Took me good few hours to find out why specific combination of task performs incredibly slowly on my server.

For reference, in my case it’s port-forwarded ssh/https connection over openvpn.

[ Client ] --(Internet)--> [ Gateway ] --(OpenVPN)--> [ Server (SSH) ]

Doing anything which takes up bandwidth (displaying log files, etc) will shoot the cpu load (at interrupt) up by a lot. By a lot I mean over 50% of one core.

This guy have the reasoning why it’s happening but I don’t know how much of it is correct. VMware support page also suggesting disabling it if network performance is slow.

In FreeBSD it’s:

echo 'net.inet.tcp.tso=0' >> /etc/sysctl.conf

In Windows it’s this .reg file:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"DisableTaskOffload"=dword:00000001

It seems to involve a shell script in Linux so I won’t bother writing it off here since it differs by system.

As usual, YMMV.

…and there goes my time 🙁