XebiCon | iOS: Full Speed Ahead in your Pants (Performance tuning on iOS)

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PERFORMANCE TUNING ON IOS Jeroen Leenarts! Rotterdam, June 2014! [email protected] 10 April 2014 1

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. 10 "We should forget about small efﬁciencies, say about 97% of the time: premature optimization is the root of all evil. ! Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identiﬁed"

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. IOS PERFORMANCE TUNING ! Why does it matter?! ! What uses energy?! ! It’s all about the tools! ! Obvious things to do? 11

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Cause under 60 fps  simply won’t do… You only got 1/60th of second

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. ALWAYS A TRADE-OFF Using CPU is usually better compared to network I/O! Using memory is usually better compared to CPU 17

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. APPLE SAYS Be absolutely idle when app is not in use! Eliminate nonuser-driven work! Wait quietly for user input! ! Be efficient when user requests action! Performance = power! Efficient, multithreaded algorithms win (use GCD)! Then race back to idle 18

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. OBVIOUS THINGS TO DO Use ARC! Use a reuseidentifier! Don’t be transparant! Don’t block the main thread! Size image resources appropriately! Enable GZip compression! Set the shadow path 24

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. OBVIOUS THINGS TO DO? Reuse and lazy load when appropriate! Cache! Re-use expensive objects (DateFormatters!!)! Let someone/something else do the work. 26

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. TABLE VIEW TIPS You should reuse cells with the correct reuseIdentifier.! As many views as possible should have the opaque setting, including the cell itself.! Avoid sequences, scaled images and offscreen drawing.! If the height of the lines varies, they should be cached.! 27

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. TABLE VIEW TIPS If a cell shows contents from the web, queries should take place asynchronously and the responses should be cached.! Shadows can be created with shadowPath.! The number of subviews should be kept low. 28

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Copyright © 2014 Xebia Netherlands B.V. All rights reserved. For Xebia internal review only. LINKS ! https://github.com/jeroenleenarts/FibonacciTest! https://github.com/jeroenleenarts/PerformanceFunHouse! http://www.raywenderlich.com/31166/25-ios-app-performance-tips- tricks! WWDC 2012 session 712  https://developer.apple.com/videos/wwdc/2012/! https://developer.apple.com/library/mac/documentation/ DeveloperTools/Conceptual/InstrumentsUserGuide/Introduction/ Introduction.html! https://developer.apple.com/library/ios/documentation/iphone/ conceptual/iphoneosprogrammingguide/PerformanceTuning/ PerformanceTuning.html 29