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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A62DC0650F for ; Tue, 30 Jul 2019 18:40:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2FACB20693 for ; Tue, 30 Jul 2019 18:40:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="RLGTbz1o"; dkim=pass (1024-bit key) header.d=fb.onmicrosoft.com header.i=@fb.onmicrosoft.com header.b="Ep3U/KS3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2FACB20693 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=fb.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9A1DA8E0003; Tue, 30 Jul 2019 14:40:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9799D8E0001; Tue, 30 Jul 2019 14:40:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F33B8E0003; Tue, 30 Jul 2019 14:40:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by kanga.kvack.org (Postfix) with ESMTP id 2B0AD8E0001 for ; Tue, 30 Jul 2019 14:40:01 -0400 (EDT) Received: by mail-wr1-f72.google.com with SMTP id u5so32283465wrp.10 for ; Tue, 30 Jul 2019 11:40:01 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:dkim-signature:from:to:cc:subject :thread-topic:thread-index:date:message-id:references:in-reply-to :accept-language:content-language:content-id :content-transfer-encoding:mime-version; bh=AUwSPm4smgaC06dcO2BrmAUXjLSZek9Pxdr2qqWzQb8=; b=qCAXJHUFAV442hIMAjcssOLUNg5SYasOKLwQ92tHo+H4QQmlYXxaON+olKy1u4yMv+ C8J6BDMBCyO1ktERoIm7T3E9mzg3TSnqrkk4wuBH5FVdbYxZgIJ6y2DsY9u6lJXBWdLr L/ny3UbgS6jYvbBn0rdybjC7e8DIcDPqeTlrbseJOGPx0lL6PlqOwC6oHizE1mxHnhT0 pmYu3iMUpdWbveIB3gwge5exMmqELdplsFPYf0Vv5NuimYvmCl28URqmL0dZ6Twi2e4q TwBiNybWm3EtN7BGmawgecI0pscaTWGJZX4JCb+y/A40dibn8eWhIVbyJWTKlv6wYDoJ Syew== X-Gm-Message-State: APjAAAVP9rRfvWTE+AaQub/FXL+ayHFLhzpZXV8AplS34MRvxfevAZGu S8l1hkMp7XuPU0rImIbED2aV4XW3ve3yFTxMXT9ZDrC6wrXtlQeJRxBrIyxKkwoi/BUk/qVwjN+ pZyCD8YbWXxRaFf30lrV8J4rR6zK9dyyyBw8PMIxUldeZl/A5QO1/Fvn2X7KuQoT+5w== X-Received: by 2002:a1c:9e4d:: with SMTP id h74mr111417823wme.9.1564512000603; Tue, 30 Jul 2019 11:40:00 -0700 (PDT) X-Google-Smtp-Source: APXvYqz3nAZXK0ZkLbfQoEkNrDxyL9eI4eq3wznzoYTRsY77LzovRmJpHGA8uW//bpmK6tudKFIo X-Received: by 2002:a1c:9e4d:: with SMTP id h74mr111417794wme.9.1564511999748; Tue, 30 Jul 2019 11:39:59 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1564511999; cv=pass; d=google.com; s=arc-20160816; b=EAVsHQxtP2R92GWmHUQImgyvXA/zwa7fk23UtNZhPBxa5hgUtmcjdJd/QH4hFAAS5/ F4ycAYxilj9LE5DP7JFBRQFSyE+CYbtFFRUhtDFj1wFRyZ5EPsDqYkaprA4xsVQ0wARk O0NPW+pJl2G/mfLbhL9LVsIM4kZFzeUdrcWqwmnVWZwTNlyqX6UzFoUmdFU9uJ4QIHqk xd+IpHkeOZVchMFzJBpphe9ISuN+pWvBWwmiijRqwYqyFNDhs9sjZ3eI7ddy4yePfMnw p95y3SJTdst8152f6QDJQhmA+Rh9csz/tTtljZUfKz0EyU/1pZfkQHj6wg8DrxPmLkbQ Cgzw== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:content-transfer-encoding:content-id:content-language :accept-language:in-reply-to:references:message-id:date:thread-index :thread-topic:subject:cc:to:from:dkim-signature:dkim-signature; bh=AUwSPm4smgaC06dcO2BrmAUXjLSZek9Pxdr2qqWzQb8=; b=a4rxp+CWKFpywEwZH6qvY9/anDXs4Sqpw5Pdc1uc3khXEqQjCCcML2k/NGkQi+wRa6 70eBLW/1BgatTYX071guQLzLyJcy1WP7vQ83j5sW7irhB60ekmCSwgCJ4LiknrWQ9HKV RY/LTpBfdX96YnOWKBD/s+h3bSuBa6CzurRX8j3qw2rKVhZ0uHSd2C8A8zihB57bkHGb 6ztohSpVrTrkhxIiAQfPu+NTQRTXGHCwbZ/tafzuBoNDnHfZCoRWWe+H5BEs58yqJ2dn