ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1 | // Copyright 2006-2008 the V8 project authors. All rights reserved. |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 2 | // Redistribution and use in source and binary forms, with or without |
| 3 | // modification, are permitted provided that the following conditions are |
| 4 | // met: |
| 5 | // |
| 6 | // * Redistributions of source code must retain the above copyright |
| 7 | // notice, this list of conditions and the following disclaimer. |
| 8 | // * Redistributions in binary form must reproduce the above |
| 9 | // copyright notice, this list of conditions and the following |
| 10 | // disclaimer in the documentation and/or other materials provided |
| 11 | // with the distribution. |
| 12 | // * Neither the name of Google Inc. nor the names of its |
| 13 | // contributors may be used to endorse or promote products derived |
| 14 | // from this software without specific prior written permission. |
| 15 | // |
| 16 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | |
| 28 | #include "v8.h" |
| 29 | |
| 30 | #include "execution.h" |
| 31 | #include "global-handles.h" |
| 32 | #include "ic-inl.h" |
| 33 | #include "mark-compact.h" |
| 34 | #include "stub-cache.h" |
| 35 | |
| 36 | namespace v8 { namespace internal { |
| 37 | |
ager@chromium.org | ddb913d | 2009-01-27 10:01:48 +0000 | [diff] [blame] | 38 | // ------------------------------------------------------------------------- |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 39 | // MarkCompactCollector |
| 40 | |
| 41 | bool MarkCompactCollector::compacting_collection_ = false; |
| 42 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 43 | int MarkCompactCollector::previous_marked_count_ = 0; |
| 44 | GCTracer* MarkCompactCollector::tracer_ = NULL; |
| 45 | |
| 46 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 47 | #ifdef DEBUG |
| 48 | MarkCompactCollector::CollectorState MarkCompactCollector::state_ = IDLE; |
| 49 | |
| 50 | // Counters used for debugging the marking phase of mark-compact or mark-sweep |
| 51 | // collection. |
| 52 | int MarkCompactCollector::live_bytes_ = 0; |
| 53 | int MarkCompactCollector::live_young_objects_ = 0; |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 54 | int MarkCompactCollector::live_old_data_objects_ = 0; |
| 55 | int MarkCompactCollector::live_old_pointer_objects_ = 0; |
| 56 | int MarkCompactCollector::live_code_objects_ = 0; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 57 | int MarkCompactCollector::live_map_objects_ = 0; |
| 58 | int MarkCompactCollector::live_lo_objects_ = 0; |
| 59 | #endif |
| 60 | |
kasperl@chromium.org | 061ef74 | 2009-02-27 12:16:20 +0000 | [diff] [blame] | 61 | void MarkCompactCollector::CollectGarbage() { |
| 62 | // Make sure that Prepare() has been called. The individual steps below will |
| 63 | // update the state as they proceed. |
| 64 | ASSERT(state_ == PREPARE_GC); |
| 65 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 66 | // Prepare has selected whether to compact the old generation or not. |
| 67 | // Tell the tracer. |
| 68 | if (IsCompacting()) tracer_->set_is_compacting(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 69 | |
| 70 | MarkLiveObjects(); |
| 71 | |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 72 | if (FLAG_collect_maps) ClearNonLiveTransitions(); |
| 73 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 74 | SweepLargeObjectSpace(); |
| 75 | |
| 76 | if (compacting_collection_) { |
| 77 | EncodeForwardingAddresses(); |
| 78 | |
| 79 | UpdatePointers(); |
| 80 | |
| 81 | RelocateObjects(); |
| 82 | |
| 83 | RebuildRSets(); |
| 84 | |
| 85 | } else { |
| 86 | SweepSpaces(); |
| 87 | } |
| 88 | |
| 89 | Finish(); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 90 | |
| 91 | // Save the count of marked objects remaining after the collection and |
| 92 | // null out the GC tracer. |
| 93 | previous_marked_count_ = tracer_->marked_count(); |
| 94 | ASSERT(previous_marked_count_ == 0); |
| 95 | tracer_ = NULL; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 96 | } |
| 97 | |
| 98 | |
kasperl@chromium.org | 061ef74 | 2009-02-27 12:16:20 +0000 | [diff] [blame] | 99 | void MarkCompactCollector::Prepare(GCTracer* tracer) { |
| 100 | // Rather than passing the tracer around we stash it in a static member |
| 101 | // variable. |
| 102 | tracer_ = tracer; |
| 103 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 104 | static const int kFragmentationLimit = 50; // Percent. |
| 105 | #ifdef DEBUG |
| 106 | ASSERT(state_ == IDLE); |
| 107 | state_ = PREPARE_GC; |
| 108 | #endif |
| 109 | ASSERT(!FLAG_always_compact || !FLAG_never_compact); |
| 110 | |
| 111 | compacting_collection_ = FLAG_always_compact; |
| 112 | |
| 113 | // We compact the old generation if it gets too fragmented (ie, we could |
| 114 | // recover an expected amount of space by reclaiming the waste and free |
| 115 | // list blocks). We always compact when the flag --gc-global is true |
| 116 | // because objects do not get promoted out of new space on non-compacting |
| 117 | // GCs. |
| 118 | if (!compacting_collection_) { |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 119 | int old_gen_recoverable = 0; |
| 120 | int old_gen_used = 0; |
| 121 | |
| 122 | OldSpaces spaces; |
| 123 | while (OldSpace* space = spaces.next()) { |
| 124 | old_gen_recoverable += space->Waste() + space->AvailableFree(); |
| 125 | old_gen_used += space->Size(); |
| 126 | } |
| 127 | int old_gen_fragmentation = |
| 128 | static_cast<int>((old_gen_recoverable * 100.0) / old_gen_used); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 129 | if (old_gen_fragmentation > kFragmentationLimit) { |
| 130 | compacting_collection_ = true; |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | if (FLAG_never_compact) compacting_collection_ = false; |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 135 | if (FLAG_collect_maps) CreateBackPointers(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 136 | |
| 137 | #ifdef DEBUG |
| 138 | if (compacting_collection_) { |
| 139 | // We will write bookkeeping information to the remembered set area |
| 140 | // starting now. |
| 141 | Page::set_rset_state(Page::NOT_IN_USE); |
| 142 | } |
| 143 | #endif |
| 144 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 145 | PagedSpaces spaces; |
| 146 | while (PagedSpace* space = spaces.next()) { |
| 147 | space->PrepareForMarkCompact(compacting_collection_); |
| 148 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 149 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 150 | #ifdef DEBUG |
| 151 | live_bytes_ = 0; |
| 152 | live_young_objects_ = 0; |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 153 | live_old_pointer_objects_ = 0; |
| 154 | live_old_data_objects_ = 0; |
| 155 | live_code_objects_ = 0; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 156 | live_map_objects_ = 0; |
| 157 | live_lo_objects_ = 0; |
| 158 | #endif |
| 159 | } |
| 160 | |
| 161 | |
| 162 | void MarkCompactCollector::Finish() { |
| 163 | #ifdef DEBUG |
| 164 | ASSERT(state_ == SWEEP_SPACES || state_ == REBUILD_RSETS); |
| 165 | state_ = IDLE; |
| 166 | #endif |
| 167 | // The stub cache is not traversed during GC; clear the cache to |
| 168 | // force lazy re-initialization of it. This must be done after the |
| 169 | // GC, because it relies on the new address of certain old space |
| 170 | // objects (empty string, illegal builtin). |
| 171 | StubCache::Clear(); |
| 172 | } |
| 173 | |
| 174 | |
ager@chromium.org | ddb913d | 2009-01-27 10:01:48 +0000 | [diff] [blame] | 175 | // ------------------------------------------------------------------------- |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 176 | // Phase 1: tracing and marking live objects. |
| 177 | // before: all objects are in normal state. |
| 178 | // after: a live object's map pointer is marked as '00'. |
| 179 | |
| 180 | // Marking all live objects in the heap as part of mark-sweep or mark-compact |
| 181 | // collection. Before marking, all objects are in their normal state. After |
| 182 | // marking, live objects' map pointers are marked indicating that the object |
| 183 | // has been found reachable. |
| 184 | // |
| 185 | // The marking algorithm is a (mostly) depth-first (because of possible stack |
| 186 | // overflow) traversal of the graph of objects reachable from the roots. It |
| 187 | // uses an explicit stack of pointers rather than recursion. The young |
| 188 | // generation's inactive ('from') space is used as a marking stack. The |
| 189 | // objects in the marking stack are the ones that have been reached and marked |
| 190 | // but their children have not yet been visited. |
| 191 | // |
| 192 | // The marking stack can overflow during traversal. In that case, we set an |
| 193 | // overflow flag. When the overflow flag is set, we continue marking objects |
| 194 | // reachable from the objects on the marking stack, but no longer push them on |
| 195 | // the marking stack. Instead, we mark them as both marked and overflowed. |
| 196 | // When the stack is in the overflowed state, objects marked as overflowed |
| 197 | // have been reached and marked but their children have not been visited yet. |
| 198 | // After emptying the marking stack, we clear the overflow flag and traverse |
| 199 | // the heap looking for objects marked as overflowed, push them on the stack, |
| 200 | // and continue with marking. This process repeats until all reachable |
| 201 | // objects have been marked. |
| 202 | |
| 203 | static MarkingStack marking_stack; |
| 204 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 205 | |
kasperl@chromium.org | 5a8ca6c | 2008-10-23 13:57:19 +0000 | [diff] [blame] | 206 | static inline HeapObject* ShortCircuitConsString(Object** p) { |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 207 | // Optimization: If the heap object pointed to by p is a non-symbol |
| 208 | // cons string whose right substring is Heap::empty_string, update |
| 209 | // it in place to its left substring. Return the updated value. |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 210 | // |
| 211 | // Here we assume that if we change *p, we replace it with a heap object |
| 212 | // (ie, the left substring of a cons string is always a heap object). |
| 213 | // |
| 214 | // The check performed is: |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 215 | // object->IsConsString() && !object->IsSymbol() && |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 216 | // (ConsString::cast(object)->second() == Heap::empty_string()) |
| 217 | // except the maps for the object and its possible substrings might be |
| 218 | // marked. |
| 219 | HeapObject* object = HeapObject::cast(*p); |
| 220 | MapWord map_word = object->map_word(); |
| 221 | map_word.ClearMark(); |
| 222 | InstanceType type = map_word.ToMap()->instance_type(); |
kasperl@chromium.org | d1e3e72 | 2009-04-14 13:38:25 +0000 | [diff] [blame] | 223 | if ((type & kShortcutTypeMask) != kShortcutTypeTag) return object; |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 224 | |
