1 /* 2 * Copyright (c) 2001, 2017, 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/heapMonitoring.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 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 61 bool clear_all_softrefs) { 62 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 63 64 #ifdef ASSERT 65 if (G1CollectedHeap::heap()->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::set_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 #if defined(COMPILER2) || INCLUDE_JVMCI 94 // Don't add any more derived pointers during phase3 95 DerivedPointerTable::set_active(false); 96 #endif 97 98 mark_sweep_phase3(); 99 100 mark_sweep_phase4(); 101 102 GenMarkSweep::restore_marks(); 103 BiasedLocking::restore_marks(); 104 GenMarkSweep::deallocate_stacks(); 105 106 CodeCache::gc_epilogue(); 107 JvmtiExport::gc_epilogue(); 108 109 // refs processing: clean slate 110 GenMarkSweep::set_ref_processor(NULL); 111 } 112 113 114 void G1MarkSweep::allocate_stacks() { 115 GenMarkSweep::_preserved_count_max = 0; 116 GenMarkSweep::_preserved_marks = NULL; 117 GenMarkSweep::_preserved_count = 0; 118 } 119 120 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, 121 bool clear_all_softrefs) { 122 // Recursively traverse all live objects and mark them 123 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer()); 124 125 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 126 127 // Need cleared claim bits for the roots processing 128 ClassLoaderDataGraph::clear_claimed_marks(); 129 130 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations); 131 { 132 G1RootProcessor root_processor(g1h, 1); 133 if (ClassUnloading) { 134 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, 135 &GenMarkSweep::follow_cld_closure, 136 &follow_code_closure); 137 } else { 138 root_processor.process_all_roots_no_string_table( 139 &GenMarkSweep::follow_root_closure, 140 &GenMarkSweep::follow_cld_closure, 141 &follow_code_closure); 142 } 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, gc_timer()); 170 171 g1h->complete_cleaning(&GenMarkSweep::is_alive, purged_class); 172 } else { 173 GCTraceTime(Debug, gc, phases) trace("Cleanup", gc_timer()); 174 g1h->partial_cleaning(&GenMarkSweep::is_alive, true, true, G1StringDedup::is_enabled()); 175 } 176 177 if (VerifyDuringGC) { 178 HandleMark hm; // handle scope 179 #if defined(COMPILER2) || INCLUDE_JVMCI 180 DerivedPointerTableDeactivate dpt_deact; 181 #endif 182 g1h->prepare_for_verify(); 183 // Note: we can verify only the heap here. When an object is 184 // marked, the previous value of the mark word (including 185 // identity hash values, ages, etc) is preserved, and the mark 186 // word is set to markOop::marked_value - effectively removing 187 // any hash values from the mark word. These hash values are 188 // used when verifying the dictionaries and so removing them 189 // from the mark word can make verification of the dictionaries 190 // fail. At the end of the GC, the original mark word values 191 // (including hash values) are restored to the appropriate 192 // objects. 193 GCTraceTime(Info, gc, verify)("During GC (full)"); 194 g1h->verify(VerifyOption_G1UseMarkWord); 195 } 196 197 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); 198 } 199 200 201 void G1MarkSweep::mark_sweep_phase2() { 202 // Now all live objects are marked, compute the new object addresses. 203 204 // It is not required that we traverse spaces in the same order in 205 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 206 // tracking expects us to do so. See comment under phase4. 207 208 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer()); 209 210 prepare_compaction(); 211 } 212 213 class G1AdjustPointersClosure: public HeapRegionClosure { 214 public: 215 bool doHeapRegion(HeapRegion* r) { 216 if (r->is_humongous()) { 217 if (r->is_starts_humongous()) { 218 // We must adjust the pointers on the single H object. 219 oop obj = oop(r->bottom()); 220 // point all the oops to the new location 221 MarkSweep::adjust_pointers(obj); 222 } 223 } else if (!r->is_pinned()) { 224 // This really ought to be "as_CompactibleSpace"... 225 r->adjust_pointers(); 226 } 227 return false; 228 } 229 }; 230 231 void G1MarkSweep::mark_sweep_phase3() { 232 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 233 234 // Adjust the pointers to reflect the new locations 235 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer()); 236 237 // Need cleared claim bits for the roots processing 238 ClassLoaderDataGraph::clear_claimed_marks(); 239 240 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations); 241 { 242 G1RootProcessor root_processor(g1h, 1); 243 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure, 244 &GenMarkSweep::adjust_cld_closure, 245 &adjust_code_closure); 246 } 247 248 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); 249 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 250 251 // Now adjust pointers in remaining weak roots. (All of which should 252 // have been cleared if they pointed to non-surviving objects.) 253 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure); 254 HeapMonitoring::weak_oops_do(&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 } 280 hr->reset_during_compaction(); 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(Info, gc, phases) tm("Phase 4: Move objects", gc_timer()); 298 299 G1SpaceCompactClosure blk; 300 g1h->heap_region_iterate(&blk); 301 302 } 303 304 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) { 305 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 306 g1h->heap_region_iterate(blk); 307 blk->update_sets(); 308 } 309 310 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) { 311 HeapWord* end = hr->end(); 312 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); 313 314 hr->set_containing_set(NULL); 315 _humongous_regions_removed++; 316 317 _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */); 318 prepare_for_compaction(hr, end); 319 dummy_free_list.remove_all(); 320 } 321 322 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) { 323 // If this is the first live region that we came across which we can compact, 324 // initialize the CompactPoint. 325 if (!is_cp_initialized()) { 326 _cp.space = hr; 327 _cp.threshold = hr->initialize_threshold(); 328 } 329 prepare_for_compaction_work(&_cp, hr, end); 330 } 331 332 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp, 333 HeapRegion* hr, 334 HeapWord* end) { 335 hr->prepare_for_compaction(cp); 336 // Also clear the part of the card table that will be unused after 337 // compaction. 338 _mrbs->clear(MemRegion(hr->compaction_top(), end)); 339 } 340 341 void G1PrepareCompactClosure::update_sets() { 342 // We'll recalculate total used bytes and recreate the free list 343 // at the end of the GC, so no point in updating those values here. 344 _g1h->remove_from_old_sets(0, _humongous_regions_removed); 345 } 346 347 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) { 348 if (hr->is_humongous()) { 349 oop obj = oop(hr->humongous_start_region()->bottom()); 350 if (hr->is_starts_humongous() && obj->is_gc_marked()) { 351 obj->forward_to(obj); 352 } 353 if (!obj->is_gc_marked()) { 354 free_humongous_region(hr); 355 } 356 } else if (!hr->is_pinned()) { 357 prepare_for_compaction(hr, hr->end()); 358 } 359 return false; 360 }