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b=O3r8zX3rRAdTh0tZ7rs6DQexuLgO9QK0vtOA6kKeN8MadLlRZl/xbGDhgQW1w9lLr RIMwyajFNVsPe+RnDMMptexa7Z+k3f+aK8i6Wlj37NMZ8VtcfTGeDp8IJNnoMqI8nf 23lATnS4SrmJdOkZpjKxmuDOeI3HwfpP3FYOgOLS4l1JlEoQ74ksPe2EPombWAmaub i0BPGA2SU2TmTWn+l8hwAesNTCiAzu0AJTgWPzfgXmjRD4GY6zCyoW8sQAgFR2JOfZ cSYaC5nq11ykUAUAqGSBD9FbdPahivlPZaQYvxyGMz4EVzYyXb85FpKYMU9aRTh/h8 ObdTOs2AVvpyA== Message-ID: <7e555045eff532576b56daa4e023be1b@kernel.org> From: Tejun Heo To: Qiliang Yuan Cc: christian.koenig@amd.com, ray.huang@amd.com, matthew.auld@intel.com, matthew.brost@intel.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, natalie.vock@gmx.de, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, thomas.hellstrom@linux.intel.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v8] cgroup/dmem: implement dmem.high soft limit with proactive reclaim Date: Mon, 21 Sep 2026 08:13:47 -1000 In-Reply-To: <20260921-feature-dmem-high-v8-1-6371fa83d6c3@gmail.com> References: <20260921-feature-dmem-high-v8-1-6371fa83d6c3@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: hk8q6d74dbpd94jap3iabx8a8fji5eim X-Rspamd-Queue-Id: 791BDC0003 X-HE-Tag: 1790014589-163076 X-HE-Meta: U2FsdGVkX1826lhLP0HcIpcABCMIQDhD4xJSWWAAb9aSV5F2sOtEl9NoEl7QJo5ckncC5OljO8yios9GP/y5pwFqM6wQsaz1U0wL/s0loLRY0v3/qiYOVpiL7iXwDnzLKJsbj96yZoHY3ZOtDlM9QcaCgBH++d+oYAE1w9PIb5X4rV3mKUJS5AVqBNStHhNcXweeCKHdVEWxgC0OcGpUkNeFMmUege575cPQgMWoN7v+qlF4KEdaybQ+nCOyQbCW2t8acd9dmXx5++bTzUBgPKjePUP7F51sxX8pGhpiGKGAX90p3nJfUC7pTpH085JokiFh8Zq2xqVFOhubuOuMnp7lfJL1buue/H4FgXTsxgaVaQoNjuX3H5QijqoeNIPcBFXZ/Mn6+e7iWNQOCKLGfVFJxG5YSxCq/9YiUg4w6TjqcsExStZGdN2F/1cWEGwEzqzeYHkzenRel9d7fF2rCd68x/uyw8D8em7tyMLUINiO4h6NixLERWTLf92c0DwXZdICmnX8tqfsOUrMdjh7SeAQfPpZkN+msUAu6u8BK4mxHMOS7Zdz0/T4Qz497jjqEf5RmOX4SG2DwEbIUmEkYZ0Kqk1aXw2aXbXcs5w6hZq8J2eZccN43G2wk6iH/9HbLxL4Vgk913PCkd6eIhngZKxJFHfYC1sWirDz8fPpeOpZTrfKbytHB+pwcmNa9Xqzv4LA5heFN3q4+vnnsBm/VuN0Iaz2SKa8AQIK2HXRvH0AF39q1TIovruccyhKVj4ip6GF/2wAMMKdWnwgB7BxMc1XaqHlDgESEN3fn/f4SuHCXEgSf9eGa9nBhrzivHNymjhQXGSoh3FSrINnmIdCCYhqOZTMd0DoAWaOFNwI6HzodUKsZcNU7W9qF1eU4MssLJaX3ATGE2Ako8t8Qr/8jQGJAMxj5Y6oETtuFF2Qg4saPTyYSPJYtfCD0wIUIsPU5dfBmA6ASNe6tnOkp3j I8DJuTi4 TJzcRPFikdHS2sX460QxmnYecmcZooNpVJTTB7gg2ISGwKNyQL6sl02L+u7nq8TrYa65dzEVbHPz2Y0A5xoq1+wVg+WoiRwk/kcRT1TM5tlFRPdp1QD1VAGpFl2z3AXORGqinVKKXmD32VNUBGjOt3rCHEjD0iAgX7/BOB2NU2sYqaJTVZCWACpcepJPqeorDuuLfEQmUvnbIjnAwvVEr0lVmXya4Os55e31oO/C/4WItr8uqn1NI92eMya1oiPeUp8WU+J22b86ETpmZWpaIoRs6ifwseh3/uqNp2nna2RqpbAsDcDpB8BqlSCWM9lcOLu/F0SSXncCjl8qeo20oYyRv+NcQMBNLDnvb Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, On Mon, Sep 21, 2026 at 03:02:48PM +0800, Qiliang Yuan wrote: > The dmem cgroup v2 controller only provides a hard "max" limit, which > fails allocations outright once a cgroup's device memory usage hits > its quota. GPU-bound AI workloads need smoother over-subscription: a > soft limit that applies backpressure through reclaim before the hard > limit is hit. That's not how max behaves. A max hit makes TTM evict and retry before the allocation fails, and since 747c4bb450ad ("cgroup/dmem: Add reclaim callback for lowering max below current usage") lowering max reclaims as well. So the premise doesn't hold, and the patch doesn't show a concrete case where max reclaim falls short and high would help. Without that, there isn't enough justification for adding a new interface file. Thanks. -- tejun