1 /* 2 * Copyright (c) 2001, 2013, 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/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); 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 Threads::gc_prologue(); 80 81 // Increment the invocation count 82 _total_invocations++; 83 84 // Capture heap size before collection for printing. 85 size_t gch_prev_used = gch->used(); 86 87 // Capture used regions for each generation that will be 88 // subject to collection, so that card table adjustments can 89 // be made intelligently (see clear / invalidate further below). 90 gch->save_used_regions(level); 91 92 allocate_stacks(); 93 94 mark_sweep_phase1(level, clear_all_softrefs); 95 96 mark_sweep_phase2(); 97 98 // Don't add any more derived pointers during phase3 99 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); 100 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); 101 102 mark_sweep_phase3(level); 103 104 mark_sweep_phase4(); 105 106 restore_marks(); 107 108 // Set saved marks for allocation profiler (and other things? -- dld) 109 // (Should this be in general part?) 110 gch->save_marks(); 111 112 deallocate_stacks(); 113 114 // If compaction completely evacuated all generations younger than this 115 // one, then we can clear the card table. Otherwise, we must invalidate 116 // it (consider all cards dirty). In the future, we might consider doing 117 // compaction within generations only, and doing card-table sliding. 118 bool all_empty = true; 119 for (int i = 0; all_empty && i < level; i++) { 120 Generation* g = gch->get_gen(i); 121 all_empty = all_empty && gch->get_gen(i)->used() == 0; 122 } 123 GenRemSet* rs = gch->rem_set(); 124 Generation* old_gen = gch->get_gen(level); 125 // Clear/invalidate below make use of the "prev_used_regions" saved earlier. 126 if (all_empty) { 127 // We've evacuated all generations below us. 128 rs->clear_into_younger(old_gen); 129 } else { 130 // Invalidate the cards corresponding to the currently used 131 // region and clear those corresponding to the evacuated region. 132 rs->invalidate_or_clear(old_gen); 133 } 134 135 Threads::gc_epilogue(); 136 CodeCache::gc_epilogue(); 137 JvmtiExport::gc_epilogue(); 138 139 if (PrintGC && !PrintGCDetails) { 140 gch->print_heap_change(gch_prev_used); 141 } 142 143 // refs processing: clean slate 144 _ref_processor = NULL; 145 146 // Update heap occupancy information which is used as 147 // input to soft ref clearing policy at the next gc. 148 Universe::update_heap_info_at_gc(); 149 150 // Update time of last gc for all generations we collected 151 // (which currently is all the generations in the heap). 152 // We need to use a monotonically non-decreasing time in ms 153 // or we will see time-warp warnings and os::javaTimeMillis() 154 // does not guarantee monotonicity. 155 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 156 gch->update_time_of_last_gc(now); 157 158 gch->trace_heap_after_gc(_gc_tracer); 159 } 160 161 void GenMarkSweep::allocate_stacks() { 162 GenCollectedHeap* gch = GenCollectedHeap::heap(); 163 // Scratch request on behalf of oldest generation; will do no 164 // allocation. 165 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0); 166 167 // $$$ To cut a corner, we'll only use the first scratch block, and then 168 // revert to malloc. 169 if (scratch != NULL) { 170 _preserved_count_max = 171 scratch->num_words * HeapWordSize / sizeof(PreservedMark); 172 } else { 173 _preserved_count_max = 0; 174 } 175 176 _preserved_marks = (PreservedMark*)scratch; 177 _preserved_count = 0; 178 } 179 180 181 void GenMarkSweep::deallocate_stacks() { 182 if (!UseG1GC) { 183 GenCollectedHeap* gch = GenCollectedHeap::heap(); 184 gch->release_scratch(); 185 } 186 187 _preserved_mark_stack.clear(true); 188 _preserved_oop_stack.clear(true); 189 _marking_stack.clear(); 190 _objarray_stack.clear(true); 191 } 192 193 void GenMarkSweep::mark_sweep_phase1(int level, 194 bool clear_all_softrefs) { 195 // Recursively traverse all live objects and mark them 196 GCTraceTime tm("phase 1", PrintGC && Verbose, true, _gc_timer); 197 trace(" 1"); 198 199 GenCollectedHeap* gch = GenCollectedHeap::heap(); 200 201 // Because follow_root_closure is created statically, cannot 202 // use OopsInGenClosure constructor which takes a generation, 203 // as the Universe has not been created when the static constructors 204 // are run. 205 follow_root_closure.set_orig_generation(gch->get_gen(level)); 206 207 // Need new claim bits before marking starts. 