Re: [PATCH 1/3] sched: Add new API wake_up_if_idle() to wake up the idle cpu

[Daniel Lezcano]

On 08/21/2014 04:12 AM, Liu, Chuansheng wrote:
> Hello Daniel,
>
> > -----Original Message-----
> > From: Daniel Lezcano [mailto:daniel.lezcano@xxxxxxxxxx]
> > Sent: Thursday, August 21, 2014 9:54 AM
> > To: Liu, Chuansheng; luto@xxxxxxxxxxxxxx; peterz@xxxxxxxxxxxxx;
> > rjw@xxxxxxxxxxxxx; mingo@xxxxxxxxxx
> > Cc: linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Liu, Changcheng;
> > Wang, Xiaoming; Chakravarty, Souvik K
> > Subject: Re: [PATCH 1/3] sched: Add new API wake_up_if_idle() to wake up the
> > idle cpu
> >
> > On 08/18/2014 10:37 AM, Chuansheng Liu wrote:
> > > Implementing one new API wake_up_if_idle(), which is used to
> > > wake up the idle CPU.
> >
> > Is this patchset tested ? Did you check it solves the issue you were
> > facing ?
> We have done the basic test, and found the cores can exit C0 quickly with this patchset.
> Basically once the _TIF_NEED_RESCHED is set, then the poll_idle() can be broken.
>
> Please correct me if something is wrong, thanks.

Actually, it was not clear for me if this patch was a proposal or not.

I will review it.

Thanks

  -- Daniel

> > > Suggested-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> > > Signed-off-by: Chuansheng Liu <chuansheng.liu@xxxxxxxxx>
> > > ---
> > >    include/linux/sched.h |    1 +
> > >    kernel/sched/core.c   |   16 ++++++++++++++++
> > >    2 files changed, 17 insertions(+)
> > >
> > > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > > index 857ba40..3f89ac1 100644
> > > --- a/include/linux/sched.h
> > > +++ b/include/linux/sched.h
> > > @@ -1024,6 +1024,7 @@ struct sched_domain_topology_level {
> > >    extern struct sched_domain_topology_level *sched_domain_topology;
> > >
> > >    extern void set_sched_topology(struct sched_domain_topology_level *tl);
> > > +extern void wake_up_if_idle(int cpu);
> > >
> > >    #ifdef CONFIG_SCHED_DEBUG
> > >    # define SD_INIT_NAME(type)		.name = #type
> > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > > index 1211575..adf104f 100644
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > @@ -1620,6 +1620,22 @@ static void ttwu_queue_remote(struct
> > task_struct *p, int cpu)
> > >    	}
> > >    }
> > >
> > > +void wake_up_if_idle(int cpu)
> > > +{
> > > +	struct rq *rq = cpu_rq(cpu);
> > > +	unsigned long flags;
> > > +
> > > +	if (set_nr_if_polling(rq->idle)) {
> > > +		trace_sched_wake_idle_without_ipi(cpu);
> > > +	} else {
> > > +		raw_spin_lock_irqsave(&rq->lock, flags);
> > > +		if (rq->curr == rq->idle)
> > > +			smp_send_reschedule(cpu);
> > > +		/* Else cpu is not in idle, do nothing here */
> > > +		raw_spin_unlock_irqrestore(&rq->lock, flags);
> > > +	}
> > > +}
> > > +
> > >    bool cpus_share_cache(int this_cpu, int that_cpu)
> > >    {
> > >    	return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
> >
> >
> > --
> >    <http://www.linaro.org/> Linaro.org â Open source software for ARM
> > SoCs
> >
> > Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
> > <http://twitter.com/#!/linaroorg> Twitter |
> > <http://www.linaro.org/linaro-blog/> Blog


--
 <http://www.linaro.org/> Linaro.org â Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/