Re: 2.6: More about interactivity

[Roger Larsson <roger.larsson@skelleftea.mail.telia.com>]

On Thursday 07 August 2003 20.15, Felipe Alfaro Solana wrote:
> Just wanted to throw a few thoughts I have about the current scheduler
> and my experiences with it (well, with my specific workloads and
> applications on my little 700 Mhz PIII laptop).
>
> I feel that 2.6.0-test2-mm5 is not as smooth as 2.6.0-test2-mm2 (O10int)
> was. I am experiencing sound skips, but this time I'm not using XMMS,
> but Juk, a KDE player which uses the aRTS sound daemon, which in turn, I
> assume it uses the OSS API.

Arts uses whatever you have - i think ALSA is preferred.

>
> With X reniced at +0, the system feels not as smooth as 2.6.0-test2-mm2,
> but at least there are no sound skips. However, to gain on smoothness, I
> have chosen to renice X to -20. Renicing X to -20 makes Juk skip like
> crazy simply by dragging a window over the screen. Also, with X at -20,
> opening a long Bookmarks Konqueror menu also causes sound skips (even
> with XMMS). By now, I'm sticking at +0, but I really miss those times
> when I was running O10int and the desktop was as smooth as silk.

Wait a minute!

Arts (I think JuK only tells Arts what to play) is a realtime task - if it 
does not meet its deadline you get drop outs. X is not a realtime task 
(unless you display video using it - is X even involved in video/3D?).

But you run X at a higher priority than Arts!? Don't you? You have told the
scheduler that X is more important than Arts - and you are surpriced that
you get dropouts?

Arts should really run as SCHED_FIFO or SCHED_RR but that opens another
can of worms - audio plugins can busy lock the computer... We need 
SCHED_SOFTRR now!

But you can try to prioritize arts higher than X (arts at -20, X at -15).
Or set suid root on artswrapper to get SCHED_FIFO, and then enable realtime 
scheduling in configuration.

/RogerL

-- 
Roger Larsson
Skellefteå
Sweden