qvIjvavgjw5xIz5AdAQRADmkO+QkuFjS77TLvxU+kcY9+uMVYuy3rXGVRj50XOIYRCit 7PHw== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=RLGTbz1o; dkim=pass header.i=@fb.onmicrosoft.com header.s=selector2-fb-onmicrosoft-com header.b="Ep3U/KS3"; arc=pass (i=1 spf=pass spfdomain=fb.com dkim=pass dkdomain=fb.com dmarc=pass fromdomain=fb.com); spf=pass (google.com: domain of prvs=31148e3214=songliubraving@fb.com designates 67.231.153.30 as permitted sender) smtp.mailfrom="prvs=31148e3214=songliubraving@fb.com"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=fb.com Received: from mx0a-00082601.pphosted.com (mx0b-00082601.pphosted.com. [67.231.153.30]) by mx.google.com with ESMTPS id v4si32527956wmc.134.2019.07.30.11.39.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Jul 2019 11:39:59 -0700 (PDT) Received-SPF: pass (google.com: domain of prvs=31148e3214=songliubraving@fb.com designates 67.231.153.30 as permitted sender) client-ip=67.231.153.30; Authentication-Results: mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=RLGTbz1o; dkim=pass header.i=@fb.onmicrosoft.com header.s=selector2-fb-onmicrosoft-com header.b="Ep3U/KS3"; arc=pass (i=1 spf=pass spfdomain=fb.com dkim=pass dkdomain=fb.com dmarc=pass fromdomain=fb.com); spf=pass (google.com: domain of prvs=31148e3214=songliubraving@fb.com designates 67.231.153.30 as permitted sender) smtp.mailfrom="prvs=31148e3214=songliubraving@fb.com"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=fb.com Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.27/8.16.0.27) with SMTP id x6UINe7F018323; Tue, 30 Jul 2019 11:39:57 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : references : in-reply-to : content-type : content-id : content-transfer-encoding : mime-version; s=facebook; bh=AUwSPm4smgaC06dcO2BrmAUXjLSZek9Pxdr2qqWzQb8=; b=RLGTbz1ottombFFiW1QrJ8odFtboKg60gAiDI1HkU2dvdeAp86dzNAjjD8pDrkKW/tZG TidiA8hVOULw1h0L10wTtZlEXguH5VRfR0zGnKvOw2xN9vX6BOer2sLO9EZBwVba9kdp OeJ4QN0Nz2R5ldsgsta9grgxJ5BLy0NCHto= Received: from maileast.thefacebook.com ([163.114.130.16]) by m0089730.ppops.net with ESMTP id 2u2p4b1ape-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Tue, 30 Jul 2019 11:39:57 -0700 Received: from ash-exhub103.TheFacebook.com (2620:10d:c0a8:82::c) by ash-exhub204.TheFacebook.com (2620:10d:c0a8:83::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Tue, 30 Jul 2019 11:39:55 -0700 Received: from NAM02-CY1-obe.outbound.protection.outlook.com (100.104.31.183) by o365-in.thefacebook.com (100.104.35.174) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1713.5 via Frontend Transport; Tue, 30 Jul 2019 11:39:55 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Ju8VsZs+Iw+j0/UmYIvv4JUldv6GPJoHMfMFf7tqbhonJMd0kSVNry3HCHWyMTEGsQPFdhGJ9le1UEbJ8zx70gMCcOjXreq7DhJAts3e6w+1fgf/DK6IjENvIJj/ze1aZTXnHK702T+b5hxkIa+aKPmL7OyhJWhUp7zhCrcaCnIVIsMWHIe06ov8dn6u3Af5eZa+6kF6jbhi/fvb53wcVoAEs06rUaHdt8fBP1/fs/nKiFP7cPjRfAvDN70YJN0iOXP06v4giHY38SHIHkf7kKE7JavpRPOqwH5lvp2u6gYM+pLopC5kCzL0fEHbFnuYvB1lPLFtWpFhQs3A5DHlqA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=AUwSPm4smgaC06dcO2BrmAUXjLSZek9Pxdr2qqWzQb8=; b=JqFJe/KZJsqpFae2za80+gCVZBV1jazX1m/2PKJWdKjAYG/N0RBFr6xxj5QymzCcB4NTDO615gud+fY+P3vQ0nD9DvpHMlfVSJlgO5H95CdV6KPw7Ock87+FBkcxJvrwHna5hO6UNf0m7Irppx/FMJtIDEmIt9Y7HweyzMlfhK/U+k0GjNXEIr6SuKT8UxG9NhE71RhzYD4yJo/UmxtW0NSqsgZknHQ4CdV32mltHWkzRoRZa/uN7QV/+LfIv9I6Z8QQd7orjLE1ulfz3yeQYfP5z92EsA5L8ktcGk5IFWRs3eCxTnOoE/cUrQM2ZMiPuOuSFjjVE+ZpZRklo/xQHQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1;spf=pass