[LAT] Tickless kernel and realtime

[Robin Gareus]

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Maurizio De Cecco wrote:
> I am running Ubuntu studio 64 on a Thinkpad laptop (X61s), and i get
> an horrible battery life. Powertop suggest to configure the kernel
> with CONFIG_NO_HZ=y.
> 
> How does this interact with the -rt kernel (2.6.24) used in Ubuntu
> Studio ? Any good reason to don't do it ?

I can't think of any. On the contrary with NO_HZ an X60s can get down to
under 10W. I'm using tickless realtime kernels ever since the NO_HZ
option was available. At 2.6.19 I measured MIDI latency/jitter around
1kHz/1ms using NO_HZ on i686.
Audio I/O works just fine on tickless 2.6.24-rt - there are no X-Runs
with JACK under normal operation even down to 256fpp on USB.

> And in case, where i find the ubuntu studio kernel source ?

I have no idea ;) you can try `apt-cache search kernel | grep 2.6.24`
and `apt-get install linux-source-2.6.24...`

Instead of compiling your own, you can also try to use the kernel from
64studio (it's also debian based) which IIRC is tickless:
http://apt.64studio.com/64studio/stable/pool/main/l/linux-2.6/
install with `sudo dpkg -i linux-image...deb` - You can find more
information on compiling and post-compilation setup notes here:
http://64studio.com/node/504

Maybe you also find the config and patches from pure-dyne useful. They
use ubuntustudio-kernel patches and provide diffs that works with a
vanilla kernel from kernel.org - see
https://code.goto10.org/projects/puredyne/browser/live/kernel/2.6.24

HTH,
robin
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