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Shutemov" Subject: [LSF/MM TOPIC] (again) THP for file systems Thread-Topic: [LSF/MM TOPIC] (again) THP for file systems Thread-Index: AQHUw+d98PJr/f1RW0yrtlybflg8VA== Date: Wed, 13 Feb 2019 22:00:10 +0000 Message-ID: <77A00946-D70D-469D-963D-4C4EA20AE4FA@fb.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3445.102.3) x-originating-ip: [2620:10d:c090:180::1:f80f] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 57ec5233-de4e-4423-2a70-08d691fe9fac x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600110)(711020)(4605077)(2017052603328)(7153060)(7193020);SRVR:MWHPR15MB1439; x-ms-traffictypediagnostic: MWHPR15MB1439: x-ms-exchange-purlcount: 3 x-microsoft-exchange-diagnostics: 1;MWHPR15MB1439;20:hy1n5M+KXnbfYRHZrH+M4PwwePhRQeMxosaf5HpofpptO/oxnWZTFruJH6u813Z6z7Me8LBxvs9bL2+Z6MDEElIJ24TNn/RzQ9qoq8vjoSu08cOtPcmS26VptXLLRcY9HgZ0rK4+E5eL7hmTgyuv1+qvftFemjD7xs5GPQnxCZQ= x-microsoft-antispam-prvs: x-forefront-prvs: 094700CA91 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(396003)(376002)(136003)(366004)(39860400002)(346002)(189003)(199004)(2501003)(81166006)(478600001)(6116002)(33656002)(4743002)(966005)(99286004)(57306001)(53936002)(81156014)(8676002)(105586002)(6436002)(7736002)(4326008)(110136005)(106356001)(6486002)(316002)(6306002)(8936002)(83716004)(71200400001)(71190400001)(6512007)(68736007)(102836004)(97736004)(46003)(36756003)(2906002)(2616005)(82746002)(6506007)(305945005)(50226002)(486006)(256004)(25786009)(86362001)(186003)(14454004)(2201001)(476003);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1439;H:MWHPR15MB1165.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A: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: j5JNJSuf3Ta1uW0DAHUEjrTXHZFFekoxIpEMCDEtvdG0invqqin5/4j0fE7vhEmRO4IpuhOF7bTKfm8dwzWSy723uKR3t0Zeo79wA2Y0+hnY/w+XvBFDbisXzWdKogKmbNPU/j79AsFnB4sxNe+dogNYM6cjig5sp4W1UMjS4j5svs/c2O6vlDM8vUzXpp8iyYNLXAWWwSRse6q0A38UxWqwHWfPqYLkr0nWZQ47fDNppnG0/h3ltmmKTg/86J4c8c7qtvQmV9wSUU16dWzD5iR3qMgn5XBfajpqxKCqsLJ4Z6IBx9kUXdA9RPfe1v4/OpipklPCUbGG+dXCLCWnPscdHXRBWlb2LI6uJQPQUI3XNnTTCV61cAFw8ApYb/oeuy91FbYPOkHbPWrX8E6RpGjnYcij/RZ9vWUN9yl05UE= Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 57ec5233-de4e-4423-2a70-08d691fe9fac X-MS-Exchange-CrossTenant-originalarrivaltime: 13 Feb 2019 22:00:10.3502 (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-Transport-CrossTenantHeadersStamped: MWHPR15MB1439 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-13_12:,, signatures=0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe 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: Hi, I would like to attend the LSF/MM Summit 2019. I'm interested in topics abo= ut BPF, mdraid, and MM. I am a designated reviewer of BPF. I am also helping J= ens organize mdraid patches. I would like to discuss remaining work to bring THP to (non-tmpfs) file sys= tems. This topic has been discussed multiple times in previous LSF/MM summits [1]= [2]. However, there hasn't been much progress since late 2017 (the latest work I= can find is by Kirill A. Shutemov [3]). We (Facebook) uses THP in many services. We see significant savings by putt= ing hot-text on THP. To achieve this with state-of-the-art Linux Kernel, we hav= e to either: trick the Kernel to believe certain region is anonymous pages; or p= ut the executable in tmpfs. In our case, the tmpfs solution is too expensive. Therefore, we use a hack to trick the Kernel. This hack breaks other useful features, e.g. perf symbols and uprobes. Instead of introducing more hacks = to use these broken features, it is better to enable THP for file systems. Therefore, we would like discuss (for one more time) what is needed to brin= g THP to file systems like ext4, xfs, btrfs, etc. Once we are aligned on the direction, we are more than happy to commit time and resource to make it ha= ppen. Since this topic is my main focus of this year's summit, I would like an in= vite to the MM track. Thanks, Song [1] https://lwn.net/Articles/686690/ [2] https://lwn.net/Articles/718102/ [3] https://kernel.googlesource.com/pub/scm/linux/kernel/git/kas/linux/+/hu= geext4/wip=