From: Philippe Gerum <rpm@xenomai.org>
To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: xenomai@xenomai.org
Subject: Re: [Xenomai-help] Is xenomai OK for early boot purpose ?
Date: Mon, 31 Jan 2011 11:53:54 +0100 [thread overview]
Message-ID: <1296471234.2214.38.camel@domain.hid> (raw)
In-Reply-To: <4D469437.9050902@domain.hid>
On Mon, 2011-01-31 at 11:51 +0100, Gilles Chanteperdrix wrote:
> 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.
Yeah, I suspect that longer periods ( >= 10 ms ) may introduce more
opportunities for cache eviction due to linux activity, and therefore
higher jittery, even if bounded.
>
> >
> >> - 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.
>
--
Philippe.
next prev parent reply other threads:[~2011-01-31 10:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-31 8:55 [Xenomai-help] Is xenomai OK for early boot purpose ? gryma biloy
2011-01-31 10:32 ` Philippe Gerum
2011-01-31 10:51 ` Gilles Chanteperdrix
2011-01-31 10:53 ` Philippe Gerum [this message]
2011-01-31 11:01 ` gryma biloy
2011-01-31 11:12 ` Philippe Gerum
2011-01-31 11:17 ` Gilles Chanteperdrix
2011-01-31 11:22 ` Philippe Gerum
2011-01-31 11:14 ` Gilles Chanteperdrix
2011-01-31 14:27 ` Gilles Chanteperdrix
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