| // Copyright 2011 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_STORE_BUFFER_H_ |
| #define V8_STORE_BUFFER_H_ |
| |
| #include "src/allocation.h" |
| #include "src/base/logging.h" |
| #include "src/base/platform/platform.h" |
| #include "src/globals.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| class Page; |
| class PagedSpace; |
| class StoreBuffer; |
| |
| typedef void (*ObjectSlotCallback)(HeapObject** from, HeapObject* to); |
| |
| // Used to implement the write barrier by collecting addresses of pointers |
| // between spaces. |
| class StoreBuffer { |
| public: |
| explicit StoreBuffer(Heap* heap); |
| |
| static void StoreBufferOverflow(Isolate* isolate); |
| |
| void SetUp(); |
| void TearDown(); |
| |
| // This is used to add addresses to the store buffer non-concurrently. |
| inline void Mark(Address addr); |
| |
| // This is used to add addresses to the store buffer when multiple threads |
| // may operate on the store buffer. |
| inline void MarkSynchronized(Address addr); |
| |
| // This is used by the heap traversal to enter the addresses into the store |
| // buffer that should still be in the store buffer after GC. It enters |
| // addresses directly into the old buffer because the GC starts by wiping the |
| // old buffer and thereafter only visits each cell once so there is no need |
| // to attempt to remove any dupes. During the first part of a GC we |
| // are using the store buffer to access the old spaces and at the same time |
| // we are rebuilding the store buffer using this function. There is, however |
| // no issue of overwriting the buffer we are iterating over, because this |
| // stage of the scavenge can only reduce the number of addresses in the store |
| // buffer (some objects are promoted so pointers to them do not need to be in |
| // the store buffer). The later parts of the GC scan the pages that are |
| // exempt from the store buffer and process the promotion queue. These steps |
| // can overflow this buffer. We check for this and on overflow we call the |
| // callback set up with the StoreBufferRebuildScope object. |
| inline void EnterDirectlyIntoStoreBuffer(Address addr); |
| |
| // Iterates over all pointers that go from old space to new space. It will |
| // delete the store buffer as it starts so the callback should reenter |
| // surviving old-to-new pointers into the store buffer to rebuild it. |
| void IteratePointersToNewSpace(ObjectSlotCallback callback); |
| |
| static const int kStoreBufferOverflowBit = 1 << (14 + kPointerSizeLog2); |
| static const int kStoreBufferSize = kStoreBufferOverflowBit; |
| static const int kStoreBufferLength = kStoreBufferSize / sizeof(Address); |
| static const int kOldStoreBufferLength = kStoreBufferLength * 16; |
| static const int kHashSetLengthLog2 = 12; |
| static const int kHashSetLength = 1 << kHashSetLengthLog2; |
| |
| void Compact(); |
| |
| void GCPrologue(); |
| void GCEpilogue(); |
| |
| Object*** Limit() { return reinterpret_cast<Object***>(old_limit_); } |
| Object*** Start() { return reinterpret_cast<Object***>(old_start_); } |
| Object*** Top() { return reinterpret_cast<Object***>(old_top_); } |
| void SetTop(Object*** top) { |
| DCHECK(top >= Start()); |
| DCHECK(top <= Limit()); |
| old_top_ = reinterpret_cast<Address*>(top); |
| } |
| |
| bool old_buffer_is_sorted() { return old_buffer_is_sorted_; } |
| bool old_buffer_is_filtered() { return old_buffer_is_filtered_; } |
| |
| void EnsureSpace(intptr_t space_needed); |
| void Verify(); |
| |
| bool PrepareForIteration(); |
| |
| void Filter(int flag); |
| |
| // Eliminates all stale store buffer entries from the store buffer, i.e., |
| // slots that are not part of live objects anymore. This method must be |
| // called after marking, when the whole transitive closure is known and |
| // must be called before sweeping when mark bits are still intact. |
| void ClearInvalidStoreBufferEntries(); |
| void VerifyValidStoreBufferEntries(); |
| |
| private: |
