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 81EFBFD5F91 for ; Wed, 8 Apr 2026 07:36:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9C1BD6B0088; Wed, 8 Apr 2026 03:36:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 973396B0089; Wed, 8 Apr 2026 03:36:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 861736B008A; Wed, 8 Apr 2026 03:36:22 -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 77F5E6B0088 for ; Wed, 8 Apr 2026 03:36:22 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 1734A160A45 for ; Wed, 8 Apr 2026 07:36:22 +0000 (UTC) X-FDA: 84634580604.02.D75E633 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf02.hostedemail.com (Postfix) with ESMTP id 0C7DB8000D for ; Wed, 8 Apr 2026 07:36:19 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=nBN6TY5G; spf=pass (imf02.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=1775633780; 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=NHBxpCe8VwSq3CDbulhrrdaBqwIRC/vJocbp0QUE9l0=; b=coQfXwzsDo0bUKQ8ykCzGl3Rm6rba3+/9ubEQMAMOpOz9C8eepE5bYCvab8DqhouR3D0f4 SdI9JajcjAqZXLmlzjOmylIaxH9BEuZNRaLmWFVO0PHn7yj/a3HdFgXqkE019febPgPXSE 7ghKrsZKj1bcbxGaB6ErC40lA588FoM= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=nBN6TY5G; spf=pass (imf02.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-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1775633780; a=rsa-sha256; cv=none; b=qNpxTnr/bYmPOFLkGeOY8qza2rY4Nlmg+BW26STWsCvU314CYwlUWCbvZ0DMR//9UHh18c ng+hazaAtdsZ7IvVBsYlsopRhcDtoAXQ+TY8Tvh4/9Y/a3E1qO1JdNaOUUFfsXf6TPrXPw WrDNbxS4OrgsBYP4KR5tIWbOAzvTM6A= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 082CB433B3; Wed, 8 Apr 2026 07:36:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 358E3C2BCB0; Wed, 8 Apr 2026 07:36:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775633778; bh=9usUKozMxTM5/KPBGhFL/Q5Q+WRhnI82yaR3J4yHm9A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=nBN6TY5GLLWEq3U7h/9ZirccALW3l4Tx4ivhOSx0sUKHGA1kyxKWjil3vxw8CK7gz yf2xzlKeYUJE2n/u08fy7XYLgX2ZBHpzeQxy4h0c77nWZVYQvDc6naZandP5Sw6m6b 8G9WHeVeNCxTVeT4FX7uNn7Ff1JEhX/9T6K2Kmmdy1CGD1Ku7FjSDuCwncxORKyg4e /9TiGZ/AxuGYiZ+i81To3jOOGzRkWUs7ybxqkYExRifwGqkjomQou1PqeXGRR4wtgE WMR1WF2XYtJeGlsYVfOrqTplvmhEXjc95oPGAu1xNYXtDNcmaTj3f229tLgjytv4L8 UI0J61zg01uaQ== Message-ID: <17b821b6-0176-43d5-92f7-fe2a0c4f70cf@kernel.org> Date: Wed, 8 Apr 2026 09:36:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/memory hotplug/unplug: Optimize zone contiguous check when changing pfn range To: Yuan Liu , Oscar Salvador , Mike Rapoport , Wei Yang Cc: linux-mm@kvack.org, Yong Hu , Nanhai Zou , Tim Chen , Qiuxu Zhuo , Yu C Chen , Pan Deng , Tianyou Li , Chen Zhang , linux-kernel@vger.kernel.org References: <20260408031615.1831922-1-yuan1.liu@intel.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: <20260408031615.1831922-1-yuan1.liu@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 0C7DB8000D X-Stat-Signature: x9xgqgcf7hm4eau8ysmmh6khqcbtpjcr X-Rspamd-Server: rspam06 X-HE-Tag: 1775633779-744893 X-HE-Meta: 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 Ekg7hQrb zFFd+fcW2LA8SLTZYwnyAAUTlxTQiR7E9wHTvhDGbfLRFgHGfKSaU/PeJf3aB26bKZHdMdRHraDxULPg9jMGULpE8MHwokaaO8CpBqex530HpWtkZkDvvPc5IjM8R9HtR1/M1xWdJ83RucMAlp34et2D0PY84VZwOuAadfH883U0NPzpdvp6CtSjosovIHbiMU5S5BnqQrQPaZzU4g23fNvsTsrAG1PxYqw0HjHT4yztn92BSBOQZ5x+WASSLA6cyMj3MahgWCmF8Q8Xx/v8b1N85rWmiw5znWX3TjpvT3+qbUKfZYyp5DEHy9Cujslvt0+VBcx8jKUh4pr4ez/Jdz6xZvKbcoqsxqF0xLkGI954HDN+oxcg+lECihMCCOttFj/C/O1SdK/+ix7EPjJWhXWn7RQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/8/26 05:16, Yuan Liu wrote: > When move_pfn_range_to_zone() or remove_pfn_range_from_zone() updates a > zone, set_zone_contiguous() rescans the entire zone pageblock-by-pageblock > to rebuild zone->contiguous. For large zones this is a significant cost > during memory hotplug and hot-unplug. > > Add a new zone member pages_with_online_memmap that tracks the number of > pages within the zone span that have an online memory map (including present > pages and memory holes whose memory map has been initialized). When > spanned_pages == pages_with_online_memmap the zone is contiguous and > pfn_to_page() can be called on any PFN in the zone span without further > pfn_valid() checks. > > Only pages that fall within the current zone span are accounted towards > pages_with_online_memmap. A "too small" value is safe, it merely prevents > detecting a contiguous zone. > > The following test cases of memory hotplug for a VM [1], tested in the > environment [2], show that this optimization can significantly reduce the > memory hotplug time [3]. > > +----------------+------+---------------+--------------+----------------+ > | | Size | Time (before) | Time (after) | Time Reduction | > | +------+---------------+--------------+----------------+ > | Plug Memory | 256G | 10s | 3s | 70% | > | +------+---------------+--------------+----------------+ > | | 512G | 36s | 7s | 81% | > +----------------+------+---------------+--------------+----------------+ > > +----------------+------+---------------+--------------+----------------+ > | | Size | Time (before) | Time (after) | Time Reduction | > | +------+---------------+--------------+----------------+ > | Unplug Memory | 256G | 11s | 4s | 64% | > | +------+---------------+--------------+----------------+ > | | 512G | 36s | 9s | 75% | > +----------------+------+---------------+--------------+----------------+ > > [1] Qemu commands to hotplug 256G/512G memory for a VM: > object_add memory-backend-ram,id=hotmem0,size=256G/512G,share=on > device_add virtio-mem-pci,id=vmem1,memdev=hotmem0,bus=port1 > qom-set vmem1 requested-size 256G/512G (Plug Memory) > qom-set vmem1 requested-size 0G (Unplug Memory) > > [2] Hardware : Intel Icelake server > Guest Kernel : v7.0-rc4 > Qemu : v9.0.0 > > Launch VM : > qemu-system-x86_64 -accel kvm -cpu host \ > -drive file=./Centos10_cloud.qcow2,format=qcow2,if=virtio \ > -drive file=./seed.img,format=raw,if=virtio \ > -smp 3,cores=3,threads=1,sockets=1,maxcpus=3 \ > -m 2G,slots=10,maxmem=2052472M \ > -device pcie-root-port,id=port1,bus=pcie.0,slot=1,multifunction=on \ > -device pcie-root-port,id=port2,bus=pcie.0,slot=2 \ > -nographic -machine q35 \ > -nic user,hostfwd=tcp::3000-:22 > > Guest kernel auto-onlines newly added memory blocks: > echo online > /sys/devices/system/memory/auto_online_blocks > > [3] The time from typing the QEMU commands in [1] to when the output of > 'grep MemTotal /proc/meminfo' on Guest reflects that all hotplugged > memory is recognized. > > Reported-by: Nanhai Zou > Reported-by: Chen Zhang > Tested-by: Yuan Liu > Reviewed-by: Tim Chen > Reviewed-by: Qiuxu Zhuo > Reviewed-by: Yu C Chen > Reviewed-by: Pan Deng > Reviewed-by: Nanhai Zou > Co-developed-by: Tianyou Li > Signed-off-by: Tianyou Li > Signed-off-by: Yuan Liu > Acked-by: David Hildenbrand (Arm) > --- [...] > @@ -842,7 +842,7 @@ overlap_memmap_init(unsigned long zone, unsigned long *pfn) > * zone/node above the hole except for the trailing pages in the last > * section that will be appended to the zone/node below. > */ > -static void __init init_unavailable_range(unsigned long spfn, > +static unsigned long __init init_unavailable_range(unsigned long spfn, > unsigned long epfn, > int zone, int node) > { > @@ -858,6 +858,7 @@ static void __init init_unavailable_range(unsigned long spfn, > if (pgcnt) > pr_info("On node %d, zone %s: %lld pages in unavailable ranges\n", > node, zone_names[zone], pgcnt); > + return pgcnt; > } > > /* > @@ -956,9 +957,22 @@ static void __init memmap_init_zone_range(struct zone *zone, > memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn, > zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE, > false); > + zone->pages_with_online_memmap += end_pfn - start_pfn; > > - if (*hole_pfn < start_pfn) > - init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid); > + if (*hole_pfn < start_pfn) { > + unsigned long pgcnt; > + > + if (*hole_pfn < zone_start_pfn) { > + init_unavailable_range(*hole_pfn, zone_start_pfn, > + zone_id, nid); > + pgcnt = init_unavailable_range(zone_start_pfn, > + start_pfn, zone_id, nid); Indentation of parameters. > + } else { > + pgcnt = init_unavailable_range(*hole_pfn, start_pfn, > + zone_id, nid); Same here. > + } > + zone->pages_with_online_memmap += pgcnt; > + } Maybe something like the following could make it nicer to read, just a thought. unsigned long hole_start_pfn = *hole_pfn; if (hole_start_pfn < zone_start_pfn) { init_unavailable_range(hole_start_pfn, zone_start_pfn, zone_id, nid); hole_start_pfn = zone_start_pfn; } pgcnt = init_unavailable_range(hole_start_pfn, start_pfn, zone_id, nid); LGTM, thanks! -- Cheers, David