Re: [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities

Valentin Schneider
2020-04-14T14:29:28Z

On 14/04/20 12:40, Qais Yousef wrote:
>
> I haven't followed this discussion closely, so I could be missing something
> here.
>
> In sched_cpu_dying() we call set_rq_offline() which clears the cpu in
> rq->rd->online.
>
> So the way I read the code
>
> rd->online = cpumask_and(rd->span, cpu_active_mask)
>
> But I could have easily missed some detail.
>

sched_cpu_dying() is wayyyy below sched_cpu_deactivate(). This doesn't help
at all for the dl_cpu_busy() check in sched_cpu_deactivate().

> Regardless, it seems to me that DL is working around something not right in the
> definition of rd->span or using the wrong variable.
>

What DL is doing now is fine, it only needs to be aligned with the active
mask (which it is). We're making things a bit trickier by adding capacity
values into the mix.

> My 2p :-). I have to go back and read the discussion in more detail.
>
> Thanks