smtp.mailfrom=fb.com;dmarc=pass action=none header.from=fb.com;dkim=pass header.d=fb.com;arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.onmicrosoft.com; s=selector2-fb-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=AUwSPm4smgaC06dcO2BrmAUXjLSZek9Pxdr2qqWzQb8=; b=Ep3U/KS30jSXOTfYySxc7RUKFtytwfNi2VA+0fgrYYGazNfGJNmGZSHREwaNSdWTk4654YR4QTT2+rNeVhoF4kf2gGrAlHFVo5oyZQTPbMM8+tS0Q+NLT5MfKh0nfXFPffgCHQN3cXONWZ9rdWiOfB72KxSXtvOIGEkzRFQprUs= Received: from MWHPR15MB1165.namprd15.prod.outlook.com (10.175.3.22) by MWHPR15MB1167.namprd15.prod.outlook.com (10.175.3.147) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2115.15; Tue, 30 Jul 2019 18:39:54 +0000 Received: from MWHPR15MB1165.namprd15.prod.outlook.com ([fe80::d4fc:70c0:79a5:f41b]) by MWHPR15MB1165.namprd15.prod.outlook.com ([fe80::d4fc:70c0:79a5:f41b%2]) with mapi id 15.20.2115.005; Tue, 30 Jul 2019 18:39:54 +0000 From: Song Liu To: "Kirill A. Shutemov" CC: lkml , Linux-MM , "akpm@linux-foundation.org" , "matthew.wilcox@oracle.com" , "kirill.shutemov@linux.intel.com" , "oleg@redhat.com" , Kernel Team , "william.kucharski@oracle.com" , "srikar@linux.vnet.ibm.com" Subject: Re: [PATCH 1/2] khugepaged: enable collapse pmd for pte-mapped THP Thread-Topic: [PATCH 1/2] khugepaged: enable collapse pmd for pte-mapped THP Thread-Index: AQHVRdCXaB8qUzCo40K8bOFQNuNjzqbjQxwAgAAplQCAABQIgA== Date: Tue, 30 Jul 2019 18:39:54 +0000 Message-ID: <48DAF4DE-AB27-487A-B9B2-E733FA30A7B1@fb.com> References: <20190729054335.3241150-1-songliubraving@fb.com> <20190729054335.3241150-2-songliubraving@fb.com> <20190730145922.m5omqqf7rmilp6yy@box> <452746EE-186C-43D8-B15C-9921E587BA3A@fb.com> In-Reply-To: <452746EE-186C-43D8-B15C-9921E587BA3A@fb.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3445.104.11) x-originating-ip: [2620:10d:c090:200::3:5cb8] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: d08c1f08-cca6-4bdc-eec7-08d7151d5063 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1167; x-ms-traffictypediagnostic: MWHPR15MB1167: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:6108; x-forefront-prvs: 0114FF88F6 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(39860400002)(366004)(376002)(396003)(346002)(136003)(199004)(189003)(102836004)(476003)(33656002)(6916009)(76116006)(2616005)(66446008)(486006)(229853002)(86362001)(11346002)(50226002)(66556008)(64756008)(446003)(66476007)(256004)(71200400001)(4326008)(6246003)(25786009)(81156014)(66946007)(8676002)(68736007)(8936002)(71190400001)(46003)(81166006)(7736002)(5660300002)(99286004)(2906002)(6506007)(186003)(478600001)(14444005)(316002)(76176011)(6436002)(14454004)(36756003)(57306001)(53936002)(6486002)(53546011)(6116002)(305945005)(54906003)(6512007);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1167;H:MWHPR15MB1165.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: fb.