Memory and CPU Profiling

A public talk given at the 1st iOS Conf ( https://iosconf.taxibeat.com ) in Athens on Wednesday, 08 March 2017.

A video of the of the talk is available at https://www.youtube.com/watch?v=lyNHJOsAxIs

Transcript

1. qnoid
2. qnoid Memory and CPU Profiling ⏱
3. qnoid Why should you do it you are running blind if not
4. qnoid What to look for red flags
5. qnoid How often on every new of functionality/release
6. qnoid Some knowledge of the code base can still do it without
7. qnoid Deep knowledge of the iOS SDK ARC, GCD
8. qnoid How to prepare device
9. qnoid Configuration release, base model
10. qnoid Red flags lead the investigation
11. qnoid Memory how much can you use before crashing
12. qnoid
13. qnoid Usage not all of it is yours
14. qnoid
15. qnoid Establish a baseline user’s “home” screen
16. qnoid Draw a trend what goes up, should come down
17. qnoid fixed baseline
18. qnoid bounded on the baseline
19. qnoid unbounded growth
20. qnoid Calculate usage per feature memory hungry
21. qnoid
22. qnoid
23. qnoid Memory warnings respond to them
24. qnoid Abandoned memory referenced
25. qnoid Generational Analysis see what’s left behind* * WWDC 2014 Session 418, Improving Your App with Instruments
27. qnoid Stacktrace finding the offending source code
29. qnoid Debug the View UI Hierarchy Peaking behind the curtain
31. qnoid leaked memory not referenced (reference cycle), not used
33. qnoid weak reference
35. qnoid bad access memory the unowned trap
37. qnoid risks why high memory usage is a bad thing
38. qnoid App terminated while in use Random and hard to reproduce (unknown user usage pattern) Peaks of memory usage can drive the app over the "limit" thus terminated.
39. qnoid A high baseline that puts a constraint on the features that can be added later
40. qnoid App terminated in the background or why the app always launches state preservation
41. qnoid Other apps are getting killed (including yours too!) getting the blame
42. qnoid actions what to do
43. qnoid bring the baseline down reduce image sizes reuse memory
44. qnoid release unused memory when is no longer used return to the baseline
45. qnoid reuse memory don’t allocate
46. qnoid CPU getting things done fast and responsive
47. qnoid Responsiveness
48. qnoid What responsive UI means responsive to touch
49. qnoid What responsive UI means responsive to user actions
51. qnoid UI lag time profiler
53. qnoid 60fps or 1 frame per ~17ms
54. qnoid User waiting time i.e. at login
55. qnoid the 0.1s / 1.0s / 10s rule know the limits * https://www.nngroup.com/articles/response-times-3-important-limits/
56. qnoid Graph how fast can you go
57. qnoid
58. qnoid Stay idle do you let the CPU rest
60. qnoid risks why high CPU usage is a bad thing
61. qnoid Main thread is busy unresponsive to touch miss opportunity to respond to memory warnings
62. qnoid Degrades user experience app does not "feel" smooth time wait processing
63. qnoid Unresponsive due to high cpu usage whether on the main thread or not
64. qnoid battery drain device runs hot
65. qnoid actions what to do
66. qnoid offload processing from main thread on background operations
67. qnoid Postpone processing for when required being lazy
68. qnoid Partition the work 2 cores = 200% CPU
69. qnoid Find what’s killing your CPU keeping you busy
70. qnoid In general tips and tricks
71. qnoid don’t tie user interface to processing i.e. network
72. qnoid didFinishLaunchingWithOptions 400ms is a good target (no more than 20 seconds)* * WWDC 2016 Session 406, Optimizing App Startup Time
73. qnoid applicationDidEnterBackground release resources persist state stay low
74. qnoid IBAction low hanging fruit
75. qnoid touch handling low hanging fruit
76. qnoid completion blocks low hanging fruit
77. qnoid Put it on schedule on every release
78. qnoid Keep a record of your measurements to compare and contrast
79. qnoid Go forth and release confident / knowing the risks
80. qnoid www qnoid.com
81. qnoid One more thing…
82. qnoid