Messages in this thread | | | Date | Wed, 12 Jan 2011 09:07:09 +0530 | From | Bharata B Rao <> | Subject | Re: [patch] Re: autogroup: sched_setscheduler() fails |
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On Tue, Jan 11, 2011 at 07:48:06PM +0100, Mike Galbraith wrote: > On Tue, 2011-01-11 at 22:40 +0530, Bharata B Rao wrote: > > On Mon, Jan 10, 2011 at 05:42:26PM +0100, Mike Galbraith wrote: > > > Index: linux-2.6/kernel/sched_autogroup.c > > > =================================================================== > > > --- linux-2.6.orig/kernel/sched_autogroup.c > > > +++ linux-2.6/kernel/sched_autogroup.c > > > @@ -73,6 +73,15 @@ static inline struct autogroup *autogrou > > > ag->id = atomic_inc_return(&autogroup_seq_nr); > > > ag->tg = tg; > > > tg->autogroup = ag; > > > +#ifdef CONFIG_RT_GROUP_SCHED > > > + /* > > > + * HACK: autogroup RT tasks run in the root task group. > > > + * This fools __sched_setscheduler() into proceeding on > > > + * so we can move the task to the appropriate runqueue > > > + * upon scheduling policy change. > > > + */ > > > + tg->rt_bandwidth.rt_runtime = RUNTIME_INF; > > > +#endif > > > > > > return ag; > > > > > > @@ -143,6 +152,15 @@ autogroup_move_group(struct task_struct > > > autogroup_kref_put(prev); > > > } > > > > > > +static inline void > > > +autogroup_setscheduler(struct task_struct *p, int on_rq) > > > +{ > > > + if (p->sched_class->task_move_group) > > > + p->sched_class->task_move_group(p, on_rq); > > > + else > > > + set_task_rq(p, task_cpu(p)); > > > +} > > > + > > > > IIUC, with the above changes you are actually queing the task into > > rt_rq of an autogroup. But the task's autogroup interface > > (/proc/<pid>/autogroup) allows you to control the bandwidth of only > > cfs_rq tasks, while the rt tasks in the group get RUNTIME_INF bandwidth. > > > > I think what we need is a real group change here (which is difficult I > > think) and not just sched_class change. > > Unless I fscked up, set_task_rq() is the group change. As soon as the > task's class changes, it'll be moved to the root_task_group.
Ok, this is what I understand, may be Peter Z can confirm...
set_task_rq() just changes the task's cfs_rq and rt_rq as per its task_group(). The normal way to change a task's group is to first change its cgroup pointer (task->cgroups, see cgroup_attach_task()) After this you change the runqueues by calling set_task_rq() which now refers to new group's runqueues.
In your code, I don't see where you really change task's group. AFAICS, it continues to remain in the same autogroup.
Regards, Bharata.
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