1 /* 2 * Copyright (c) 2001, 2010, 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/g1MarkSweep.hpp" 33 #include "memory/gcLocker.hpp" 34 #include "memory/genCollectedHeap.hpp" 35 #include "memory/modRefBarrierSet.hpp" 36 #include "memory/referencePolicy.hpp" 37 #include "memory/space.hpp" 38 #include "oops/instanceRefKlass.hpp" 39 #include "oops/oop.inline.hpp" 40 #include "prims/jvmtiExport.hpp" 41 #include "runtime/aprofiler.hpp" 42 #include "runtime/biasedLocking.hpp" 43 #include "runtime/fprofiler.hpp" 44 #include "runtime/synchronizer.hpp" 45 #include "runtime/thread.hpp" 46 #include "runtime/vmThread.hpp" 47 #include "utilities/copy.hpp" 48 #include "utilities/events.hpp" 49 50 class HeapRegion; 51 52 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, 53 bool clear_all_softrefs) { 54 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 55 56 SharedHeap* sh = SharedHeap::heap(); 57 #ifdef ASSERT 58 if (sh->collector_policy()->should_clear_all_soft_refs()) { 59 assert(clear_all_softrefs, "Policy should have been checked earler"); 60 } 61 #endif 62 // hook up weak ref data so it can be used during Mark-Sweep 63 assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); 64 assert(rp != NULL, "should be non-NULL"); 65 GenMarkSweep::_ref_processor = rp; 66 rp->setup_policy(clear_all_softrefs); 67 68 // When collecting the permanent generation methodOops may be moving, 69 // so we either have to flush all bcp data or convert it into bci. 70 CodeCache::gc_prologue(); 71 Threads::gc_prologue(); 72 73 // Increment the invocation count for the permanent generation, since it is 74 // implicitly collected whenever we do a full mark sweep collection. 75 sh->perm_gen()->stat_record()->invocations++; 76 77 bool marked_for_unloading = false; 78 79 allocate_stacks(); 80 81 // We should save the marks of the currently locked biased monitors. 82 // The marking doesn't preserve the marks of biased objects. 83 BiasedLocking::preserve_marks(); 84 85 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); 86 87 if (VerifyDuringGC) { 88 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 89 g1h->checkConcurrentMark(); 90 } 91 92 mark_sweep_phase2(); 93 94 // Don't add any more derived pointers during phase3 95 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 96 97 mark_sweep_phase3(); 98 99 mark_sweep_phase4(); 100 101 GenMarkSweep::restore_marks(); 102 BiasedLocking::restore_marks(); 103 GenMarkSweep::deallocate_stacks(); 104 105 // We must invalidate the perm-gen rs, so that it gets rebuilt. 106 GenRemSet* rs = sh->rem_set(); 107 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/); 108 109 // "free at last gc" is calculated from these. 110 // CHF: cheating for now!!! 111 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity()); 112 // Universe::set_heap_used_at_last_gc(Universe::heap()->used()); 113 114 Threads::gc_epilogue(); 115 CodeCache::gc_epilogue(); 116 117 // refs processing: clean slate 118 GenMarkSweep::_ref_processor = NULL; 119 } 120 121 122 void G1MarkSweep::allocate_stacks() { 123 GenMarkSweep::_preserved_count_max = 0; 124 GenMarkSweep::_preserved_marks = NULL; 125 GenMarkSweep::_preserved_count = 0; 126 } 127 128 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, 129 bool clear_all_softrefs) { 130 // Recursively traverse all live objects and mark them 131 EventMark m("1 mark object"); 132 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty); 133 GenMarkSweep::trace(" 1"); 134 135 SharedHeap* sh = SharedHeap::heap(); 136 137 sh->process_strong_roots(true, // activeate StrongRootsScope 138 true, // Collecting permanent generation. 