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,DKIMWL_WL_HIGH, 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 644FBC388F7 for ; Thu, 22 Oct 2020 20:39:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 15EBA24640 for ; Thu, 22 Oct 2020 20:39:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ior1q17y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2901257AbgJVUjc (ORCPT ); Thu, 22 Oct 2020 16:39:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:27074 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S371724AbgJVUjb (ORCPT ); Thu, 22 Oct 2020 16:39:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603399170; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6Es6PtacViKqb4jQqg5gw1aMx5VJx45xwSoGJuNjLWg=; b=Ior1q17y+hc6lmWPcJ1XGsLp6cjaaxLLTF8vFy7pgXjdtk2NcFKvsOvS8sTnkIolhU6IzB cVFjaL6ZwVTBABOob3nTiU50XwTDgG0sJYl+Iufmcc4Ikxsap6HyQN7frjmQEoL4/UAGSi iEOjELQ12OV3RWrtvqs2dFFUVeCpWuk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-569-ryZ9fepCPgylb0QODfouhA-1; Thu, 22 Oct 2020 16:39:27 -0400 X-MC-Unique: ryZ9fepCPgylb0QODfouhA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3A6FA1006CA9; Thu, 22 Oct 2020 20:39:24 +0000 (UTC) Received: from lorien.usersys.redhat.com (ovpn-113-70.phx2.redhat.com [10.3.113.70]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 24C9660BFA; Thu, 22 Oct 2020 20:39:15 +0000 (UTC) Date: Thu, 22 Oct 2020 16:39:13 -0400 From: Phil Auld To: Mel Gorman Cc: "Rafael J. Wysocki" , Colin Ian King , Peter Zijlstra , "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 Mailing List , Valentin Schneider , Gilles Muller , Srinivas Pandruvada , Linux PM , Len Brown Subject: Re: default cpufreq gov, was: [PATCH] sched/fair: check for idle core Message-ID: <20201022203913.GJ92942@lorien.usersys.redhat.com> References: <34115486.YmRjPRKJaA@kreacher> <20201022120213.GG2611@hirez.programming.kicks-ass.net> <1790766.jaFeG3T87Z@kreacher> <20201022122949.GW2628@hirez.programming.kicks-ass.net> <20201022145250.GK32041@suse.de> <6606e5f4-3f66-5844-da02-5b11e1464be6@canonical.com> <20201022151200.GC92942@lorien.usersys.redhat.com> <20201022163509.GM32041@suse.de> <20201022203255.GN32041@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201022203255.GN32041@suse.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Thu, Oct 22, 2020 at 09:32:55PM +0100 Mel Gorman wrote: > On Thu, Oct 22, 2020 at 07:59:43PM +0200, Rafael J. Wysocki wrote: > > > > Agreed. I'd like the option to switch back if we make the default change. > > > > It's on the table and I'd like to be able to go that way. > > > > > > > > > > Yep. It sounds chicken, but it's a useful safety net and a reasonable > > > way to deprecate a feature. It's also useful for bug creation -- User X > > > running whatever found that schedutil is worse than the old governor and > > > had to temporarily switch back. Repeat until complaining stops and then > > > tear out the old stuff. > > > > > > When/if there is a patch setting schedutil as the default, cc suitable > > > distro people (Giovanni and myself for openSUSE). > > > > So for the record, Giovanni was on the CC list of the "cpufreq: > > intel_pstate: Use passive mode by default without HWP" patch that this > > discussion resulted from (and which kind of belongs to the above > > category). > > > > Oh I know, I did not mean to suggest that you did not. He made people > aware that this was going to be coming down the line and has been looking > into the "what if schedutil was the default" question. AFAIK, it's still > a work-in-progress and I don't know all the specifics but he knows more > than I do on the topic. I only know enough that if we flipped the switch > tomorrow that we could be plagued with google searches suggesting it be > turned off again just like there is still broken advice out there about > disabling intel_pstate for usually the wrong reasons. > > The passive patch was a clear flag that the intent is that schedutil will > be the default at some unknown point in the future. That point is now a > bit closer and this thread could have encouraged a premature change of > the default resulting in unfair finger pointing at one company's test > team. If at least two distos check it out and it still goes wrong, at > least there will be shared blame :/ > > > > Other distros assuming they're watching can nominate their own victim. > > > > But no other victims had been nominated at that time. > > We have one, possibly two if Phil agrees. That's better than zero or > unfairly placing the full responsibility on the Intel guys that have been > testing it out. > Yes. I agree and we (RHEL) are planning to test this soon. I'll try to get to it. You can certainly CC me, please, athough I also try to watch for this sort of thing on list. Cheers, Phil > -- > Mel Gorman > SUSE Labs > --