Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937339AbdLRRYm (ORCPT ); Mon, 18 Dec 2017 12:24:42 -0500 Received: from us-smtp-delivery-194.mimecast.com ([63.128.21.194]:27471 "EHLO us-smtp-delivery-194.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936796AbdLRRYe (ORCPT ); Mon, 18 Dec 2017 12:24:34 -0500 From: Trond Myklebust To: "bfields@fieldses.org" , "efault@gmx.de" CC: "linux-kernel@vger.kernel.org" , "linux-nfs@vger.kernel.org" , "jlayton@kernel.org" Subject: Re: NFS: 82ms wakeup latency 4.14-rc4 Thread-Topic: NFS: 82ms wakeup latency 4.14-rc4 Thread-Index: AQHTeBNgYuFsZjt8pUS1zqFlYV658aNJOoAAgAAR6oCAAAa8gIAABs4A Date: Mon, 18 Dec 2017 17:24:29 +0000 Message-ID: <1513617866.4581.6.camel@primarydata.com> References: <1513610231.7998.13.camel@gmx.de> <1513611112.7113.1.camel@gmx.de> <20171218163559.GA11829@fieldses.org> <1513616405.7113.18.camel@gmx.de> In-Reply-To: <1513616405.7113.18.camel@gmx.de> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [68.49.162.121] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;DM5PR11MB0074;20:I9IJqCWlKSC34mfL0XHI5+491Le9XNVONyqnEVC9k7PBL29r2k6Qi7vD22so5EevF+l+oPEkaGGJlhzvwqWdQU/tR2rEbBwW/f7eRNkTrVhG/qcduXRApsGKfUeF03sw7YREVglXrB1wop6Yfqu17FYkI+eCO9dae1UUB0ErEH4= x-ms-exchange-antispam-srfa-diagnostics: SSOS; x-ms-office365-filtering-correlation-id: 5b36ef3e-c5e4-4f6a-a380-08d5463c3236 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(5600026)(4604075)(4534020)(4602075)(4603075)(4627115)(201702281549075)(2017052603307);SRVR:DM5PR11MB0074; x-ms-traffictypediagnostic: DM5PR11MB0074: x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:; x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(6040450)(2401047)(8121501046)(5005006)(93006095)(93001095)(10201501046)(3002001)(3231023)(6041248)(20161123562025)(20161123560025)(20161123558100)(20161123555025)(20161123564025)(2016111802025)(201703131423075)(201702281528075)(201703061421075)(201703061406153)(6043046)(6072148)(201708071742011);SRVR:DM5PR11MB0074;BCL:0;PCL:0;RULEID:(100000803101)(100110400095);SRVR:DM5PR11MB0074; x-forefront-prvs: 0525BB0ADF x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(396003)(39830400003)(366004)(376002)(346002)(199004)(189003)(24454002)(377424004)(478600001)(8676002)(3280700002)(36756003)(6506007)(53936002)(93886005)(2900100001)(81156014)(2501003)(66066001)(7736002)(305945005)(6246003)(25786009)(4326008)(316002)(54906003)(110136005)(99286004)(76176011)(3660700001)(2906002)(14454004)(8666007)(3846002)(229853002)(6512007)(8936002)(86362001)(4001150100001)(97736004)(5660300001)(2950100002)(77096006)(6486002)(103116003)(81166006)(68736007)(102836003)(6116002)(106356001)(105586002)(6436002);DIR:OUT;SFP:1102;SCL:1;SRVR:DM5PR11MB0074;H:DM5PR11MB0075.namprd11.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;A:1;MX:1;LANG:en; spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-ID: <94BF55633380BF4891F5AB7C27186F39@namprd11.prod.outlook.com> MIME-Version: 1.0 X-OriginatorOrg: primarydata.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5b36ef3e-c5e4-4f6a-a380-08d5463c3236 X-MS-Exchange-CrossTenant-originalarrivaltime: 18 Dec 2017 17:24:29.6435 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 03193ed6-8726-4bb3-a832-18ab0d28adb7 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR11MB0074 X-MC-Unique: rGGE2MLuOkaOPpAqlHFviw-1 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id vBIHOk1k009012 Content-Length: 784 Lines: 22 On Mon, 2017-12-18 at 18:00 +0100, Mike Galbraith wrote: > On Mon, 2017-12-18 at 11:35 -0500, J. Bruce Fields wrote: > > > > Like I say, I don't really understand the issues here, so it's more > > a > > question than an objection.... (I don't know any reason a > > cond_resched() would be bad there.) > > Think of it this way: what all can be queued up behind that kworker > that is hogging CPU for huge swaths of time? It's not only userspace > that suffers. > Any cond_sched() belongs in the loop in nfs_commit_release_pages() (where it can be mitigated) rather than in a function whose purpose is to free memory. There is no reason to call it from the writeback or readpages code. -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@primarydata.com