Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default

[Rik van Riel]

KOSAKI Motohiro wrote:
> Subject: [PATCH] zone_reclaim_mode is always 0 by default
>
> Current linux policy is, if the machine has large remote node distance,
>  zone_reclaim_mode is enabled by default because we've be able to assume to 
> large distance mean large server until recently.
>
> Unfrotunately, recent modern x86 CPU (e.g. Core i7, Opeteron) have P2P transport
> memory controller. IOW it's NUMA from software view.
>
> Some Core i7 machine has large remote node distance and zone_reclaim don't
> fit desktop and small file server. it cause performance degression.
>
> Thus, zone_reclaim == 0 is better by default. sorry, HPC gusy. 
> you need to turn zone_reclaim_mode on manually now.

I'll believe that it causes a performance regression with the
old zone_reclaim behaviour, however the way you tweaked
zone_reclaim should make it behave a lot better, no?

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