linux-kernel - Re: 2.6.21-rc3-mm1 RSDL results

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Message-Id: <200703100918.05547.kernel@kolivas.org>
Date:	Sat, 10 Mar 2007 09:18:05 +1100
From:	Con Kolivas <kernel@...ivas.org>
To:	Matt Mackall <mpm@...enic.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	akpm@...ux-foundation.org
Subject: Re: 2.6.21-rc3-mm1 RSDL results

On Saturday 10 March 2007 08:57, Con Kolivas wrote:
> On Saturday 10 March 2007 08:39, Matt Mackall wrote:
> > On Sat, Mar 10, 2007 at 08:19:18AM +1100, Con Kolivas wrote:
> > > On Saturday 10 March 2007 08:07, Con Kolivas wrote:
> > > > On Saturday 10 March 2007 07:46, Matt Mackall wrote:
> > > > > My suspicion is the problem lies in giving too much quanta to
> > > > > newly-started processes.
> > > >
> > > > Ah that's some nice detective work there. Mainline does some rather
> > > > complex accounting on sched_fork including (possibly) a whole timer
> > > > tick which rsdl does not do. make forks off continuously so what you
> > > > say may well be correct. I'll see if I can try to revert to the
> > > > mainline behaviour in sched_fork (which was obviously there for a
> > > > reason).
> > >
> > > Wow! Thanks Matt. You've found a real bug too. This seems to fix the
> > > qemu misbehaviour and bitmap errors so far too! Now can you please try
> > > this to see if it fixes your problem?
> >
> > Sorry, it's about the same. I now suspect an accounting glitch involving
> > pipe wake-ups.
> >
> > 5x memload: good
> > 5x execload: good
> > 5x forkload: good
> > 5 parallel makes: mostly good
> > make -j 5: bad
> >
> > So what's different between makes in parallel and make -j 5? Make's
> > job server uses pipe I/O to control how many jobs are running.
>
> Hmm it must be those deep pipes again then. I removed any quirks testing
> for those from mainline as I suspected it would be ok. Guess I"m wrong.

I shouldn't blame this straight up though if NO_HZ makes it better. Something 
else is going wrong... wtf though?

-- 
-ck
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