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 420A2FEC118 for ; Tue, 24 Mar 2026 20:56:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 33AFF6B0005; Tue, 24 Mar 2026 16:56:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2EC7D6B0088; Tue, 24 Mar 2026 16:56:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1DACF6B008A; Tue, 24 Mar 2026 16:56:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 0B3D66B0005 for ; Tue, 24 Mar 2026 16:56:52 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 7F50EB931B for ; Tue, 24 Mar 2026 20:56:51 +0000 (UTC) X-FDA: 84582165822.04.2CA65AB Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf14.hostedemail.com (Postfix) with ESMTP id C25D2100007 for ; Tue, 24 Mar 2026 20:56:49 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=f6Poctri; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774385809; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to: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=UEM1kwWQ+mF9wiFGAPSZEFY5LYihg214naVwgduLaRc=; b=3dztz5I8FWH1fS85b4UTHvWeDxFwJxmloQO7v9+2jFBPOTYDOqpJxso6GBHJZ64Q+/hWnT AZjy1VXFzJacJfZB+JXaqERSI7NIGQXDG832nqm7cjyA1xjdm6l1eHseuH6Mv9q543QYLD OOfDyJowLpOQzhUP2kP7znOBQ1RdD+o= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774385809; a=rsa-sha256; cv=none; b=b7UdZdYdQulWSa1B5ia9G792BSrExWg1RxVG4tfM+/4BtGtEavYZ5H+Mp8coofQb5n2ij1 cypsHVkKxFdSrFSKF7HrB5hVSwAdK5Ah/Ns6FCpopwkO5KHG7CePczMOABI3oHi5d53ZCm HxxlnYZDpk/M1xYUsRl+Rf8UUZOcIJU= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=f6Poctri; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1571260120; Tue, 24 Mar 2026 20:56:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92E48C2BC9E; Tue, 24 Mar 2026 20:56:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774385808; bh=Qo+ZovdrQkA7kuzporo2AYwDS9G8g8sICjIZiGOAKnU=; h=Date:Subject:To:References:From:In-Reply-To:From; b=f6PoctrisWs98te5iO4xZq2aMrivny/ZTKH1g6lAJVKqCu4up5Jcvk5+KYY6nHk9F 3qCodf23wxz+kbD9cCp2cSubZ/Dy+JrdOV4sDjqhCCPXva93kN/UIDxXcj1+Db/FEp FEmZcQTFAlb5JRMgUG8NJPTDz42ABtcAg7LK7zAaAvQZ/UuqKh29rEgunQIRzjuGIf ewfpTCdIBi0YDqg/wD+dAHAtbj5IqsB3x2klBeK6+2V4vAIUXkRCGm0n6VbF1+BN0J bMwciUWDai06Dzyf4612pObXLHKPJvtn+VUkp2h/8Wss0jNMqxah5nUeiCrMHwkv0o IMHTkGc+zl8og== Message-ID: Date: Tue, 24 Mar 2026 21:56:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] mm/page_alloc: Optimize free_contig_range() To: Muhammad Usama Anjum , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Uladzislau Rezki , Nick Terrell , David Sterba , Vishal Moola , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com References: <20260324133538.497616-1-usama.anjum@arm.com> <20260324133538.497616-2-usama.anjum@arm.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: <20260324133538.497616-2-usama.anjum@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C25D2100007 X-Stat-Signature: kofphoj5eoiu6ahhetparan6s3ijs14c X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1774385809-129909 X-HE-Meta: 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 a+7xwVaY DXCKE/J/9j6NxOYxekOneobqNI+kyYgUC4pl7IKzFMgwLfs86AoEP0exZS0MLrANBFjEo/X8L2Vo3CVd1yRG5Qlc6xk9DXvj0obZzt+rLlwyaPjVuJet2hFZYyhjK65RkSKkRaFeU3SDObhZDeHpFr6oaSu+2McqvxpohjPrBXMybwvZpweJFvauA3I+SbP6zcVVuVc6KnVWA+1DtA+nhp4iYwrRGR5ZOej9WZdKryZXtudrcwfIqyJEICzlTcCsb7AqNTyWQYxg10tJUCMENw2rR49HdYt1o/BQVsq2eJ8gMB8cu0q7i1wwkpN3IQBeIjJQQUPun+5k+XOywgmiYypJC+2eFBPFPBOngunB3srO3JSSL4wpwrFBKSfmVzOipNYDE Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > +void __free_contig_range(unsigned long pfn, unsigned long nr_pages) > +{ > + struct page *page = pfn_to_page(pfn); > + struct page *start = NULL; > + unsigned long start_sec; > + unsigned long i; > + bool can_free; > + > + /* > + * Chunk the range into contiguous runs of pages for which the refcount > + * went to zero and for which free_pages_prepare() succeeded. If > + * free_pages_prepare() fails we consider the page to have been freed; > + * deliberately leak it. > + * > + * Code assumes contiguous PFNs have contiguous struct pages, but not > + * vice versa. Break batches at section boundaries since pages from > + * different sections must not be coalesced into a single high-order > + * block. The comment is not completely accurate: section boundary only applies to some kernel configs. Maybe rewrite the whole paragraph into "Contiguous PFNs might not have a contiguous "struct pages" in some kernel config. Therefore, check memdesc_section(), and stop batching once it changes, see num_pages_contiguous()." > + */ > + for (i = 0; i < nr_pages; i++, page++) { > + VM_WARN_ON_ONCE(PageHead(page)); > + VM_WARN_ON_ONCE(PageTail(page)); > + > + can_free = put_page_testzero(page); > + if (can_free && !free_pages_prepare(page, 0)) > + can_free = false; > + > + if (can_free && start && > + memdesc_section(page->flags) != start_sec) { > + free_prepared_contig_range(start, page - start); > + start = page; > + start_sec = memdesc_section(page->flags); > + } else if (!can_free && start) { > + free_prepared_contig_range(start, page - start); > + start = NULL; > + } else if (can_free && !start) { > + start = page; > + start_sec = memdesc_section(page->flags); > + } > + } Simplification a proposed by Zi make sense to me! -- Cheers, David