On Wed 19-02-14 00:20:21, David Rientjes wrote:

On Wed, 19 Feb 2014, Michal Hocko wrote:

quoted

quoted

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