ager@chromium.org | bb29dc9 | 2009-03-24 13:25:23 +0000 | [diff] [blame] | 225 | Object* second = reinterpret_cast<ConsString*>(object)->unchecked_second(); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 226 | if (reinterpret_cast<String*>(second) != Heap::empty_string()) return object; |
| 227 | |
| 228 | // Since we don't have the object's start, it is impossible to update the |
| 229 | // remembered set. Therefore, we only replace the string with its left |
| 230 | // substring when the remembered set does not change. |
ager@chromium.org | bb29dc9 | 2009-03-24 13:25:23 +0000 | [diff] [blame] | 231 | Object* first = reinterpret_cast<ConsString*>(object)->unchecked_first(); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 232 | if (!Heap::InNewSpace(object) && Heap::InNewSpace(first)) return object; |
| 233 | |
| 234 | *p = first; |
| 235 | return HeapObject::cast(first); |
| 236 | } |
| 237 | |
| 238 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 239 | // Helper class for marking pointers in HeapObjects. |
| 240 | class MarkingVisitor : public ObjectVisitor { |
| 241 | public: |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 242 | void VisitPointer(Object** p) { |
| 243 | MarkObjectByPointer(p); |
| 244 | } |
| 245 | |
| 246 | void VisitPointers(Object** start, Object** end) { |
| 247 | // Mark all objects pointed to in [start, end). |
| 248 | const int kMinRangeForMarkingRecursion = 64; |
| 249 | if (end - start >= kMinRangeForMarkingRecursion) { |
| 250 | if (VisitUnmarkedObjects(start, end)) return; |
| 251 | // We are close to a stack overflow, so just mark the objects. |
| 252 | } |
| 253 | for (Object** p = start; p < end; p++) MarkObjectByPointer(p); |
| 254 | } |
| 255 | |
| 256 | void BeginCodeIteration(Code* code) { |
| 257 | // When iterating over a code object during marking |
| 258 | // ic targets are derived pointers. |
| 259 | ASSERT(code->ic_flag() == Code::IC_TARGET_IS_ADDRESS); |
| 260 | } |
| 261 | |
| 262 | void EndCodeIteration(Code* code) { |
| 263 | // If this is a compacting collection, set ic targets |
| 264 | // are pointing to object headers. |
| 265 | if (IsCompacting()) code->set_ic_flag(Code::IC_TARGET_IS_OBJECT); |
| 266 | } |
| 267 | |
| 268 | void VisitCodeTarget(RelocInfo* rinfo) { |
ager@chromium.org | 236ad96 | 2008-09-25 09:45:57 +0000 | [diff] [blame] | 269 | ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode())); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 270 | Code* code = CodeFromDerivedPointer(rinfo->target_address()); |
| 271 | if (FLAG_cleanup_ics_at_gc && code->is_inline_cache_stub()) { |
| 272 | IC::Clear(rinfo->pc()); |
| 273 | // Please note targets for cleared inline cached do not have to be |
| 274 | // marked since they are contained in Heap::non_monomorphic_cache(). |
| 275 | } else { |
| 276 | MarkCompactCollector::MarkObject(code); |
| 277 | } |
| 278 | if (IsCompacting()) { |
| 279 | // When compacting we convert the target to a real object pointer. |
| 280 | code = CodeFromDerivedPointer(rinfo->target_address()); |
| 281 | rinfo->set_target_object(code); |
| 282 | } |
| 283 | } |
| 284 | |
| 285 | void VisitDebugTarget(RelocInfo* rinfo) { |
ager@chromium.org | 236ad96 | 2008-09-25 09:45:57 +0000 | [diff] [blame] | 286 | ASSERT(RelocInfo::IsJSReturn(rinfo->rmode()) && |
iposva@chromium.org | 245aa85 | 2009-02-10 00:49:54 +0000 | [diff] [blame] | 287 | rinfo->IsCallInstruction()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 288 | HeapObject* code = CodeFromDerivedPointer(rinfo->call_address()); |
| 289 | MarkCompactCollector::MarkObject(code); |
| 290 | // When compacting we convert the call to a real object pointer. |
| 291 | if (IsCompacting()) rinfo->set_call_object(code); |
| 292 | } |
| 293 | |
| 294 | private: |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 295 | // Mark object pointed to by p. |
| 296 | void MarkObjectByPointer(Object** p) { |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 297 | if (!(*p)->IsHeapObject()) return; |
| 298 | HeapObject* object = ShortCircuitConsString(p); |
| 299 | MarkCompactCollector::MarkObject(object); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 300 | } |
| 301 | |
| 302 | // Tells whether the mark sweep collection will perform compaction. |
| 303 | bool IsCompacting() { return MarkCompactCollector::IsCompacting(); } |
| 304 | |
| 305 | // Retrieves the Code pointer from derived code entry. |
| 306 | Code* CodeFromDerivedPointer(Address addr) { |
| 307 | ASSERT(addr != NULL); |
| 308 | return reinterpret_cast<Code*>( |
| 309 | HeapObject::FromAddress(addr - Code::kHeaderSize)); |
| 310 | } |
| 311 | |
| 312 | // Visit an unmarked object. |
| 313 | void VisitUnmarkedObject(HeapObject* obj) { |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 314 | #ifdef DEBUG |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 315 | ASSERT(Heap::Contains(obj)); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 316 | ASSERT(!obj->IsMarked()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 317 | #endif |
| 318 | Map* map = obj->map(); |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 319 | MarkCompactCollector::SetMark(obj); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 320 | // Mark the map pointer and the body. |
| 321 | MarkCompactCollector::MarkObject(map); |
| 322 | obj->IterateBody(map->instance_type(), obj->SizeFromMap(map), this); |
| 323 | } |
| 324 | |
| 325 | // Visit all unmarked objects pointed to by [start, end). |
| 326 | // Returns false if the operation fails (lack of stack space). |
| 327 | inline bool VisitUnmarkedObjects(Object** start, Object** end) { |
| 328 | // Return false is we are close to the stack limit. |
| 329 | StackLimitCheck check; |
| 330 | if (check.HasOverflowed()) return false; |
| 331 | |
| 332 | // Visit the unmarked objects. |
| 333 | for (Object** p = start; p < end; p++) { |
| 334 | if (!(*p)->IsHeapObject()) continue; |
| 335 | HeapObject* obj = HeapObject::cast(*p); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 336 | if (obj->IsMarked()) continue; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 337 | VisitUnmarkedObject(obj); |
| 338 | } |
| 339 | return true; |
| 340 | } |
| 341 | }; |
| 342 | |
| 343 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 344 | // Visitor class for marking heap roots. |
| 345 | class RootMarkingVisitor : public ObjectVisitor { |
| 346 | public: |
| 347 | void VisitPointer(Object** p) { |
| 348 | MarkObjectByPointer(p); |
| 349 | } |
| 350 | |
| 351 | void VisitPointers(Object** start, Object** end) { |
| 352 | for (Object** p = start; p < end; p++) MarkObjectByPointer(p); |
| 353 | } |
| 354 | |
| 355 | MarkingVisitor* stack_visitor() { return &stack_visitor_; } |
| 356 | |
| 357 | private: |
| 358 | MarkingVisitor stack_visitor_; |
| 359 | |
| 360 | void MarkObjectByPointer(Object** p) { |
| 361 | if (!(*p)->IsHeapObject()) return; |
| 362 | |
| 363 | // Replace flat cons strings in place. |
| 364 | HeapObject* object = ShortCircuitConsString(p); |
| 365 | if (object->IsMarked()) return; |
| 366 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 367 | Map* map = object->map(); |
| 368 | // Mark the object. |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 369 | MarkCompactCollector::SetMark(object); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 370 | // Mark the map pointer and body, and push them on the marking stack. |
| 371 | MarkCompactCollector::MarkObject(map); |
| 372 | object->IterateBody(map->instance_type(), object->SizeFromMap(map), |
| 373 | &stack_visitor_); |
| 374 | |
| 375 | // Mark all the objects reachable from the map and body. May leave |
| 376 | // overflowed objects in the heap. |
| 377 | MarkCompactCollector::EmptyMarkingStack(&stack_visitor_); |
| 378 | } |
| 379 | }; |
| 380 | |
| 381 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 382 | // Helper class for pruning the symbol table. |
| 383 | class SymbolTableCleaner : public ObjectVisitor { |
| 384 | public: |
| 385 | SymbolTableCleaner() : pointers_removed_(0) { } |
| 386 | void VisitPointers(Object** start, Object** end) { |
| 387 | // Visit all HeapObject pointers in [start, end). |
| 388 | for (Object** p = start; p < end; p++) { |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 389 | if ((*p)->IsHeapObject() && !HeapObject::cast(*p)->IsMarked()) { |
ager@chromium.org | 6f10e41 | 2009-02-13 10:11:16 +0000 | [diff] [blame] | 390 | // Check if the symbol being pruned is an external symbol. We need to |
| 391 | // delete the associated external data as this symbol is going away. |
| 392 | |
| 393 | // Since the object is not marked we can access its map word safely |
| 394 | // without having to worry about marking bits in the object header. |
| 395 | Map* map = HeapObject::cast(*p)->map(); |
| 396 | // Since no objects have yet been moved we can safely access the map of |
| 397 | // the object. |
| 398 | uint32_t type = map->instance_type(); |
| 399 | bool is_external = (type & kStringRepresentationMask) == |
| 400 | kExternalStringTag; |
| 401 | if (is_external) { |
| 402 | bool is_two_byte = (type & kStringEncodingMask) == kTwoByteStringTag; |
| 403 | byte* resource_addr = reinterpret_cast<byte*>(*p) + |
| 404 | ExternalString::kResourceOffset - |
| 405 | kHeapObjectTag; |
| 406 | if (is_two_byte) { |
ager@chromium.org | 80787b7 | 2009-04-17 10:24:24 +0000 | [diff] [blame] | 407 | v8::String::ExternalStringResource** resource = |
| 408 | reinterpret_cast<v8::String::ExternalStringResource**> |
ager@chromium.org | 6f10e41 | 2009-02-13 10:11:16 +0000 | [diff] [blame] | 409 | (resource_addr); |
ager@chromium.org | 80787b7 | 2009-04-17 10:24:24 +0000 | [diff] [blame] | 410 | delete *resource; |
| 411 | // Clear the resource pointer in the symbol. |
| 412 | *resource = NULL; |
ager@chromium.org | 6f10e41 | 2009-02-13 10:11:16 +0000 | [diff] [blame] | 413 | } else { |
ager@chromium.org | 80787b7 | 2009-04-17 10:24:24 +0000 | [diff] [blame] | 414 | v8::String::ExternalAsciiStringResource** resource = |
| 415 | reinterpret_cast<v8::String::ExternalAsciiStringResource**> |
ager@chromium.org | 6f10e41 | 2009-02-13 10:11:16 +0000 | [diff] [blame] | 416 | (resource_addr); |
ager@chromium.org | 80787b7 | 2009-04-17 10:24:24 +0000 | [diff] [blame] | 417 | delete *resource; |
| 418 | // Clear the resource pointer in the symbol. |
| 419 | *resource = NULL; |
ager@chromium.org | 6f10e41 | 2009-02-13 10:11:16 +0000 | [diff] [blame] | 420 | } |
| 421 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 422 | // Set the entry to null_value (as deleted). |
| 423 | *p = Heap::null_value(); |
| 424 | pointers_removed_++; |
| 425 | } |
| 426 | } |
| 427 | } |
| 428 | |
| 429 | int PointersRemoved() { |
| 430 | return pointers_removed_; |
| 431 | } |
| 432 | private: |
| 433 | int pointers_removed_; |
| 434 | }; |
| 435 | |
| 436 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 437 | void MarkCompactCollector::MarkUnmarkedObject(HeapObject* object) { |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 438 | ASSERT(!object->IsMarked()); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 439 | ASSERT(Heap::Contains(object)); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 440 | if (object->IsMap()) { |
