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From: Yosry Ahmed To: Johannes Weiner Cc: Hamza Mahfooz , linux-mm@kvack.org, Roman Gushchin , Shakeel Butt , Andrew Morton , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo , Michal =?utf-8?Q?Koutn=C3=BD?= , Michal Hocko , Muchun Song , Zach O'Keefe , Kinsey Ho , Yosry Ahmed , Allen Pais Subject: Re: A path forward to cleaning up dying cgroups? Message-ID: References: <20250205180842.GC1183495@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250205180842.GC1183495@cmpxchg.org> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 506151C0019 X-Stat-Signature: syajr93ir3sd76qkfeum3x3js9qmfa4w X-HE-Tag: 1738779376-70461 X-HE-Meta: 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 K+fSl+js 1bKo4/n58E61NA11mgq4HoJ8tTKXyOo1gAtkEi1ZiyY626ZSWGEnmRD6wOJNmJr36ExsC6Ff1yrW6h0qheqRminh9Fp8Axno9e2W2O9QUCN9UAsvt5jbWxJVtYq6U/rRBnleHmV7udsckXI2yPpqM0gq+422M2RGpBf65kixfEl/KXtZ0v0PueAzFpfutUGyB6+jqk466oLKcTaajLlXcevHlpnEWqo2Toti6GvanDcv2nU1UAhcvip3pS5rAUP3zTs8JRJlz41e2sds= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 05, 2025 at 01:08:42PM -0500, Johannes Weiner wrote: > On Wed, Feb 05, 2025 at 12:50:19PM -0500, Hamza Mahfooz wrote: > > Cc: Shakeel Butt > > > > On 2/5/25 12:48, Hamza Mahfooz wrote: > > > I was just curious as to what the status of the issue described in [1] > > > is. It appears that the last time someone took a stab at it was in [2]. > > If memory serves, the sticking point was whether pages should indeed > be reparented on cgroup death, or whether they could be moved > arbitrarily to other cgroups that are still using them. > > It's a bit unfortunate, because the reparenting patches were tested > and reviewed, and the arbitrary recharging was just an idea that > ttbomk nobody seriously followed up on afterwards. There was an RFC series [1] for the recharging, but all memcg maintainers hated it :P https://lore.kernel.org/lkml/20230720070825.992023-1-yosryahmed@google.com/ > > We also recently removed the charge moving code from cgroup1, along > with the subtle page access/locking/accounting rules it imposed on the > rest of the MM. I'm doubtful there is much appetite in either camp for > bringing this back. Yeah with the charge moving code gone the case for recharging grows weaker. > > So I would still love to see Muchun's patches merged. They fix a > seemingly universally experienced operational issue in memcg, and we > shouldn't hold it up unless somebody actually posts alternative code. > > Thoughts? Adding Zach and Kinsey who were recently looking into this from the Google side.