From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932138AbdEQOvE (ORCPT ); Wed, 17 May 2017 10:51:04 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:35997 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753693AbdEQOu4 (ORCPT ); Wed, 17 May 2017 10:50:56 -0400 Authentication-Results: codeblueprint.co.uk; dkim=none (message not signed) header.d=none;codeblueprint.co.uk; dmarc=none action=none header.from=fb.com; Subject: Re: hackbench vs select_idle_sibling; was: [tip:sched/core] sched/fair, cpumask: Export for_each_cpu_wrap() To: Peter Zijlstra , , , , , , , , References: <20170414122005.o35me2h5nowqkxbv@hirez.programming.kicks-ass.net> <20170517105350.hk5m4h4jb6dfr65a@hirez.programming.kicks-ass.net> CC: , , From: Chris Mason Message-ID: <8e44a5e1-35b0-7895-f313-c9a765e20b11@fb.com> Date: Wed, 17 May 2017 10:49:46 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170517105350.hk5m4h4jb6dfr65a@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [2620:10d:c091:180::1:c111] X-ClientProxiedBy: DM3PR12CA0071.namprd12.prod.outlook.com (10.161.151.143) To BN6PR15MB1652.namprd15.prod.outlook.com (10.175.131.145) X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN6PR15MB1652: X-MS-Office365-Filtering-Correlation-Id: aee61982-1e6e-4e11-d243-08d49d33f998 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(201703131423075)(201703031133081);SRVR:BN6PR15MB1652; X-Microsoft-Exchange-Diagnostics: 1;BN6PR15MB1652;3:ss12G8Rg7WdM43Am9BT6haQrEmoSbblu/Nx6T06tyqBh++bh9If7WUl2aGyXc+Wl1zd95K6TTxfilaV9x/pjhDhpndT6DvB0hNHS9it/w9tP5DZZIeSzmjB1IBTZTJIo97Q9gV6YDBKNZ+aABk0Vc99xpCjpJE6RfHCiG3IwMYzEfQXqgNv6YeYlaAnxBV4IVtkNlVo20vMc8wIGSJU2IZlW9Fez38tLk/T9u3Q8TcvyJTOYiMBq1WbDIIaob/5PK/CQHf4444ewRpQN+LVpORx0tIvJ31qWr48CvvTSjqOKRKWtyUy9hG+zj2O0aLduHQhHqLIYzkUyAlJ3HlAQQQ==;25:iky/VoET5k6JtE3zeIsKEyjUEIEXVxBrS3X4+H6i5KU+i60zI3iTrBwm8kpKp/p8EEzvO2JrmSk010mbhhBlYhAJJ7ZpcEKhW+0jNDy1K6qfInufOi5HE4CYmwsND84kqGsPZz63iBCRt0UCicyMxmZxKD5tXM8qkujA0lwUgzSC6ikKfQ3J/9v4Uq+JVF9FZntUFfD0/bPRQ3ifOoZdCpouLHJjbzC4C4JDyYqWeq+6gazriG20EGlkz1ilTz1bUcVSp9MVguzoJgkV30WaBKFAV9Xr4G2xteZo4R39oOJ4VB1Ma2Ma+FbyeBZ0+3zFN+a4AROo39pm2tVewYX6OA9bHkSTtNsGJaH6GxkFZKW3TvPc1zS94xjO6r/L97hXeuIEjsWUrkNlls4LQ72Rvx6HtHvhsHF+3SYBnjnFxq/0CFZiiM2Wg+bBrKe4db9094atml3/x2MjeCdApmfcpjgnOu3yJiPvKbbAhhLo8ks= X-Microsoft-Exchange-Diagnostics: 1;BN6PR15MB1652;31:PicVF2xTHvNK+zJdt1r/0gf5a4DGgA4NTgFWpDt49yxgtTGjG9TTkECMzJVh8rbCW//eDpFjAxFGjUWZl6Qa++M+6cU2sYgb4olTBZXX/Q/XV+tEVPXKx4js5FGP6G8xciUCkNjYHtE8BTABussxRYHeB8xax6NECnmlwn6ZQ/fD7ozi+j+htIxaItSCEhKmpTJeQtxegIyn8COKo1IrkTTzefTvcj0zb1wLzIj4/iZiao9k5WvD2sn0fAprfSN8BDCE6Hi7iuiXFGt/p2kcyw==;20: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 