Re: [Xenomai-help] native kernel task example

[Jan Kiszka <jan.kiszka@domain.hid>]

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Ramon wrote:
> Hi,
> 
> I have a system developed (teaching and research purposes) developed in
> RTLinuxfree and currently I'm trying to migrate
> this system to Xenomai (several task periodical task with period of
> 100us (one at 50us)).
> As a first step I would like to run them at kernel level to preserve
> performance (hard realtime),

Unless your system is already running on its limits with this 20 KHz
job, kernel vs. user space won't make the big difference. Check the
results of the latency test while loading the system with I/O and memory
cache stress to get a first impression.

> latter I will try to migrate
> user space.

Specifically while trying to stabilize the port, you will quickly love
the robustness of user space: if something crashes or hangs, just attach
gdb - but don't forget to enable the Xenomai watchdog in order to catch
runaway tasks.

> 
> This task contains low level  commands (out, in commands to access AD/DA
> card registers)

iopl(3) will grant your root user space process in/out privileges. Not
nice, but probably easier as a first step than porting over the Analogy
framework.

Jan

PS: Specifically for educational purposes, it is a bad idea to continue
spreading the legacy concept of kernel-based RT applications.


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