cc/base/histograms.cc

   1 // Copyright 2015 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 "cc/base/histograms.h"
   6
   7 #include <algorithm>
   8 #include <cmath>
   9 #include <limits>
  10
  11 #include "base/numerics/safe_conversions.h"
  12
  13 namespace cc {
  14
  15 // Minimum elapsed time of 1us to limit weighting of fast calls.
  16 static const int64 kMinimumTimeMicroseconds = 1;
  17
  18 ScopedUMAHistogramAreaTimerBase::ScopedUMAHistogramAreaTimerBase() : area_(0) {
  19 }
  20
  21 ScopedUMAHistogramAreaTimerBase::~ScopedUMAHistogramAreaTimerBase() {
  22 }
  23
  24 bool ScopedUMAHistogramAreaTimerBase::GetHistogramValues(
  25     Sample* time_microseconds,
  26     Sample* pixels_per_ms) const {
  27   return GetHistogramValues(
  28       timer_.Elapsed(), area_.ValueOrDefault(std::numeric_limits<int>::max()),
  29       time_microseconds, pixels_per_ms);
  30 }
  31
  32 // static
  33 bool ScopedUMAHistogramAreaTimerBase::GetHistogramValues(
  34     base::TimeDelta elapsed,
  35     int area,
  36     Sample* time_microseconds,
  37     Sample* pixels_per_ms) {
  38   elapsed = std::max(
  39       elapsed, base::TimeDelta::FromMicroseconds(kMinimumTimeMicroseconds));
  40   double area_per_time = area / elapsed.InMillisecondsF();
  41   // It is not clear how NaN can get here, but we've gotten crashes from
  42   // saturated_cast. http://crbug.com/486214
  43   if (std::isnan(area_per_time))
  44     return false;
  45   *time_microseconds = base::saturated_cast<Sample>(elapsed.InMicroseconds());
  46   *pixels_per_ms = base::saturated_cast<Sample>(area_per_time);
  47   return true;
  48 }
  49
  50 }  // namespace cc