Bad routing performance on 500Mhz Geode LX with CURRENT, ipfw and mpd5 (was: ipfw, "ip|all" proto and PPPoE -- does PPPoE packets passed to ipfw?)

[YongHyeon PYUN]

On Thu, Aug 30, 2012 at 03:32:25PM -0500, Adam Vande More wrote:
> On Thu, Aug 30, 2012 at 4:11 AM, Lev Serebryakov <lev at freebsd.org> wrote:
> 
> > Hello, Ian.
> > You wrote 30 августа 2012 г., 10:23:56:
> >
> >  >>   Yep, I'll collapse my two-rule chains in one rule.
> > IS> I guess if the issue persists, we may need to see more of your ruleset.
> >   Not a problem at all, here it is:
> >   http://lev.serebryakov.spb.ru/_sklad/firewall.ipfw
> >
> > IS> Hmm, you shouldn't see ANY pppoe traffic on ng0, only on the interface
> > IS> mpd5 uses to connect with your DSL modem/bridge.  Nor would you expect
> >   Yep. I didn't see it. My question is, really: why vr1 (my physical
> > interface, used to connect to my ISP) takes 50%+ of CPU when traffic
> > is only 40mbit/s down and about 20mbit/s up (with many connections)?
> 
> 
> Have you taken this into account from  vr(4)?
> 
> BUGS
>      The vr driver always copies transmit mbuf chains into longword-aligned
>      buffers prior to transmission in order to pacify the Rhine chips.  If
>      buffers are not aligned correctly, the chip will round the supplied
>      buffer address and begin DMAing from the wrong location.  This buffer
>      copying impairs transmit performance on slower systems but cannot be
>      avoided.  On faster machines (e.g. a Pentium II), the performance
> impact
>      is much less noticeable.

I'm not sure what controller is used in Geode LX but newer vr(4)
controllers such as VT6105/VT6105M do not have such DMA alignment
limitation of TX buffer.  vr(4) selectively enables software
workaround based on controller revision.  Manual software padding
for short frames(< 60 bytes) is still required for all VIA fast
ethernet controllers though.

vr_attach() will show what quirks are activated so you would be
able to tell whether your controller has TX DMA buffer alignment
limitation or not.