linux-kernel - Re: [RFC PATCH 0/3] mm/lru_gen: add memory.lru

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Message-ID: <aXFPhnOn4oGllq_Q@linux.dev>
Date: Wed, 21 Jan 2026 14:19:44 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>
Cc: linux-mm@...ck.org, Tejun Heo <tj@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Koutný <mkoutny@...e.com>, 
	Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>, 
	David Hildenbrand <david@...nel.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, 
	Michal Hocko <mhocko@...e.com>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Muchun Song <muchun.song@...ux.dev>, Qi Zheng <zhengqi.arch@...edance.com>, cgroups@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] mm/lru_gen: add memory.lru_gen interface for
 cgroup v2

On Wed, Jan 21, 2026 at 08:39:46PM +0800, Jiayuan Chen wrote:
> This patchset adds a memory.lru_gen interface to cgroup v2, allowing users
> to interact with MGLRU directly on a specific cgroup without needing to
> know the internal memcg_id.

Unfortunetely we don't want to expose reclaim implementation specific
interface to a cgroup. 

> 
> Motivation
> ==========
> Currently, the only way to perform aging or eviction on a specific memcg
> is through the debugfs interface (/sys/kernel/debug/lru_gen), which
> requires the memcg_id. However, there's no straightforward way to get the
> memcg_id for a given cgroup path. This makes it difficult for users to
> leverage MGLRU's proactive reclaim capabilities on specific cgroups.

>From the next kernel version, this memcg_id will be inode number of the
cgroup for this interface. So, a simple 'ls -id cgroup_path' would  be
sufficient for your use-case.

The relevant series [1] is in mm-tree at the moment and if you want, you
can backport it to your kernels.

[1] https://lkml.kernel.org/r/20251225232116.294540-1-shakeel.butt@linux.dev