cc/scheduler/rolling_time_delta_history.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include <cmath>
   6
   7 #include "cc/scheduler/rolling_time_delta_history.h"
   8
   9 namespace cc {
  10
  11 RollingTimeDeltaHistory::RollingTimeDeltaHistory(size_t max_size)
  12     : max_size_(max_size) {
  13 }
  14
  15 RollingTimeDeltaHistory::~RollingTimeDeltaHistory() {
  16 }
  17
  18 void RollingTimeDeltaHistory::InsertSample(base::TimeDelta time) {
  19   if (max_size_ == 0)
  20     return;
  21
  22   if (sample_set_.size() == max_size_) {
  23     sample_set_.erase(chronological_sample_deque_.front());
  24     chronological_sample_deque_.pop_front();
  25   }
  26
  27   TimeDeltaMultiset::iterator it = sample_set_.insert(time);
  28   chronological_sample_deque_.push_back(it);
  29 }
  30
  31 void RollingTimeDeltaHistory::Clear() {
  32   chronological_sample_deque_.clear();
  33   sample_set_.clear();
  34 }
  35
  36 base::TimeDelta RollingTimeDeltaHistory::Percentile(double percent) const {
  37   if (sample_set_.size() == 0)
  38     return base::TimeDelta();
  39
  40   double fraction = percent / 100.0;
  41
  42   if (fraction <= 0.0)
  43     return *(sample_set_.begin());
  44
  45   if (fraction >= 1.0)
  46     return *(sample_set_.rbegin());
  47
  48   size_t num_smaller_samples =
  49       static_cast<size_t>(std::ceil(fraction * sample_set_.size())) - 1;
  50
  51   if (num_smaller_samples > sample_set_.size() / 2) {
  52     size_t num_larger_samples = sample_set_.size() - num_smaller_samples - 1;
  53     TimeDeltaMultiset::const_reverse_iterator it = sample_set_.rbegin();
  54     for (size_t i = 0; i < num_larger_samples; i++)
  55       it++;
  56     return *it;
  57   }
  58
  59   TimeDeltaMultiset::const_iterator it = sample_set_.begin();
  60   for (size_t i = 0; i < num_smaller_samples; i++)
  61     it++;
  62   return *it;
  63 }
  64
  65 }  // namespace cc