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 B5789C79F8C for ; Wed, 9 Sep 2026 09:36:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BB1C46B0092; Wed, 9 Sep 2026 05:36:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B89BA6B0093; Wed, 9 Sep 2026 05:36:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AA0446B0098; Wed, 9 Sep 2026 05:36:37 -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 6F0706B0092 for ; Wed, 9 Sep 2026 05:36:37 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 7A6981A016C for ; Wed, 9 Sep 2026 09:36:36 +0000 (UTC) X-FDA: 85193718792.21.EEBFE73 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf09.hostedemail.com (Postfix) with ESMTP id ADA6D140003 for ; Wed, 9 Sep 2026 09:36:34 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="Qb/l7rzW"; spf=pass (imf09.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=1788946594; 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=61cn5W91VBgvdwAX5AGeN1SkiyX6gawVNp1MxJrLTEc=; b=fDKAwuRiiR3JbGIscMIR+W9L68E+s9Ycm+ZLg8dNBUw6W3maHWHUDT0uvXdeZdlmnU0ezU +Z0JcT6aGgxhujOdrhYKDK7B97kc1Z++/pUDB5V5poiWSoz68Q8uNOtzffQpmAZ3r147M9 9733BlqNR0Stumuekhi+4YH4uiIFLUc= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788946594; b=Xv3oWn5J3iZjQTxcXCF3Nsi00Firtd+f9R1Y5pxVOHkJw1/9N/gUxsr6OQrDxjMyN6uV56 ggRaUc9JN2jUfhjPXkwcZhPJiYbKfizbmNVceZ+R9mSqn/RXNgQRFCwQ7W+R9n05XmFTaJ LJJeiMo37TP352xyxUHKMgo+JJORgxE= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="Qb/l7rzW"; spf=pass (imf09.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 A7D7043825; Wed, 9 Sep 2026 09:36:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 518AF1F00A3A; Wed, 9 Sep 2026 09:36:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788946593; bh=61cn5W91VBgvdwAX5AGeN1SkiyX6gawVNp1MxJrLTEc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Qb/l7rzWJ5jbqv8kKCDnAS6EuQ3N4KRM9M6u68pQwe2chd8OrgoTZKKpb5eQ3HzPY erNvfk1LZ29flRIIMHMsdmRijv1d2gQ/CFcYqnFXcWFwmUqxwXAr00M5yPw+jENdHr mitXp+TI8vZtJbOyiHFndFgJzr8q5gJ/0+7g0kMOC9V033D9F7eVTUQfSmh31yFS7t Z3QLs6LyQWRUfP78dzT8o2Jg9a34VdGDp7iVITbIZMg53eWsLhCzJ70VTZ9FBfLxI4 /rPy6rxpcFijryXs3wqZ314cxXvJemCNFAcWmib7LWrO9UGG9bHDmdNzngJhp70/Cd EjUwamppEjhlw== Message-ID: Date: Wed, 9 Sep 2026 11:36:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 03/17] mm/mm_init: skip initializing shared vmemmap tail pages 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> <20260825084608.47437-4-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: <20260825084608.47437-4-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: psnx8j5so9zmuqmdg9zn95h91rhdhnbm X-Rspamd-Queue-Id: ADA6D140003 X-HE-Tag: 1788946594-244436 X-HE-Meta: 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 YnkilWlP xRCmXCdESRqzosmtcGDuniY+OTydHo/818cisu8MVN7ZsHNRh2UHP/nr93sswD1pRlTfcxF93p+idBTLl3Dcg6Rl/xeQvZm5+CpYyBBeweEg4fCwVoGuLsLwejSqkqOE5L5bxMqWtUTQLjSvCuUW5b6DQN4cx3tzZoZwXqKf4FpfB+OBwiGhfLRrh6zpstgtfLmWPJ4GdQ7F6Tm9+lsCa7ZbKzuP4iuYK0Z04ZucZgI/kT3qGpTxSrPno5loHmourNfmVLeHNwsRJcUAkmkNXk/YG5okuoU6pCVoymTO0K1DVKOulEdnDnQ53RLYjj2Jz8FaU/X2+6XityjCvLsLheqyaGjlIExuWKafdvfrJyUuctrAv5on8r3Mhluvyaqv/Yyfc03MOYln8cuzpOdd0Ud1gWg== 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: > memmap_init_range() initializes every struct page in the target range. > For compound pages with vmemmap optimization, the tail struct pages are > backed by a shared vmemmap page. > > Initializing those tail struct pages would overwrite the shared > vmemmap page contents, requiring users such as HugeTLB to restore the > metadata afterwards. > > Track the compound order for HVO-backed sections and use that metadata > to detect struct pages that fall into the shared tail vmemmap range. > Skip those shared tail pages in memmap_init_range(), then initialize > pageblock migratetypes for the processed range with a helper after the > per-page initialization loop. > > Keep direct mem_section access inside sparse helpers by exposing > pfn_to_section_order() to users that only need the order associated with > a PFN. This lets memmap_init_range() skip shared tail vmemmap pages > without exposing __pfn_to_section() to !SPARSEMEM builds. > > This is a preparatory change for consolidating handling across users of > vmemmap optimization, and it also avoids redundant initialization of > shared tail vmemmap pages during early boot. That early-boot benefit > appears only once HugeTLB is switched to this common handling, since > HugeTLB is the early-boot user that creates those shared tail vmemmap > pages. > > Signed-off-by: Muchun Song > --- > v5: > - Add comments for pageblock migratetype helper callers and shared > tail vmemmap skipping (suggested by Mike Rapoport) > > v4: > - Rename pfn_vmemmap_optimizable() to vmemmap_optimizable_pfn() > for consistency with vmemmap_optimizable_order() > > v3: > - Replace the !SPARSEMEM __pfn_to_section() stub with > pfn_to_section_order() (suggested by Mike Rapoport) > > v2: > - Fold section order tracking into the first user instead of keeping a > standalone API-only patch (suggested by Mike Rapoport) > - Rename page_vmemmap_optimizable() to pfn_vmemmap_optimizable() and > pass a PFN directly (suggested by Mike Rapoport) > - Initialize pageblock migratetypes from a helper after the per-page > loop (suggested by Mike Rapoport) > - Use a 1G PFN chunk for cond_resched() in the pageblock helper > (suggested by Mike Rapoport) > - Guard section_order() with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP so > it returns 0 when HVO is disabled and lets the compiler optimize the > code as much as possible (suggested by Mike Rapoport) > - Explain why the !SPARSEMEM __pfn_to_section() stub belongs here > (suggested by Mike Rapoport) > --- > include/linux/mmzone.h | 8 ++++++++ > mm/mm_init.c | 40 +++++++++++++++++++++++----------------- > mm/sparse.h | 33 +++++++++++++++++++++++++++++++++ > 3 files changed, 64 insertions(+), 17 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 5fb9b37819d5..df31cac12311 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -2022,6 +2022,14 @@ struct mem_section { > unsigned long section_mem_map; > > struct mem_section_usage *usage; > +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP > + /* > + * Normally, sections hold regular (order-0) pages. However, for > + * sections with HVO enabled, this tracks the compound page order > + * to enable deduplication of redundant vmemmap pages. > + */ > + unsigned int order; order is a way too generic name for this. page_order? compound_page_order? -- Cheers, David