1 // Copyright 2011 the V8 project authors. All rights reserved. 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 #ifndef V8_STORE_BUFFER_H_ 29 #define V8_STORE_BUFFER_H_ 30 31 #include "allocation.h" 32 #include "checks.h" 33 #include "globals.h" 34 #include "platform.h" 35 #include "v8globals.h" 36 37 namespace v8 { 38 namespace internal { 39 40 class StoreBuffer; 41 42 typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to); 43 44 typedef void (StoreBuffer::*RegionCallback)( 45 Address start, Address end, ObjectSlotCallback slot_callback); 46 47 // Used to implement the write barrier by collecting addresses of pointers 48 // between spaces. 49 class StoreBuffer { 50 public: 51 explicit StoreBuffer(Heap* heap); 52 53 static void StoreBufferOverflow(Isolate* isolate); 54 55 inline Address TopAddress(); 56 57 void SetUp(); 58 void TearDown(); 59 60 // This is used by the mutator to enter addresses into the store buffer. 61 inline void Mark(Address addr); 62 63 // This is used by the heap traversal to enter the addresses into the store 64 // buffer that should still be in the store buffer after GC. It enters 65 // addresses directly into the old buffer because the GC starts by wiping the 66 // old buffer and thereafter only visits each cell once so there is no need 67 // to attempt to remove any dupes. During the first part of a GC we 68 // are using the store buffer to access the old spaces and at the same time 69 // we are rebuilding the store buffer using this function. There is, however 70 // no issue of overwriting the buffer we are iterating over, because this 71 // stage of the scavenge can only reduce the number of addresses in the store 72 // buffer (some objects are promoted so pointers to them do not need to be in 73 // the store buffer). The later parts of the GC scan the pages that are 74 // exempt from the store buffer and process the promotion queue. These steps 75 // can overflow this buffer. We check for this and on overflow we call the 76 // callback set up with the StoreBufferRebuildScope object. 77 inline void EnterDirectlyIntoStoreBuffer(Address addr); 78 79 // Iterates over all pointers that go from old space to new space. It will 80 // delete the store buffer as it starts so the callback should reenter 81 // surviving old-to-new pointers into the store buffer to rebuild it. 82 void IteratePointersToNewSpace(ObjectSlotCallback callback); 83 84 static const int kStoreBufferOverflowBit = 1 << (14 + kPointerSizeLog2); 85 static const int kStoreBufferSize = kStoreBufferOverflowBit; 86 static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address); 87 static const int kOldStoreBufferLength = kStoreBufferLength * 16; 88 static const int kHashSetLengthLog2 = 12; 89 static const int kHashSetLength = 1 << kHashSetLengthLog2; 90 91 void Compact(); 92 93 void GCPrologue(); 94 void GCEpilogue(); 95 96 Object*** Limit() { return reinterpret_cast<Object***>(old_limit_); } 97 Object*** Start() { return reinterpret_cast<Object***>(old_start_); } 98 Object*** Top() { return reinterpret_cast<Object***>(old_top_); } 99 void SetTop(Object*** top) { 100 ASSERT(top >= Start()); 101 ASSERT(top <= Limit()); 102 old_top_ = reinterpret_cast<Address*>(top); 103 } 104 105 bool old_buffer_is_sorted() { return old_buffer_is_sorted_; } 106 bool old_buffer_is_filtered() { return old_buffer_is_filtered_; } 107 108 // Goes through the store buffer removing pointers to things that have 109 // been promoted. Rebuilds the store buffer completely if it overflowed. 110 void SortUniq(); 111 112 void EnsureSpace(intptr_t space_needed); 113 void Verify(); 114 115 bool PrepareForIteration(); 116 117 #ifdef DEBUG 118 void Clean(); 119 // Slow, for asserts only. 120 bool CellIsInStoreBuffer(Address cell); 121 #endif 122 123 void Filter(int flag); 124 125 private: 126 Heap* heap_; 127 128 // The store buffer is divided up into a new buffer that is constantly being 129 // filled by mutator activity and an old buffer that is filled with the data 130 // from the new buffer after compression. 