139 SharedHeap::SO_SystemClasses, 140 &GenMarkSweep::follow_root_closure, 141 &GenMarkSweep::follow_code_root_closure, 142 &GenMarkSweep::follow_root_closure); 143 144 // Process reference objects found during marking 145 ReferenceProcessor* rp = GenMarkSweep::ref_processor(); 146 rp->setup_policy(clear_all_softrefs); 147 rp->process_discovered_references(&GenMarkSweep::is_alive, 148 &GenMarkSweep::keep_alive, 149 &GenMarkSweep::follow_stack_closure, 150 NULL); 151 152 // Follow system dictionary roots and unload classes 153 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); 154 assert(GenMarkSweep::_marking_stack.is_empty(), 155 "stack should be empty by now"); 156 157 // Follow code cache roots (has to be done after system dictionary, 158 // assumes all live klasses are marked) 159 CodeCache::do_unloading(&GenMarkSweep::is_alive, 160 &GenMarkSweep::keep_alive, 161 purged_class); 162 GenMarkSweep::follow_stack(); 163 164 // Update subklass/sibling/implementor links of live klasses 165 GenMarkSweep::follow_weak_klass_links(); 166 assert(GenMarkSweep::_marking_stack.is_empty(), 167 "stack should be empty by now"); 168 169 // Visit memoized MDO's and clear any unmarked weak refs 170 GenMarkSweep::follow_mdo_weak_refs(); 171 assert(GenMarkSweep::_marking_stack.is_empty(), "just drained"); 172 173 174 // Visit symbol and interned string tables and delete unmarked oops 175 SymbolTable::unlink(&GenMarkSweep::is_alive); 176 StringTable::unlink(&GenMarkSweep::is_alive); 177 178 assert(GenMarkSweep::_marking_stack.is_empty(), 179 "stack should be empty by now"); 180 } 181 182 class G1PrepareCompactClosure: public HeapRegionClosure { 183 ModRefBarrierSet* _mrbs; 184 CompactPoint _cp; 185 186 void free_humongous_region(HeapRegion* hr) { 187 HeapWord* bot = hr->bottom(); 188 HeapWord* end = hr->end(); 189 assert(hr->startsHumongous(), 190 "Only the start of a humongous region should be freed."); 191 G1CollectedHeap::heap()->free_region(hr); 192 hr->prepare_for_compaction(&_cp); 193 // Also clear the part of the card table that will be unused after 194 // compaction. 195 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end())); 196 } 197 198 public: 199 G1PrepareCompactClosure(CompactibleSpace* cs) : 200 _cp(NULL, cs, cs->initialize_threshold()), 201 _mrbs(G1CollectedHeap::heap()->mr_bs()) 202 {} 203 bool doHeapRegion(HeapRegion* hr) { 204 if (hr->isHumongous()) { 205 if (hr->startsHumongous()) { 206 oop obj = oop(hr->bottom()); 207 if (obj->is_gc_marked()) { 208 obj->forward_to(obj); 209 } else { 210 free_humongous_region(hr); 211 } 212 } else { 213 assert(hr->continuesHumongous(), "Invalid humongous."); 214 } 215 } else { 216 hr->prepare_for_compaction(&_cp); 217 // Also clear the part of the card table that will be unused after 218 // compaction. 219 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end())); 220 } 221 return false; 222 } 223 }; 224 225 // Finds the first HeapRegion. 226 class FindFirstRegionClosure: public HeapRegionClosure { 227 HeapRegion* _a_region; 228 public: 229 FindFirstRegionClosure() : _a_region(NULL) {} 230 bool doHeapRegion(HeapRegion* r) { 231 _a_region = r; 232 return true; 233 } 234 HeapRegion* result() { return _a_region; } 235 }; 236 237 void G1MarkSweep::mark_sweep_phase2() { 238 // Now all live objects are marked, compute the new object addresses. 239 240 // It is imperative that we traverse perm_gen LAST. If dead space is 241 // allowed a range of dead object may get overwritten by a dead int 242 // array. If perm_gen is not traversed last a klassOop may get 243 // overwritten. This is fine since it is dead, but if the class has dead 244 // instances we have to skip them, and in order to find their size we 245 // need the klassOop! 246 // 247 // It is not required that we traverse spaces in the same order in 248 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 249 // tracking expects us to do so. See comment under phase4. 