linux-kernel - Re: [PATCH 5/7] perf: Optimise topology iteration

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Message-ID: <20110103152025.GB25713@one.firstfloor.org>
Date:	Mon, 3 Jan 2011 16:20:25 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>, robert.richter@....com,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7] perf: Optimise topology iteration

On Mon, Jan 03, 2011 at 12:02:10PM +0100, Peter Zijlstra wrote:
> On Mon, 2010-12-27 at 23:38 +0800, Lin Ming wrote:
> > Currently we iterate the full machine looking for a matching core_id/nb
> > for the percore and the amd northbridge stuff , using a smaller topology
> > mask makes sense. 
> 
> Does topology_thread_cpumask() include offline cpus? I tried looking at
> it, but I cannot find any code clearing bits in that mask on offline.

The problem is not only at offline, but also at online between CPUs
going online.  I don't think the patch is a good idea and it doesn't
even have any advantages either since this is a initialization only
slow path.

-Andi
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