Re: [tip:sched/core] sched: Add 'autogroup' scheduling feature:automated per session task groups

[Bharata B Rao]

On Mon, Dec 20, 2010 at 6:49 PM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:
> On Mon, 2010-12-20 at 18:38 +0530, Bharata B Rao wrote:
>> The autogroup patchset removes the display of cgroup name from
>> sched_debug output.
>
> Hrmph.. that wasn't supposed to happen, care to send a patch to fix that
> up?

There are two aspects here:

- Printing cgroup name for per-CPU cfs_rqs shouldn't be affected by
  autogroup and the old code should work here.
- Printing cgroup name for tasks depends on task_group(), which has
been changed by autogroup patch. I haven't really looked deep into
autogroup patch, but from whatever I can gather, Mike had a reason
to remove this bit from sched_debug. The task groups created for
autogroups don't have cgroups associated with them and hence no
dentries and hence no pathnames.

I guess we could do fix this as shown in the attached patch.

>
>
>> Also, with tg_shares_up improvements, the leaf cfs_rqs are maintained
>> on rq->leaf_cfs_rq_list only if they carry any load. But the code to
>> display cfs_rq information for sched_debug isn't updated and hence
>> information from a few cfs_rqs are missing from sched_debug.
>
> Well, that's a _good_ thing, right?
>
> I mean, if we know they're empty, and don't contribute to schedule, why
> bother displaying them?

In addition to tasks, we do display other details pertaining to the cfs_rq.
I thought, having a complete view of all the cfs_rqs in the system would
be better and consistent than obtaining different cfs_rqs on different
captures of /proc/sched_debug.

Regards,
Bharata.
-- 
http://bharata.sulekha.com/blog/posts.htm, http://raobharata.wordpress.com/

Attachment: fix-sched-debug.patch
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