V8 API Reference, 7.2.502.16 (for Deno 0.2.4)
circular-queue.h
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 // Lock-free cache-friendly sampling circular queue for large
15 // records. Intended for fast transfer of large records between a
16 // single producer and a single consumer. If the queue is full,
17 // StartEnqueue will return nullptr. The queue is designed with
18 // a goal in mind to evade cache lines thrashing by preventing
19 // simultaneous reads and writes to adjanced memory locations.
20 template<typename T, unsigned Length>
22  public:
23  // Executed on the application thread.
26 
27  // StartEnqueue returns a pointer to a memory location for storing the next
28  // record or nullptr if all entries are full at the moment.
29  T* StartEnqueue();
30  // Notifies the queue that the producer has complete writing data into the
31  // memory returned by StartEnqueue and it can be passed to the consumer.
32  void FinishEnqueue();
33 
34  // Executed on the consumer (analyzer) thread.
35  // Retrieves, but does not remove, the head of this queue, returning nullptr
36  // if this queue is empty. After the record had been read by a consumer,
37  // Remove must be called.
38  T* Peek();
39  void Remove();
40 
41  private:
42  // Reserved values for the entry marker.
43  enum {
44  kEmpty, // Marks clean (processed) entries.
45  kFull // Marks entries already filled by the producer but not yet
46  // completely processed by the consumer.
47  };
48 
49  struct V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry {
50  Entry() : marker(kEmpty) {}
51  T record;
52  base::Atomic32 marker;
53  };
54 
55  Entry* Next(Entry* entry);
56 
57  Entry buffer_[Length];
58  V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* enqueue_pos_;
59  V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* dequeue_pos_;
60 
61  DISALLOW_COPY_AND_ASSIGN(SamplingCircularQueue);
62 };
63 
64 
65 } // namespace internal
66 } // namespace v8
67 
68 #endif // V8_PROFILER_CIRCULAR_QUEUE_H_
Definition: libplatform.h:13