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Fri, 18 Sep 2026 02:41:10 -0700 (PDT) Date: Fri, 18 Sep 2026 11:41:09 +0200 From: Michal Hocko To: Shakeel Butt Cc: Tao Cui , 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 Subject: Re: [RFC PATCH 0/3] mm, memcg: isolate deprecated v1 state from struct mem_cgroup Message-ID: References: <20260916125737.1095414-1-cui.tao@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: ssbqfs3m51j1upy4b4i7ti1bhy7gfjtp X-Rspamd-Queue-Id: 0C2151C0007 X-HE-Tag: 1789724471-22652 X-HE-Meta: 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 RDKCOb5w o7HZC+60gYkI0l1P4Y3BlZlFCn6+WnDqZIGQ6SWwOpApBI/fAQEjLKJBV8yBfKOx2A0C98l7auuySth5uu7DEIM4veY5eYtADpO9szzHYxdWcIF4k19z/ZKnnWzRD0ocCh7E1HaOUraq8QHW3fCPGRKYtkyQFqnaG+mv2gpxFSXls/eVEFohlBVyjcV+hrx5At04rVhd4TTjXGkNKoHJRzyN7F2ECd4pWcfHetygd1s4VTOVXqnmAAmY44pKnl2c8EHGkhJLmON/7KAPkk1Qmz6lBAsE9P7EAUEEXpZRIxm3Ji3YI1Nzk4i9wEVJlpZV5VvXMIE6HXuxjXp22Hh9GJxV5AW41tCcUpLRzqGDS6gCk2PDhjRxTLtLT+lQER+Blr0WmcZMsR2TNAIpEptgxWuOp6Vt5VuYWG5iOOm7xG+rKyBRdwwZjPb0VjQoucOsKVb2F Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > > > > 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