Re: Poor performance with stable/13 and Mellanox ConnectX-6 (mlx5)

From: Andrey V. Elsukov <>
Date: Tue, 14 Jun 2022 13:45:10 UTC
13.06.2022 21:25, Mike Jakubik пишет:
> Hello,
> I have two new servers with a Mellnox ConnectX-6 card linked at 25Gb/s, 
> however, I am unable to get much more than 6Gb/s when testing with iperf3.
> The servers are Lenovo SR665 (2 x AMD EPYC 7443 24-Core Processor, 256 
> GB RAM, Mellanox ConnectX-6 Lx 10/25GbE SFP28 2-port OCP Ethernet Adapter)
> They are connected to a Dell N3224PX-ON switch. Both servers are idle 
> and not in use, with a fresh install of stable/13-ebea872f8, nothing 
> running on them except ssh, sendmail, etc.
> The same exact servers tested on Linux (fedora 34) produced nearly 3x 
> the performance (see attached screenshots), i was able to get a steady 
> 14.6Gb/s rate with nearly 0 retries shown in iperf, the performance on 
> FreeBSD seems to avg at around 6Gbs but it is very sporadic during the 
> iperf run.
> # ifconfig mce0
> mce0: flags=8863<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>          ether b8:ce:f6:81:df:6a
>          inet netmask 0xffffff00 broadcast
>          media: Ethernet 25GBase-CR <full-duplex,rxpause,txpause>
>          status: active

Do you have the same MTU size on linux machine?

WBR, Andrey V. Elsukov