| 441 | Map* map = Map::cast(object); |
| 442 | if (FLAG_cleanup_caches_in_maps_at_gc) { |
| 443 | map->ClearCodeCache(); |
| 444 | } |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 445 | SetMark(map); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 446 | if (FLAG_collect_maps && |
| 447 | map->instance_type() >= FIRST_JS_OBJECT_TYPE && |
| 448 | map->instance_type() <= JS_FUNCTION_TYPE) { |
| 449 | MarkMapContents(map); |
| 450 | } else { |
| 451 | marking_stack.Push(map); |
| 452 | } |
| 453 | } else { |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 454 | SetMark(object); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 455 | marking_stack.Push(object); |
| 456 | } |
| 457 | } |
| 458 | |
| 459 | |
| 460 | void MarkCompactCollector::MarkMapContents(Map* map) { |
| 461 | MarkDescriptorArray(reinterpret_cast<DescriptorArray*>( |
| 462 | *HeapObject::RawField(map, Map::kInstanceDescriptorsOffset))); |
| 463 | |
| 464 | // Mark the Object* fields of the Map. |
| 465 | // Since the descriptor array has been marked already, it is fine |
| 466 | // that one of these fields contains a pointer to it. |
| 467 | MarkingVisitor visitor; // Has no state or contents. |
| 468 | visitor.VisitPointers(HeapObject::RawField(map, Map::kPrototypeOffset), |
| 469 | HeapObject::RawField(map, Map::kSize)); |
| 470 | } |
| 471 | |
| 472 | |
| 473 | void MarkCompactCollector::MarkDescriptorArray( |
| 474 | DescriptorArray *descriptors) { |
| 475 | if (descriptors->IsMarked()) return; |
| 476 | // Empty descriptor array is marked as a root before any maps are marked. |
| 477 | ASSERT(descriptors != Heap::empty_descriptor_array()); |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 478 | SetMark(descriptors); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 479 | |
| 480 | FixedArray* contents = reinterpret_cast<FixedArray*>( |
| 481 | descriptors->get(DescriptorArray::kContentArrayIndex)); |
| 482 | ASSERT(contents->IsHeapObject()); |
| 483 | ASSERT(!contents->IsMarked()); |
| 484 | ASSERT(contents->IsFixedArray()); |
| 485 | ASSERT(contents->length() >= 2); |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 486 | SetMark(contents); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 487 | // Contents contains (value, details) pairs. If the details say |
| 488 | // that the type of descriptor is MAP_TRANSITION, CONSTANT_TRANSITION, |
| 489 | // or NULL_DESCRIPTOR, we don't mark the value as live. Only for |
| 490 | // type MAP_TRANSITION is the value a Object* (a Map*). |
| 491 | for (int i = 0; i < contents->length(); i += 2) { |
| 492 | // If the pair (value, details) at index i, i+1 is not |
| 493 | // a transition or null descriptor, mark the value. |
| 494 | PropertyDetails details(Smi::cast(contents->get(i + 1))); |
| 495 | if (details.type() < FIRST_PHANTOM_PROPERTY_TYPE) { |
| 496 | HeapObject* object = reinterpret_cast<HeapObject*>(contents->get(i)); |
| 497 | if (object->IsHeapObject() && !object->IsMarked()) { |
ager@chromium.org | 3bf7b91 | 2008-11-17 09:09:45 +0000 | [diff] [blame] | 498 | SetMark(object); |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 499 | marking_stack.Push(object); |
| 500 | } |
| 501 | } |
| 502 | } |
| 503 | // The DescriptorArray descriptors contains a pointer to its contents array, |
| 504 | // but the contents array is already marked. |
| 505 | marking_stack.Push(descriptors); |
| 506 | } |
| 507 | |
| 508 | |
| 509 | void MarkCompactCollector::CreateBackPointers() { |
| 510 | HeapObjectIterator iterator(Heap::map_space()); |
| 511 | while (iterator.has_next()) { |
| 512 | Object* next_object = iterator.next(); |
| 513 | if (next_object->IsMap()) { // Could also be ByteArray on free list. |
| 514 | Map* map = Map::cast(next_object); |
| 515 | if (map->instance_type() >= FIRST_JS_OBJECT_TYPE && |
| 516 | map->instance_type() <= JS_FUNCTION_TYPE) { |
| 517 | map->CreateBackPointers(); |
| 518 | } else { |
| 519 | ASSERT(map->instance_descriptors() == Heap::empty_descriptor_array()); |
| 520 | } |
| 521 | } |
| 522 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 523 | } |
| 524 | |
| 525 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 526 | static int OverflowObjectSize(HeapObject* obj) { |
| 527 | // Recover the normal map pointer, it might be marked as live and |
| 528 | // overflowed. |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 529 | MapWord map_word = obj->map_word(); |
| 530 | map_word.ClearMark(); |
| 531 | map_word.ClearOverflow(); |
| 532 | return obj->SizeFromMap(map_word.ToMap()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 533 | } |
| 534 | |
| 535 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 536 | // Fill the marking stack with overflowed objects returned by the given |
| 537 | // iterator. Stop when the marking stack is filled or the end of the space |
| 538 | // is reached, whichever comes first. |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 539 | template<class T> |
| 540 | static void ScanOverflowedObjects(T* it) { |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 541 | // The caller should ensure that the marking stack is initially not full, |
| 542 | // so that we don't waste effort pointlessly scanning for objects. |
| 543 | ASSERT(!marking_stack.is_full()); |
| 544 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 545 | while (it->has_next()) { |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 546 | HeapObject* object = it->next(); |
| 547 | if (object->IsOverflowed()) { |
| 548 | object->ClearOverflow(); |
| 549 | ASSERT(object->IsMarked()); |
| 550 | ASSERT(Heap::Contains(object)); |
| 551 | marking_stack.Push(object); |
| 552 | if (marking_stack.is_full()) return; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 553 | } |
| 554 | } |
| 555 | } |
| 556 | |
| 557 | |
| 558 | bool MarkCompactCollector::MustBeMarked(Object** p) { |
| 559 | // Check whether *p is a HeapObject pointer. |
| 560 | if (!(*p)->IsHeapObject()) return false; |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 561 | return !HeapObject::cast(*p)->IsMarked(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 562 | } |
| 563 | |
| 564 | |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 565 | class SymbolMarkingVisitor : public ObjectVisitor { |
| 566 | public: |
| 567 | void VisitPointers(Object** start, Object** end) { |
| 568 | MarkingVisitor marker; |
| 569 | for (Object** p = start; p < end; p++) { |
| 570 | if (!(*p)->IsHeapObject()) continue; |
| 571 | |
| 572 | HeapObject* object = HeapObject::cast(*p); |
| 573 | // If the object is marked, we have marked or are in the process |
| 574 | // of marking subparts. |
| 575 | if (object->IsMarked()) continue; |
| 576 | |
| 577 | // The object is unmarked, we do not need to unmark to use its |
| 578 | // map. |
| 579 | Map* map = object->map(); |
| 580 | object->IterateBody(map->instance_type(), |
| 581 | object->SizeFromMap(map), |
| 582 | &marker); |
| 583 | } |
| 584 | } |
| 585 | }; |
| 586 | |
| 587 | |
| 588 | void MarkCompactCollector::MarkSymbolTable() { |
| 589 | // Objects reachable from symbols are marked as live so as to ensure |
| 590 | // that if the symbol itself remains alive after GC for any reason, |
| 591 | // and if it is a sliced string or a cons string backed by an |
| 592 | // external string (even indirectly), then the external string does |
| 593 | // not receive a weak reference callback. |
| 594 | SymbolTable* symbol_table = SymbolTable::cast(Heap::symbol_table()); |
| 595 | // Mark the symbol table itself. |
| 596 | SetMark(symbol_table); |
| 597 | // Explicitly mark the prefix. |
| 598 | MarkingVisitor marker; |
| 599 | symbol_table->IteratePrefix(&marker); |
| 600 | ProcessMarkingStack(&marker); |
| 601 | // Mark subparts of the symbols but not the symbols themselves |
| 602 | // (unless reachable from another symbol). |
| 603 | SymbolMarkingVisitor symbol_marker; |
| 604 | symbol_table->IterateElements(&symbol_marker); |
| 605 | ProcessMarkingStack(&marker); |
| 606 | } |
| 607 | |
| 608 | |
| 609 | void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) { |
| 610 | // Mark the heap roots including global variables, stack variables, |
| 611 | // etc., and all objects reachable from them. |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 612 | Heap::IterateStrongRoots(visitor); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 613 | |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 614 | // Handle the symbol table specially. |
| 615 | MarkSymbolTable(); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 616 | |
| 617 | // There may be overflowed objects in the heap. Visit them now. |
| 618 | while (marking_stack.overflowed()) { |
| 619 | RefillMarkingStack(); |
| 620 | EmptyMarkingStack(visitor->stack_visitor()); |
| 621 | } |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 622 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 623 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 624 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 625 | void MarkCompactCollector::MarkObjectGroups() { |
ager@chromium.org | 8bb6058 | 2008-12-11 12:02:20 +0000 | [diff] [blame] | 626 | List<ObjectGroup*>* object_groups = GlobalHandles::ObjectGroups(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 627 | |
ager@chromium.org | 8bb6058 | 2008-12-11 12:02:20 +0000 | [diff] [blame] | 628 | for (int i = 0; i < object_groups->length(); i++) { |
| 629 | ObjectGroup* entry = object_groups->at(i); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 630 | if (entry == NULL) continue; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 631 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 632 | List<Object**>& objects = entry->objects_; |
| 633 | bool group_marked = false; |
| 634 | for (int j = 0; j < objects.length(); j++) { |
| 635 | Object* object = *objects[j]; |
| 636 | if (object->IsHeapObject() && HeapObject::cast(object)->IsMarked()) { |
| 637 | group_marked = true; |
| 638 | break; |
| 639 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 640 | } |
| 641 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 642 | if (!group_marked) continue; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 643 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 644 | // An object in the group is marked, so mark as gray all white heap |
| 645 | // objects in the group. |
| 646 | for (int j = 0; j < objects.length(); ++j) { |
| 647 | if ((*objects[j])->IsHeapObject()) { |
| 648 | MarkObject(HeapObject::cast(*objects[j])); |
| 649 | } |
| 650 | } |
| 651 | // Once the entire group has been colored gray, set the object group |
| 652 | // to NULL so it won't be processed again. |
ager@chromium.org | 8bb6058 | 2008-12-11 12:02:20 +0000 | [diff] [blame] | 653 | delete object_groups->at(i); |
| 654 | object_groups->at(i) = NULL; |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 655 | } |
| 656 | } |
| 657 | |
| 658 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 659 | // Mark all objects reachable from the objects on the marking stack. |
