linux-kernel - Re: Ten percent test

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Date:	Mon, 9 Apr 2007 15:53:55 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Rene Herman <rene.herman@...il.com>
Cc:	Gene Heskett <gene.heskett@...il.com>,
	linux-kernel@...r.kernel.org, Con Kolivas <kernel@...ivas.org>,
	Mike Galbraith <efault@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	ck list <ck@....kolivas.org>
Subject: Re: Ten percent test


* Rene Herman <rene.herman@...il.com> wrote:

> > and that change from Mike responded to a testcase. Mike's latest 
> > changes (the ones you just tested) were mostly driven by actual 
> > testcases too, which measured long-term timeslice distribution 
> > fairness.
> 
> Ah yes, that one. Here's the next one in that series:
> 
> commit f1adad78dd2fc8edaa513e0bde92b4c64340245c
> Author: Linus Torvalds <torvalds@...osdl.org>
> Date:   Sun May 21 18:54:09 2006 -0700
> 
>     Revert "[PATCH] sched: fix interactive task starvation"

yes - in hindsight i regret having asked Mike for a "simpler" patch, 
which turned out to be rushed and plain broke your setup: my bad. And i 
completely forgot about that episode, Mike did a stream of changes in 
that timeframe and this one was indeed reverted :-/

> It personally had me wonder if _anyone_ was testing this stuff...

yes, i certainly tried it and it broke nothing, and it was in fact acked 
by Con too:

>    Signed-off-by: Mike Galbraith <efault@....de>
>    Acked-by: Ingo Molnar <mingo@...e.hu>
>    Cc: Nick Piggin <nickpiggin@...oo.com.au>
>    Acked-by: Con Kolivas <kernel@...ivas.org>
>    Signed-off-by: Andrew Morton <akpm@...l.org>
>    Signed-off-by: Linus Torvalds <torvalds@...l.org>

but it broke your setup:

>    This reverts commit 5ce74abe788a26698876e66b9c9ce7e7acc25413 (and 
>    its dependent commit 8a5bc075b8d8cf7a87b3f08fad2fba0f5d13295e), 
>    because of audio underruns.
>
>    Reported by Rene Herman <rene.herman@...access.nl>, who also 
>    pinpointed the exact cause of the underruns:
>
>      "Audio underruns galore, with only ogg123 and firefox (browsing 
>      the GIT tree online is also a nice trigger by the way).
>
>      If I back it out, everything is fine for me again."

so reverting it was justified. Basically, the approach was that the 
vanilla scheduler is working reasonably well, and that any improvement 
to it must not cause regression in areas where it already works well. 
(it obviously must have been working on your audio setup to a certain 
degree if reverting Mike's patch made the underruns go away)

In any case, it would be very nice if you could try Mike's latest patch, 
how does it work on your setup? (i've attached it)

	Ingo

View attachment "sched-mike-4.patch" of type "text/plain" (31774 bytes)