kvm presenting wrong CPU Topology for cache

Satish Patel
Sun, 01 Mar 2020 17:42:10 -0000

Any thought here ?

Sent from my iPhone

> On Feb 28, 2020, at 3:55 PM, Satish Patel <satish.txt at gmail.com>
wrote:
>
> ?Folks,
>
> I am having major performance issue with my Erlang application running
> on openstack KVM hypervisor and after so many test i found something
> wrong with my KVM guest CPU Topology
>
> This is KVM host - http://paste.openstack.org/show/790120/
> This is KVM guest - http://paste.openstack.org/show/790121/
>
> If you carefully observe output of both host and guest you can see
> guest machine threads has own cache that is very strange
>
> L2 L#0 (4096KB) + Core L#0
>      L1d L#0 (32KB) + L1i L#0 (32KB) + PU L#0 (P#0)
>      L1d L#1 (32KB) + L1i L#1 (32KB) + PU L#1 (P#1)
>
> I believe because of that my erlang doesn't understand topology and
> going crazy..
>
> I have Ali Cloud and AWS and when i compare with them they are showing
> correct CPU Topology the way physical machine showing, something is
> wrong with my KVM look like.
>
> I am running qemu-kvm-2.12 on centos 7.6 and i have tune my KVM at my
> best level, like CPU vining, NUMA and cpu host-passthrough.
>
> Thanks in advance for your help.