Re: [RFD] sched/deadline: Support single CPU affinity

From: Tommaso Cucinotta
Date: Thu Dec 15 2016 - 06:30:50 EST

Hi Peter,

On 13/12/2016 11:21, Peter Zijlstra wrote:
On Thu, Nov 10, 2016 at 11:01:59AM +0100, Tommaso Cucinotta wrote:
Just a note: if you want to recover arbitrary task affinities, you can re-cast your above test like this:

\sum U[t]/A[t] \leq 1 (or U_max), for each task t on cpu, with utilization U[t] and A[t] tasks overall in its affinity mask

Do I read it correct when I interpret A[t] as the number of CPUs in its
affinity mask?

yes, exactly, A[t] number of CPUs in the task affinity mask (sorry for my bad write-up)

Also, does recoverable mean a bound tardiness, or is that something
weaker still?

nope, nothing exact -- it just meant providing flexible but simple & consistent (ie, towards recovering affinity masks) options from the kernel/scheduler side, leaving more complex & exact tests to user-space, or future add-ons to the kernel.