1/* 2 * Copyright (c) 2001, 2016, 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.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 57class HeapRegion; 58 59bool G1MarkSweep::_archive_check_enabled = false; 60G1ArchiveRegionMap G1MarkSweep::_archive_region_map; 61 62void 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 116void G1MarkSweep::allocate_stacks() { 117 GenMarkSweep::_preserved_count_max = 0; 118 GenMarkSweep::_preserved_marks = NULL; 119 GenMarkSweep::_preserved_count = 0; 120} 121 122void 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 { 134 G1RootProcessor root_processor(g1h, 1); 135 if (ClassUnloading) { 136 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, 137 &GenMarkSweep::follow_cld_closure, 138 &follow_code_closure); 139 } else { 140 root_processor.process_all_roots_no_string_table( 141 &GenMarkSweep::follow_root_closure, 142 &GenMarkSweep::follow_cld_closure, 143 &follow_code_closure); 144 } 145 } 146 147 { 148 GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer()); 149 150 // Process reference objects found during marking 151 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 152 assert(rp == g1h->ref_processor_stw(), "Sanity"); 153 154 rp->setup_policy(clear_all_softrefs); 155 const ReferenceProcessorStats& stats = 156 rp->process_discovered_references(&GenMarkSweep::is_alive, 157 &GenMarkSweep::keep_alive, 158 &GenMarkSweep::follow_stack_closure, 159 NULL, 160 gc_timer()); 161 gc_tracer()->report_gc_reference_stats(stats); 162 } 163 164 // This is the point where the entire marking should have completed. 165 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); 166 167 if (ClassUnloading) { 168 GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer()); 169 170 // Unload classes and purge the SystemDictionary. 171 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 172 173 // Unload nmethods. 174 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); 175 176 // Prune dead klasses from subklass/sibling/implementor lists. 177 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); 178 } 179 180 { 181 GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer()); 182 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table. 183 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); 184 } 185 186 if (G1StringDedup::is_enabled()) { 187 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer()); 188 G1StringDedup::unlink(&GenMarkSweep::is_alive); 189 } 190 191 if (VerifyDuringGC) { 192 HandleMark hm; // handle scope 193#if defined(COMPILER2) || INCLUDE_JVMCI 194 DerivedPointerTableDeactivate dpt_deact; 195#endif 196 g1h->prepare_for_verify(); 197 // Note: we can verify only the heap here. When an object is 198 // marked, the previous value of the mark word (including 199 // identity hash values, ages, etc) is preserved, and the mark 200 // word is set to markOop::marked_value - effectively removing 201 // any hash values from the mark word. These hash values are 202 // used when verifying the dictionaries and so removing them 203 // from the mark word can make verification of the dictionaries 204 // fail. At the end of the GC, the original mark word values 205 // (including hash values) are restored to the appropriate 206 // objects. 207 GCTraceTime(Info, gc, verify)("During GC (full)"); 208 g1h->verify(VerifyOption_G1UseMarkWord); 209 } 210 211 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); 212} 213 214 215void G1MarkSweep::mark_sweep_phase2() { 216 // Now all live objects are marked, compute the new object addresses. 217 218 // It is not required that we traverse spaces in the same order in 219 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 220 // tracking expects us to do so. See comment under phase4. 221 222 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer()); 223 224 prepare_compaction(); 225} 226 227class G1AdjustPointersClosure: public HeapRegionClosure { 228 public: 229 bool doHeapRegion(HeapRegion* r) { 230 if (r->is_humongous()) { 231 if (r->is_starts_humongous()) { 232 // We must adjust the pointers on the single H object. 233 oop obj = oop(r->bottom()); 234 // point all the oops to the new location 235 MarkSweep::adjust_pointers(obj); 236 } 237 } else if (!r->is_pinned()) { 238 // This really ought to be "as_CompactibleSpace"... 