From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BAD2C433E0 for ; Fri, 31 Jul 2020 17:20:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 074E122B3F for ; Fri, 31 Jul 2020 17:20:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="LrZ1HXS6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387499AbgGaRU1 (ORCPT ); Fri, 31 Jul 2020 13:20:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729944AbgGaRU1 (ORCPT ); Fri, 31 Jul 2020 13:20:27 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38EEEC061574 for ; Fri, 31 Jul 2020 10:20:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=6BEQZGFz2zyuCgyEWRRLllezcZ3YAqzZtIi2etzzWTQ=; b=LrZ1HXS6ViVyE0DVAAxdJiejyl cW+KEbW1oIx22XnqVTnPeI5ujto/D4SotYTJ6deM5ly0wsy55hWHeXGOq3wlh317U3TIYyJCvJquB kcnvrgcR6JFdj3OASMJWcFdPRKP3Q3flMKHMdkUP8j7TU0c1m4I4PE7qZZnrpRCch/mz1lFAPT55m 543U9IBFMMuMlcYF7hiTt2jK0PULpqTghGr0lnBIAaBeGIIbSHGSyO3GZ7fLXvzlWgEW5IricnjSq Vus25K8dz3GJ/6egXFsoaC584e/iOEGdxqbrW/enwZc1ouS6erSc6Yc0LLaNm71/7mrBri9R+IaQJ /kd48RzQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k1YhV-0005y4-Ne; Fri, 31 Jul 2020 17:20:09 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 4A1993050F0; Fri, 31 Jul 2020 19:20:06 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 15627203C0A49; Fri, 31 Jul 2020 19:20:06 +0200 (CEST) Date: Fri, 31 Jul 2020 19:20:06 +0200 From: peterz@infradead.org To: David Ahern Cc: Jiri Olsa , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Namhyung Kim , Alexander Shishkin , Michael Petlan , Ian Rogers , Andi Kleen , =?iso-8859-1?Q?Genevi=E8ve?= Bastien , Wang Nan , Jeremie Galarneau Subject: Re: [PATCH 0/6] perf tools: Add wallclock time conversion support Message-ID: <20200731172006.GJ2638@hirez.programming.kicks-ass.net> References: <20200730213950.1503773-1-jolsa@kernel.org> <20200730221423.GH2638@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 30, 2020 at 07:21:54PM -0600, David Ahern wrote: > On 7/30/20 4:14 PM, peterz@infradead.org wrote: > > On Thu, Jul 30, 2020 at 11:39:44PM +0200, Jiri Olsa wrote: > > > >> The patchset is adding the ability to display TOD/wallclock timestamp > >> in 'perf script' output and in 'perf data convert --to-ctf' subcommand, > >> so the converted CTF data contain TOD/wallclock timestamps. > > > > But why? Wallclock is a horrible piece of crap. Why would you want to do > > this? > > > > Same reason I brought this up 9+ years ago: userspace lives on > time-of-day, and troubleshooting is based on correlating timestamps from > multiple sources. To correlate a perf event to syslog or an application > log, we need time-of-day. You need a sync'ed CLOCK_MONOTONIC for that, CLOCK_REALTIME 'aka' wallclock is a trainwreck, you don't ever want that.