Re: 2.6 vs 2.4 regression when running gnomemeeting

Christian Meder
2003-12-20T16:17:37Z

On Sat, 2003-12-20 at 12:19, Ingo Molnar wrote:
> * Christian Meder <chris@onestepahead.de> wrote:
>
> > That would leave me with two possibilities: 2.6. is doing something
> > different in the gnomemeeting case or gnomemeeting is doing something
> > different in the 2.6 case. A cursory look at the gnomemeeting sources
> > didn't give me the impression that it's doing anything which would be
> > affected by 2.6 deployment but I'll ask on the gnomemeeting-devel list
> > for advice.
>
> yep, i've looked at the source too and it doesnt do anything that
> changed in 2.6 from an interactivity POV.
>
> To analyze the precise workload that hurts gnomemeeting, could you try
> the following workload:
>
> main()
> {
> for (;;) sched_yield();
> }
>
> and run 1-2 copies of such a load-generator - does it degrade
> gnome-meeting audio just as much as eg. a kernel compile does?
>
> as a next step, does the following degrade gnomemeeting?:
>
> main()
> {
> for (;;) ;
> }
>
> my guess would be that if the yield() one degrades interactivity too
> then this is unlikely to be somehow related to the scheduler proper.
>
> If it doesnt degrade but the simple non-yield loop above does, then it's
> probably something scheduling related in the sound architecture. (eg.
> use of yield() by some codepath of the sound drivers - although they
> dont seem to be doing anything like this.)
>
> If neither of these workloads degrades gnomemeeting, but a kernel-make
> does, then it's the interactivity estimator.

Ok, the results are in. Running up to three yield-loops doesn't degrade
gnomemeeting. Running one non-yield loop does degrade gnomemeeting
_very_ slightly. Adding a second non-yield loop has approximately the
same stuttering effect as a kernel compile. Adding a third non-yield
loop makes gnomemeeting totally unusable.

All these tests were done with Nick's scheduler patch. If I should retry
with stock 2.6.0 just tell me.

Sound driver is by the way snd_es1968 in ALSA and maestro in OSS.

Christian

--
Christian Meder, email: chris@onestepahead.de

What's the railroad to me ?
I never go to see
Where it ends.
It fills a few hollows,
And makes banks for the swallows,
It sets the sand a-blowing,
And the blackberries a-growing.
(Henry David Thoreau)