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/g1/g1Log.hpp" 33 #include "gc/g1/g1MarkSweep.hpp" 34 #include "gc/g1/g1RootProcessor.hpp" 35 #include "gc/g1/g1StringDedup.hpp" 36 #include "gc/serial/markSweep.inline.hpp" 37 #include "gc/shared/gcHeapSummary.hpp" 38 #include "gc/shared/gcLocker.hpp" 39 #include "gc/shared/gcTimer.hpp" 40 #include "gc/shared/gcTrace.hpp" 41 #include "gc/shared/gcTraceTime.hpp" 42 #include "gc/shared/genCollectedHeap.hpp" 43 #include "gc/shared/modRefBarrierSet.hpp" 44 #include "gc/shared/referencePolicy.hpp" 45 #include "gc/shared/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 bool G1MarkSweep::_archive_check_enabled = false; 61 G1ArchiveRegionMap G1MarkSweep::_archive_region_map; 62 63 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 64 bool clear_all_softrefs) { 65 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 66 67 #ifdef ASSERT 68 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) { 69 assert(clear_all_softrefs, "Policy should have been checked earler"); 70 } 71 #endif 72 // hook up weak ref data so it can be used during Mark-Sweep 73 assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); 74 assert(rp != NULL, "should be non-NULL"); 75 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition"); 76 77 GenMarkSweep::_ref_processor = rp; 78 rp->setup_policy(clear_all_softrefs); 79 80 // When collecting the permanent generation Method*s may be moving, 81 // so we either have to flush all bcp data or convert it into bci. 82 CodeCache::gc_prologue(); 83 84 bool marked_for_unloading = false; 85 86 allocate_stacks(); 87 88 // We should save the marks of the currently locked biased monitors. 89 // The marking doesn't preserve the marks of biased objects. 90 BiasedLocking::preserve_marks(); 91 92 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); 93 94 mark_sweep_phase2(); 95 96 // Don't add any more derived pointers during phase3 97 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 98 99 mark_sweep_phase3(); 100 101 mark_sweep_phase4(); 102 103 GenMarkSweep::restore_marks(); 104 BiasedLocking::restore_marks(); 105 GenMarkSweep::deallocate_stacks(); 106 107 CodeCache::gc_epilogue(); 108 JvmtiExport::gc_epilogue(); 109 110 // refs processing: clean slate 111 GenMarkSweep::_ref_processor = NULL; 112 } 113 114 115 void G1MarkSweep::allocate_stacks() { 116 GenMarkSweep::_preserved_count_max = 0; 117 GenMarkSweep::_preserved_marks = NULL; 118 GenMarkSweep::_preserved_count = 0; 119 } 120 121 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, 122 bool clear_all_softrefs) { 123 // Recursively traverse all live objects and mark them 124 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 125 126 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 127 128 // Need cleared claim bits for the roots processing 129 ClassLoaderDataGraph::clear_claimed_marks(); 130 131 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations); 132 { 133 G1RootProcessor root_processor(g1h, 1); 134 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, 135 &GenMarkSweep::follow_cld_closure, 136 &follow_code_closure); 137 } 138 139 // Process reference objects found during marking 140 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 141 assert(rp == g1h->ref_processor_stw(), "Sanity"); 142 143 rp->setup_policy(clear_all_softrefs); 144 const ReferenceProcessorStats& stats = 145 rp->process_discovered_references(&GenMarkSweep::is_alive, 146 &GenMarkSweep::keep_alive, 147 &GenMarkSweep::follow_stack_closure, 148 NULL, 149 gc_timer(), 150 gc_tracer()->gc_id()); 151 gc_tracer()->report_gc_reference_stats(stats); 152 153 154 // This is the point where the entire marking should have completed. 155 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); 156 157 // Unload classes and purge the SystemDictionary. 158 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 159 160 // Unload nmethods. 161 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); 162 163 // Prune dead klasses from subklass/sibling/implementor lists. 164 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); 165 166 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table. 167 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); 168 169 if (VerifyDuringGC) { 170 HandleMark hm; // handle scope 171 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); 172 g1h->prepare_for_verify(); 173 // Note: we can verify only the heap here. When an object is 174 // marked, the previous value of the mark word (including 175 // identity hash values, ages, etc) is preserved, and the mark 176 // word is set to markOop::marked_value - effectively removing 177 // any hash values from the mark word. These hash values are 178 // used when verifying the dictionaries and so removing them 179 // from the mark word can make verification of the dictionaries 180 // fail. At the end of the GC, the original mark word values 181 // (including hash values) are restored to the appropriate 182 // objects. 