Performance tuning from the trenches

Session description as announced:

"Mobile phones are becoming more and more powerful. The amount of computing power people carry in their pockets nowadays is mind boggling. But still, mobile devices are very much constrained by their battery capacity. So it is important to be frugal about the amount of processor cycles a mobile App uses. It is also important to achieve 60 frames per second, even if you are just creating yet another weather app. (The example will not be a weather app.)

In this session Jeroen will show how you can analyse and improve processor usage on your iOS app. The principals are general and applicable to any other platform, but Jeroen will demonstrate these principles with Xcode and iOS."

Transcript

1. Performance tuning from the trenches or „Some things I learned along the way”
2. Premature optimization is the root of all evil
3. 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
4. Jeroen Leenarts iOS Developer
8. 5 JUNI 2014 15:00 - 21:00 ! Thema: Full speed ahead! Met keynote speakers: ANDRÉ KUIPERS & NALDEN ! Unieke locatie: SS ROTTERDAM http://xebicon.nl
9. Premature optimization is the root of all evil
10. …about that quote…
11. Premature optimization is the root of all evil
12. "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"
13. iOS Performance tuning • Why does it matter? • What uses energy? • It’s all about the tools • Obvious things to do?
14. Why does it matter?
16. Cause under 60 fps
 simply won’t do… You only got 1/60th of second
17. What uses energy What Uses Energy? I/O CPU Graphics
18. 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
19. Race back to idle
20. Race back to idle
23. It’s all about the tools
24. I’ll show… • Some Xcode • Some instruments • Some iOS Simulator
25. Obvious things to do? • Use ARC • Use a Reuseidentifier • Don’t be transparant, be opaque • Don’t block the main thread • Size image resource appropriately • Enable GZip Compression • Set the shadow path http://www.raywenderlich.com/31166/25-ios-app-performance-tips-tricks
26. Set the shadow path view.layer.shadowOffset = CGSizeMake(-1.0f, 1.0f); view.layer.shadowRadius = 5.0f; view.layer.shadowOpacity = 0.6; ! view.layer.shadowPath = [[UIBezierPath bezierPathWithRect:view.bounds] CGPath]; http://www.raywenderlich.com/31166/25-ios-app-performance-tips-tricks#shadowpath
27. Obvious things to do? • Reuse and lazy load when appropriate • Cache • Re-use expensive objects (DateFormatters) • Let someone else do the work
28. Always a trade-off
29. Always a trade-off • Using CPU is usually is better compared to network I/O • Using memory is usually better compared to CPU
30. Go forth and optimize