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:
> > 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
>
> Nam
>
> diff --git a/include/trace/events/sched.h
> b/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, struct
> task_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);
>
