From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262236AbVGKFDh (ORCPT ); Mon, 11 Jul 2005 01:03:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262240AbVGKFDh (ORCPT ); Mon, 11 Jul 2005 01:03:37 -0400 Received: from mx2.elte.hu ([157.181.151.9]:14266 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S262236AbVGKFDg (ORCPT ); Mon, 11 Jul 2005 01:03:36 -0400 Date: Mon, 11 Jul 2005 07:03:03 +0200 From: Ingo Molnar To: Serge Noiraud Cc: linux-kernel Subject: Re: PREEMPT_RT and latency_trace Message-ID: <20050711050303.GA13190@elte.hu> References: <1120826951.6225.167.camel@ibiza.btsn.frna.bull.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1120826951.6225.167.camel@ibiza.btsn.frna.bull.fr> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Serge Noiraud wrote: > Hi, > > I have a big dilemna on one machine : > I run a task with RT priority which make a loop to mesure the system > perturbation. > It works well except on one machine. > On a multi-cpu, If I run the program on cpu 1, I get 23us. It's OK. > If I run the same program on cpu 0, I get 17373us ! could you try the -51-24 (or later) kernel, does it have any better latencies? It has a PI fix that fixes the recent priority leakage observed on SMP systems. The priority leakage can lead to excessive delays in RT apps. Ingo