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Shutemov" , Johannes Weiner , Matthew Wilcox Subject: Re: [PATCH v3 0/2] mm,thp: Add filemap_huge_fault() for THP Thread-Topic: [PATCH v3 0/2] mm,thp: Add filemap_huge_fault() for THP Thread-Index: AQHVR3mCOKwnV56WUUyluRdig0XL86bkZvIA Date: Wed, 31 Jul 2019 08:35:46 +0000 Message-ID: References: <20190731082513.16957-1-william.kucharski@oracle.com> In-Reply-To: <20190731082513.16957-1-william.kucharski@oracle.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:c090:180::1:6d8b] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 63204fcb-963d-4141-b478-08d7159215bb x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1312; x-ms-traffictypediagnostic: MWHPR15MB1312: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:6108; x-forefront-prvs: 011579F31F x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(136003)(346002)(39860400002)(376002)(366004)(396003)(199004)(189003)(305945005)(57306001)(50226002)(54906003)(8936002)(446003)(102836004)(2616005)(486006)(186003)(71190400001)(66556008)(64756008)(476003)(5660300002)(478600001)(6506007)(81156014)(66476007)(229853002)(6486002)(76176011)(68736007)(46003)(76116006)(36756003)(53546011)(66446008)(6916009)(4326008)(11346002)(66946007)(6116002)(14454004)(33656002)(256004)(81166006)(53936002)(6246003)(25786009)(8676002)(71200400001)(99286004)(6512007)(7416002)(316002)(6436002)(2906002)(7736002)(86362001)(142933001)(14583001);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1312;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: lZAkvh2sNC1fzKIaVom/N0TJGn2sn7KEJwVOMM2SS3IozJgmhQ9XR83aIGn7IpM6sL78d8BkO+IF5mISw/XPLJB6Mlm7TKSI2d/evRF2pi8S6tQRkW1rFiy93zs/o0r4Ecx1rRKriurH6Uhsg54C0kaeHZI4/D0NGVP7KV+52ZHuY5XWpiqEKYwoUV6GZdX7/at87BFAWqCKY3IMqDbObAoqli0+Xqs9d6cRHRJ7b1YLHYjIpI+pnrbLD1oTbulDW63tmCMdQpj/AyFUUQDp7B4851KVyi94YDKSIZZSjqtkXRkhBNYufC2BUFizuzSEVFDgKCjn75dpvNEN0izwqannkxojKbeSZU2XmkYVwQbNDRzRme/wKumDl8i1LeeNRr4v8GxtwOaWhLcsxzEYs1PWoS1NA1PmzR3ajQtiL5M= Content-Type: text/plain; charset="us-ascii" Content-ID: <2E2A26E3179D714EACC580A7A1618AB3@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 63204fcb-963d-4141-b478-08d7159215bb X-MS-Exchange-CrossTenant-originalarrivaltime: 31 Jul 2019 08:35:46.7934 (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: MWHPR15MB1312 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-31_04:,, 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=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907310092 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jul 31, 2019, at 1:25 AM, William Kucharski wrote: >=20 > This set of patches is the first step towards a mechanism for automatical= ly > mapping read-only text areas of appropriate size and alignment to THPs > whenever possible. >=20 > For now, the central routine, filemap_huge_fault(), amd various support > routines are only included if the experimental kernel configuration optio= n >=20 > RO_EXEC_FILEMAP_HUGE_FAULT_THP >=20 > is enabled. >=20 > This is because filemap_huge_fault() is dependent upon the > address_space_operations vector readpage() pointing to a routine that wil= l > read and fill an entire large page at a time without poulluting the page > cache with PAGESIZE entries for the large page being mapped or performing > readahead that would pollute the page cache entries for succeeding large > pages. Unfortunately, there is no good way to determine how many bytes > were read by readpage(). At present, if filemap_huge_fault() were to call > a conventional readpage() routine, it would only fill the first PAGESIZE > bytes of the large page, which is definitely NOT the desired behavior. >=20 > However, by making the code available now it is hoped that filesystem > maintainers who have pledged to provide such a mechanism will do so more > rapidly. Could you please explain how to test/try this? Would it automatically map all executables to THPs?=20 Thanks, Song=