Subject: Re: [RT] [RFC] simple SMI detector
From: Jon Masters <jcm@redhat.com>
To: Mike Kravetz <kravetz@us.ibm.com>
Cc: linux-rt-users@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
       williams <williams@redhat.com>,
       "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
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	 <20090125225205.GA3783@monkey.beaverton.ibm.com>
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Organization: Red Hat, Inc.
Date: Mon, 26 Jan 2009 12:51:12 -0500
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On Sun, 2009-01-25 at 14:52 -0800, Mike Kravetz wrote:

> Any reason why you could not do SMI detection in user level code running
> at the highest RT priority?

Yeah. I had some suggestions about that already...the problem with that
is that you can't know whether measured latencies are due to SMIs /or/
other kernel latencies - maybe there's a bug or other problem? I really
want to be able to say to vendors "nope, it's definitely your problem".

So I think what'll end up happening is a user process for ease of
deployment but something like smi_detector for advanced diagnostics. And
then I just hope others will write tools like the one IBM already has
that will turn off extraneous SMI generation :)

Jon.


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