From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [RFC 5/8] Make writeout during reclaim cpuset aware Date: Wed, 17 Jan 2007 16:59:15 +1100 References: <20070116054743.15358.77287.sendpatchset@schroedinger.engr.sgi.com> <200701171528.16854.ak@suse.de> <20070116203622.7f1b4e87.pj@sgi.com> In-Reply-To: <20070116203622.7f1b4e87.pj@sgi.com> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200701171659.16290.ak@suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Paul Jackson Cc: clameter@sgi.com, akpm@osdl.org, menage@google.com, linux-kernel@vger.kernel.org, nickpiggin@yahoo.com.au, linux-mm@kvack.org, dgc@sgi.com List-ID: On Wednesday 17 January 2007 15:36, Paul Jackson wrote: > > With a per node dirty limit ... > > What would this mean? > > Lets say we have a simple machine with 4 nodes, cpusets disabled. There can be always NUMA policy without cpusets for once. > Lets say all tasks are allowed to use all nodes, no set_mempolicy > either. Ok. > If a task happens to fill up 80% of one node with dirty pages, but > we have no dirty pages yet on other nodes, and we have a dirty ratio > of 40%, then do we throttle that task's writes? Yes we should actually. Every node should be able to supply memory (unless extreme circumstances like mlock) and that much dirty memory on a node will make that hard. > I am surprised you are asking for this, Andi. I would have thought > that on no-cpuset systems, the system wide throttling served your > needs fine. No actually people are fairly unhappy when one node is filled with file data and then they don't get local memory from it anymore. I get regular complaints about that for Opteron. Dirty limit wouldn't be a full solution, but a good step. > If not, then I can only guess that is because NUMA > mempolicy constraints on allowed nodes are causing the same dirty page > problems as cpuset constrained systems -- is that your concern? That is another concern. I haven't checked recently, but it used to be fairly simple to put a system to its knees by oversubscribing a single node with a strict memory policy. Fixing that would be good. -Andi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org