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SubjectRe: [PATCH resend^2] mm: increase RECLAIM_DISTANCE to 30
Date

>> Recently, Robert Mueller reported zone_reclaim_mode doesn't work
>> properly on his new NUMA server (Dual Xeon E5520 + Intel S5520UR MB).
>> He is using Cyrus IMAPd and it's built on a very traditional
>> single-process model.
>>
>
> Let's add Robert to the cc to see if this is still an issue, it hasn't
> been re-reported in over six months.

We definitely still set this in /etc/sysctl.conf on every imap server
machine:

vm.zone_reclaim_mode = 0

I believe it still defaults to 1 otherwise. What I haven't tested is if
leaving it at 1 still causes problems. It definitely DID previously cause
big problems (I think that was around 2.6.34 or so).

http://blog.fastmail.fm/2010/09/15/default-zone_reclaim_mode-1-on-numa-kernel-is-bad-for-fileemailweb-servers/

I'll try changing it to 1 on a machine for 4 hours, see if it makes a
noticeable difference and report back.

Rob



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