Routing SMP benefit

[Jeremie Le Hen]

On Fri, Dec 28, 2007 at 03:51:31PM -0800, Tiffany Snyder wrote:
> Hi Andre,
>         are those numbers for small (64 bytes) packets? Good job on pushing
> the base numbers higher on the same HW.
> 
>         What piqued my attention was the note that our forwarding
> performance doesn't scale with multiple CPUs. Which means there's a lot of
> work to be done :-) Have we taken a look at OpenSolaris' Surya
> (http://www.opensolaris.org/os/community/networking/surya-design.pdf)
> project? They allow multiple readers/single writer on the radix_node_head
> (and not a mutex as we do) and we may be able to do the same to gain some
> parallelism. There are other things in Surya that exploit multiple CPUs.
> It's definitely worth a read. DragonFlyBSD seems to achieve parallelism by
> classifying packet as flows and then redirecting the flows to different
> CPUs. OpenSolaris also does something similar. We can definitely think along
> those lines.
> 
> NOTE:
> 1) I said  multiple instead of dual CPUs on purpose.
> 2) I mentioned OpenSolaris and DragonFlyBSD as examples and to acknowledge
> the work they are doing and to show that FreeBSD is far behind and is losing
> it's lustre on continuing to be the networking platform  of choice.

A very good paper worth reading about all this by Paul Willmann, Scott
Rixner and Alan Cox:

An Evaluation of Network Stack Parallelism Strategies in Modern
Operating Systems
http://www.ece.rice.edu/~willmann/pubs/paranet_tr06-872.pdf

-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >