On Mon, 4 May 2020 at 03:57, Hillf Danton <hdan...@sina.com> wrote: > > > The comment says, if there is an imbalance between LLC domains (IOW we > could increase the overall cache use), we need some less-loaded LLC > domain to pull some load. > > To show that imbalance, record busy CPUs as they come and go by doing > a minor cleanup for sd::nohz_idle.
Your comment failed to explain why we can get rid of sd->nohz_idle > > Cc: Mel Gorman <mgor...@techsingularity.net> > Cc: Vincent Guittot <vincent.guit...@linaro.org> > Cc: Valentin Schneider <valentin.schnei...@arm.com> > Cc: Dietmar Eggemann <dietmar.eggem...@arm.com> > Signed-off-by: Hillf Danton <hdan...@sina.com> > --- > > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -10138,13 +10138,8 @@ static void set_cpu_sd_state_busy(int cp > > rcu_read_lock(); > sd = rcu_dereference(per_cpu(sd_llc, cpu)); > - > - if (!sd || !sd->nohz_idle) > - goto unlock; > - sd->nohz_idle = 0; you remove the use of sd->nohz_idle but you don't remove it from struct sched_domain > - > - atomic_inc(&sd->shared->nr_busy_cpus); > -unlock: > + if (sd) > + atomic_inc(&sd->shared->nr_busy_cpus); > rcu_read_unlock(); > } > > @@ -10168,13 +10163,8 @@ static void set_cpu_sd_state_idle(int cp > > rcu_read_lock(); > sd = rcu_dereference(per_cpu(sd_llc, cpu)); > - > - if (!sd || sd->nohz_idle) > - goto unlock; > - sd->nohz_idle = 1; > - > - atomic_dec(&sd->shared->nr_busy_cpus); > -unlock: > + if (sd) > + atomic_dec(&sd->shared->nr_busy_cpus); > rcu_read_unlock(); > } > >
