Re: [PATCH] sched_ext: Provides a sysfs 'events' to expose core event counters

From: Changwoo Min
Date: Fri Feb 14 2025 - 02:07:55 EST


Hello Tejun,


Thank you for the review!

On 25. 2. 14. 01:45, Tejun Heo wrote:
Hello, sorry about the late reply.

On Tue, Feb 11, 2025 at 09:57:08AM +0900, Changwoo Min wrote:
This probably should belong to the root/ subdir as we'd probably want to
keep the event counter separate per scheduler instance in the
multi-scheduler future.

I feel this is a bit contradictory to the need to access the core
event counters even after an scx scheduler is unloaded. In the
current implementation, root/ subdir appears and disappears when
an scx scheduler is loaded and unloaded.

We may change the scx_ktype to something similar to
scx_global_attr_group in order to keep root/ subdir. We then show
an empty file for root/ops when no scx scheduler is loaded while
keep the root/events file intact. I am not sure if this is what
we want.

What do you think?

Hmm... I don't think we can keep the directory for counters of schedulers
that have been unloaded. Looks like the right thing to do is giving up on
the idea of being able to access the counters after the scheduler is
unloaded. The counters are dumped on error exits, so hopefully this isn't
too big a loss. What do you think?

Yes, dumping the event counters is a part of scx_dump_state().
I agree. That's a reasonable choice. I will move 'events' under
the root/ subdir and send out a new version.

Regards,
Changwoo Min