Re: [RFC PATCH] sched: select_idle_sibling macro optimize

From: Mike Galbraith
Date: Thu Jan 16 2014 - 08:52:24 EST


On Thu, 2014-01-16 at 21:13 +0800, Alex Shi wrote:
> Add Mike Galbraith.
>
> Any one like to give some comments?
>
> On 01/15/2014 10:23 PM, Alex Shi wrote:
> > If the sd domain just has one group, then we must be caught the
> > i == target later, and then goes to deeper level domain.
> > So just skip this domain checking to save some instructions.
> >
> > Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxx>
> > ---
> > kernel/sched/fair.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index c7395d9..3265fbc 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4196,6 +4196,11 @@ static int select_idle_sibling(struct task_struct *p, int target)
> > sd = rcu_dereference(per_cpu(sd_llc, target));
> > for_each_lower_domain(sd) {
> > sg = sd->groups;
> > +
> > + /* skip single group domain */
> > + if (sg == sg->next)
> > + continue;

When is that gonna happen?

-Mike


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