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    SubjectRe: [PATCH V4 1/3] sched: cpufreq: Allow remote cpufreq callbacks
    Date
    On Wednesday, July 26, 2017 02:52:32 PM Viresh Kumar wrote:
    > We do not call cpufreq callbacks from scheduler core for remote
    > (non-local) CPUs currently. But there are cases where such remote
    > callbacks are useful, specially in the case of shared cpufreq policies.
    >
    > This patch updates the scheduler core to call the cpufreq callbacks for
    > remote CPUs as well.
    >
    > For now, all the registered utilization update callbacks are updated to
    > return early if remote callback is detected. That is, this patch just
    > moves the decision making down in the hierarchy.
    >
    > Later patches would enable remote callbacks for shared policies.
    >
    > Based on initial work from Steve Muckle.
    >
    > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
    > ---
    > drivers/cpufreq/cpufreq_governor.c | 4 ++++
    > drivers/cpufreq/intel_pstate.c | 8 ++++++++
    > include/linux/sched/cpufreq.h | 1 +
    > kernel/sched/cpufreq.c | 1 +
    > kernel/sched/cpufreq_schedutil.c | 11 ++++++++---
    > kernel/sched/deadline.c | 2 +-
    > kernel/sched/fair.c | 8 +++++---
    > kernel/sched/rt.c | 2 +-
    > kernel/sched/sched.h | 10 ++--------
    > 9 files changed, 31 insertions(+), 16 deletions(-)
    >
    > diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
    > index eed069ecfd5e..5499796cf9a8 100644
    > --- a/drivers/cpufreq/cpufreq_governor.c
    > +++ b/drivers/cpufreq/cpufreq_governor.c
    > @@ -272,6 +272,10 @@ static void dbs_update_util_handler(struct update_util_data *data, u64 time,
    > struct policy_dbs_info *policy_dbs = cdbs->policy_dbs;
    > u64 delta_ns, lst;
    >
    > + /* Don't allow remote callbacks */
    > + if (smp_processor_id() != data->cpu)
    > + return;
    > +
    > /*
    > * The work may not be allowed to be queued up right now.
    > * Possible reasons:
    > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
    > index 89bbc0c11b22..0dd14c8edd2d 100644
    > --- a/drivers/cpufreq/intel_pstate.c
    > +++ b/drivers/cpufreq/intel_pstate.c
    > @@ -1747,6 +1747,10 @@ static void intel_pstate_update_util_pid(struct update_util_data *data,
    > struct cpudata *cpu = container_of(data, struct cpudata, update_util);
    > u64 delta_ns = time - cpu->sample.time;
    >
    > + /* Don't allow remote callbacks */
    > + if (smp_processor_id() != data->cpu)
    > + return;

    You can do this check against cpu->cpu, however.

    > +
    > if ((s64)delta_ns < pid_params.sample_rate_ns)
    > return;
    >
    > @@ -1764,6 +1768,10 @@ static void intel_pstate_update_util(struct update_util_data *data, u64 time,
    > struct cpudata *cpu = container_of(data, struct cpudata, update_util);
    > u64 delta_ns;
    >
    > + /* Don't allow remote callbacks */
    > + if (smp_processor_id() != data->cpu)
    > + return;

    And same here.

    > +
    > if (flags & SCHED_CPUFREQ_IOWAIT) {
    > cpu->iowait_boost = int_tofp(1);
    > } else if (cpu->iowait_boost) {
    > diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h
    > index d2be2ccbb372..8256a8f35f22 100644
    > --- a/include/linux/sched/cpufreq.h
    > +++ b/include/linux/sched/cpufreq.h
    > @@ -16,6 +16,7 @@
    > #ifdef CONFIG_CPU_FREQ
    > struct update_util_data {
    > void (*func)(struct update_util_data *data, u64 time, unsigned int flags);
    > + unsigned int cpu;

    So it looks like you don't need this.

    schedutil doesn't need it as per patch [2/3].

    ondemand/conservative don't need it as per patch [3/3]

    intel_pstate doesn't need this too, because of the above.

    Thanks,
    Rafael

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