1 /* 2 * Copyright (c) 2001, 2012, 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 "memory/gcLocker.hpp" 35 #include "memory/genCollectedHeap.hpp" 36 #include "memory/modRefBarrierSet.hpp" 37 #include "memory/referencePolicy.hpp" 38 #include "memory/space.hpp" 39 #include "oops/instanceRefKlass.hpp" 40 #include "oops/oop.inline.hpp" 41 #include "prims/jvmtiExport.hpp" 42 #include "runtime/biasedLocking.hpp" 43 #include "runtime/fprofiler.hpp" 44 #include "runtime/synchronizer.hpp" 45 #include "runtime/thread.hpp" 46 #include "runtime/vmThread.hpp" 47 #include "utilities/copy.hpp" 48 #include "utilities/events.hpp" 49 50 class HeapRegion; 51 52 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 53 bool clear_all_softrefs) { 54 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 55 56 SharedHeap* sh = SharedHeap::heap(); 57 #ifdef ASSERT 58 if (sh->collector_policy()->should_clear_all_soft_refs()) { 59 assert(clear_all_softrefs, "Policy should have been checked earler"); 60 } 61 #endif 62 // hook up weak ref data so it can be used during Mark-Sweep 63 assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); 64 assert(rp != NULL, "should be non-NULL"); 65 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition"); 66 67 GenMarkSweep::_ref_processor = rp; 68 rp->setup_policy(clear_all_softrefs); 69 70 // When collecting the permanent generation Method*s may be moving, 71 // so we either have to flush all bcp data or convert it into bci. 72 CodeCache::gc_prologue(); 73 Threads::gc_prologue(); 74 75 bool marked_for_unloading = false; 76 77 allocate_stacks(); 78 79 // We should save the marks of the currently locked biased monitors. 80 // The marking doesn't preserve the marks of biased objects. 81 BiasedLocking::preserve_marks(); 82 83 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); 84 85 mark_sweep_phase2(); 86 87 // Don't add any more derived pointers during phase3 88 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 89 90 mark_sweep_phase3(); 91 92 mark_sweep_phase4(); 93 94 GenMarkSweep::restore_marks(); 95 BiasedLocking::restore_marks(); 96 GenMarkSweep::deallocate_stacks(); 97 98 // "free at last gc" is calculated from these. 99 // CHF: cheating for now!!! 100 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity()); 101 // Universe::set_heap_used_at_last_gc(Universe::heap()->used()); 102 103 Threads::gc_epilogue(); 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 TraceTime tm("phase 1", G1Log::fine() && Verbose, true, gclog_or_tty); 122 GenMarkSweep::trace(" 1"); 123 124 SharedHeap* sh = SharedHeap::heap(); 125 126 // Need cleared claim bits for the strong roots processing 127 ClassLoaderDataGraph::clear_claimed_marks(); 128 129 sh->process_strong_roots(true, // activate StrongRootsScope 130 false, // not scavenging. 131 SharedHeap::SO_SystemClasses, 132 &GenMarkSweep::follow_root_closure, 133 &GenMarkSweep::follow_code_root_closure, 134 &GenMarkSweep::follow_klass_closure); 135 136 // Process reference objects found during marking 137 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 138 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity"); 139 140 rp->setup_policy(clear_all_softrefs); 141 rp->process_discovered_references(&GenMarkSweep::is_alive, 142 &GenMarkSweep::keep_alive, 143 &GenMarkSweep::follow_stack_closure, 144 NULL); 145 146 147 // This is the point where the entire marking should have completed. 148 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); 149 150 // Unload classes and purge the SystemDictionary. 151 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 152 153 // Unload nmethods. 154 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); 155 156 // Prune dead klasses from subklass/sibling/implementor lists. 157 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); 158 159 // Delete entries for dead interned strings. 160 StringTable::unlink(&GenMarkSweep::is_alive); 161 162 // Clean up unreferenced symbols in symbol table. 163 SymbolTable::unlink(); 164 165 if (VerifyDuringGC) { 166 HandleMark hm; // handle scope 167 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); 168 Universe::heap()->prepare_for_verify(); 169 // Note: we can verify only the heap here. When an object is 170 // marked, the previous value of the mark word (including 171 // identity hash values, ages, etc) is preserved, and the mark 172 // word is set to markOop::marked_value - effectively removing 173 // any hash values from the mark word. These hash values are 174 // used when verifying the dictionaries and so removing them 175 // from the mark word can make verification of the dictionaries 176 // fail. At the end of the GC, the orginal mark word values 177 // (including hash values) are restored to the appropriate 178 // objects. 179 if (!VerifySilently) { 180 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying "); 181 } 182 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord); 183 if (!VerifySilently) { 184 gclog_or_tty->print_cr("]"); 185 } 186 } 187 } 188 189 class G1PrepareCompactClosure: public HeapRegionClosure { 190 G1CollectedHeap* _g1h; 191 ModRefBarrierSet* _mrbs; 192 CompactPoint _cp; 193 HumongousRegionSet _humongous_proxy_set; 194 195 void free_humongous_region(HeapRegion* hr) { 196 HeapWord* end = hr->end(); 197 size_t dummy_pre_used; 198 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 199 200 assert(hr->startsHumongous(), 201 "Only the start of a humongous region should be freed."); 202 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list, 203 &_humongous_proxy_set, false /* par */); 204 hr->prepare_for_compaction(&_cp); 205 // Also clear the part of the card table that will be unused after 206 // compaction. 