1 /* 2 * Copyright (c) 2001, 2014, 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/gcHeapSummary.hpp" 37 #include "gc_implementation/shared/gcTimer.hpp" 38 #include "gc_implementation/shared/gcTrace.hpp" 39 #include "gc_implementation/shared/gcTraceTime.hpp" 40 #include "memory/gcLocker.hpp" 41 #include "memory/genCollectedHeap.hpp" 42 #include "memory/modRefBarrierSet.hpp" 43 #include "memory/referencePolicy.hpp" 44 #include "memory/space.hpp" 45 #include "oops/instanceRefKlass.hpp" 46 #include "oops/oop.inline.hpp" 47 #include "prims/jvmtiExport.hpp" 48 #include "runtime/atomic.inline.hpp" 49 #include "runtime/biasedLocking.hpp" 50 #include "runtime/fprofiler.hpp" 51 #include "runtime/synchronizer.hpp" 52 #include "runtime/thread.hpp" 53 #include "runtime/vmThread.hpp" 54 #include "utilities/copy.hpp" 55 #include "utilities/events.hpp" 56 57 class HeapRegion; 58 59 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 60 bool clear_all_softrefs) { 61 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 62 63 SharedHeap* sh = SharedHeap::heap(); 64 #ifdef ASSERT 65 if (sh->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 // "free at last gc" is calculated from these. 105 // CHF: cheating for now!!! 106 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity()); 107 // Universe::set_heap_used_at_last_gc(Universe::heap()->used()); 108 109 CodeCache::gc_epilogue(); 110 JvmtiExport::gc_epilogue(); 111 112 // refs processing: clean slate 113 GenMarkSweep::_ref_processor = NULL; 114 } 115 116 117 void G1MarkSweep::allocate_stacks() { 118 GenMarkSweep::_preserved_count_max = 0; 119 GenMarkSweep::_preserved_marks = NULL; 120 GenMarkSweep::_preserved_count = 0; 121 } 122 123 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, 124 bool clear_all_softrefs) { 125 // Recursively traverse all live objects and mark them 126 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 127 GenMarkSweep::trace(" 1"); 128 129 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 130 131 // Need cleared claim bits for the roots processing 132 ClassLoaderDataGraph::clear_claimed_marks(); 133 134 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations); 135 { 136 G1RootProcessor root_processor(g1h); 137 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, 138 &GenMarkSweep::follow_cld_closure, 139 &follow_code_closure); 140 } 141 142 // Process reference objects found during marking 143 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 144 assert(rp == g1h->ref_processor_stw(), "Sanity"); 145 146 rp->setup_policy(clear_all_softrefs); 147 const ReferenceProcessorStats& stats = 148 rp->process_discovered_references(&GenMarkSweep::is_alive, 149 &GenMarkSweep::keep_alive, 150 &GenMarkSweep::follow_stack_closure, 151 NULL, 152 gc_timer(), 153 gc_tracer()->gc_id()); 154 gc_tracer()->report_gc_reference_stats(stats); 155 156 157 // This is the point where the entire marking should have completed. 158 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); 159 160 // Unload classes and purge the SystemDictionary. 161 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 162 163 // Unload nmethods. 164 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); 165 166 // Prune dead klasses from subklass/sibling/implementor lists. 167 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); 168 169 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table. 170 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); 171 172 if (VerifyDuringGC) { 173 HandleMark hm; // handle scope 174 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); 175 Universe::heap()->prepare_for_verify(); 176 // Note: we can verify only the heap here. When an object is 177 // marked, the previous value of the mark word (including 178 // identity hash values, ages, etc) is preserved, and the mark 179 // word is set to markOop::marked_value - effectively removing 180 // any hash values from the mark word. These hash values are 181 // used when verifying the dictionaries and so removing them 182 // from the mark word can make verification of the dictionaries 183 // fail. At the end of the GC, the original mark word values 184 // (including hash values) are restored to the appropriate 185 // objects. 186 if (!VerifySilently) { 187 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying "); 188 } 189 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord); 190 if (!VerifySilently) { 191 gclog_or_tty->print_cr("]"); 192 } 193 } 194 195 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); 196 } 197 198 199 void G1MarkSweep::mark_sweep_phase2() { 200 // Now all live objects are marked, compute the new object addresses. 201 202 // It is not required that we traverse spaces in the same order in 203 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 204 // tracking expects us to do so. See comment under phase4. 