Poor network performance in 5.4 AMD64 Snap 8 with SMP support

[Robert Watson]

On Sat, 8 Oct 2005, Roger Skjetlein wrote:

> I have a server with a Supermikro mainboard and two Xeon 3.0Ghz/2MB. 
> When running kernel with SMP support the network performance is very 
> poor, this is very visible on NFS traffic. When running UP kernel the 
> performance is as espected and very good.
>
> I have tried some different GB nics and the problems is static and 
> independent of modell/brand.
>
> I have also disabled as much as hardware possible, no usb, sio and etc.
>
> Typical indicator is also that the load on the box is skyrocketing when 
> it starts to serve nfs client, but the cpu load is very load.
>
> Is there any way around this problem?

Is it possible for you to test using an i386 install rather than an amd64 
install, for reference?  I use Xeon SMP test hardware in the netperf 
cluster, and have no problem saturating multiple gigabit ethernet links 
with either UP or SMP kernels.  However, all the Xeons I have access to 
are 32-bit CPUs.

Robert N M Watson