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[2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id q5-20020a170902c74500b00183c67844aesm3334819plq.22.2023.01.27.13.44.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Jan 2023 13:44:20 -0800 (PST) Date: Fri, 27 Jan 2023 11:44:19 -1000 From: Tejun Heo To: Alistair Popple Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jgg@nvidia.com, jhubbard@nvidia.com, tjmercier@google.com, hannes@cmpxchg.org, surenb@google.com, mkoutny@suse.com, daniel@ffwll.ch, Zefan Li , Andrew Morton Subject: Re: [RFC PATCH 14/19] mm: Introduce a cgroup for pinned memory Message-ID: References: <183372b80aac73e640d9f5ac3c742d505fc6c1f2.1674538665.git-series.apopple@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <183372b80aac73e640d9f5ac3c742d505fc6c1f2.1674538665.git-series.apopple@nvidia.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C9BCF120011 X-Rspam-User: X-Stat-Signature: d6jqtrkmkdhskzus7irnudw4h3kpxruw X-HE-Tag: 1674855862-835276 X-HE-Meta: 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 gPuEDibm 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 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 Tue, Jan 24, 2023 at 04:42:43PM +1100, Alistair Popple wrote: > If too much memory in a system is pinned or locked it can lead to > problems such as performance degredation or in the worst case > out-of-memory errors as such memory cannot be moved or paged out. > > In order to prevent users without CAP_IPC_LOCK from causing these > issues the amount of memory that can be pinned is typically limited by > RLIMIT_MEMLOCK. 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. Thanks. -- tejun