From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v9 3/7] cpuset: Add cpuset.sched.load_balance flag to v2 Date: Thu, 31 May 2018 18:08:57 +0200 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 Return-path: 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 Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 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.