6.3. Enabling vhost-net zero-copy

In Red Hat Enterprise Linux 7, vhost-net zero-copy is disabled by default. To enable this action on a permanent basis, add a new file vhost-net.conf to /etc/modprobe.d with the following content:

options vhost_net  experimental_zcopytx=1

If you want to disable this again, you can run the following:

modprobe -r vhost_net

modprobe vhost_net experimental_zcopytx=0

The first command removes the old file, the second one makes a new file (like above) and disables zero-copy. You can use this to enable as well but the change will not be permanent.

To confirm that this has taken effect, check the output of cat /sys/module/vhost_net/parameters/experimental_zcopytx. It should show:

$ cat /sys/module/vhost_net/parameters/experimental_zcopytx
0