Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754938AbZCQP2T (ORCPT ); Tue, 17 Mar 2009 11:28:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752748AbZCQP2E (ORCPT ); Tue, 17 Mar 2009 11:28:04 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:50907 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751915AbZCQP2C (ORCPT ); Tue, 17 Mar 2009 11:28:02 -0400 Date: Tue, 17 Mar 2009 16:27:53 +0100 From: Ingo Molnar To: Miklos Szeredi , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Peter Zijlstra Cc: rostedt@goodmis.org, linux-kernel@vger.kernel.org Subject: Re: wrong timestamps in ftrace? Message-ID: <20090317152753.GD13895@elte.hu> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 40 * Miklos Szeredi wrote: > I've started playing with ftrace and timestamps seem to be > misbehaving. > > # echo 0 > /sys/kernel/debug/tracing/tracing_enabled > # echo nop > /sys/kernel/debug/tracing/current_tracer > # echo 131072 > /sys/kernel/debug/tracing/buffer_size_kb > # echo sched_switch > /sys/kernel/debug/tracing/current_tracer > # echo 1 > /sys/kernel/debug/tracing/tracing_enabled > # sleep 10 > # echo 0 > /sys/kernel/debug/tracing/tracing_enabled > # cat /sys/kernel/debug/tracing/trace > /tmp/trace.txt > # ls -lh /tmp/trace.txt > -rw-r--r-- 1 root root 96K Mar 17 16:11 /tmp/trace.txt > # head -5 /tmp/trace.txt | tail -1 > bash-4908 [001] 212.139730: 4908:120:S + [001] 4845:120:S > # tail -1 /tmp/trace.txt > kondemand/1-1020 [001] 212.261054: 1020:115:S ==> [001] 0:140:R > > So according to the timestamps the time difference between the first > and last event was just 0.12s, which is rubbish. > > This is latest git on a CoreDuo T60 notebook. Attaching .config and > dmesg. There's been changes to timestamping in the tracing tree. Could you check whether latest -tip: http://people.redhat.com/mingo/tip.git/README works better for you? Ingo -- 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/