183 if (!VerifySilently) { 184 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying "); 185 } 186 g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord); 187 if (!VerifySilently) { 188 gclog_or_tty->print_cr("]"); 189 } 190 } 191 192 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); 193 } 194 195 196 void G1MarkSweep::mark_sweep_phase2() { 197 // Now all live objects are marked, compute the new object addresses. 198 199 // It is not required that we traverse spaces in the same order in 200 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 201 // tracking expects us to do so. See comment under phase4. 202 203 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 204 205 prepare_compaction(); 206 } 207 208 class G1AdjustPointersClosure: public HeapRegionClosure { 209 public: 210 bool doHeapRegion(HeapRegion* r) { 211 if (r->is_humongous()) { 212 if (r->is_starts_humongous()) { 213 // We must adjust the pointers on the single H object. 214 oop obj = oop(r->bottom()); 215 // point all the oops to the new location 216 MarkSweep::adjust_pointers(obj); 217 } 218 } else if (!r->is_pinned()) { 219 // This really ought to be "as_CompactibleSpace"... 220 r->adjust_pointers(); 221 } 222 return false; 223 } 224 }; 225 226 class G1AlwaysTrueClosure: public BoolObjectClosure { 227 public: 228 bool do_object_b(oop p) { return true; } 229 }; 230 static G1AlwaysTrueClosure always_true; 231 232 void G1MarkSweep::mark_sweep_phase3() { 233 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 234 235 // Adjust the pointers to reflect the new locations 236 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id()); 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, 1); 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 if (!hr->is_pinned()) { 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()); 298 299 G1SpaceCompactClosure blk; 300 g1h->heap_region_iterate(&blk); 301 302 } 303 304 void G1MarkSweep::enable_archive_object_check() { 305 assert(!_archive_check_enabled, "archive range check already enabled"); 306 _archive_check_enabled = true; 307 size_t length = Universe::heap()->max_capacity(); 308 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(), 309 (HeapWord*)Universe::heap()->base() + length, 310 HeapRegion::GrainBytes); 311 } 312 313 void G1MarkSweep::mark_range_archive(MemRegion range, bool is_archive) { 314 assert(_archive_check_enabled, "archive range check not enabled"); 315 _archive_region_map.set_by_address(range, is_archive); 316 } 317 318 bool G1MarkSweep::in_archive_range(oop object) { 319 // This is the out-of-line part of is_archive_object test, done separately 320 // to avoid additional performance impact when the check is not enabled. 321 return _archive_region_map.get_by_address((HeapWord*)object); 322 } 323 324 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) { 325 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 326 g1h->heap_region_iterate(blk); 327 blk->update_sets(); 328 } 329 330 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) { 331 HeapWord* end = hr->end(); 332 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 333 334 assert(hr->is_starts_humongous(), 335 "Only the start of a humongous region should be freed."); 336 337 hr->set_containing_set(NULL); 338 _humongous_regions_removed.increment(1u, hr->capacity()); 339 340 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */); 341 prepare_for_compaction(hr, end); 342 dummy_free_list.remove_all(); 343 } 344 345 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) { 346 // If this is the first live region that we came across which we can compact, 347 // initialize the CompactPoint. 348 if (!is_cp_initialized()) { 349 _cp.space = hr; 350 _cp.threshold = hr->initialize_threshold(); 351 } 352 prepare_for_compaction_work(&_cp, hr, end); 353 } 354 355 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp, 356 HeapRegion* hr, 357 HeapWord* end) { 358 hr->prepare_for_compaction(cp); 359 // Also clear the part of the card table that will be unused after 360 // compaction. 361 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 362 } 363 364 void G1PrepareCompactClosure::update_sets() { 365 // We'll recalculate total used bytes and recreate the free list 366 // at the end of the GC, so no point in updating those values here. 367 HeapRegionSetCount empty_set; 368 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed); 369 } 370 371 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) { 372 if (hr->is_humongous()) { 373 if (hr->is_starts_humongous()) { 374 oop obj = oop(hr->bottom()); 375 if (obj->is_gc_marked()) { 376 obj->forward_to(obj); 377 } else { 378 free_humongous_region(hr); 379 } 380 } else { 381 assert(hr->is_continues_humongous(), "Invalid humongous."); 382 } 383 } else if (!hr->is_pinned()) { 384 prepare_for_compaction(hr, hr->end()); 385 } 386 return false; 387 }