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SubjectRe: [PATCH v3 1/2] sched/cpufreq: always consider blocked FAIR utilization
On 27-May 11:50, Rafael J. Wysocki wrote:
> On Thu, May 24, 2018 at 4:10 PM, Patrick Bellasi
> <patrick.bellasi@arm.com> wrote:
> > Since the refactoring introduced by:
> >
> > commit 8f111bc357aa ("cpufreq/schedutil: Rewrite CPUFREQ_RT support")
> >
> > we aggregate FAIR utilization only if this class has runnable tasks.
> > This was mainly due to avoid the risk to stay on an high frequency just
> > because of the blocked utilization of a CPU not being properly decayed
> > while the CPU was idle.
> >
> > However, since:
> >
> > commit 31e77c93e432 ("sched/fair: Update blocked load when newly idle")
> >
> > the FAIR blocked utilization is properly decayed also for IDLE CPUs.
> >
> > This allows us to use the FAIR blocked utilization as a safe mechanism
> > to gracefully reduce the frequency only if no FAIR tasks show up on a
> > CPU for a reasonable period of time.
> >
> > Moreover, we also reduce the frequency drops of CPUs running periodic
> > tasks which, depending on the task periodicity and the time required
> > for a frequency switch, was increasing the chances to introduce some
> > undesirable performance variations.
> >
> > Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
> > Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> > Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
> > Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > Cc: Vincent Guittot <vincent.guittot@linaro.org>
> > Cc: Viresh Kumar <viresh.kumar@linaro.org>
> > Cc: Joel Fernandes <joelaf@google.com>
> > Cc: linux-kernel@vger.kernel.org
> > Cc: linux-pm@vger.kernel.org
>
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Or please let me know if you want me to apply this one.

Hi Rafael, seems this patch has already been applied in tip/sched/core.
However is missing your tag above. :/

Dunno if I have / I can to do something about that.

> > ---
> > Changes in v3:
> > - add "Tested-by" and "Acked-by" Vincent tags
> >
> > Changes in v2:
> > - add "Acked-by" Viresh tag
> > ---
> > kernel/sched/cpufreq_schedutil.c | 17 ++++++++---------
> > 1 file changed, 8 insertions(+), 9 deletions(-)
> >
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index e13df951aca7..28592b62b1d5 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -183,22 +183,21 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu)
> > static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
> > {
> > struct rq *rq = cpu_rq(sg_cpu->cpu);
> > - unsigned long util;
> >
> > - if (rq->rt.rt_nr_running) {
> > - util = sg_cpu->max;
> > - } else {
> > - util = sg_cpu->util_dl;
> > - if (rq->cfs.h_nr_running)
> > - util += sg_cpu->util_cfs;
> > - }
> > + if (rq->rt.rt_nr_running)
> > + return sg_cpu->max;
> >
> > /*
> > + * Utilization required by DEADLINE must always be granted while, for
> > + * FAIR, we use blocked utilization of IDLE CPUs as a mechanism to
> > + * gracefully reduce the frequency when no tasks show up for longer
> > + * periods of time.
> > + *
> > * Ideally we would like to set util_dl as min/guaranteed freq and
> > * util_cfs + util_dl as requested freq. However, cpufreq is not yet
> > * ready for such an interface. So, we only do the latter for now.
> > */
> > - return min(util, sg_cpu->max);
> > + return min(sg_cpu->max, (sg_cpu->util_dl + sg_cpu->util_cfs));
> > }
> >
> > static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time, unsigned int flags)
> > --
> > 2.15.1
> >

--
#include <best/regards.h>

Patrick Bellasi

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