Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932087AbWBJNQ4 (ORCPT ); Fri, 10 Feb 2006 08:16:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932088AbWBJNQ4 (ORCPT ); Fri, 10 Feb 2006 08:16:56 -0500 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:5547 "EHLO ecfrec.frec.bull.fr") by vger.kernel.org with ESMTP id S932087AbWBJNQz convert rfc822-to-8bit (ORCPT ); Fri, 10 Feb 2006 08:16:55 -0500 Subject: Re: preempt-rt, NUMA and strange latency traces From: =?ISO-8859-1?Q?S=E9bastien_Dugu=E9?= To: Lee Revell Cc: Steven Rostedt , "linux-kernel@vger.kernel.org" , Ingo Molnar In-Reply-To: <1139515365.30058.91.camel@mindpipe> References: <1139311689.19708.36.camel@frecb000686> <1139395534.21471.13.camel@frecb000686> <1139465045.30058.31.camel@mindpipe> <1139484275.5706.19.camel@frecb000686> <1139515365.30058.91.camel@mindpipe> Date: Fri, 10 Feb 2006 14:18:54 +0100 Message-Id: <1139577535.5706.81.camel@frecb000686> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 X-MIMETrack: Itemize by SMTP Server on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 10/02/2006 14:16:49, Serialize by Router on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 10/02/2006 14:17:58, Serialize complete at 10/02/2006 14:17:58 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1661 Lines: 43 On Thu, 2006-02-09 at 15:02 -0500, Lee Revell wrote: > On Thu, 2006-02-09 at 12:24 +0100, S?bastien Dugu? wrote: > > On Thu, 2006-02-09 at 01:04 -0500, Lee Revell wrote: > > > On Wed, 2006-02-08 at 11:45 +0100, S?bastien Dugu? wrote: > > > > The more I think about it, the more I tend to believe it's hardware > > > > related. It seems as if the CPU just hangs for ~27 ms before > > > > resuming processing. > > > > > > That would be an exceptionally long latency - you would probably notice > > > it if the mouse froze, VOIP dropped out, ping stops, etc for 30ms. > > > > > > > It's a test machine and I use it remotely with console redirected so > > no mouse, no RT applications aside from my silly nanosleep() loop. But > > I do notice that that test sometimes takes more time (ie when I get > > those weird latencies). > > Argh. You would think the vendors would consider a 30ms delay > unacceptable. This is big enough to show up on an MRTG graph of ping > times ferchrissake. > > I guess the assumption is that most hardware will never be used for even > soft RT work... > > Lee > That may be but in that case I may be pushing it a bit far testing that kind of box with realtime stuff. As a former hw designer I find it useful to have some hardware monitoring capabilities on a system but it should either not be so intrusive or at least we should be able to disable it. S?bastien. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/