linux-kernel - Re: [PATCH v2 00/28] Eliminate Dying Memory Cgroup

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Message-ID: <aVJDuObeV2Y99em-@hyeyoo>
Date: Mon, 29 Dec 2025 18:35:22 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Qi Zheng <qi.zheng@...ux.dev>
Cc: Shakeel Butt <shakeel.butt@...ux.dev>, Yosry Ahmed <yosry.ahmed@...ux.dev>,
        hannes@...xchg.org, hughd@...gle.com, mhocko@...e.com,
        roman.gushchin@...ux.dev, muchun.song@...ux.dev, david@...nel.org,
        lorenzo.stoakes@...cle.com, ziy@...dia.com, imran.f.khan@...cle.com,
        kamalesh.babulal@...cle.com, axelrasmussen@...gle.com,
        yuanchu@...gle.com, weixugc@...gle.com, chenridong@...weicloud.com,
        mkoutny@...e.com, akpm@...ux-foundation.org,
        hamzamahfooz@...ux.microsoft.com, apais@...ux.microsoft.com,
        lance.yang@...ux.dev, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH v2 00/28] Eliminate Dying Memory Cgroup

On Mon, Dec 29, 2025 at 03:48:26PM +0800, Qi Zheng wrote:
> 
> 
> On 12/24/25 7:20 AM, Shakeel Butt wrote:
> > On Tue, Dec 23, 2025 at 08:04:50PM +0000, Yosry Ahmed wrote:
> > [...]
> > > 
> > > I think there might be a problem with non-hierarchical stats on cgroup
> > > v1, I brought it up previously [*]. I am not sure if this was addressed
> > > but I couldn't immediately find anything.
> > 
> > Sigh, the curse of memcg-v1. Let's see what we can do to not break v1.
> 
> The memcg-v1 was originally planned to be removed, could we skip
> supporting v1?

You mean not reparenting LRU pages if CONFIG_MEMCG_V1 is set?

That may work, but IMHO given that there is no clear timeline for removal
yet (some v1-specific features have been officially deprecated,
but memcg v1 as a whole hasn't), implementing Shakeel's suggestion [1]
may be a good option (it doesn't seem to add much complexity)

But it can be argued that it's not good enough reason to
delay the series; adding support for V1 later sounds sensible to me.

Anyway I'm fine either way and I'm not a memcg maintainer myself,
so this is just my two cents.

[1] https://lore.kernel.org/linux-mm/wvj4w7ifmrifnh5bvftdziudsj52fdnwlhbt2oifwmxmi4eore@ob3mrfahhnm5/

-- 
Cheers,
Harry / Hyeonggon