xpcom/threads/InputEventStatistics.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "InputEventStatistics.h"
   8
   9 #include "mozilla/Preferences.h"
  10 #include "nsRefreshDriver.h"
  11
  12 namespace mozilla {
  13
  14 /*static*/ InputEventStatistics& InputEventStatistics::Get() {
  15   static UniquePtr<InputEventStatistics> sInstance;
  16   if (!sInstance) {
  17     sInstance = MakeUnique<InputEventStatistics>(ConstructorCookie());
  18     ClearOnShutdown(&sInstance);
  19   }
  20   return *sInstance;
  21 }
  22
  23 TimeDuration InputEventStatistics::TimeDurationCircularBuffer::GetMean() {
  24   return mTotal / (int64_t)mSize;
  25 }
  26
  27 InputEventStatistics::InputEventStatistics(ConstructorCookie&&)
  28     : mEnable(false) {
  29   MOZ_ASSERT(Preferences::IsServiceAvailable());
  30   uint32_t inputDuration = Preferences::GetUint(
  31       "input_event_queue.default_duration_per_event", sDefaultInputDuration);
  32
  33   TimeDuration defaultDuration = TimeDuration::FromMilliseconds(inputDuration);
  34
  35   uint32_t count = Preferences::GetUint(
  36       "input_event_queue.count_for_prediction", sInputCountForPrediction);
  37
  38   mLastInputDurations =
  39       MakeUnique<TimeDurationCircularBuffer>(count, defaultDuration);
  40
  41   uint32_t maxDuration = Preferences::GetUint("input_event_queue.duration.max",
  42                                               sMaxReservedTimeForHandlingInput);
  43
  44   uint32_t minDuration = Preferences::GetUint("input_event_queue.duration.min",
  45                                               sMinReservedTimeForHandlingInput);
  46
  47   mMaxInputDuration = TimeDuration::FromMilliseconds(maxDuration);
  48   mMinInputDuration = TimeDuration::FromMilliseconds(minDuration);
  49 }
  50
  51 TimeStamp InputEventStatistics::GetInputHandlingStartTime(
  52     uint32_t aInputCount) {
  53   MOZ_ASSERT(mEnable);
  54   Maybe<TimeStamp> nextTickHint = nsRefreshDriver::GetNextTickHint();
  55
  56   if (nextTickHint.isNothing()) {
  57     // Return a past time to process input events immediately.
  58     return TimeStamp::Now() - TimeDuration::FromMilliseconds(1);
  59   }
  60   TimeDuration inputCost = mLastInputDurations->GetMean() * aInputCount;
  61   inputCost = inputCost > mMaxInputDuration   ? mMaxInputDuration
  62               : inputCost < mMinInputDuration ? mMinInputDuration
  63                                               : inputCost;
  64
  65   return nextTickHint.value() - inputCost;
  66 }
  67
  68 TimeDuration InputEventStatistics::GetMaxInputHandlingDuration() const {
  69   MOZ_ASSERT(StaticPrefs::dom_input_events_strict_input_vsync_alignment());
  70   return mMaxInputDuration;
  71 }
  72 }  // namespace mozilla