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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 C5596C433DF for ; Tue, 30 Jun 2020 03:26:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95FCB206A5 for ; Tue, 30 Jun 2020 03:26:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729133AbgF3D04 (ORCPT ); Mon, 29 Jun 2020 23:26:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:40662 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728949AbgF3D0z (ORCPT ); Mon, 29 Jun 2020 23:26:55 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 82E94206B6; Tue, 30 Jun 2020 03:26:53 +0000 (UTC) Date: Mon, 29 Jun 2020 23:26:52 -0400 From: Steven Rostedt To: Mathieu Desnoyers Cc: linux-kernel , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Masami Hiramatsu , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Yordan Karadzhov , Tzvetomir Stoyanov , Tom Zanussi , Jason Behmer , Julia Lawall , Clark Williams , bristot , Daniel Wagner , Darren Hart , Jonathan Corbet , "Suresh E. Warrier" , "Joel Fernandes, Google" Subject: Re: [RFC][PATCH] ring-buffer: Have nested events still record running time stamp Message-ID: <20200629232652.5872c966@oasis.local.home> In-Reply-To: <650783164.16607.1593486812734.JavaMail.zimbra@efficios.com> References: <20200625094454.732790f7@oasis.local.home> <1548518134.13177.1593107707149.JavaMail.zimbra@efficios.com> <20200625143525.2f3a2902@oasis.local.home> <79426976.13417.1593113702719.JavaMail.zimbra@efficios.com> <20200629202146.29520925@oasis.local.home> <650783164.16607.1593486812734.JavaMail.zimbra@efficios.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 29 Jun 2020 23:13:32 -0400 (EDT) Mathieu Desnoyers wrote: > -> This configuration's avg varies between 239 and 256 ns based on your benchmark methodology. The std. dev. varies between > 138 and 201 ns. > > In the benchmark results you collected, config #1 appeared to have little delta between xadd and cmpxchg, whereas > config #2 and #3 had some avg difference. Did you try running this test many times on each machine to see if the > result was indeed stable ? Yes, but as we discussed on IRC, my machines are much smaller than this one, and that makes it a bit more deterministic. I also run them with distro configs. When there's debugging enabled, I get much more erratic results. -- Steve