Date: Mon, 6 Feb 2006 09:40:01 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Paul Jackson <pj@sgi.com>
Cc: akpm@osdl.org, dgc@sgi.com, steiner@sgi.com, Simon.Derr@bull.net,
       ak@suse.de, linux-kernel@vger.kernel.org, clameter@sgi.com
Subject: Re: [PATCH 1/5] cpuset memory spread basic implementation
Message-ID: <20060206084001.GA5600@elte.hu>
References: <20060204071910.10021.8437.sendpatchset@jackhammer.engr.sgi.com> <20060204154944.36387a86.akpm@osdl.org> <20060205203358.1fdcea43.akpm@osdl.org> <20060205215052.c5ab1651.pj@sgi.com> <20060205220204.194ba477.akpm@osdl.org> <20060206061743.GA14679@elte.hu> <20060205232253.ddbf02d7.pj@sgi.com> <20060206074334.GA28035@elte.hu> <20060206001959.394b33bc.pj@sgi.com> <20060206082258.GA1991@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> > We normally run with different policies, in the same box, on different 
> > cpusets at the same time.  But this might be because some cpusets 
> > -need- the memory spreading, and the others that don't are left to the 
> > default policy.
> 
> so in practice, the memory spreading is in fact a global setting, used 
> by all cpusets that matter? That seems to support Andrew's observation 
> that our assumptions / defaults are bad, pretty much independently of 
> the workload.

in other words: the spreading out likely _hurts_ performance in the 
typical case (which prefers node-locality), but when you are using 
multiple cpusets you want to opt for fairness between projects, over 
opportunistic optimizations such as node-local allocations. I.e. the 
spreading out, as it is used today, is rather a global fairness setting 
for the kernel, and not really a workload-specific access-pattern thing.  
Right?

	Ingo
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