IOS 11.3 I'm experiencing a definite lag whilst using a thread (even one with NSQualityOfServiceUserInteractive) with high activity (5ms processing)
Start the loop here
NSOperationQueue *q = [[NSOperationQueue alloc] init];
q.qualityOfService=NSQualityOfServiceUserInteractive; // highest priority
[q addOperationWithBlock: ^{
[self runRackPanelLoopThread];
}];
Then runRackPanelLoopThread sits in a while loop looking at CACurrentMediaTime() & measuring intervals to fire off events.
But, when my app switches to background the thread created glitches - it gets starved of cpu (you can see it drop even with the xcode cpu monitor).
Stack trace with pointers shows a definite gap during this glitch ( nice and regular when in foregound).
I've tried many forms of dispatch but all the same, the only method I have that works is an AudioUnit callback to call my processing, but thats limited to about 23ms.
I can't run my processing on the main thread as it kills the app, and dispatch to main queue also kills it - it has to be in non-gcd code.
Is there a bug with IOS11 that means any GCD threads are preempted for a long time (I've seen up to .25 seconds) whilst in background and the system is being loaded.
I should point out that this is really bad on A7 devices, but less noticeable as you improve the cpu (doesn't happen on ipad pro)
What should I be looking for?
regards
Tony
