From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934192AbXC0TQf (ORCPT ); Tue, 27 Mar 2007 15:16:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934193AbXC0TQf (ORCPT ); Tue, 27 Mar 2007 15:16:35 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:44730 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934192AbXC0TQe (ORCPT ); Tue, 27 Mar 2007 15:16:34 -0400 Date: Tue, 27 Mar 2007 21:15:48 +0200 From: Ingo Molnar To: Steven Rostedt Cc: LKML , Roland Dreier Subject: Re: [PATCH -rt] fix setting of preempt_max_latency and preempt_thresh on 64 bit systems Message-ID: <20070327191548.GC29929@elte.hu> References: <1175015947.19634.6.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1175015947.19634.6.camel@localhost.localdomain> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > Ingo, > > I wasn't able to turn on latency tracing on a x86_64 box. Using logdev > to see what was happening, I found that echoing 0 into > /proc/sys/kernel/preempt_max_latency would only change the max from > -1ULL to 0xffffffff00000000. Which would keep the max pretty high > still. ah! This should explain Roland Dreier's report about tracing not working on x86_64. > The problem is in sysctl.c where preempt_max_latency can be modified. > On systems where cycle_t is greater than the size of int (x86_64) we > only write to the 4 LSB. > > Here's the patch: thanks, applied. Ingo