Re: [LAD] Timers, hpet, hrtimer

On Mon, 9 Nov 2009 17:43:12 +0100
<hollunder@email-addr-hidden> wrote:

> On Mon, 9 Nov 2009 16:47:07 +0100
> <hollunder@email-addr-hidden> wrote:
>
> > On Mon, 09 Nov 2009 16:40:41 +0100
> > Ralf Mardorf <ralf.mardorf@email-addr-hidden-dsl.net> wrote:
> >
> > > Emanuel Rumpf wrote:
> > > > Opening the hr-timer with rosegarden freezes my whole system
> > > > here, what could cause that ?
> > > >
> > >
> > > I guess Open Octave is based on Rosegarden. While Qtractor is fine
> > > with HR timer on my system, Open Octave freezes my system too. I
> > > only was able to push reset, resp. I didn't try magic keys.
> >
> > Hmmm, I only find system-timer in either application.
> > I recently found a line in dmesg that hpet wasn't enabled and I
> > could try the boot option hpet=force.
> > After doing this I have a /dev/hpet entry but still, only system, no
> > rt or hpet in either app.
> >
> > Also no freezes tough ;)
>
> Ralf helped me a bit further off-list.
> It seems I needed to modprobe snd-hrtimer
> Now oom pretty much freezes as well when I tell it to use that,
> qtractor doesn't complain, at least not immediately, couldn't try
> further yet.
>
> Kernel is 2.6.31.4-rt14
>
> Haven't tried this yet since I'm not sure it makes sense:
> chgrp audio /dev/hpet
>
> So even when hpet is available, hrtimer is the one to use?

Sorry for replying to myself again, but I'm still not sure about this
point:

chgrp audio /dev/hpet
... will make hpet usable for the group audio. <--?

HR Timer as sequencer source will use HPET.

Since hrtimer uses hpet if available and apps use hrtimer, why would I
need to allow some audio group to access hpet directly?
More so, changing the group of /dev/hpet seems very strange to me.

Can someone please clarify?

Regards,
Philipp
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Received on Tue Nov 10 04:15:04 2009