1 // Copyright 2010 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
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.
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.
28 #ifndef V8_CIRCULAR_QUEUE_H_
29 #define V8_CIRCULAR_QUEUE_H_
35 // Lock-free cache-friendly sampling circular queue for large
36 // records. Intended for fast transfer of large records between a
37 // single producer and a single consumer. If the queue is full,
38 // previous unread records are overwritten. The queue is designed with
39 // a goal in mind to evade cache lines thrashing by preventing
40 // simultaneous reads and writes to adjanced memory locations.
42 // IMPORTANT: as a producer never checks for chunks cleanness, it is
43 // possible that it can catch up and overwrite a chunk that a consumer
44 // is currently reading, resulting in a corrupt record being read.
45 class SamplingCircularQueue {
47 // Executed on the application thread.
48 SamplingCircularQueue(int record_size_in_bytes,
49 int desired_chunk_size_in_bytes,
50 int buffer_size_in_chunks);
51 ~SamplingCircularQueue();
53 // Enqueue returns a pointer to a memory location for storing the next
55 INLINE(void* Enqueue());
57 // Executed on the consumer (analyzer) thread.
58 // StartDequeue returns a pointer to a memory location for retrieving
59 // the next record. After the record had been read by a consumer,
60 // FinishDequeue must be called. Until that moment, subsequent calls
61 // to StartDequeue will return the same pointer.
64 // Due to a presence of slipping between the producer and the consumer,
65 // the queue must be notified whether producing has been finished in order
66 // to process remaining records from the buffer.
67 void FlushResidualRecords();
69 typedef AtomicWord Cell;
70 // Reserved values for the first cell of a record.
71 static const Cell kClear = 0; // Marks clean (processed) chunks.
72 static const Cell kEnd = -1; // Marks the end of the buffer.
75 struct ProducerPosition {
78 struct ConsumerPosition {
79 Cell* dequeue_chunk_pos;
80 Cell* dequeue_chunk_poll_pos;
82 Cell* dequeue_end_pos;
85 INLINE(void WrapPositionIfNeeded(Cell** pos));
87 const int record_size_;
88 const int chunk_size_in_bytes_;
89 const int chunk_size_;
90 const int buffer_size_;
91 const int producer_consumer_distance_;
94 ProducerPosition* producer_pos_;
95 ConsumerPosition* consumer_pos_;
97 DISALLOW_COPY_AND_ASSIGN(SamplingCircularQueue);
101 } } // namespace v8::internal
103 #endif // V8_CIRCULAR_QUEUE_H_