On 1 February 2018 at 19:10, Peter Zijlstra <pet...@infradead.org> wrote: > On Wed, Jan 24, 2018 at 09:25:36AM +0100, Vincent Guittot wrote: >> @@ -8861,7 +8875,14 @@ static int idle_balance(struct rq *this_rq, struct >> rq_flags *rf) >> update_next_balance(sd, &next_balance); >> rcu_read_unlock(); >> >> - if (time_after(jiffies, next) && >> atomic_read(&nohz.stats_state)) >> + /* >> + * Update blocked idle load if it has not been done for a >> + * while. Try to do it locally before entering idle but kick a >> + * ilb if it takes too much time and might delay next local >> + * wake up >> + */ >> + if (time_after(jiffies, next) && >> atomic_read(&nohz.stats_state) && >> + !_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, >> CPU_NEWLY_IDLE)) >> kick_ilb(NOHZ_STATS_KICK); >> >> goto out; > > This I really dislike. We're here because avg_idle is _really_ low, we > really should not then call _nohz_idle_balance().
Yes. In fact I was targeting the case were (this_rq->avg_idle >= sysctl_sched_migration_cost) and the system is not overloaded
