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]) by smtp.lore.kernel.org (Postfix) with ESMTP id E68C2C19F32 for ; Wed, 5 Mar 2025 03:46:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7CC016B0089; Tue, 4 Mar 2025 22:46:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 77BC86B008A; Tue, 4 Mar 2025 22:46:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 66B196B008C; Tue, 4 Mar 2025 22:46:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 4A1206B0089 for ; Tue, 4 Mar 2025 22:46:26 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id DA092C0A78 for ; Wed, 5 Mar 2025 03:46:25 +0000 (UTC) X-FDA: 83186109930.01.E51F26E Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) by imf05.hostedemail.com (Postfix) with ESMTP id B702F100003 for ; Wed, 5 Mar 2025 03:46:21 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf05.hostedemail.com: domain of tujinjiang@huawei.com designates 45.249.212.35 as permitted sender) smtp.mailfrom=tujinjiang@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1741146384; 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; bh=o7i4FhB+bDj2Gw0XD944AnIG5jRGdO5N0fLhiqvWxbU=; b=WunZxUCZ4u7H5OvVl+xKcSEiEGdNCOBUiaa0Z/eDzTzpUlc/A70Ffx73BFoU6bpF1exeV5 v16ELLHs30E/n8056EZjrZ+SitOMOl4CmMHHCaenKTdNPuxnBuMPP+KnNGdAehvztFheko EmwqBi7zbB3MHaEjYlgYXcCkgEWn9cw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1741146384; a=rsa-sha256; cv=none; b=OycdgAA18PowMpDSozV5KIZ7BQ0zn1MZuLmi9iMLKF6xfljluLBeFMBjGUCHp5qnxUtYbD HlFe4/XkCiqTejm9HJSUpSnYakl2vj7nNkFB8HfgpcCmkEj0IhiPNQq6BaTpciJ5hz8X11 hCV5/5ltxGf2Et0PK8sO2X0Q0lFfKi4= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf05.hostedemail.com: domain of tujinjiang@huawei.com designates 45.249.212.35 as permitted sender) smtp.mailfrom=tujinjiang@huawei.com Received: from mail.maildlp.com (unknown [172.19.88.214]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4Z6yzJ3gCRz1f051; Wed, 5 Mar 2025 11:42:04 +0800 (CST) Received: from kwepemo200002.china.huawei.com (unknown [7.202.195.209]) by mail.maildlp.com (Postfix) with ESMTPS id 5CE2D1A016C; Wed, 5 Mar 2025 11:46:17 +0800 (CST) Received: from [10.174.179.13] (10.174.179.13) by kwepemo200002.china.huawei.com (7.202.195.209) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 5 Mar 2025 11:46:16 +0800 Message-ID: <932dde6f-06a0-121d-584c-256e74ebadb9@huawei.com> Date: Wed, 5 Mar 2025 11:46:15 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v2] mm/hugetlb: fix surplus pages in dissolve_free_huge_page() To: Oscar Salvador CC: , , , , , References: <20250304132106.2872754-1-tujinjiang@huawei.com> From: Jinjiang Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.13] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemo200002.china.huawei.com (7.202.195.209) X-Stat-Signature: 9yjntm9pagnd9yboh3zeex3teftix9z5 X-Rspamd-Queue-Id: B702F100003 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1741146381-590244 X-HE-Meta: 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 aI47g7sl VYHZ6x/xCNZ7DolLxGLJOT4cDMr62VvE/HdO/9VNQxEttqB6DlNYfdtiOScQc0fooJgf69dYYOzzfM1ye6ijtGJJRcqpFRaec3IXvqAdhavFF+LS2XoebqkXkVctReBg3pSESlJTm1mb4P15aSzIxH0sPOmd6uNr3Qzeg5IykGKn7RBFmwS85DLqw+UAWGVw+LajFwSXummF5THO3mrGpVdO+tITUceV6evy4E12doBomgRzku4piJo+3Xg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2025/3/4 21:43, Oscar Salvador 写道: > On Tue, Mar 04, 2025 at 09:21:06PM +0800, Jinjiang Tu wrote: >> In dissolve_free_huge_page(), free huge pages are dissolved without >> adjusting surplus count. However, free huge pages may be accounted as >> surplus pages, and will lead to wrong surplus count. >> >> I reproduce this issue on qemu. The steps are: >> 1) Node1 is memory-less at first. Hot-add memory to node1 by executing >> the two commands in qemu monitor: >> object_add memory-backend-ram,id=mem1,size=1G >> device_add pc-dimm,id=dimm1,memdev=mem1,node=1 >> 2) online one memory block of Node1 with： >> echo online_movable > /sys/devices/system/node/node1/memoryX/state >> 3) create 64 huge pages for node1 >> 4) run a program to reserve (don't consume) all the huge pages >> 5) echo 0 > nr_huge_pages for node1. After this step, free huge pages in >> Node1 are surplus. >> 6) create 80 huge pages for node0 >> 7) offline memory of node1, The memory range to offline contains the free >> surplus huge pages created in step3) ~ step5) >> echo offline > /sys/devices/system/node/node1/memoryX/state >> 8) kill the program in step 4) >> >> The result: >> Node0 Node1 >> total 80 0 >> free 80 0 >> surplus 0 61 >> >> To fix it, adjust surplus when destroying huge pages if the node has >> surplus pages in dissolve_free_hugetlb_folio(). >> >> The result with this patch: >> Node0 Node1 >> total 80 0 >> free 80 0 >> surplus 0 0 >> >> Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") >> Acked-by: David Hildenbrand >> Signed-off-by: Jinjiang Tu > Acked-by: Oscar Salvador > >> @@ -2157,7 +2159,9 @@ int dissolve_free_hugetlb_folio(struct folio *folio) >> goto retry; >> } >> >> - remove_hugetlb_folio(h, folio, false); >> + if (h->surplus_huge_pages_node[folio_nid(folio)]) >> + adjust_surplus = true; >> + remove_hugetlb_folio(h, folio, adjust_surplus); >> h->max_huge_pages--; >> spin_unlock_irq(&hugetlb_lock); >> >> @@ -2177,7 +2181,7 @@ int dissolve_free_hugetlb_folio(struct folio *folio) >> rc = hugetlb_vmemmap_restore_folio(h, folio); >> if (rc) { >> spin_lock_irq(&hugetlb_lock); >> - add_hugetlb_folio(h, folio, false); >> + add_hugetlb_folio(h, folio, adjust_surplus); > I was about to point this out, but checking v1 I saw that David already > that. > My alternative would have been to just get rid of the adjust_surplus > boolean and to the checking right within the lock cycle e.g: > > if (h->surplus_huge_pages_node[folio_nid(folio)]) > add_hugetlb_folio(h, folio, true); > else > add_hugetlb_folio(h, folio, false); It seems wrong to fix like this. h->surplus_huge_pages_node[folio_nid(folio)] !=0 means existing surplus pages after removing folio (the variable named folio), doesn't mean if the folio need to be treated as surplus too. > But I guess that's fine as you already explained. > > >