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      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
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     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
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     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 
     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
    123