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/ClearOnShutdown.h"
  10 #include "mozilla/Preferences.h"
  11 #include "nsRefreshDriver.h"
  12
  13 namespace mozilla {
  14
  15 /*static*/ InputEventStatistics& InputEventStatistics::Get() {
  16   static UniquePtr<InputEventStatistics> sInstance;
  17   if (!sInstance) {
  18     sInstance = MakeUnique<InputEventStatistics>(ConstructorCookie());
  19     ClearOnShutdown(&sInstance);
  20   }
  21   return *sInstance;
  22 }
  23
  24 TimeDuration InputEventStatistics::TimeDurationCircularBuffer::GetMean() {
  25   return mTotal / (int64_t)mSize;
  26 }
  27
  28 InputEventStatistics::InputEventStatistics(ConstructorCookie&&)
  29     : mEnable(false) {
  30   MOZ_ASSERT(Preferences::IsServiceAvailable());
  31   uint32_t inputDuration = Preferences::GetUint(
  32       "input_event_queue.default_duration_per_event", sDefaultInputDuration);
  33
  34   TimeDuration defaultDuration = TimeDuration::FromMilliseconds(inputDuration);
  35
  36   uint32_t count = Preferences::GetUint(
  37       "input_event_queue.count_for_prediction", sInputCountForPrediction);
  38
  39   mLastInputDurations =
  40       MakeUnique<TimeDurationCircularBuffer>(count, defaultDuration);
  41
  42   uint32_t maxDuration = Preferences::GetUint("input_event_queue.duration.max",
  43                                               sMaxReservedTimeForHandlingInput);
  44
  45   uint32_t minDuration = Preferences::GetUint("input_event_queue.duration.min",
  46                                               sMinReservedTimeForHandlingInput);
  47
  48   mMaxInputDuration = TimeDuration::FromMilliseconds(maxDuration);
  49   mMinInputDuration = TimeDuration::FromMilliseconds(minDuration);
  50 }
  51
  52 TimeStamp InputEventStatistics::GetInputHandlingStartTime(
  53     uint32_t aInputCount) {
  54   MOZ_ASSERT(mEnable);
  55   Maybe<TimeStamp> nextTickHint = nsRefreshDriver::GetNextTickHint();
  56
  57   if (nextTickHint.isNothing()) {
  58     // Return a past time to process input events immediately.
  59     return TimeStamp::Now() - TimeDuration::FromMilliseconds(1);
  60   }
  61   TimeDuration inputCost = mLastInputDurations->GetMean() * aInputCount;
  62   inputCost = inputCost > mMaxInputDuration   ? mMaxInputDuration
  63               : inputCost < mMinInputDuration ? mMinInputDuration
  64                                               : inputCost;
  65
  66   return nextTickHint.value() - inputCost;
  67 }
  68
  69 TimeDuration InputEventStatistics::GetMaxInputHandlingDuration() const {
  70   MOZ_ASSERT(StaticPrefs::dom_input_events_strict_input_vsync_alignment());
  71   return mMaxInputDuration;
  72 }
  73 }  // namespace mozilla