239 r->adjust_pointers(); 240 } 241 return false; 242 } 243}; 244 245void G1MarkSweep::mark_sweep_phase3() { 246 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 247 248 // Adjust the pointers to reflect the new locations 249 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer()); 250 251 // Need cleared claim bits for the roots processing 252 ClassLoaderDataGraph::clear_claimed_marks(); 253 254 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations); 255 { 256 G1RootProcessor root_processor(g1h, 1); 257 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure, 258 &GenMarkSweep::adjust_cld_closure, 259 &adjust_code_closure); 260 } 261 262 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 263 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 264 265 // Now adjust pointers in remaining weak roots. (All of which should 266 // have been cleared if they pointed to non-surviving objects.) 267 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 268 269 if (G1StringDedup::is_enabled()) { 270 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure); 271 } 272 273 GenMarkSweep::adjust_marks(); 274 275 G1AdjustPointersClosure blk; 276 g1h->heap_region_iterate(&blk); 277} 278 279class G1SpaceCompactClosure: public HeapRegionClosure { 280public: 281 G1SpaceCompactClosure() {} 282 283 bool doHeapRegion(HeapRegion* hr) { 284 if (hr->is_humongous()) { 285 if (hr->is_starts_humongous()) { 286 oop obj = oop(hr->bottom()); 287 if (obj->is_gc_marked()) { 288 obj->init_mark(); 289 } else { 290 assert(hr->is_empty(), "Should have been cleared in phase 2."); 291 } 292 } 293 hr->reset_during_compaction(); 294 } else if (!hr->is_pinned()) { 295 hr->compact(); 296 } 297 return false; 298 } 299}; 300 301void G1MarkSweep::mark_sweep_phase4() { 302 // All pointers are now adjusted, move objects accordingly 303 304 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 305 // in the same order in phase2, phase3 and phase4. We don't quite do that 306 // here (code and comment not fixed for perm removal), so we tell the validate code 307 // to use a higher index (saved from phase2) when verifying perm_gen. 308 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 309 310 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer()); 311 312 G1SpaceCompactClosure blk; 313 g1h->heap_region_iterate(&blk); 314 315} 316 317void G1MarkSweep::enable_archive_object_check() { 318 assert(!_archive_check_enabled, "archive range check already enabled"); 319 _archive_check_enabled = true; 320 size_t length = Universe::heap()->max_capacity(); 321 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(), 322 (HeapWord*)Universe::heap()->base() + length, 323 HeapRegion::GrainBytes); 324} 325 326void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) { 327 assert(_archive_check_enabled, "archive range check not enabled"); 328 _archive_region_map.set_by_address(range, is_archive); 329} 330 331bool G1MarkSweep::in_archive_range(oop object) { 332 // This is the out-of-line part of is_archive_object test, done separately 333 // to avoid additional performance impact when the check is not enabled. 334 return _archive_region_map.get_by_address((HeapWord*)object); 335} 336 337void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) { 338 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 339 g1h->heap_region_iterate(blk); 340 blk->update_sets(); 341} 342 343void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) { 344 HeapWord* end = hr->end(); 345 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 346 347 hr->set_containing_set(NULL); 348 _humongous_regions_removed++; 349 350 _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */); 351 prepare_for_compaction(hr, end); 352 dummy_free_list.remove_all(); 353} 354 355void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) { 356 // If this is the first live region that we came across which we can compact, 357 // initialize the CompactPoint. 358 if (!is_cp_initialized()) { 359 _cp.space = hr; 360 _cp.threshold = hr->initialize_threshold(); 361 } 362 prepare_for_compaction_work(&_cp, hr, end); 363} 364 365void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp, 366 HeapRegion* hr, 367 HeapWord* end) { 368 hr->prepare_for_compaction(cp); 369 // Also clear the part of the card table that will be unused after 370 // compaction. 371 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 372} 373 374void G1PrepareCompactClosure::update_sets() { 375 // We'll recalculate total used bytes and recreate the free list 376 // at the end of the GC, so no point in updating those values here. 377 _g1h->remove_from_old_sets(0, _humongous_regions_removed); 378} 379 380bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) { 381 if (hr->is_humongous()) { 382 oop obj = oop(hr->humongous_start_region()->bottom()); 383 if (hr->is_starts_humongous() && obj->is_gc_marked()) { 384 obj->forward_to(obj); 385 } 386 if (!obj->is_gc_marked()) { 387 free_humongous_region(hr); 388 } 389 } else if (!hr->is_pinned()) { 390 prepare_for_compaction(hr, hr->end()); 391 } 392 return false; 393} 394