1 /* 2 * Copyright (c) 2001, 2013, 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/shared/gcHeapSummary.hpp" 35 #include "gc_implementation/shared/gcTimer.hpp" 36 #include "gc_implementation/shared/gcTrace.hpp" 37 #include "gc_implementation/shared/gcTraceTime.hpp" 38 #include "memory/gcLocker.hpp" 39 #include "memory/genCollectedHeap.hpp" 40 #include "memory/modRefBarrierSet.hpp" 41 #include "memory/referencePolicy.hpp" 42 #include "memory/space.hpp" 43 #include "oops/instanceRefKlass.hpp" 44 #include "oops/oop.inline.hpp" 45 #include "prims/jvmtiExport.hpp" 46 #include "runtime/biasedLocking.hpp" 47 #include "runtime/fprofiler.hpp" 48 #include "runtime/synchronizer.hpp" 49 #include "runtime/thread.hpp" 50 #include "runtime/vmThread.hpp" 51 #include "utilities/copy.hpp" 52 #include "utilities/events.hpp" 53 54 class HeapRegion; 55 56 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 57 bool clear_all_softrefs) { 58 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 59 60 SharedHeap* sh = SharedHeap::heap(); 61 #ifdef ASSERT 62 if (sh->collector_policy()->should_clear_all_soft_refs()) { 63 assert(clear_all_softrefs, "Policy should have been checked earler"); 64 } 65 #endif 66 // hook up weak ref data so it can be used during Mark-Sweep 67 assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); 68 assert(rp != NULL, "should be non-NULL"); 69 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition"); 70 71 GenMarkSweep::_ref_processor = rp; 72 rp->setup_policy(clear_all_softrefs); 73 74 // When collecting the permanent generation Method*s may be moving, 75 // so we either have to flush all bcp data or convert it into bci. 76 CodeCache::gc_prologue(); 77 Threads::gc_prologue(); 78 79 bool marked_for_unloading = false; 80 81 allocate_stacks(); 82 83 // We should save the marks of the currently locked biased monitors. 84 // The marking doesn't preserve the marks of biased objects. 85 BiasedLocking::preserve_marks(); 86 87 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); 88 89 mark_sweep_phase2(); 90 91 // Don't add any more derived pointers during phase3 92 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 93 94 mark_sweep_phase3(); 95 96 mark_sweep_phase4(); 97 98 GenMarkSweep::restore_marks(); 99 BiasedLocking::restore_marks(); 100 GenMarkSweep::deallocate_stacks(); 101 102 // "free at last gc" is calculated from these. 103 // CHF: cheating for now!!! 104 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity()); 105 // Universe::set_heap_used_at_last_gc(Universe::heap()->used()); 106 107 Threads::gc_epilogue(); 108 CodeCache::gc_epilogue(); 109 JvmtiExport::gc_epilogue(); 110 111 // refs processing: clean slate 112 GenMarkSweep::_ref_processor = NULL; 113 } 114 115 116 void G1MarkSweep::allocate_stacks() { 117 GenMarkSweep::_preserved_count_max = 0; 118 GenMarkSweep::_preserved_marks = NULL; 119 GenMarkSweep::_preserved_count = 0; 120 } 121 122 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, 123 bool clear_all_softrefs) { 124 // Recursively traverse all live objects and mark them 125 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer()); 126 GenMarkSweep::trace(" 1"); 127 128 SharedHeap* sh = SharedHeap::heap(); 129 130 // Need cleared claim bits for the strong roots processing 131 ClassLoaderDataGraph::clear_claimed_marks(); 132 133 sh->process_strong_roots(true, // activate StrongRootsScope 134 SharedHeap::SO_SystemClasses, 135 &GenMarkSweep::follow_root_closure, 136 &GenMarkSweep::follow_klass_closure); 137 138 // Process reference objects found during marking 139 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 140 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity"); 141 142 rp->setup_policy(clear_all_softrefs); 143 const ReferenceProcessorStats& stats = 144 rp->process_discovered_references(&GenMarkSweep::is_alive, 145 &GenMarkSweep::keep_alive, 146 &GenMarkSweep::follow_stack_closure, 147 NULL, 148 gc_timer()); 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 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); 166 167 if (VerifyDuringGC) { 168 HandleMark hm; // handle scope 169 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); 170 Universe::heap()->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 Universe::heap()->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 class G1PrepareCompactClosure: public HeapRegionClosure { 194 G1CollectedHeap* _g1h; 195 ModRefBarrierSet* _mrbs; 196 CompactPoint _cp; 197 HumongousRegionSet _humongous_proxy_set; 198 199 void free_humongous_region(HeapRegion* hr) { 200 HeapWord* end = hr->end(); 201 size_t dummy_pre_used; 202 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 203 204 assert(hr->startsHumongous(), 205 "Only the start of a humongous region should be freed."); 206 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list, 207 &_humongous_proxy_set, false /* par */); 208 hr->prepare_for_compaction(&_cp); 209 // Also clear the part of the card table that will be unused after 210 // compaction. 