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 <[email protected]> > > Reviewed-by: Dietmar Eggemann <[email protected]> > > Cc: Ingo Molnar <[email protected]> > > Cc: Peter Zijlstra <[email protected]> > > Cc: Rafael J. Wysocki <[email protected]> > > Cc: Viresh Kumar <[email protected]> > > Cc: [email protected] > > Cc: [email protected] > > > > --- > > 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 <[email protected]> > > Best, > > Juri -- #include <best/regards.h> Patrick Bellasi
