ash/metrics/task_switch_time_tracker.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 "ash/metrics/task_switch_time_tracker.h"
   6
   7 #include "base/metrics/histogram.h"
   8 #include "base/time/default_tick_clock.h"
   9
  10 namespace ash {
  11
  12 namespace {
  13
  14 // The number of buckets in the histogram.
  15 // See IMPORTANT note below if you want to change this value!
  16 const size_t kBucketCount = 50;
  17
  18 // The underflow (aka minimum) bucket size for the histogram.
  19 // See IMPORTANT note below if you want to change this value!
  20 const int kMinBucketSizeInSeconds = 0;
  21
  22 // The overflow (aka maximium) bucket size for the histogram.
  23 // See IMPORTANT note below if you want to change this value!
  24 const int kMaxBucketSizeInSeconds = 60 * 60;
  25
  26 }  // namespace
  27
  28 TaskSwitchTimeTracker::TaskSwitchTimeTracker(const std::string& histogram_name)
  29     : histogram_name_(histogram_name),
  30       tick_clock_(new base::DefaultTickClock()) {
  31 }
  32
  33 TaskSwitchTimeTracker::TaskSwitchTimeTracker(
  34     const std::string& histogram_name,
  35     scoped_ptr<base::TickClock> tick_clock)
  36     : histogram_name_(histogram_name), tick_clock_(tick_clock.release()) {
  37 }
  38
  39 TaskSwitchTimeTracker::~TaskSwitchTimeTracker() {
  40 }
  41
  42 void TaskSwitchTimeTracker::OnTaskSwitch() {
  43   if (!HasLastActionTime())
  44     SetLastActionTime();
  45   else
  46     RecordTimeDelta();
  47 }
  48
  49 bool TaskSwitchTimeTracker::HasLastActionTime() const {
  50   return last_action_time_ != base::TimeTicks();
  51 }
  52
  53 base::TimeTicks TaskSwitchTimeTracker::SetLastActionTime() {
  54   base::TimeTicks previous_last_action_time = last_action_time_;
  55   last_action_time_ = tick_clock_->NowTicks();
  56   return previous_last_action_time;
  57 }
  58
  59 void TaskSwitchTimeTracker::RecordTimeDelta() {
  60   base::TimeTicks previous_last_action_time = SetLastActionTime();
  61   base::TimeDelta time_delta = last_action_time_ - previous_last_action_time;
  62
  63   CHECK_GE(time_delta, base::TimeDelta());
  64
  65   GetHistogram()->Add(time_delta.InSeconds());
  66 }
  67
  68 base::HistogramBase* TaskSwitchTimeTracker::GetHistogram() {
  69   if (!histogram_) {
  70     // IMPORTANT: If you change the type of histogram or any values that define
  71     // its bucket construction then you must rename all of the histograms using
  72     // the TaskSwitchTimeTracker mechanism.
  73     histogram_ = base::Histogram::FactoryGet(
  74         histogram_name_,
  75         base::TimeDelta::FromSeconds(kMinBucketSizeInSeconds).InSeconds(),
  76         base::TimeDelta::FromSeconds(kMaxBucketSizeInSeconds).InSeconds(),
  77         kBucketCount, base::HistogramBase::kUmaTargetedHistogramFlag);
  78   }
  79
  80 #if DCHECK_IS_ON()
  81   histogram_->CheckName(histogram_name_);
  82 #endif  // DCHECK_IS_ON()
  83
  84   return histogram_;
  85 }
  86
  87 }  // namespace ash