[LAU] Ubuntu Hard real time kernel (2.6.24-21) poor performance.

[Cassiel]

You should receive answers like "hey, there's 64studio and other audio
related distros out there!!!" in a couple of hours on this list.

By the way, I am running debian lenny and using my own rt kernel.
I succesfully compiled 2.6.24 and 2.6.26 with real time patch and tried
2.6.21 from 64studio and the ubuntu studio one to learn something more using
'make oldconfig'

2.6.26 performances are good (1.5ms 32 frames/period) even if sometimes
jackd freezes and I don't know why. qjackctl load is around 30-50% with
ardour running a 14tracks mix with full fx in playback mode. Duplex mode
loads are around 60-70%

2.6.24 performances are the same but with no freezes and an increased load,
around 1-2% (same mix).

With 64studio and ubuntu studio kernels I didn't noticed the improvements I
expected...

I then started to built my own and benchmarking following (as you probably
know):
http://www.alsa-project.org/main/index.php/Low_latency_howto


For nvidia drivers have a look at this.
http://desiato.tinyplanet.ca/~lsorense/debian/debian-nvidia-dri-howto.html<http://desiato.tinyplanet.ca/%7Elsorense/debian/debian-nvidia-dri-howto.html>

Removing network/server/router... and experimentale features in the
"oldconfig/menuconfig" process helped me a lot.

regards
r



2008/10/24 John Tomlinson <normalblaster-lau at yahoo.co.uk>

> After a number of years of making successful music recordings using a
> combination of rosegarden and ardour on my Ubuntu Dapper Drake system,
> and my home grown real-time kernels, I thought it was time to upgrade to
> Hardy Heron and use the proper real time kernel that the experts had
> built. What a disappointment!
>
> I have an internal pci sound blaster live card (emu10k1 chip set) and a
> M-audio audiophile USB sound module.
>
> On my dapper installation, which happened to have 2.6.22.1 real time
> patched kernel (the default ubuntu kernel was 2.6.15), I could get
> latencies as low as 1.5ms (32 frames/period) on the sound blaster and
> 2.7ms ( 64 frames/period) on the USB Audiophile with very few xruns; so
> few xruns that I used to wonder why people posted to mailing
> lists/forums about the problem.
>
> With the stock Ubuntu 2.6.24-21rt kernel the sound blaster gives xruns
> every few seconds with no load (no recording and no playing back) at
> 23ms latency (512 frames/period) and the Audiophile struggles at 43ms
> ( 1024 frames/period); I am getting xruns every 10-20 seconds. Infact
> the rt kernel gives little, if any, improvement over the generic kernel.
>
> I have the following settings in my limits.conf
> @audio - rtprio 95
> @audio - memlock 512000
> @audio - nice -19
>
> And I have a script to set the real-time priorities for the interrupts
> for the interrupts that the sound system use - usually IRQ17 and IRQ19.
>
> My user is also a member of the audio group.
>
> I have tried the nohz=no on the kernel start up command line as
> discussed in numerous fora with no change. I did not expect one:
>
> johnt at TOMO001:/boot$ grep NO_HZ config-2.6.24-21-*
> config-2.6.24-21-generic:CONFIG_NO_HZ=y
> config-2.6.24-21-rt:# CONFIG_NO_HZ is not set
>
> I have also tried the changes described in:
>
> http://alsa.opensrc.org/index.php/Usb-audio
>
> which also made no difference.
>
> Any ideas what to try next? Have I got to go back and start build my own
> kernels again (which always involved a battle between me and the nvidia
> graphics card)?
>
> John Tomlinson
>
> _______________________________________________
> Linux-audio-user mailing list
> Linux-audio-user at lists.linuxaudio.org
> http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.linuxaudio.org/pipermail/linux-audio-user/attachments/20081024/5d5c7a86/attachment.htm