On Fri, Sep 11, 2020 at 01:17:45PM +0100, Valentin Schneider wrote: > > @@ -6968,6 +7064,8 @@ int sched_cpu_deactivate(unsigned int cp > > */ > > synchronize_rcu(); > > > > + balance_push_set(cpu, true); > > + > > IIUC this is going to make every subsequent finish_lock_switch() > migrate the switched-to task if it isn't a pcpu kthread. So this is going > to lead to a dance of > > switch_to(<task0>) -> switch_to(<stopper>) -> switch_to(<task1>) -> > switch_to(<stopper>) ... > > Wouldn't it be better to batch all those in a migrate_tasks() sibling that > skips pcpu kthreads?
That's 'difficult', this is hotplug, performance is not a consideration. Basically we don't have an iterator for the runqueues, so finding these tasks is hard.
