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
4 // met:
5 //
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
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11 // with the distribution.
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15 //
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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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
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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.
27
28 #include "v8.h"
29
30 #include "circular-queue-inl.h"
31
32 namespace v8 {
33 namespace internal {
34
35
SamplingCircularQueue(int record_size_in_bytes,int desired_chunk_size_in_bytes,int buffer_size_in_chunks)36 SamplingCircularQueue::SamplingCircularQueue(int record_size_in_bytes,
37 int desired_chunk_size_in_bytes,
38 int buffer_size_in_chunks)
39 : record_size_(record_size_in_bytes / sizeof(Cell)),
40 chunk_size_in_bytes_(desired_chunk_size_in_bytes / record_size_in_bytes *
41 record_size_in_bytes),
42 chunk_size_(chunk_size_in_bytes_ / sizeof(Cell)),
43 buffer_size_(chunk_size_ * buffer_size_in_chunks),
44 // The distance ensures that producer and consumer never step on
45 // each other's chunks and helps eviction of produced data from
46 // the CPU cache (having that chunk size is bigger than the cache.)
47 producer_consumer_distance_(2 * chunk_size_),
48 buffer_(NewArray<Cell>(buffer_size_ + 1)) {
49 ASSERT(buffer_size_in_chunks > 2);
50 // Clean up the whole buffer to avoid encountering a random kEnd
51 // while enqueuing.
52 for (int i = 0; i < buffer_size_; ++i) {
53 buffer_[i] = kClear;
54 }
55 buffer_[buffer_size_] = kEnd;
56
57 // Layout producer and consumer position pointers each on their own
58 // cache lines to avoid cache lines thrashing due to simultaneous
59 // updates of positions by different processor cores.
60 const int positions_size =
61 RoundUp(1, kProcessorCacheLineSize) +
62 RoundUp(static_cast<int>(sizeof(ProducerPosition)),
63 kProcessorCacheLineSize) +
64 RoundUp(static_cast<int>(sizeof(ConsumerPosition)),
65 kProcessorCacheLineSize);
66 positions_ = NewArray<byte>(positions_size);
67
68 producer_pos_ = reinterpret_cast<ProducerPosition*>(
69 RoundUp(positions_, kProcessorCacheLineSize));
70 producer_pos_->enqueue_pos = buffer_;
71
72 consumer_pos_ = reinterpret_cast<ConsumerPosition*>(
73 reinterpret_cast<byte*>(producer_pos_) + kProcessorCacheLineSize);
74 ASSERT(reinterpret_cast<byte*>(consumer_pos_ + 1) <=
75 positions_ + positions_size);
76 consumer_pos_->dequeue_chunk_pos = buffer_;
77 consumer_pos_->dequeue_chunk_poll_pos = buffer_ + producer_consumer_distance_;
78 consumer_pos_->dequeue_pos = NULL;
79 }
80
81
~SamplingCircularQueue()82 SamplingCircularQueue::~SamplingCircularQueue() {
83 DeleteArray(positions_);
84 DeleteArray(buffer_);
85 }
86
87
StartDequeue()88 void* SamplingCircularQueue::StartDequeue() {
89 if (consumer_pos_->dequeue_pos != NULL) {
90 return consumer_pos_->dequeue_pos;
91 } else {
92 if (*consumer_pos_->dequeue_chunk_poll_pos != kClear) {
93 consumer_pos_->dequeue_pos = consumer_pos_->dequeue_chunk_pos;
94 consumer_pos_->dequeue_end_pos = consumer_pos_->dequeue_pos + chunk_size_;
95 return consumer_pos_->dequeue_pos;
96 } else {
97 return NULL;
98 }
99 }
100 }
101
102
FinishDequeue()103 void SamplingCircularQueue::FinishDequeue() {
104 consumer_pos_->dequeue_pos += record_size_;
105 if (consumer_pos_->dequeue_pos < consumer_pos_->dequeue_end_pos) return;
106 // Move to next chunk.
107 consumer_pos_->dequeue_pos = NULL;
108 *consumer_pos_->dequeue_chunk_pos = kClear;
109 consumer_pos_->dequeue_chunk_pos += chunk_size_;
110 WrapPositionIfNeeded(&consumer_pos_->dequeue_chunk_pos);
111 consumer_pos_->dequeue_chunk_poll_pos += chunk_size_;
112 WrapPositionIfNeeded(&consumer_pos_->dequeue_chunk_poll_pos);
113 }
114
115
FlushResidualRecords()116 void SamplingCircularQueue::FlushResidualRecords() {
117 // Eliminate producer / consumer distance.
118 consumer_pos_->dequeue_chunk_poll_pos = consumer_pos_->dequeue_chunk_pos;
119 }
120
121
122 } } // namespace v8::internal
123