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client-ip=165.204.84.17; helo=SATLEXMB03.amd.com; pr=C Received: from SATLEXMB03.amd.com (165.204.84.17) by SN1PEPF00036F43.mail.protection.outlook.com (10.167.248.27) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.9052.8 via Frontend Transport; Thu, 21 Aug 2025 08:44:08 +0000 Received: from Satlexmb09.amd.com (10.181.42.218) by SATLEXMB03.amd.com (10.181.40.144) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Thu, 21 Aug 2025 03:44:04 -0500 Received: from SATLEXMB03.amd.com (10.181.40.144) by satlexmb09.amd.com (10.181.42.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.1748.10; Thu, 21 Aug 2025 01:44:03 -0700 Received: from [172.31.184.125] (10.180.168.240) by SATLEXMB03.amd.com (10.181.40.144) with Microsoft SMTP Server id 15.1.2507.39 via Frontend Transport; Thu, 21 Aug 2025 03:44:00 -0500 Message-ID: <47c67022-427c-4c24-8dcf-a3721f8c5bdd@amd.com> Date: Thu, 21 Aug 2025 14:13:54 +0530 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] sched: Add task enqueue/dequeue trace points To: Nam Cao , Peter Zijlstra CC: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Gabriele Monaco , , , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , "Phil Auld" References: <20250815134016.GB3289052@noisy.programming.kicks-ass.net> <20250815135212.GA1386988@noisy.programming.kicks-ass.net> <20250821070504.-ZhqdfHs@linutronix.de> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20250821070504.-ZhqdfHs@linutronix.de> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Aug 2025 08:44:08.0801 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7ad23782-ef42-46fa-b9fe-08dde08ee495 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=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF00036F43.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB7126 Hello Nam, On 8/21/2025 12:35 PM, Nam Cao wrote: >>> How about something like: >>> >>> dequeue_task(): >>> ... >>> ret = p->sched_class->dequeue_task(rq, p, flags); >>> if (trace_dequeue_task_p_enabled() && !(flags & DEQUEUE_SLEEP)) >>> __trace_dequeue_task_tp(rq->cpu, p); >>> return ret; >>> >>> >>> __block_task(): >>> trace_dequeue_task_tp(rq->cpu, p); >>> ... >>> >>> >>> Specifically, only DEQUEUE_SLEEP is allowed to fail, and DEQUEUE_SLEEP >>> will eventually cause __block_task() to be called, either directly, or >>> delayed. >> >> If you extend the tracepoint with the sleep state, you can probably >> remove the nr_running tracepoints. Esp. once we get this new throttle >> stuff sorted. > > Sorry, I'm a bit out of depth here. Can you elaborate? > > By "sleep state" do you mean (flags & DEQUEUE_SLEEP)? The nr_running > tracepoints are not hit if the task is throttled, while these new > tracepoints are hit. How does the sleep state help with this difference? Once we have per-task throttling being discussed in https://lore.kernel.org/lkml/20250715071658.267-1-ziqianlu@bytedance.com/ throttled tasks will do a dequeue_task_fair(rq, p, DEQUEUE_SLEEP | DEQUEUE_THROTTLE); and remove themselves from the runqueue but they won't hit block_task(). To preserve current throttle behavior, I don't think per-task throttle should call dequeue_task() directly since it does a bunch more stuff with core-sched dequeue, psi, uclamp, etc or maybe it is fine to do that now with per-task throttling? Peter, what do you think? If we don't what to do all that stuff in the throttle path, adding to Peter's suggestion, perhaps we can have a wrapper like: int __dequeue_task(rq, p, flags) int ret = p->sched_class->dequeue_task(rq, p, flags); if (trace_dequeue_task_p_enabled() && !((flags & (DEQUEUE_SLEEP | DEQUEUE_THROTTLE)) == DEQUEUE_SLEEP)) __trace_dequeue_task_tp(rq->cpu, p); return ret; and then per-task throttle can just call __dequeue_task() instead. I'll let Peter chime in with his thoughts. > > Also +Cc Phil Auld , who seems to care about the > nr_running tracepoints. > > Nam -- Thanks and Regards, Prateek