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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by CH2PEPF00000143.mail.protection.outlook.com (10.167.244.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9520.1 via Frontend Transport; Tue, 13 Jan 2026 10:14:43 +0000 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 13 Jan 2026 04:14:43 -0600 Received: from [10.136.46.14] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Tue, 13 Jan 2026 02:14:39 -0800 Message-ID: <531cd86a-0737-40bc-a504-a016a64464f8@amd.com> Date: Tue, 13 Jan 2026 15:44:38 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] sched/clock: Avoid false sharing for sched_clock_irqtime To: Peter Zijlstra , Wangyang Guo CC: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , , Shrikanth Hegde , Benjamin Lei , Tim Chen , Tianyou Li References: <20260113074807.3404180-1-wangyang.guo@intel.com> <20260113100755.GV830755@noisy.programming.kicks-ass.net> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20260113100755.GV830755@noisy.programming.kicks-ass.net> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jan 2026 10:14:43.9662 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 724639f7-f6ab-4f01-a626-08de528c9283 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH2PEPF00000143.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN5PR12MB9462 Hello Peter, On 1/13/2026 3:37 PM, Peter Zijlstra wrote: > On Tue, Jan 13, 2026 at 03:48:07PM +0800, Wangyang Guo wrote: >> Read-mostly sched_clock_irqtime may share the same cacheline with >> frequently updated nohz struct. Mark it as __read_mostly to avoid >> false sharing issue. >> > > Is there a reason that thing can't be a static_key or so? Yes, the exact case is stated in commit b9f2b29b9494 ("sched: Don't define sched_clock_irqtime as static key") https://lore.kernel.org/lkml/173961695743.10177.17683780278419896262.tip-bot2@tip-bot2/ -- Thanks and Regards, Prateek