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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 8EC54C282C0 for ; Wed, 23 Jan 2019 19:10:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5FDBF2184B for ; Wed, 23 Jan 2019 19:10:16 +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="Wg4QR/xK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726361AbfAWTKO (ORCPT ); Wed, 23 Jan 2019 14:10:14 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:40660 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726101AbfAWTKO (ORCPT ); Wed, 23 Jan 2019 14:10:14 -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=WR9PUrRzUHma+Z7YOmuyL5asuyyyFMfZUNkzeEZT7Xw=; b=Wg4QR/xKdD2VqbA6sZua2U0vF 83H5qKeRVt47aKzlbF/c8UanYJUfK29oMo6RcF+lgzon7fd/upEUrB0WA6xdiFWcLc2CsOAUH3Tni hS2Ch0x0gHznAUuxQVXq/oN+vT5yEk1qyU2L36nHCwEzp2Mh2esTB61qsdQzWf/bMwlbbCP474HHr A/QIjzgtBWyRKzq5EX/XEJ7mMw6Hvf0oOumGjJyAI8rs5Br+WBPrgChkGtZZdhKCmvkBxN4iz6yRu fqLDZj8659YgC5NINqmyuFNYewf76J8bAYZHW1vPraOq7jKJf3HDWZ9+uZGwF+JKMkT8wSlP/+AZF arYpJc2ew==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gmNub-0008GK-IG; Wed, 23 Jan 2019 19:10:09 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 02C90236EC0DA; Wed, 23 Jan 2019 20:10:07 +0100 (CET) Date: Wed, 23 Jan 2019 20:10:07 +0100 From: Peter Zijlstra To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org, Ingo Molnar , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v6 07/16] sched/core: uclamp: Add system default clamps Message-ID: <20190123191007.GG17749@hirez.programming.kicks-ass.net> References: <20190115101513.2822-1-patrick.bellasi@arm.com> <20190115101513.2822-8-patrick.bellasi@arm.com> <20190122135644.GP27931@hirez.programming.kicks-ass.net> <20190122144329.ziimv6fejwvky7yb@e110439-lin> <20190122151317.GH13777@hirez.programming.kicks-ass.net> <20190122154129.mxnpgaoxnccbjbch@e110439-lin> <20190123092210.GU27931@hirez.programming.kicks-ass.net> <20190123141924.x36iqxh42lkssrxl@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190123141924.x36iqxh42lkssrxl@e110439-lin> 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 Wed, Jan 23, 2019 at 02:19:24PM +0000, Patrick Bellasi wrote: > On 23-Jan 10:22, Peter Zijlstra wrote: > > On Tue, Jan 22, 2019 at 03:41:29PM +0000, Patrick Bellasi wrote: > > > On 22-Jan 16:13, Peter Zijlstra wrote: > > > > On Tue, Jan 22, 2019 at 02:43:29PM +0000, Patrick Bellasi wrote: > > > > > > > Do you think that could be acceptable? > > > > > > > > Think so, it's a sysctl poke, 'nobody' ever does that. > > > > > > Cool, so... I'll keep lazy update for system default. > > > > Ah, I think I misunderstood. I meant to say that since nobody ever pokes > > at sysctl's it doesn't matter if its a little more expensive and iterate > > everything. > > Here I was more worried about the code complexity/overhead... for > something actually not very used/useful. > > > Also; if you always keep everything up-to-date, you can avoid doing that > > duplicate accounting. > > To update everything we will have to walk all the CPUs and update all > the RUNNABLE tasks currently enqueued, which are either RT or CFS. > > That's way more expensive both in code and time then what we do for > cgroups, where at least we have a limited scope since the cgroup > already provides a (usually limited) list of tasks to consider. > > Do you think it's really worth to have ? Dunno; the whole double bucket thing seems a bit weird to me; but maybe it will all look better without the mapping stuff.