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

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To: Fernando Lopez-Lezcano <nando@...>
Cc: <linux-audio-user@...>, <linux-audio-tuning@...>, <torbenh@...>
Date: Sunday, February 1, 2009 - 3:42 am

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Fernando Lopez-Lezcano wrote:

surely they are.

$ lspci | grep Audio
00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High
Definition Audio Controller (rev 02)

The RT patch does two things:
It allows to prioritize interrupts and it [almost] guarantees real-time
scheduling for a dedicated process or thread.

While the soundcard is low bandwith on the PCI bus, IRQ prio may still
be required to override HDD and [sometimes] graphics I/O; at least when
playing or recording many tracks. NTL, you can get a perfect x-run free
system without the RT patch; you can just not rely on it to be as x-run
free as a RT patched kernel ;)

>> and i havent really seen xruns which i could not relate to some

I just booted into a vanilla 2.6.28.2 #1 SMP PREEMPT

right, there's no realtime patch, yet running jackd at 64 * 3 @48kSPS on
a HDA - ardour2 with 12 tracks, a couple of LADSPA effects and jamin
(lots of CPU!) - there's no xruns yet!

I'll be back in the studio in two weeks from now to test it with USB and
1394 devices. With <=2.6.24 kernels those were always working more
reliably that the HDA so I don't expect problems there.

BTW. with 2.6.28 I needed to

`echo -1 > /proc/sys/kernel/sched_rt_runtime_us`

or edit /etc/sysctl.conf and add
sys.kernel.sched_rt_runtime_us = -1

before JACK was able to acquire real-time privileges.

Here's my .config running running debian/lenny+sid on a Thinkpad X60s:
http://mir.dnsalias.com/_media/wiki/kernel/config-2.6.28.2.txt

robin

PS. I bumped into Linus at LCA: 2.6.27 still had various issues with the
"big kernel lock" in some modules - most notably vfat - but they should
be pretty much gone by now. YAY!
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Messages in current thread:
[Linux-audio-tuning] test, MarcOChapeau, (Sun Jul 27, 11:34 am)
[LAT] hello, dyne:bolic -rt and freeeee, jaromil, (Wed Sep 10, 2:06 pm)
[LAT] BIOS and IRQ, Grammostola Rosea, (Wed Nov 26, 8:55 pm)
Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: >..., Robin Gareus, (Sun Feb 1, 3:42 am)
[LAT] Setting up a performance synth, David McClanahan, (Wed Jan 13, 9:55 pm)
[LAT] We're back online !, Marc-Olivier Barre, (Thu Apr 22, 8:10 pm)
[LAT] presonus firebox and 2.6.31-9-rt gives tons of xruns, yvan volochine, (Tue May 18, 10:45 am)
[LAT] Document on using Jack Apps, Arvind Venkatasubramanian..., (Sat Jul 31, 10:23 pm)
[LAT] rt kernel 2.6.39, Emanuel Rumpf, (Sun May 29, 11:56 am)
[LAT] To much latency, Dave Stikkolorum, (Sun Oct 30, 11:02 am)
[LAT] 3.x kernel, Emanuel Rumpf, (Wed May 2, 8:48 pm)
Re: [LAT] 3.x kernel, Robin Gareus, (Wed May 2, 8:51 pm)
Re: [LAT] To much latency, Jeremy Jongepier, (Sun Oct 30, 11:25 am)
Re: [LAT] To much latency, Dave Stikkolorum, (Sun Oct 30, 11:55 am)
Re: [LAT] To much latency, Jeremy Jongepier, (Sun Oct 30, 12:03 pm)
Re: [LAT] To much latency, Dave Stikkolorum, (Sun Oct 30, 12:23 pm)
Re: [LAT] To much latency, Jeremy Jongepier, (Sun Oct 30, 1:50 pm)
Re: [LAT] To much latency, Dave Stikkolorum, (Sun Oct 30, 2:13 pm)
Re: [LAT] To much latency, Jeremy Jongepier, (Sun Oct 30, 2:19 pm)
Re: [LAT] To much latency, Dave Stikkolorum, (Sun Oct 30, 2:39 pm)
Re: [LAT] To much latency, Jeremy Jongepier, (Mon Oct 31, 11:59 am)
Re: [LAT] To much latency, Dave Stikkolorum, (Tue Nov 1, 4:17 pm)
Re: [LAT] To much latency, Jeremy Jongepier, (Wed Nov 2, 5:34 pm)
Re: [LAT] To much latency, Rafael Vega, (Tue Nov 1, 12:25 am)
Re: [LAT] To much latency, Daniel James, (Tue Nov 1, 10:04 am)
Re: [LAT] To much latency, Rafael Vega, (Thu Nov 3, 12:33 pm)
Re: [LAT] To much latency, email.rafa@gmail.com, (Thu Dec 22, 2:50 pm)
Re: [LAT] rt kernel 2.6.39, Robin Gareus, (Sun May 29, 1:43 pm)
Re: [LAT] rt kernel 2.6.39, Emanuel Rumpf, (Sun May 29, 2:39 pm)
Re: [LAT] rt kernel 2.6.39, Robin Gareus, (Mon May 30, 3:52 pm)
Re: [LAT] Document on using Jack Apps, Daniel James, (Tue Aug 3, 6:48 pm)
Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: &gt;..., Lars-Erik Helander, (Mon Feb 2, 8:53 am)
Re: [LAT] [LAU] Are RT-patches needed anymore? (Was Re: &gt;..., Fernando Lopez-Lezcano, (Mon Feb 2, 6:35 pm)