Re: A path forward to cleaning up dying cgroups?

[Muchun Song <muchun.song@linux.dev>]

> On Feb 6, 2025, at 02:46, Shakeel Butt <shakeel.butt@linux.dev> wrote:
> 
> On Wed, Feb 05, 2025 at 01:08:42PM -0500, Johannes Weiner wrote:
>> On Wed, Feb 05, 2025 at 12:50:19PM -0500, Hamza Mahfooz wrote:
>>> Cc: Shakeel Butt <shakeel.butt@linux.dev>
>>> 
>>> On 2/5/25 12:48, Hamza Mahfooz wrote:
>>>> I was just curious as to what the status of the issue described in [1]
>>>> is. It appears that the last time someone took a stab at it was in [2].
>> 
>> If memory serves, the sticking point was whether pages should indeed
>> be reparented on cgroup death, or whether they could be moved
>> arbitrarily to other cgroups that are still using them.
>> 
>> It's a bit unfortunate, because the reparenting patches were tested
>> and reviewed, and the arbitrary recharging was just an idea that
>> ttbomk nobody seriously followed up on afterwards.
>> 
>> We also recently removed the charge moving code from cgroup1, along
>> with the subtle page access/locking/accounting rules it imposed on the
>> rest of the MM. I'm doubtful there is much appetite in either camp for
>> bringing this back.
>> 
>> So I would still love to see Muchun's patches merged. They fix a
>> seemingly universally experienced operational issue in memcg, and we
>> shouldn't hold it up unless somebody actually posts alternative code.
>> 
>> Thoughts?
> 
> I think the recharging (or whatever the alternative) can be a followup
> to this. I agree this is a good change.

I agree with you. We've been encountering dying memory issues for years
on our servers. As Roman said, I need to refresh my patches. So I need
some time for refreshing.

Muchun,
Thanks.