Re: [Xenomai-help] How to chose between xenomai and preempt RT

[Adrien LECOINTRE <adrien20@domain.hid>]

Jeff Angielski wrote:
> Of course, just by choosing to use Xenomai, you don't get hard realtime. 
>   You still need to design your system and software correctly.

Yes but a software can be well designed on PREEMPT_RT as well.
I built a kernel and a filesystem with the less possible number of driver. After startup there is only an ATA driver and bash running on my system! In this situation I really doubt that a big latency can occurs.

Then if my real-time software uses a specific device I just have to write my own driver (instead of using a "basic" linux driver) if I want to know exactly what's going on my system and keep a hard real-time behavior.

Those are basics things that we always do when designing a real-time software on any RT OS.

Of course for a real-time software with a lot of non-real-time loads it's probably easier to use Xenomai and let Linux deals with loads.

I read a lot of things about PREEMPT_RT not providing hard real-time but I coudn't find any test case which shows that. My loads are probably not good enough but it shouldn't be so difficult to find a way to cause a significant latency on a supposed non-hard-real-time OS.

Adrien.