FreeBSD 5.4 network performance with SMP

O. Hartmann ohartman at
Sun Oct 2 16:57:09 PDT 2005

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.
> 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
>> To unsubscribe, send any mail to "freebsd-smp-unsubscribe at"
> _______________________________________________
> freebsd-smp at mailing list
> To unsubscribe, send any mail to "freebsd-smp-unsubscribe at"

I see something similar in FreeBSD 6.0-BETA5, no SMP, but with both sk0 
and nve0 NICs. This is what my vmstat -i shows up. I do not have 
attached any USB device, but there seems to be a lot of interrupt 
requests. nve0 seems to 'hang' sometimes. As I can see, nve0 and the 
sound device ocm0 (snd_ich) shares an IRQ. Can this be changed anyway?

interrupt                          total       rate
irq1: atkbd0                       15130          3
irq4: sio0                          6178          1
irq6: fdc0                            27          0
irq12: psm0                        42158         10
irq14: ata0                        13047          3
irq16: fwohci0                         1          0
irq17: skc0                            4          0
irq22: ehci0+                      11525          2
irq23: pcm0 nve0                      27          0
lapic0: timer                    8350298       1999
Total                            8438395       2020


More information about the freebsd-smp mailing list