linux-kernel - Re: [PATCH 00/10] x86: Reduce memory and intra-node effects with large count NR

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Message-ID: <20080114081418.GB18296@elte.hu>
Date:	Mon, 14 Jan 2008 09:14:18 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	travis@....com
Cc:	Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <ak@...e.de>,
	Christoph Lameter <clameter@....com>,
	Jack Steiner <steiner@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/10] x86: Reduce memory and intra-node effects with
	large count NR_CPUs


* travis@....com <travis@....com> wrote:

> This patchset addresses the kernel bloat that occurs when NR_CPUS is 
> increased. The memory numbers below are with NR_CPUS = 1024 which I've 
> been testing (4 and 32 real processors, the rest "possible" using the 
> additional_cpus start option.) These changes are all specific to the 
> x86 architecture, non-arch specific changes will follow.

thanks, i'll try this patchset in x86.git.

> 32cpus			  1kcpus-before		    1kcpus-after
>    7172678 Total	   +23314404 Total	       -147590 Total

1kcpus-after means it's +23314404-147590, i.e. +23166814? (i.e. a 0.6% 
reduction of the bloat?)

i.e. we've got ~22K bloat per CPU - which is not bad, but because it's a 
static component, it hurts smaller boxes. For distributors to enable 
CONFIG_NR_CPU=1024 by default i guess that bloat has to drop below 1-2K 
per CPU :-/ [that would still mean 1-2MB total bloat but that's much 
more acceptable than 23MB]

	Ingo
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