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Fri, 10 Apr 2026 03:12:42 -0700 (PDT) Date: Fri, 10 Apr 2026 03:12:42 -0700 (PDT) From: "Christoph Lameter (Ampere)" To: "Vlastimil Babka (SUSE)" cc: Ming Lei , Harry Yoo , Hao Li , Andrew Morton , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] slab: decouple pointer to barn from kmem_cache_node In-Reply-To: <20260311-b4-slab-memoryless-barns-v1-1-70ab850be4ce@kernel.org> Message-ID: References: <20260311-b4-slab-memoryless-barns-v1-0-70ab850be4ce@kernel.org> <20260311-b4-slab-memoryless-barns-v1-1-70ab850be4ce@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Queue-Id: 241FAC0006 X-Stat-Signature: ab9ins5hzhi4ysytfgehf4kxjz6swniu X-Rspamd-Server: rspam06 X-HE-Tag: 1775816677-395172 X-HE-Meta: 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 4B/RpHML /D/PU8UGbEwzzW4Ns30uFlPP+dxSuM+5UwuvcS3dOvGxt9FQgqyDKsZ/wmuwPpRvSB07bEiVoPLaPPhn67iJbyjHfy3hrU7sxXK/qq0rxtfB6X6cNnyMALCVWBV06VjBx/OZqLuHSJYGIoX9+Q/x3XT718D9IxGKKHNKvPU8HG4BRSeJaFaPkFg3g/YLGFppjTGs0Sfy+8EP4oWD+N0oDVNgCJCyeoO2t0xjlDnERYseo1iekkJGdSmGkzx6FYAzMEbEPa450J+1uyjj2/E5mxD3M7/eg+vpSSPfMigcqIcc+IYEs3+nqD7N6Yw0oBpAadL8B Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 11 Mar 2026, Vlastimil Babka (SUSE) wrote: > The pointer to barn currently exists in struct kmem_cache_node. That > struct is instantiated for every NUMA node with memory, but we want to > have a barn for every online node (including memoryless). Is this breaking the 1-1 association of kmem_cache to numa nodes? I would think you needd local per cpu queues on a memoryless node for performance but not fake node structures. Per node access is already serialized via locks and therefore slow. If you break the association of per cpu queues to cpu and kmem_cache_node to numa_nodes then the code may get complicated.