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Wed, 05 Feb 2025 10:08:47 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:da5e:d3ff:fee7:26e7]) by smtp.gmail.com with UTF8SMTPSA id d75a77b69052e-46fdf0a74a5sm72911691cf.8.2025.02.05.10.08.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Feb 2025 10:08:46 -0800 (PST) Date: Wed, 5 Feb 2025 13:08:42 -0500 From: Johannes Weiner To: Hamza Mahfooz Cc: linux-mm@kvack.org, Roman Gushchin , Shakeel Butt , Andrew Morton , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo , Michal =?iso-8859-1?Q?Koutn=FD?= , Michal Hocko , Muchun Song , Allen Pais , Yosry Ahmed Subject: Re: A path forward to cleaning up dying cgroups? Message-ID: <20250205180842.GC1183495@cmpxchg.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D0DD1A000C X-Stat-Signature: qpfm1pcpyd5nx3j6g1nxna697ys7xe3z X-HE-Tag: 1738778928-977725 X-HE-Meta: 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 +cP+lkkq 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.007838, 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 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. 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. 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?