X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(6040450)(601004)(2401047)(5005006)(8121501046)(93006095)(93001095)(3002001)(10201501046)(6041248)(20161123560025)(20161123564025)(20161123555025)(20161123562025)(20161123558100)(201703131423075)(201702281528075)(201703061421075)(201703061406153)(6072148);SRVR:BN6PR15MB1652;BCL:0;PCL:0;RULEID:;SRVR:BN6PR15MB1652; X-Microsoft-Exchange-Diagnostics: 1;BN6PR15MB1652;4: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 X-Forefront-PRVS: 0310C78181 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(4630300001)(6009001)(39410400002)(39450400003)(39840400002)(39850400002)(39400400002)(377454003)(24454002)(83506001)(25786009)(7736002)(53546009)(2201001)(189998001)(33646002)(31696002)(54356999)(76176999)(50986999)(42186005)(31686004)(86362001)(8666007)(50466002)(54906002)(305945005)(7416002)(6486002)(65806001)(64126003)(65826007)(38730400002)(6666003)(81166006)(2906002)(2950100002)(230700001)(229853002)(8676002)(47776003)(6246003)(478600001)(53936002)(4001350100001)(5660300001)(36756003)(23746002)(42262002);DIR:OUT;SFP:1102;SCL:1;SRVR:BN6PR15MB1652;H:[IPv6:2620:10d:c0a1:1110:8000::206f];FPR:;SPF:None;MLV:sfv;LANG:en; X-Microsoft-Exchange-Diagnostics: =?Windows-1252?Q?1;BN6PR15MB1652;23:KrJoIzV6EekIvjJGF4cv21kRGh1O9RqB/dlJP?= =?Windows-1252?Q?/6jRw4QHCKb/6X8qgzEh0M9ybtxXSqyqgyJPbVjV+675Z3tArIcF3SsB?= =?Windows-1252?Q?42UCmK+CU1AfpMXrbSUDTCYjIrDVlj7Zo52eYpOAccQHwC3mLbZ7vD3E?= =?Windows-1252?Q?R+ZYFQ0BYeBL/1zNSzIwdKLyCmxht3nPUvo1AjtAnqmNQTvCJthfmqAz?= =?Windows-1252?Q?oa18NSrjfqep6Gk76SSNKwc6vFplrYmC6GK1kihzswGg8fqb12Hwvxka?= =?Windows-1252?Q?YQfpnTf4EriCzD49xxxkMxXvpG+kZnv/jqHFdD5f79pGxmGtXGeZh2MS?= =?Windows-1252?Q?N3r+ZqeVIRDjODPEs9VD/swKX+lfrUcLB/Pw7pCFRXvfNkX+5FYtkqUj?= =?Windows-1252?Q?q7jo4lqw0Da6MgfbUt/nLwPJkE2qX1tj4Xe4wH/o7rvN2gaYldkeI2QC?= =?Windows-1252?Q?LIPFT89QGbqG/aRLh0FevmgGZyAzWBdPvcZlJByECpevBYa2d6LXemsc?= =?Windows-1252?Q?wMgoDC/OSy42DqrAg9ZtKUi8fcKlLKeFxCsLUE250Pz1iSHhOi2HtHDn?= =?Windows-1252?Q?iPowHyXVUp7eTogsnvO7jAYgILO+Eeng+oz75swUWEzdTILvH9n48+Vx?= =?Windows-1252?Q?KpDWq9p2UskqhlJSyxMQpa9XBOcuP1e/TnLGiOM1zhw24rNh/gYqY3sK?= =?Windows-1252?Q?p0ZzC8371XyzG1B1sDq9kVpewm/Gw6gxng8yU7yHrOPwptqZPBFZPmzo?= =?Windows-1252?Q?iq9vrjnK/9W81krMakRTLPcNQLhA6suUfXp2+DAYv016dWQVycpdEx90?= =?Windows-1252?Q?/dU1a0eV3kHmK+7vJEXuaTslYgUvJmDU4ohoEi7USl05JPDzc8+y0FO4?= =?Windows-1252?Q?Wha37wsz1Bfk1ohMjdaNdG0LVfG04qN4/+CMI9UzLcjVgKqL3ZLX3HRl?= =?Windows-1252?Q?frM3fLHj0xcS1hm1DgN6M3SCzgGfADHgeuno4JcEedXWQt2Pa16o99Yq?= =?Windows-1252?Q?cVUxkTne/9e89OCCGp/0AdHkS9UPRv5QCDcwW0LXEDuYsQakof42ddVc?= =?Windows-1252?Q?/SJq0DLpj7LNakWKBquVQb75cQ3KUAqwur80pIl4+tIR5O/kPiDYg5ql?= =?Windows-1252?Q?vIqH2KMpsXMBAXtxU9RHr/AA92v7NX1HVkCqNIhVWy4ZZqPYeaZWHZXu?= =?Windows-1252?Q?Es3OV8OZ3G+h3d+9Hz+99LYpeBT+tvl8J+8kXQURZKOI+qW96Mc/qxhE?