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: hHsOqAID5UGAS+4qcrjJEN8IOBtIZYLa1GD3lrZI0Wn5zMbX+HcOrr9Ve6z57Eq9vO/0v57nOeSRWTqy86fkAjeGHnlyAC9fZgGxxluXBJZW+mRQVRWUrLbA2j/9qe7Ndc6rBPrwlpoJeiiMJiwP/LnNI9CwGmPlcQu2rGMFs1AlViIbmurQtEYu7TixjnL+9sO0I8D8kKExINpo7pds0byT193CB2fi2Jr+/B+BAoGQj5ZcBiUrK3Pr3/cfy7c4F8Xy+dHlD7RgcFPxLtfyjGM/ta86INWmjde8fDr5gmIpGIAQQWbRRT5XeaN0H9SN8ibCmbpTp0dEwXpvJqA/zboRg+Dyv4m+DtNnlPZ8DTcD+5FbQWDt+yuGh8u7LPvJ9TY83Qmo3n5vyS4cFWwz/EmioYK7F9ZzLPmnVbmYTJQ= Content-Type: text/plain; charset="us-ascii" Content-ID: <48545CF677458D478E69088DFEE8881D@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: d08c1f08-cca6-4bdc-eec7-08d7151d5063 X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Jul 2019 18:39:54.1584 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: songliubraving@fb.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1167 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-30_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=943 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907300191 X-FB-Internal: deliver 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: > On Jul 30, 2019, at 10:28 AM, Song Liu wrote: >=20 >=20 >=20 >> On Jul 30, 2019, at 7:59 AM, Kirill A. Shutemov w= rote: >>=20 >> On Sun, Jul 28, 2019 at 10:43:34PM -0700, Song Liu wrote: >>> khugepaged needs exclusive mmap_sem to access page table. When it fails >>> to lock mmap_sem, the page will fault in as pte-mapped THP. As the page >>> is already a THP, khugepaged will not handle this pmd again. >>>=20 >>> This patch enables the khugepaged to retry collapse the page table. >>>=20 >>> struct mm_slot (in khugepaged.c) is extended with an array, containing >>> addresses of pte-mapped THPs. We use array here for simplicity. We can >>> easily replace it with more advanced data structures when needed. This >>> array is protected by khugepaged_mm_lock. >>>=20 >>> In khugepaged_scan_mm_slot(), if the mm contains pte-mapped THP, we try >>> to collapse the page table. >>>=20 >>> Since collapse may happen at an later time, some pages may already faul= t >>> in. collapse_pte_mapped_thp() is added to properly handle these pages. >>> collapse_pte_mapped_thp() also double checks whether all ptes in this p= md >>> are mapping to the same THP. This is necessary because some subpage of >>> the THP may be replaced, for example by uprobe. In such cases, it is no= t >>> possible to collapse the pmd. >>>=20 >>> Signed-off-by: Song Liu >>> --- >>> include/linux/khugepaged.h | 15 ++++ >>> mm/khugepaged.c | 136 +++++++++++++++++++++++++++++++++++++ >>> 2 files changed, 151 insertions(+) >>>=20 >>> diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h >>> index 082d1d2a5216..2d700830fe0e 100644 >>> --- a/include/linux/khugepaged.h >>> +++ b/include/linux/khugepaged.h >>> @@ -15,6 +15,16 @@ extern int __khugepaged_enter(struct mm_struct *mm); >>> extern void __khugepaged_exit(struct mm_struct *mm); >>> extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma, >>> unsigned long vm_flags); >>> +#ifdef CONFIG_SHMEM >>> +extern int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, >>> + unsigned long addr); >>> +#else >>> +static inline int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, >>> + unsigned long addr) >>> +{ >>> + return 0; >>> +} >>> +#endif >>>=20 >>> #define khugepaged_enabled() \ >>> (transparent_hugepage_flags & \ >>> @@ -73,6 +83,11 @@ static inline int khugepaged_enter_vma_merge(struct = vm_area_struct *vma, >>> { >>> return 0; >>> } >>> +static inline int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, >>> + unsigned long addr) >>> +{ >>> + return 0; >>> +} >>> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >>>=20 >>> #endif /* _LINUX_KHUGEPAGED_H */ >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index eaaa21b23215..247c25aeb096 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -76,6 +76,7 @@ static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, = MM_SLOTS_HASH_BITS); >>>=20 >>> static struct kmem_cache *mm_slot_cache __read_mostly; >>>=20 >>> +#define MAX_PTE_MAPPED_THP 8 >>=20 >> Is MAX_PTE_MAPPED_THP value random or do you have any justification for >> it? >=20 > In our use cases, we only have small number (< 10) of huge pages for the > text section, so 8 should be enough to cover the worse case.=20 >=20 > If this is not sufficient, we can make it a list.=20 >=20 >>=20 >> Please add empty line after it. >>=20 >>> /** >>> * struct mm_slot - hash lookup from mm to mm_slot >>> * @hash: hash collision list >>> @@ -86,6 +87,10 @@ struct mm_slot { >>> struct hlist_node hash; >>> struct list_head mm_node; >>> struct mm_struct *mm; >>> + >>> + /* pte-mapped THP in this mm */ >>> + int nr_pte_mapped_thp; >>> + unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; >>> }; >>>=20 >>> /** >>> @@ -1281,11 +1286,141 @@ static void retract_page_tables(struct address= _space *mapping, pgoff_t pgoff) >>> up_write(&vma->vm_mm->mmap_sem); >>> mm_dec_nr_ptes(vma->vm_mm); >>> pte_free(vma->vm_mm, pmd_pgtable(_pmd)); >>> + } else if (down_read_trylock(&vma->vm_mm->mmap_sem)) { >>> + /* need down_read for khugepaged_test_exit() */ >>> + khugepaged_add_pte_mapped_thp(vma->vm_mm, addr); >>> + up_read(&vma->vm_mm->mmap_sem); >>> } >>> } >>> i_mmap_unlock_write(mapping); >>> } >>>=20 >>> +/* >>> + * Notify khugepaged that given addr of the mm is pte-mapped THP. Then >>> + * khugepaged should try to collapse the page table. >>> + */ >>> +int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, unsigned long = addr) >>=20 >> What is contract about addr alignment? Do we expect it PAGE_SIZE aligned >> or PMD_SIZE aligned? Do we want to enforce it? >=20 > It is PMD_SIZE aligned. Let me add VM_BUG_ON() for it.=20 >=20 >>=20 >>> +{ >>> + struct mm_slot *mm_slot; >>> + int ret =3D 0; >>> + >>> + /* hold mmap_sem for khugepaged_test_exit() */ >>> + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); >>> + >>> + if (unlikely(khugepaged_test_exit(mm))) >>> + return 0; >>> + >>> + if (!test_bit(MMF_VM_HUGEPAGE, &mm->flags) && >>> + !test_bit(MMF_DISABLE_THP, &mm->flags)) { >>> + ret =3D __khugepaged_enter(mm); >>> + if (ret) >>> + return ret; >>> + } >>=20 >> Any reason not to call khugepaged_enter() here? >=20 > No specific reasons... Let me try it.=20 Actually, khugepaged_enter() takes vma and vm_flags; while here we only =20 have the mm. I guess we should just use __khugepaged_enter(). Once we=20 remove all checks on vm_flags, khugepaged_enter() is about the same as=20 the logic above.=20 Thanks, Song [...]=