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Mercier" , Alistair Popple , Tejun Heo , Michal Hocko , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jhubbard@nvidia.com, hannes@cmpxchg.org, surenb@google.com, mkoutny@suse.com, daniel@ffwll.ch, "Daniel P . Berrange" , Alex Williamson , Zefan Li , Andrew Morton Subject: Re: [PATCH 14/19] mm: Introduce a cgroup for pinned memory Message-ID: References: <87o7pmnd0p.fsf@nvidia.com> <87k009nvnr.fsf@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MN2PR20CA0028.namprd20.prod.outlook.com (2603:10b6:208:e8::41) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|DM6PR12MB4355:EE_ X-MS-Office365-Filtering-Correlation-Id: 7caabec5-fefe-4683-076a-08db15c94f7a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV2PR12MB5869.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230025)(4636009)(396003)(346002)(39860400002)(366004)(136003)(376002)(451199018)(86362001)(36756003)(2616005)(54906003)(316002)(41300700001)(66556008)(66946007)(66476007)(6916009)(8676002)(4326008)(53546011)(6486002)(6506007)(6512007)(478600001)(186003)(26005)(38100700002)(7416002)(5660300002)(8936002)(83380400001)(2906002);DIR:OUT;SFP:1101; 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Mercier wrote: > > > > > > Solving that problem means figuring out when every cgroup stops using > > > > the memory - pinning or not. That seems to be very costly. > > > > > > > This is the current behavior of accounting for memfds, and I suspect > > > any kind of shared memory. > > > > > > If cgroup A creates a memfd, maps and faults in pages, shares the > > > memfd with cgroup B and then A unmaps and closes the memfd, then > > > cgroup A is still charged for the pages it faulted in. > > > > As we discussed, as long as the memory is swappable then eventually > > memory pressure on cgroup A will evict the memfd pages and then cgroup > > B will swap it in and be charged for it. > > I am not familiar with memfd, but based on > mem_cgroup_swapin_charge_folio() it seems like if cgroup B swapped in > the pages they will remain charged to cgroup A, unless cgroup A is > removed/offlined. Am I missing something? Ah, I don't know, Tejun said: "but it can converge when page usage transfers across cgroups if needed." Which I assumed was swap related but I don't know how convergence works. Jason