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

[John Naggets <hostingnuggets@xxxxxxxxx>]

Thanks Hans for your interesting comments.

I forgot to mention that I also have added in my /etc/rc.local the
following to be on the safe side:

/usr/sbin/xl sched-credit -d 0 -w 512

So if I understand here correctly this is a fine config for mixed HVM
and PV domUs ensuring enough resources to the dom0?

I am using a Intel Xeon Silver 4110 CPU @ 2.10GHz which has 8 cores
and 16 threads.

On Mon, Feb 12, 2018 at 11:00 PM, Hans van Kranenburg <hans@xxxxxxxxxxx> wrote:
> 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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