[Gllug] Observed speed of gigabit ethernet only about 1/4 or 1/5 of advertised

[Kostas Georgiou]

On Sat, Jul 14, 2007 at 02:52:28PM +0100, Richard Jones wrote:

> Hi, I've just got a new gigabit ethernet switch to replace my ancient
> 10 Mbps home switch.  The old switch easily maxed out at 10 Mbps.
> 
> With the other ports on the switch idle and two machines connected
> through gigabit ethernet, I'm seeing 220 Mbps with ssh.  That's about
> a quarter of what I'd expect to be the theoretical maximum.
> Surprisingly with ttcp it's slower -- 170 Mbps, or about one fifth of
> the theoretical max.  With UDP it's little better -- 195 Mbps.
> 
> I wonder if someone can suggest from the description below where the
> weak point is likely to be in this setup.  Crappy on-board ethernet?
> SoHo switch?  PCI bus or processor speeds?  Or does everyone with
> gigabit ethernet only see a fraction of the advertised throughput?
> 
>   Machine A:
> 
>     eth0: VIA Networking Velocity Family Gigabit Ethernet Adapter
>     AMD Athlon(tm) 64 Processor 3200+ (2043.109 MHz)
>     2 GB RAM
> 
>   Machine B:
> 
>     eth0: forcedeth.c: subsystem: 010f1:2915 bound to 0000:00:08.0
>     Quad AMD Opteron(tm) Processor 2220 (2814 MHz)
>     4 GB RAM
> 
>   Switch:
> 
>     Netgear GS105 5-port Gigabit Ethernet Switch

I am pretty sure I've seen speeds above 800Mbit/sec on this switch
so the problem isn't there. Connecting the machines directly will
easilly tell you if this is the case.

The nvidia NIC should be connected to a bus that can handle gigabit
speeds but I am not sure about the quality of the driver, as always
nvidia hasn't released any info and the driver is the result of reverse
engineering the nvidia binary module. I think most of the problems
on the driver have been fixed now but you never know.

Cheers,
Kostas


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