FreeBSD 5.4 network performance with SMP

Robert Lindgren robert at
Mon Oct 3 00:39:24 PDT 2005

On Monday 03 October 2005 00:47, Matt Hartzell wrote:
> In my experience I had to disable the USB in the bios.
> Do a quick vmstat -i  and note how many interrupts are on the uhci
> device - with no devices even connected to the usb bus.

uhci isn't loaded. It's not comipiled in my kernels at all.

> Also, what sysctl settings are you using?

I use the standard settings.

> If your network supports it, how about using jumbo frames?

We would I do that? It works OK with a UP kernel, so why should I need to use 
jumbo frames on a SMP kernel? I've never had to do that on 4.11 for example 
and I'm confident that jumbo frames won't help me at all.

> Robert Lindgren wrote:
> >Hi All,
> >
> >I have a strange little problem on Dell 1800's. If HT,SMP is enabled in
> > the kernel (5.4p7), performance on the integrated em0 is not especially
> > good, half the speed of the current 100Mbit connection. This is true from
> > the server and a little better to  the server. On a pci rl0 card in the
> > same machine performance is even worse. About 15Mbit from the server!
> >
> >Then I read a lot of people having poor performance from the rl0 cards and
> > a lot of FreeBSD people bashing it for being crap, even in the source
> > code for the module it's stated that these cards aren't so good. I guess
> > that is right to some extent but not 15Mbit/sec.
> >
> >So when I rebuilt the kernel without HT and SMP I get full wirespeed from
> > the em0 and the rl0 (100Mbit/sec). Is there anything I've been doing
> > wrong to get hit by this poor performance with the SMP kernel. I read the
> > disabling USB could improve performance but tried that with the HT kernel
> > without any luck.
> >
> >The server has 1 3Ghz cpu, and I would prefer too run a HT enabled kernel,
> > but not with that kind of performance, so please advice. The same
> > machines (Dell 1800) run linux with HT enabled without any network
> > performance degradation.
> >
> >Best regards
> >Robert Lindgren
> >
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> >
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