On 2011-01-27 17:13, Scott Lavender wrote:
On Wed, Jan 26, 2011 at 9:25 AM, David Henningsson
<david.hennings...@canonical.com
<mailto:david.hennings...@canonical.com>> wrote:
What is really the current status of the lowlatency kernel? Are we
planning to have it in universe for Natty? If so, is any work going
on in that area?
Alessio answered most of these questions, however I would like to add a
few more comments.
Alessio, would you please upload your -lowlatency kernel to the
repository since there will be a delay in the documentation? I believe
it is paramount to have the -lowlatency kernel in place for user
experience and functionality.
I also would like to note that a few items about Alessio's kernel that
have been explained to me:
* it is based on the -generic Ubuntu kernel
* it does NOT have an invasive patch as others have declared or believed
* changes in build time flags ONLY are required to build Alessio's kernel
I apologize if I am being pedantic but sometimes I feel like this is an
continually uphill battle, but it is one that I am committed.
I talked to Andy Whitcroft yesterday about providing "derivative
flavour" documentation, but he is currently busy with other tasks so
this documentation will have to wait (no prognosis given). So I
assume that waiting on that documentation is not an option.
Again, I want to reiterate my desire to get the -lowlatency kernel into
the repositories for a Natty release. Given that it is based on the
-generic Ubuntu kernel and ONLY requires compile flags I would like to
believe that this is possible.
Also, do we have any signs of this kernel performing better than the
generic one? (As for bug 690010, that's fixed upstream now, and will
be fixed in the generic kernel on the next Natty kernel upload.)
My experience is that the -lowlatency performs in a far superior manner
than the -generic one for audio work.
Using my Dell P4, 2.8ghz machine with 3 gigs memory and an MAudio Delta
44 card I test the -generic kernel using JACK and Ardour and made test
recordings of guitar. I found that the -generic kernel provided stable
performance (i.e. no xruns) at slightly over 22msecs.
Using the same machine I installed Alessio's -lowlatency kernel and
testing it in the same manner. I found that the -lowlatency kernel
provided stable performance (i.e. no xruns) at just under 3msecs.
I hope all find this information useful.
Thanks, it's the first time I've actually seen some numbers, that's
great and could point as confirmation that there is actually a need for
this kernel.
Would you (and others) mind redoing the test with the 2.6.38-1-generic
kernel? It is not yet installed by default, but you can test it with
sudo apt-get install linux-image-2.6.38-1-generic
(then reboot and choose the right kernel in grub.)
And to be fair, I guess it should be tested against a 2.6.38 version of
the lowlatency kernel as well.
I have confirmed that bug #690010 is fixed in this kernel.
--
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic
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