low-latency and preemptive for gentoo-sources

Message

wip · Post by **wip** » Wed Sep 07, 2005 5:15 pm

hi all,

i'm doing audio with alsa / jack / pure data so i was wondering about what kernel to use to have low-latency and preemptive performance for pd. i've installed gentoo-sources (2.6.10) but i'm not sure about it. does it have low-latency & preemptive patches by default? if not, how can i add those patch? do i miss something for good audio performance?

asking all this because ck-kernel and mm-sources are masked!

pat

evilben · Post by **evilben** » Wed Sep 07, 2005 10:50 pm

I was looking into this a few weeks ago, but I just decided to run everything as root. As long as you've got preemption enabled in the default kernel, I don't think the patches do much except for non-root users.

The package to give non-root users realtime priority is realtime-lsm, in portage.

kmare · Post by **kmare** » Wed Sep 07, 2005 10:55 pm

you can enable "voluntary kernel preemption" and set the "timer frequency" under "processor type and features". Low latency patches I don't think are in the main kernel.. but I think that as it is right now under 2.6.13 it should work just fine with everything...

evilben · Post by **evilben** » Wed Sep 07, 2005 11:07 pm

Must be a new feature--I don't see it in the 2.6.12 menu.

wip · Post by **wip** » Wed Sep 07, 2005 11:14 pm

where can i get (emerge?) kernel 2.6.13?

evilben · Post by **evilben** » Wed Sep 07, 2005 11:46 pm

Either do

ACCEPT_KEYWORDS="~x86" emerge gentoo-sources

or put the line

sys-kernel/gentoo-sources ~x86

in your /etc/portage/package.keywords file. Make the file if it doesn't exist.

nxsty · Post by **nxsty** » Thu Sep 08, 2005 8:34 am

evilben wrote:Must be a new feature--I don't see it in the 2.6.12 menu.

Yes it's a new feature of kernel 2.6.13 that where previously only in -mm. I used to patch my 2.6.12 with it too.

If you want even lower latencies and better performance you should try ck-sources.

wip · Post by **wip** » Thu Sep 08, 2005 1:31 pm

hi!

ck-kernel is masked, maybe a big problem?
now i'm running 2.6.13 with good results (well it think)!

thank you all,
pat

nxsty · Post by **nxsty** » Thu Sep 08, 2005 2:10 pm

No, it's just updated so often that no version ever has time to hit stable before the next release.

The staircase CPU-scheduler used in -ck has been around since 2.6.4 so it's mature and well tested.