Making Xcode build times great again

Transcript

1. Making build times great again SCHIBSTED iOS JAM 2018 Xavier Jurado iOS Lead @ Schibsted Spain
2. Making build times great bearable again SCHIBSTED iOS JAM 2018 Xavier Jurado iOS Lead @ Schibsted Spain
3. Agenda → Motivation → Benchmarks → Recap 3/51
4. Motivation 4/51
5. 5/51
6. 6/51
7. Optimize build times → Lots of tips & tricks available → Some outdated information → Some myths → Lack of up to date analytical data 7/51
8. Benchmarks 8/51
9. Methodology → Real life project → Ruby script + fastlane → Xcode 9.3.1, debug configuration, simulator → 5 iterations cleaning derived data → 5 incremental iterations → https://github.schibsted.io/xavier-jurado/ios- common--xcode-benchmark 9/51
10. Benchmarks 1. Baseline 2. Function & expression optimization 3. Number of files/classes 4. New build system 5. dSYM generation 6. CPU 7. WMO 10/51
11. Baseline 11/51
12. 28 % 72 % Swift Objective-C Baseline → Coches.net project → 4 years old → ~700 source files → 44k loc → Cocoapods (~20 dependencies) → Forced default settings 12/51
13. Baseline Non incremental → Average: 159.76s → Stdev: 3.9s Incremental → Average: 9.5s → Stdev: 0,05s 13/51
14. Function & expression optimization 14/51
15. Motivation → Type checking: historical problem → Still an issue? Edge cases? 15/51
16. Execution Swift compiler diagnostic optionss1: OTHER_SWIFT_FLAGS=-driver-time-compilation -Xfrontend -debug-time-function-bodies -Xfrontend -debug-time-compilation … plus awk, grep, sed magick1 k1 https://koke.me/2017/03/24/diving-into-swift-compiler-performance/ s1 https://github.com/apple/swift/blob/master/docs/ CompilerPerformance.md#diagnostic-options 16/51
17. Results 11.5645 ( 42.5%) {compile: PopTip.o <= PopTip.swift} 10.6891 ( 8.9%) {compile: CameraPresenter.o <= CameraPresenter.swift} 10.6874 ( 8.9%) {compile: CameraUI.o <= CameraUI.swift} 10.6855 ( 8.9%) {compile: CameraViewController.o <= CameraViewController.swift} 10.6844 ( 8.9%) {compile: CheckCameraAccess.o <= CheckCameraAccess.swift} 10.6829 ( 8.9%) {compile: CheckPhotoAccess.o <= CheckPhotoAccess.swift} 10.6814 ( 8.9%) {compile: CollectionSelectorPresenter.o <= CollectionSelectorPresenter.swift} 10.6795 ( 8.9%) {compile: CollectionSelectorTableViewCell.o <= CollectionSelectorTableViewCell.swift} 10.6781 ( 8.9%) {compile: CollectionSelectorTableViewDataSource.o <= CollectionSelectorTableViewDataSource.swift} 10.1187 ( 11.5%) {compile: BadgeManager.o <= BadgeManager.swift} 10.1169 ( 11.5%) {compile: DeviceTokenManager.o <= DeviceTokenManager.swift} 10.1133 ( 11.5%) {compile: KnockerError.o <= KnockerError.swift} 10.1118 ( 11.4%) {compile: KnockerNotification.o <= KnockerNotification.swift} 10.1104 ( 11.4%) {compile: Knocker.o <= Knocker.swift} 10.1102 ( 11.4%) {compile: KnockerTrackingModule.o <= KnockerTrackingModule.swift} ... > 400 files took more than 1 second to compile 17/51
18. Results 11.5645 ( 42.5%) {compile: PopTip.o <= PopTip.swift} 10.6891 ( 8.9%) {compile: CameraPresenter.o <= CameraPresenter.swift} 10.6874 ( 8.9%) {compile: CameraUI.o <= CameraUI.swift} 10.6855 ( 8.9%) {compile: CameraViewController.o <= CameraViewController.swift} 10.6844 ( 8.9%) {compile: CheckCameraAccess.o <= CheckCameraAccess.swift} 10.6829 ( 8.9%) {compile: CheckPhotoAccess.o <= CheckPhotoAccess.swift} 10.6814 ( 8.9%) {compile: CollectionSelectorPresenter.o <= CollectionSelectorPresenter.swift} 10.6795 ( 8.9%) {compile: CollectionSelectorTableViewCell.o <= CollectionSelectorTableViewCell.swift} 10.6781 ( 8.9%) {compile: CollectionSelectorTableViewDataSource.o <= CollectionSelectorTableViewDataSource.swift} 10.1187 ( 11.5%) {compile: BadgeManager.o <= BadgeManager.swift} 10.1169 ( 11.5%) {compile: DeviceTokenManager.o <= DeviceTokenManager.swift} 10.1133 ( 11.5%) {compile: KnockerError.o <= KnockerError.swift} 10.1118 ( 11.4%) {compile: KnockerNotification.o <= KnockerNotification.swift} 10.1104 ( 11.4%) {compile: Knocker.o <= Knocker.swift} 10.1102 ( 11.4%) {compile: KnockerTrackingModule.o <= KnockerTrackingModule.swift} ... 18/51
