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 70DDCC982FA for ; Tue, 22 Sep 2026 12:51:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 762816B00AF; Tue, 22 Sep 2026 08:51:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 739E36B00B0; Tue, 22 Sep 2026 08:51:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 676E66B00B1; Tue, 22 Sep 2026 08:51:50 -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 451C66B00AF for ; Tue, 22 Sep 2026 08:51:50 -0400 (EDT) Received: from smtpin03.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id CC0EE4034B for ; Tue, 22 Sep 2026 12:51:49 +0000 (UTC) X-FDA: 85241385138.03.7E30CD6 Received: from mail-ed2-f35.google.com (mail-ed2-f35.google.com [74.125.228.99]) by imf23.hostedemail.com (Postfix) with ESMTP id E57B7140004 for ; Tue, 22 Sep 2026 12:51:47 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=jznpxOnR; spf=pass (imf23.hostedemail.com: domain of richard.weiyang@gmail.com designates 74.125.228.99 as permitted sender) smtp.mailfrom=richard.weiyang@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790081507; h=from:from:sender:reply-to: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=G0pT1Bz/Ukk2yKj9z6fcgefhEfOADcNNQjef2vknbn4=; b=OI5dwT/oV9JhojkdCryXPe3q0zD7S2WDSBMuJxxynm2n58PpW1yPoFnr5007JXyXZxyIAJ YRuMaPs0rXG8dLXQe302+F0Tv3rYzv4ED5bNPAfYJxjZe0zSoyty/4U55Vl5dI6s7tuxeP HvChTAF+MlYs883hOEYizXzMvsA26sg= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=jznpxOnR; spf=pass (imf23.hostedemail.com: domain of richard.weiyang@gmail.com designates 74.125.228.99 as permitted sender) smtp.mailfrom=richard.weiyang@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790081507; b=TrgfcDf1GihWjmKS5ZOxdC6klSlnePLQmnlyyPLhXitamUYKfeaxBSRklkix47u5ZdXZiU DOZqJh6jN2uMFfo306RJNaHFdzBurt44Gvp25jkMP9cuH7cKj6mYsjO17O/SqdQOdQkcEN +WgGhROPk85L3BstjDJzuw+pukZ0VH0= Received: by mail-ed2-f35.google.com with SMTP id 4fb4d7f45d1cf-6aa1d00daaaso7104846a12.1 for ; Tue, 22 Sep 2026 05:51:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790081506; x=1790686306; darn=kvack.org; h=user-agent:in-reply-to:content-disposition:content-type :mime-version:references:reply-to:message-id:subject:cc:to:from:date :from:to:cc:subject:date:message-id:reply-to:content-type; bh=G0pT1Bz/Ukk2yKj9z6fcgefhEfOADcNNQjef2vknbn4=; b=jznpxOnRqtX1zP4w916A93xuXJuGa1LnKXRnhNp9GeC3E6IHmhVkPCREiQ3NACVb8V hrCShUwQigKpeVhaNP1iJBcSc8sM+IzWklvknwWc9B/kqBafwx3W+NP35Vg3wC8CMy9J eSEX9hF0Laka1bzRAebikfH9FrTyrzyMHSOJYYxbJzqSLjFWTSxWA9HS7AjqhvmfI4Vh NBLIfGXUeT6t+4Q220vN1zBQ/elMmM2ctsLalhYmiiAfUjWS+5w91mkwsFJ1XpoAd/Ru eBWW6ZxoORBvcsbJiVRZTd8NJjK+yIScnuXHoTJ/LWfSkgMqrlzk5zp0RpPPp7mlhRPf kqXA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790081506; x=1790686306; h=user-agent:in-reply-to:content-disposition:content-type :mime-version:references:reply-to:message-id:subject:cc:to:from:date :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=G0pT1Bz/Ukk2yKj9z6fcgefhEfOADcNNQjef2vknbn4=; b=gIMtKK0wp/wXYOMoCZGK6ItWAjOfAMy0CegANEeAPZBGDeLhDGbBLnMlEQAwul6AqP xOgJQCEIR43Xpl+EOVhBm0UDZRfnejrzTiMD6XJLaVdfO37JbmnV/J2l/8j8JkXGxOl4 WiB64qCPu/GRufu1xRXHd58a8nFZXKKcKtsx/EnG8ArG7+igoL6uIhb18GFDQwN1MnR9 7rB5jYbrCjJh7/AmVltKXDhI/9Ybf+wm8U20i0JmaUrwdHUkCFIFpEwMbhz23oXVsd/I k+VKVFFLZmd50XiU2+ELRZYhJZbpC71dZ2RbFm+qbdZVxgGl/GaQzKKOtyazGd7hk71M q2mQ== X-Forwarded-Encrypted: i=1; AKwUvBzNwez7ISY0gmkQ8JNTQjUcFpdaE0nRYTmg8nOijlUrFY9YRgRPDtq49Rdn/PXj0wTFM8uplEo1DQ==@kvack.org X-Gm-Message-State: AFuF++kGBWnXOCvmaDGYC+pIWhf+0t+RiZMw3c3zhCtp+mfOmS8Y8sf8 w2euq84LaLhSSjONCfsAIhNCfguOw5WSNxB/lqqvSn0PmDrWcyyNYMvD X-Gm-Gg: AYBFou1zP94qq7iW4H/1ubG6410LqGl2RfOst3WyaFO2hC4m9DnnT7ROnarTWdlOOYa MTAfdLus6cw0DFFLz/Z8m5nsvTamvUWKGbE6V/hlEtqOIpy+bQ+6NHGzSRgKyNfI2hO5OOhsndB AdO5ih9SgrmtOxV3AwfIO5m6Q2rFL9cibtFwUpJX2NdyfAKP+lOIlsy0vGye1O9BnEr0A1ZA6sC LavcGaqeyqsZe6yNty2qt1Lez8AHMvraK9mn7OykiQEtbLRJPRBQSaFhkY0SSr95GgIy4zzh6pU Sn/ijGhV6MJFkkcnmpg2NMvQJM3MlvBs6tOaugOA31VsYYf+saAZyWqR8XeywHbKtbKTDAawgRT