205 206 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 207 GenMarkSweep::trace("2"); 208 209 prepare_compaction(); 210 } 211 212 class G1AdjustPointersClosure: public HeapRegionClosure { 213 public: 214 bool doHeapRegion(HeapRegion* r) { 215 if (r->is_humongous()) { 216 if (r->is_starts_humongous()) { 217 // We must adjust the pointers on the single H object. 218 oop obj = oop(r->bottom()); 219 // point all the oops to the new location 220 obj->adjust_pointers(); 221 } 222 } else { 223 // This really ought to be "as_CompactibleSpace"... 224 r->adjust_pointers(); 225 } 226 return false; 227 } 228 }; 229 230 class G1AlwaysTrueClosure: public BoolObjectClosure { 231 public: 232 bool do_object_b(oop p) { return true; } 233 }; 234 static G1AlwaysTrueClosure always_true; 235 236 void G1MarkSweep::mark_sweep_phase3() { 237 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 238 239 // Adjust the pointers to reflect the new locations 240 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 241 GenMarkSweep::trace("3"); 242 243 // Need cleared claim bits for the roots processing 244 ClassLoaderDataGraph::clear_claimed_marks(); 245 246 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations); 247 { 248 G1RootProcessor root_processor(g1h); 249 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure, 250 &GenMarkSweep::adjust_cld_closure, 251 &adjust_code_closure); 252 } 253 254 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 255 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 256 257 // Now adjust pointers in remaining weak roots. (All of which should 258 // have been cleared if they pointed to non-surviving objects.) 259 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure); 260 261 if (G1StringDedup::is_enabled()) { 262 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure); 263 } 264 265 GenMarkSweep::adjust_marks(); 266 267 G1AdjustPointersClosure blk; 268 g1h->heap_region_iterate(&blk); 269 } 270 271 class G1SpaceCompactClosure: public HeapRegionClosure { 272 public: 273 G1SpaceCompactClosure() {} 274 275 bool doHeapRegion(HeapRegion* hr) { 276 if (hr->is_humongous()) { 277 if (hr->is_starts_humongous()) { 278 oop obj = oop(hr->bottom()); 279 if (obj->is_gc_marked()) { 280 obj->init_mark(); 281 } else { 282 assert(hr->is_empty(), "Should have been cleared in phase 2."); 283 } 284 hr->reset_during_compaction(); 285 } 286 } else { 287 hr->compact(); 288 } 289 return false; 290 } 291 }; 292 293 void G1MarkSweep::mark_sweep_phase4() { 294 // All pointers are now adjusted, move objects accordingly 295 296 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 297 // in the same order in phase2, phase3 and phase4. We don't quite do that 298 // here (code and comment not fixed for perm removal), so we tell the validate code 299 // to use a higher index (saved from phase2) when verifying perm_gen. 300 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 301 302 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 303 GenMarkSweep::trace("4"); 304 305 G1SpaceCompactClosure blk; 306 g1h->heap_region_iterate(&blk); 307 308 } 309 310 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) { 311 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 312 g1h->heap_region_iterate(blk); 313 blk->update_sets(); 314 } 315 316 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) { 317 HeapWord* end = hr->end(); 318 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 319 320 assert(hr->is_starts_humongous(), 321 "Only the start of a humongous region should be freed."); 322 323 hr->set_containing_set(NULL); 324 _humongous_regions_removed.increment(1u, hr->capacity()); 325 326 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */); 327 prepare_for_compaction(hr, end); 328 dummy_free_list.remove_all(); 329 } 330 331 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) { 332 // If this is the first live region that we came across which we can compact, 333 // initialize the CompactPoint. 334 if (!is_cp_initialized()) { 335 _cp.space = hr; 336 _cp.threshold = hr->initialize_threshold(); 337 } 338 prepare_for_compaction_work(&_cp, hr, end); 339 } 340 341 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp, 342 HeapRegion* hr, 343 HeapWord* end) { 344 hr->prepare_for_compaction(cp); 345 // Also clear the part of the card table that will be unused after 346 // compaction. 347 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 348 } 349 350 void G1PrepareCompactClosure::update_sets() { 351 // We'll recalculate total used bytes and recreate the free list 352 // at the end of the GC, so no point in updating those values here. 353 HeapRegionSetCount empty_set; 354 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed); 355 } 356 357 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) { 358 if (hr->is_humongous()) { 359 if (hr->is_starts_humongous()) { 360 oop obj = oop(hr->bottom()); 361 if (obj->is_gc_marked()) { 362 obj->forward_to(obj); 363 } else { 364 free_humongous_region(hr); 365 } 366 } else { 367 assert(hr->is_continues_humongous(), "Invalid humongous."); 368 } 369 } else { 370 prepare_for_compaction(hr, hr->end()); 371 } 372 return false; 373 }