Messages in this thread | | | Date | Wed, 11 Jun 2014 18:45:36 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH 1/2] sched: Rework migrate_tasks() |
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> > * Kirill Tkhai <ktkhai@parallels.com> [2014-06-11 13:52:10]: > >> Currently migrate_tasks() skips throttled tasks, > >> because they are not pickable by pick_next_task(). > > > > Before migrate_tasks() is called, we do call set_rq_offline(), in > > migration_call(). > > > > Shouldnt this take care of unthrottling the tasks and making sure that > > they can be picked by pick_next_task(). > > If we do this separate for every class, we'll have to do this 3 times. > Furthermore, deadline class does not have a list of throttled tasks. > So we'll have to the same as I did: to lock tasklist_lock and to iterate > throw all of the tasks in the system just to found deadline tasks. >
I think you misread my comment.
Currently migrate_task() gets called from migration_call() and in the migration_call() before migrate_tasks(), set_rq_offline() should put tasks back using unthrottle_cfs_rq().
So my question is: Why are these tasks not getting unthrottled through we are calling set_rq_offline? To me set_rq_offline is calling the actual sched class routines to do the needful.
I can understand about deadline tasks, because we don't have a deadline But thats the only tasks that we need to fix.
> >> These tasks stay on dead cpu even after they > >> becomes unthrottled. They are not schedulable > >> till user manually changes their affinity or till > >> cpu becomes alive again. > > > > If we are still seeing tasks not being picked by pick_next_task(), then > > can it probably mean that rq->rd was NULL? > > Unthrottle functions dl_task_timer() and unthrottle_cfs_rq() put tasks and > queues back. They do not look at rq->rd.
What I meant was only if rq->rd isn't set, then we don't call set_rq_offline, which seems very reasonable. -- Thanks and Regards Srikar Dronamraju
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