Introduction to Swift Performance - Try! Swift 2016

Transcript

1. An Introduction to Swift Performance Danielle Tomlinson - @dantoml
2. What makes code slow?
3. Allocation
4. Stack
5. Heap
6. Reference Counting
7. func perform(with object: Object) { object.doAThing() }
8. func perform(with object: Object) { __swift_retain(object) object.doAThing() __swift_release(object) }
9. Dispatch
10. Inline (0ns)
11. Static (~1ns)
12. Dynamic (~5ns)
13. Objects
14. Classes
15. p: Index* Stack class Index { let section: Int let item: Int } let i = Index(section: 1, item: 1) Heap section: Int item: Int
16. i: Index* Stack class Index { let section: Int let item: Int } let i = Index(section: 1, item: 1) let i2 = i Heap section: Int item: Int i2: Index*
17. i: Index* Stack class Index { let section: Int let item: Int } let i = Index(section: 1, item: 1) __swift_retain(i) let i2 = i Heap section: Int item: Int i2: Index*
18. Structs
19. Stack
20. section: 1 item: 1 Stack struct Index { let section: Int let item: Int } let i = Index(section: 1, item: 1)
21. Stack struct Index { let section: Int let item: Int } let i = Index(section: 1, item: 1) let i2 = i section: 1 item: 1 section: 1 item: 1
22. name: StringA* id: StringB* Stack struct User { let name: String let id: String } let u = User(name: "Joe", id: "1234")
23. name: StringA* id: StringB* Stack name: StringA* id: StringB* struct User { let name: String let id: String } let u = User(name: "Joe", id: "1234") __swift_retain(u.name._textStorage) __swift_retain(u.id._textStorage) let u2 = u
24. Abstractions
25. Example (0.3s) : struct Circle { let radius: Double let center: Point func draw() {} } var circles = (1..<100_000_000).map { _ in Circle(...) } for circle in circles { circle.draw() }
26. Requirements Change
27. Protocols
28. Example (4s) : protocol Drawable { func draw() } struct Circle: Drawable { let radius: Double let center: Point func draw() {} } let drawables: [Drawable] = (1..<100_000_000).map { _ in Circle(...) } for drawable in drawables { drawable.draw() }
29. Why?
30. struct Circle { let radius: Double let center: Point func draw() {} } var circles = (1..<100_000_000).map { _ in Circle(...) } for circle in circles { circle.draw() }
31. protocol Drawable { func draw() } struct Circle: Drawable { let radius: Double let center: Point func draw() {} } var drawables: [Drawable] = (1..<100_000_000).map { _ in return Circle(...) } for drawable in drawables { drawable.draw() }
32. ProtocolWitnessTable draw() CircleDrawable ... draw() LineDrawable ...
33. protocol Drawable { func draw() } struct Circle: Drawable { let radius: Double let center: Point func draw() {} } var drawables: [Drawable] = (1..<100_000_000).map { _ in return Circle(...) } for drawable in drawables { drawable.draw() } draw() CircleDrawable ...
34. ExistentialContainer ValueBuffer ProtocolWitnessTable
35. ExistentialContainer radius struct Circle: Drawable { let radius: Double let center: Point func draw() {} } center
36. ExistentialContainer struct Line: Drawable { let origin: Point let end: Point func draw() {} } Origin End
37. Example (45s) : protocol Drawable { func draw() } struct Line: Drawable { let origin: Point let end: Point func draw() {} } let drawables: [Drawable] = (1..<100_000_000).map { _ in Line(...) } for drawable in drawables { drawable.draw() }
39. ValueWitnessTable ValueBuffer allocate: copy: destruct: deallocate:
40. In Practice Stack origin Line vwt pwt end LineDrawable copy: ... Heap drawable: func draw(drawable: Drawable) { drawable.draw() } let value: Drawable = Line() draw(local: value) // Generates func draw(value: ECTDrawable) { var drawable: ECTDrawable = ECTDrawable() let vwt = value.vwt let pwt = value.pwt drawable.vwt = value.vwt drawable.pwt = value.pwt vwt.allocateBuffAndCopyValue(&drawable, value) pwt.draw(vwt.projectBuffer(&drawable) }
41. Modelling Your Data
42. Generics
43. struct Stack<T: Type> { ... }
44. Enumerations
45. enum AccountStatus: String, RawRepresentable { case .banned, .verified, incomplete }
46. Domain Specific Models
47. Thanks! Office Hours: 16:30 in the Atrium. @dantoml