1 /* 2 * Copyright (c) 2001, 2014, 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/stringTable.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/shared/gcHeapSummary.hpp" 33 #include "gc_implementation/shared/gcTimer.hpp" 34 #include "gc_implementation/shared/gcTrace.hpp" 35 #include "gc_implementation/shared/gcTraceTime.hpp" 36 #include "gc_interface/collectedHeap.inline.hpp" 37 #include "memory/genCollectedHeap.hpp" 38 #include "memory/genMarkSweep.hpp" 39 #include "memory/genOopClosures.inline.hpp" 40 #include "memory/generation.inline.hpp" 41 #include "memory/modRefBarrierSet.hpp" 42 #include "memory/referencePolicy.hpp" 43 #include "memory/space.hpp" 44 #include "oops/instanceRefKlass.hpp" 45 #include "oops/oop.inline.hpp" 46 #include "prims/jvmtiExport.hpp" 47 #include "runtime/fprofiler.hpp" 48 #include "runtime/handles.inline.hpp" 49 #include "runtime/synchronizer.hpp" 50 #include "runtime/thread.inline.hpp" 51 #include "runtime/vmThread.hpp" 52 #include "utilities/copy.hpp" 53 #include "utilities/events.hpp" 54 55 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp, bool clear_all_softrefs) { 56 guarantee(level == 1, "We always collect both old and young."); 57 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 58 59 GenCollectedHeap* gch = GenCollectedHeap::heap(); 60 #ifdef ASSERT 61 if (gch->collector_policy()->should_clear_all_soft_refs()) { 62 assert(clear_all_softrefs, "Policy should have been checked earlier"); 63 } 64 #endif 65 66 // hook up weak ref data so it can be used during Mark-Sweep 67 assert(ref_processor() == NULL, "no stomping"); 68 assert(rp != NULL, "should be non-NULL"); 69 _ref_processor = rp; 70 rp->setup_policy(clear_all_softrefs); 71 72 GCTraceTime t1(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, _gc_tracer->gc_id()); 73 74 gch->trace_heap_before_gc(_gc_tracer); 75 76 // When collecting the permanent generation Method*s may be moving, 77 // so we either have to flush all bcp data or convert it into bci. 78 CodeCache::gc_prologue(); 79 80 // Increment the invocation count 81 _total_invocations++; 82 83 // Capture heap size before collection for printing. 84 size_t gch_prev_used = gch->used(); 85 86 // Capture used regions for each generation that will be 87 // subject to collection, so that card table adjustments can 88 // be made intelligently (see clear / invalidate further below). 89 gch->save_used_regions(level); 90 91 allocate_stacks(); 92 93 mark_sweep_phase1(level, clear_all_softrefs); 94 95 mark_sweep_phase2(); 96 97 // Don't add any more derived pointers during phase3 98 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); 99 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 100 101 mark_sweep_phase3(level); 102 103 mark_sweep_phase4(); 104 105 restore_marks(); 106 107 // Set saved marks for allocation profiler (and other things? -- dld) 108 // (Should this be in general part?) 109 gch->save_marks(); 110 111 deallocate_stacks(); 112 113 // If compaction completely evacuated all generations younger than this 114 // one, then we can clear the card table. Otherwise, we must invalidate 115 // it (consider all cards dirty). In the future, we might consider doing 116 // compaction within generations only, and doing card-table sliding. 117 bool all_empty = true; 118 for (int i = 0; all_empty && i < level; i++) { 119 Generation* g = gch->get_gen(i); 120 all_empty = all_empty && gch->get_gen(i)->used() == 0; 121 } 122 GenRemSet* rs = gch->rem_set(); 123 Generation* old_gen = gch->get_gen(level); 124 // Clear/invalidate below make use of the "prev_used_regions" saved earlier. 125 if (all_empty) { 126 // We've evacuated all generations below us. 127 rs->clear_into_younger(old_gen); 128 } else { 129 // Invalidate the cards corresponding to the currently used 130 // region and clear those corresponding to the evacuated region. 131 rs->invalidate_or_clear(old_gen); 132 } 133 134 CodeCache::gc_epilogue(); 135 JvmtiExport::gc_epilogue(); 136 137 if (PrintGC && !PrintGCDetails) { 138 gch->print_heap_change(gch_prev_used); 139 } 140 141 // refs processing: clean slate 142 _ref_processor = NULL; 143 144 // Update heap occupancy information which is used as 145 // input to soft ref clearing policy at the next gc. 146 Universe::update_heap_info_at_gc(); 147 148 // Update time of last gc for all generations we collected 149 // (which currently is all the generations in the heap). 150 // We need to use a monotonically non-decreasing time in ms 151 // or we will see time-warp warnings and os::javaTimeMillis() 152 // does not guarantee monotonicity. 153 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 154 gch->update_time_of_last_gc(now); 155 156 gch->trace_heap_after_gc(_gc_tracer); 157 } 158 159 void GenMarkSweep::allocate_stacks() { 160 GenCollectedHeap* gch = GenCollectedHeap::heap(); 161 // Scratch request on behalf of oldest generation; will do no 162 // allocation. 163 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0); 164 165 // $$$ To cut a corner, we'll only use the first scratch block, and then 166 // revert to malloc. 