lowlatency kernel status?

Scott Lavender scottalavender at gmail.com
Thu Jan 27 16:13:39 UTC 2011

On Wed, Jan 26, 2011 at 9:25 AM, David Henningsson <
david.henningsson at 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

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.

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