[LAU] Ubuntu Hard real time kernel (2.6.24-21) poor performance.

Fernando Lopez-Lezcano nando at ccrma.Stanford.EDU
Sat Dec 6 16:05:53 EST 2008

On Sat, 2008-12-06 at 01:41 -0500, Lee Revell wrote:
> On Wed, Dec 3, 2008 at 7:44 PM, Florin Andrei <florin at andrei.myip.org> wrote:
> > Fernando Lopez-Lezcano wrote:
> >>
> >> So far the most "stable" realtime kernel for me has been is
> >> (if we are talking about recent kernels, of course).
> >
> > Well, it's "good to know" that RT and its typical usage domains such as
> > music and audio processing are still a pretty low priority for the
> > kernel developers, even after all these years. :-(
> Judging from LKML activity it's actually a higher priority than ever.
> I think the issue is that the Linux audio community has not been very
> engaged with kernel development lately (except for Fernando) and
> naturally the kernel devs will assume that if no one complains to them
> then it's all good. 

Sigh, I'm not that good at all. I spent two weeks on and off on that for
nothing, at least on my builds MIDI is still not working for 2.6.26.x rt
(your suggestion - thanks! - enabled midi input to work but there was
not followup and something is still drastically wrong with the alsa
timer - apps that use it don't actually output anything). I meant to
post it but this last couple of weeks I had other priorities and posts
like "midi does not work" or "it freezes" without hard data will
probably not help either. 

... and the last few times I have posted with problems I have not
received any feedback from lkml except for you. And no forthcoming
patches to test or anything like that (with one exception for some BUG
reports but that lead nowhere). At least from the point of view of my
email account I get a lot of silence. Maybe I'm not being cc'ed? I just
can't at this point try to follow lkml directly (I did till the
beginning of this year). 

> The RT kernel work lately has been driven by
> traditional hard RT users like simulation, machine control, HPC, etc
> who all seem to be happy.

Strange. Maybe different configurations or hardware? When I try to run
2.6.26.x rt patched kernels I eventually end with a completely dead
machine, not very often (once every two days?) but it happens (I don't
currently have a way to trace what happens). And there's nothing
official AFAIK for 2.6.27.x. 

> Also the kernel RT people are focused on
> getting the RT kernel patches into mainline.

That would be sooooo good.... at least then it would _have_ to keep up
with new releases. 

At this point I'm also ready to give up and just try to find latency
problems in the vanilla kernel, find a way to trace their origins and
report that to lkml. 

-- Fernando

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