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Wed, 26 Feb 2025 19:52:00 -0800 (PST) Date: Wed, 26 Feb 2025 22:51:55 -0500 From: Johannes Weiner To: Shakeel Butt Cc: Michal =?iso-8859-1?Q?Koutn=FD?= , Roman Gushchin , "T.J. Mercier" , Tejun Heo , Michal Hocko , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: add hierarchical effective limits for v2 Message-ID: <20250227035155.GA110982@cmpxchg.org> References: <20250205222029.2979048-1-shakeel.butt@linux.dev> <5jwdklebrnbym6c7ynd5y53t3wq453lg2iup6rj4yux5i72own@ay52cqthg3hy> <20250210225234.GB2484@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 4230A120007 X-Rspamd-Server: rspam12 X-Stat-Signature: 4uchqe6idfezyq7f3k3ecu33dugnk8er X-HE-Tag: 1740628322-106385 X-HE-Meta: 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 lBEd9o4q o66Q2x+/X5M+opSiQ5LLmHTbOCEpkHnWJQfiIH5NrCXm014F0ae50xeIkDka/bjvpl+KvBNsLP46Oks287CbkGCiRsz0MXpv3Pz6yrMtBwZAIPEJJecb4dDPGyIU56V7UfK+HJ7Se3UNJPua+AJZuBuWG5YVC7ODTbFAfrQf0HUmlGNVmF3CRVztx8Gn/09uFW+yml895/oKekBIjqJ1eli/XeLxgQs6b5IiJ5l2wq386LbFIchQGLkq15ZkCUNnxszOkyPDfJxSXqYtMhQXWrny4HubK6e2KWkxE1S5C5AAvdw3WjxcPAO8TMRizkpHK6V6HM7zVB35wrshOk3WLLx4BZg9UX4Hk5M6i/dovjQ9nEyk/oPIperMHFAa9hDXuSNccXfIFszMov59kxCDFpzR7pPa9Gw5Qj0SY2uPRBZAmQnuizPJObHZqWH8n3H6k03VBzrI4TiHKFLQ4a8eb3DMCqT6LlsifuyHU39ZWbOvoGcU= 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 26, 2025 at 01:13:28PM -0800, Shakeel Butt wrote: > Sorry for the late response. > > On Mon, Feb 17, 2025 at 06:57:46PM +0100, Michal Koutný wrote: > > Hello. > > > > [...] > > > > The most simple explanation is visibility. Workloads that used to run > > > solo are being moved to a multi-tenant but non-overcommited environment > > > and they need to know their capacity which they used to get from system > > > metrics. > > > > > Now they have to get from cgroup limit files but usage of > > > cgroup namespace limits those workloads to extract the needed > > > information. > > > > I remember Shakeel said the limit may be set higher in the hierarchy for > > container + siblings but then it's potentially overcommitted, no? > > > > I.e. namespace visibility alone is not the problem. The cgns root's > > memory.max is the shared medium between host and guest through which the > > memory allowance can be passed -- that actually sounds to me like > > Johannes' option b). > > > > (Which leads me to an idea of memory.max.effective that'd only present > > the value iff there's no sibling between tightest ancestor..self. If one > > looks at nr_tasks, it's partial but correct memory available. Not that > > useful due to the partiality.) > > > > Since I was originally fan of the idea, I'm not a strong opponent of > > plain memory.max.effective, especially when Johannes considers the > > option of kernel stepping back here and it may help some users. But I'd > > like to see the original incarnations [2] somehow linked (and maybe > > start only with memory.max as > > that has some usecases). > > Yes, I can link [2] with more info added to the commit message. > > Johannes, do you want effective interface for low and min as well or for > now just keep the current targeted interfaces? I think it would make sense to do min, low, high, max for memory in one go, as a complete new feature, rather than doing them one by one. Tejun, what's your take on this, considering other controllers as well? Does that seem like a reasonable solution to address the "I'm in a namespace and can't see my configuration" problem?