From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Revell Subject: Re: [RT] [RFC] simple SMI detector Date: Mon, 26 Jan 2009 21:23:45 -0500 Message-ID: <75b66ecd0901261823o72339347kfa70d6e54f61af00@mail.gmail.com> References: <1232751312.3990.59.camel@perihelion.bos.jonmasters.org> <20090125225205.GA3783@monkey.beaverton.ibm.com> <1232992272.19862.3.camel@londonpacket.bos.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Mike Kravetz , linux-rt-users@vger.kernel.org, LKML , williams , "Luis Claudio R. Goncalves" To: Jon Masters Return-path: Received: from rv-out-0506.google.com ([209.85.198.234]:16692 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751977AbZA0CXq (ORCPT ); Mon, 26 Jan 2009 21:23:46 -0500 In-Reply-To: <1232992272.19862.3.camel@londonpacket.bos.redhat.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Mon, Jan 26, 2009 at 12:51 PM, Jon Masters wrote: > 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". Can't you do this with a known good version of the -rt kernel and the latency tracer in full RT preempt mode? SMI induced latency will show up in the trace as long delays in random code paths where kernel induced latency can be ruled out. Lee