iOS 11 CPU throttling and idle timer

Question

On an iPhone SE, after an upgrade to iOS 11.4, I am now seeing a very strange CPU throttling result after about 8-10 seconds. I am using a very simple example app with (Depl

Answer 1

This may be relevant to your experience: we found that the act of profiling an app could fool these versions of iOS into downclocking when it was not appropriate. The problem did not occur in release builds not connected to the host PC.

We had an app whose render-loop ran in just under 8ms - well under the ~16ms needed for 60fps gameplay. When connected to the profiler, the target device would detect this and downclock - but the overhead of communicating with the profiler would push the frame time over 16ms, resulting in 30fps gameplay.

We found no solution to this other than recognising that it was happening and taking it into account. When we added additional render load to the app, pushing it past 8ms, the problem went away because the target device no longer downclocked.