From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261867AbVFVSv4 (ORCPT ); Wed, 22 Jun 2005 14:51:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261884AbVFVSv4 (ORCPT ); Wed, 22 Jun 2005 14:51:56 -0400 Received: from e35.co.us.ibm.com ([32.97.110.133]:49102 "EHLO e35.co.us.ibm.com") by vger.kernel.org with ESMTP id S261867AbVFVStv (ORCPT ); Wed, 22 Jun 2005 14:49:51 -0400 Date: Wed, 22 Jun 2005 11:50:19 -0700 From: "Paul E. McKenney" To: Kristian Benoit Cc: Karim Yaghmour , linux-kernel@vger.kernel.org, bhuey@lnxw.com, andrea@suse.de, tglx@linutronix.de, mingo@elte.hu, pmarques@grupopie.com, bruce@andrew.cmu.edu, nickpiggin@yahoo.com.au, ak@muc.de, sdietrich@mvista.com, dwalker@mvista.com, hch@infradead.org, akpm@osdl.org, Philippe Gerum Subject: Re: PREEMPT_RT vs I-PIPE: the numbers, part 2 Message-ID: <20050622185019.GG1296@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <1119287612.6863.1.camel@localhost> <20050621015542.GB1298@us.ibm.com> <42B77B8C.6050109@opersys.com> <20050622011931.GF1324@us.ibm.com> <42B9845B.8030404@opersys.com> <20050622162718.GD1296@us.ibm.com> <1119460803.5825.13.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1119460803.5825.13.camel@localhost> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 22, 2005 at 01:20:03PM -0400, Kristian Benoit wrote: > On Wed, 2005-06-22 at 09:27 -0700, Paul E. McKenney wrote: > > On Wed, Jun 22, 2005 at 11:31:39AM -0400, Karim Yaghmour wrote: > > > > If I understand your analysis correctly (hah!!!), your breakdown > > of the maximum delay assumes that the maximum delays for the logger > > and the target are correlated. What causes this correlation? > > My (probably hopelessly naive) assumption would be that there would > > be no such correlation. In absence of correlation, one might > > approximate the maximum ipipe delay by subtracting the -average- > > ipipe delay from the maximum preemption delay, for 55us - 7us = 48us. > > Is this the case, or am I missing something here? > > Your analysis is correct, but with 600,000 samples, it is possible that > we got 2 peeks (perhaps not maximum), one on the logger and one on the > target. So in my point of view, the maximum value is probably somewhere > between 55us / 2 and 55us - 7us. And probably closer to 55us / 2. Possible, but it could also be a large peak and a small one. Any way of getting the logger's latency separately? Or the target's? Thanx, Paul