linux-kernel - Re: [RFT][PATCH] sched: scale sysctl_sched_shares_ratelimit with nr

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Date:	Wed, 30 Jul 2008 12:32:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	David Miller <davem@...emloft.net>
Cc:	vatsa@...ux.vnet.ibm.com, dhaval@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [RFT][PATCH] sched: scale sysctl_sched_shares_ratelimit with
	nr_cpus

On Wed, 2008-07-30 at 03:29 -0700, David Miller wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Wed, 30 Jul 2008 12:25:11 +0200
> 
> > Dhaval, Vatsa,
> > 
> > Could you guys give this patch a spin on the big iron and possibly tune
> > the default shares_ratelimit value to give satisfactory fairness on your
> > large machines while considering the overhead?
> > 
> > 
> > ---
> > Subject: sched: scale sysctl_sched_shares_ratelimit with nr_cpus
> > 
> > David reported that his Niagra spend a little too much time in
> > tg_shares_up(), which considering he has a large cpu count makes sense.
> > 
> > So scale the ratelimit value with the number of cpus like we do for
> > other controls as well.
> > 
> > Reported-by: David Miller <davem@...emloft.net>
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> 
> This turned out to be a false theory, and the lockdep problem I
> reported the past few days was the real culprit.
> 
> The rebalancing et al. showing up in my debugging dumps was
> just chance and not even consistent.

Ah, still I think the proposed change makes sense, but lets wait for
some test results from Dhaval and or Vatsa.. ;-)

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