F3SyWUUXqbsLs4QSLRhcvQ7K0+zgTjnHkRy+tBwLSnHjPbXUSdeUu3kOOeRhAAK4g1CxVFLjknI Yw545kxZrQt2yclbumWSRW7ubgOz/WCge8pSP2Nc5PHJgz6UbnoNgjMePH/dPluMR+J5Og X-Received: by 2002:a05:6402:1d4f:b0:6aa:9823:218a with SMTP id 4fb4d7f45d1cf-6aa982324cfmr3582241a12.31.1790081506095; Tue, 22 Sep 2026 05:51:46 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6aaa4537b5dsm1073668a12.30.2026.09.22.05.51.45 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 22 Sep 2026 05:51:45 -0700 (PDT) Date: Tue, 22 Sep 2026 12:51:45 +0000 From: Wei Yang To: Yuan Liu Cc: David Hildenbrand , Oscar Salvador , Mike Rapoport , Wei Yang , linux-mm@kvack.org, Nanhai Zou , Chen Zhang , Jason Zeng , Chen Yu , Pan Deng , Tianyou Li , linux-kernel@vger.kernel.org Subject: Re: [PATCH v10 2/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range Message-ID: <20260922125145.3fygpy7gxoztsa3n@master> Reply-To: Wei Yang References: <20260920084946.3266279-1-yuan1.liu@intel.com> <20260920084946.3266279-3-yuan1.liu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260920084946.3266279-3-yuan1.liu@intel.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E57B7140004 X-Stat-Signature: 5jtmdi6bcrt6a17biwknxx5frwwyguok X-Rspam-User: X-HE-Tag: 1790081507-987937 X-HE-Meta: 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 jOZmdJLt 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Sep 20, 2026 at 04:49:46AM -0400, 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 and for which pfn_to_online_page() succeeds. > >For early boot memory, pages_with_online_memmap is calculated in >memmap_init_zone_range(). PFNs initialized by memmap_init_range() are >included in pages_with_online_memmap, and hole PFNs for which >pfn_to_online_page() succeeds are also counted in >init_unavailable_range(). For hotplugged memory, >pages_with_online_memmap is updated through adjust_present_page_count(), >which is called during memory online and offline operations. When >spanned_pages == pages_with_online_memmap, every PFN in the zone span >has a valid memmap entry, so pfn_to_page() can be called for any PFN >within the zone span without an additional pfn_valid() check. > >Note: this counter may temporarily undercount when pages with an >online memory map exist outside the current zone span. Such pages >are only created during boot, when initializing the memory map of >pages that do not fall into any zone span. The undercount itself >can only happen after boot, during memory hotplug, when growing >the zone to cover such pages and later shrinking it back, which >may result in a "too small" value. This is safe: it merely >prevents detecting a contiguous zone. > >Here is an example (page numbers are just for illustration purposes): > after boot: > [ zone span ] > [ zone pages ] > spanned=10, initialized=15, online=10 > online == spanned -> contiguous > > growing after hotplug (hotplug 5): > [ zone span ] > [ zone pages ] [ zone pages ] > spanned=30, initialized=20, online=15 > online != spanned -> not contiguous > > shrinking after hotunplug (hotunplug 5 again): > [ zone span ] > [ zone pages ] > spanned=15, initialized=15, online=10 > online != spanned -> not contiguous although contiguous > >The contiguity check using pages_with_online_memmap is stricter than >the old pageblock-by-pageblock scan. The old set_zone_contiguous() >iterated at pageblock granularity via pageblock_pfn_to_page(), so a >zone could be marked contiguous even if a subsection-sized hole >existed within a pageblock. The new check requires >spanned_pages == pages_with_online_memmap, meaning every PFN in the >zone span must satisfy pfn_to_online_page(). > >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 : v7.3-rc3 > 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: Jason Zeng >Reviewed-by: Chen Yu >Reviewed-by: Pan Deng >Co-developed-by: Tianyou Li >Signed-off-by: Tianyou Li >Signed-off-by: Yuan Liu >Acked-by: Mike Rapoport (Microsoft) LGTM, thanks for the effort. Reviewed-by: Wei Yang -- Wei Yang Help you, Help me