| 660 | // Before: the marking stack contains zero or more heap object pointers. |
| 661 | // After: the marking stack is empty, and all objects reachable from the |
| 662 | // marking stack have been marked, or are overflowed in the heap. |
| 663 | void MarkCompactCollector::EmptyMarkingStack(MarkingVisitor* visitor) { |
| 664 | while (!marking_stack.is_empty()) { |
| 665 | HeapObject* object = marking_stack.Pop(); |
| 666 | ASSERT(object->IsHeapObject()); |
| 667 | ASSERT(Heap::Contains(object)); |
| 668 | ASSERT(object->IsMarked()); |
| 669 | ASSERT(!object->IsOverflowed()); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 670 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 671 | // Because the object is marked, we have to recover the original map |
| 672 | // pointer and use it to mark the object's body. |
| 673 | MapWord map_word = object->map_word(); |
| 674 | map_word.ClearMark(); |
| 675 | Map* map = map_word.ToMap(); |
| 676 | MarkObject(map); |
| 677 | object->IterateBody(map->instance_type(), object->SizeFromMap(map), |
| 678 | visitor); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 679 | } |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 680 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 681 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 682 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 683 | // Sweep the heap for overflowed objects, clear their overflow bits, and |
| 684 | // push them on the marking stack. Stop early if the marking stack fills |
| 685 | // before sweeping completes. If sweeping completes, there are no remaining |
| 686 | // overflowed objects in the heap so the overflow flag on the markings stack |
| 687 | // is cleared. |
| 688 | void MarkCompactCollector::RefillMarkingStack() { |
| 689 | ASSERT(marking_stack.overflowed()); |
| 690 | |
| 691 | SemiSpaceIterator new_it(Heap::new_space(), &OverflowObjectSize); |
| 692 | ScanOverflowedObjects(&new_it); |
| 693 | if (marking_stack.is_full()) return; |
| 694 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 695 | HeapObjectIterator old_pointer_it(Heap::old_pointer_space(), |
| 696 | &OverflowObjectSize); |
| 697 | ScanOverflowedObjects(&old_pointer_it); |
| 698 | if (marking_stack.is_full()) return; |
| 699 | |
| 700 | HeapObjectIterator old_data_it(Heap::old_data_space(), &OverflowObjectSize); |
| 701 | ScanOverflowedObjects(&old_data_it); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 702 | if (marking_stack.is_full()) return; |
| 703 | |
| 704 | HeapObjectIterator code_it(Heap::code_space(), &OverflowObjectSize); |
| 705 | ScanOverflowedObjects(&code_it); |
| 706 | if (marking_stack.is_full()) return; |
| 707 | |
| 708 | HeapObjectIterator map_it(Heap::map_space(), &OverflowObjectSize); |
| 709 | ScanOverflowedObjects(&map_it); |
| 710 | if (marking_stack.is_full()) return; |
| 711 | |
| 712 | LargeObjectIterator lo_it(Heap::lo_space(), &OverflowObjectSize); |
| 713 | ScanOverflowedObjects(&lo_it); |
| 714 | if (marking_stack.is_full()) return; |
| 715 | |
| 716 | marking_stack.clear_overflowed(); |
| 717 | } |
| 718 | |
| 719 | |
| 720 | // Mark all objects reachable (transitively) from objects on the marking |
| 721 | // stack. Before: the marking stack contains zero or more heap object |
| 722 | // pointers. After: the marking stack is empty and there are no overflowed |
| 723 | // objects in the heap. |
| 724 | void MarkCompactCollector::ProcessMarkingStack(MarkingVisitor* visitor) { |
| 725 | EmptyMarkingStack(visitor); |
| 726 | while (marking_stack.overflowed()) { |
| 727 | RefillMarkingStack(); |
| 728 | EmptyMarkingStack(visitor); |
| 729 | } |
| 730 | } |
| 731 | |
| 732 | |
| 733 | void MarkCompactCollector::ProcessObjectGroups(MarkingVisitor* visitor) { |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 734 | bool work_to_do = true; |
| 735 | ASSERT(marking_stack.is_empty()); |
| 736 | while (work_to_do) { |
| 737 | MarkObjectGroups(); |
| 738 | work_to_do = !marking_stack.is_empty(); |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 739 | ProcessMarkingStack(visitor); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 740 | } |
| 741 | } |
| 742 | |
| 743 | |
| 744 | void MarkCompactCollector::MarkLiveObjects() { |
| 745 | #ifdef DEBUG |
| 746 | ASSERT(state_ == PREPARE_GC); |
| 747 | state_ = MARK_LIVE_OBJECTS; |
| 748 | #endif |
| 749 | // The to space contains live objects, the from space is used as a marking |
| 750 | // stack. |
| 751 | marking_stack.Initialize(Heap::new_space()->FromSpaceLow(), |
| 752 | Heap::new_space()->FromSpaceHigh()); |
| 753 | |
| 754 | ASSERT(!marking_stack.overflowed()); |
| 755 | |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 756 | RootMarkingVisitor root_visitor; |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 757 | MarkRoots(&root_visitor); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 758 | |
| 759 | // The objects reachable from the roots are marked black, unreachable |
| 760 | // objects are white. Mark objects reachable from object groups with at |
| 761 | // least one marked object, and continue until no new objects are |
| 762 | // reachable from the object groups. |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 763 | ProcessObjectGroups(root_visitor.stack_visitor()); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 764 | |
| 765 | // The objects reachable from the roots or object groups are marked black, |
| 766 | // unreachable objects are white. Process objects reachable only from |
| 767 | // weak global handles. |
| 768 | // |
| 769 | // First we mark weak pointers not yet reachable. |
| 770 | GlobalHandles::MarkWeakRoots(&MustBeMarked); |
| 771 | // Then we process weak pointers and process the transitive closure. |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 772 | GlobalHandles::IterateWeakRoots(&root_visitor); |
| 773 | while (marking_stack.overflowed()) { |
| 774 | RefillMarkingStack(); |
| 775 | EmptyMarkingStack(root_visitor.stack_visitor()); |
| 776 | } |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 777 | |
| 778 | // Repeat the object groups to mark unmarked groups reachable from the |
| 779 | // weak roots. |
mads.s.ager | 31e7138 | 2008-08-13 09:32:07 +0000 | [diff] [blame] | 780 | ProcessObjectGroups(root_visitor.stack_visitor()); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 781 | |
| 782 | // Prune the symbol table removing all symbols only pointed to by the |
| 783 | // symbol table. Cannot use SymbolTable::cast here because the symbol |
| 784 | // table is marked. |
| 785 | SymbolTable* symbol_table = |
| 786 | reinterpret_cast<SymbolTable*>(Heap::symbol_table()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 787 | SymbolTableCleaner v; |
| 788 | symbol_table->IterateElements(&v); |
| 789 | symbol_table->ElementsRemoved(v.PointersRemoved()); |
| 790 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 791 | // Remove object groups after marking phase. |
| 792 | GlobalHandles::RemoveObjectGroups(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 793 | } |
| 794 | |
| 795 | |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 796 | static int CountMarkedCallback(HeapObject* obj) { |
| 797 | MapWord map_word = obj->map_word(); |
| 798 | map_word.ClearMark(); |
| 799 | return obj->SizeFromMap(map_word.ToMap()); |
| 800 | } |
| 801 | |
| 802 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 803 | #ifdef DEBUG |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 804 | void MarkCompactCollector::UpdateLiveObjectCount(HeapObject* obj, int scale) { |
| 805 | ASSERT(scale == -1 || scale == 1); |
| 806 | live_bytes_ += obj->Size() * scale; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 807 | if (Heap::new_space()->Contains(obj)) { |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 808 | live_young_objects_ += scale; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 809 | } else if (Heap::map_space()->Contains(obj)) { |
| 810 | ASSERT(obj->IsMap()); |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 811 | live_map_objects_ += scale; |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 812 | } else if (Heap::old_pointer_space()->Contains(obj)) { |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 813 | live_old_pointer_objects_ += scale; |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 814 | } else if (Heap::old_data_space()->Contains(obj)) { |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 815 | live_old_data_objects_ += scale; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 816 | } else if (Heap::code_space()->Contains(obj)) { |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 817 | live_code_objects_ += scale; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 818 | } else if (Heap::lo_space()->Contains(obj)) { |
ager@chromium.org | 5ec4892 | 2009-05-05 07:25:34 +0000 | [diff] [blame^] | 819 | live_lo_objects_ +=scale; |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 820 | } else { |
| 821 | UNREACHABLE(); |
| 822 | } |
| 823 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 824 | #endif // DEBUG |
| 825 | |
| 826 | |
| 827 | void MarkCompactCollector::SweepLargeObjectSpace() { |
| 828 | #ifdef DEBUG |
| 829 | ASSERT(state_ == MARK_LIVE_OBJECTS); |
| 830 | state_ = |
| 831 | compacting_collection_ ? ENCODE_FORWARDING_ADDRESSES : SWEEP_SPACES; |
| 832 | #endif |
| 833 | // Deallocate unmarked objects and clear marked bits for marked objects. |
| 834 | Heap::lo_space()->FreeUnmarkedObjects(); |
| 835 | } |
| 836 | |
kasperl@chromium.org | 9bbf968 | 2008-10-30 11:53:07 +0000 | [diff] [blame] | 837 | // Safe to use during marking phase only. |
| 838 | bool MarkCompactCollector::SafeIsMap(HeapObject* object) { |
| 839 | MapWord metamap = object->map_word(); |
| 840 | metamap.ClearMark(); |
| 841 | return metamap.ToMap()->instance_type() == MAP_TYPE; |
| 842 | } |
| 843 | |
| 844 | void MarkCompactCollector::ClearNonLiveTransitions() { |
| 845 | HeapObjectIterator map_iterator(Heap::map_space(), &CountMarkedCallback); |
| 846 | // Iterate over the map space, setting map transitions that go from |
| 847 | // a marked map to an unmarked map to null transitions. At the same time, |
| 848 | // set all the prototype fields of maps back to their original value, |
| 849 | // dropping the back pointers temporarily stored in the prototype field. |
| 850 | // Setting the prototype field requires following the linked list of |
| 851 | // back pointers, reversing them all at once. This allows us to find |
| 852 | // those maps with map transitions that need to be nulled, and only |
| 853 | // scan the descriptor arrays of those maps, not all maps. |
| 854 | // All of these actions are carried out only on maps of JSObects |
| 855 | // and related subtypes. |
| 856 | while (map_iterator.has_next()) { |
| 857 | Map* map = reinterpret_cast<Map*>(map_iterator.next()); |
| 858 | if (!map->IsMarked() && map->IsByteArray()) continue; |
| 859 | |
| 860 | ASSERT(SafeIsMap(map)); |
| 861 | // Only JSObject and subtypes have map transitions and back pointers. |
