Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: >= 2.6.27 RT ETA?)

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To: <linux-audio-tuning@...>
Date: Wednesday, February 4, 2009 - 8:42 am

Il giorno Tue, 03 Feb 2009 10:11:20 -0800
Fernando Lopez-Lezcano ha scritto:

> > - what's the difference between running some app realtime, say

What I meant there was (if I got how it works right):
- jackd already manages audio thread priority, which get SCHED_FIFO
and therefore can preempt every other process/thread in the system
- all other processes are sheduled SCHED_OTHER with various nice levels

So, isn't it better to schedule SCHED_RR audio processes (say lmms,
hydrogen and zynaddsubfx) so a cronjob, xorg, daemons and such can't
possibly preempt audio processes?
I think such a situation (i.e. a cronjob preempting zynaddsubfx)
would not give you xruns, but it could lead to audio dropouts
(zynaddsubfx not having time to process audio), which is as bad as xruns
'cause you lose your sound.
Same goes for any other setup in which some apps aren't connected to
jack or properly designed.

> SCHED_RR will be preempted when it uses up its time slice. That

I imagine this scenario being very close to the machine not having
enough power to fulfill the requested tasks.
If a round robin across all audio threads gives xruns a fifo on jackd's
audio thread would leave other ones with no cpu time left, I guess.

> > - apart from irq threads, is there any other big improvement a -rt

Yep, I run 2.6.28.

Thank for your reply, I've made my mind clearer on some interesting
points now.

bye,
Nicola.
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Messages in current thread:
[LAT] Hello, Gilberto Borges, (Wed Jul 30, 9:39 pm)
[LAT] Hyper Threading, Jaromír Mikeš, (Wed Sep 17, 10:43 pm)
[LAT] amd64: kernels? base system?, james of jwm-art net, (Tue Dec 2, 5:53 pm)
Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: &gt;..., Fernando Lopez-Lezcano, (Mon Feb 2, 11:08 pm)
Re: [LAT] 2.6.29-rt1, Robin Gareus, (Sat Mar 28, 1:18 pm)
[LAT] RT kernel for audio and dynamic vs static ticks, Lars-Erik Helander, (Mon Jan 18, 12:50 pm)
Re: [LAT] 2.6.29-rt1, Fernando Lopez-Lezcano, (Sat Mar 28, 6:11 pm)
Re: [LAT] 2.6.29-rt1, Ray Rashif, (Wed Apr 8, 2:54 am)
Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: &gt;..., Fernando Lopez-Lezcano, (Tue Feb 3, 6:11 pm)
Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: >..., dieeasy, (Wed Feb 4, 8:42 am)
Re: [LAT] amd64: kernels? base system?, Daniel James, (Wed Dec 3, 11:17 am)
Re: [LAT] amd64: kernels? base system?, james of jwm-art net, (Wed Dec 3, 3:29 pm)
Re: [LAT] Hyper Threading, Robin Gareus, (Thu Sep 18, 2:53 pm)
Re: [LAT] Hyper Threading, Jaromír Mikeš, (Thu Sep 18, 7:45 pm)
Re: [LAT] Hello, Andy Farnell, (Wed Jul 30, 10:00 pm)
Re: [LAT] Hello, Marcos Guglielmetti, (Wed Jul 30, 11:00 pm)
Re: [LAT] Hello, Daniel James, (Tue Aug 5, 3:12 pm)
Re: [LAT] Hello / kernels, Marcos Guglielmetti, (Wed Aug 6, 8:53 am)
Re: [LAT] Hello / kernels, Robin Gareus, (Thu Aug 7, 5:05 pm)
Re: [LAT] Hello / kernels, Marcos Guglielmetti, (Wed Aug 6, 3:36 pm)