[Rock-dev] Scheduler warning and realtime

[Sylvain Joyeux]

On 11/08/2012 03:27 PM, Pierre Letier wrote:
> I succeeded to build an application based on Orogen. It is currently working on a xubuntu 12.04. The application is running correctly but when I start it, I receive the following warning:
>
> 0.037 [ Warning][Thread] Lowering scheduler type to SCHED_OTHER for non-privileged users..
> 0.037 [ Warning][Activity] Lowering scheduler type to SCHED_OTHER for non-privileged users..
> Based on a google reserach, I found the following answer on the Orocos mailing list:
> http://www.orocos.org/node/1089
>
> In summary I need to change my user ulimit to use the real-time scheduler as a non-priveleged user. This solution works (I don't have anymore the warning). However, I don't know where, in my Orogen development, I specify that I want to use the real time sheduler. I don't define any realtime parameter in the deployment (I use the "automatic" deployment approach) or any priority. I was thinking that I was automatically in SCHED_OTHER from OROCOS point of view. Do you have any idea about that ?
In theory, if you don't add the .realtime tag to the deployed task, the 
warning should not appear. I thought I fixed it a while back. RTT spawns 
some threads (for isolating CORBA from the task context for instance), 
and I thought I made sure they would be spawned with the same scheduler 
than the task ... Will have to check that.
> In the future, I would like to port the component in realtime, using XENOMAI. For that I have the following questions:
>
> - Any suggestion/advices about the installation/configuration of XUBUNTU/XENOMAI/Orogen (e.g. kernel configuration). Is there specific thinks to do with orogen ?
In theory, there is nothing special to do with oroGen. In practice, we 
have not done any Xenomai work in ages, so I don't really know. We moved 
to using Linux with the RT patchset, which gives good RT performance 
without the Xenomai caveats (i.e. the normal linux-based monitoring / 
debugging tools work out of the box)
> - How the orogen codes/component have to be modified/updated to make them working in the realtime environement (modification of CMAKE ?)
orogen should be called with the --target=xenomai flag and RTT should be 
compiled for both xenomai and gnulinux.

The orogen parameter is historical in nature and we should probably make 
it completely configurable when calling CMake (i.e. cmake 
-DOROCOS_TARGET=xenomai). Automatically compiling the two configurations 
for RTT using autoproj is not supported either ... I should have a look 
at that, since it is also required by cross-compilation setups.
> - How the GUI UI have to be managed if developped on the same computer ? (of course not realtime)
I don't really understand that question ...
> - is there any documentation/tutorial about developping orogen components on realtime platforms (like Xenomai)
There was not, but now there is. I quickly wrote this without testing, 
so it might not be as accurate as one might like ;-)

    https://rock.opendfki.de/wiki/WikiStart/Toolchain/RTPlatforms

-- 
Sylvain Joyeux (Dr.Ing.)
Senior Researcher

Space & Security Robotics
Underwater Robotics

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