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The Road to 60 FPS
This document discusses techniques for measuring and improving mobile app performance to achieve 60 frames per second (FPS). It explains that the UI thread is responsible for Vsync, input, animation, and drawing each frame. Measuring FPS accurately requires using the Choreographer class to detect dropped or delayed frames. The document also presents approaches like AutoBlame and AutoProfiler used by Facebook to identify sources of jank or stutter. It recommends using Systrace with custom markers on a Nexus 4 running KitKat to quickly profile problem areas and improve performance.
The Road to 60 FPS
- 1. The Road to60 FPS Jason Sendros
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- 3. Android Frame RenderingDeep Dive
- 4. What happens onthe UI thread? VSync Input Animation Draw Frame 1 Frame 2 Frame 3 Get used to this guy
- 5. 60FPS is inaccurate GalaxyCore 2 33fps Nexus 5 60fps 55fps Nexus 4 60fps 49fps
- 6. How do youmeasure a skipped frame?
- 7. Choreographer ▪ FrameCallback ▪ Deliveredduring the next frame’s animation callback ▪ Measure the difference between two inputs VSync Input Animation Draw 17ms 17ms17ms
- 8. Choreographer VSync Input Animation Draw 17ms 33ms17ms draw drawdrawdrop draw 17ms
- 9. public interface FrameCallback { /** * @param frameTimeNanos The time in nanoseconds when the frame started being rendered */ void doFrame(long frameTimeNanos); }
- 10. 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
- 11. An FPS measuringAPI public void enable() { mLastFrameTimeMs = FIRST_FRAME; mChoreographer.postFrameCallback(mFPSMeasuringCallback); } public void disable() { mChoreographer.removeFrameCallback(mFPSMeasuringCallback); report(); }
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- 13. Percent time spentdropping 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?
- 14. How does Facebookblame jank?
- 15. AutoBlame ▪ Must belightweight ▪ High level ▪ Will not blame every slow frame ▪ Not perfect VSync Input Animation Draw Expensive Work Marker
- 16. AutoBlame* Year Class Slowtime GC getView notifyDSC 2012 16% 6% 50% 16% 2014 22% 12% 44% 12% *surprisingly accurate
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- 18. 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
- 19. 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
- 20. Systrace ▪ Add yourown markers ▪ Sample base profiling VSync Input Animation Draw Expensive Work Marker
- 21. How can Iquickly 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
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