realtek performance (was Re: good ATI chipset results)

[John Baldwin]

On Thursday 13 October 2005 01:07 pm, Sean McNeil wrote:
> On Thu, 2005-10-13 at 11:49 -0400, John Baldwin wrote:
> > On Thursday 13 October 2005 11:13 am, Sean McNeil wrote:
> > > On Thu, 2005-10-13 at 09:17 -0400, Mike Tancsa wrote:
> > > > Havent really seen anyone else use this board, but I have had good
> > > > luck with it so far
> > > >
> > > > http://www.ecs.com.tw/ECSWeb/Products/ProductsDetail.aspx?DetailID=50
> > > >6&Me nuID=90&LanID=0
> > > >
> > > > Its a micro ATX formfactor with built in video and the onboard NIC is
> > > > a realtek.  (Although its not the fastest NIC, its driver is stable
> > > > and mature-- especially compared to the headaches people seem to have
> > > > with the NVIDIA NICs.)
> > >
> > > Is this the RealTek 8169S Single-chip Gigabit Ethernet?
> > >
> > > For those interested, here are some changes I always use to increase
> > > the performance of the above NIC.  With these mods, I can stream over
> > > 20 MBps video multicast and do other stuff over the network without
> > > issues. Without the changes, xmit is horrible with severe UDP packet
> > > loss.
> >
> > So, I see two changes.  One is to up the number of descriptors from 32 rx
> > and 64 tx to 64 rx and 64 tx on some models and 1024 rx and 1024 tx on
> > other modules.  The other thing is that you seem to pessimize TX
> > performance by always forcing the send packets to be coalesced into one
> > mbuf (which requires doing an alloc and then copying all of the data)
> > instead of making use of scatter/gatter for sending packets.  Do you need
> > both changes or do just the higher descriptor counts make the difference?
>
> Actually, I've found that the higher descriptor counts do not make a
> noticeable difference.  The only thing that mattered was to eliminate
> the scatter/gather of sending packets.  I can't remember why I left the
> descriptor increase in there.  I think it was to get the best use out of
> the hardware.

Hmm, odd.  Scott, do you have any ideas why m_defrag() plus one descriptor 
would be faster than s/g dma for re(4)?

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org