[LAU] 200 lines kernel patch

[Jouni Rinne]

On 11/20/10 20:38, Ray Rashif wrote:
> On 21 November 2010 02:33, torbenh <torbenh at gmx.de> wrote:
>> On Sat, Nov 20, 2010 at 08:26:45AM -0500, Paul Davis wrote:
>>> On Sat, Nov 20, 2010 at 4:48 AM, Atte André Jensen <atte at email.dk> wrote:
>>>> Hi
>>>>
>>>> Aparently a new, 200 lines kernel patch have been buzzing the web lately,
>>>> supposedly it should provide a much more responsive desktop.
>>>>
>>>> But this userspace alternative should be even better:
>>>> http://www.webupd8.org/2010/11/alternative-to-200-lines-kernel-patch.html
>>>>
>>>> Anyone heard of it, tried it and/or has any thoughts whether it has anything
>>>> to offer on a DAW?
>>>
>>> it doesn't look terribly relevant because a DAW is going to schedule
>>> most threads that matter with SCHED_FIFO. these threads will be
>>> scheduled by a different set of rules than SCHED_OTHER (i.e. most of
>>> the desktop threads, and the scheduling class that is affected by the
>>> patch). that's not to say it might not still make things feel a bit
>>> better, but it won't really make lower latencies possible etc. etc.. I
>>> think.
>>
>> looking at the 200lines patch... it seems to activate RT_GROUP_SCHED
>> if anybody know how the system needs to be configured, so that jackd
>> runs with this option on, it might be nice if you told us.
>>
>> if we really get kernels with this turned on soon, we better be prepared.
> 
> In fact, isn't cgroups incompatible with realtime scheduling? Not
> quite sure where I'm quoting that from but I vaguely recall something
> like that.

Cgroups (using the 'Ubuntu'-style workaround mentioned in the original article)
+ realtime scheduling works here, on Gentoo, kernel 2.6.34-r12, but needs a
little extra configuration in /etc/security/limits.d/audio.conf, please see here
http://en.gentoo-wiki.com/wiki/JACK#Kernel_Configuration

JR

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