167 if (scratch != NULL) { 168 _preserved_count_max = 169 scratch->num_words * HeapWordSize / sizeof(PreservedMark); 170 } else { 171 _preserved_count_max = 0; 172 } 173 174 _preserved_marks = (PreservedMark*)scratch; 175 _preserved_count = 0; 176 } 177 178 179 void GenMarkSweep::deallocate_stacks() { 180 if (!UseG1GC) { 181 GenCollectedHeap* gch = GenCollectedHeap::heap(); 182 gch->release_scratch(); 183 } 184 185 _preserved_mark_stack.clear(true); 186 _preserved_oop_stack.clear(true); 187 _marking_stack.clear(); 188 _objarray_stack.clear(true); 189 } 190 191 void GenMarkSweep::mark_sweep_phase1(int level, 192 bool clear_all_softrefs) { 193 // Recursively traverse all live objects and mark them 194 GCTraceTime tm("phase 1", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 195 trace(" 1"); 196 197 GenCollectedHeap* gch = GenCollectedHeap::heap(); 198 199 // Because follow_root_closure is created statically, cannot 200 // use OopsInGenClosure constructor which takes a generation, 201 // as the Universe has not been created when the static constructors 202 // are run. 203 follow_root_closure.set_orig_generation(gch->get_gen(level)); 204 205 // Need new claim bits before marking starts. 206 ClassLoaderDataGraph::clear_claimed_marks(); 207 208 gch->gen_process_roots(level, 209 false, // Younger gens are not roots. 210 true, // activate StrongRootsScope 211 SharedHeap::SO_None, 212 GenCollectedHeap::StrongRootsOnly, 213 &follow_root_closure, 214 &follow_root_closure, 215 &follow_cld_closure); 216 217 // Process reference objects found during marking 218 { 219 ref_processor()->setup_policy(clear_all_softrefs); 220 const ReferenceProcessorStats& stats = 221 ref_processor()->process_discovered_references( 222 &is_alive, &keep_alive, &follow_stack_closure, NULL, _gc_timer, _gc_tracer->gc_id()); 223 gc_tracer()->report_gc_reference_stats(stats); 224 } 225 226 // This is the point where the entire marking should have completed. 227 assert(_marking_stack.is_empty(), "Marking should have completed"); 228 229 // Unload classes and purge the SystemDictionary. 230 bool purged_class = SystemDictionary::do_unloading(&is_alive); 231 232 // Unload nmethods. 233 CodeCache::do_unloading(&is_alive, purged_class); 234 235 // Prune dead klasses from subklass/sibling/implementor lists. 236 Klass::clean_weak_klass_links(&is_alive); 237 238 // Delete entries for dead interned strings. 239 StringTable::unlink(&is_alive); 240 241 // Clean up unreferenced symbols in symbol table. 242 SymbolTable::unlink(); 243 244 gc_tracer()->report_object_count_after_gc(&is_alive); 245 } 246 247 248 void GenMarkSweep::mark_sweep_phase2() { 249 // Now all live objects are marked, compute the new object addresses. 250 251 // It is imperative that we traverse perm_gen LAST. If dead space is 252 // allowed a range of dead object may get overwritten by a dead int 253 // array. If perm_gen is not traversed last a Klass* may get 254 // overwritten. This is fine since it is dead, but if the class has dead 255 // instances we have to skip them, and in order to find their size we 256 // need the Klass*! 257 // 258 // It is not required that we traverse spaces in the same order in 259 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 260 // tracking expects us to do so. See comment under phase4. 261 262 GenCollectedHeap* gch = GenCollectedHeap::heap(); 263 264 GCTraceTime tm("phase 2", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 265 trace("2"); 266 267 gch->prepare_for_compaction(); 268 } 269 270 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure { 271 public: 272 void do_generation(Generation* gen) { 273 gen->adjust_pointers(); 274 } 275 }; 276 277 void GenMarkSweep::mark_sweep_phase3(int level) { 278 GenCollectedHeap* gch = GenCollectedHeap::heap(); 279 280 // Adjust the pointers to reflect the new locations 281 GCTraceTime tm("phase 3", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 282 trace("3"); 283 284 // Need new claim bits for the pointer adjustment tracing. 285 ClassLoaderDataGraph::clear_claimed_marks(); 286 287 // Because the closure below is created statically, we cannot 288 // use OopsInGenClosure constructor which takes a generation, 289 // as the Universe has not been created when the static constructors 290 // are run. 291 adjust_pointer_closure.set_orig_generation(gch->get_gen(level)); 292 293 gch->gen_process_roots(level, 294 false, // Younger gens are not roots. 295 true, // activate StrongRootsScope 296 SharedHeap::SO_AllCodeCache, 297 GenCollectedHeap::StrongAndWeakRoots, 298 &adjust_pointer_closure, 299 &adjust_pointer_closure, 300 &adjust_cld_closure); 301 302 gch->gen_process_weak_roots(&adjust_pointer_closure); 303 304 adjust_marks(); 305 GenAdjustPointersClosure blk; 306 gch->generation_iterate(&blk, true); 307 } 308 309 class GenCompactClosure: public GenCollectedHeap::GenClosure { 310 public: 311 void do_generation(Generation* gen) { 312 gen->compact(); 313 } 314 }; 315 316 void GenMarkSweep::mark_sweep_phase4() { 317 // All pointers are now adjusted, move objects accordingly 318 319 // It is imperative that we traverse perm_gen first in phase4. All 320 // classes must be allocated earlier than their instances, and traversing 321 // perm_gen first makes sure that all Klass*s have moved to their new 322 // location before any instance does a dispatch through it's klass! 323 324 // The ValidateMarkSweep live oops tracking expects us to traverse spaces 325 // in the same order in phase2, phase3 and phase4. We don't quite do that 326 // here (perm_gen first rather than last), so we tell the validate code 327 // to use a higher index (saved from phase2) when verifying perm_gen. 328 GenCollectedHeap* gch = GenCollectedHeap::heap(); 329 330 GCTraceTime tm("phase 4", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id()); 331 trace("4"); 332 333 GenCompactClosure blk; 334 gch->generation_iterate(&blk, true); 335 }