From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752873AbbJUHLK (ORCPT ); Wed, 21 Oct 2015 03:11:10 -0400 Received: from mail-am1on0095.outbound.protection.outlook.com ([157.56.112.95]:6896 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751721AbbJUHLI convert rfc822-to-8bit (ORCPT ); Wed, 21 Oct 2015 03:11:08 -0400 X-Greylist: delayed 866 seconds by postgrey-1.27 at vger.kernel.org; Wed, 21 Oct 2015 03:11:08 EDT From: Gilad Ben Yossef To: Frederic Weisbecker , Chris Metcalf CC: Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andrew Morton , Rik van Riel , Tejun Heo , Thomas Gleixner , "Paul E. McKenney" , Christoph Lameter , Viresh Kumar , Catalin Marinas , "Will Deacon" , Andy Lutomirski , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v8 08/14] nohz_full: allow disabling the 1Hz minimum tick at boot Thread-Topic: [PATCH v8 08/14] nohz_full: allow disabling the 1Hz minimum tick at boot Thread-Index: AQHRC3cTX8zoQw/6A0K/dtQOsFEXHJ503qCAgACie3A= Date: Wed, 21 Oct 2015 06:56:38 +0000 Message-ID: References: <1445373372-6567-1-git-send-email-cmetcalf@ezchip.com> <1445373372-6567-9-git-send-email-cmetcalf@ezchip.com> <20151020210331.GC29289@lerouge> In-Reply-To: <20151020210331.GC29289@lerouge> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=giladb@ezchip.com; x-originating-ip: [212.179.42.66] x-microsoft-exchange-diagnostics: 1;AM2PR02MB0772;5:Meiu9G4vpAE5URY/HQ9jIWkf5w5TGcuvwOaQevieRHqhL5iDaOhm9ahEeVU9ufURKvQLjmRrV+uDWc0YaYQciO3pl4C/SB8B66I0KtFVA+fHhpnQOXXT7pEtRZTdYkLKYA/UTvMcH3zIS6vFp8EDAg==;24:Pz92FURYyKIbz2YrQazXZ4Zzp4B2JwFqs78ihMV+md9HbBnFiJ8b6l1Nu8A4/EBjijljaUcML3Sp06evwVQIt/aRbHa/ZdIS39ofMA34d48=;20:O21/J5dS8RMBftqC26hX4HAo3fjFZwILWmH9lB5f6NWtng6FMy87JjAqQb6P3ht0Wu1W6YEpL0S6FYwO50iqNQ== x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:AM2PR02MB0772; x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(121898900299872); x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(601004)(2401047)(8121501046)(5005006)(520078)(3002001);SRVR:AM2PR02MB0772;BCL:0;PCL:0;RULEID:;SRVR:AM2PR02MB0772; x-forefront-prvs: 073631BD3D x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(6009001)(189002)(164054003)(199003)(92566002)(4001450100002)(561944003)(5007970100001)(33656002)(5004730100002)(76576001)(10400500002)(5003600100002)(46102003)(86362001)(77096005)(102836002)(101416001)(19580405001)(19580395003)(122556002)(40100003)(87936001)(2950100001)(54356999)(50986999)(76176999)(2900100001)(189998001)(5001960100002)(106356001)(106116001)(74316001)(105586002)(64706001)(5002640100001)(5001920100001)(5008740100001)(5001770100001)(97736004)(81156007)(66066001);DIR:OUT;SFP:1101;SCL:1;SRVR:AM2PR02MB0772;H:AM2PR02MB0417.eurprd02.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; spamdiagnosticoutput: 1:23 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-OriginatorOrg: ezchip.com X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Oct 2015 06:56:38.7060 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 0fc16e0a-3cd3-4092-8b2f-0a42cff122c3 X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM2PR02MB0772 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Frederic Weisbecker [mailto:fweisbec@gmail.com] > > This option also allows easy testing of nohz_full and task-isolation > > modes to determine what functionality needs to be implemented, > > and what possibly-spurious timer interrupts are scheduled when > > the basic 1Hz tick has been turned off. > > > > Signed-off-by: Chris Metcalf > > There have been proposals to disable/tune the 1 Hz tick via debugfs which > I Nacked because once you give such an opportunity to the users, they > will use that hack and never fix the real underlying issue. > > For the same reasons, I'm sorry but I have to Nack this proposal as well. > > If this is for development or testing purpose, > scheduler_max_tick_deferment() is > easily commented out. The problem with the latter is that it is much easier get back to one of the poor^H^H^H^H brave souls that are willing to risk their kittens testing this stuff for us saying: "can you please boot without this boot option and let me know if that behavior you were complaining about still happens?" rather than "can you please go to this and that line in the source file and un-comment it and re-compile and see if it still happens?" I hope this makes more sense. Thinking about it, it's probably a good idea to taint the kernel when this option is set as well. Thanks, Gilad