On Tue, 9 Feb 2021 at 14:09, Valentin Schneider <valentin.schnei...@arm.com> wrote: > > On 05/02/21 12:48, Vincent Guittot wrote: > > @@ -10517,16 +10499,11 @@ static void nohz_newidle_balance(struct rq > > *this_rq) > > time_before(jiffies, READ_ONCE(nohz.next_blocked))) > > return; > > > > I was wondering whether all the conditions above were still relevant. I > think they are, but this one: > > /* Will wake up very soon. No time for doing anything else*/ > if (this_rq->avg_idle < sysctl_sched_migration_cost) > return; > > should have its comment updated to something like: > > /* > * Will wake up very soon. Blocked load will be updated > * periodically, no need to wake an idle CPU. > */ > > given kick_ilb() isn't the costliest of things. > > > - raw_spin_unlock(&this_rq->lock); > > /* > > - * This CPU is going to be idle and blocked load of idle CPUs > > - * need to be updated. Run the ilb locally as it is a good > > - * candidate for ilb instead of waking up another idle CPU. > > - * Kick an normal ilb if we failed to do the update. > > + * Blocked load of idle CPUs need to be updated. > > + * Kick an ILB to update statistics. > > */ > > - if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE)) > > - kick_ilb(NOHZ_STATS_KICK); > > - raw_spin_lock(&this_rq->lock); > > With this change, the return value of _nohz_idle_balance() is no longer > used. This means we could get rid of the tracking of whether it iterated > over all nohz CPUs or not.
Yeah, the return is useless now > > > + kick_ilb(NOHZ_STATS_KICK); > > } > > > > #else /* !CONFIG_NO_HZ_COMMON */
