linux-kernel - Re: [PATCH 3/3] x86: fix node_possible

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Message-ID: <20090512071531.GF19296@one.firstfloor.org>
Date:	Tue, 12 May 2009 09:15:31 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	David Rientjes <rientjes@...gle.com>,
	Jack Steiner <steiner@....com>,
	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] x86: fix node_possible_map logic -v2

> Should it?  It seems to me that CPUs 0-1 should be antipreferentially 
> scheduled, 

You could do that, but the question is if it matters. It would
only make a difference on systems which are not fully loaded, 
and it's unclear how much.

And at some point you need to use these cores anyways; usually it's much
worse to not use a CPU and overload others than to use it with slower memory.

Is it worth adding a lot of fixes all over hte kernel? Not clear
to me.

Also it's a obscure situation and it affects a lot of code, so you
would likely have to continuously fight with regressions as Jack
has discovered.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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