Re: [LAU] Too many xruns

On 11 October 2012 at 9:07, Jeremy Jongepier <jeremy@email-addr-hidden> wrote:

> On 10/11/2012 08:33 AM, Kevin Cosgrove wrote:
> >
> >> More information on tweaking your setup:
> >> http://wiki.linuxmusicians.com/doku.php?id=system_configuration
> >
> > I've been trying to reduce my xrun troubles. I'm down from > 10
> > xruns per second to something more like 10 xruns per minute. Still
> > not good, but better.
> >
> > I used the realTimeConfigQuickScan.pl script to diagnose things.
> >
> > https://code.google.com/p/realtimeconfigquickscan/
> >
> > I'm down to three things reported as "not good" now.
> >
> > 1. Checking checking sysctl inotify max_user_watches... < 524288 - not good
> > increase max_user_watches by adding 'fs.inotify.max_user_watches = 524288'
> > to /etc/sysctl.conf and rebooting
> > For more information, see
> > http://wiki.linuxmusicians.com/doku.php?id=system_configuration#sysctl.conf
> >
> > Looking at the link there's a comment, "...it remains very
> > unclear ... if adjusting this value actually does anything at
> > all." So, I haven't altered this. Does anyone have
> > experience saying that this helped them?
> >
>
> Hello Kevin,
>
> I've added this comment after having asked the exact same question at my
> LAC2011 workshop. Nobody in the audience could acknowledge that changing
> the inotify setting helped anything.

Nice to know.

> > 2. chrt: failed to set pid 0's policy: Operation not permitted
> > Checking the ability to prioritize processes with chrt... no - not good
> > Could not assign a 80 rtprio value. Set up limits.conf.
> > For more information, see
> > http://wiki.linuxmusicians.com/doku.php?id=system_configuration#limits.conf
> >
> > I did make the changes outlined at the above link. I still
> > get the above report. I'm going to guess that I need some
> > real-time support from the kernel to make this work. Which
> > brings me to
> >
> > 3. Kernel with Real-Time Preemption... not found - not good
> > Kernel without real-time capabilities found
> > For more information, see
> > http://wiki.linuxmusicians.com/doku.php?id=system_configuration#installing_a_real-time_kernel
> >
> > First I looked at this link:
> > http://wiki.linuxmusicians.com/doku.php?id=system_configuration#the_kernel
> > Specifically, I looked at the threadirqs kernel option.
> >
> > grep -e CONFIG_IRQ_FORCED_THREADING=y -e CONFIG_PREEMPT=y /boot/config-`uname -r`
> > produces "CONFIG_IRQ_FORCED_THREADING=y" and I think that's good.
> >
>
> No it's not, unless it also outputs CONFIG_PREEMPT=y. if it doesn't than
> your kernel isn't preemtible and in that case I doubt if threadirqs or
> even chrt works (no expert on this).

A comment at the above link says, "If [the grep command]
returns CONFIG_IRQ_FORCED_THREADING=y and CONFIG_PREEMPT=y
then your kernel is using IRQ threading and you don't have
to proceed with the following steps. If it only returns
CONFIG_IRQ_FORCED_THREADING=y you can add the threadirqs boot
option as described..." My grep was in the 2nd case, with
only CONFIG_IRQ_FORCED_THREADING set to "y", so I proceeded
with the rest of the "threadirqs" instructions related to grub.
That didn't seem to work.

> > I altered my /boot/grub2/grub.cfg file to include
> > "threadirqs" on the stanza for my kernel, like so, but
> > without all the line breaks.
> >
> > linux /boot/vmlinuz-3.5.5-2.fc17.x86_64
> > root=UUID=77edf07a-a49b-48dd-82c8-2f9e5c8691b7 ro nomodeset
> > rd.md=0 rd.lvm=0 rd.dm=0 SYSFONT=True KEYTABLE=us rd.luks=0
> > LANG=en_US.UTF-8 rhgb quiet threadirqs nouveau.modeset=0
> > rd.driver.blacklist=nouveau
> >
>
> Slightly OT, but wow, that's a whole lot of kernel options ;) I only use
> two or three.

I left all of that in there from Fedora's installation of the kernel.

> Check if your kernel is preemtible (at least, I think that might be a
> probable cause) or install a kernel that is preemtible

# CONFIG_PREEMPT_RCU is not set
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set

> (there's no real-time kernel available for FC17?).

CCRMA has kernel-rt-3.4.11-1.rt19.2.fc17.ccrma.x86_64 but it
doesn't play nicely with my nVidia card and X config. I changed
the X config to use the nouveau driver, which got it to boot to
level 5 at least. But the geometry is not good and that driver
ignores my 2nd display. I found A LOT of potentially useful
information with a websearch for enabling an nVidia driver with a
CCRMA kernel. Sorting that out is a possibility.

Thanks....

--
Kevin
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user@email-addr-hidden
http://lists.linuxaudio.org/listinfo/linux-audio-user