| Heap* heap_; |
| |
| // The store buffer is divided up into a new buffer that is constantly being |
| // filled by mutator activity and an old buffer that is filled with the data |
| // from the new buffer after compression. |
| Address* start_; |
| Address* limit_; |
| |
| Address* old_start_; |
| Address* old_limit_; |
| Address* old_top_; |
| Address* old_reserved_limit_; |
| base::VirtualMemory* old_virtual_memory_; |
| |
| bool old_buffer_is_sorted_; |
| bool old_buffer_is_filtered_; |
| bool during_gc_; |
| // The garbage collector iterates over many pointers to new space that are not |
| // handled by the store buffer. This flag indicates whether the pointers |
| // found by the callbacks should be added to the store buffer or not. |
| bool store_buffer_rebuilding_enabled_; |
| StoreBufferCallback callback_; |
| bool may_move_store_buffer_entries_; |
| |
| base::VirtualMemory* virtual_memory_; |
| |
| // Two hash sets used for filtering. |
| // If address is in the hash set then it is guaranteed to be in the |
| // old part of the store buffer. |
| uintptr_t* hash_set_1_; |
| uintptr_t* hash_set_2_; |
| bool hash_sets_are_empty_; |
| |
| // Used for synchronization of concurrent store buffer access. |
| base::Mutex mutex_; |
| |
| void ClearFilteringHashSets(); |
| |
| bool SpaceAvailable(intptr_t space_needed); |
| void ExemptPopularPages(int prime_sample_step, int threshold); |
| |
| void ProcessOldToNewSlot(Address slot_address, |
| ObjectSlotCallback slot_callback); |
| |
| void FindPointersToNewSpaceInRegion(Address start, Address end, |
| ObjectSlotCallback slot_callback); |
| |
| void IteratePointersInStoreBuffer(ObjectSlotCallback slot_callback); |
| |
| #ifdef VERIFY_HEAP |
| void VerifyPointers(LargeObjectSpace* space); |
| #endif |
| |
| friend class DontMoveStoreBufferEntriesScope; |
| friend class FindPointersToNewSpaceVisitor; |
| friend class StoreBufferRebuildScope; |
| }; |
| |
| |
| class StoreBufferRebuilder { |
| public: |
| explicit StoreBufferRebuilder(StoreBuffer* store_buffer) |
| : store_buffer_(store_buffer) {} |
| |
| void Callback(MemoryChunk* page, StoreBufferEvent event); |
| |
| private: |
| StoreBuffer* store_buffer_; |
| |
| // We record in this variable how full the store buffer was when we started |
| // iterating over the current page, finding pointers to new space. If the |
| // store buffer overflows again we can exempt the page from the store buffer |
| // by rewinding to this point instead of having to search the store buffer. |
| Object*** start_of_current_page_; |
| // The current page we are scanning in the store buffer iterator. |
| MemoryChunk* current_page_; |
| }; |
| |
| |
| class StoreBufferRebuildScope { |
| public: |
| explicit StoreBufferRebuildScope(Heap* heap, StoreBuffer* store_buffer, |
| StoreBufferCallback callback) |
| : store_buffer_(store_buffer), |
| stored_state_(store_buffer->store_buffer_rebuilding_enabled_), |
| stored_callback_(store_buffer->callback_) { |
| store_buffer_->store_buffer_rebuilding_enabled_ = true; |
| store_buffer_->callback_ = callback; |
| (*callback)(heap, NULL, kStoreBufferStartScanningPagesEvent); |
| } |
| |
| ~StoreBufferRebuildScope() { |
| store_buffer_->callback_ = stored_callback_; |
| store_buffer_->store_buffer_rebuilding_enabled_ = stored_state_; |
| } |
| |
| private: |
| StoreBuffer* store_buffer_; |
| bool stored_state_; |
| StoreBufferCallback stored_callback_; |
| }; |
| |
| |
| class DontMoveStoreBufferEntriesScope { |
| public: |
| explicit DontMoveStoreBufferEntriesScope(StoreBuffer* store_buffer) |
| : store_buffer_(store_buffer), |
| stored_state_(store_buffer->may_move_store_buffer_entries_) { |
| store_buffer_->may_move_store_buffer_entries_ = false; |
| } |
| |
| ~DontMoveStoreBufferEntriesScope() { |
| store_buffer_->may_move_store_buffer_entries_ = stored_state_; |
| } |
| |
| private: |
| StoreBuffer* store_buffer_; |
| bool stored_state_; |
| }; |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_STORE_BUFFER_H_ |