11.06.2014, 17:15, "Srikar Dronamraju" <[email protected]>: >>> * Kirill Tkhai <[email protected]> [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.
Hm, I tested that on fair class tasks. They used to disappear from /proc/sched_debug and used to hang. I'll check all once again. I'm agree with you, if set_rq_offline() already presents, we should use it. /me went to clarify why it does not work in my test. >>>> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
