Re: [PATCH] Balanced Multi Queue Scheduler ...

[Andrew Morton]

Davide Libenzi wrote:
> 
> On Sat, 29 Dec 2001, Dieter [iso-8859-15] Nützel wrote:
> 
> > Davide worte:
> > > There's a bug fix and the use of the Time Slice Split Scheduler inside the
> > > local CPUs schedulers. Versions from 0.46 to 0.52 are broken by the fixed
> > > bug so testers should use this version :
> > >
> > > http://www.xmailserver.org/linux-patches/mss-2.html#patches
> >
> > Sorry, if someone asks this before but do you think that you get some stuff
> > out of it for 2.4.xx?
> >
> > Your numbers for the 8 SMP system are great.
> > Can't wait to do some tests on my poor single 1 GHz Athlon II and soon dual
> > Athlon MP/XP 1600+ on an MS 6501 (AMD 760MPX).
> >
> > Maybe my MP3/Ogg-Vorbis hiccup during dbench 32+ are solved?
> > Currently running latest 2.4.17+preempt (do think that can be mixed with your
> > new scheduler?).
> 
> The new patch need ver >= 2.5.2-pre3 because Linus merged the Time Slice
> Split Scheduler and making it to apply to 2.4.x could be a pain in the b*tt.
> Yes, as i expected numbers on big SMP are very good but still i don't
> think that this can help you with your problem.

I would expect the audio dropouts to be due to disk read latencies
and insufficiently large buffers in the audio app, and/or failure
of that audio app to mlock itself down.

If it's scheduling latency, which I doubt, I yesterday put out
a 2.4.17 low-latency patch which has a worst-case latency which is
two orders of magnitude less that the preemptive kernel's.  The
lock-break patch will improve the preempt patch's worst case.
http://www.zip.com.au/~akpm/linux/2.4.17-low-latency.patch.gz

> It'd be nice to have inside local_irq_disable()/enable() a cycle counter
> sampler to see what is the worst case path with disabled irqs.
> 

http://www.zip.com.au/~akpm/linux/#intlat

This tool needs a bit of maintenance work, but it can measure and identify
the source of worst-case interrupt latencies quite successfully.

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