Line data Source code
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 165660 : 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_
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