Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1431819

Re: [PATCH] sched/fair: avoid !CONFIG_SMP cpufreq update callbacks when go idle

Show all headers | View raw

Dear Peter,

On Mon, 27 Jun 2016 10:37:21 +0200
Peter Zijlstra wrote:

> On Mon, Jun 27, 2016 at 03:56:03PM +0800, Jisheng Zhang wrote:
> > This is to avoid cpufreq update callbacks when we go idle on UP
> > platforms.  
> 
> How so? the patch only avoids calling the update for (!root) cgroups --
> which makes sense, but I'm not seeing how that's related to going idle,
> or UP at all.

oops, I may mis-understand below comment at cfs_rq_util_change()

                 * It will not get called when we go idle, because the idle
                 * thread is a different class (!fair),

I mis-read the comment as:

it's the "&rq->cfs == cfs_rq" check to prevent the calling when go idle.

So the patch still make sense, but I need to update the commit msg?

Thanks,
Jisheng

> 
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
> > ---
> >  kernel/sched/fair.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index bdcbeea..236ec5b 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -3121,7 +3121,8 @@ static inline void update_load_avg(struct sched_entity *se, int not_used)
> >  	struct cfs_rq *cfs_rq = cfs_rq_of(se);
> >  	struct rq *rq = rq_of(cfs_rq);
> >  
> > -	cpufreq_trigger_update(rq_clock(rq));
> > +	if (&rq->cfs == cfs_rq)
> > +		cpufreq_trigger_update(rq_clock(rq));
> >  }
> >  
> >  static inline void
> > -- 
> > 2.8.1
> >   

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] sched/fair: avoid !CONFIG_SMP cpufreq update callbacks when go idle Jisheng Zhang <jszhang@marvell.com> - 2016-06-27 10:10 +0200
  Re: [PATCH] sched/fair: avoid !CONFIG_SMP cpufreq update callbacks  when go idle Peter Zijlstra <peterz@infradead.org> - 2016-06-27 10:40 +0200
    Re: [PATCH] sched/fair: avoid !CONFIG_SMP cpufreq update callbacks  when go idle Jisheng Zhang <jszhang@marvell.com> - 2016-06-27 10:50 +0200

csiph-web