Philippe Gerum wrote:
> On Mon, 2011-01-31 at 09:55 +0100, gryma biloy wrote:
>> Hello,
>>
>> On a project running Linux on a beagle board, I'd like to add the
>> following capabilities to my platform :
>> - real time processes with periodic tasks (10ms, 100ms & 200 ms) and
>> a low jitter (< 50 us)
>
> Kernel space apps then, likely. Userland apps (the recommended way)
> probably have a larger worst-case jitter on this hardware, albeit still
> below 100 us. Gilles?
Las time I checked, latency measured on a 720MHz omap3 was around 55us
with a 1ms period and 35us with a 100us period.
>
>> - early boot operations (i.e. being able to perform some tasks asap
>> after a power on reset)
>>
>> I've searched for solutions over the net and Xenomai seems to be a
>> possible candidate to fulfill
>> these constraints. Can you please share your knowledge to confirm that
>> Xenomai would make
>> the job (especially on the early boot side) ?
>>
>
> I don't see how Xenomai could directly help in any way for the early
> boot goal. If you question is about whether Xenomai initializes fast
> enough, and early enough during the linux boot process for kicking rt
> applications as soon as possible, then the answer is yes, that should
> do.
Well, user-space applications will not get started before user-space is
started, i.e. basically before root filesystem has been mounted and init
is running. You could write your real-time application as the init
application, but that would be kind of awkward.
--
Gilles.
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