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 4D754C61DF4 for ; Fri, 24 Nov 2023 07:45:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CF75B8D0063; Fri, 24 Nov 2023 02:45:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CA6678D0002; Fri, 24 Nov 2023 02:45:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B96C78D0063; Fri, 24 Nov 2023 02:45:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id AC74E8D0002 for ; Fri, 24 Nov 2023 02:45:15 -0500 (EST) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 87964A0540 for ; Fri, 24 Nov 2023 07:45:15 +0000 (UTC) X-FDA: 81492062190.07.ED88E21 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf22.hostedemail.com (Postfix) with ESMTP id B1EC9C001D for ; Fri, 24 Nov 2023 07:45:12 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf22.hostedemail.com: domain of zhangpeng362@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=zhangpeng362@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1700811913; 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=gsElJToFBQqoUwxmFjo/mA9ZhlDnDhTgsvFZOCmX1Kc=; b=mBcQe9HDZNwfuNKg0dWSfl6wZcGPv6s3CYGk/fS1z7TzDF5nVLs8oOqI1l1ldYUhC+FM65 01tZ0KO95NNQ3Z9IzQVCDgeKD/i0DZYeRCVlikdiMwHVQN9hBIvz33I2laklTLtexurMGo n3nMuQrHXNMhjzFgdb2hZmfy+YuL1Hc= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf22.hostedemail.com: domain of zhangpeng362@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=zhangpeng362@huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700811913; a=rsa-sha256; cv=none; b=07wmgYZDmsBBN8gq8hgv7+l35Ob/6MxSOvqIVy4MgE/1mX6CspuV8xcUbfOtknz0uVVpFH b/Y/kmRUQEbIsKbvWRBcIgNtoTWcyfZXnx6PIM0ve54VQbkAPrjLXG+s/tICKH3LlTCnhN pQ3vwqR8tgOh3XK4PMnwfQcpPaxCcDY= Received: from kwepemm000020.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Sc5zw4ylCz1P8nL; Fri, 24 Nov 2023 15:23:08 +0800 (CST) Received: from [10.174.179.160] (10.174.179.160) by kwepemm000020.china.huawei.com (7.193.23.93) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Fri, 24 Nov 2023 15:26:39 +0800 Message-ID: <513144c1-c0e0-fe63-e133-c2611a440a94@huawei.com> Date: Fri, 24 Nov 2023 15:26:38 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [RFC PATCH] mm: filemap: avoid unnecessary major faults in filemap_fault() Content-Language: en-US To: "Huang, Ying" CC: , , , , , , , , , , References: <20231122140052.4092083-1-zhangpeng362@huawei.com> <87a5r4988r.fsf@yhuang6-desk2.ccr.corp.intel.com> From: "zhangpeng (AS)" In-Reply-To: <87a5r4988r.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.160] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm000020.china.huawei.com (7.193.23.93) X-CFilter-Loop: Reflected X-Rspam-User: X-Stat-Signature: arkw4cnjuczyztbapfmrfz17gpoahgp7 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B1EC9C001D X-HE-Tag: 1700811912-858594 X-HE-Meta: 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 XST4+uv4 pjI/wrW+TeS26nYVn0q0Hv7MCyZTpTGA+lR2TPwzg/BTrksCYt589OS3S5na6ULnmD+mvBx2Alg7VcRxArkaW0S4UB15C78GhdE1Cxn0vs2Vez9V7YolrthfhdXu9BzZ5Nssx26uGoXAi0SR1dKvzmdkFAFiQ+OxqGRPnRaIvhFFPz+RiqivCQliDDSSsESnLwjBG8TRoSEle144ILKI7brYddu8NoV5LujLii29K+/EDLxvNl5SGX6ZJswVWT6Olk7RnqKeZH9nPCIGg1ZUEkaHhx3wyXAMgCScjzCxSkInDs8FUn29nKyTCQg== 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: On 2023/11/23 16:36, Huang, Ying wrote: > Peng Zhang writes: > >> From: ZhangPeng >> >> The major fault occurred when using mlockall(MCL_CURRENT | MCL_FUTURE) >> in application, which leading to an unexpected performance issue[1]. >> >> This caused by temporarily cleared pte during a read/modify/write update >> of the pte, eg, do_numa_page()/change_pte_range(). >> >> For the data segment of the user-mode program, the global variable area >> is a private mapping. After the pagecache is loaded, the private anonymous >> page is generated after the COW is triggered. Mlockall can lock COW pages >> (anonymous pages), but the original file pages cannot be locked and may >> be reclaimed. If the global variable (private anon page) is accessed when >> vmf->pte is zeroed in numa fault, a file page fault will be triggered. >> >> At this time, the original private file page may have been reclaimed. >> If the page cache is not available at this time, a major fault will be >> triggered and the file will be read, causing additional overhead. >> >> Fix this by rechecking the pte by holding ptl in filemap_fault() before >> triggering a major fault. >> >> [1] https://lore.kernel.org/linux-mm/9e62fd9a-bee0-52bf-50a7-498fa17434ee@huawei.com/ >> >> Signed-off-by: ZhangPeng >> Signed-off-by: Kefeng Wang > Suggested-by: "Huang, Ying" > > :-) > >> --- >> mm/filemap.c | 14 ++++++++++++++ >> 1 file changed, 14 insertions(+) >> >> diff --git a/mm/filemap.c b/mm/filemap.c >> index 71f00539ac00..bb5e6a2790dc 100644 >> --- a/mm/filemap.c >> +++ b/mm/filemap.c >> @@ -3226,6 +3226,20 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) >> mapping_locked = true; >> } >> } else { >> + pte_t *ptep = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, >> + vmf->address, &vmf->ptl); >> + if (ptep) { >> + /* >> + * Recheck pte with ptl locked as the pte can be cleared >> + * temporarily during a read/modify/write update. >> + */ >> + if (unlikely(!pte_none(ptep_get(ptep)))) >> + ret = VM_FAULT_NOPAGE; >> + pte_unmap_unlock(ptep, vmf->ptl); >> + if (unlikely(ret)) >> + return ret; >> + } >> + > Need to deal with ptep == NULL. Although that is high impossible. Maybe we don't need to deal with ptep == NULL, because it has been considered later in filemap_fault()? ptep == NULL means that the ptep has been replaced with a PMD entry. In this case, major fault is also required. > -- > Best Regards, > Huang, Ying > >> /* No page in the page cache at all */ >> count_vm_event(PGMAJFAULT); >> count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); -- Best Regards, Peng