linux-kernel - Re: [PATCH 2/4] sched/fair: Drop out incomplete current period when sched averages accrue

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Date:	Tue, 12 Apr 2016 21:04:54 -0700
From:	Joe Perches <joe@...ches.com>
To:	Yuyang Du <yuyang.du@...el.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Cc:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, bsegall@...gle.com, pjt@...gle.com,
	morten.rasmussen@....com, vincent.guittot@...aro.org,
	juri.lelli@....com
Subject: Re: [PATCH 2/4] sched/fair: Drop out incomplete current period when
 sched averages accrue

On Wed, 2016-04-13 at 04:14 +0800, Yuyang Du wrote:
> On Tue, Apr 12, 2016 at 01:02:58PM +0100, Dietmar Eggemann wrote:
> > On 10/04/16 23:36, Yuyang Du wrote:
> > [...]
> > > @@ -2704,11 +2694,14 @@ static __always_inline int
> > >  __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
> > >  		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
> > >  {
> > > -	u64 delta, scaled_delta, periods;
> > > -	u32 contrib;
> > > -	unsigned int delta_w, scaled_delta_w, decayed = 0;
> > > +	u64 delta;
> > > +	u32 contrib, periods;
> > >  	unsigned long scale_freq, scale_cpu;
> > >  
> > > +	/*
> > > +	 * now rolls down to a period boundary
> > > +	 */
> > > +	now = now && (u64)(~0xFFFFF);
> > This forces now to be 1.
> > 
> > s/&&/&
> Duh, :)

You could also avoid the cast:

	now &= 0xFFFFull;