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Mon, 02 Nov 2026 11:16:06 -0800 (PST) Received: from localhost ([2605:8600:200:14e3:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67baf147246sm5737296d50.1.2026.11.02.11.15.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 11:16:00 -0800 (PST) Date: Mon, 2 Nov 2026 14:15:52 -0500 From: Johannes Weiner To: Roman Gushchin Cc: Tao Cui , Michal Hocko , Shakeel Butt , 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: <0BEF7489-16EC-44EE-847B-A6AA380BE11F@linux.dev> <32e80536-64e4-4ae3-a7da-4a37ed415f0a@linux.dev> <7ia41p9341lv.fsf@castle.c.googlers.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7ia41p9341lv.fsf@castle.c.googlers.com> On Mon, Nov 02, 2026 at 04:52:44PM +0000, Roman Gushchin wrote: > Tao Cui writes: > > > Hi Roman, > > > > 在 2026/10/30 14:05, Roman Gushchin 写道: > >> I believe we want to delete this code sooner than later, why would we rewrite it before that? > >> > > > > My assumption was that v1 would still be maintained for some time > > before its eventual removal, and the goal was to reduce the coupling > > between the remaining v1 code and the shared core structures during > > that period, rather than to rewrite the implementation for its own > > sake. > > I understand. But personally I don't see big issues with the current > code caused by the v1 stuff. Maybe I miss something... > > The proposed changes on the other hand create difficulties for those > who use v1 and maintain some local changes or simple backport upstream > fixes. Of course, it's not a reason to not change the upstream code if > it's justified, but in this case I'm hardly convinced. > > > If the expectation is that the remaining v1 implementation will be > > removed in the near future, then I agree this work becomes much harder > > to justify. > > > > Am I being too optimistic about how long the remaining v1 code is > > expected to stay around? > > Well, Idk, it was considered deprecated for quite some time already, > so maybe announcing that it will be deleted in a year is reasonable? That might be tougher for v1 users than the member placement :-) My understanding is that there are still a few heavy v1 users out there. I'm not sure they can move within that timeframe. Personally I think the cost of the v1 code now is kind of negligible now? > Shakeel, Johannes, Michal, wdyt? I was a weak yes on Tao's patch. Happy to keep it out with you and Michal not being fans of it.