Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754553AbaAASiH (ORCPT ); Wed, 1 Jan 2014 13:38:07 -0500 Received: from mail-pb0-f44.google.com ([209.85.160.44]:49502 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754235AbaAASiE (ORCPT ); Wed, 1 Jan 2014 13:38:04 -0500 Message-ID: <52C46083.9070605@gmail.com> Date: Wed, 01 Jan 2014 11:37:55 -0700 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Frederic Weisbecker CC: Joseph Schuchart , Ingo Molnar , Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , thomas.ilsche@tu-dresden.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Perf: Correct Assumptions about Sample Timestamps in Passes References: <528490DE.4080204@tu-dresden.de> <20131114100552.GA5064@gmail.com> <528E1EE6.9040407@tu-dresden.de> <20131127135137.GA24403@gmail.com> <52B437AA.4090102@tu-dresden.de> <52B479E1.7020204@gmail.com> <20131223131051.GB585@localhost.localdomain> <52B84C49.70001@gmail.com> <20131226151429.GA15303@localhost.localdomain> <52BC4A13.1090508@gmail.com> <20131226153033.GC15303@localhost.localdomain> In-Reply-To: <20131226153033.GC15303@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1449 Lines: 37 On 12/26/13, 8:30 AM, Frederic Weisbecker wrote: > On Thu, Dec 26, 2013 at 10:24:03AM -0500, David Ahern wrote: >> On 12/26/13, 10:14 AM, Frederic Weisbecker wrote: >>>> I was carrying that patch while working on perf-kvm-stat-live last >>>> Fall. It does not solve the problem for live commands, so ended up >>>> dropping it and going with local (to the command) hacks. I still >>>> think for live commands getting a perf_clock timestamp at the start >>>> of a round and using that as the flush time will work best. For perf-kvm-stat-live using perf_clock value at the start of the round as the flush time works beautifully: https://github.com/dsahern/linux/commit/ba8b7b63d5dbdc95aedbbafa670c2232e0cc07a2 Never once failed with "Warning: Timestamp below last timeslice flush" error. David >>> >>> Ok, but how would you fetch this perf clock timestamp, with an explicit read? >> >> One option is exporting perf_clock to userspace. >> >> Preferably a built-in option, https://lkml.org/lkml/2013/12/10/781, >> but I can go the module route if I have to: >> https://github.com/dsahern/linux/blob/perf-full-monty/README.ahern > > I see, that's one of the very verbose threads I've seen lately ;) > -- 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/