= =?Windows-1252?Q?n9rJhMuCJBxB24jLx3qXeD+5bQTVvDK54juLrXZq6oMaW/M7cmSW83NK?= =?Windows-1252?Q?vyTAiov9nu0VojSBA/iUcmHZg=3D=3D?= X-Microsoft-Exchange-Diagnostics: 1;BN6PR15MB1652;6: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;5:aJ10Li3EGAKyjZ4hO99uVXOT1Kx8Ck0Vm1WS8Pu6lLHjCGyfiyS7byU7bOB2e97jaPgkVBt05++0cSF9UDle8rrViYFNxf3RNEIE1OBhsGeH5bG+7RSeezqLaccvFpJ+9WJehyAubwdJYW8Iv7gEOw==;24:4OLHkRmZtdzrhqOZZmJf/28UM1Sb4xJ9SuvTyOl6eWNd4lnCErs3WiGf0KdWyVT/3ZzSIHoxQZwYKDgdy2UYw73mQK6ysfk3YKkAC7IUAqU= SpamDiagnosticOutput: 1:99 SpamDiagnosticMetadata: NSPM X-Microsoft-Exchange-Diagnostics: 1;BN6PR15MB1652;7:AFVjJs7TFWqXO48tuoWM+ZHEmYgNj3h1jbR7Baju6e0jEwtfdKViZQ1/jGhKdA6ugWODEse5QIdSQjKvSJFXXkzjbMhoIYtVfEgUt/0C3l2W3yxRbA74csOBB64id0xrWuUDsoVHMM1TPxgYFdgVIaHIjm6GYu2eW8/jsSc167KiDdlAPnPRMmikeXDnkK9obJm30ecn7ZWLLPX0lRIFyhCM4hzt9E7BVqtsBKxOZjN3H4+YLjlnl4mPAVrmVz9uDZf03FBOnrZcVmw+WLWWAcy6zlZ4cYAr4w4QoBvUi1aOrkqM749D1hVnEY3+5YOuQv0yEJLf0h6BfBZ5rKMMOQ==;20:NlcGWGYJDFWLOh+lK3wPRi1vniWDHWRmy0mObFCtVj7CRhxpdlbPYaJ+pAwUjfUrWInQa7ZhYerjOb4n/6wH8ZeZoB+w9HYr8u0pxRirzANIKmlG0Vrbj1bJWgMhuMHYZqCPifmyNWa0Eu3c6oe6sHDnlu94ictoVM0RoxtPs7M= X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 May 2017 14:49:50.4102 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR15MB1652 X-OriginatorOrg: fb.com X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-05-17_11:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/17/2017 06:53 AM, Peter Zijlstra wrote: > On Mon, May 15, 2017 at 02:03:11AM -0700, tip-bot for Peter Zijlstra wrote: >> sched/fair, cpumask: Export for_each_cpu_wrap() > >> -static int cpumask_next_wrap(int n, const struct cpumask *mask, int start, int *wrapped) >> -{ > >> - next = find_next_bit(cpumask_bits(mask), nr_cpumask_bits, n+1); > >> -} > > OK, so this patch fixed an actual bug in the for_each_cpu_wrap() > implementation. The above 'n+1' should be 'n', and the effect is that > it'll skip over CPUs, potentially resulting in an iteration that only > sees every other CPU (for a fully contiguous mask). > > This in turn causes hackbench to further suffer from the regression > introduced by commit: > > 4c77b18cf8b7 ("sched/fair: Make select_idle_cpu() more aggressive") > > So its well past time to fix this. > > Where the old scheme was a cliff-edge throttle on idle scanning, this > introduces a more gradual approach. Instead of stopping to scan > entirely, we limit how many CPUs we scan. > > Initial benchmarks show that it mostly recovers hackbench while not > hurting anything else, except Mason's schbench, but not as bad as the > old thing. > > It also appears to recover the tbench high-end, which also suffered like > hackbench. > > I'm also hoping it will fix/preserve kitsunyan's interactivity issue. > > Please test.. We'll get some tests going here too. -chris