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// Copyright 2010 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_CIRCULAR_QUEUE_H_
#define V8_CIRCULAR_QUEUE_H_
#include "v8globals.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 NULL. 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 NULL 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 NULL
// 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 V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry {
Entry() : marker(kEmpty) {}
T record;
Atomic32 marker;
};
Entry* Next(Entry* entry);
Entry buffer_[Length];
V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* enqueue_pos_;
V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* dequeue_pos_;
DISALLOW_COPY_AND_ASSIGN(SamplingCircularQueue);
};
} } // namespace v8::internal
#endif // V8_CIRCULAR_QUEUE_H_
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