From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Andre Przywara" Subject: Re: [PATCH 2/4] [HVM] introduce CPU affinity for allocate_physmap call Date: Wed, 15 Aug 2007 12:12:56 +0200 Message-ID: <46C2D1A8.1030001@amd.com> References: <200708131459.31305.Christoph.Egger@amd.com> <20070813204947.GC1228@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20070813204947.GC1228@us.ibm.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ryan Harper Cc: Christoph Egger , xen-devel@lists.xensource.com, Keir Fraser List-Id: xen-devel@lists.xenproject.org Ryan Harper wrote: > One concern has been the static nature of the ACPI SRAT data versus the > dynamic ability of the vcpu to cpu mapping. If the scheduler is > migrating the guest vcpu to various cpus, then the SRAT information is > likely to be incorrect. I think this is a problem even for the native OSes when you think of=20 CPU- and/or memory-hotplugging. Although Linux can do CPU hotplugging,=20 AFAIK NUMA isn't currently considered in this process. I think the most=20 feasible approach would be to rebuild all affected structures when the=20 hotplug event occurs. This will probably considered quite rare and thus=20 could be potentially more costly, so I this is not something you want to=20 do every time Xen decides to reschedule a VCPU. So IMHO pinning VCPUs to=20 a certain node (actually all cores within this node) is OK for now. >=20 > That said, if one creates a vnode, and it sufficiently restricts the > vcpu affinity, then accurate SRAT information can be exported for the > guest to utilize. My patch does this automatically. CPU affinity information from the=20 config file is ignored and each VCPUs affinity is set to match the NUMA=20 topology. Regards, Andre. --=20 Andre Przywara AMD-Operating System Research Center (OSRC), Dresden, Germany Tel: +49 351 277-84917 ----to satisfy European Law for business letters: AMD Saxony Limited Liability Company & Co. KG Sitz (Gesch=E4ftsanschrift): Wilschdorfer Landstr. 101, 01109 Dresden,=20 Deutschland Registergericht Dresden: HRA 4896 vertretungsberechtigter Komplement=E4r: AMD Saxony LLC (Sitz Wilmington,=20 Delaware, USA) Gesch=E4ftsf=FChrer der AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy