Re: ppc: RECLAIM_DISTANCE 10?

Michal Hocko
2014-02-19T09:20:09Z

On Wed 19-02-14 00:20:21, David Rientjes wrote:
> On Wed, 19 Feb 2014, Michal Hocko wrote:
>
> > > I strongly suspect that the patch is correct since powerpc node distances
> > > are different than the architectures you're talking about and get doubled
> > > for every NUMA domain that the hardware supports.
> >
> > Even if the units of the distance is different on PPC should every NUMA
> > machine have zone_reclaim enabled? That doesn't right to me.
> >
>
> In my experience on powerpc it's very correct, there's typically a
> significant latency in remote access and we don't have the benefit of a
> SLIT that actually defines the locality between proximity domains like we
> do on other architectures.

Interesting. So is the PPC NUMA basically about local vs. very distant?
Should REMOTE_DISTANCE reflect that as well? Or can we have
distance < REMOTE_DISTANCE and it would still make sense to have
zone_reclaim enabled?

[...]

Thanks!
--
Michal Hocko
SUSE Labs