FreeBSD 5.4 network performance with SMP

Matt Hartzell mchartzell at
Sun Oct 2 15:47:31 PDT 2005

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.

Also, what sysctl settings are you using?

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

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
>freebsd-smp at mailing list
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