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Wed, 6 Jan 2021 17:45:54 +0000 Date: Wed, 6 Jan 2021 12:45:51 -0500 From: Paul Gortmaker To: Peter Zijlstra Cc: paulmck@kernel.org, linux-kernel@vger.kernel.org, yury.norov@gmail.com, kernel-team@fb.com Subject: Re: [PATCH RFC cpumask 4/5] cpumask: Add "last" alias for cpu list specifications Message-ID: <20210106174551.GB16838@windriver.com> References: <20210106004850.GA11682@paulmck-ThinkPad-P72> <20210106004956.11961-4-paulmck@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Originating-IP: [128.224.252.2] X-ClientProxiedBy: YTOPR0101CA0011.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b00:15::24) To DM6PR11MB4545.namprd11.prod.outlook.com (2603:10b6:5:2ae::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from windriver.com (128.224.252.2) by YTOPR0101CA0011.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b00:15::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3742.6 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?i1AXFFzl3H/B5ggf/z2mFhFC2+/bnzSaIb6VzybZat3APFjccmefnpPFHgUE?= =?us-ascii?Q?o2mKHpYvwGGBw3C4+03drGkG9FHhigKiKEF4dXbr00S4u/5817IHk+91KFkE?= =?us-ascii?Q?u2mbnPzbDRMgh++MzhMFC+hdwM9emkqvIoKodJqY7B/m0zzM9jprQdbG90VR?= =?us-ascii?Q?Xpx/IkDUSx5zc4KZZqv/ELmRy0URth2X1X9qErpKzngddfti4U6oDKbUhcFl?= =?us-ascii?Q?kw5ZaoA0Ajt3xrOUjpfgwUN8E8Z6nA2wOJgPdNktIwXW9AzNYV97tGxCxZUl?= =?us-ascii?Q?1ib1KYq0dtvbnK/KLicaHCtIHkpIjTaJMXjnYiJoY5fmbHiBvyUiH2Gpqifv?= =?us-ascii?Q?qCJZkWyzWbjdQReOwYjiQ0a5gVkv8idPAMK1g75Ck6+piVvF7trWOiHe3VKZ?= =?us-ascii?Q?rJyyxb1u+ZL7Xxpzj5eyI85KT3PklMCY2bem/sclOWAQP7yZF4WrijwWx/Hz?= =?us-ascii?Q?oRdHxfV5szRrK+zGTx1Dwlk2D+5FOKSL3rmOYUQXkDNDtQTtLarA6P+ihgZW?= =?us-ascii?Q?K5p+7mOQU3qz9gzrTsZQx7cSUvdK0dSk07x7mehgShUDerrbZ2xtl41wBe9O?= =?us-ascii?Q?Y9VLf27dQ5j6JniOhT9lfIRtzhc/6RGC6YR/734waqBGS7M3dPETUYmhEuTN?= =?us-ascii?Q?KI7egW4hoAcFIV4rjVDOENZQe4rmrI2R/cfqeVLoOtIdXDXDRAgrGC8uqU+M?= =?us-ascii?Q?nnbWonMjliJCV2DTPCM2lO30FRtlByEhI+aQ3PmCrIrf5yM+M71woskPg+RC?= =?us-ascii?Q?vKFIEYhiQdXVJbmx5dXjCjoHbECgY6JbBuUhU1Nm2xAuouG1ybkT3TIBttp8?= =?us-ascii?Q?2dkrZltqnt5Sc/chCa7lYQCxEHasrhoT3NR7xIZw3W9Mmz5PqoZIiM0guq/o?= =?us-ascii?Q?sNp2l054XVYI9ZjUXeAMEu/2A4yTmuAkCDw2lZJZ0Ano1idq4el3Gatikvaa?= =?us-ascii?Q?vwDIBcNTeM/c7rZ8729C7yTK7T7Dm6+DvoZxYwIgUSrMLFFszZ05J2C2Weh9?= =?us-ascii?Q?DjeE?= X-OriginatorOrg: windriver.com X-MS-Exchange-CrossTenant-AuthSource: DM6PR11MB4545.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jan 2021 17:45:54.8582 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ddb2873-a1ad-4a18-ae4e-4644631433be X-MS-Exchange-CrossTenant-Network-Message-Id: 3ba86ea3-0389-40ac-9dd9-08d8b26aead5 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: j84zfLKUzt4DdBYNGZ30O/1cFDzq7sgQdoPBgNVXNwinIhByKigZKa/c4CvD9jtMUccXSxX38Oexr5KY+FrcOPOEjbxfbaulbOeQxcN7Mnw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR11MB3898 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Re: [PATCH RFC cpumask 4/5] cpumask: Add "last" alias for cpu list specifications] On 06/01/2021 (Wed 10:49) Peter Zijlstra wrote: > On Tue, Jan 05, 2021 at 04:49:55PM -0800, paulmck@kernel.org wrote: > > From: Paul Gortmaker > > > > It seems that a common configuration is to use the 1st couple cores > > for housekeeping tasks, and or driving a busy peripheral that generates > > a lot of interrupts, or something similar. [...] > > A generic token replacement is used to substitute "last" with the > > number of CPUs present before handing off to bitmap processing. But > > it could just as easily be used to replace any placeholder token with > > any other token or value only known at/after boot. > > Aside from the comments Yury made, on how all this is better in > bitmap_parselist(), how about doing s/last/N/ here? For me something > like: "4-N" reads much saner than "4-last". OK, I can see N used as per university math classes... to indicate the end point of a fixed set of numbers, but I confess to having had to think about it for a bit (university was a long time ago). I don't have any strong opinion one way or another -- "last" vs. "N"... > Also, it might make sense to teach all this about core/node topology, > but that's going to be messy. Imagine something like "Core1-CoreN" or > "Nore1-NodeN" to mean the mask all/{Core,Node}0. > > And that is another feature that seems to be missing from parselist, > all/except. Seems reasonable, but I'm going to look at fixing up what I've got as per Yury's comments before volunteering to muck around with more string parsing code to add more features... Thanks, Paul. --