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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-527d066fa6asm463921cf.6.2026.07.21.11.16.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2026 11:16:27 -0700 (PDT) Date: Tue, 21 Jul 2026 14:16:21 -0400 From: Gregory Price To: Balbir Singh Cc: linux-mm@kvack.org, Zhigang.Luo@amd.com, arun.george@samsung.com, brendan.jackman@linux.dev, yuzenghui@huawei.com, apopple@nvidia.com, alucerop@amd.com, matthew.brost@intel.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, alison.schofield@intel.com, osandov@osandov.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, pbonzini@redhat.com, osalvador@suse.de, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, longman@redhat.com, ridong.chen@linux.dev, tj@kernel.org, mkoutny@suse.com, sj@kernel.org, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, lance.yang@linux.dev, usama.arif@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, driver-core@lists.linux.dev, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-debuggers@vger.kernel.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, cgroups@vger.kernel.org, damon@lists.linux.dev, linux-kselftest@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v5 00/36] Private Memory NUMA Nodes Message-ID: References: <20260720193431.3841992-1-gourry@gourry.net> <6a7aaac3-e70d-4063-9c84-e643db1488e0@nvidia.com> Precedence: bulk X-Mailing-List: cgroups@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: <6a7aaac3-e70d-4063-9c84-e643db1488e0@nvidia.com> On Tue, Jul 21, 2026 at 01:46:01PM +1000, Balbir Singh wrote: > On 7/21/26 5:33 AM, Gregory Price wrote: > > > > Patch Layout > > ============ > > The series is broken into two sections: > > > > 1) N_MEMORY_PRIVATE Introduction. > > Introduce the node state. > > Opt those nodes out of mm/ services. > > > > 2) NODE_PRIVATE_CAP_* features > > A set of mm/ service opt-in flags that augment private > > nodes to make them more useful (i.e. reclaim = overcommit). > > > > NODE_PRIVATE_CAP_LTPIN for private node folio pinning > > NODE_PRIVATE_CAP_NUMA_BALANCING for private-node NUMA balancing > > NODE_PRIVATE_CAP_DEMOTION for private-node tiering demotion > > NODE_PRIVATE_CAP_HOTUNPLUG for opted-in private nodes > > NODE_PRIVATE_CAP_USER_NUMA for userland numa controls > > NODE_PRIVATE_CAP_RECLAIM for opted-in private node reclaim > > > > Looks reasonable, I wonder why USER_NUMA/HOTUNPUG is an opt-in? > Ideologically: Private nodes default to fully isolated, why should any given feature be special? Concretely: User-numa Some devices don't want the user to have control over placement. I have been working on compressed memory, for example, which only ever wants to be used as a reclaim-demotion target. (The reasoning for this is another thread, i plan on publishing my research on this this year) Hot-unplug: Some devices can't necessarily handle unexpected migration, and hot-unplug is fundamentally a migration. So the HOTUNPLUG cap actually means "hot-unplug can execute migrations". If the entire device has pre-drained the memory (all memory is free) then unplug works - it's just not very hot (no migrations) :] Maybe a naming issue? ~Gregory