lkml.org 
[lkml]   [2017]   [Nov]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 6/6] cpufreq: schedutil: ignore sugov kthreads
On 30-Nov 14:41, Juri Lelli wrote:
> Hi,
>
> On 30/11/17 11:47, Patrick Bellasi wrote:
> > In system where multiple CPUs shares the same frequency domain a small
> > workload on a CPU can still be subject to frequency spikes, generated by
> > the activation of the sugov's kthread.
> >
> > Since the sugov kthread is a special RT task, which goal is just that to
> > activate a frequency transition, it does not make sense for it to bias
> > the schedutil's frequency selection policy.
> >
> > This patch exploits the information related to the current task to silently
> > ignore cpufreq_update_this_cpu() calls, coming from the RT scheduler, while
> > the sugov kthread is running.
> >
> > Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
> > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > Cc: Viresh Kumar <viresh.kumar@linaro.org>
> > Cc: linux-kernel@vger.kernel.org
> > Cc: linux-pm@vger.kernel.org
> >
> > ---
> > Changes from v2:
> > - rebased on v4.15-rc1
> > - moved at the end of the stack since considered more controversial
> > Changes from v1:
> > - move check before policy spinlock (JuriL)
> >
> > Change-Id: I4d749458229b6496dd24a8c357be42cd35a739fd
> > ---
> > kernel/sched/cpufreq_schedutil.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 3eea8884e61b..a93ad5b0c40d 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -270,6 +270,10 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
> > bool rt_mode;
> > bool busy;
> >
> > + /* Skip updates generated by sugov kthreads */
> > + if (unlikely(current == sg_policy->thread))
> > + return;
> > +
> > sugov_set_iowait_boost(sg_cpu, time, flags);
> > sg_cpu->last_update = time;
> >
> > @@ -356,6 +360,10 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> > unsigned int next_f;
> > bool rt_mode;
> >
> > + /* Skip updates generated by sugov kthreads */
> > + if (unlikely(current == sg_policy->thread))
> > + return;
> > +
> > raw_spin_lock(&sg_policy->update_lock);
> >
> > sugov_get_util(&util, &max, sg_cpu->cpu);
>
> If the DL changes (which I shall post again as soon as tip/sched/core is
> bumped up to 4.15-rc1) get in first, this is going to be useless (as the
> DL kthread gets ignored by the scheduling class itself). But, this looks
> good to me "in the meantime".

Just to better understand, you mean that the DL kthread does not send
out schedutil updates?

If that's the case I agree we can discard this patch... that's also
one of the reasons why I move it at the end of this series.

> Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
>
> Best,
>
> Juri

--
#include <best/regards.h>

Patrick Bellasi

\
 
 \ /
  Last update: 2017-11-30 17:03    [W:0.079 / U:9.352 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site