serious networking (em) performance (ggate and NFS) problem

[sthaug at nethelp.no]

> I changed cables and couldn't reproduce that bad results so I changed cables 
> back but also cannot reproduce them, especially the ggate write, formerly 
> with 2,6MB/s now performs at 15MB/s, but I haven't done any polling tests 
> anymore, just interrupt driven, since Matt explained that em doesn't benefit 
> of polling in any way.
> 
> Results don't indicate a serious problem now but are still about a third of 
> what I'd expected with my hardware. Do I really need Gigahertz Class CPUs to 
> transfer 30MB/s over GbE?

I would be highly surprised if you did. When I tested this a while ago
(around FreeBSD 4.8) with a pair of Intel ISP 1100 1U servers using
Pentium 700 and Intel GigE cards (em driver), I was able to get around
700 Mbps using ttcp. This was done with a normal 32 bit 33 MHz PCI bus.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no