Re: [Xen-users] VCPUs vs Cores

[Kun Cheng <chengkunck@xxxxxxxxx>]

Hi Manuel,

You can pin those vcpus to cpu cores in either your vm configurations or via xl command line.

See https://wiki.xenproject.org/wiki/Tuning_Xen_for_Performance or simply search xen vcpu pinning in Google.

For example, in your guest vm config file, use cpus="2-8" means pin vcpus to core 2-8, in your case you might want to pin them to 0-11 or 2-13.

Best,

Kenneth

On Wed, Oct 25, 2017 at 7:53 AM admin <admin@xxxxxxx> wrote:

Hi,

on a server with two QuadCore Xeon CPUs I observe the following:

2 CPUs x 4 Cores x 2 threads result in 16 "cores" / VCPUs.
I now assign 12 of these to a windows server VM. In the
device manager I see 12 CPUs. Is every core (vcpu) passed
as a single CPU to my VM?

If so, is there any config file option to change this?
I am asking because one of the limitations of the free
SQL Server Express is that it is utilizing max 1 CPU / 4 cores.

If each thread / vcpu is passed as a independent CPU I
am lacking possible performance. Any hint on that?

Talking about Xen 4.4 here.

Regards,
Manuel

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