Thor Lancelot Simon wrote:
> On Wed, Jun 13, 2007 at 01:12:23AM -0700, Darren Reed wrote:
>   
>> Has anyone started to think about how NetBSD can take advantage
>> of NICs that have a larger number of rx/tx descriptor rings,
>> and/or MSI interrupts?
>>     
>
> Think, yes -- do, no.
>
>   
>> For example, would this get tied in with ALTQ or something else?
>>     
>
> Ooh, I hope not.  ALTQ is slow.
>
>   
>> Should I be able to dedicate a rx/tx ring pair to http traffic
>> and another to ssh, etc?
>>     
>
> I've been thinking about this -- I know Solaris can do this now -- and
> I have to say I'm somewhat skeptical.  Does this really save much overhead?
>   

It's not just about speeding up delivery to an application, but being
able to deliver a certain QOS too because you don't have to deal
with each queue equally.

For local delivery, if you have specific rings being served by specific
cores/cpus then it stands to reason you should see some locality of
execution style benefits.

> I might rather have the packets all land in one ring, tagged for what
> rule they've matched in classification.  Now, on the other hand, what would
> be of great performance benefit for _my_ application, at least, on a
> multiprocessor, would be the ability to use multiple rings according to
> a slightly different set of classification parameters, e.g. destination
> IP address.

I believe the standard matching for packets is a 5-tuple:
source address, destination address, protocol, source port, destination port

> That way you can avoid stomping the cache of CPU A when
> packets come in that will only ever be touched by the network stack on
> CPU B.
>   

Right, see above.

>> ...but to do any of that will require some sort of framework.
>>     
>
> Yes.  Do you know how what Sun recently did has been working out?
>   

Yes, I do...the people working on the project are my co-workers, so
this is about as involved in any NetBSD stuff as I can realisticly be.
The project to do this is known as "crossbow" and is hosted on
the opensolaris.org website at:
http://www.opensolaris.org/os/project/crossbow/

Darren