Re: [PATCH v1 net-next 13/13] net-memcg: Allow decoupling memcg from global protocol memory accounting.

[Kuniyuki Iwashima <kuniyu@google.com>]

On Thu, Jul 24, 2025 at 6:49 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Wed, 23 Jul 2025 11:06:14 -0700 Kuniyuki Iwashima wrote:
> > > 3. Will there ever be a reasonable use-case where there is non-isolated
> > >    sub-tree under an isolated ancestor?
> >
> > I think no, but again, we need to think about the scenario above,
> > otherwise, your ideal semantics is just broken.
> >
> > Also, "no reasonable scenario" does not always mean "we must
> > prevent the scenario".
> >
> > If there's nothing harmful, we can just let it be, especially if such
> > restriction gives nothing andrather hurts performance with no
> > good reason.
>
> Stating the obvious perhaps but it's probably too late in the release
> cycle to get enough agreement here to merge the series. So I'll mark
> it as Deferred.

Fair enough.

>
> While I'm typing, TBH I'm not sure I'm following the arguments about
> making the property hierarchical. Since the memory limit gets inherited
> I don't understand why the property of being isolated would not.
> Either I don't understand the memcg enough, or I don't understand your
> intended semantics. Anyway..

Inheriting a config is easy, but keeping the hierarchy complete isn't,
or maybe I'm thinking too hard :S

[root@fedora ~]# mkdir /sys/fs/cgroup/test1
[root@fedora ~]# mkdir /sys/fs/cgroup/test1/test2
[root@fedora ~]# echo +memory > /sys/fs/cgroup/test1/cgroup.subtree_control
[root@fedora ~]# echo 10000 > /sys/fs/cgroup/test1/test2/memory.max
[root@fedora ~]# echo 1000 > /sys/fs/cgroup/test1/memory.max
[  108.130895] bash invoked oom-killer: gfp_mask=0xcc0(GFP_KERNEL),
order=0, oom_score_adj=0
...
[  108.260164] Out of memory and no killable processes...
[root@fedora ~]# cat /sys/fs/cgroup/test1/test2/memory.max
8192
[root@fedora ~]# cat /sys/fs/cgroup/test1/memory.max
0