Re: [Xenomai-help] overhead

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

Steven Seeger wrote:
> The overhead was measured by only comparing cpu usage between tasks from
> the statistics collection stuff. There are some userland tasks running
> at 8khz, so apparently this is a problem for Xenomai on this board. I
> had no problem at all with these tasks in kernel space under rtai. 
> 
> There are no faults at all under /proc/xenomai/faults.
> 
> The main way I can tell something is wrong is that if my three fast
> tasks are running (8 khz in kernel space, 8 khz in userspace, and 50 hz
> in userspace) then a lower priority task will timeout and trip a
> watchdog. If I remove the IO routines from the 50hz task, then the
> others can still run.

I/O does not come for free (specifically on ISA HW - if that is the case
for you). But if you think that this makes a difference here, what about
measuring both kernel- and userland-based I/O accesses in a loop and
compare the runtime? This would also allow you to quantify the impact -
regardless if there is a difference or not.

Jan

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