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b=axeTsh32UDz21vorG6qIUZfQps/zki7+NJKe37MM9zm6w5EAS+rFUB6gJtPxVqnsX FbAq5V+E0dIzK5/ESp44Cli783ETjOJheLC0xDbav7zo4CSAHrPM0WTsbbYl1VZBx0 0CdJ3vhzP7NDO4dO/2MTKX2bqZPFNc3f+Rkwiv1QZgpE49xodyWqhkXIJr0MxwZaRo MSHzksXcgrnR3KgkVgwU+hveiav8PTVHEwaKQbi1Sv2zBigUqSYh3Qq5GaDtv1YjBN 2X6V8/4f04OqvGXhSyXHu1/ucyYS9RExfftp0iMXlt9wAihcbGdKG3zBvqz6F3I5FO S4jm5ppN2FiJQ== Message-ID: <6d4f702c-5ad6-4f84-a73e-c9e34965be98@kernel.org> Date: Fri, 17 Apr 2026 11:50:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC][RFC PATCH v4 00/27] Private Memory Nodes (w/ Compressed RAM) To: Gregory Price , Frank van der Linden 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, 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 References: <20260222084842.1824063-1-gourry@gourry.net> <3342acb5-8d34-4270-98a2-866b1ff80faf@kernel.org> <2608a03b-72bb-4033-8e6f-a439502b5573@kernel.org> <38cf52d1-32a8-462f-ac6a-8fad9d14c4f0@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E87ACA0008 X-Rspamd-Server: rspam07 X-Stat-Signature: o6s88b3mbope9pdcaj8gw5zm517a9iaw X-Rspam-User: X-HE-Tag: 1776419480-160252 X-HE-Meta: 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 GNeNNvyL Js5HJ+MULop4sJW1cSG0IRp5Gvc3yJgDqm4EkdKhbMIUr8vGtaU5TGDFNuFTYKoP7lXTZcJHZdpUi+/6c8nspQSM2LQsa9P0ezlwvj86GeOveQh9L1ObsDQ9q1EMoI51mLtwjPZZU0RxGXedssQNnrZaiCs/WBYoicvKXP0M46KWqwzyOhs7tXuOmwMjTIm8tAjKyVW7g4WPS6UCN/AbJGXdBu1dJyuLjw/4QxS/UkUbH1dz4a17tdvyyPY5LdaOMRjyhyzGPyxIseY9mAW5Vs7oF+C3xEI7bPrbXXSE717Zt63AIsFjr7sIfcV8n/WEi0OpVui6p2M4XLLo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/16/26 03:24, Gregory Price wrote: > On Wed, Apr 15, 2026 at 12:47:50PM -0700, Frank van der Linden wrote: >> >> This has been a really great discussion. I just wanted to add a few >> points that I think I have mentioned in other forums, but not here. >> >> In essence, this is a discussion about memory properties and the level >> at which they should be dealt with. Right now there are basically 3 >> levels: pageblocks, zones and nodes. While these levels exist for good >> reasons, they also sometimes lead to issues. There's duplication of >> functionality. MIGRATE_CMA and ZONE_MOVABLE both implement the same >> basic property, but at different levels (attempts have been made to >> merge them, but it didn't work out). > > I have made this observation as well. ZONEs in particular are a bit > odd because they're somehow simultaneously too broad and too narrow in > terms of what they control and what they're used for. > > 1GB ZONE_MOVABLE HugeTLBFS Pages is an example weird carve-out, because > the memory is in ZONE_MOVABLE to help make 1GB allocations more > reliable, but 1GB movable pages were removed from the kernel because > they're not easily migrated (and therefore may block hot-unplug). > > (Thankfully they're back now, so VMs can live on this memory :P) Heh, but longterm-pinning would fail on them (making vfio with VMs angry). Similar to CMA hugetlb. In the latter case, we should have a way to identify "this allocation is actually from the CMA owner, so longterm pinning is perfectly fine". Checking the CMA alloc state would be one approach, but that's rather nasty. I guess there would be ways to make that work. I'd assume that people barely rely on 1GB ZONE_MOVABLE HugeTLBFS Pages (iow, mixing kernel-cmdline ZONE_MOVABLE creation with kernel-cmdline hugetlb reservation). I'll note that there was long long ago a proposal of converting ZONE_MOVABLE to "sticky-movable" page blocks. It wouldn't really solve this problem, though, where the early boot code just does something that's rather stupid. -- Cheers, David