src/3rdparty/v8/src/circular-queue.cc

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  27
  28 #include "v8.h"
  29
  30 #include "circular-queue-inl.h"
  31
  32 namespace v8 {
  33 namespace internal {
  34
  35
  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
  82 SamplingCircularQueue::~SamplingCircularQueue() {
  83   DeleteArray(positions_);
  84   DeleteArray(buffer_);
  85 }
  86
  87
  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
 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
 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