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Mercier" , Eric Chanudet , Sumit Semwal , Benjamin Gaignard , Brian Starkey , John Stultz , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, "open list:MEMORY MANAGEMENT" References: <20251211193106.755485-2-echanude@redhat.com> <20251215-sepia-husky-of-eternity-ecf0ce@penduick> <07cdcce2-7724-4fe9-8032-258f6161e71d@amd.com> <20251215-garnet-cheetah-of-adventure-ca6fdc@penduick> <20251219-large-daffy-monkey-74665d@houat> <5eda1755-865c-4bb0-a1a0-a4e6dac5388c@amd.com> <20251219-cuddly-platinum-cormorant-ae6d0e@houat> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20251219-cuddly-platinum-cormorant-ae6d0e@houat> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: YT4P288CA0094.CANP288.PROD.OUTLOOK.COM (2603:10b6:b01:d0::22) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|SJ0PR12MB6782:EE_ X-MS-Office365-Filtering-Correlation-Id: 2cc9ba21-aa47-41f4-82bd-08de4de71680 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014; 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As far as I can see there is a huge chance we >>>>>> break existing use cases with that. >>>>> >>>>> Which ones? And what about the ones that are already broken? >>>> >>>> Well everybody that expects that driver resources are *not* accounted to memcg. >>> >>> Which is a thing only because these buffers have never been accounted >>> for in the first place. >> >> Yeah, completely agree. By not accounting it for such a long time we >> ended up with people depending on this behavior. >> >> Not nice, but that's what it is. >> >>> So I guess the conclusion is that we shouldn't >>> even try to do memory accounting, because someone somewhere might not >>> expect that one of its application would take too much RAM in the >>> system? >> >> Well we do need some kind of solution to the problem. Either having >> some setting where you say "This memcg limit is inclusive/exclusive >> device driver allocated memory" or have a completely separate limit >> for device driver allocated memory. > > A device driver memory specific limit sounds like a good idea because it > would make it easier to bridge the gap with dmem. Completely agree, but that approach was rejected by the cgroups people. I mean we can already use udmabuf to allocate memcg accounted system memory which then can be imported into device drivers. So I don't see much reason why we should account dma-buf heaps and driver interfaces to memcg as well, we just need some way to limit them. Regards, Christian. > > Happy holidays, > Maxime