| 862 | if (map->instance_type() < FIRST_JS_OBJECT_TYPE) continue; |
| 863 | if (map->instance_type() > JS_FUNCTION_TYPE) continue; |
| 864 | // Follow the chain of back pointers to find the prototype. |
| 865 | Map* current = map; |
| 866 | while (SafeIsMap(current)) { |
| 867 | current = reinterpret_cast<Map*>(current->prototype()); |
| 868 | ASSERT(current->IsHeapObject()); |
| 869 | } |
| 870 | Object* real_prototype = current; |
| 871 | |
| 872 | // Follow back pointers, setting them to prototype, |
| 873 | // clearing map transitions when necessary. |
| 874 | current = map; |
| 875 | bool on_dead_path = !current->IsMarked(); |
| 876 | Object *next; |
| 877 | while (SafeIsMap(current)) { |
| 878 | next = current->prototype(); |
| 879 | // There should never be a dead map above a live map. |
| 880 | ASSERT(on_dead_path || current->IsMarked()); |
| 881 | |
| 882 | // A live map above a dead map indicates a dead transition. |
| 883 | // This test will always be false on the first iteration. |
| 884 | if (on_dead_path && current->IsMarked()) { |
| 885 | on_dead_path = false; |
| 886 | current->ClearNonLiveTransitions(real_prototype); |
| 887 | } |
| 888 | *HeapObject::RawField(current, Map::kPrototypeOffset) = |
| 889 | real_prototype; |
| 890 | current = reinterpret_cast<Map*>(next); |
| 891 | } |
| 892 | } |
| 893 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 894 | |
| 895 | // ------------------------------------------------------------------------- |
| 896 | // Phase 2: Encode forwarding addresses. |
| 897 | // When compacting, forwarding addresses for objects in old space and map |
| 898 | // space are encoded in their map pointer word (along with an encoding of |
| 899 | // their map pointers). |
| 900 | // |
| 901 | // 31 21 20 10 9 0 |
| 902 | // +-----------------+------------------+-----------------+ |
| 903 | // |forwarding offset|page offset of map|page index of map| |
| 904 | // +-----------------+------------------+-----------------+ |
| 905 | // 11 bits 11 bits 10 bits |
| 906 | // |
| 907 | // An address range [start, end) can have both live and non-live objects. |
| 908 | // Maximal non-live regions are marked so they can be skipped on subsequent |
| 909 | // sweeps of the heap. A distinguished map-pointer encoding is used to mark |
| 910 | // free regions of one-word size (in which case the next word is the start |
| 911 | // of a live object). A second distinguished map-pointer encoding is used |
| 912 | // to mark free regions larger than one word, and the size of the free |
| 913 | // region (including the first word) is written to the second word of the |
| 914 | // region. |
| 915 | // |
| 916 | // Any valid map page offset must lie in the object area of the page, so map |
| 917 | // page offsets less than Page::kObjectStartOffset are invalid. We use a |
| 918 | // pair of distinguished invalid map encodings (for single word and multiple |
| 919 | // words) to indicate free regions in the page found during computation of |
| 920 | // forwarding addresses and skipped over in subsequent sweeps. |
| 921 | static const uint32_t kSingleFreeEncoding = 0; |
| 922 | static const uint32_t kMultiFreeEncoding = 1; |
| 923 | |
| 924 | |
| 925 | // Encode a free region, defined by the given start address and size, in the |
| 926 | // first word or two of the region. |
| 927 | void EncodeFreeRegion(Address free_start, int free_size) { |
| 928 | ASSERT(free_size >= kIntSize); |
| 929 | if (free_size == kIntSize) { |
| 930 | Memory::uint32_at(free_start) = kSingleFreeEncoding; |
| 931 | } else { |
| 932 | ASSERT(free_size >= 2 * kIntSize); |
| 933 | Memory::uint32_at(free_start) = kMultiFreeEncoding; |
| 934 | Memory::int_at(free_start + kIntSize) = free_size; |
| 935 | } |
| 936 | |
| 937 | #ifdef DEBUG |
| 938 | // Zap the body of the free region. |
| 939 | if (FLAG_enable_slow_asserts) { |
| 940 | for (int offset = 2 * kIntSize; |
| 941 | offset < free_size; |
| 942 | offset += kPointerSize) { |
| 943 | Memory::Address_at(free_start + offset) = kZapValue; |
| 944 | } |
| 945 | } |
| 946 | #endif |
| 947 | } |
| 948 | |
| 949 | |
| 950 | // Try to promote all objects in new space. Heap numbers and sequential |
| 951 | // strings are promoted to the code space, all others to the old space. |
| 952 | inline Object* MCAllocateFromNewSpace(HeapObject* object, int object_size) { |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 953 | OldSpace* target_space = Heap::TargetSpace(object); |
| 954 | ASSERT(target_space == Heap::old_pointer_space() || |
| 955 | target_space == Heap::old_data_space()); |
| 956 | Object* forwarded = target_space->MCAllocateRaw(object_size); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 957 | |
| 958 | if (forwarded->IsFailure()) { |
| 959 | forwarded = Heap::new_space()->MCAllocateRaw(object_size); |
| 960 | } |
| 961 | return forwarded; |
| 962 | } |
| 963 | |
| 964 | |
| 965 | // Allocation functions for the paged spaces call the space's MCAllocateRaw. |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 966 | inline Object* MCAllocateFromOldPointerSpace(HeapObject* object, |
| 967 | int object_size) { |
| 968 | return Heap::old_pointer_space()->MCAllocateRaw(object_size); |
| 969 | } |
| 970 | |
| 971 | |
| 972 | inline Object* MCAllocateFromOldDataSpace(HeapObject* object, int object_size) { |
| 973 | return Heap::old_data_space()->MCAllocateRaw(object_size); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 974 | } |
| 975 | |
| 976 | |
| 977 | inline Object* MCAllocateFromCodeSpace(HeapObject* object, int object_size) { |
| 978 | return Heap::code_space()->MCAllocateRaw(object_size); |
| 979 | } |
| 980 | |
| 981 | |
| 982 | inline Object* MCAllocateFromMapSpace(HeapObject* object, int object_size) { |
| 983 | return Heap::map_space()->MCAllocateRaw(object_size); |
| 984 | } |
| 985 | |
| 986 | |
| 987 | // The forwarding address is encoded at the same offset as the current |
| 988 | // to-space object, but in from space. |
| 989 | inline void EncodeForwardingAddressInNewSpace(HeapObject* old_object, |
| 990 | int object_size, |
| 991 | Object* new_object, |
| 992 | int* ignored) { |
| 993 | int offset = |
| 994 | Heap::new_space()->ToSpaceOffsetForAddress(old_object->address()); |
| 995 | Memory::Address_at(Heap::new_space()->FromSpaceLow() + offset) = |
| 996 | HeapObject::cast(new_object)->address(); |
| 997 | } |
| 998 | |
| 999 | |
| 1000 | // The forwarding address is encoded in the map pointer of the object as an |
| 1001 | // offset (in terms of live bytes) from the address of the first live object |
| 1002 | // in the page. |
| 1003 | inline void EncodeForwardingAddressInPagedSpace(HeapObject* old_object, |
| 1004 | int object_size, |
| 1005 | Object* new_object, |
| 1006 | int* offset) { |
| 1007 | // Record the forwarding address of the first live object if necessary. |
| 1008 | if (*offset == 0) { |
| 1009 | Page::FromAddress(old_object->address())->mc_first_forwarded = |
| 1010 | HeapObject::cast(new_object)->address(); |
| 1011 | } |
| 1012 | |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1013 | MapWord encoding = |
| 1014 | MapWord::EncodeAddress(old_object->map()->address(), *offset); |
| 1015 | old_object->set_map_word(encoding); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1016 | *offset += object_size; |
| 1017 | ASSERT(*offset <= Page::kObjectAreaSize); |
| 1018 | } |
| 1019 | |
| 1020 | |
| 1021 | // Most non-live objects are ignored. |
| 1022 | inline void IgnoreNonLiveObject(HeapObject* object) {} |
| 1023 | |
| 1024 | |
| 1025 | // A code deletion event is logged for non-live code objects. |
| 1026 | inline void LogNonLiveCodeObject(HeapObject* object) { |
| 1027 | if (object->IsCode()) LOG(CodeDeleteEvent(object->address())); |
| 1028 | } |
| 1029 | |
| 1030 | |
| 1031 | // Function template that, given a range of addresses (eg, a semispace or a |
| 1032 | // paged space page), iterates through the objects in the range to clear |
| 1033 | // mark bits and compute and encode forwarding addresses. As a side effect, |
| 1034 | // maximal free chunks are marked so that they can be skipped on subsequent |
| 1035 | // sweeps. |
| 1036 | // |
| 1037 | // The template parameters are an allocation function, a forwarding address |
| 1038 | // encoding function, and a function to process non-live objects. |
| 1039 | template<MarkCompactCollector::AllocationFunction Alloc, |
| 1040 | MarkCompactCollector::EncodingFunction Encode, |
| 1041 | MarkCompactCollector::ProcessNonLiveFunction ProcessNonLive> |
| 1042 | inline void EncodeForwardingAddressesInRange(Address start, |
| 1043 | Address end, |
| 1044 | int* offset) { |
| 1045 | // The start address of the current free region while sweeping the space. |
| 1046 | // This address is set when a transition from live to non-live objects is |
| 1047 | // encountered. A value (an encoding of the 'next free region' pointer) |
| 1048 | // is written to memory at this address when a transition from non-live to |
| 1049 | // live objects is encountered. |
| 1050 | Address free_start = NULL; |
| 1051 | |
| 1052 | // A flag giving the state of the previously swept object. Initially true |
| 1053 | // to ensure that free_start is initialized to a proper address before |
| 1054 | // trying to write to it. |
| 1055 | bool is_prev_alive = true; |
| 1056 | |
| 1057 | int object_size; // Will be set on each iteration of the loop. |
| 1058 | for (Address current = start; current < end; current += object_size) { |
| 1059 | HeapObject* object = HeapObject::FromAddress(current); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1060 | if (object->IsMarked()) { |
| 1061 | object->ClearMark(); |
| 1062 | MarkCompactCollector::tracer()->decrement_marked_count(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1063 | object_size = object->Size(); |
| 1064 | |
| 1065 | Object* forwarded = Alloc(object, object_size); |
| 1066 | // Allocation cannot fail, because we are compacting the space. |
| 1067 | ASSERT(!forwarded->IsFailure()); |
| 1068 | Encode(object, object_size, forwarded, offset); |
| 1069 | |
| 1070 | #ifdef DEBUG |
| 1071 | if (FLAG_gc_verbose) { |
| 1072 | PrintF("forward %p -> %p.\n", object->address(), |
| 1073 | HeapObject::cast(forwarded)->address()); |
| 1074 | } |
| 1075 | #endif |
| 1076 | if (!is_prev_alive) { // Transition from non-live to live. |
| 1077 | EncodeFreeRegion(free_start, current - free_start); |
| 1078 | is_prev_alive = true; |
| 1079 | } |
| 1080 | } else { // Non-live object. |
| 1081 | object_size = object->Size(); |
| 1082 | ProcessNonLive(object); |
| 1083 | if (is_prev_alive) { // Transition from live to non-live. |
| 1084 | free_start = current; |
| 1085 | is_prev_alive = false; |
| 1086 | } |
| 1087 | } |
| 1088 | } |
| 1089 | |
| 1090 | // If we ended on a free region, mark it. |
| 1091 | if (!is_prev_alive) EncodeFreeRegion(free_start, end - free_start); |
| 1092 | } |
| 1093 | |
| 1094 | |
| 1095 | // Functions to encode the forwarding pointers in each compactable space. |
| 1096 | void MarkCompactCollector::EncodeForwardingAddressesInNewSpace() { |
| 1097 | int ignored; |
