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Re: [Xen-users] XenServer adding additional CPUs to the control domain?

To: David Erickson <halcyon1981@xxxxxxxxx>
Subject: Re: [Xen-users] XenServer adding additional CPUs to the control domain?
From: "Fajar A. Nugraha" <list@xxxxxxxxx>
Date: Mon, 3 Jan 2011 14:06:13 +0700
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On Mon, Jan 3, 2011 at 12:57 PM, David Erickson <halcyon1981@xxxxxxxxx> wrote:
> Hi all,
> I have a large pool and when it syncs up the load on the control
> domain of my pool is pretty high (I've seen up to 77..), I'd like to
> add more than 1 cpu to it, is that possible?  I tried the suggestion
> "echo 1 > /sys/devices/system/cpu/cpu1/online" followed by a reboot
> but this didn't take, upon reboot all the cpus are back off.

On "good" xen+dom0 kernel versions (like the one bundled in RHEL5), a
simple "xm vcpu-set 0 4" (to assign 4 cpus to dom0) will do the trick
just fine.

On some "bad" xen+dom0 combinations, you might need to run "echo 1 >
/sys/devices/system/cpu/cpu1/online" (no reboot needed) in addition to
xm vcpu-set. On REALLY bad combination, even the above command won't

So my suggestion is try "xm vcpu-set" route, and if doesn't work, you
should seriously consider changing xen/dom0 kernel combination.


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