linux-kernel - Re: A path forward to cleaning up dying cgroups?

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Message-ID: <5316c4b3-fae5-4525-a934-a56c45dade42@oracle.com>
Date: Thu, 6 Feb 2025 21:21:12 +0530
From: Kamalesh Babulal <kamalesh.babulal@...cle.com>
To: Muchun Song <muchun.song@...ux.dev>, Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Johannes Weiner <hannes@...xchg.org>,
        Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>, linux-mm@...ck.org,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Michal Koutný <mkoutny@...e.com>,
        Michal Hocko <mhocko@...nel.org>,
        Allen Pais <apais@...ux.microsoft.com>,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: Re: A path forward to cleaning up dying cgroups?



On 06/02/25 09:00, Muchun Song wrote:
> 
> 
>> On Feb 6, 2025, at 02:46, Shakeel Butt <shakeel.butt@...ux.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@...ux.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.
> 

We have seen the dying cgroups issue too and look forward to your patches.
Happy to help with testing/reviewing.

-- 
Thanks,
Kamalesh