Re: [Xenomai] Context Switch with rtnet

[Jan Kiszka <jan.kiszka@web.de>]

On 2012-09-14 17:01, Franz Engel wrote:
> Hi,
> 
> I've a little problem. I'm using the rtnet.h-header and the following function:
> ret = recvfrom ( ethernetConnection.sock, &recBuffer, sizeof ( recBuffer ),0, ( struct sockaddr * ) &ethernetConnection.dest_addr,&destlen );
> 
> 
> I compiled the program with the xenomai compiling flags and library.
> 
> When I look to the xenomai state I get something like this:
> CPU  PID    MSW        CSW        PF    STAT       %CPU  NAME
>  22  0      0          834840     0     00000082    0.1  rtnet-stack
>  22  0      0          1          0     00000082    0.0  rtnet-rtpc
>   0  6262   2          2          0     00300380    0.0  qs_robotpositio
>   2  6265   2          6          0     00300380    0.0  qs_robotpositio
>   0  6266   1          1          0     00300380    0.0  robotrsiinterfa
>   1  6268   1147       2365       0     00300182    0.8  robotrsiinterfa
> 
> You can see, I get a lote of context and module switches just as the rtnet-stack itself. Is that normal?

Well, I have no clue what you configured, so I can only guess. If your
task 6268 is a pure RT task that is not supposed to interact with Linux
services, you first of all have a bug in your software stack. You should
look for the reason of those mode switches to Linux, e.g. by asking
Xenomai to raise SIGXCPU when this happens.

Regarding the rtnet-stack context switches: basically, every switch is
one packet arriving at your NIC. Either you are receiving a lot of small
but valid packets or you are on an open network, and that is basically
heavy unrelated broadcast traffic of other sources than the RT device(s).

Jan

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