Re: I/OAT ... Coming Soon ?

On Nov 15, 2007 4:22 PM, Andre Oppermann <andre@freebsd.org> wrote:[color=blue]
>
> Scott Ullrich wrote:[color=green]
> > On 11/15/07, Doug Ambrisko <ambrisko@ambrisko.com> wrote:[color=darkred]
> >> Hmm, I forgot about the 2970 which are AMD based. Can you check the
> >> BIOS to see if there is an option to turn it on? I think this is an
> >> Intel feature. AMD might have something close? We have one 2970
> >> that we've played with a little but not much. I can't say for sure
> >> if it has it.[/color]
> >
> > Right you are. As of BIOS 1.2.2 I do not see a I/OAT option. Guess
> > I will need to pick up a different server as we are interested in what
> > kind of packet forwarding rate increase that this feature might bring
> > on a heavily loaded firewall.[/color]
>
> Not much. Unless your firewall is in usermode. Otherwise the data
> stays in the kernel and I/OAT is of not help as no copying happens.
> Your CPU is probably spending half of its clock cycles waiting on
> cache misses from newly arrived packets. Some Intel chipset integrated
> gige ports have a cache prefetch feature (duno whether our driver
> supports it) that would help quite a bit for your case.[/color]

What might help this is multiqueue support on the receive AND send,
and stack support for the same. Not sure what the stack changes
would look like, but I know there's interest in this sort of thing, so
naturally I'd be into it :)

Jack
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