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

Peter Zijlstra
2012-07-26T21:25:48Z

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@chello.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.