// Copyright 2010 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_PROFILER_CIRCULAR_QUEUE_H_ #define V8_PROFILER_CIRCULAR_QUEUE_H_ #include "src/base/atomicops.h" #include "src/globals.h" namespace v8 { namespace internal { // Lock-free cache-friendly sampling circular queue for large // records. Intended for fast transfer of large records between a // single producer and a single consumer. If the queue is full, // StartEnqueue will return nullptr. The queue is designed with // a goal in mind to evade cache lines thrashing by preventing // simultaneous reads and writes to adjanced memory locations. template<typename T, unsigned Length> class SamplingCircularQueue { public: // Executed on the application thread. SamplingCircularQueue(); ~SamplingCircularQueue(); // StartEnqueue returns a pointer to a memory location for storing the next // record or nullptr if all entries are full at the moment. T* StartEnqueue(); // Notifies the queue that the producer has complete writing data into the // memory returned by StartEnqueue and it can be passed to the consumer. void FinishEnqueue(); // Executed on the consumer (analyzer) thread. // Retrieves, but does not remove, the head of this queue, returning nullptr // if this queue is empty. After the record had been read by a consumer, // Remove must be called. T* Peek(); void Remove(); private: // Reserved values for the entry marker. enum { kEmpty, // Marks clean (processed) entries. kFull // Marks entries already filled by the producer but not yet // completely processed by the consumer. }; struct alignas(PROCESSOR_CACHE_LINE_SIZE) Entry { Entry() : marker(kEmpty) {} T record; base::Atomic32 marker; }; Entry* Next(Entry* entry); Entry buffer_[Length]; alignas(PROCESSOR_CACHE_LINE_SIZE) Entry* enqueue_pos_; alignas(PROCESSOR_CACHE_LINE_SIZE) Entry* dequeue_pos_; DISALLOW_COPY_AND_ASSIGN(SamplingCircularQueue); }; } // namespace internal } // namespace v8 #endif // V8_PROFILER_CIRCULAR_QUEUE_H_