1

While using FreeBSD 11 on Google Compute engine creating a vpn with openvpn & l2tp (mpd), I notice that the network speed was extreamly slow, first I disable the TSO:

ifconfig vtnet0 -tso

But didn't work, therefore I disable the full vtnet checksum offload by adding this line to the /boot/loader.conf file:

hw.vtnet.csum_disable="1"

After doing that network speed boosted noticeable.

But wondering if this could raise other issues or is totally fine to disable it been an virtual environment?

Improve this question

1 Answer 1

Reset to default
0

In short, i don't see any downside in your case disabling CSUM.

That setting helps when you use a network card with support for hardware checksuming. On virtualized guests that means that if the host supports that your guest's virtual network driver will ask the host's driver to handle that job.

Disabling it means that your virtual CPU(s) will do that work.

As long as you're getting better performance just keep it off.

Improve this answer
2
  • If the guest VM delegate the checksum task to the main host when enabling the csum, the slowness could related due the fact that the main host is configured to behave in this manner ? could this be also the reason of why small instances have low network performance since all the checksum needs to be also handled by the cpu of the instance?
    – nbari
    Commented Nov 29, 2016 at 17:37
  • Not sure about the cause, can be anything, can be a lot of guests running on the same physical host overloading the NIC's engine, but i'm wildguessing. Anyway, I had a similar problem on linux guests under VMware, but in my case i solved disabling TSO, CSUM didn't helped much. Just keep an eye on your CPU utilization before and after disabling it
    – Fredi
    Commented Nov 29, 2016 at 17:44

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .