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RE: [Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus asdocumented

To: "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>, <Xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus asdocumented
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Tue, 9 May 2006 16:05:36 +0100
Cc: "Subrahmanian, Raj" <raj.subrahmanian@xxxxxxxxxx>, "Krysan, Susan" <KRYSANS@xxxxxxxxxx>, "Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>, "Vessey, Bruce A" <Bruce.Vessey@xxxxxxxxxx>
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Thread-topic: [Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus asdocumented
> The comments for dom0-cpus in the xend-config.sxp file 
> indicate that setting this value to 0 in an SMP system will 
> cause dom0 to use all the available CPUs. However, it appears 
> as if setting this value to 0 does not change the number of 
> CPUs at all.
> I'm running SLES10 Beta 11 and xen-unstable changeset 9960 on 
> a Unisys ES7000 with 32 CPUs and 32GB memory. In 
> xend-config.sxp, dom0-cpus is set to 0. When xen dom0 boots, 
> it is using all 32 procs (as reported by 'grep processor 
> /proc/cpuinfo | wc -l').
> If I edit the xend-config.sxp file, change the value of 
> dom0-cpus to 1, and restart xend, dom0 correctly uses 1 CPUs. 
> If I then change dom0-cpus to 0 and restart xend, dom0 still 
> uses 1 cpu. The only way to have dom0 use 32 cpus again is to 
> either set the value of dom0-cpus to 32, or reboot xen.
> Has anyone else seen this behavior?

You can just use the normal xm commands to vary the number of CPUs.
Restarting xend is a rather brutal way of trying to achieve the same


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