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Berrange" , Alex Williamson Cc: Alistair Popple , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jhubbard@nvidia.com, tjmercier@google.com, hannes@cmpxchg.org, surenb@google.com, mkoutny@suse.com, daniel@ffwll.ch, Zefan Li , Andrew Morton , "libvir-list@redhat.com" , Laine Stump Subject: Re: [RFC PATCH 14/19] mm: Introduce a cgroup for pinned memory Message-ID: References: <183372b80aac73e640d9f5ac3c742d505fc6c1f2.1674538665.git-series.apopple@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MN2PR10CA0030.namprd10.prod.outlook.com (2603:10b6:208:120::43) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|CH3PR12MB7500:EE_ X-MS-Office365-Filtering-Correlation-Id: 5bc8978f-06c7-43d8-1347-08db02c4c98b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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However this is inflexible as limits can't be shared > > between tasks and the enforcement of these limits is inconsistent > > between in-kernel users of pinned memory such as mlock() and device > > drivers which may also pin pages with pin_user_pages(). > > > > To allow for a single limit to be set introduce a cgroup controller > > which can be used to limit the number of pages being pinned by all > > tasks in the cgroup. > > The use case makes some sense to me but I wonder whether this'd fit a lot > better in memcg rather than being its own controller. As long as the pinned limitation has its own bucket it is probably fine? The underlying memory allocations should have already been charged to the memcg - so we don't want to double account. Alex and Daniel were looking at this from the qemu/libvirt perspective, perhaps they have some insight what they would like to see? Thanks, Jason