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 6645F7D043 for ; Thu, 31 May 2018 16:09:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755507AbeEaQJR (ORCPT ); Thu, 31 May 2018 12:09:17 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:52824 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755456AbeEaQJQ (ORCPT ); Thu, 31 May 2018 12:09:16 -0400 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=0QOwRxESCMF6JuqJd8MdrY+MklytCyX6FiA0QLhgpuU=; b=qhi9ZUpfAFvnNM7TWasYDXvTY 939AR6tEQvAfNSdLlLuQUzj9RhzihpYly3e1Jm6Z7fI6li14v+FWXD+TMTGbxrF6JDD2IjD8tvQsd M+0pEJKwxxMeWejNgrc+86VPKbL1u01mPLnpv+vUN2aZ5wtOd7Ge1VMChpxaJah5ZEFf4Pm7Vjy1Z GN8biTHLclCFdfgmjfbZax1Mr1unjSJRN02EfhexWPkh4hmOD75XzSXhlHA8Hg5jZXYJrvfFB65tk LjiuVOFmKmGfLuSRLb4w65g6mdv3g9DNz90LYWptZUigCl3BWDFG/j7gNEbc786uz6RFJcmaJN3Pe qLejiDMSA==; 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 1fOQ8J-0000xQ-2c; Thu, 31 May 2018 16:08:59 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4790E20298BA7; Thu, 31 May 2018 18:08:57 +0200 (CEST) Date: Thu, 31 May 2018 18:08:57 +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 , Patrick Bellasi , Thomas Gleixner Subject: Re: [PATCH v9 3/7] cpuset: Add cpuset.sched.load_balance flag to v2 Message-ID: <20180531160857.GM12180@hirez.programming.kicks-ass.net> References: <1527601294-3444-1-git-send-email-longman@redhat.com> <1527601294-3444-4-git-send-email-longman@redhat.com> <20180531122638.GJ12180@hirez.programming.kicks-ass.net> <42cc1f44-2355-1c0c-b575-49c863303c42@redhat.com> <20180531152050.GK12180@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, May 31, 2018 at 11:36:39AM -0400, Waiman Long wrote: > > I'm on the fence myself; the only thing I'm fairly sure of is that tying > > this particular behaviour to the load-balance knob seems off. > > The main reason for doing it this way is that I don't want to have > load-balanced partition with no cpu in it. How about we just don't allow > consume-all at all. Each partition must have at least 1 cpu. I suspect that might be sufficient. It certainly is for the use-cases I'm aware of. You always want a system/control set which runs the regular busy work of running a system. Then you have one (or more) partitions to run your 'important' work. > > I also think we should not mix the 'consume all' thing with the > > 'fully-partitioned' thing, as they are otherwise unrelated. > > The "consume all" and "fully-partitioned" look the same to me. Are you > talking about allocating all the CPUs in a partition to sub-partitions > so that there is no CPU left in the parent partition? Not sure what you're asking. "consume all" is allowing sub-partitions to allocate all CPUs of the parent, such that there are none left. "fully-partitioned" is N cpus but no load-balancing, also equivalent to N 1 CPU parititions. They are distinct things. Disabling load-balancing should not affect how many CPUs can be allocated to sub-partitions, the moment you hit 1 CPU the load balancing is effectively off already. Going down to 0 CPUs isn't a problem for the load-balancer, it wasn't doing anything anyway. So the question is if someone really needs the one partition without balancing over N separate paritions. -- 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