Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 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_ |