From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9E83EC79F8C for ; Wed, 9 Sep 2026 09:33:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 989C06B008A; Wed, 9 Sep 2026 05:33:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 961846B008C; Wed, 9 Sep 2026 05:33:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 850B26B00A0; Wed, 9 Sep 2026 05:33:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 60EA56B008A for ; Wed, 9 Sep 2026 05:33:39 -0400 (EDT) Received: from smtpin14.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 84AB01A016D for ; Wed, 9 Sep 2026 09:33:38 +0000 (UTC) X-FDA: 85193711316.14.E782274 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf18.hostedemail.com (Postfix) with ESMTP id B35B21C0003 for ; Wed, 9 Sep 2026 09:33:36 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="ahdV/XU2"; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788946416; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SLdffO2d9oL1IoLe1z/izylXPi/WCd92jfvx6mYcYdY=; b=wutxcPGr7/4RwTzh0XgsAah9x//YWxjbQ5RbFFtjEv773bbec7Wgm5a4fsr1tQP+J/Xs8A iOef53HBegI1gGiqKJ1aV/zcIrYwLIYJ9I9HXp4hi5nBn6omMkRzjYG7omgGRdtlxlOpaQ 4nG27RdOoif8WCr9Tf8LahJlZYek5no= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788946416; b=ZiBcx/fb997Wtnok+WljaXtT/iY3YFvoDNFmwfHA+biRAhDuMTw3kHngSQskksZBx+jebs Ndvnlr9Sg17B1aH8njc4TDRDubSofr+NnQ8p6M45SK82mUfh8TAgzRAheFXs0rcc7SNcsC TRct0pzeiPnd53PWH5i950P8SvKR+yw= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="ahdV/XU2"; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id E018A4045C; Wed, 9 Sep 2026 09:33:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 728381F00A3A; Wed, 9 Sep 2026 09:33:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788946415; bh=SLdffO2d9oL1IoLe1z/izylXPi/WCd92jfvx6mYcYdY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ahdV/XU21+mGhwldu2hspAkKmm3G/Pdk7ZP7FMpkYSl+VgEhXZ9h5Xoe8L1IlIyn8 Lw3boxLMaHBmtMYJ/z+hyo8B1ErAzgFTbA2aW+Z2kshp3KZkZjLpEP52qbXrScEunL lqsMz5xQIWAL6AkOUi0FoXisNE+JfsMSsKI3XTJ6pLTeIETN3P/7hmr8Lvo/zi7Uuz B/GkJd+1JnPO900+EM1QO3CodSYd+hnYsQIua+CqcZbaiNGT5aOEQEjP36packx1uU aWUNIEdmOlEBDmLTztIjJi7tHgzx/tyBpXn0109kpG4Nh4CUeHoxJY5ZdCUmxgIk9x ZAnyvFbtvGD5w== Message-ID: Date: Wed, 9 Sep 2026 11:33:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 01/17] mm/sparse: relax struct mem_section size constraints To: Muchun Song , Andrew Morton , Oscar Salvador Cc: Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Michal Hocko , David Laight , "Liam R . Howlett" , Suren Baghdasaryan , Qi Zheng , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song References: <20260825084608.47437-1-songmuchun@bytedance.com> <20260825084608.47437-2-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260825084608.47437-2-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: 4eu4sjfb4fziwnowbs93p395xabkeydj X-Rspamd-Queue-Id: B35B21C0003 X-HE-Tag: 1788946416-952384 X-HE-Meta: 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 zSGBDDbR FueyKRT39LzRu7RUAPjWnSvwR9jUZ63TjjfTJI5laZQbDyNUvPs2+CFtwQiUqLoDudRDM/qO3axR3KERP2EzeE3POkzRzY3Jje+CMLZPCvy7ocDaITzJ8QJueaBtks48QTEmnQVrlZm2dFvtqRv8+l+AmasItLPrkWJ98j5Xd2KHql50ncFfgH+DlOKP4Bk/gXxZCOiy5v4TL/3Q/mRkjRly0qM8H7PELD2B8jWQCzfG6oXaurAnYH7ixs+Njadqrr7Xm71ZzuM9/HbeNuVTXSOrIeob5hcAiE3txlmcT/2EtChl8ajsQhMzH34UgIujutmNv3uDdJwy2Jk4wfPLwZXl7xNmKcCRmLeSGztaV8QYzngeEyLAeMMdf983pwl5V+9We7cSCCtUzRIqvj7mT7F5uYBTtig0PjCvtQrPxnbzkfUA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/25/26 10:45, Muchun Song wrote: > struct mem_section is currently forced to a power-of-2 size so the > section-to-root lookup can use a mask instead of a modulo. > > That requirement makes future extensions harder than necessary: adding a > small field can require configuration-dependent padding or layout checks > just to preserve the lookup scheme. Keep the lookup correct for any > struct mem_section size by using a plain modulo instead. > > Do not leave the layout entirely unconstrained, though. Keep struct > mem_section double-word aligned so modest size changes, such as adding > another word-sized field on 64-bit systems, still keep a compact and > efficient layout. If future fields grow the structure beyond that sweet > spot, the lookup remains correct; only the exact layout efficiency > changes. > > Signed-off-by: Muchun Song > Acked-by: Mike Rapoport (Microsoft) > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David