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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by BN2PEPF00004FC1.mail.protection.outlook.com (10.167.243.187) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9564.3 via Frontend Transport; Tue, 27 Jan 2026 03:38:39 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Mon, 26 Jan 2026 21:38:39 -0600 Received: from [10.136.38.16] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Mon, 26 Jan 2026 21:38:34 -0600 Message-ID: <95da1e97-bcfb-4a47-affc-fcec6e729d5b@amd.com> Date: Tue, 27 Jan 2026 09:08:32 +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 v5] sched/clock: Avoid false sharing for sched_clock_irqtime To: Wangyang Guo , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider CC: , Shrikanth Hegde , Benjamin Lei , Tim Chen , Tianyou Li References: <20260127031602.1907377-1-wangyang.guo@intel.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20260127031602.1907377-1-wangyang.guo@intel.com> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jan 2026 03:38:39.2127 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 60873f1a-9e43-4ce0-970a-08de5d558f64 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF00004FC1.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4068 Hello Wangyang, On 1/27/2026 8:46 AM, Wangyang Guo wrote: > @@ -238,6 +239,8 @@ static int __init sched_clock_init_late(void) > > if (__sched_clock_stable_early) > __set_sched_clock_stable(); > + else > + disable_sched_clock_irqtime(); /* disable if clock unstable. */ nit. I think we should check for irqtime_enabled() before since static_key_disable() would grab the cpus_read_lock() unnecessarily even if irqtime wasn't enabled - possible with PA-RISC where a slow processor registers the generic sched clock not eabling irqtime and then marks the sched_clock unstable on SMP which would hit this without having irqtime enabled. Same is case with "tsc=noirqtime" and then tsc turns unstable at early boot. -- Thanks and Regards, Prateek