Hi Phil,
On Thu, Jan 16, 2025 at 08:53:15AM -0500, Phil Auld wrote:
> This is actually part of the problem. It's very hard to see this
> from userspace. I can show a shell session that shows that autogroup
> is disabled and that my task has an autogroup in /proc but determining
> that the autogroup is not being used not so much. (I may be missing
> something obvious but I could not find it).
>
> I had to look at the kernel code:
>
> kernel/sched/autogroup.h:
> static inline struct task_group *
> autogroup_task_group(struct task_struct *p, struct task_group *tg)
> {
> extern unsigned int sysctl_sched_autogroup_enabled;
> int enabled = READ_ONCE(sysctl_sched_autogroup_enabled);
>
> if (enabled && task_wants_autogroup(p, tg))
> return p->signal->autogroup->tg;
>
> return tg;
> }
>
> bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
> {
> if (tg != &root_task_group)
> return false;
> ...
>
> }
>
> The former being called from sched_group_fork() and sched_get_task_group().
>
> I suppose looking at /proc/pid/cgroup and seeing it report not "0::/"
> is part of it since it then won't be in root task group.
>
> To some extent any systemd based system these days is not really
> using autogroup at all anyway.
>
> I can put some of the above in there or just something like:
>
> # cat /proc/sys/kernel/sched_autogroup_enabled
> 0
> # cat /proc/$$/autogroup
> /autogroup-112 nice 0
>
>
> Thoughts?
Both. :)
The more information we have in the commit message, the better (in case
someone needs to check in the future, that will give more context).
Cheers,
Alex
--
<https://www.alejandro-colomar.es/>
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