211 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 212 dummy_free_list.remove_all(); 213 } 214 215 public: 216 G1PrepareCompactClosure(CompactibleSpace* cs) 217 : _g1h(G1CollectedHeap::heap()), 218 _mrbs(_g1h->g1_barrier_set()), 219 _cp(NULL, cs, cs->initialize_threshold()), 220 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { } 221 222 void update_sets() { 223 // We'll recalculate total used bytes and recreate the free list 224 // at the end of the GC, so no point in updating those values here. 225 _g1h->update_sets_after_freeing_regions(0, /* pre_used */ 226 NULL, /* free_list */ 227 NULL, /* old_proxy_set */ 228 &_humongous_proxy_set, 229 false /* par */); 230 } 231 232 bool doHeapRegion(HeapRegion* hr) { 233 if (hr->isHumongous()) { 234 if (hr->startsHumongous()) { 235 oop obj = oop(hr->bottom()); 236 if (obj->is_gc_marked()) { 237 obj->forward_to(obj); 238 } else { 239 free_humongous_region(hr); 240 } 241 } else { 242 assert(hr->continuesHumongous(), "Invalid humongous."); 243 } 244 } else { 245 hr->prepare_for_compaction(&_cp); 246 // Also clear the part of the card table that will be unused after 247 // compaction. 248 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end())); 249 } 250 return false; 251 } 252 }; 253 254 void G1MarkSweep::mark_sweep_phase2() { 255 // Now all live objects are marked, compute the new object addresses. 256 257 // It is not required that we traverse spaces in the same order in 258 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 259 // tracking expects us to do so. See comment under phase4. 260 261 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 262 263 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer()); 264 GenMarkSweep::trace("2"); 265 266 // find the first region 267 HeapRegion* r = g1h->region_at(0); 268 CompactibleSpace* sp = r; 269 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) { 270 sp = r->next_compaction_space(); 271 } 272 273 G1PrepareCompactClosure blk(sp); 274 g1h->heap_region_iterate(&blk); 275 blk.update_sets(); 276 } 277 278 class G1AdjustPointersClosure: public HeapRegionClosure { 279 public: 280 bool doHeapRegion(HeapRegion* r) { 281 if (r->isHumongous()) { 282 if (r->startsHumongous()) { 283 // We must adjust the pointers on the single H object. 284 oop obj = oop(r->bottom()); 285 // point all the oops to the new location 286 obj->adjust_pointers(); 287 } 288 } else { 289 // This really ought to be "as_CompactibleSpace"... 290 r->adjust_pointers(); 291 } 292 return false; 293 } 294 }; 295 296 void G1MarkSweep::mark_sweep_phase3() { 297 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 298 299 // Adjust the pointers to reflect the new locations 300 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer()); 301 GenMarkSweep::trace("3"); 302 303 SharedHeap* sh = SharedHeap::heap(); 304 305 // Need cleared claim bits for the strong roots processing 306 ClassLoaderDataGraph::clear_claimed_marks(); 307 308 sh->process_strong_roots(true, // activate StrongRootsScope 309 SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_AllCodeCache, 310 &GenMarkSweep::adjust_pointer_closure, 311 &GenMarkSweep::adjust_klass_closure); 312 313 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 314 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 315 316 // Now adjust pointers in remaining weak roots. (All of which should 317 // have been cleared if they pointed to non-surviving objects.) 318 sh->process_weak_roots(&GenMarkSweep::adjust_pointer_closure); 319 320 GenMarkSweep::adjust_marks(); 321 322 G1AdjustPointersClosure blk; 323 g1h->heap_region_iterate(&blk); 324 } 325 326 class G1SpaceCompactClosure: public HeapRegionClosure { 327 public: 328 G1SpaceCompactClosure() {} 329 330 bool doHeapRegion(HeapRegion* hr) { 331 if (hr->isHumongous()) { 332 if (hr->startsHumongous()) { 333 oop obj = oop(hr->bottom()); 334 if (obj->is_gc_marked()) { 335 obj->init_mark(); 336 } else { 337 assert(hr->is_empty(), "Should have been cleared in phase 2."); 338 } 339 hr->reset_during_compaction(); 340 } 341 } else { 342 hr->compact(); 343 } 344 return false; 345 } 346 }; 347 348 void G1MarkSweep::mark_sweep_phase4() { 349 // All pointers are now adjusted, move objects accordingly 350 351 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 352 // in the same order in phase2, phase3 and phase4. We don't quite do that 353 // here (code and comment not fixed for perm removal), so we tell the validate code 354 // to use a higher index (saved from phase2) when verifying perm_gen. 355 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 356 357 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer()); 358 GenMarkSweep::trace("4"); 359 360 G1SpaceCompactClosure blk; 361 g1h->heap_region_iterate(&blk); 362 363 }