| 1098 | EncodeForwardingAddressesInRange<MCAllocateFromNewSpace, |
| 1099 | EncodeForwardingAddressInNewSpace, |
| 1100 | IgnoreNonLiveObject>( |
| 1101 | Heap::new_space()->bottom(), |
| 1102 | Heap::new_space()->top(), |
| 1103 | &ignored); |
| 1104 | } |
| 1105 | |
| 1106 | |
| 1107 | template<MarkCompactCollector::AllocationFunction Alloc, |
| 1108 | MarkCompactCollector::ProcessNonLiveFunction ProcessNonLive> |
| 1109 | void MarkCompactCollector::EncodeForwardingAddressesInPagedSpace( |
| 1110 | PagedSpace* space) { |
| 1111 | PageIterator it(space, PageIterator::PAGES_IN_USE); |
| 1112 | while (it.has_next()) { |
| 1113 | Page* p = it.next(); |
| 1114 | // The offset of each live object in the page from the first live object |
| 1115 | // in the page. |
| 1116 | int offset = 0; |
| 1117 | EncodeForwardingAddressesInRange<Alloc, |
| 1118 | EncodeForwardingAddressInPagedSpace, |
| 1119 | ProcessNonLive>( |
| 1120 | p->ObjectAreaStart(), |
| 1121 | p->AllocationTop(), |
| 1122 | &offset); |
| 1123 | } |
| 1124 | } |
| 1125 | |
| 1126 | |
| 1127 | static void SweepSpace(NewSpace* space) { |
| 1128 | HeapObject* object; |
| 1129 | for (Address current = space->bottom(); |
| 1130 | current < space->top(); |
| 1131 | current += object->Size()) { |
| 1132 | object = HeapObject::FromAddress(current); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1133 | if (object->IsMarked()) { |
| 1134 | object->ClearMark(); |
| 1135 | MarkCompactCollector::tracer()->decrement_marked_count(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1136 | } else { |
| 1137 | // We give non-live objects a map that will correctly give their size, |
| 1138 | // since their existing map might not be live after the collection. |
| 1139 | int size = object->Size(); |
| 1140 | if (size >= Array::kHeaderSize) { |
| 1141 | object->set_map(Heap::byte_array_map()); |
| 1142 | ByteArray::cast(object)->set_length(ByteArray::LengthFor(size)); |
| 1143 | } else { |
| 1144 | ASSERT(size == kPointerSize); |
| 1145 | object->set_map(Heap::one_word_filler_map()); |
| 1146 | } |
| 1147 | ASSERT(object->Size() == size); |
| 1148 | } |
| 1149 | // The object is now unmarked for the call to Size() at the top of the |
| 1150 | // loop. |
| 1151 | } |
| 1152 | } |
| 1153 | |
| 1154 | |
| 1155 | static void SweepSpace(PagedSpace* space, DeallocateFunction dealloc) { |
| 1156 | PageIterator it(space, PageIterator::PAGES_IN_USE); |
| 1157 | while (it.has_next()) { |
| 1158 | Page* p = it.next(); |
| 1159 | |
| 1160 | bool is_previous_alive = true; |
| 1161 | Address free_start = NULL; |
| 1162 | HeapObject* object; |
| 1163 | |
| 1164 | for (Address current = p->ObjectAreaStart(); |
| 1165 | current < p->AllocationTop(); |
| 1166 | current += object->Size()) { |
| 1167 | object = HeapObject::FromAddress(current); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1168 | if (object->IsMarked()) { |
| 1169 | object->ClearMark(); |
| 1170 | MarkCompactCollector::tracer()->decrement_marked_count(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1171 | if (MarkCompactCollector::IsCompacting() && object->IsCode()) { |
| 1172 | // If this is compacting collection marked code objects have had |
| 1173 | // their IC targets converted to objects. |
| 1174 | // They need to be converted back to addresses. |
| 1175 | Code::cast(object)->ConvertICTargetsFromObjectToAddress(); |
| 1176 | } |
| 1177 | if (!is_previous_alive) { // Transition from free to live. |
| 1178 | dealloc(free_start, current - free_start); |
| 1179 | is_previous_alive = true; |
| 1180 | } |
| 1181 | } else { |
| 1182 | if (object->IsCode()) { |
iposva@chromium.org | 245aa85 | 2009-02-10 00:49:54 +0000 | [diff] [blame] | 1183 | // Notify the logger that compiled code has been collected. |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1184 | LOG(CodeDeleteEvent(Code::cast(object)->address())); |
| 1185 | } |
| 1186 | if (is_previous_alive) { // Transition from live to free. |
| 1187 | free_start = current; |
| 1188 | is_previous_alive = false; |
| 1189 | } |
| 1190 | } |
| 1191 | // The object is now unmarked for the call to Size() at the top of the |
| 1192 | // loop. |
| 1193 | } |
| 1194 | |
| 1195 | // If the last region was not live we need to from free_start to the |
| 1196 | // allocation top in the page. |
| 1197 | if (!is_previous_alive) { |
| 1198 | int free_size = p->AllocationTop() - free_start; |
| 1199 | if (free_size > 0) { |
| 1200 | dealloc(free_start, free_size); |
| 1201 | } |
| 1202 | } |
| 1203 | } |
| 1204 | } |
| 1205 | |
| 1206 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1207 | void MarkCompactCollector::DeallocateOldPointerBlock(Address start, |
| 1208 | int size_in_bytes) { |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1209 | Heap::ClearRSetRange(start, size_in_bytes); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1210 | Heap::old_pointer_space()->Free(start, size_in_bytes); |
| 1211 | } |
| 1212 | |
| 1213 | |
| 1214 | void MarkCompactCollector::DeallocateOldDataBlock(Address start, |
| 1215 | int size_in_bytes) { |
| 1216 | Heap::old_data_space()->Free(start, size_in_bytes); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1217 | } |
| 1218 | |
| 1219 | |
| 1220 | void MarkCompactCollector::DeallocateCodeBlock(Address start, |
| 1221 | int size_in_bytes) { |
| 1222 | Heap::code_space()->Free(start, size_in_bytes); |
| 1223 | } |
| 1224 | |
| 1225 | |
| 1226 | void MarkCompactCollector::DeallocateMapBlock(Address start, |
| 1227 | int size_in_bytes) { |
| 1228 | // Objects in map space are frequently assumed to have size Map::kSize and a |
| 1229 | // valid map in their first word. Thus, we break the free block up into |
| 1230 | // chunks and free them separately. |
| 1231 | ASSERT(size_in_bytes % Map::kSize == 0); |
| 1232 | Heap::ClearRSetRange(start, size_in_bytes); |
| 1233 | Address end = start + size_in_bytes; |
| 1234 | for (Address a = start; a < end; a += Map::kSize) { |
| 1235 | Heap::map_space()->Free(a); |
| 1236 | } |
| 1237 | } |
| 1238 | |
| 1239 | |
| 1240 | void MarkCompactCollector::EncodeForwardingAddresses() { |
| 1241 | ASSERT(state_ == ENCODE_FORWARDING_ADDRESSES); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1242 | // Objects in the active semispace of the young generation may be |
| 1243 | // relocated to the inactive semispace (if not promoted). Set the |
| 1244 | // relocation info to the beginning of the inactive semispace. |
| 1245 | Heap::new_space()->MCResetRelocationInfo(); |
| 1246 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1247 | // Compute the forwarding pointers in each space. |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1248 | EncodeForwardingAddressesInPagedSpace<MCAllocateFromOldPointerSpace, |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1249 | IgnoreNonLiveObject>( |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1250 | Heap::old_pointer_space()); |
| 1251 | |
| 1252 | EncodeForwardingAddressesInPagedSpace<MCAllocateFromOldDataSpace, |
| 1253 | IgnoreNonLiveObject>( |
| 1254 | Heap::old_data_space()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1255 | |
| 1256 | EncodeForwardingAddressesInPagedSpace<MCAllocateFromCodeSpace, |
| 1257 | LogNonLiveCodeObject>( |
| 1258 | Heap::code_space()); |
| 1259 | |
| 1260 | // Compute new space next to last after the old and code spaces have been |
| 1261 | // compacted. Objects in new space can be promoted to old or code space. |
| 1262 | EncodeForwardingAddressesInNewSpace(); |
| 1263 | |
| 1264 | // Compute map space last because computing forwarding addresses |
| 1265 | // overwrites non-live objects. Objects in the other spaces rely on |
| 1266 | // non-live map pointers to get the sizes of non-live objects. |
| 1267 | EncodeForwardingAddressesInPagedSpace<MCAllocateFromMapSpace, |
| 1268 | IgnoreNonLiveObject>( |
| 1269 | Heap::map_space()); |
| 1270 | |
| 1271 | // Write relocation info to the top page, so we can use it later. This is |
| 1272 | // done after promoting objects from the new space so we get the correct |
| 1273 | // allocation top. |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1274 | Heap::old_pointer_space()->MCWriteRelocationInfoToPage(); |
| 1275 | Heap::old_data_space()->MCWriteRelocationInfoToPage(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1276 | Heap::code_space()->MCWriteRelocationInfoToPage(); |
| 1277 | Heap::map_space()->MCWriteRelocationInfoToPage(); |
| 1278 | } |
| 1279 | |
| 1280 | |
| 1281 | void MarkCompactCollector::SweepSpaces() { |
| 1282 | ASSERT(state_ == SWEEP_SPACES); |
| 1283 | ASSERT(!IsCompacting()); |
| 1284 | // Noncompacting collections simply sweep the spaces to clear the mark |
| 1285 | // bits and free the nonlive blocks (for old and map spaces). We sweep |
| 1286 | // the map space last because freeing non-live maps overwrites them and |
| 1287 | // the other spaces rely on possibly non-live maps to get the sizes for |
| 1288 | // non-live objects. |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1289 | SweepSpace(Heap::old_pointer_space(), &DeallocateOldPointerBlock); |
| 1290 | SweepSpace(Heap::old_data_space(), &DeallocateOldDataBlock); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1291 | SweepSpace(Heap::code_space(), &DeallocateCodeBlock); |
| 1292 | SweepSpace(Heap::new_space()); |
| 1293 | SweepSpace(Heap::map_space(), &DeallocateMapBlock); |
| 1294 | } |
| 1295 | |
| 1296 | |
| 1297 | // Iterate the live objects in a range of addresses (eg, a page or a |
| 1298 | // semispace). The live regions of the range have been linked into a list. |
| 1299 | // The first live region is [first_live_start, first_live_end), and the last |
| 1300 | // address in the range is top. The callback function is used to get the |
| 1301 | // size of each live object. |
| 1302 | int MarkCompactCollector::IterateLiveObjectsInRange( |
| 1303 | Address start, |
| 1304 | Address end, |
| 1305 | HeapObjectCallback size_func) { |
| 1306 | int live_objects = 0; |
| 1307 | Address current = start; |
| 1308 | while (current < end) { |
| 1309 | uint32_t encoded_map = Memory::uint32_at(current); |
| 1310 | if (encoded_map == kSingleFreeEncoding) { |
| 1311 | current += kPointerSize; |
| 1312 | } else if (encoded_map == kMultiFreeEncoding) { |
| 1313 | current += Memory::int_at(current + kIntSize); |
| 1314 | } else { |
| 1315 | live_objects++; |
| 1316 | current += size_func(HeapObject::FromAddress(current)); |
| 1317 | } |
| 1318 | } |
| 1319 | return live_objects; |
| 1320 | } |
| 1321 | |
| 1322 | |
| 1323 | int MarkCompactCollector::IterateLiveObjects(NewSpace* space, |
| 1324 | HeapObjectCallback size_f) { |
| 1325 | ASSERT(MARK_LIVE_OBJECTS < state_ && state_ <= RELOCATE_OBJECTS); |
| 1326 | return IterateLiveObjectsInRange(space->bottom(), space->top(), size_f); |
| 1327 | } |
| 1328 | |
| 1329 | |
| 1330 | int MarkCompactCollector::IterateLiveObjects(PagedSpace* space, |
| 1331 | HeapObjectCallback size_f) { |
| 1332 | ASSERT(MARK_LIVE_OBJECTS < state_ && state_ <= RELOCATE_OBJECTS); |
| 1333 | int total = 0; |
| 1334 | PageIterator it(space, PageIterator::PAGES_IN_USE); |
| 1335 | while (it.has_next()) { |
