10 Gigabit Network Iperf3 Speed slow down. Why?

[Proxmoxbeginner30]

Hello to all network and proxmox experts, the following happened:
I gave my Proxmox Home Server a power saving upgrade.
After putting this together, reconnecting the Mellanox Connect X2 single port card (server) to my main Debian 11 Bullseye system via a SFP+ DAC cable from Cisco properly, it shows me 10.9 between the two when I first tested it with iperf3, currently only 3.7 unfortunately. Internally from VM to Proxmox everything fits, but the main problem is between the two systems connected directly without a switch. MTU I have set on both systems jumbo frames equals 9000 What setting can it be ?
Glad about helpful suggestions

My Specs:

Server:
CPU = Intel i3 6100
RAM = Kingston Fury DDR 4 8GB
MB = Gigabyte Q170M - D3H
System = Proxmox 7.2-7
Netzteil = Compat Power 550W
HDD = 2x 1TB NAS Platten
SSD: 2x Crucial MX 500GB und 1x Emtec X 150 120GB
Netzwerk: Mellanox Connect X2
Intel Gigabit LAN

Client:

Debian 11 (Bullseye Desktop Rechner:
CPU = Intel i5 7400
RAM = Kingston Fury DDR4 8GB
MB: = Asus Prime B250
Netzteil = Cooler Master 550W
GPU: Nvidia GTX 660ti
Netzwerk = Intel Gigabit Lan
Mellanox Connect X2

 

[gurubert]

Have you tried a new cable?

 

[Proxmoxbeginner30]

Yes I got a new one from amazon yesterday and after test got same result. Whats wrong with my system ? Mellanox plug in first pcie x16 slots in both machines

 

[damo2929]

have you tweaked the networking stack ? whats the setting on ethtool ?
what the values of settings of net core and net ipv4 from proc?

 

[Proxmoxbeginner30]

Hello damo2929,
I tweaked my Interface on both machines to MTU 9000. ethtool say this:

Settings for enp1s0:
        Supported ports: [ FIBRE ]
        Supported link modes:   10000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: No
        Supported FEC modes: Not reported
        Advertised link modes:  10000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Advertised FEC modes: Not reported
        Speed: 10000Mb/s
        Duplex: Full
        Auto-negotiation: off
        Port: FIBRE
        PHYAD: 0
        Transceiver: internal
        Supports Wake-on: d
        Wake-on: d
        Current message level: 0x00000014 (20)
                               link ifdown
        Link detected: yes

I dont know what you mean with net core and net ipv4. Please tell me command for that then I can show you my results

 

[damo2929]

Hello damo2929,
I tweaked my Interface on both machines to MTU 9000. ethtool say this:

Settings for enp1s0:
        Supported ports: [ FIBRE ]
        Supported link modes:   10000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: No
        Supported FEC modes: Not reported
        Advertised link modes:  10000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Advertised FEC modes: Not reported
        Speed: 10000Mb/s
        Duplex: Full
        Auto-negotiation: off
        Port: FIBRE
        PHYAD: 0
        Transceiver: internal
        Supports Wake-on: d
        Wake-on: d
        Current message level: 0x00000014 (20)
                               link ifdown
        Link detected: yes

I dont know what you mean with net core and net ipv4. Please tell me command for that then I can show you my results

you can find the setting in /proc/sys/net
sub folders core and ipv4

can you send the output of ethtool -k <iface>

 

[Proxmoxbeginner30]

Ok I found them. I am goinmg to uploiad this now for looking inside errors maybe ?