Poor network performance in 5.4 AMD64 Snap 8 with SMP support

Robert Lindgren robert at orcafat.com
Mon Oct 10 10:10:13 PDT 2005

On Saturday 08 October 2005 01:11, Roger Skjetlein wrote:
> Hi,
> 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?

I had the same problem a couple of weeks ago, but had to settle for UP, since 
it wasn't possible to get any decent performance with SMP in 5.4.

One thing that you could try, which isn't a solution, is to run the interface 
in promiscuous mode, install trafshow and run it on the interface you have 
poor performance on. When I did that I was able to get better performance 
with SMP, in the real world the opposite would be true.


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