| 1336 | Page* p = it.next(); |
| 1337 | total += IterateLiveObjectsInRange(p->ObjectAreaStart(), |
| 1338 | p->AllocationTop(), |
| 1339 | size_f); |
| 1340 | } |
| 1341 | return total; |
| 1342 | } |
| 1343 | |
| 1344 | |
ager@chromium.org | ddb913d | 2009-01-27 10:01:48 +0000 | [diff] [blame] | 1345 | // ------------------------------------------------------------------------- |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1346 | // Phase 3: Update pointers |
| 1347 | |
| 1348 | // Helper class for updating pointers in HeapObjects. |
| 1349 | class UpdatingVisitor: public ObjectVisitor { |
| 1350 | public: |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1351 | void VisitPointer(Object** p) { |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1352 | UpdatePointer(p); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1353 | } |
| 1354 | |
| 1355 | void VisitPointers(Object** start, Object** end) { |
| 1356 | // Mark all HeapObject pointers in [start, end) |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1357 | for (Object** p = start; p < end; p++) UpdatePointer(p); |
| 1358 | } |
| 1359 | |
| 1360 | private: |
| 1361 | void UpdatePointer(Object** p) { |
| 1362 | if (!(*p)->IsHeapObject()) return; |
| 1363 | |
| 1364 | HeapObject* obj = HeapObject::cast(*p); |
| 1365 | Address old_addr = obj->address(); |
| 1366 | Address new_addr; |
| 1367 | ASSERT(!Heap::InFromSpace(obj)); |
| 1368 | |
| 1369 | if (Heap::new_space()->Contains(obj)) { |
| 1370 | Address f_addr = Heap::new_space()->FromSpaceLow() + |
| 1371 | Heap::new_space()->ToSpaceOffsetForAddress(old_addr); |
| 1372 | new_addr = Memory::Address_at(f_addr); |
| 1373 | |
| 1374 | #ifdef DEBUG |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1375 | ASSERT(Heap::old_pointer_space()->Contains(new_addr) || |
| 1376 | Heap::old_data_space()->Contains(new_addr) || |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1377 | Heap::code_space()->Contains(new_addr) || |
| 1378 | Heap::new_space()->FromSpaceContains(new_addr)); |
| 1379 | |
| 1380 | if (Heap::new_space()->FromSpaceContains(new_addr)) { |
| 1381 | ASSERT(Heap::new_space()->FromSpaceOffsetForAddress(new_addr) <= |
| 1382 | Heap::new_space()->ToSpaceOffsetForAddress(old_addr)); |
| 1383 | } |
| 1384 | #endif |
| 1385 | |
| 1386 | } else if (Heap::lo_space()->Contains(obj)) { |
| 1387 | // Don't move objects in the large object space. |
| 1388 | return; |
| 1389 | |
| 1390 | } else { |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1391 | ASSERT(Heap::old_pointer_space()->Contains(obj) || |
| 1392 | Heap::old_data_space()->Contains(obj) || |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1393 | Heap::code_space()->Contains(obj) || |
| 1394 | Heap::map_space()->Contains(obj)); |
| 1395 | |
| 1396 | new_addr = MarkCompactCollector::GetForwardingAddressInOldSpace(obj); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1397 | ASSERT(Heap::old_pointer_space()->Contains(new_addr) || |
| 1398 | Heap::old_data_space()->Contains(new_addr) || |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1399 | Heap::code_space()->Contains(new_addr) || |
| 1400 | Heap::map_space()->Contains(new_addr)); |
| 1401 | |
| 1402 | #ifdef DEBUG |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1403 | if (Heap::old_pointer_space()->Contains(obj)) { |
| 1404 | ASSERT(Heap::old_pointer_space()->MCSpaceOffsetForAddress(new_addr) <= |
| 1405 | Heap::old_pointer_space()->MCSpaceOffsetForAddress(old_addr)); |
| 1406 | } else if (Heap::old_data_space()->Contains(obj)) { |
| 1407 | ASSERT(Heap::old_data_space()->MCSpaceOffsetForAddress(new_addr) <= |
| 1408 | Heap::old_data_space()->MCSpaceOffsetForAddress(old_addr)); |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1409 | } else if (Heap::code_space()->Contains(obj)) { |
| 1410 | ASSERT(Heap::code_space()->MCSpaceOffsetForAddress(new_addr) <= |
| 1411 | Heap::code_space()->MCSpaceOffsetForAddress(old_addr)); |
| 1412 | } else { |
| 1413 | ASSERT(Heap::map_space()->MCSpaceOffsetForAddress(new_addr) <= |
| 1414 | Heap::map_space()->MCSpaceOffsetForAddress(old_addr)); |
| 1415 | } |
| 1416 | #endif |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1417 | } |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1418 | |
| 1419 | *p = HeapObject::FromAddress(new_addr); |
| 1420 | |
| 1421 | #ifdef DEBUG |
| 1422 | if (FLAG_gc_verbose) { |
| 1423 | PrintF("update %p : %p -> %p\n", |
| 1424 | reinterpret_cast<Address>(p), old_addr, new_addr); |
| 1425 | } |
| 1426 | #endif |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1427 | } |
| 1428 | }; |
| 1429 | |
mads.s.ager | cbaa060 | 2008-08-14 13:41:48 +0000 | [diff] [blame] | 1430 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1431 | void MarkCompactCollector::UpdatePointers() { |
| 1432 | #ifdef DEBUG |
| 1433 | ASSERT(state_ == ENCODE_FORWARDING_ADDRESSES); |
| 1434 | state_ = UPDATE_POINTERS; |
| 1435 | #endif |
| 1436 | UpdatingVisitor updating_visitor; |
| 1437 | Heap::IterateRoots(&updating_visitor); |
| 1438 | GlobalHandles::IterateWeakRoots(&updating_visitor); |
| 1439 | |
| 1440 | int live_maps = IterateLiveObjects(Heap::map_space(), |
| 1441 | &UpdatePointersInOldObject); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1442 | int live_pointer_olds = IterateLiveObjects(Heap::old_pointer_space(), |
| 1443 | &UpdatePointersInOldObject); |
| 1444 | int live_data_olds = IterateLiveObjects(Heap::old_data_space(), |
| 1445 | &UpdatePointersInOldObject); |
| 1446 | int live_codes = IterateLiveObjects(Heap::code_space(), |
| 1447 | &UpdatePointersInOldObject); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1448 | int live_news = IterateLiveObjects(Heap::new_space(), |
| 1449 | &UpdatePointersInNewObject); |
| 1450 | |
| 1451 | // Large objects do not move, the map word can be updated directly. |
| 1452 | LargeObjectIterator it(Heap::lo_space()); |
| 1453 | while (it.has_next()) UpdatePointersInNewObject(it.next()); |
| 1454 | |
| 1455 | USE(live_maps); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1456 | USE(live_pointer_olds); |
| 1457 | USE(live_data_olds); |
| 1458 | USE(live_codes); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1459 | USE(live_news); |
| 1460 | |
| 1461 | #ifdef DEBUG |
| 1462 | ASSERT(live_maps == live_map_objects_); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1463 | ASSERT(live_data_olds == live_old_data_objects_); |
| 1464 | ASSERT(live_pointer_olds == live_old_pointer_objects_); |
| 1465 | ASSERT(live_codes == live_code_objects_); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1466 | ASSERT(live_news == live_young_objects_); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1467 | #endif |
| 1468 | } |
| 1469 | |
| 1470 | |
| 1471 | int MarkCompactCollector::UpdatePointersInNewObject(HeapObject* obj) { |
| 1472 | // Keep old map pointers |
| 1473 | Map* old_map = obj->map(); |
| 1474 | ASSERT(old_map->IsHeapObject()); |
| 1475 | |
| 1476 | Address forwarded = GetForwardingAddressInOldSpace(old_map); |
| 1477 | |
| 1478 | ASSERT(Heap::map_space()->Contains(old_map)); |
| 1479 | ASSERT(Heap::map_space()->Contains(forwarded)); |
| 1480 | #ifdef DEBUG |
| 1481 | if (FLAG_gc_verbose) { |
| 1482 | PrintF("update %p : %p -> %p\n", obj->address(), old_map->address(), |
| 1483 | forwarded); |
| 1484 | } |
| 1485 | #endif |
| 1486 | // Update the map pointer. |
| 1487 | obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(forwarded))); |
| 1488 | |
| 1489 | // We have to compute the object size relying on the old map because |
| 1490 | // map objects are not relocated yet. |
| 1491 | int obj_size = obj->SizeFromMap(old_map); |
| 1492 | |
| 1493 | // Update pointers in the object body. |
| 1494 | UpdatingVisitor updating_visitor; |
| 1495 | obj->IterateBody(old_map->instance_type(), obj_size, &updating_visitor); |
| 1496 | return obj_size; |
| 1497 | } |
| 1498 | |
| 1499 | |
| 1500 | int MarkCompactCollector::UpdatePointersInOldObject(HeapObject* obj) { |
| 1501 | // Decode the map pointer. |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1502 | MapWord encoding = obj->map_word(); |
| 1503 | Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1504 | ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr))); |
| 1505 | |
| 1506 | // At this point, the first word of map_addr is also encoded, cannot |
| 1507 | // cast it to Map* using Map::cast. |
| 1508 | Map* map = reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr)); |
| 1509 | int obj_size = obj->SizeFromMap(map); |
| 1510 | InstanceType type = map->instance_type(); |
| 1511 | |
| 1512 | // Update map pointer. |
| 1513 | Address new_map_addr = GetForwardingAddressInOldSpace(map); |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1514 | int offset = encoding.DecodeOffset(); |
| 1515 | obj->set_map_word(MapWord::EncodeAddress(new_map_addr, offset)); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1516 | |
| 1517 | #ifdef DEBUG |
| 1518 | if (FLAG_gc_verbose) { |
| 1519 | PrintF("update %p : %p -> %p\n", obj->address(), |
| 1520 | map_addr, new_map_addr); |
| 1521 | } |
| 1522 | #endif |
| 1523 | |
| 1524 | // Update pointers in the object body. |
| 1525 | UpdatingVisitor updating_visitor; |
| 1526 | obj->IterateBody(type, obj_size, &updating_visitor); |
| 1527 | return obj_size; |
| 1528 | } |
| 1529 | |
| 1530 | |
| 1531 | Address MarkCompactCollector::GetForwardingAddressInOldSpace(HeapObject* obj) { |
| 1532 | // Object should either in old or map space. |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1533 | MapWord encoding = obj->map_word(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1534 | |
| 1535 | // Offset to the first live object's forwarding address. |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1536 | int offset = encoding.DecodeOffset(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1537 | Address obj_addr = obj->address(); |
| 1538 | |
| 1539 | // Find the first live object's forwarding address. |
| 1540 | Page* p = Page::FromAddress(obj_addr); |
| 1541 | Address first_forwarded = p->mc_first_forwarded; |
| 1542 | |
| 1543 | // Page start address of forwarded address. |
| 1544 | Page* forwarded_page = Page::FromAddress(first_forwarded); |
| 1545 | int forwarded_offset = forwarded_page->Offset(first_forwarded); |
| 1546 | |
| 1547 | // Find end of allocation of in the page of first_forwarded. |
| 1548 | Address mc_top = forwarded_page->mc_relocation_top; |
| 1549 | int mc_top_offset = forwarded_page->Offset(mc_top); |
| 1550 | |
| 1551 | // Check if current object's forward pointer is in the same page |
| 1552 | // as the first live object's forwarding pointer |
| 1553 | if (forwarded_offset + offset < mc_top_offset) { |
| 1554 | // In the same page. |
| 1555 | return first_forwarded + offset; |
| 1556 | } |
| 1557 | |
| 1558 | // Must be in the next page, NOTE: this may cross chunks. |
| 1559 | Page* next_page = forwarded_page->next_page(); |
| 1560 | ASSERT(next_page->is_valid()); |
| 1561 | |
| 1562 | offset -= (mc_top_offset - forwarded_offset); |
| 1563 | offset += Page::kObjectStartOffset; |
| 1564 | |
| 1565 | ASSERT_PAGE_OFFSET(offset); |
