Re: ppc: RECLAIM_DISTANCE 10?

David Rientjes
2014-02-19T21:45:18Z

On Wed, 19 Feb 2014, Michal Hocko wrote:

> Interesting. So is the PPC NUMA basically about local vs. very distant?

The point is that it's impossible to tell how distant they are from one
NUMA domain to the next NUMA domain.

> 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?
>

Ppc doesn't want to allocate in a different NUMA domain unless required,
the latency of a remote access is too high. Everything that isn't in the
same domain has a distance >10 and is setup as 2^(domain hops) * 10. We
don't have the ability like with a SLIT to define remote nodes to have
local latency vs remote or costly latency so the safe setting is a
RECLAIM_DISTANCE of 10.