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Date: Wed, 27 Feb 2008 13:45:18 +0900
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: balbir@linux.vnet.ibm.com
Subject: Re: [RFC][PATCH] page reclaim throttle take2
Cc: kosaki.motohiro@jp.fujitsu.com, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Rik van Riel <riel@redhat.com>,
       Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
       Nick Piggin <npiggin@suse.de>
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Hi

> One more thing, I would request you to add default heuristics (number of
> reclaimers), based on the number of cpus in the system. Letting people tuning it
> is fine, but defaults should be related to number of cpus, nodes and zones on
> the system. Zones can be reaped in parallel per node and cpus allow threads to
> run in parallel. So please use that to come up with good defaults, instead of a
> number like "3".

I don't think so.
all modern many cpu machine stand on NUMA.
it mean following,
 - if cpu increases, then zone increases, too.

if default value increase by #cpus, lock contension dramatically increase
on large numa.

Have I overlooked anything?


and, (but) i afraid to 3 is too small value.
if you have another test result on large machine, please show me.

- kosaki