Odd Slowness on Gigabit Ethernet

[Warren Togami]

Mike Barnes wrote:
> Hi folks - got a strange little issue coming up on an FC2 server, just
> hoping someone might have seen something like it before and might be
> able to suggest an angle to attack it from.
> 
> We're seeing pretty dismal transfer rates when copying files onto the
> server. We noticed it first via Samba, but tested and it occurs when
> using SCP as well. Not sure on the exact card in the server, but it's
> using the sk98lin module. We've tested on both the 2.6.5-1.358smp and
> 2.6.6-1.435.2.3smp kernel packages.
> 
> The switch is a big Cisco thing, but we've tried it in isolation with
> just a Windows XP client on another switch too (Netgear, I think.
> Certainly not another Cisco.) - same deal. The switch ports are
> showing it's negotiated full-duplex and so forth, and we forced the
> setting manually too - no difference.
> 
> The really odd thing is that the transfer rates pick up dramatically
> if we start ANOTHER copy to the server at the same time. Don't have
> the numbers to hand, but we figured that one single copy to the server
> was running at about 1/10th or less of the network's capacity, but if
> we started another one from either the same client machine or any
> other one on the switch, they were getting about half each.
> 
> Any suggestions as to what might be happening here? We're pretty
> confident it's something at the server's end, and we're still poking
> at it, but if anyone's seen anything like this before I'd love to hear
> about it.
> 

sk98lin module seems to have problems with the FC2 kernel.  On my 
Athlon64 3200+ Asus A8V motherboard with x86-64 I get maximum speeds of 
only about 350KB/sec.  I did not notice this until I was transferring 
stuff on my local LAN though, because coincidentally 350KB/sec is the 
average speed of my cable modem.

Have you tried the FC3 or rawhide kernel?  I haven't tested it for a while.

Warren Togami
wtogami at redhat.com