| 1566 | ASSERT(next_page->OffsetToAddress(offset) < next_page->mc_relocation_top); |
| 1567 | |
| 1568 | return next_page->OffsetToAddress(offset); |
| 1569 | } |
| 1570 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1571 | |
ager@chromium.org | ddb913d | 2009-01-27 10:01:48 +0000 | [diff] [blame] | 1572 | // ------------------------------------------------------------------------- |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1573 | // Phase 4: Relocate objects |
| 1574 | |
| 1575 | void MarkCompactCollector::RelocateObjects() { |
| 1576 | #ifdef DEBUG |
| 1577 | ASSERT(state_ == UPDATE_POINTERS); |
| 1578 | state_ = RELOCATE_OBJECTS; |
| 1579 | #endif |
| 1580 | // Relocates objects, always relocate map objects first. Relocating |
| 1581 | // objects in other space relies on map objects to get object size. |
| 1582 | int live_maps = IterateLiveObjects(Heap::map_space(), &RelocateMapObject); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1583 | int live_pointer_olds = IterateLiveObjects(Heap::old_pointer_space(), |
| 1584 | &RelocateOldPointerObject); |
| 1585 | int live_data_olds = IterateLiveObjects(Heap::old_data_space(), |
| 1586 | &RelocateOldDataObject); |
| 1587 | int live_codes = IterateLiveObjects(Heap::code_space(), &RelocateCodeObject); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1588 | int live_news = IterateLiveObjects(Heap::new_space(), &RelocateNewObject); |
| 1589 | |
| 1590 | USE(live_maps); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1591 | USE(live_data_olds); |
| 1592 | USE(live_pointer_olds); |
| 1593 | USE(live_codes); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1594 | USE(live_news); |
| 1595 | #ifdef DEBUG |
| 1596 | ASSERT(live_maps == live_map_objects_); |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1597 | ASSERT(live_data_olds == live_old_data_objects_); |
| 1598 | ASSERT(live_pointer_olds == live_old_pointer_objects_); |
| 1599 | ASSERT(live_codes == live_code_objects_); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1600 | ASSERT(live_news == live_young_objects_); |
| 1601 | #endif |
| 1602 | |
| 1603 | // Notify code object in LO to convert IC target to address |
| 1604 | // This must happen after lo_space_->Compact |
| 1605 | LargeObjectIterator it(Heap::lo_space()); |
| 1606 | while (it.has_next()) { ConvertCodeICTargetToAddress(it.next()); } |
| 1607 | |
| 1608 | // Flips from and to spaces |
| 1609 | Heap::new_space()->Flip(); |
| 1610 | |
| 1611 | // Sets age_mark to bottom in to space |
| 1612 | Address mark = Heap::new_space()->bottom(); |
| 1613 | Heap::new_space()->set_age_mark(mark); |
| 1614 | |
| 1615 | Heap::new_space()->MCCommitRelocationInfo(); |
| 1616 | #ifdef DEBUG |
| 1617 | // It is safe to write to the remembered sets as remembered sets on a |
| 1618 | // page-by-page basis after committing the m-c forwarding pointer. |
| 1619 | Page::set_rset_state(Page::IN_USE); |
| 1620 | #endif |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1621 | PagedSpaces spaces; |
| 1622 | while (PagedSpace* space = spaces.next()) space->MCCommitRelocationInfo(); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1623 | } |
| 1624 | |
| 1625 | |
| 1626 | int MarkCompactCollector::ConvertCodeICTargetToAddress(HeapObject* obj) { |
| 1627 | if (obj->IsCode()) { |
| 1628 | Code::cast(obj)->ConvertICTargetsFromObjectToAddress(); |
| 1629 | } |
| 1630 | return obj->Size(); |
| 1631 | } |
| 1632 | |
| 1633 | |
| 1634 | int MarkCompactCollector::RelocateMapObject(HeapObject* obj) { |
| 1635 | // decode map pointer (forwarded address) |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1636 | MapWord encoding = obj->map_word(); |
| 1637 | Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1638 | ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr))); |
| 1639 | |
| 1640 | // Get forwarding address before resetting map pointer |
| 1641 | Address new_addr = GetForwardingAddressInOldSpace(obj); |
| 1642 | |
| 1643 | // recover map pointer |
| 1644 | obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr))); |
| 1645 | |
| 1646 | // The meta map object may not be copied yet. |
| 1647 | Address old_addr = obj->address(); |
| 1648 | |
| 1649 | if (new_addr != old_addr) { |
| 1650 | memmove(new_addr, old_addr, Map::kSize); // copy contents |
| 1651 | } |
| 1652 | |
| 1653 | #ifdef DEBUG |
| 1654 | if (FLAG_gc_verbose) { |
| 1655 | PrintF("relocate %p -> %p\n", old_addr, new_addr); |
| 1656 | } |
| 1657 | #endif |
| 1658 | |
| 1659 | return Map::kSize; |
| 1660 | } |
| 1661 | |
| 1662 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1663 | static inline int RelocateOldObject(HeapObject* obj, |
| 1664 | OldSpace* space, |
| 1665 | Address new_addr, |
| 1666 | Address map_addr) { |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1667 | // recover map pointer |
| 1668 | obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr))); |
| 1669 | |
| 1670 | // This is a non-map object, it relies on the assumption that the Map space |
| 1671 | // is compacted before the Old space (see RelocateObjects). |
| 1672 | int obj_size = obj->Size(); |
| 1673 | ASSERT_OBJECT_SIZE(obj_size); |
| 1674 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1675 | ASSERT(space->MCSpaceOffsetForAddress(new_addr) <= |
| 1676 | space->MCSpaceOffsetForAddress(obj->address())); |
| 1677 | |
| 1678 | space->MCAdjustRelocationEnd(new_addr, obj_size); |
| 1679 | |
| 1680 | #ifdef DEBUG |
| 1681 | if (FLAG_gc_verbose) { |
| 1682 | PrintF("relocate %p -> %p\n", obj->address(), new_addr); |
| 1683 | } |
| 1684 | #endif |
| 1685 | |
| 1686 | return obj_size; |
| 1687 | } |
| 1688 | |
| 1689 | |
| 1690 | int MarkCompactCollector::RelocateOldNonCodeObject(HeapObject* obj, |
| 1691 | OldSpace* space) { |
| 1692 | // decode map pointer (forwarded address) |
| 1693 | MapWord encoding = obj->map_word(); |
| 1694 | Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
| 1695 | ASSERT(Heap::map_space()->Contains(map_addr)); |
| 1696 | |
| 1697 | // Get forwarding address before resetting map pointer |
| 1698 | Address new_addr = GetForwardingAddressInOldSpace(obj); |
| 1699 | |
| 1700 | int obj_size = RelocateOldObject(obj, space, new_addr, map_addr); |
| 1701 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1702 | Address old_addr = obj->address(); |
| 1703 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1704 | if (new_addr != old_addr) { |
| 1705 | memmove(new_addr, old_addr, obj_size); // copy contents |
| 1706 | } |
| 1707 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1708 | ASSERT(!HeapObject::FromAddress(new_addr)->IsCode()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1709 | |
| 1710 | return obj_size; |
| 1711 | } |
| 1712 | |
| 1713 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1714 | int MarkCompactCollector::RelocateOldPointerObject(HeapObject* obj) { |
| 1715 | return RelocateOldNonCodeObject(obj, Heap::old_pointer_space()); |
| 1716 | } |
| 1717 | |
| 1718 | |
| 1719 | int MarkCompactCollector::RelocateOldDataObject(HeapObject* obj) { |
| 1720 | return RelocateOldNonCodeObject(obj, Heap::old_data_space()); |
| 1721 | } |
| 1722 | |
| 1723 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1724 | int MarkCompactCollector::RelocateCodeObject(HeapObject* obj) { |
| 1725 | // decode map pointer (forwarded address) |
kasper.lund | 7276f14 | 2008-07-30 08:49:36 +0000 | [diff] [blame] | 1726 | MapWord encoding = obj->map_word(); |
| 1727 | Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1728 | ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr))); |
| 1729 | |
| 1730 | // Get forwarding address before resetting map pointer |
| 1731 | Address new_addr = GetForwardingAddressInOldSpace(obj); |
| 1732 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1733 | int obj_size = RelocateOldObject(obj, Heap::code_space(), new_addr, map_addr); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1734 | |
| 1735 | // convert inline cache target to address using old address |
| 1736 | if (obj->IsCode()) { |
| 1737 | // convert target to address first related to old_address |
| 1738 | Code::cast(obj)->ConvertICTargetsFromObjectToAddress(); |
| 1739 | } |
| 1740 | |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1741 | Address old_addr = obj->address(); |
| 1742 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1743 | if (new_addr != old_addr) { |
| 1744 | memmove(new_addr, old_addr, obj_size); // copy contents |
| 1745 | } |
| 1746 | |
| 1747 | HeapObject* copied_to = HeapObject::FromAddress(new_addr); |
| 1748 | if (copied_to->IsCode()) { |
| 1749 | // may also update inline cache target. |
| 1750 | Code::cast(copied_to)->Relocate(new_addr - old_addr); |
iposva@chromium.org | 245aa85 | 2009-02-10 00:49:54 +0000 | [diff] [blame] | 1751 | // Notify the logger that compiled code has moved. |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1752 | LOG(CodeMoveEvent(old_addr, new_addr)); |
| 1753 | } |
| 1754 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1755 | return obj_size; |
| 1756 | } |
| 1757 | |
| 1758 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1759 | int MarkCompactCollector::RelocateNewObject(HeapObject* obj) { |
| 1760 | int obj_size = obj->Size(); |
| 1761 | |
| 1762 | // Get forwarding address |
| 1763 | Address old_addr = obj->address(); |
| 1764 | int offset = Heap::new_space()->ToSpaceOffsetForAddress(old_addr); |
| 1765 | |
| 1766 | Address new_addr = |
| 1767 | Memory::Address_at(Heap::new_space()->FromSpaceLow() + offset); |
| 1768 | |
| 1769 | if (Heap::new_space()->FromSpaceContains(new_addr)) { |
| 1770 | ASSERT(Heap::new_space()->FromSpaceOffsetForAddress(new_addr) <= |
| 1771 | Heap::new_space()->ToSpaceOffsetForAddress(old_addr)); |
| 1772 | } else { |
ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1773 | OldSpace* target_space = Heap::TargetSpace(obj); |
| 1774 | ASSERT(target_space == Heap::old_pointer_space() || |
| 1775 | target_space == Heap::old_data_space()); |
| 1776 | target_space->MCAdjustRelocationEnd(new_addr, obj_size); |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1777 | } |
| 1778 | |
| 1779 | // New and old addresses cannot overlap. |
| 1780 | memcpy(reinterpret_cast<void*>(new_addr), |
| 1781 | reinterpret_cast<void*>(old_addr), |
| 1782 | obj_size); |
| 1783 | |
| 1784 | #ifdef DEBUG |
| 1785 | if (FLAG_gc_verbose) { |
| 1786 | PrintF("relocate %p -> %p\n", old_addr, new_addr); |
| 1787 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1788 | #endif |
| 1789 | |
| 1790 | return obj_size; |
| 1791 | } |
| 1792 | |
| 1793 | |
ager@chromium.org | ddb913d | 2009-01-27 10:01:48 +0000 | [diff] [blame] | 1794 | // ------------------------------------------------------------------------- |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 1795 | // Phase 5: rebuild remembered sets |
| 1796 | |
| 1797 | void MarkCompactCollector::RebuildRSets() { |
| 1798 | #ifdef DEBUG |
| 1799 | ASSERT(state_ == RELOCATE_OBJECTS); |
| 1800 | state_ = REBUILD_RSETS; |
| 1801 | #endif |
| 1802 | Heap::RebuildRSets(); |
| 1803 | } |
| 1804 | |
| 1805 | } } // namespace v8::internal |