Rewrite SamplingCircularQueue

src/circular-queue.cc

-// Copyright 2010 the V8 project authors. All rights reserved.
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-//       notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-//       copyright notice, this list of conditions and the following
-//       disclaimer in the documentation and/or other materials provided
-//       with the distribution.
-//     * Neither the name of Google Inc. nor the names of its
-//       contributors may be used to endorse or promote products derived
-//       from this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#include "v8.h"
-
-#include "circular-queue-inl.h"
-
-namespace v8 {
-namespace internal {
-
-
-SamplingCircularQueue::SamplingCircularQueue(size_t record_size_in_bytes,
-                                             size_t desired_chunk_size_in_bytes,
-                                             unsigned 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 + sizeof(Cell)),
-      chunk_size_(chunk_size_in_bytes_ / sizeof(Cell)),
-      buffer_size_(chunk_size_ * buffer_size_in_chunks),
-      buffer_(NewArray<Cell>(buffer_size_)) {
-  ASSERT(record_size_ * sizeof(Cell) == record_size_in_bytes);
-  ASSERT(chunk_size_ * sizeof(Cell) == chunk_size_in_bytes_);
-  ASSERT(buffer_size_in_chunks > 2);
-  // Mark all chunks as clear.
-  for (size_t i = 0; i < buffer_size_; i += chunk_size_) {
-    buffer_[i] = kClear;
-  }
-
-  // Layout producer and consumer position pointers each on their own
-  // cache lines to avoid cache lines thrashing due to simultaneous
-  // updates of positions by different processor cores.
-  const int positions_size =
-      RoundUp(1, kProcessorCacheLineSize) +
-      RoundUp(static_cast<int>(sizeof(ProducerPosition)),
-              kProcessorCacheLineSize) +
-      RoundUp(static_cast<int>(sizeof(ConsumerPosition)),
-              kProcessorCacheLineSize);
-  positions_ = NewArray<byte>(positions_size);
-
-  producer_pos_ = reinterpret_cast<ProducerPosition*>(
-      RoundUp(positions_, kProcessorCacheLineSize));
-  producer_pos_->next_chunk_pos = buffer_;
-  producer_pos_->enqueue_pos = buffer_;
-
-  consumer_pos_ = reinterpret_cast<ConsumerPosition*>(
-      reinterpret_cast<byte*>(producer_pos_) + kProcessorCacheLineSize);
-  ASSERT(reinterpret_cast<byte*>(consumer_pos_ + 1) <=
-         positions_ + positions_size);
-  consumer_pos_->dequeue_chunk_pos = buffer_;
-  // 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.)
-  const size_t producer_consumer_distance = (2 * chunk_size_);
-  consumer_pos_->dequeue_chunk_poll_pos = buffer_ + producer_consumer_distance;
-  consumer_pos_->dequeue_pos = NULL;
-}
-
-
-SamplingCircularQueue::~SamplingCircularQueue() {
-  DeleteArray(positions_);
-  DeleteArray(buffer_);
-}
-
-
-void* SamplingCircularQueue::StartDequeue() {
-  if (consumer_pos_->dequeue_pos != NULL) {
-    return consumer_pos_->dequeue_pos;
-  } else {
-    if (Acquire_Load(consumer_pos_->dequeue_chunk_poll_pos) != kClear) {
-      // Skip marker.
-      consumer_pos_->dequeue_pos = consumer_pos_->dequeue_chunk_pos + 1;
-      consumer_pos_->dequeue_end_pos =
-          consumer_pos_->dequeue_chunk_pos + chunk_size_;
-      return consumer_pos_->dequeue_pos;
-    } else {
-      return NULL;
-    }
-  }
-}
-
-
-void SamplingCircularQueue::FinishDequeue() {
-  consumer_pos_->dequeue_pos += record_size_;
-  if (consumer_pos_->dequeue_pos < consumer_pos_->dequeue_end_pos) return;
-  // Move to next chunk.
-  consumer_pos_->dequeue_pos = NULL;
-  *consumer_pos_->dequeue_chunk_pos = kClear;
-  consumer_pos_->dequeue_chunk_pos += chunk_size_;
-  WrapPositionIfNeeded(&consumer_pos_->dequeue_chunk_pos);
-  consumer_pos_->dequeue_chunk_poll_pos += chunk_size_;
-  WrapPositionIfNeeded(&consumer_pos_->dequeue_chunk_poll_pos);
-}
-
-
-void SamplingCircularQueue::FlushResidualRecords() {
-  // Eliminate producer / consumer distance.
-  consumer_pos_->dequeue_chunk_poll_pos = consumer_pos_->dequeue_chunk_pos;
-}
-
-
-} }  // namespace v8::internal