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Fri, 20 Aug 2021 10:18:25 +0000 Date: Fri, 20 Aug 2021 18:18:14 +0800 From: Jisheng Zhang To: Thomas Gleixner Cc: John Stultz , Stephen Boyd , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] timer: Use static_branch_likely() for timers_nohz_active Message-ID: <20210820181814.2761b051@xhacker.debian> In-Reply-To: <87im0dqohb.ffs@tglx> References: <20210624163218.39ae3ec6@xhacker.debian> <87im0dqohb.ffs@tglx> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR03CA0362.namprd03.prod.outlook.com (2603:10b6:a03:3a1::7) To BL1PR03MB6055.namprd03.prod.outlook.com (2603:10b6:208:31b::6) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from xhacker.debian (192.147.44.204) by SJ0PR03CA0362.namprd03.prod.outlook.com (2603:10b6:a03:3a1::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4436.19 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Si5eISsPCy4kKVi61yvMOxBqchVmZp5N1y9sTc+DvNy9c9cabO6JTj2CxO8G?= =?us-ascii?Q?J52AOvIWmXwS3p/nQ4pPe7N3OSfxkme3NEg3V7d/7Jt3C0YrMv8OgdZwj4sQ?= =?us-ascii?Q?hAR4WwJfzHXPi7kNvyIKTbbDB8b99y9e4AHLYJ+oyawJfk0k1dzQj9MtAW1Z?= =?us-ascii?Q?sMlHOYC+XSzpvIQ5QhiaRjSmVC17o6hFNRcb8z1c7J4xY3RF3HFI97j5JJ+M?= =?us-ascii?Q?M0bnRRMtQE5ffCb66N3/wNVK0jKNS1TPjjgZQjxRhcNMQtPRvl3Kmr2vmC77?= =?us-ascii?Q?fF9G2dc6oo2y/8aYqHG9YTk+9E3KBdC+VjUTQFcrq2Du8q1D2KATktcHYUA2?= =?us-ascii?Q?nSmyTjArmU5GQQWikd6PaPB2hqNMxePFIoGgH8VW/xhPmS8jiliwdVZ4F+Ea?= =?us-ascii?Q?EJ5d8viD80AKiUi6RK3XOjNy4O0Bf7Jc/K+pHMC/igDel2QxoBn4G/sf8LwC?= =?us-ascii?Q?5tznoQFU2ovzEVNlfju3aGG9j8opS0HWJHGixROWDMbNJTaJlZA7Cxq16Ut4?= =?us-ascii?Q?oxDBYpxgCLkOBgxF8kCj2DXogODs3iBTCVXd2M6oelgXMjsPHjXpE++UL9Zp?= =?us-ascii?Q?wq07ZI2DTvErd977SeJ/zHwjCxMtw+fecFB/KizSUF+5qNxU5DOHV023iVBi?= =?us-ascii?Q?DCwp2BGvEbUgewJPqlO7RDQiEyZ/70r+Fcptt0NJiskAdcOWrFQ9SmG9vlVb?= =?us-ascii?Q?RdQo4bQfXWgfRVOVF+CvINdE8z5NP6zclABHUhl7ceh2XmxACJ2hRYtpL9zN?= =?us-ascii?Q?9Fa6fGFQ6x6ebda/EgcDvm0DJJgRLj6Z78WZMYth2NathrGxxUpAWKgjFcUF?= =?us-ascii?Q?8yjsALfJTSnXAS5BQw7DPW7Oe44qLwsgLPqDzUiCGn2fhjkSGwNEA79T2c7i?= =?us-ascii?Q?xpSGkXNtT1SkAz0F+REcFsD+mcSwqhAsmo2UaYSJ7jnK9b1b/ceLuyeW6hgq?= =?us-ascii?Q?r+854jv1sMtPc+FJI4gIteT6KGxXn8e+xnOeIx1FRNTs/bnkXUJW2A1zNJWF?= =?us-ascii?Q?3AdNd5S6FhJZdSCYH7DLvoatkyJQG9VaW3GEndNgYDYLPfjklzrV4eeQ14yD?= =?us-ascii?Q?q9lhP1dRdIiDyuHZgPPCppMU+zmC9AiQojhJb+f1ouajZA0axxrmDIomY2u2?= =?us-ascii?Q?q+dzzKRpm1t/mgPmBQRzYbbFqICK0JexynGgs6Uz3Lfd/IKMregPpE7sGkiX?= =?us-ascii?Q?7uku5B7nLlx5SjPM8M7NwbXGHCAkj06iESIarpmBkld6fxY3fVrkKYeTTYER?= =?us-ascii?Q?XqML1Zde1AJyRSdV751Yv+0fX45mPel0aj+9t3PcfwcAH2zzOB0/rWglgOmP?= =?us-ascii?Q?uPd1SgDegUt43XYL27WTn1va?= X-OriginatorOrg: synaptics.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7ca624c6-7ef0-4528-324f-08d963c3d896 X-MS-Exchange-CrossTenant-AuthSource: BL1PR03MB6055.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Aug 2021 10:18:25.5579 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335d1fbc-2124-4173-9863-17e7051a2a0e X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: LHISzLnm0iB+lcyadDY3dWPcuXe123zYzMjbgn2K+dVqfwQSbTzHWxWXy1SC/ruOtL37XlmF/Q33n3ECam05Kg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR03MB4289 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 10 Aug 2021 18:00:16 +0200 Thomas Gleixner wrote: > > > Jisheng, Hi Thomas, > > On Thu, Jun 24 2021 at 16:32, Jisheng Zhang wrote: > > > The static key timers_nohz_active is likely to be true, so use > > static_branch_likely() to reflect this fact. > > you still lack any justification for your statement that NOHZ active is > likely. This patch only affects NO_HZ_COMMON=y code path which is enabled if either NO_HZ_IDLE or NO_HZ_FULL = y. Per my understanding, when the system has oneshot tick device, NOHZ active is likely true. After going through drivers/clocksource/*, I found there are about 86 drivers, 69(occupies 80%) of which support CLOCK_EVT_FEAT_ONESHOT. Then I browsed apic, hpet and xen timer source code in x86 directory, they all support oneshot feature. I'm not sure whether I misunderstood the code or not. Thanks > > It might be likely for your system, but is this true in general? >