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=-6.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 890FCC433E2 for ; Tue, 8 Sep 2020 17:18:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4FACA20768 for ; Tue, 8 Sep 2020 17:18:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726699AbgIHRSL (ORCPT ); Tue, 8 Sep 2020 13:18:11 -0400 Received: from foss.arm.com ([217.140.110.172]:57126 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731547AbgIHQSP (ORCPT ); Tue, 8 Sep 2020 12:18:15 -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 5ABF01045; Tue, 8 Sep 2020 09:18:08 -0700 (PDT) Received: from [192.168.178.2] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2683E3F66E; Tue, 8 Sep 2020 09:18:07 -0700 (PDT) Subject: Re: [PATCH v2] sched/debug: Add new tracepoint to track cpu_capacity To: Qais Yousef Cc: peterz@infradead.org, vincent.donnefort@arm.com, mingo@redhat.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, valentin.schneider@arm.com, Phil Auld References: <1598605249-72651-1-git-send-email-vincent.donnefort@arm.com> <20200828102724.wmng7p6je2pkc33n@e107158-lin.cambridge.arm.com> <1e806d48-fd54-fd86-5b3a-372d9876f360@arm.com> <20200828172658.dxygk7j672gho4ax@e107158-lin.cambridge.arm.com> <58f5d2e8-493b-7ce1-6abd-57705e5ab437@arm.com> <20200907104845.6rust2lf2o3d5gmq@e107158-lin.cambridge.arm.com> <20200907111320.GP2674@hirez.programming.kicks-ass.net> <20200907145155.fsmeygi4fiypikzk@e107158-lin.cambridge.arm.com> <20200908151722.b7ai2bpgvixlimz3@e107158-lin.cambridge.arm.com> From: Dietmar Eggemann Message-ID: Date: Tue, 8 Sep 2020 18:17:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200908151722.b7ai2bpgvixlimz3@e107158-lin.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/09/2020 17:17, Qais Yousef wrote: > On 09/08/20 13:17, Dietmar Eggemann wrote: >> On 07/09/2020 16:51, Qais Yousef wrote: >>> On 09/07/20 13:13, peterz@infradead.org wrote: >>>> On Mon, Sep 07, 2020 at 11:48:45AM +0100, Qais Yousef wrote: >>>>> IMHO the above is a hack. Out-of-tree modules should rely on public headers and >>>>> exported functions only. What you propose means that people who want to use >>>>> these tracepoints in meaningful way must have a prebuilt kernel handy. Which is >>>>> maybe true for us who work in the embedded world. But users who run normal >>>>> distro kernels (desktop/servers) will fail to build against >>>> >>>> But this isn't really aimed at regular users. We're aiming this at >>>> developers (IIUC) so I dont really see this as a problem. >> >> This is what I thought as well. All these helpers can be coded directly >> in these tracepoint-2-traceevent (tp-2-te) converters. As long as they >> are build from within kernel/sched/ there is no issue with the export >> via kernel/sched/sched.h. Otherwise this little trick would be necessary. >> But since it is a tool for developers I guess we can assume that they >> can build it from within kernel/sched/. > > I think this will reduce the usefulness of these tracepoints. But if you really > want to remove them, I am certainly not strongly attached to them and they were > meant to be removable anyway. So fine by me :-) I would like to see them go. Less stuff to maintain. And as we see with the new cpu_capacity tp there are always more helper functions coming. IMHO, the ability to build those modules via public headers is less important since they are meant for developers.