Re: Performance Problems, probably network related

[Simon Hobson <simon@xxxxxxxxxxxxxxxx>]

Klaus Darilion <klaus.darilion@xxxxxx> wrote:

> Hardware: 2 servers, hardware is more or less identical
>  
> Server 1: Ubuntu 20.04 (xen 4.11, Kernel 5.4, Linux Bridge)
> AMD EPYC 7702P 64-Core Processor
> BCM57416 10G NIC
> dom0 has 4 vCPUs
>  
> Server 2: VMware ESXi 7.0
> AMD EPYC 7543P 32-Core Processor
> BCM57414 NetXtreme-E 10Gb/25Gb
>  
>  
> VM: Ubuntu 20.04, 8vCPUs. Running Knot DNS name server. I am doing benchmark 
> tests against a VM running either on XEN or VMware.
>  
> In both cases no tuning (no cpu pinning …).
>  
> The XEN VM: 170.000 qps
> The ESX VM: 575.000 qps
>  
> So, the XEN VM is much slower than the VMware VM.

With the disclaimer that it’s now a few years since I was seriously working 
with Xen (I now only run it at home) ...

From memory, the default is that all I/O goes through a single thread in Dom0 - 
or it used to, dunno if things have changed. Naturally this is likely to create 
a bottleneck. There is an option of running the I/O in a separate domain, but 
I’ve not done it and never looked at how to or whether it might help.

Simon