From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D9702DEA61; Fri, 17 Apr 2026 09:51:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776419480; cv=none; b=k8Ew7J85B7E5tAR1onyhe3WMfvftF/hUBkg0wtNE+rVCmR7gmZMkMzjLatczo/Blw8nQE0G3/648A3mmUSi7gblZ2vJOKnl5t8vptdVlxZwh87fC1YeMqF5o2L4+O5eMDryeqM8PnsnnZtvuDZwfnnRLJRWpf/ojKz9oP0VjKbU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776419480; c=relaxed/simple; bh=K+ulvf1w3U8a+KN7T54hOG5ryDsrSUTMSLNev+ah4n8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=j9N6LPbrJMllYJ8G3UH/d6aNaK4HQ3Z1c3NxP9xCLMne691AUR5n5NzdP22n053PxONSj1k7DFwCJ7WtrwrgkB61EQsBi+f8zbfnPpiaOwVJ6V0JxVaUy31R/aVUtjjVVpbPYVF0s75g65eZRieODGk/eT9zLdBsai6gkPDax2E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=axeTsh32; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="axeTsh32" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FEB9C19425; Fri, 17 Apr 2026 09:51:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776419479; bh=K+ulvf1w3U8a+KN7T54hOG5ryDsrSUTMSLNev+ah4n8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; 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 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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