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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 43FE0C43603 for ; Fri, 20 Dec 2019 12:20:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 12A3C24679 for ; Fri, 20 Dec 2019 12:20:07 +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="kGleREul" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727360AbfLTMUG (ORCPT ); Fri, 20 Dec 2019 07:20:06 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48508 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727209AbfLTMUG (ORCPT ); Fri, 20 Dec 2019 07:20:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=R5Zw3DDJm4ULPliPYUAssjzZ7w7pMoy4+U0VF7anJkg=; b=kGleREul1+TOIzHsXgqHZ4Cbq 4MeHJK5OCxVpyeUhcrn4CWbXjCzzGTXNYQmilD7zoJVZs2mlZ+++cSHPzBI73i9aDHhRjONctFEsT /VW6qnZo1P8/l5b+cU+nB+zxwjnAWy6svrA3N/QHZQotSX3ahFyfe3RQbJhB4uotDaqG7FWxgQdwK BZIN/8nCFvnv1iqS5ZcLLw66PHJNQlh53yIqPDCv800XrVXKZH3ehTze5Xt2dFWEJTSUudSYHPHRH LBV2u4nm8Qco5AwB9aVQrWj3p+g/ZFQ/9fj4LSQJNheTcNBqGe1yQVMU4XdjpMeHSfe1oAhe8OwfF I+egC4T4g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iiHG1-0005GX-Fr; Fri, 20 Dec 2019 12:19:51 +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 82D67300DB7; Fri, 20 Dec 2019 13:18:23 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6D4702B270F5D; Fri, 20 Dec 2019 13:19:47 +0100 (CET) Date: Fri, 20 Dec 2019 13:19:47 +0100 From: Peter Zijlstra To: Rasmus Villemoes Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Kirill Tkhai , Kirill Tkhai , "mingo@redhat.com" , "juri.lelli@redhat.com" , "vincent.guittot@linaro.org" , "dietmar.eggemann@arm.com" , "bsegall@google.com" , "mgorman@suse.de" , Ingo Molnar , Andrew Morton Subject: Re: [RFC][PATCH 1/4] sched: Force the address order of each sched class descriptor Message-ID: <20191220121947.GH2844@hirez.programming.kicks-ass.net> References: <20191219214451.340746474@goodmis.org> <20191219214558.510271353@goodmis.org> <0a957e8d-7af8-613c-11ae-f51b9b241eb7@rasmusvillemoes.dk> <20191220100033.GE2844@hirez.programming.kicks-ass.net> <1ac359e8-fa7f-7ded-e2f2-9f7d0b23a4e1@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1ac359e8-fa7f-7ded-e2f2-9f7d0b23a4e1@rasmusvillemoes.dk> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 20, 2019 at 11:12:37AM +0100, Rasmus Villemoes wrote: > On 20/12/2019 11.00, Peter Zijlstra wrote: > >>> +/* > >>> + * The order of the sched class addresses are important, as they are > >>> + * used to determine the order of the priority of each sched class in > >>> + * relation to each other. > >>> + */ > >>> +#define SCHED_DATA \ > >>> + *(__idle_sched_class) \ > >>> + *(__fair_sched_class) \ > >>> + *(__rt_sched_class) \ > >>> + *(__dl_sched_class) \ > >>> + STOP_SCHED_CLASS > > > > I'm confused, why does that STOP_SCHED_CLASS need magic here at all? > > Doesn't the linker deal with empty sections already by making them 0 > > sized? > > Yes, but dropping the STOP_SCHED_CLASS define doesn't prevent one from > needing some ifdeffery to define highest_sched_class if they are laid > out in (higher sched class <-> higher address) order. Would not something like: __begin_sched_classes = .; *(__idle_sched_class) *(__fair_sched_class) *(__rt_sched_class) *(__dl_sched_class) *(__stop_sched_class) __end_sched_classes = .; combined with something like: extern struct sched_class *__begin_sched_classes; extern struct sched_class *__end_sched_classes; #define sched_class_highest (__end_sched_classes - 1) #define sched_class_lowest (__begin_sched_classes - 1) #define for_class_range(class, _from, _to) \ for (class = (_from); class != (_to), class--) #define for_each_class(class) \ for_class_range(class, sched_class_highest, sched_class_lowest) just work? When no __stop_sched_class is present, that section is 0 sized, and __end_sched_classes points to one past __dl_sched_class, no?