Hi Vincent, On Thu, May 26, 2016 at 01:50:56PM +0200, Vincent Guittot wrote: > On 26 May 2016 at 03:14, Yuyang Du <yuyang...@intel.com> wrote: > > Vincent reported that the first task to a new task group's cfs_rq will > > be attached in attach_task_cfs_rq() and once more when it is enqueued > > (see https://lkml.org/lkml/2016/5/25/388). > > > > Actually, it is worse, attach_task_cfs_rq() is called for new task even > > way before init_entity_runnable_average(). > > > > Solve this by avoiding attach as well as detach new task's sched avgs > > in task_move_group_fair(). To do it, we need to know whether the task > > is forked or not, so we pass this info all the way from sched_move_task() > > to attach_task_cfs_rq(). > > Not sure that this is the right way to solve this problem because you > continue to attach the task twice without detaching it in the mean > time: > - once during the copy of the process in cpu_cgroup_fork (you skip the > attach of load average but the task is still attached to the local > cpu)
Sorry, the task's what is still attached, and how? You mean the vruntime thingy? But the load/util avgs are not. > In the mean time, sched_entity is initialized and the last_update_time is > reset last_update_time is set to 0 in initialization, and this is the first time it is touched, no? > - one more time when the task is enqueued because the last_update_time > has been reset (this time you don't skip the attache of load_avg This is expected/wanted. We don't skip this because this will be the first-time attach. > Should you better detach the sched_entity with a copy of its parent > metrics before initializing it and attaching it to the new cpu ? Thanks, Yuyang
