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

[alex stone]

I'd have to agree that Hardy with 2.6.24.21 definitely doesn't perform as
well as the gutsy build. More xruns, etc..

Has anyone tested and tried a later kernel in any distro with any success?
2.6.26, 2.6.27? Is there any consequence audio/midi wise with one of these
later kernels?

Alex.


On Fri, Oct 24, 2008 at 1:13 PM, Cassiel <raffaele.morelli at gmail.com> wrote:

> 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
>>
>
>
> _______________________________________________
> 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/ccb302c0/attachment.htm