From: Michal Hocko <mhocko@suse.com>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Tao Cui <cui.tao@linux.dev>,
hannes@cmpxchg.org, roman.gushchin@linux.dev,
muchun.song@linux.dev, cgroups@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Tao Cui <cuitao@kylinos.cn>
Subject: Re: [RFC PATCH 0/3] mm, memcg: isolate deprecated v1 state from struct mem_cgroup
Date: Fri, 18 Sep 2026 11:41:09 +0200 [thread overview]
Message-ID: <aq0HNe5s3zvOnM_I@tiehlicka> (raw)
In-Reply-To: <aqxMk6yaiFHeeAAg@linux.dev>
On Thu 17-09-26 13:26:40, Shakeel Butt wrote:
> On Wed, Sep 16, 2026 at 08:57:34PM +0800, Tao Cui wrote:
> > From: Tao Cui <cuitao@kylinos.cn>
> >
> > The legacy cgroup v1 memory controller has already been moved out of
> > the shared implementation at the file level (mm/memcontrol-v1.c) and at
> > the Kconfig level (CONFIG_MEMCG_V1, default n since 6.11). Its
> > per-cgroup state, however, still sits as individual members inside
> > struct mem_cgroup, guarded by #ifdefs.
> >
> > This series isolates the deprecated implementation from the shared hot
> > structure: all v1-only members are grouped into a dedicated
> > struct mem_cgroup_v1, and every access goes through memcg->v1.X.
> >
> > With this in place the v1 implementation is self-contained: its
> > interface in mm/memcontrol-v1.c, its state in struct mem_cgroup_v1, and
> > its eventual removal becomes a localized deletion of this struct
> > together with mm/memcontrol-v1.c, instead of unwinding
> > ifdef-scattered members across the shared header.
>
> Sorry I don't see any benefit of this code churn. The code is already behind
> config. What exactly this code churn is giving us?
The only arguable upside is that this would make it ever so slightly
easier to track v1 specific stuff (once that s@v1@memcg1@ or similar).
I am not convinced this is sufficient to justify the churn either.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2026-09-18 9:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 12:57 Tao Cui
2026-09-16 12:57 ` [PATCH 1/3] mm, memcg: introduce struct mem_cgroup_v1 Tao Cui
2026-09-16 12:57 ` [PATCH 2/3] mm, memcg: move v1-only members into mem_cgroup_v1 Tao Cui
2026-09-16 12:57 ` [PATCH 3/3] docs: cgroup-v1: note the v1 memory controller implementation boundary Tao Cui
2026-09-17 20:26 ` [RFC PATCH 0/3] mm, memcg: isolate deprecated v1 state from struct mem_cgroup Shakeel Butt
2026-09-18 9:41 ` Michal Hocko [this message]
2026-09-18 10:22 ` Tao Cui
2026-09-18 16:24 ` Johannes Weiner
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