Re: ppc: RECLAIM_DISTANCE 10?

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.