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=-3.9 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 7DAAFC388F7 for ; Thu, 22 Oct 2020 15:25:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2030924630 for ; Thu, 22 Oct 2020 15:25:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="SR5PUoAV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2901434AbgJVPZs (ORCPT ); Thu, 22 Oct 2020 11:25:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42094 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2901438AbgJVPZm (ORCPT ); Thu, 22 Oct 2020 11:25:42 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E34FCC0613CE; Thu, 22 Oct 2020 08:25:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=uNiU3efnTwPeAKOY4UJUGM46GfdX/X2ngekQQHB4va8=; b=SR5PUoAVNy8wU0ea/eyb0/kUYU 53hX/8NiDEWA0ZcRxmxtqRpgpbNnip2BBnOrXY8+9D7Q8oIpeDgt4npEjXf+5wVqGyqFySUkSERco 6x7Vc5LmIzk5Us32wJWXaYLn+n7D79f9u5o/K9QPn0IB9dBAUNeawLiJoH7nCGoS7IYkCN46k3q5e Xf09A4bKmOQxGUw89OpsbvyTa1O3FSlcXxEvdaJZrek5lRBKG+ywveYoL6iQ3yu9uwjAEVRMzTk4c tSdHzC1BRqBjPk2hEZZAlbtX2TubM8HeFx7vhQR43uVLFRney+3dZXlI9m18+FQQNPxhiU1EHyJQi 4YvhkQvw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVcSq-0006or-2N; Thu, 22 Oct 2020 15:25:16 +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 86DE03010D2; Thu, 22 Oct 2020 17:25:14 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6DA02203D0835; Thu, 22 Oct 2020 17:25:14 +0200 (CEST) Date: Thu, 22 Oct 2020 17:25:14 +0200 From: Peter Zijlstra To: Mel Gorman Cc: "Rafael J. Wysocki" , Giovanni Gherdovich , Viresh Kumar , Julia Lawall , Ingo Molnar , kernel-janitors@vger.kernel.org, Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , linux-kernel@vger.kernel.org, Valentin Schneider , Gilles Muller , srinivas.pandruvada@linux.intel.com, Linux PM , Len Brown Subject: Re: default cpufreq gov, was: [PATCH] sched/fair: check for idle core Message-ID: <20201022152514.GJ2611@hirez.programming.kicks-ass.net> References: <1603211879-1064-1-git-send-email-Julia.Lawall@inria.fr> <34115486.YmRjPRKJaA@kreacher> <20201022120213.GG2611@hirez.programming.kicks-ass.net> <1790766.jaFeG3T87Z@kreacher> <20201022122949.GW2628@hirez.programming.kicks-ass.net> <20201022145250.GK32041@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201022145250.GK32041@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Thu, Oct 22, 2020 at 03:52:50PM +0100, Mel Gorman wrote: > There are some questions > currently on whether schedutil is good enough when HWP is not available. Srinivas and Rafael will know better, but Intel does run a lot of tests and IIRC it was found that schedutil was on-par for !HWP. That was the basis for commit: 33aa46f252c7 ("cpufreq: intel_pstate: Use passive mode by default without HWP") But now it turns out that commit results in running intel_pstate-passive on ondemand, which is quite horrible. > There was some evidence (I don't have the data, Giovanni was looking into > it) that HWP was a requirement to make schedutil work well. That seems to be the question; Rafael just said the opposite. > For distros, switching to schedutil by default would be nice because > frequency selection state would follow the task instead of being per-cpu > and we could stop worrying about different HWP implementations but it's s/HWP/cpufreq-governors/ ? But yes. > not at the point where the switch is advisable. I would expect hard data > before switching the default and still would strongly advise having a > period of time where we can fall back when someone inevitably finds a > new corner case or exception. Which is why I advocated to make it 'difficult' to use the old ones and only later remove them. > For reference, SLUB had the same problem for years. It was switched > on by default in the kernel config but it was a long time before > SLUB was generally equivalent to SLAB in terms of performance. I remember :-)