208 ClassLoaderDataGraph::clear_claimed_marks(); 209 210 gch->gen_process_strong_roots(level, 211 false, // Younger gens are not roots. 212 true, // activate StrongRootsScope 213 SharedHeap::SO_SystemClasses, 214 &follow_root_closure, 215 &follow_root_closure, 216 &follow_klass_closure); 217 218 // Process reference objects found during marking 219 { 220 ref_processor()->setup_policy(clear_all_softrefs); 221 const ReferenceProcessorStats& stats = 222 ref_processor()->process_discovered_references( 223 &is_alive, &keep_alive, &follow_stack_closure, NULL, _gc_timer); 224 gc_tracer()->report_gc_reference_stats(stats); 225 } 226 227 // This is the point where the entire marking should have completed. 228 assert(_marking_stack.is_empty(), "Marking should have completed"); 229 230 // Unload classes and purge the SystemDictionary. 231 bool purged_class = SystemDictionary::do_unloading(&is_alive); 232 233 // Unload nmethods. 234 CodeCache::do_unloading(&is_alive, purged_class); 235 236 // Prune dead klasses from subklass/sibling/implementor lists. 237 Klass::clean_weak_klass_links(&is_alive); 238 239 // Delete entries for dead interned strings. 240 StringTable::unlink(&is_alive); 241 242 // Clean up unreferenced symbols in symbol table. 243 SymbolTable::unlink(); 244 245 gc_tracer()->report_object_count_after_gc(&is_alive); 246 } 247 248 249 void GenMarkSweep::mark_sweep_phase2() { 250 // Now all live objects are marked, compute the new object addresses. 251 252 // It is imperative that we traverse perm_gen LAST. If dead space is 253 // allowed a range of dead object may get overwritten by a dead int 254 // array. If perm_gen is not traversed last a Klass* may get 255 // overwritten. This is fine since it is dead, but if the class has dead 256 // instances we have to skip them, and in order to find their size we 257 // need the Klass*! 258 // 259 // It is not required that we traverse spaces in the same order in 260 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops 261 // tracking expects us to do so. See comment under phase4. 262 263 GenCollectedHeap* gch = GenCollectedHeap::heap(); 264 265 GCTraceTime tm("phase 2", PrintGC && Verbose, true, _gc_timer); 266 trace("2"); 267 268 gch->prepare_for_compaction(); 269 } 270 271 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure { 272 public: 273 void do_generation(Generation* gen) { 274 gen->adjust_pointers(); 275 } 276 }; 277 278 void GenMarkSweep::mark_sweep_phase3(int level) { 279 GenCollectedHeap* gch = GenCollectedHeap::heap(); 280 281 // Adjust the pointers to reflect the new locations 282 GCTraceTime tm("phase 3", PrintGC && Verbose, true, _gc_timer); 283 trace("3"); 284 285 // Need new claim bits for the pointer adjustment tracing. 286 ClassLoaderDataGraph::clear_claimed_marks(); 287 288 // Because the closure below is created statically, we cannot 289 // use OopsInGenClosure constructor which takes a generation, 290 // as the Universe has not been created when the static constructors 291 // are run. 292 adjust_pointer_closure.set_orig_generation(gch->get_gen(level)); 293 294 gch->gen_process_strong_roots(level, 295 false, // Younger gens are not roots. 296 true, // activate StrongRootsScope 297 SharedHeap::SO_AllClasses | SharedHeap::SO_AllCodeCache, 298 &adjust_pointer_closure, 299 &adjust_pointer_closure, 300 &adjust_klass_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); 331 trace("4"); 332 333 GenCompactClosure blk; 334 gch->generation_iterate(&blk, true); 335 }