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/g1MarkSweep.hpp" 33 #include "gc/g1/g1RootProcessor.hpp" 34 #include "gc/g1/g1StringDedup.hpp" 35 #include "gc/serial/markSweep.inline.hpp" 36 #include "gc/shared/gcHeapSummary.hpp" 37 #include "gc/shared/gcLocker.hpp" 38 #include "gc/shared/gcTimer.hpp" 39 #include "gc/shared/gcTrace.hpp" 40 #include "gc/shared/gcTraceTime.inline.hpp" 41 #include "gc/shared/genCollectedHeap.hpp" 42 #include "gc/shared/modRefBarrierSet.hpp" 43 #include "gc/shared/referencePolicy.hpp" 44 #include "gc/shared/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 bool G1MarkSweep::_archive_check_enabled = false; 60 G1ArchiveRegionMap G1MarkSweep::_archive_region_map; 61 62 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 63 bool clear_all_softrefs) { 64 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 65 66 #ifdef ASSERT 67 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) { 68 assert(clear_all_softrefs, "Policy should have been checked earler"); 69 } 70 #endif 71 // hook up weak ref data so it can be used during Mark-Sweep 72 assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); 73 assert(rp != NULL, "should be non-NULL"); 74 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition"); 75 76 GenMarkSweep::set_ref_processor(rp); 77 rp->setup_policy(clear_all_softrefs); 78 79 // When collecting the permanent generation Method*s may be moving, 80 // so we either have to flush all bcp data or convert it into bci. 81 CodeCache::gc_prologue(); 82 83 bool marked_for_unloading = false; 84 85 allocate_stacks(); 86 87 // We should save the marks of the currently locked biased monitors. 88 // The marking doesn't preserve the marks of biased objects. 89 BiasedLocking::preserve_marks(); 90 91 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); 92 93 mark_sweep_phase2(); 94 95 #if defined(COMPILER2) || INCLUDE_JVMCI 96 // Don't add any more derived pointers during phase3 97 DerivedPointerTable::set_active(false); 98 #endif 99 100 mark_sweep_phase3(); 101 102 mark_sweep_phase4(); 103 104 GenMarkSweep::restore_marks(); 105 BiasedLocking::restore_marks(); 106 GenMarkSweep::deallocate_stacks(); 107 108 CodeCache::gc_epilogue(); 109 JvmtiExport::gc_epilogue(); 110 111 // refs processing: clean slate 112 GenMarkSweep::set_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(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer()); 126 127 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 128 129 // Need cleared claim bits for the roots processing 130 ClassLoaderDataGraph::clear_claimed_marks(); 131 132 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations); 133 if (ClassUnloading) { 134 G1RootProcessor root_processor(g1h, 1); 135 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, 136 &GenMarkSweep::follow_cld_closure, 137 &follow_code_closure); 138 } else { 139 G1RootProcessor root_processor(g1h, 1); 140 root_processor.process_all_roots(&GenMarkSweep::follow_root_closure, 141 &GenMarkSweep::follow_cld_closure, 142 &follow_code_closure); 143 } 144 145 { 146 GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer()); 147 148 // Process reference objects found during marking 149 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 150 assert(rp == g1h->ref_processor_stw(), "Sanity"); 151 152 rp->setup_policy(clear_all_softrefs); 153 const ReferenceProcessorStats& stats = 154 rp->process_discovered_references(&GenMarkSweep::is_alive, 155 &GenMarkSweep::keep_alive, 156 &GenMarkSweep::follow_stack_closure, 157 NULL, 158 gc_timer()); 159 gc_tracer()->report_gc_reference_stats(stats); 160 } 161 162 // This is the point where the entire marking should have completed. 163 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); 164 165 if (ClassUnloading) { 166 GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer()); 167 168 // Unload classes and purge the SystemDictionary. 169 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 170 171 // Unload nmethods. 172 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); 173 174 // Prune dead klasses from subklass/sibling/implementor lists. 175 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); 176 } 177 178 { 179 GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer()); 180 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table. 181 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); 182 } 183 184 if (G1StringDedup::is_enabled()) { 185 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer()); 186 G1StringDedup::unlink(&GenMarkSweep::is_alive); 187 } 188 189 if (VerifyDuringGC) { 190 HandleMark hm; // handle scope 191 #if defined(COMPILER2) || INCLUDE_JVMCI 192 DerivedPointerTableDeactivate dpt_deact; 193 #endif 194 g1h->prepare_for_verify(); 195 // Note: we can verify only the heap here. When an object is 196 // marked, the previous value of the mark word (including 197 // identity hash values, ages, etc) is preserved, and the mark 198 // word is set to markOop::marked_value - effectively removing 199 // any hash values from the mark word. These hash values are 200 // used when verifying the dictionaries and so removing them 201 // from the mark word can make verification of the dictionaries 202 // fail. At the end of the GC, the original mark word values 203 // (including hash values) are restored to the appropriate 204 // objects. 205 GCTraceTime(Info, gc, verify)("During GC (full)"); 206 g1h->verify(VerifyOption_G1UseMarkWord); 207 } 208 209 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); 210 } 211 212 213 void G1MarkSweep::mark_sweep_phase2() { 214 // Now all live objects are marked, compute the new object addresses. 