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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 Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 666502000B X-Stat-Signature: h7kmuru4cbu65xkgmc1ia4ndx5y1ok4k X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1677176082-376893 X-HE-Meta: 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 +6/QtDwt IE7CConzCmeY25cLLVK8qJ4puiWdRX5KnctteebSCAFVjSDeZHDrwBj5ip7Jpai8GIpM2COPjmIw6lGzd3Iwj3AKS4i+MopjktROufpWdsy9/nlTgOd4ifNAfikNeOCYrzRCQQyB+3f4kHpyL2idZTou+a9f4oUciJfxsNPiaBt2yCh2Pt5zclvvxx3WAtCogXuQhBnQ2F0uTxthiuZkGRXaEeQgica3X/yXF8KU9Vv6+NZshxD4pHjHDlEa51q+1E9DRiD+pNVQWt7U= 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: On Thu, Feb 23, 2023 at 10:11 AM Jason Gunthorpe wrote: > > On Thu, Feb 23, 2023 at 10:03:50AM -0800, Yosry Ahmed wrote: > > On Thu, Feb 23, 2023 at 9:28 AM Jason Gunthorpe wrote: > > > > > > On Thu, Feb 23, 2023 at 09:18:23AM -0800, T.J. 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. I believe that's the case for file-backed pages, but I do not believe it's the case for swap-backed pages. > > Jason