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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 9CFDFC433E0 for ; Mon, 25 Jan 2021 10:22:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 379FF208C7 for ; Mon, 25 Jan 2021 10:22:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727349AbhAYKW3 (ORCPT ); Mon, 25 Jan 2021 05:22:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727398AbhAYKQJ (ORCPT ); Mon, 25 Jan 2021 05:16:09 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E62AC06178A; Mon, 25 Jan 2021 02:04:53 -0800 (PST) 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=ypMbUlgrFbzcYuyucmNzuPumJ/xgx4bvW34r5XmbX2k=; b=q+Ey7/6eqsYlxEb26Jlt9VFQu+ lkJNNN+ouMyaQPwzLeanUfS9aIhBlgUpehQjGLYi+paXzMifRwePCvK3tpdrmNf5kQsYyPtY8+QX5 uBRAEDSP31JRdBJQ7mv1nLE4jBZHBBsrmL5WFOzOitm3TlkHZU/sMJcu+S3uPSd+uJH4g4lbLipkH wWN5fwjMRALwccVtTwgmEdaVggHULpi0GubaHrezgIgZKeE/GK182Qa+xTFCEnRKEi5ZfJr8ePpbV XkWct4vsBx6iUjhHb5Isw4drz3XUruAMrjUaAjkM0aH+yyjhOPgnRM2F23QFu8zzsyh4bhZjgxCuL LVTypm2g==; 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 1l3yjD-000500-Lp; Mon, 25 Jan 2021 10:04:11 +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 63A2F300DB4; Mon, 25 Jan 2021 11:04:08 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4FBF928B66D18; Mon, 25 Jan 2021 11:04:08 +0100 (CET) Date: Mon, 25 Jan 2021 11:04:08 +0100 From: Peter Zijlstra To: Giovanni Gherdovich Cc: Borislav Petkov , Ingo Molnar , "Rafael J . Wysocki" , Viresh Kumar , Jon Grimm , Nathan Fontenot , Yazen Ghannam , Thomas Lendacky , Suthikulpanit Suravee , Mel Gorman , Pu Wen , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Michael Larabel , x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH v2 1/1] x86,sched: On AMD EPYC set freq_max = max_boost in schedutil invariant formula Message-ID: References: <20210122204038.3238-1-ggherdovich@suse.cz> <20210122204038.3238-2-ggherdovich@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210122204038.3238-2-ggherdovich@suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 22, 2021 at 09:40:38PM +0100, Giovanni Gherdovich wrote: > This workload is constant in time, so instead of using the PELT sum we can > pretend that scale invariance is obtained with > > util_inv = util_raw * freq_curr / freq_max1 [formula-1] > > where util_raw is the PELT util from v5.10 (which is to say, not invariant), > and util_inv is the PELT util from v5.11-rc4. freq_max1 comes from > commit 976df7e5730e ("x86, sched: Use midpoint of max_boost and max_P for > frequency invariance on AMD EPYC") and is (P0+max_boost)/2 = (2.25+3.4)/2 = > 2.825 GHz. Then we have the schedutil formula > > freq_next = 1.25 * freq_max2 * util_inv [formula-2] > > Here v5.11-rc4 uses freq_max2 = P0 = 2.25 GHz (and this patch changes it to > 3.4 GHz). > > Since all cores are busy, there is no boost available. Let's be generous and say > the tasks initially get P0, i.e. freq_curr = 2.25 GHz. Combining the formulas > above and taking util_raw = 825/1024 = 0.8, freq_next is: > > freq_next = 1.25 * 2.25 * 0.8 * 2.25 / 2.825 = 1.79 GHz Right, so here's a 'problem' between schedutil and cpufreq, they don't use the same f_max at all times. And this is also an inconsistency between acpi_cpufreq and intel_pstate (passive). IIRC the intel_pstate cpufreq drivers uses 4C/1C/P0 resp, while ACPI seems to stick to P0 f_max. Rafael; should ACPI change that behaviour rather than adding yet another magic variable?