Intel 82550 Pro/100 Ethernet and TSO troubles

[YongHyeon PYUN]

On Thu, Dec 15, 2011 at 03:16:51PM +0100, Andrea Venturoli wrote:
> On 12/14/11 22:32, YongHyeon PYUN wrote:
> 
> >>Wireshark showed some wrong checksums (I believe on the ICMP packet, but
> >>I might remember wrong).
> >
> >You can check whether you received bad checksummed frames with
> >netstat(1).
> 
> I tried "netstat -ind", but it shows no Ierrs/Idrop/Oerrs/Odrop.
> 

Use -s option which will show statistics for each network
protocols.  Search 'discarded for bad checksums' from the output.

> 
> 
> 
> 
> >Is simple downloading from client to server is enough to trigger
> >the issue?
> 
> Yes and no.
> Depending on where the client is located (on the Internet) and/or the 
> protocol used, I get either failures or ridicuolous performance (i.e. 
> 58-60kB/s without TSO vs. 1-2kB/s with TSO).
> 
> 
> 
> 
> 
> >Packet capture that shows the problem would be great to
> >know what's going on here.
> 
> I'll send them to you privately.
> 
> You'll see tso.dump and notso.dump: they are both from the same client 
> downloading the same (random) file (the file name was changed only  to 
> prevent possible caching).
> See notso.dump is perfect, while tso.dump shows a lot of potential problems.
> 

Thanks.

> 
> 
> 
> 
> >>Would you try attached patch and let me know it goes?
> >Sorry, it seems extra pull up for TCP payload may not be required
> >here.  Try this instead.
> 
> I see a little increase in performance (2-3kB/s instead of 1-2kB/s); 
> this might however well depend on external factors. Still it is very 
> different from what I'm get without TSO.
> 

Thanks for testing. Based on dump file, I tried various MTU
configuration and I was not able to reproduce it.  By chance, are
you using firewall(pf/ipfw/ipf) or bridge(4)?  If I remember
correctly some firewall rules are not compatible with TSO.
For bridge, if one member of bridge does not support TSO, TSO
should be disabled.

> 
> 
>  bye & Thanks
> 	av.
> 
> P.S. I can live well without TSO; I'm just doing this to let the 
> software improve. Go ahead only if *you* are interested.

I do care driver stability so it would be great if I manage to
address the issue. :-)