forward_to(obj); 358 } else { 359 free_humongous_region(hr); 360 } 361 } else { 362 assert(hr->is_continues_humongous(), "Invalid humongous."); 363 } 364 } else { 365 prepare_for_compaction(hr, hr->end()); 366 } 367 return false; 368 }