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[96.255.20.42]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4b48f756d16sm102123611cf.34.2025.09.08.10.50.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Sep 2025 10:50:35 -0700 (PDT) Date: Mon, 8 Sep 2025 13:50:33 -0400 From: Gregory Price To: Jinjiang Tu Cc: mhocko@suse.com, rientjes@google.com, shakeel.butt@linux.dev, akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, wangkefeng.wang@huawei.com Subject: Re: [PATCH] mm/oom_kill: kill current in OOM when binding to cpu-less nodes Message-ID: References: <20250904134431.1637701-1-tujinjiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250904134431.1637701-1-tujinjiang@huawei.com> X-Stat-Signature: f33gyqr59mphnnqs3a9qf98773zmmbg9 X-Rspam-User: X-Rspamd-Queue-Id: 17F7B100019 X-Rspamd-Server: rspam04 X-HE-Tag: 1757353847-940551 X-HE-Meta: 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 O8xUNsti CJRY/HSwC69BTA60s+NX6O8lp6sA79YprfVNv4mfnU2zohq09P1gE3dw3Dgarg3LSPiSIeFTea7OH3mIEctr2XoYaH5tRpCWeH6bcQTRu6dIY6P00AfOO2nej8WraBDEx2Pe5kbXG8iubxU1By55nU9wy/Z4cP6veCr2qZjET+aZ/ExA51qw6Q0w/48uHJ5PVgCofqw0K+vl1Ocf2oqA4Gy9hw8Zu700k/FZm2aBNp+i5tb+Lq+m0wuSyvAWJNmI1fpAN6us7cOYjFGlT4MN5Cw+j6lwXJkc9EGwjx529JgECxTcjt+uwSgluW0hJIQ2URkXJ4qKt8fpeatGyUgNYdXzTsr2g8wAl+9uHSwgM3JFOJIpNtcXCGQLmhnDVQUBb68+A50WmljLsSCFN4zLFWAozXwWsniYo7EGy9HDjrgF6r+Q1pYAW5xEK95ZRKmykuILg 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: List-Subscribe: List-Unsubscribe: On Thu, Sep 04, 2025 at 09:44:31PM +0800, Jinjiang Tu wrote: > out_of_memory() selects tasks without considering mempolicy. Assuming a > cpu-less NUMA Node, ordinary process that don't set mempolicy don't > allocate memory from this cpu-less Node, unless other NUMA Nodes are below > low watermark. If a task binds to this cpu-less Node and triggers OOM, many > tasks may be killed wrongly that don't occupy memory from this Node. > I don't think mempolicy is the right source of information for this, as mempolicy is non-restrictive. Mempolicy is not necessarily respected by reclaim, for example. A task without mempolicy can still end up using cpu-less nodes for a number of reasons - for example pro-active reclaim, shared pagecache, shared file mappings (KSM), etc etc etc. If mempolicy were restrictive by default, this would be a different story, but I have to agree with Michal that I don't think mempolicy is the right source of information for this. It seems much more appopriate to use cpusets to inform oom_kill. > To fix it, only kill current if oc->nodemask are all nodes without any cpu. > This feels very heuristic-y and way too narrow of a use case. My gut reaction is that there must be better way to get what you're looking for ~Gregory