realtek performance (was Re: good ATI chipset results)

John Baldwin jhb at
Thu Oct 13 10:02:17 PDT 2005

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
> >
> >
> >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?

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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