On Mon, Sep 12, 2016 at 09:47:52AM +0200, Vincent Guittot wrote: > When a task switches to fair scheduling class, the period between now and > the last update of its utilization is accounted as running time whatever > happened during this period. This wrong accounting applies to the task > and also to the task group branch. > > When changing the property of a running task like its list of allowed CPUs > or its scheduling class, we follow the sequence: > -dequeue task > -put task > -change the property > -set task as current task > -enqueue task > > The end of the sequence doesn't follow the normal sequence which is : > -enqueue a task > -then set the task as current task. > > This wrong ordering is the root cause of wrong utilization accounting. > Update the sequence to follow the right one: > -dequeue task > -put task > -change the property > -enqueue task > -set task as current task
But enqueue_entity depends on cfs_rq->curr, which is set by set_curr_task_fair(). Also, the normalize comment in dequeue_entity() worries me, 'someone' didn't update that when he moved update_min_vruntime() around.
