Fix Proxmox VE Slow Downloads on a Dedicated Server

Objective

Some Dedicated Servers equipped with Broadcom BCM57502 NICs may experience really slow (as low as 255 kb/s) download speeds inside VMs or containers running on Proxmox VE (Virtual Environment).

Find out how to fix slow downloads problems inside containers and VMs running on Proxmox VE with a Broadcom BCM57502 network interface controller by disabling the generic-receive-offload parameter.

Requirements

The issue is known to occur on bare metal servers of the ADVANCE ranges running Proxmox VE. Only servers equipped with a Broadcom BCM57502 network interface controller are affected.

Instructions

Step 1 - Identifying your network interface controller

SSH into the server and run the following command which lists all PCI devices of class 200 (Ethernet controllers):

lspci -nnd ::200

If the output shows devices with PCI ID 14e4:1752, your server is affected. Example output:

02:00.0 Ethernet controller [0200]: Broadcom Inc. and subsidiaries BCM57502 NetXtreme-E 10Gb/25Gb/40Gb/50Gb Ethernet [14e4:1752] (rev 12)
02:00.1 Ethernet controller [0200]: Broadcom Inc. and subsidiaries BCM57502 NetXtreme-E 10Gb/25Gb/40Gb/50Gb Ethernet [14e4:1752] (rev 12)

Step 2 - Obtaining the network interface names

List network interfaces with:

ip -brief link show

Example output:

lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
enp2s0f0np0      UP             9c:6b:00:12:34:56 <BROADCAST,MULTICAST,UP,LOWER_UP>
enp2s0f1np1      DOWN           9c:6b:00:12:34:57 <BROADCAST,MULTICAST>
vmbr0            UP             9c:6b:00:12:34:56 <BROADCAST,MULTICAST,UP,LOWER_UP>

To find the interfaces that correspond to the Broadcom controllers shown by lspci, you can run:

ethtool -i enp2s0f0np0

Example output:

driver: bnxt_en
version: 6.8.12-5-pve
firmware-version: 229.0.121.0/pkg N/A
expansion-rom-version:
bus-info: 0000:02:00.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

The bus-info line matches the PCI address (02:00.0 shown by lspci).

Step 3 - Disabling the generic-receive-offload parameter

You can now check the status of the generic-receive-offload parameter with the following command:

ethtool --show-offload enp2s0f0np0 | grep generic-receive-offload:

Example output:

generic-receive-offload: on

The slow downloads issue can be fixed by disabling generic-receive-offload with the following command:

ethtool --offload enp2s0f0np0 generic-receive-offload off

Example output:

Actual changes:
rx-gro: off
rx-gro-hw: off [not requested]

Step 4 - Persisting the change across reboots

In order to persist the change after the next reboot, the ethtool command may be added to the appropriate interfaces in /etc/network/interfaces as an up command.

For instance:

auto lo
iface lo inet loopback

iface enp2s0f0np0 inet manual
    up ethtool --offload $IFACE generic-receive-offload off

auto vmbr0
iface vmbr0 inet static
    address <IPV4>/32
    gateway 100.64.0.1
    bridge-ports enp2s0f0np0
    bridge-stp off
    bridge-fd 0
    hwaddress 9C:6B:00:12:34:56

iface vmbr0 inet6 static
    address <IPV6>/56
    gateway fe80::1

You can now restart the networking service to apply the configuration:

systemctl restart networking.service

Go further

Proxmox VE Networking on HG/Scale Dedicated Servers

Hardware upgrade on a High Grade or Scale Dedicated Server

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