250 251 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 252 Generation* pg = g1h->perm_gen(); 253 254 EventMark m("2 compute new addresses"); 255 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty); 256 GenMarkSweep::trace("2"); 257 258 FindFirstRegionClosure cl; 259 g1h->heap_region_iterate(&cl); 260 HeapRegion *r = cl.result(); 261 CompactibleSpace* sp = r; 262 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) { 263 sp = r->next_compaction_space(); 264 } 265 266 G1PrepareCompactClosure blk(sp); 267 g1h->heap_region_iterate(&blk); 268 269 CompactPoint perm_cp(pg, NULL, NULL); 270 pg->prepare_for_compaction(&perm_cp); 271 } 272 273 class G1AdjustPointersClosure: public HeapRegionClosure { 274 public: 275 bool doHeapRegion(HeapRegion* r) { 276 if (r->isHumongous()) { 277 if (r->startsHumongous()) { 278 // We must adjust the pointers on the single H object. 279 oop obj = oop(r->bottom()); 280 debug_only(GenMarkSweep::track_interior_pointers(obj)); 281 // point all the oops to the new location 282 obj->adjust_pointers(); 283 debug_only(GenMarkSweep::check_interior_pointers()); 284 } 285 } else { 286 // This really ought to be "as_CompactibleSpace"... 287 r->adjust_pointers(); 288 } 289 return false; 290 } 291 }; 292 293 void G1MarkSweep::mark_sweep_phase3() { 294 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 295 Generation* pg = g1h->perm_gen(); 296 297 // Adjust the pointers to reflect the new locations 298 EventMark m("3 adjust pointers"); 299 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty); 300 GenMarkSweep::trace("3"); 301 302 SharedHeap* sh = SharedHeap::heap(); 303 304 sh->process_strong_roots(true, // activate StrongRootsScope 305 true, // Collecting permanent generation. 306 SharedHeap::SO_AllClasses, 307 &GenMarkSweep::adjust_root_pointer_closure, 308 NULL, // do not touch code cache here 309 &GenMarkSweep::adjust_pointer_closure); 310 311 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure); 312 313 // Now adjust pointers in remaining weak roots. (All of which should 314 // have been cleared if they pointed to non-surviving objects.) 315 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure, 316 &GenMarkSweep::adjust_pointer_closure); 317 318 GenMarkSweep::adjust_marks(); 319 320 G1AdjustPointersClosure blk; 321 g1h->heap_region_iterate(&blk); 322 pg->adjust_pointers(); 323 } 324 325 class G1SpaceCompactClosure: public HeapRegionClosure { 326 public: 327 G1SpaceCompactClosure() {} 328 329 bool doHeapRegion(HeapRegion* hr) { 330 if (hr->isHumongous()) { 331 if (hr->startsHumongous()) { 332 oop obj = oop(hr->bottom()); 333 if (obj->is_gc_marked()) { 334 obj->init_mark(); 335 } else { 336 assert(hr->is_empty(), "Should have been cleared in phase 2."); 337 } 338 hr->reset_during_compaction(); 339 } 340 } else { 341 hr->compact(); 342 } 343 return false; 344 } 345 }; 346 347 void G1MarkSweep::mark_sweep_phase4() { 348 // All pointers are now adjusted, move objects accordingly 349 350 // It is imperative that we traverse perm_gen first in phase4. All 351 // classes must be allocated earlier than their instances, and traversing 352 // perm_gen first makes sure that all klassOops have moved to their new 353 // location before any instance does a dispatch through it's klass! 354 355 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 356 // in the same order in phase2, phase3 and phase4. We don't quite do that 357 // here (perm_gen first rather than last), so we tell the validate code 358 // to use a higher index (saved from phase2) when verifying perm_gen. 359 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 360 Generation* pg = g1h->perm_gen(); 361 362 EventMark m("4 compact heap"); 363 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty); 364 GenMarkSweep::trace("4"); 365 366 pg->compact(); 367 368 G1SpaceCompactClosure blk; 369 g1h->heap_region_iterate(&blk); 370 371 } 372 373 // Local Variables: *** 374 // c-indentation-style: gnu *** 375 // End: ***