Re: I/OAT ... Coming Soon ?

On Nov 15, 2007 4:25 PM, Jack Vogel <jfvogel_at_gmail.com> wrote:
>
> 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
>

OH, and I should quickly add, that this only makes sense with hardware
that supports it, ie with MSI/X.

Jack