Re: [PATCH v5 09/15] sched: Add task enqueue/dequeue trace points

[Gabriele Monaco]

2026-01-22T15:56:08Z Gabriele Monaco <gmonaco@xxxxxxxxxx>:

> From: Nam Cao <namcao@xxxxxxxxxxxxx>
>
> Add trace points into enqueue_task() and dequeue_task().
>

Peter,

can I have your Ack on this?

(Apologies for the spam, I sent it as HTML by mistake)

Thanks,
Gabriele

> Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
> Reviewed-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> Signed-off-by: Gabriele Monaco <gmonaco@xxxxxxxxxx>
> ---
>
> Notes:
>     V5:
>     * Do not fire enqueue tracepoint for delayed enqueues
>
> include/trace/events/sched.h | 13 +++++++++++++
> kernel/sched/core.c          | 10 +++++++++-
> kernel/sched/sched.h         |  2 ++
> 3 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index 366b2e8ec40c..f4e1d3554e3e 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -912,6 +912,19 @@ DECLARE_TRACE(sched_dl_server_stop,
>     TP_PROTO(struct sched_dl_entity *dl_se, int cpu),
>     TP_ARGS(dl_se, cpu));
>
> +/*
> + * The two trace points below may not work as expected for fair tasks due
> + * to delayed dequeue. See:
> + * https://lore.kernel.org/lkml/179674c6-f82a-4718-ace2-67b5e672fdee@xxxxxxx/
> + */
> +DECLARE_TRACE(sched_enqueue,
> +   TP_PROTO(struct task_struct *tsk, int cpu),
> +   TP_ARGS(tsk, cpu));
> +
> +DECLARE_TRACE(sched_dequeue,
> +   TP_PROTO(struct task_struct *tsk, int cpu),
> +   TP_ARGS(tsk, cpu));
> +
> #endif /* _TRACE_SCHED_H */
>
> /* This part must be outside protection */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index f6293fa02fb7..c885d7885172 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2087,6 +2087,9 @@ unsigned long get_wchan(struct task_struct *p)
>
> void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
> {
> +   if (trace_sched_enqueue_tp_enabled() && !(flags & ENQUEUE_DELAYED))
> +       trace_sched_enqueue_tp(p, rq->cpu);
> +
>     if (!(flags & ENQUEUE_NOCLOCK))
>         update_rq_clock(rq);
>
> @@ -2114,6 +2117,8 @@ 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)
> {
> +   int ret;
> +
>     if (sched_core_enabled(rq))
>         sched_core_dequeue(rq, p, flags);
>
> @@ -2131,7 +2136,10 @@ inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
>      */
>     uclamp_rq_dec(rq, p);
>     rq->queue_mask |= p->sched_class->queue_mask;
> -   return p->sched_class->dequeue_task(rq, p, flags);
> +   ret = p->sched_class->dequeue_task(rq, p, flags);
> +   if (trace_sched_dequeue_tp_enabled() && !(flags & DEQUEUE_SLEEP))
> +       trace_sched_dequeue_tp(p, rq->cpu);
> +   return ret;
> }
>
> void activate_task(struct rq *rq, struct task_struct *p, int flags)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index e885a935b716..8465472b40fa 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2918,6 +2918,8 @@ static inline void sub_nr_running(struct rq *rq, unsigned count)
>
> static inline void __block_task(struct rq *rq, struct task_struct *p)
> {
> +   trace_sched_dequeue_tp(p, rq->cpu);
> +
>     if (p->sched_contributes_to_load)
>         rq->nr_uninterruptible++;
>
> --
> 2.52.0