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[2603:800c:1a02:1bae:44e6:6a58:44be:40a6]) by smtp.gmail.com with ESMTPSA id a5-20020a17090a740500b0022c0622cc16sm3067685pjg.54.2023.02.06.16.32.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Feb 2023 16:32:39 -0800 (PST) Date: Mon, 6 Feb 2023 14:32:37 -1000 From: Tejun Heo To: Jason Gunthorpe Cc: Yosry Ahmed , 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, "Daniel P . Berrange" , Alex Williamson , Zefan Li , Andrew Morton Subject: Re: [PATCH 14/19] mm: Introduce a cgroup for pinned memory Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D5B721C000F X-Stat-Signature: hzquxp46a3udua4ao1gh3o86na5erd5g X-Rspam-User: X-HE-Tag: 1675729961-750228 X-HE-Meta: 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 WE1mDKbD 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000310, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, On Mon, Feb 06, 2023 at 07:40:55PM -0400, Jason Gunthorpe wrote: > (a) kind of destroys the point of this as a sandboxing tool > > It is not so harmful to use memory that someone else has been charged > with allocating. > > But it is harmful to pin memory if someone else is charged for the > pin. It means it is unpredictable how much memory a sandbox can > actually lock down. > > Plus we have the double accounting problem, if 1000 processes in > different cgroups open the tmpfs and all pin the memory then cgroup A > will be charged 1000x for the memory and hit its limit, possibly > creating a DOS from less priv to more priv Let's hear what memcg people think about it. I'm not a fan of disassociating the ownership and locker of the same page but it is true that actively increasing locked consumption on a remote cgroup is awkward too. Thanks. -- tejun