linux-kernel - Re: [tip:sched/balancing] sched: Add comments to find_busiest

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Date:	Thu, 26 Mar 2009 00:47:08 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Ray Lee <ray-lk@...rabbit.org>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	a.p.zijlstra@...llo.nl, dhaval@...ux.vnet.ibm.com,
	balbir@...ibm.com, bharata@...ux.vnet.ibm.com,
	suresh.b.siddha@...el.com, tglx@...utronix.de,
	nickpiggin@...oo.com.au, svaidy@...ux.vnet.ibm.com, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/balancing] sched: Add comments to
	find_busiest_group()  function

Hi Ray,
On Wed, Mar 25, 2009 at 09:04:05AM -0700, Ray Lee wrote:
> > sched: Add comments to find_busiest_group() function
> >
> > Impact: cleanup
> >
> > Add /** style comments around find_busiest_group(). Also add a few
> > explanatory comments.
> 
> ...but there are actual code changes. Hard to know if you intended to
> do that and forgot to changelog it, or if it's an unexpected hunk that
> accidentally got included:

These code changes are intentional. They improve readability and help us
categorize the various cases for which we're pretty sure that we don't
have a need to calculate the imbalance.

The fact that the code was reorganized should have been mentioned in the
changelog. My bad. Sorry :(

> 
> >        if (balance && !(*balance))
> >                goto ret;
> >
> > -       if (!sds.busiest || sds.this_load >= sds.max_load
> > -               || sds.busiest_nr_running == 0)
> > +       if (!sds.busiest || sds.busiest_nr_running == 0)
> > +               goto out_balanced;
> > +
> > +       if (sds.this_load >= sds.max_load)
> >                goto out_balanced;
> >
> >        sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
> >
> > -       if (sds.this_load >= sds.avg_load ||
> > -                       100*sds.max_load <= sd->imbalance_pct * sds.this_load)
> > +       if (sds.this_load >= sds.avg_load)
> > +               goto out_balanced;
> > +
> > +       if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
> >                goto out_balanced;
> >
> >        sds.busiest_load_per_task /= sds.busiest_nr_running;

-- 
Thanks and Regards
gautham
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