From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754889Ab2BHPXk (ORCPT ); Wed, 8 Feb 2012 10:23:40 -0500 Received: from mail-lpp01m010-f46.google.com ([209.85.215.46]:63719 "EHLO mail-lpp01m010-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752427Ab2BHPXj convert rfc822-to-8bit (ORCPT ); Wed, 8 Feb 2012 10:23:39 -0500 MIME-Version: 1.0 In-Reply-To: <20120208152200.GC25473@somewhere.redhat.com> References: <20120206132546.GA30854@quad> <20120208150715.GB25473@somewhere.redhat.com> <20120208152200.GC25473@somewhere.redhat.com> Date: Wed, 8 Feb 2012 16:23:37 +0100 Message-ID: Subject: Re: [BUG] perf: perf sched warning possibly due to clock granularity on AMD From: Stephane Eranian To: Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, acme@redhat.com, peterz@infradead.org, mingo@elte.hu, robert.richter@amd.com, eric.dumazet@gmail.com X-System-Of-Record: true Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 8, 2012 at 4:22 PM, Frederic Weisbecker wrote: > On Wed, Feb 08, 2012 at 04:10:24PM +0100, Stephane Eranian wrote: >> On Wed, Feb 8, 2012 at 4:07 PM, Frederic Weisbecker wrote: >> > On Mon, Feb 06, 2012 at 02:25:46PM +0100, Stephane Eranian wrote: >> >> Hi, >> >> >> >> I am running 3.3.30-rc2 on an AMD Bulldozer system in 64-bit mode. >> >> I was testing perf sched and I ran into an issue. That issue seems >> >> to exist only on AMD and not on Intel systems. It is not PMU related >> >> because I am doing tracing. >> >> >> >> I am running a simple ping pong test to stress the context switch >> >> code. Two processes exchanging a byte through a pipe (program provided >> >> below). >> >> >> >> Then, I capture a trace using perf sched, and I run sched lat, but >> >> on certain runs, I get: >> >> >> >>    $ perf sched rec pong 2 >> >>    $ perf sched lat >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: Timestamp below last timeslice flush >> >>      Warning: TimesFound 4934 unknown events! >> >>      Is this an older tool processing a perf.data file generated by a more recent tool? >> > >> > I've tried to reproduce this on an AMD phenom but haven't got any such >> > warning. >> > >> It does not happen at each run. > > Yeah I tried 5 times but wasn't lucky. That's not enough! > >> >> > Is there any chance you could "perf archive" your data and upload it somewhere >> > I can fetch it from? >> > >> I can send you the perf.data in a private Email. > > Thanks! Will dig it up and send it to you.