From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.6 required=5.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 9DAEB7D043 for ; Mon, 28 May 2018 12:45:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1425089AbeE1Mp3 (ORCPT ); Mon, 28 May 2018 08:45:29 -0400 Received: from merlin.infradead.org ([205.233.59.134]:46990 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1425087AbeE1MpZ (ORCPT ); Mon, 28 May 2018 08:45:25 -0400 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: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=Qg2upbHUIP+Lq3k1kuOt3nwQiJ1wX2pgcfZxbw78mng=; b=OpOmeb4b1mZoeEb1Kpz1jXmVx MMdl9FzZ9nIcNbXYqKE8xskiW3Xpgf/I2FC4hBndj3xd7yFphz3NRXe2dRL0FqBW3YMu/CaTnnglv g14IR60HD+mSrZlPwsa1KFBq46AisBrhzif8ItOsbll3p0DJJg8UajEmYxUn25qF+Yh2GzGeb6BJL 0dLOUpGRygjCWHLZCD0G3Y01etTnIJaAefxmlZdKTQpgpuiwuKYQs+4s4ow+qUS6bz31gczB06xgG oYB11pulnu1SqCP2j9lVmlG0qVQg86WPbSC/bpFHh11N6vtN4ic01AGxsQUJshW8wmpmmhUqKGhDM /CTPBKRFQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fNHWQ-0000eR-5b; Mon, 28 May 2018 12:45:10 +0000 Received: by worktop (Postfix, from userid 1000) id 24A126E08A4; Mon, 28 May 2018 14:45:08 +0200 (CEST) Date: Mon, 28 May 2018 14:45:08 +0200 From: Peter Zijlstra To: Waiman Long Cc: Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli Subject: Re: [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2 Message-ID: <20180528124508.GE3452@worktop.programming.kicks-ass.net> References: <1526590545-3350-1-git-send-email-longman@redhat.com> <1526590545-3350-4-git-send-email-longman@redhat.com> <20180524154341.GJ12198@hirez.programming.kicks-ass.net> <9f547771-54e8-118e-80f7-48f99c7b0a12@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9f547771-54e8-118e-80f7-48f99c7b0a12@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, May 24, 2018 at 02:55:25PM -0400, Waiman Long wrote: > On 05/24/2018 11:43 AM, Peter Zijlstra wrote: > > I'm confused... why exactly do we have both domain and load_balance ? > > The domain is for partitioning the CPUs only. It doesn't change the load > balancing state. So the load_balance flag is still need to turn on and > off load balancing. OK, so we have to two boolean flags, giving 4 possible states. Lets just go through them one by on: A) domain:0 load_balance:0 -- we have no exclusive domain, but have load-balancing disabled across them. AFAICT this should be an invalid state. B) domain:0 load_balance:1 -- we have no exclusive domain, but have load-balancing enabled. AFAICT this is the default state and is a no-op. C) domain:1 load_balance:0 -- we have an exclusive domain, and have load-balancing disabled across it. This is, AFAICT, identical to having a bunch of sub/sibling groups each with a single CPU domain. D) domain:1 load_balance:1 -- we have an exclusive domain, and have load-balancing enabled. This is a partition. Now, I think I've overlooked the fact that load_balance==1 only really means something when the parent's load_balance==0, but I'm not sure that really changes anything. So, afaict, the above only have two useful states: B and D. Which again raises the question, why two knobs? What useful configurations does it allow? -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html