src/circular-queue.cc

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#include "v8.h"

#include "circular-queue-inl.h"

namespace v8 {
namespace internal {


SamplingCircularQueue::SamplingCircularQueue(int record_size_in_bytes,
                                             int desired_chunk_size_in_bytes,
                                             int buffer_size_in_chunks)
    : record_size_(record_size_in_bytes / sizeof(Cell)),
      chunk_size_in_bytes_(desired_chunk_size_in_bytes / record_size_in_bytes *
                        record_size_in_bytes),
      chunk_size_(chunk_size_in_bytes_ / sizeof(Cell)),
      buffer_size_(chunk_size_ * buffer_size_in_chunks),
      // The distance ensures that producer and consumer never step on
      // each other's chunks and helps eviction of produced data from
      // the CPU cache (having that chunk size is bigger than the cache.)
      producer_consumer_distance_(2 * chunk_size_),
      buffer_(NewArray<Cell>(buffer_size_ + 1)) {
  ASSERT(buffer_size_in_chunks > 2);
  // Only need to keep the first cell of a chunk clean.
  for (int i = 0; i < buffer_size_; i += chunk_size_) {
    buffer_[i] = kClear;
  }
  buffer_[buffer_size_] = kEnd;
}


SamplingCircularQueue::~SamplingCircularQueue() {
  DeleteArray(buffer_);
}


void SamplingCircularQueue::SetUpProducer() {
  producer_key_ = Thread::CreateThreadLocalKey();
  Thread::SetThreadLocal(producer_key_, buffer_);
}


void SamplingCircularQueue::TearDownProducer() {
  Thread::DeleteThreadLocalKey(producer_key_);
}


void SamplingCircularQueue::SetUpConsumer() {
  consumer_key_ = Thread::CreateThreadLocalKey();
  ConsumerPosition* cp = new ConsumerPosition;
  cp->dequeue_chunk_pos = buffer_;
  cp->dequeue_chunk_poll_pos = buffer_ + producer_consumer_distance_;
  cp->dequeue_pos = NULL;
  Thread::SetThreadLocal(consumer_key_, cp);
}


void SamplingCircularQueue::TearDownConsumer() {
  delete reinterpret_cast<ConsumerPosition*>(
      Thread::GetThreadLocal(consumer_key_));
  Thread::DeleteThreadLocalKey(consumer_key_);
}


void* SamplingCircularQueue::StartDequeue() {
  ConsumerPosition* cp = reinterpret_cast<ConsumerPosition*>(
      Thread::GetThreadLocal(consumer_key_));
  if (cp->dequeue_pos != NULL) {
    return cp->dequeue_pos;
  } else {
    if (*cp->dequeue_chunk_poll_pos != kClear) {
      cp->dequeue_pos = cp->dequeue_chunk_pos;
      cp->dequeue_end_pos = cp->dequeue_pos + chunk_size_;
      return cp->dequeue_pos;
    } else {
      return NULL;
    }
  }
}


void SamplingCircularQueue::FinishDequeue() {
  ConsumerPosition* cp = reinterpret_cast<ConsumerPosition*>(
      Thread::GetThreadLocal(consumer_key_));
  cp->dequeue_pos += record_size_;
  if (cp->dequeue_pos < cp->dequeue_end_pos) return;
  // Move to next chunk.
  cp->dequeue_pos = NULL;
  *cp->dequeue_chunk_pos = kClear;
  cp->dequeue_chunk_pos += chunk_size_;
  WrapPositionIfNeeded(&cp->dequeue_chunk_pos);
  cp->dequeue_chunk_poll_pos += chunk_size_;
  WrapPositionIfNeeded(&cp->dequeue_chunk_poll_pos);
}


void SamplingCircularQueue::FlushResidualRecords() {
  ConsumerPosition* cp = reinterpret_cast<ConsumerPosition*>(
      Thread::GetThreadLocal(consumer_key_));
  // Eliminate producer / consumer distance.
  cp->dequeue_chunk_poll_pos = cp->dequeue_chunk_pos;
}


} }  // namespace v8::internal