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 99F74C433E0 for ; Tue, 26 Jan 2021 03:12:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7168722D58 for ; Tue, 26 Jan 2021 03:12:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727394AbhAYKPI (ORCPT ); Mon, 25 Jan 2021 05:15:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726614AbhAYKIH (ORCPT ); Mon, 25 Jan 2021 05:08:07 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE00AC06178B; Mon, 25 Jan 2021 02:06:30 -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=GtW+rqjBxkqPAgL+lYKMDvLoZJFjuWlfCcBAqCEjP5s=; b=WJyw0nG2FuUQR4LFIN4hKSNWnv CtcoSv8B8UtYxJHi5AKG1FYYZNVorPAQ6nXBtosCtNuF62XaAMoRda/QWD7slH2EZA+wsT++O4H4Q dYbn8ohRzsYbDseZb0piXlX6IdhjnxsxM1a0sziELEA14GdW5zIH91RwEQyV/ATy2Tnsq8XwPsLYT yI9U083MD98OAwroK9WLJoKNcwaTDr15rP/83+dcj9Sc4uPEQOaZR3xYlEz3eqlQLt7ZI4AIihVNK AJfgltRW7BifG+3DPWv9ppPlklIHMthgGqWWr3LbHrhWU8OrdMpDRvY+PcccMIqC3nC86VtJLEU3x FzfvsCjg==; 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 1l3yl8-0005Gq-L3; Mon, 25 Jan 2021 10:06:10 +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 DB4003010C8; Mon, 25 Jan 2021 11:06:08 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BA1AD28B66D18; Mon, 25 Jan 2021 11:06:08 +0100 (CET) Date: Mon, 25 Jan 2021 11:06:08 +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: > 1. PROBLEM DESCRIPTION (over-utilization and schedutil) > > The problem happens on CPU-bound workloads spanning a large number of cores. > In this case schedutil won't select the maximum P-State. Actually, it's > likely that it will select the minimum one. > > A CPU-bound workload puts the machine in a state generally called > "over-utilization": an increase in CPU speed doesn't result in an increase of > capacity. The fraction of time tasks spend on CPU becomes constant regardless > of clock frequency (the tasks eat whatever we throw at them), and the PELT > invariant util goes up and down with the frequency (i.e. it's not invariant > anymore). > v5.10 v5.11-rc4 > ~~~~~~~~~~~~~~~~~~~~~~~~ > CPU activity (mpstat) 80-90% 80-90% > schedutil requests (tracepoint) always P0 mostly P2 > CPU frequency (HW feedback) ~2.2 GHz ~1.5 GHz > PELT root rq util (tracepoint) ~825 ~450 > > mpstat shows that the workload is CPU-bound and usage doesn't change with So I'm having trouble with calling a 80%-90% workload CPU bound, because clearly there's a ton of idle time.