Advice on a multithreaded netisr patch?

Barney Cordoba barney_cordoba at
Tue Apr 7 15:24:18 PDT 2009

--- On Tue, 4/7/09, Ivan Voras <ivoras at> wrote:

> From: Ivan Voras <ivoras at>
> Subject: Re: Advice on a multithreaded netisr patch?
> To: freebsd-net at
> Date: Tuesday, April 7, 2009, 5:59 PM
> Barney Cordoba wrote:
> > 1) Multiple TX queues are not supported. There's
> some hokey code to
> > test, but it doesn't properly separate flows to
> the queues.
> > 2) 2 Rx queues don't work, so only 1 and 4 work
> > 3) With 4 queues, it just sucks up CPU under heavy
> load on 4 cpus. It will
> > blow 4 cpus at a lower load than em will with 1
> > 4) You'll need to fix DMA setup, as it sets the
> alignment requirement
> > to PAGE_SIZE. I haven't been able to convince Jack
> that its wrong, not
> > that I've tried very hard since its easy to just
> fix myself.
> Reading this thread it looks like the development of both
> Intel drivers
> is a bit stalled, doesn't it? AFAIK the em driver is
> also
> semi-officially abandoned, and both from my experience and
> others it
> looks like new development and patches are being rejected.
> Time to shop
> other hardware?

To be fair, the OS doesn't really support multiqueue yet, or has
for only a few hours, so lets not go crazy.

It makes a lot more sense to have someone on the "team" work with
Jack on improving the performance and working out the kinks. When
I asked Jack about the poor performance of if_igb, he indicated that
Intel's position is that the drivers are "just samples", which really
doesn't give anyone much confidence that they want to run their business
on them. You already  have Jack doing all of the hard work; that is 
supporting the new-chip-per-week that intel puts out, so it seems to 
me the best strategy would be to try to convince Intel that its in
their best interest to have drivers that work well so people don't 
think that their hardware stinks.

As an example, the Chelsio 10gb bypass card is $3495. and an Intel
card is ~$1000, so its a big win for the community as a whole to have
good intel drivers going forward.

My work is commercially proprietary so I can't share my code, but
I can certainly share ideas on things that I've tested and discovered.



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