Hi,

Anyone can help?

Thanks

Patrick

Hi all,

I am using libvirt for more than 10 years, and I have installed it on lot of servers, with dozens of VMs. Network performances from VMs to host have always been at top.

But first time I am in front of this problem:

Replacing an old platform made of 2 servers Fedora (36 upgraded to) 37 by 2 servers (H/W stronger) with Fedora 39, same .qcow2 diskimages for VMs, I found out that response times are 2,5 times higher on the new platform than the old one.

I have check H/W, new are better.

I have check standard network configuration, identical, virtio is best (same as older) like I saw in my google searches.

Then I checked network performances:

On old platform, from VM1 to guest:
iperf3

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  27.7 GBytes  23.8 Gbits/sec    0             sender
[  5]   0.00-10.00  sec  27.7 GBytes  23.8 Gbits/sec                  receiver

On new platform:

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  2.67 GBytes  2.29 Gbits/sec   17             sender
[  5]   0.00-10.00  sec  2.67 GBytes  2.29 Gbits/sec                  receiver

So intrinsic network performances are ten times better on old platform.

All VMs network definitions are identical:

   <interface type='network'>
     <mac address='52:54:xx:yy:zz:53'/>
     <source network='default'/>
     <model type='virtio'/>
     <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
   </interface>

On the host:
<network>
 <name>default</name>
 <uuid>cfcfeeb6-3aa2-4732-9ca4-caf5b6554f2a</uuid>
 <forward mode='nat'/>
 <bridge name='virbr0' stp='on' delay='0'/>
 <mac address='52:54:00:82:33:0c'/>
 <ip address='10.0.10.1' netmask='255.255.255.0'>
   <dhcp>
       <range start='10.0.10.170' end='10.0.10.195'/>
   </dhcp>
 </ip>
</network>

chatGPT has no clue too.

May I have some help?

Thx

Patrick