215 216 // It is not required that we traverse spaces in the same order in 217 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 218 // tracking expects us to do so. See comment under phase4. 219 220 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer()); 221 222 prepare_compaction(); 223 } 224 225 class G1AdjustPointersClosure: public HeapRegionClosure { 226 public: 227 bool doHeapRegion(HeapRegion* r) { 228 if (r->is_humongous()) { 229 if (r->is_starts_humongous()) { 230 // We must adjust the pointers on the single H object. 231 oop obj = oop(r->bottom()); 232 // point all the oops to the new location 233 MarkSweep::adjust_pointers(obj); 234 } 235 } else if (!r->is_pinned()) { 236 // This really ought to be "as_CompactibleSpace"... 237 r->adjust_pointers(); 238 } 239 return false; 240 } 241 }; 242 243 void G1MarkSweep::mark_sweep_phase3() { 244 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 245 246 // Adjust the pointers to reflect the new locations 247 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer()); 248 249 // Need cleared claim bits for the roots processing 250 ClassLoaderDataGraph::clear_claimed_marks(); 251 252 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations); 253 { 254 G1RootProcessor root_processor(g1h, 1); 255 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure, 256 &GenMarkSweep::adjust_cld_closure, 257 &adjust_code_closure); 258 } 259 260 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 261 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 262 263 // Now adjust pointers in remaining weak roots. (All of which should 264 // have been cleared if they pointed to non-surviving objects.) 265 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 266 267 if (G1StringDedup::is_enabled()) { 268 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure); 269 } 270 271 GenMarkSweep::adjust_marks(); 272 273 G1AdjustPointersClosure blk; 274 g1h->heap_region_iterate(&blk); 275 } 276 277 class G1SpaceCompactClosure: public HeapRegionClosure { 278 public: 279 G1SpaceCompactClosure() {} 280 281 bool doHeapRegion(HeapRegion* hr) { 282 if (hr->is_humongous()) { 283 if (hr->is_starts_humongous()) { 284 oop obj = oop(hr->bottom()); 285 if (obj->is_gc_marked()) { 286 obj->init_mark(); 287 } else { 288 assert(hr->is_empty(), "Should have been cleared in phase 2."); 289 } 290 } 291 hr->reset_during_compaction(); 292 } else if (!hr->is_pinned()) { 293 hr->compact(); 294 } 295 return false; 296 } 297 }; 298 299 void G1MarkSweep::mark_sweep_phase4() { 300 // All pointers are now adjusted, move objects accordingly 301 302 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 303 // in the same order in phase2, phase3 and phase4. We don't quite do that 304 // here (code and comment not fixed for perm removal), so we tell the validate code 305 // to use a higher index (saved from phase2) when verifying perm_gen. 306 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 307 308 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer()); 309 310 G1SpaceCompactClosure blk; 311 g1h->heap_region_iterate(&blk); 312 313 } 314 315 void G1MarkSweep::enable_archive_object_check() { 316 assert(!_archive_check_enabled, "archive range check already enabled"); 317 _archive_check_enabled = true; 318 size_t length = Universe::heap()->max_capacity(); 319 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(), 320 (HeapWord*)Universe::heap()->base() + length, 321 HeapRegion::GrainBytes); 322 } 323 324 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) { 325 assert(_archive_check_enabled, "archive range check not enabled"); 326 _archive_region_map.set_by_address(range, is_archive); 327 } 328 329 bool G1MarkSweep::in_archive_range(oop object) { 330 // This is the out-of-line part of is_archive_object test, done separately 331 // to avoid additional performance impact when the check is not enabled. 332 return _archive_region_map.get_by_address((HeapWord*)object); 333 } 334 335 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) { 336 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 337 g1h->heap_region_iterate(blk); 338 blk->update_sets(); 339 } 340 341 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) { 342 HeapWord* end = hr->end(); 343 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 344 345 hr->set_containing_set(NULL); 346 _humongous_regions_removed++; 347 348 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */); 349 prepare_for_compaction(hr, end); 350 dummy_free_list.remove_all(); 351 } 352 353 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) { 354 // If this is the first live region that we came across which we can compact, 355 // initialize the CompactPoint. 356 if (!is_cp_initialized()) { 357 _cp.space = hr; 358 _cp.threshold = hr->initialize_threshold(); 359 } 360 prepare_for_compaction_work(&_cp, hr, end); 361 } 362 363 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp, 364 HeapRegion* hr, 365 HeapWord* end) { 366 hr->prepare_for_compaction(cp); 367 // Also clear the part of the card table that will be unused after 368 // compaction. 369 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 370 } 371 372 void G1PrepareCompactClosure::update_sets() { 373 // We'll recalculate total used bytes and recreate the free list 374 // at the end of the GC, so no point in updating those values here. 375 _g1h->remove_from_old_sets(0, _humongous_regions_removed); 376 } 377 378 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) { 379 if (hr->is_humongous()) { 380 oop obj = oop(hr->humongous_start_region()->bottom()); 381 if (hr->is_starts_humongous() && obj->is_gc_marked()) { 382 obj->forward_to(obj); 383 } 384 if (!obj->is_gc_marked()) { 385 free_humongous_region(hr); 386 } 387 } else if (!hr->is_pinned()) { 388 prepare_for_compaction(hr, hr->end()); 389 } 390 return false; 391 }