Re: [LAU] Too many xruns

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.

> 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).

> 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.

> "uname -r" reports "3.5.5-2.fc17.x86_64" but I don't have
> threaded IRQs.
>
> Any ideas on how to improve my IRQs? They are not alterable in the BIOS.
>
> Thanks....
>

Check if your kernel is preemtible (at least, I think that might be a
probable cause) or install a kernel that is preemtible (there's no
real-time kernel available for FC17?). But like I said, I'm no expert on
the different preemption models so I could be completely wrong.
Hopefully someone with more knowledge on this matter chimes in.

Best,

Jeremy

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

_______________________________________________
Linux-audio-user mailing list
Linux-audio-user@email-addr-hidden
http://lists.linuxaudio.org/listinfo/linux-audio-user
Received on Thu Oct 11 12:15:02 2012