207 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 208 dummy_free_list.remove_all(); 209 } 210 211 public: 212 G1PrepareCompactClosure(CompactibleSpace* cs) 213 : _g1h(G1CollectedHeap::heap()), 214 _mrbs(G1CollectedHeap::heap()->mr_bs()), 215 _cp(NULL, cs, cs->initialize_threshold()), 216 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { } 217 218 void update_sets() { 219 // We'll recalculate total used bytes and recreate the free list 220 // at the end of the GC, so no point in updating those values here. 221 _g1h->update_sets_after_freeing_regions(0, /* pre_used */ 222 NULL, /* free_list */ 223 NULL, /* old_proxy_set */ 224 &_humongous_proxy_set, 225 false /* par */); 226 } 227 228 bool doHeapRegion(HeapRegion* hr) { 229 if (hr->isHumongous()) { 230 if (hr->startsHumongous()) { 231 oop obj = oop(hr->bottom()); 232 if (obj->is_gc_marked()) { 233 obj->forward_to(obj); 234 } else { 235 free_humongous_region(hr); 236 } 237 } else { 238 assert(hr->continuesHumongous(), "Invalid humongous."); 239 } 240 } else { 241 hr->prepare_for_compaction(&_cp); 242 // Also clear the part of the card table that will be unused after 243 // compaction. 244 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end())); 245 } 246 return false; 247 } 248 }; 249 250 void G1MarkSweep::mark_sweep_phase2() { 251 // Now all live objects are marked, compute the new object addresses. 252 253 // It is not required that we traverse spaces in the same order in 254 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 255 // tracking expects us to do so. See comment under phase4. 256 257 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 258 259 TraceTime tm("phase 2", G1Log::fine() && Verbose, true, gclog_or_tty); 260 GenMarkSweep::trace("2"); 261 262 // find the first region 263 HeapRegion* r = g1h->region_at(0); 264 CompactibleSpace* sp = r; 265 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) { 266 sp = r->next_compaction_space(); 267 } 268 269 G1PrepareCompactClosure blk(sp); 270 g1h->heap_region_iterate(&blk); 271 blk.update_sets(); 272 } 273 274 class G1AdjustPointersClosure: public HeapRegionClosure { 275 public: 276 bool doHeapRegion(HeapRegion* r) { 277 if (r->isHumongous()) { 278 if (r->startsHumongous()) { 279 // We must adjust the pointers on the single H object. 280 oop obj = oop(r->bottom()); 281 // point all the oops to the new location 282 obj->adjust_pointers(); 283 } 284 } else { 285 // This really ought to be "as_CompactibleSpace"... 286 r->adjust_pointers(); 287 } 288 return false; 289 } 290 }; 291 292 void G1MarkSweep::mark_sweep_phase3() { 293 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 294 295 // Adjust the pointers to reflect the new locations 296 TraceTime tm("phase 3", G1Log::fine() && Verbose, true, gclog_or_tty); 297 GenMarkSweep::trace("3"); 298 299 SharedHeap* sh = SharedHeap::heap(); 300 301 // Need cleared claim bits for the strong roots processing 302 ClassLoaderDataGraph::clear_claimed_marks(); 303 304 sh->process_strong_roots(true, // activate StrongRootsScope 305 false, // not scavenging. 306 SharedHeap::SO_AllClasses, 307 &GenMarkSweep::adjust_pointer_closure, 308 NULL, // do not touch code cache here 309 &GenMarkSweep::adjust_klass_closure); 310 311 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 312 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 313 314 // Now adjust pointers in remaining weak roots. (All of which should 315 // have been cleared if they pointed to non-surviving objects.) 316 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_pointer_closure); 317 318 GenMarkSweep::adjust_marks(); 319 320 G1AdjustPointersClosure blk; 321 g1h->heap_region_iterate(&blk); 322 } 323 324 class G1SpaceCompactClosure: public HeapRegionClosure { 325 public: 326 G1SpaceCompactClosure() {} 327 328 bool doHeapRegion(HeapRegion* hr) { 329 if (hr->isHumongous()) { 330 if (hr->startsHumongous()) { 331 oop obj = oop(hr->bottom()); 332 if (obj->is_gc_marked()) { 333 obj->init_mark(); 334 } else { 335 assert(hr->is_empty(), "Should have been cleared in phase 2."); 336 } 337 hr->reset_during_compaction(); 338 } 339 } else { 340 hr->compact(); 341 } 342 return false; 343 } 344 }; 345 346 void G1MarkSweep::mark_sweep_phase4() { 347 // All pointers are now adjusted, move objects accordingly 348 349 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 350 // in the same order in phase2, phase3 and phase4. We don't quite do that 351 // here (code and comment not fixed for perm removal), so we tell the validate code 352 // to use a higher index (saved from phase2) when verifying perm_gen. 353 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 354 355 TraceTime tm("phase 4", G1Log::fine() && Verbose, true, gclog_or_tty); 356 GenMarkSweep::trace("4"); 357 358 G1SpaceCompactClosure blk; 359 g1h->heap_region_iterate(&blk); 360 361 }