Re: [Xen-users] Xen dom0 vCPUs pinning for PV/HVM domUs

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

On 02/12/2018 10:42 PM, John Naggets wrote:
> Hello,
> 
> I am running Xen 4.9 on Unbutu 17.10 with a mix of PV and HVM domUs.
> Now on the dom0 side I have pinned 2 vCPUs and reserved 4 GB as I am
> used to do that in a pure PV domU environment (no HVM).
> 
> Now I was wondering if this is still valid when running a mix of PV
> and HVM domUs? or is this recommendations of pinning and reserving
> memory for the dom0 only valid when running PV domUs?
> 
> These are the Xen settings I use in my /etc/default/grub file:
> 
> GRUB_CMDLINE_XEN="dom0_mem=4G,max:4G dom0_max_vcpus=2 dom0_vcpus_pin"

The dom0_mem=4G,max:4G is always a good idea to prevent the golden age
of ballooning from happening in your dom0.

I have dom0_max_vcpus=4 myself (servers have 16 or 20 cpu cores) and no
dom0_vcpus_pin, but I use...

  xl sched-credit -d 0 -w 32767

...to give the dom0 a ridiculous high priority if it requests cpu time,
to make sure it gets scheduled first.

https://wiki.xenproject.org/wiki/Tuning_Xen_for_Performance#Dom0_vCPUs

Hans

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