linux-kernel - Re: [ 028/108] sched/nohz: Rewrite and fix load-avg computation -- again

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Date:	Thu, 26 Jul 2012 23:25:37 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	stable@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [ 028/108] sched/nohz: Rewrite and fix load-avg computation --
 again

On Tue, 2012-07-24 at 15:06 +0100, Ben Hutchings wrote:
> On Mon, 2012-07-23 at 02:07 +0100, Ben Hutchings wrote:
> > 3.2-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > 
> > commit 5167e8d5417bf5c322a703d2927daec727ea40dd upstream.
> > 
> > Thanks to Charles Wang for spotting the defects in the current code:
> > 
> >  - If we go idle during the sample window -- after sampling, we get a
> >    negative bias because we can negate our own sample.
> > 
> >  - If we wake up during the sample window we get a positive bias
> >    because we push the sample to a known active period.
> > 
> > So rewrite the entire nohz load-avg muck once again, now adding
> > copious documentation to the code.
> [...]
> 
> Based on <http://bugs.debian.org/674153>, I think we also need:
> 
> 556061b sched/nohz: Fix rq->cpu_load[] calculations
> 5aaa0b7 sched/nohz: Fix rq->cpu_load calculations some more
> 
> Does this ('sched/nohz: Rewrite and fix load-avg computation -- again')
> depend in any way on those, or are they separate fixes?

they might touch on a few entry points but the logic is separate.

->cpu_load[] is per-cpu weight tracking for the load-balancer.




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