On Wed, Feb 17, 2021 at 03:52:59PM -0500, Johannes Weiner [off-list ref] wrote:

It's possible, but I don't think worth the trouble.

You're right. I gave it a deeper look and what would be saved on data,
would be paid in code complexity.

In this case, we're talking about a relatively small data structure
and the overhead is per mountpoint.

IIUC, it is per each mountpoint's number of cgroups. But I still accept
the argument above. Furthermore, this can be changed later.

The default root group has statically preallocated percpu data before
and after this patch. See cgroup.c:

I stand corrected, the comment is still valid.

Therefore,
Reviewed-by: Michal Koutný <mkoutny@suse.com>