I have an app which I am trying to migrate to a new project. There is a heavy operation which I am handling in main thread asynchronously. In my older project, it takes just a second to complete this task but in my new project, it takes 6-7 seconds for the same task.
I observed the CPU usage and it looks like the new app is using less CPU and getting very few threads while the old one gets lots of threads for the same task. PS: I am using the same device.
What could cause this? Any ideas or suggestions to find out?
Thanks.
Finally, I found the problem. It was caused by
Optimization Level
setting in XcodeBuild Settings
. When a new project created, defaultDebug
optimization level isnone
, andRelease
optimization level isFastest, Smallest [-Os]
So when I changed Debug toFastest, Smallest [-Os]
my task completion time dropped to 1 sec.From Apple:
If you want to read more about optimization levels and performance: Tuning for Performance and Responsiveness
Side note: Changing the optimization level to fastest, Smallest [-0s] in debug mode might affect the debugger breakpoints and it will behave abruptly.
Cheers.