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Wed, 06 May 2026 07:43:47 -0700 (PDT) Date: Wed, 6 May 2026 15:43:35 +0100 From: Gregory Price To: Alejandro Lucero Palau Cc: lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, kernel-team@meta.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, dan.j.williams@intel.com, longman@redhat.com, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, 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, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com, sj@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, jannh@google.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, pfalcato@suse.de, rientjes@google.com, shakeel.butt@linux.dev, riel@surriel.com, harry.yoo@oracle.com, cl@gentwo.org, roman.gushchin@linux.dev, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, zhengqi.arch@bytedance.com, terry.bowman@amd.com Subject: Re: [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM) Message-ID: References: <20260222084842.1824063-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Feb 25, 2026 at 12:40:09PM +0000, Alejandro Lucero Palau wrote: > > I can see the nid param is just a "preferred nid" with alloc pages. Using > __GFP_PRIVATE will restrict the allocation to private nodes but I think the > idea here is: > > > 1) I own this node > > 2) Do not give me memory from another private node but from mine. > > I mildly mis-read this question, apologies. Multiple private nodes in the nodemask are ignored, because the nodemask is a filter function for the fallback lists - and private nodes never show up in the fallback lists (except for their own). So for example Nodes: Normal(A,B), Private(C,D) Fallback lists: A: [A,B] B: [B,A] C: [C,A,B] D: [D,B,A] combination | possible result ---------------------------------------------------------------- __GFP_PRIVATE + pref_node(C) + nodemask(NULL) = (C or A or B) __GFP_PRIVATE + pref_node(C) + nodemask(C,D) = C GFP_PRIVATE + pref_node(C) + nodemask(ALL) = C Basically private nodes are completely ignored in the nodemask, so you cannot do fallback allocations to other private nodes. There is no good abstraction (that I have found) to communicate multi-private-node allocations simply because this would imply needing private nodes to be in the fallback lists for other nodes. Maybe there is a possibility of modifying fallback lists explicitly, but I think that is out of scope for the first implementation. ~Gregory