OK, let me get this straight: 1) Your application has a deadline. 2) You do not tell the kernel of that deadline. 3) You want to know if the kernel will keep the promise you never told it about?
Yes. All I am saying is that by keeping a *sched_wakeup_granularity_ns *parameter as 2.5 ms. A process which is waken up has to wait for that much amount of time if any other (non-important) process is executing. Now I am saying that the way CFS seems to be designed it will never make a process which wakes up and has a deadline < 2.5 ms meet its deadline. Now why does this scenario matter. This may occur in real workloads like video processing etc. I do not want any guarantee that CFS will meet deadline that I did not even give it (or its not even aware of). But one sure would like a guarantee that CFS surely will not fail all the time in such scenarios (which is my claim). Is that really your question? I hope the question makes sense now.