Help: FreeBSD 6.3 - em driver & taskqueue & priority

Ivan Voras ivoras at
Tue Jul 8 12:23:44 UTC 2008

Joe Kuan wrote:
> Hi all,
>    I have implemented an network application in kernel space and it is
> working fine. The application involves 3 network interfaces that FreeBSD
> 6.3 can forward mbuf between em0 and em1 in a rate 1.3 - 1.4 millions
> packets per second. Em2 is used for controlling the network application.
>    The problem is that when em0 and em1 are transmitting in 1.3 - 1.4
> millions packets per second, the em2 interface becomes irresponsive.
> However, my goal is to make the kernelised network application response
> as soon as a control packet arrives in em2, ie jumps the queue ahead of
> all the packets in em0 and em1.
>    I think the problem lies on the priority set on the task structure
> are all the same for all the em devices. Am I heading in the right
> direction?

A wild theory: are the NICs separate / individual and on separate buses?
If they are not (e.g. two of them are on the same card or bus) it might
be a hardware issue.

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