[Rtai] Memory size in Kernel Space.

Paolo Mantegazza mantegazza at aero.polimi.it
Thu Dec 10 11:55:19 CET 2009

Nael AL_Sheakh Ameen wrote:
> Greetings!
> I'm wondering if someone can tell me how much memory is available when the program is running in Kerenl Space.

The whole memory available to the kernel. For RTAI applications the part 
Linux has not consumed (yet). From an RTAI based usage point of view it 
depends on how you manage memory, i.e. if you prepare everything at 
module init you can use Linux allocations, if you want to do it lively 
in real time you have to use the RTAI heap. So care of setting RTAI heap 
size to as high a value as you need. Notice that RTAI own kernel tasks 
stacks use that heap too. If you want to work with large stacks use the 
kscheduler. You'll be constrained to 4/8K otherwise, the size of the 
stack of Linux kernel threads, otherwise.

> And How can I Know that and how observe the memory usage.

If I'm not wrong Linux own memory usage is seen with "top" and "cat 
/proc/meminfo". RTAI own heap consumption can be followed with "cat 
/pro	c/rtai/scheduler".


> With Best regards
>     Nael_NAS
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