Hi, I confirm it is a serial queue and the dispatch_async_f() call is not made on the same queue. I used CACurrentMediaTime() instead of clock() but the duration still increases. It grows from 0 to 3ms over 3 minutes of rendering.

Hi, I confirm the functions pushed to the queue do run. If I randomly pause execution, I land in that dispatch_async_f() call 50% of the time. The other 50% I land on a Metal call (Create Command Buffer) which duration also increases over time. This Metal call is not made on a dispatch queue. It runs on the same thread than dispatch_async_f.

Thanks! That fixed the issue. Is our game doing something wrong to cause this?