From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f175.google.com (mail-ob0-f175.google.com [209.85.214.175]) by kanga.kvack.org (Postfix) with ESMTP id 165F66B0031 for ; Tue, 18 Feb 2014 17:23:21 -0500 (EST) Received: by mail-ob0-f175.google.com with SMTP id wn1so19188872obc.34 for ; Tue, 18 Feb 2014 14:23:20 -0800 (PST) Received: from e35.co.us.ibm.com (e35.co.us.ibm.com. [32.97.110.153]) by mx.google.com with ESMTPS id sp3si12840612obb.108.2014.02.18.14.23.20 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 18 Feb 2014 14:23:20 -0800 (PST) Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 18 Feb 2014 15:23:19 -0700 Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 2FEF919D8045 for ; Tue, 18 Feb 2014 15:23:16 -0700 (MST) Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by b03cxnp08027.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s1IMMmM351511530 for ; Tue, 18 Feb 2014 23:22:53 +0100 Received: from d03av02.boulder.ibm.com (localhost [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s1IMMu2j012606 for ; Tue, 18 Feb 2014 15:22:56 -0700 Date: Tue, 18 Feb 2014 14:22:42 -0800 From: Nishanth Aravamudan Subject: Re: [RFC PATCH 2/3] topology: support node_numa_mem() for determining the fallback node Message-ID: <20140218222242.GA10844@linux.vnet.ibm.com> References: <20140210191321.GD1558@linux.vnet.ibm.com> <20140211074159.GB27870@lge.com> <20140213065137.GA10860@linux.vnet.ibm.com> <20140217070051.GE3468@lge.com> <20140218172832.GD31998@linux.vnet.ibm.com> <20140218210923.GA28170@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Joonsoo Kim , David Rientjes , Han Pingtian , Pekka Enberg , Linux Memory Management List , Paul Mackerras , Anton Blanchard , Matt Mackall , linuxppc-dev@lists.ozlabs.org, Wanpeng Li On 18.02.2014 [15:49:22 -0600], Christoph Lameter wrote: > On Tue, 18 Feb 2014, Nishanth Aravamudan wrote: > > > We use the topology provided by the hypervisor, it does actually reflect > > where CPUs and memory are, and their corresponding performance/NUMA > > characteristics. > > And so there are actually nodes without memory that have processors? Virtually (topologically as indicated to Linux), yes. Physically, I don't think they are, but they might be exhausted, which is we get sort of odd-appearing NUMA configurations. > Can the hypervisor or the linux arch code be convinced to ignore nodes > without memory or assign a sane default node to processors? I think this happens quite often, so I don't know that we want to ignore the performance impact of the underlying NUMA configuration. I guess we could special-case memoryless/cpuless configurations somewhat, but I don't think there's any reason to do that if we can make memoryless-node support work in-kernel? > > > Ok then also move the memory of the local node somewhere? > > > > This happens below the OS, we don't control the hypervisor's decisions. > > I'm not sure if that's what you are suggesting. > > You could also do this from the powerpc arch code by sanitizing the > processor / node information that is then used by Linux. I see what you're saying now, thanks! -Nish -- 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