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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
