Re: I/OAT ... Coming Soon ?

On Nov 15, 2007 4:22 PM, Andre Oppermann <andre_at_freebsd.org> wrote:
>
> Scott Ullrich wrote:
> > On 11/15/07, Doug Ambrisko <ambrisko_at_ambrisko.com> wrote:
> >> 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.
> >
> > 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.
>
> 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.

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