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=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 2A63FC3A5A2 for ; Tue, 3 Sep 2019 16:05:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 09C6622CF8 for ; Tue, 3 Sep 2019 16:05:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729935AbfICQFv (ORCPT ); Tue, 3 Sep 2019 12:05:51 -0400 Received: from foss.arm.com ([217.140.110.172]:39712 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729709AbfICQFu (ORCPT ); Tue, 3 Sep 2019 12:05:50 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5FC3E360; Tue, 3 Sep 2019 09:05:50 -0700 (PDT) Received: from [10.1.194.37] (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AAC203F246; Tue, 3 Sep 2019 09:05:48 -0700 (PDT) Subject: Re: [PATCH 2/2] sched/debug: add sched_update_nr_running tracepoint To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Dave Hansen , Steven Rostedt , "H. Peter Anvin" , Andy Lutomirski , =?UTF-8?Q?Jirka_Hladk=c3=bd?= , =?UTF-8?B?SmnFmcOtIFZvesOhcg==?= , x86@kernel.org, Qais Yousef References: <20190903154340.860299-1-rkrcmar@redhat.com> <20190903154340.860299-3-rkrcmar@redhat.com> From: Valentin Schneider Message-ID: Date: Tue, 3 Sep 2019 17:05:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190903154340.860299-3-rkrcmar@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/09/2019 16:43, Radim Krčmář wrote: > The paper "The Linux Scheduler: a Decade of Wasted Cores" used several > custom data gathering points to better understand what was going on in > the scheduler. > Red Hat adapted one of them for the tracepoint framework and created a > tool to plot a heatmap of nr_running, where the sched_update_nr_running > tracepoint is being used for fine grained monitoring of scheduling > imbalance. > The tool is available from https://github.com/jirvoz/plot-nr-running. > > The best place for the tracepoints is inside the add/sub_nr_running, > which requires some shenanigans to make it work as they are defined > inside sched.h. > The tracepoints have to be included from sched.h, which means that > CREATE_TRACE_POINTS has to be defined for the whole header and this > might cause problems if tree-wide headers expose tracepoints in sched.h > dependencies, but I'd argue it's the other side's misuse of tracepoints. > > Moving the import sched.h line lower would require fixes in s390 and ppc > headers, because they don't include dependecies properly and expect > sched.h to do it, so it is simpler to keep sched.h there and > preventively undefine CREATE_TRACE_POINTS right after. > > Exports of the pelt tracepoints remain because they don't need to be > protected by CREATE_TRACE_POINTS and moving them closer would be > unsightly. > Pure trace events are frowned upon in scheduler world, try going with trace points. Qais did something very similar recently: https://lore.kernel.org/lkml/20190604111459.2862-1-qais.yousef@arm.com/ You'll have to implement the associated trace events in a module, which lets you define your own event format and doesn't form an ABI :).