[kvm-devel] virtio_net backport performance

[Anthony L. <ali...@us...>]

Hey Rusty et al,

I've got automatic backports of the virtio modules[1] working back to 
2.6.18.  Everything seems okay except that for any kernel with the older 
NAPI api, performance is extremely bad.  I get about 1gbit on TX with 
2.6.24 but I get somewhere around 20mbit on 2.6.22.

I had to refactor the NAPI poll function heavily to get it working with 
the old api so my suspicion is that I'm doing something wrong.  I'd 
appreciate if ya'll could take a look at it.  I've included a patch that 
only has the differences of the backported version and the latest 
version.  Pay careful attention to the COMPAT_napi blocks as these are 
what would be used on older kernels.

It's a bit ugly because it's automatically generated by an awk script.

[1] http://hg.codemonkey.ws/virtio-ext-modules

Thanks,

Anthony Liguori