The Road to 60 FPS

The Road to 60 FPS

Jason Sendros

Why care?

Android Frame Rendering Deep Dive

What happens on the UI thread?

VSync

Input

Animation

Draw

Frame 1 Frame 2 Frame 3

Get used to this guy

60FPS is inaccurate

Galaxy Core 2 33fps

Nexus 5 60fps 55fps

Nexus 4 60fps 49fps

How do you measure a skipped frame?

Choreographer

▪  FrameCallback

▪  Delivered during the next frame’s animation callback

▪  Measure the difference between two inputs

VSync

Input

Animation

Draw

17ms 17ms 17ms

Choreographer

VSync

Input

Animation

Draw

17ms 33ms 17ms

draw draw draw drop draw

17ms

public  interface  FrameCallback  {          /**            *  @param  frameTimeNanos  The  time  in  nanoseconds  when  the  frame  started  being  rendered            */          void  doFrame(long  frameTimeNanos);  }  

mFPSMeasuringCallback  =  new  Choreographer.FrameCallback()  {      @Override      public  void  doFrame(long  frameTimeNanos)  {            long  frameTimeMs  =  nsToMs(frameTimeNanos);

       if  (mLastFrameTimeMs  ==  FIRST_FRAME)  {              mLastFrameTimeMs  =  frameTimeMs;              mChoreographer.postFrameCallback(mFPSMeasuringCallback);              return;          }

       long  milliSecondDelay  =  frameTimeMs  -­‐  mLastFrameTimeMs;          mLastFrameTimeMs  =  frameTimeMs;          onFrameRendered(milliSecondDelay);            mChoreographer.postFrameCallback(mFPSMeasuringCallback);      }  };

First frame!

Report time between frames Always post the callback

An FPS measuring API

public  void  enable()  {          mLastFrameTimeMs  =  FIRST_FRAME;          mChoreographer.postFrameCallback(mFPSMeasuringCallback);  }  

public  void  disable()  {          mChoreographer.removeFrameCallback(mFPSMeasuringCallback);          report();  }  

A Reasonable Metric

Percent time spent dropping 2+ frames*

VSync

Input

Animation

Draw

0

<2 dropped frames = 6/11 = 55% 2+ dropped frames = 5/11 = 45%

4 dropped* 1 dropped 0 0 0 *rendered on the 5th frame

*…reasonable?

How does Facebook blame jank?

AutoBlame

▪  Must be lightweight

▪  High level

▪  Will not blame every slow frame

▪  Not perfect

VSync

Input

Animation

Draw

Expensive Work Marker

AutoBlame*

Year Class Slow time GC getView notifyDSC

2012 16% 6% 50% 16%

2014 22% 12% 44% 12%

*surprisingly accurate

AutoProfiler

VSync

Input

Animation

Draw

Expensive Work

AutoProfiler*

Method Time

com/android/widget/RecyclerView.onScrolled 16%

> com/facebook/logging/FeedLogger.onScroll 10%

> com/facebook/feed/NewsFeedFragment.maybeFetch 3.3%

>> com/facebook/feed/NewsFeedRecyclerView.notifyDataSetChange 3%

>> com/facebook/feed/FetchController.shouldFetch .3%

> com/facebook/prefetch/ImagePrefetcher.onScroll 2.7%

*totally made up shit

AutoProfiler

for  i  in  range(20):          time.sleep(1)          device.drag((start_x,  start_y),  (stop_x,  stop_y),  0.1,  15)  

Traceview sample based profiling

MonkeyRunner Script

Left as an exercise to the developer Post-process Traceview file

Systrace

▪  Add your own markers

▪  Sample base profiling

VSync

Input

Animation

Draw

Expensive Work

Marker

How can I quickly improve performance?

▪  Ideal Profiling Device

▪  Nexus 4

▪  KitKat

▪  Systrace

▪  Custom markers for problem areas

▪  Sample based profiling

▪  Find an interaction or event which consistently causes lag or jitter and profile it

Questions? jsendros