Re: [PATCH] cpusets - big numa cpu and memory placement

Matthew Dobson
2004-10-09T00:23:29Z

On Thu, 2004-10-07 at 13:12, Hubertus Franke wrote:
> The way this is heading is quite promising.
> - sched_domains seems the right answer wrt to partitioning the machine.
> Given some boot option or dynamic means one can shift cpus from
> on domain to the next domain.
> - If I understood correctly, there would be only one level of such
> hard partitioning, speak exclusive cpu-set or sched_domain.
> - In each such domain/set we allow shared *use*.

I don't think that there needs to be a requirement that we have only one
level of hard partitioning. The rest of your points are valid though,
Hubertus.

It'd be really nice if we could all get together with a wall of
whiteboards, some markers, and a few pots of coffee. I think we'd all
get this pretty much hashed out in an hour or two. This isn't directed
at you, Hubertus, but at the many communication breakdowns in this
thread.

> First, one needs to understand that sched_domains are nothing else
> but a set of cpus that are considered during load balancing times.
> By constricting the top_domain to the respective exclusive set one
> essentially has accomplished the desired feature of partitioning
> the machines into "isolated" sections (here from cpu perspective).
> So it is quite possible that an entire domain is empty based, while
> another exclusive domain would be totally overloaded.

I think that is very well stated, Hubertus. By having a more or less
passive data structure that is only checked at load balance time, we can
ensure (in a very light-weight way) that no task ever moves *out* of
it's area nor moves *into* someone else's area.

-Matt