App Performance Tips and Examples

Bruce Evans
LINE App Dev Team6 Software Engineer
https://linedevday.linecorp.com/2020/ja/sessions/8808
https://linedevday.linecorp.com/2020/en/sessions/8808

Transcript

2. Agenda › How and Whys of Measurement › Tools and Settings › Dos and Don’ts
3. Why Do We Care? › Apps that take over 5s to launch see 19% uninstall rates off the bat › Users want immediate behavior → <1s › Every 1s during app launch reduces conversion rate by 7%
4. The real problem is that programmers have spent far too much time worrying about efficiency in the wrong places and at the wrong times; premature optimization is the root of all evil (or at least most of it) in programming — Donald Knuth, Computer Programming as an Art
5. Always Data Driven LINE STYLE Rule 03
6. Keep in Mind › Absolute vs Relative Performance › Use Instruments › Remember your goal › Test on Device
7. Tools XCTests Third Party Solutions Instruments › CPU, GPU, Memory, Power
8. Instruments
9. XCTest https://github.com/wikimedia/wikipedia-ios/blob/main/WikipediaUnitTests/Manual%20Tests/ReadingListManualPerformanceTests.swift#L18-L24
10. Third Party https://www.objc.io/blog/2018/06/14/quick-performance-timing/
11. Tips and Tricks
12. Compiler Settings › -O0, -O1, -O2, -O3, -Ofast, -Os, -Oz Clang Optimizations: Swift Whole Module Optimization (WMO) Swift Optimization: › -Onone, -O, -Osize LLVM Link-Time Optimization (LTO)
13. Generics Specialization
14. Coding › Mark classes private › Force Swift Backing over NSBacked › Mark classes final
15. Coding Forego ARC Use let in closures Copy on Write
16. Black Magic Perceived Performance › Display something › Prioritize important content › Free up the main thread
17. Conclusion › MEASURE! › Make use of the compiler › Code Smart › Be Sneaky › MEASURE!
18. Thank you