131 Address* start_; 132 Address* limit_; 133 134 Address* old_start_; 135 Address* old_limit_; 136 Address* old_top_; 137 Address* old_reserved_limit_; 138 VirtualMemory* old_virtual_memory_; 139 140 bool old_buffer_is_sorted_; 141 bool old_buffer_is_filtered_; 142 bool during_gc_; 143 // The garbage collector iterates over many pointers to new space that are not 144 // handled by the store buffer. This flag indicates whether the pointers 145 // found by the callbacks should be added to the store buffer or not. 146 bool store_buffer_rebuilding_enabled_; 147 StoreBufferCallback callback_; 148 bool may_move_store_buffer_entries_; 149 150 VirtualMemory* virtual_memory_; 151 152 // Two hash sets used for filtering. 153 // If address is in the hash set then it is guaranteed to be in the 154 // old part of the store buffer. 155 uintptr_t* hash_set_1_; 156 uintptr_t* hash_set_2_; 157 bool hash_sets_are_empty_; 158 159 void ClearFilteringHashSets(); 160 161 void CheckForFullBuffer(); 162 void Uniq(); 163 void ExemptPopularPages(int prime_sample_step, int threshold); 164 165 void FindPointersToNewSpaceInRegion(Address start, 166 Address end, 167 ObjectSlotCallback slot_callback); 168 169 // For each region of pointers on a page in use from an old space call 170 // visit_pointer_region callback. 171 // If either visit_pointer_region or callback can cause an allocation 172 // in old space and changes in allocation watermark then 173 // can_preallocate_during_iteration should be set to true. 174 void IteratePointersOnPage( 175 PagedSpace* space, 176 Page* page, 177 RegionCallback region_callback, 178 ObjectSlotCallback slot_callback); 179 180 void FindPointersToNewSpaceInMaps( 181 Address start, 182 Address end, 183 ObjectSlotCallback slot_callback); 184 185 void FindPointersToNewSpaceInMapsRegion( 186 Address start, 187 Address end, 188 ObjectSlotCallback slot_callback); 189 190 void FindPointersToNewSpaceOnPage( 191 PagedSpace* space, 192 Page* page, 193 RegionCallback region_callback, 194 ObjectSlotCallback slot_callback); 195 196 void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback); 197 198 #ifdef DEBUG 199 void VerifyPointers(PagedSpace* space, RegionCallback region_callback); 200 void VerifyPointers(LargeObjectSpace* space); 201 #endif 202 203 friend class StoreBufferRebuildScope; 204 friend class DontMoveStoreBufferEntriesScope; 205 }; 206 207 208 class StoreBufferRebuildScope { 209 public: 210 explicit StoreBufferRebuildScope(Heap* heap, 211 StoreBuffer* store_buffer, 212 StoreBufferCallback callback) 213 : heap_(heap), 214 store_buffer_(store_buffer), 215 stored_state_(store_buffer->store_buffer_rebuilding_enabled_), 216 stored_callback_(store_buffer->callback_) { 217 store_buffer_->store_buffer_rebuilding_enabled_ = true; 218 store_buffer_->callback_ = callback; 219 (*callback)(heap, NULL, kStoreBufferStartScanningPagesEvent); 220 } 221 222 ~StoreBufferRebuildScope() { 223 store_buffer_->callback_ = stored_callback_; 224 store_buffer_->store_buffer_rebuilding_enabled_ = stored_state_; 225 store_buffer_->CheckForFullBuffer(); 226 } 227 228 private: 229 Heap* heap_; 230 StoreBuffer* store_buffer_; 231 bool stored_state_; 232 StoreBufferCallback stored_callback_; 233 }; 234 235 236 class DontMoveStoreBufferEntriesScope { 237 public: 238 explicit DontMoveStoreBufferEntriesScope(StoreBuffer* store_buffer) 239 : store_buffer_(store_buffer), 240 stored_state_(store_buffer->may_move_store_buffer_entries_) { 241 store_buffer_->may_move_store_buffer_entries_ = false; 242 } 243 244 ~DontMoveStoreBufferEntriesScope() { 245 store_buffer_->may_move_store_buffer_entries_ = stored_state_; 246 } 247 248 private: 249 StoreBuffer* store_buffer_; 250 bool stored_state_; 251 }; 252 253 } } // namespace v8::internal 254 255 #endif // V8_STORE_BUFFER_H_ 256
