Re: [PATCH 4/5] sched: Add rt task enqueue/dequeue trace points
From: Gabriele Monaco <gmonaco@redhat.com>
Date: 2025-07-31 08:39:32
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On Thu, 2025-07-31 at 09:35 +0200, Nam Cao wrote:
On Wed, Jul 30, 2025 at 06:18:45PM +0200, Gabriele Monaco wrote:quoted
Well, thinking about it again, these tracepoints might simplify things considerably when tasks change policy.. Syscalls may fail, for that you could register to sys_exit and check the return value, but at that point the policy changed already, so you cannot tell if it's a relevant event or not (e.g. same policy). Also sched_setscheduler_nocheck would be out of the picture here, not sure how recurrent that is though (and might not matter if you only focus on userspace tasks). If you go down the route of adding tracepoints, why not have other classes benefit too? I believe calling them from the enqueue_task / dequeue_task in sched/core.c would allow you to easily filter out by policy anyway (haven't tested).Something like the untested patch below? Will you have a use case for it too? Then I will try to accommodate your use case, otherwise I will do just enough for my case.
Well, I'm still defining the best set of tracepoints I need, if you see it cleaner go ahead the way you're currently doing, then. Unless anyone else complains let's keep it like this. Thanks, Gabriele
quoted hunk ↗ jump to hunk
Namdiff --git a/include/trace/events/sched.hb/include/trace/events/sched.h index c38f12f7f903..b50668052f99 100644--- a/include/trace/events/sched.h +++ b/include/trace/events/sched.h@@ -906,6 +906,14 @@ DECLARE_TRACE(dequeue_task_rt,TP_PROTO(int cpu, struct task_struct *task), TP_ARGS(cpu, task)); +DECLARE_TRACE(enqueue_task, + TP_PROTO(int cpu, struct task_struct *task), + TP_ARGS(cpu, task)); + +DECLARE_TRACE(dequeue_task, + TP_PROTO(int cpu, struct task_struct *task), + TP_ARGS(cpu, task)); + #endif /* _TRACE_SCHED_H */ /* This part must be outside protection */diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b485e0639616..2af90532982a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c@@ -2077,6 +2077,8 @@ unsigned long get_wchan(struct task_struct *p)void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { + trace_enqueue_task_tp(rq->cpu, p); + if (!(flags & ENQUEUE_NOCLOCK)) update_rq_clock(rq);@@ -2103,6 +2105,8 @@ void enqueue_task(struct rq *rq, structtask_struct *p, int flags) */ inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags) { + trace_dequeue_task_tp(rq->cpu, p); + if (sched_core_enabled(rq)) sched_core_dequeue(rq, p, flags);