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(e.g. idle load balancing)? > > I still can't see the reason why this code should be changed (was asked > in v4 already). I noticed that the rq->idle_stamp is not zero when rq->idle_stamp is set in begining of sched_balance_newidle(). It is a strange behavior. then I found a new task(clone/fork, etc) may be move to this rq while this rq->idle_stamp is still not zero. it triggers the second newidle on this CPU. > > Do you have a workload on your machine which gives you better scores in > case you set 'rq->idle_stamp = 0' in all those cases? I tested the specjbb, the performance does not change. Btw, the "rq->idle_stamp = 0" is redandent, we can remove it in patch 1. > What is is actual issue in the current code? the current code is confusing to me :) Current  rq->idle_stamp is equal to rq->wakeup_idle_stamp. > > Does 'this_rq->avg_idle' get too big so you spend too much useless time > (since pulled_task == 0) in sched_balance_newidle() because the bailout > condition: > > sched_balance_newidle() > > ... > if (!get_rd_overloaded(this_rq->rd) || > this_rq->avg_idle < sd->max_newidle_lb_cost) { > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > ... > goto out; > > doesn't trigger anymore? Not this issue. Thanks Huang Shijie > > [...]