19. import Foundation extension Data { func toHexString() -> String { return self.reduce("", {$0 + String(format: "%02.2hhx", $1)}) } } @objc public class DeviceTokenManager: NSObject { private static let key:String = "knocker.device.token" static let defaults = UserDefaults.standard public static func store(_ deviceToken: Data) { defaults.set(deviceToken.toHexString(), forKey: key) defaults.synchronize() } public static func retrieve() -> String? { return defaults.object(forKey: key) as? String } public static func clear() { defaults.removeObject(forKey: key) } } 19/51
20. Conclusions → Quick wins. → Risk: write for the compiler instead of the developer. 20/51
21. Number of files vs number of classes 21/51
22. Motivation → As projects get bigger, Xcode gets slower → By how much? → Who's to blame? Code complexity? File count? 22/51
23. Execution → Add 100, 300 and 900 randomly generated classes to the project → Check incremental & absolute build times → Compare with 900 randomly generated classes inside a single file 23/51
24. // Autogenerated import Foundation class BenchmarkSwiftClass_0 { let dep: BenchmarkSwiftClass_15 private let iteration = 0 init(dep: BenchmarkSwiftClass_15) { self.dep = dep } } 24/51
25. Results 25/51
26. Conclusions → Huge cost on incremental builds. → Shall we take it into account when creating protocols, extensions, etc? 26/51
27. New build system 27/51
28. Motivation → Provides higher reliabilitya1 → Catches many project configuration problems. → Improves overall build-system performance. a1 https://developer.apple.com/library/content/documentation/DeveloperTools/ Conceptual/WhatsNewXcode/xcode9/xcode9.html 28/51
30. Execution UseNewBuildSystem=YES 30/51
31. Results ! 31/51
32. Conclusions → Performance wise it's a net loss. → May make Xcode more stable 32/51
33. dSYM generation 33/51
34. Motivation → "Popular culture" → DWARF vs DWARF + dSYM? → dSYM files are only needed for external analysis (ie: release builds) 34/51
35. Execution → DEBUG_INFORMATION_FORMAT: "dwarf" 35/51
36. Results meh. 36/51
37. Conclusions → No tangible effect 37/51
38. CPU 38/51
39. Motivation → Real life experience between MBP 13 (2 cores) & MBP 15 (4 cores) is abysmal. → What about faster processors? More cores? 39/51
40. Execution Computer CPU #Cores Freq Max Freq MacbookPro Mid 2015 i7-4980HQ 4 2,8 Ghz 4 Ghz Hackintosh Late 2017 i7-7700k 4 4.2 GHz 4.5 Ghz MacbookPro Mid 2017 i7-7820HQ 4 2.9 Ghz 3.9 Ghz MacbookPro Mid 2014 i7-4578U 2 3 Ghz 3.5 Ghz https://technical.city/en/cpu/Core-i7-7700K-vs-Core-i7-4980HQ 40/51
41. Results 41/51
42. Conclusions → #cores matters a lot. → If you don't have a 4 core machine, ask for one . → CPU matters, but newer != better. → Apple hardware is terrible has room for improvement. 42/51
43. WMO Whole Module Optimizations 43/51
44. Motivation → Introduced in Xcode 8 to produce faster Release binaries by applying optimizations that can only be performed to a whole module s2. → WMO: Compilation Mode + Optimization Level → It significantly changes the way the compiler runs. s2 https://swift.org/blog/whole-module-optimizations/ 44/51
45. Execution → Pre Xcode 9.3: SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule" OTHER_SWIFT_FLAGS="-Onone" → Xcode 9.3: has its own setting SWIFT_COMPILATION_MODE 45/51
46. As expected…? 46/51
47. ! 47/51
48. Conclusions → Greatly reduces absolute build times. → Can increase incremental build times. → Better for projects with lots of files. → Give it a try! 48/51
49. Recap 49/51
50. Worth your time 1. CPU 2. WMO (for big projects) 3. Function/expression optimization 4. Be aware of the implications of having lots of small files Not worth it → New build system (but may be worth it for Xcode stability) → dSYM 50/51
51. Thanks! 51/51