CPU Topology confusion

Satish Patel satish.txt at gmail.com
Thu Mar 5 12:18:15 UTC 2020


cpu-passthrough 

Sent from my iPhone

> On Mar 4, 2020, at 9:24 PM, rui zang <rui.zang at yandex.com> wrote:
> 
> 
> Hi,
>  
> What is the value for the "cpu_mode" configuration option?
> https://docs.openstack.org/mitaka/config-reference/compute/hypervisor-kvm.html
>  
> Thanks,
> Zang, Rui
>  
>  
> 05.03.2020, 01:24, "Satish Patel" <satish.txt at gmail.com>:
> Folks,
> 
> We are running openstack with KVM and i have noticed kvm presenting
> wrong CPU Tolopoly to VM and because of that we are seeing bad
> performance to our application.
> 
> This is openstack compute:
> 
> # lstopo-no-graphics --no-io
> Machine (64GB total)
>   NUMANode L#0 (P#0 32GB) + Package L#0 + L3 L#0 (25MB)
>     L2 L#0 (256KB) + L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0
>       PU L#0 (P#0)
>       PU L#1 (P#20)
>     L2 L#1 (256KB) + L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1
>       PU L#2 (P#1)
>       PU L#3 (P#21)
> 
> This is VM running on above compute
> 
> # lstopo-no-graphics --no-io
> Machine (59GB total)
>   NUMANode L#0 (P#0 29GB) + Package L#0 + L3 L#0 (16MB)
>     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)
>     L2 L#1 (4096KB) + Core L#1
>       L1d L#2 (32KB) + L1i L#2 (32KB) + PU L#2 (P#2)
>       L1d L#3 (32KB) + L1i L#3 (32KB) + PU L#3 (P#3)
> 
> if you noticed P#0 and P#1 has own (32KB) cache per thread that is
> wrong presentation if you compare with physical CPU.
> 
> This is a screenshot of AWS vs Openstack CPU Topology and looking at
> openstack its presentation is little odd, is that normal?
> 
> https://imgur.com/a/2sPwJVC
> 
> I am running CentOS7.6 with kvm 2.12 version.
>  
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