[ovs-dev] Userspace Netlink MMAP status

[Zoltan Kiss]

Hi,

I would like to ask, what's the status of enabling Netlink MMAP in the 
userspace? I'm interested to see this progressing, but digging the mail 
archive I've found it run into scalability issues:

http://openvswitch.org/pipermail/dev/2013-December/034546.html

And also it can't handle frags at the moment properly:

http://openvswitch.org/pipermail/dev/2014-March/037337.html

I was thinking about this scalability issue, and I think maybe we 
shouldn't stick to the 16 KB frame size. I think in most cases the 
packets we are actually sending up are small ones, in case of TCP the 
packets of the handshakes are less than 100 bytes. And for the rest, we 
can call genlmsg_new_unicast() with the full packet size, so it will 
fall back to non-mmaped communication. And this would solve the 
frag-handling problem as well.
Another approach to keep the frame size lower is to pass references to 
the frags, which would point outside the ring buffer, to the actual page 
(which need to be mapped for the userspace). I don't know how feasible 
would that be, but huge linear buffers also has to be sliced up to frags.

Regards,

Zoli