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 06AE3C982F1 for ; Tue, 22 Sep 2026 10:17:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AFF516B00A2; Tue, 22 Sep 2026 06:17:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AAEF16B00A4; Tue, 22 Sep 2026 06:17:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 99EEF6B00A5; Tue, 22 Sep 2026 06:17:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 6C6916B00A2 for ; Tue, 22 Sep 2026 06:17:37 -0400 (EDT) Received: from smtpin30.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id E10D1A638F for ; Tue, 22 Sep 2026 10:17:36 +0000 (UTC) X-FDA: 85240996512.30.08F4A47 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf08.hostedemail.com (Postfix) with ESMTP id 0EE5D16000F for ; Tue, 22 Sep 2026 10:17:34 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=CXRwwD9Z; spf=pass (imf08.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; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790072255; b=jYCZsiFQB3kpuR+BkW7Q3T0a0PEJC3f4y09hYTUvJW7+Xg/aScwn7qEY4YU9zlkn96sTDx NDaIVtrUT7NgUTM1msWZQXV20GvTTRF2xqMlOZ+f0R+BDryctQm+WE/EYlJGBoMyOldNMY +jCamoGhGnWEJMqUMgBjroZuzZcQQ+I= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=CXRwwD9Z; spf=pass (imf08.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=1790072255; 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=T5fauLT8ZuuY2ajM6FiAGbOvo57L73z/6qhgXvAWzLs=; b=BQxNno1BbZsv7h6TF2Cwbb1SNmIiG6CCh87eh/6k8tjNAINgxAM9irTDk496EGc6vqwkkD BaEW2ct1DiWNTzNASBJcO7zkri5WrNM9rMHQZvfKpjo4SyPhKYdxGw6+4VP2gQiRZMplbX wsceoVvEhSG8EkiU3HsieQVZ6j/SOYg= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 3E1A540046; Tue, 22 Sep 2026 10:17:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6624F1F000FF; Tue, 22 Sep 2026 10:17:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790072254; bh=T5fauLT8ZuuY2ajM6FiAGbOvo57L73z/6qhgXvAWzLs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=CXRwwD9ZL3yhrTkqxAeknomV92rLTDZpaQNiwJ+maRcLwpOjEIp3vAzfkJFYlpQF8 ly3ejSd/6IhagpAtdyOwKJPOJkbte+qSN7F6xkJ6V7y3jQRXOYmhQ9ccodDWrprsK3 8kmGCUDhx0Oxk6nsHx58vr+fblPEUYr4wYNzTxX493dnmE3esr6/nJk265S8od19Yb tnFtXnOsqZecQ8I4rAdrkAcnnxXFWHwLhqZT+gRLl2SQ4EkdKCGKxBHQvc8xK2DpGM 3bB8UavCRRjP9zqE4yxymE0zbIZkk++DCriWVXKoTX8TafrEIrFR9WeI9elfdGjGOv kKmhsJj7PY3Sg== Message-ID: Date: Tue, 22 Sep 2026 12:17:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory_hotplug: cache zone stats for "auto-movable" online policy To: Zhijian Han , Oscar Salvador , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260922082207.3224897-1-hanzhijian1991@gmail.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: <20260922082207.3224897-1-hanzhijian1991@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0EE5D16000F X-Stat-Signature: dn8cnedhzwrumwnfjdc1yipsquorrkzj X-HE-Tag: 1790072254-140618 X-HE-Meta: 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 py1Pcy45 b/PnoMBwB2WG+PAWCVQ7JMEcrfco+bTGORaWajaVapljzNSHPwAb6nlPeNv1w/kU7e/NKIeisVWzmQ5ZUsox47aTylUN0M5Zi4dxj7TtZwO5wAb9eD0VWl4XmucIYLQN3fCsheuEHKaQbX+uSQJKzjNYYhUAxDO/jEkYgacx+i8ZS6qBgYr3uHCSvIgEcG2XLStkLqoiD3vngqCeZTlpzKotlQX8ewuhmZyt3s3kf8sRi1TkAUcbz2XfTXv1q/0nZKCXaA9il+waAwZuKEswHBCjgarWO0pT4FFZ31xNyi6OtGTZ1VWbjAlbwbsoobKtyO6p+XhmwC9VxSJcPHPxs32jRBj0IuRI0IuJ5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/22/26 10:22, Zhijian Han wrote: > When onlining memory using the "auto-movable" online policy with > nid == NUMA_NO_NODE, auto_movable_can_online_movable() walks all > populated zones across all nodes on each invocation to collect the > MOVABLE vs. KERNEL_EARLY stats. This walk happens twice for every > memory block onlining decision (global check and, with NUMA awareness > enabled, per-node check) and is repeated for every single memory block > that gets onlined, although the underlying zone counters rarely change. > > Cache the stats for nid == NUMA_NO_NODE and only recalculate them when > a zone counter actually changes. All modifications of the relevant > zone counters (present_pages, present_early_pages) funnel through > adjust_present_page_count(), which is only called while holding the > mem_hotplug_lock in write mode and the device_lock() of the memory > block device. Invalidate the cache there, such that the next > auto-movable onlining decision recalculates the stats from scratch. > > CMA adjustments (zone->cma_pages) only happen during boot (via > init_cma_reserved_pageblock()/init_cma_pageblock(), both __init) and > cannot race with memory onlining. Boot-time zone initialization > happens before any memory block can be onlined. > > The per-node path (nid != NUMA_NO_NODE) is left uncached; it only > walks a single node's zones. > > Resolve a TODO that was left when the "auto-movable" online policy was > introduced. I have to ask 1) Why is this TODO a concern for you. Are you a frequent memory hotplug user or somehow working on memory hotplug. 2) Did you use an LLM to come up with this idea or this patch. 3) Why is there no discussion / performance measurements whether the TODO should be removed instead. I'll point you at: https://lore.kernel.org/linux-mm/20251206212507.135503-1-swarajgaikwad1925@gmail.com/ -- Cheers, David