Advice on a multithreaded netisr patch?

H.Fazaeli fazaeli at
Wed Apr 8 15:35:13 PDT 2009

   Dear Jack
   Can you please comment on below statements ?!
   Is the assertion true for all OSes (windows, linux, ...) or it
   is just freebsd? I am actually concerned in how much production
   ready is igb drivers in your opinion.
   As a matter of fact, We have been (and are) using em drivers for years
   production systems in biggest ICPs/ISPs/organizations without problem
   and we
   have very good faith in it (I have not tested igb).
   Barney Cordoba wrote:

--- On Tue, 4/7/09, Ivan Voras [1]<ivoras at> wrote:

From: Ivan Voras [2]<ivoras at>
Subject: Re: Advice on a multithreaded netisr patch?
To: [3]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
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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Best regards.

Hooman Fazaeli [7]<hf at>
Sepehr S. T. Co. Ltd.

Web: [8]
Tel: (9821)88975701-2
Fax: (9821)88983352


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