Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2010 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_PROFILER_CIRCULAR_QUEUE_H_ |
| 6 | #define V8_PROFILER_CIRCULAR_QUEUE_H_ |
| 7 | |
| 8 | #include "src/base/atomicops.h" |
| 9 | #include "src/globals.h" |
| 10 | |
| 11 | namespace v8 { |
| 12 | namespace internal { |
| 13 | |
| 14 | |
| 15 | // Lock-free cache-friendly sampling circular queue for large |
| 16 | // records. Intended for fast transfer of large records between a |
| 17 | // single producer and a single consumer. If the queue is full, |
| 18 | // StartEnqueue will return NULL. The queue is designed with |
| 19 | // a goal in mind to evade cache lines thrashing by preventing |
| 20 | // simultaneous reads and writes to adjanced memory locations. |
| 21 | template<typename T, unsigned Length> |
| 22 | class SamplingCircularQueue { |
| 23 | public: |
| 24 | // Executed on the application thread. |
| 25 | SamplingCircularQueue(); |
| 26 | ~SamplingCircularQueue(); |
| 27 | |
| 28 | // StartEnqueue returns a pointer to a memory location for storing the next |
| 29 | // record or NULL if all entries are full at the moment. |
| 30 | T* StartEnqueue(); |
| 31 | // Notifies the queue that the producer has complete writing data into the |
| 32 | // memory returned by StartEnqueue and it can be passed to the consumer. |
| 33 | void FinishEnqueue(); |
| 34 | |
| 35 | // Executed on the consumer (analyzer) thread. |
| 36 | // Retrieves, but does not remove, the head of this queue, returning NULL |
| 37 | // if this queue is empty. After the record had been read by a consumer, |
| 38 | // Remove must be called. |
| 39 | T* Peek(); |
| 40 | void Remove(); |
| 41 | |
| 42 | private: |
| 43 | // Reserved values for the entry marker. |
| 44 | enum { |
| 45 | kEmpty, // Marks clean (processed) entries. |
| 46 | kFull // Marks entries already filled by the producer but not yet |
| 47 | // completely processed by the consumer. |
| 48 | }; |
| 49 | |
| 50 | struct V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry { |
| 51 | Entry() : marker(kEmpty) {} |
| 52 | T record; |
| 53 | base::Atomic32 marker; |
| 54 | }; |
| 55 | |
| 56 | Entry* Next(Entry* entry); |
| 57 | |
| 58 | Entry buffer_[Length]; |
| 59 | V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* enqueue_pos_; |
| 60 | V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* dequeue_pos_; |
| 61 | |
| 62 | DISALLOW_COPY_AND_ASSIGN(SamplingCircularQueue); |
| 63 | }; |
| 64 | |
| 65 | |
| 66 | } // namespace internal |
| 67 | } // namespace v8 |
| 68 | |
| 69 | #endif // V8_PROFILER_CIRCULAR_QUEUE_H_ |