linux-kernel - Re: [PATCH 2/3] mm/lru_gen: add configuration option to select debugfs/procfs for lru

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Message-ID: <CAJj2-QFM3iwO==3JKQ4nnHfAxYJuyYXZ6uNJUR8rQdf_Q_1x0A@mail.gmail.com>
Date: Mon, 1 Dec 2025 15:35:05 -0600
From: Yuanchu Xie <yuanchu@...gle.com>
To: Zicheng Wang <wangzicheng@...or.com>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, david@...hat.com, 
	axelrasmussen@...gle.com, mhocko@...nel.org, zhengqi.arch@...edance.com, 
	shakeel.butt@...ux.dev, lorenzo.stoakes@...cle.com, weixugc@...gle.com, 
	Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com, 
	mhocko@...e.com, corbet@....net, linux-mm@...ck.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm/lru_gen: add configuration option to select
 debugfs/procfs for lru_gen

On Thu, Nov 27, 2025 at 8:54 PM Zicheng Wang <wangzicheng@...or.com> wrote:
>
> Signed-off-by: Zicheng Wang <wangzicheng@...or.com>
> ---
>  mm/Kconfig | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index e443fe8cd..be7efa794 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1325,6 +1325,16 @@ config LRU_GEN_STATS
>  config LRU_GEN_WALKS_MMU
>         def_bool y
>         depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
> +
> +config LRU_GEN_PROCFS_CTRL
> +       bool "Move lru_gen files from debugfs to procfs"
> +       depends on LRU_GEN && PROC_FS
> +       help
> +         Move lru_gen management from debugfs to procfs (/proc/lru_gen).
> +         This production-ready feature provides critical memory reclaim
> +         prediction and control. It is no longer experimental.
> +         The migration ensures availability in commercial products where
> +         debugfs may be disabled.
Hi Zicheng,

A config option determining where LRU_gen files reside creates a
fragile procfs interface. Consider adding a similar interface with
less implementation detail to /sys/kernel/mm/lru_gen/ if the goal is
to stabilize the debugfs APIs.

If the goal is to proactively age lruvecs that have been at
MIN_NR_GENS for some time/events/etc, is it possible to integrate this
into the kernel and avoid leaking MGLRU implementation details into
userspace?

Thanks,
Yuanchu