Date: Mon, 6 Feb 2006 11:23:37 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <ak@suse.de>
Cc: Paul Jackson <pj@sgi.com>, akpm@osdl.org, dgc@sgi.com, steiner@sgi.com,
       Simon.Derr@bull.net, linux-kernel@vger.kernel.org, clameter@sgi.com
Subject: Re: [PATCH 1/5] cpuset memory spread basic implementation
Message-ID: <20060206102337.GA3359@elte.hu>
References: <20060204071910.10021.8437.sendpatchset@jackhammer.engr.sgi.com> <200602061109.45788.ak@suse.de> <20060206101156.GA1761@elte.hu> <200602061116.44040.ak@suse.de>
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* Andi Kleen <ak@suse.de> wrote:

> On Monday 06 February 2006 11:11, Ingo Molnar wrote:
> > 
> > * Andi Kleen <ak@suse.de> wrote:
> > 
> > > Of course there might be some corner cases where using local memory 
> > > for caching is still better (like mmap file IO), but my guess is that 
> > > it isn't a good default.
> > 
> > /tmp is almost certainly one where local memory is better.
> 
> Not sure. What happens if someone writes a 1GB /tmp file on a 1GB 
> node?

well, if the pagecache is filled on a node above a certain ratio then 
one would have to spread it out forcibly. But otherwise, try to keep 
things as local as possible, because that will perform best. This is 
different from the case Paul's patch is addressing: workloads which are 
known to be global (and hence spreading out is the best-performing 
allocation).

(for which problem i suggested a per-mount/directory/file 
locality-of-reference attribute in another post.)

	Ingo
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