@olivierlambert said in Epyc VM to VM networking slow:
I wonder about the guest kernel too (Debian 11 vs 12)
Here are my results with Debian11 vs. Debian12 on our EPYC 7313P 16-Core Processor on the same host. Fresh and fully updated VMs with 4vcpu /4GB RAM, XCP-NG guest tools 7.30.0-11 are installed.:
All tests were made 3 times showing the best result.
All tests with multiple connections were made three times -P2 /-P4/-P8/-P12/-P16 showing here the best result:
DEBIAN11>DEBIAN11
-------------------------
**root@deb11-master:~# iperf3 -c 192.168.1.95**
Connecting to host 192.168.1.95, port 5201
------------------------------------------------
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 8.84 GBytes 7.60 Gbits/sec 1687 sender
[ 5] 0.00-10.04 sec 8.84 GBytes 7.56 Gbits/sec receiver
**root@deb11-master:~# iperf3 -c 192.168.1.95 -P2**
Connecting to host 192.168.1.95, port 5201
------------------------------------------------------------
[SUM] 0.00-10.00 sec 12.0 GBytes 10.3 Gbits/sec 2484 sender
[SUM] 0.00-10.04 sec 12.0 GBytes 10.3 Gbits/sec receiver
DEBIAN12>DEBIAN12
-------------------------
**root@deb12master:~# iperf3 -c 192.168.1.98**
Connecting to host 192.168.1.98, port 5201
-----------------------------------------------
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 5.12 GBytes 4.40 Gbits/sec 953 sender
[ 5] 0.00-10.00 sec 5.12 GBytes 4.39 Gbits/sec receiver
**root@deb12master:~# iperf3 -c 192.168.1.98 -P4**
Connecting to host 192.168.1.98, port 5201
-----------------------------------------------
[SUM] 0.00-10.00 sec 3.58 GBytes 3.08 Gbits/sec 3365 sender
[SUM] 0.00-10.00 sec 3.57 GBytes 3.07 Gbits/sec receiver
Conclusion: Debian12 with kernel 6.1.55-1 compared to Debain 11 with kernel 5.10.197-1 run less performant on this EPYC host.
I will check now if I could perform the same test with a Windows VM.
Update
A quick test with two Windows 7 VMs, both with 2 vcpu / 2GB RAM have shown the best result with, the latest available Citrix guest tools are installed:
C:\Tools\Iperf3\iperf3.exe -c 192.168.1.108 -P8
In average 11.3 GBits/sec were reached.