linux-kernel - Re: [RFC PATCH V3] sched: psi: Add psi events trace point

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Message-ID: <CAB8ipk-xqbsNh6EQ42JFV8CqPeJR0gjObOKvSs=-b=qcuLQxfg@mail.gmail.com>
Date: Tue, 23 Sep 2025 10:58:23 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Xuewen Yan <xuewen.yan@...soc.com>
Cc: surenb@...gle.com, hannes@...xchg.org, mathieu.desnoyers@...icios.com, 
	mhiramat@...nel.org, peterz@...radead.org, rostedt@...dmis.org, 
	mingo@...hat.com, vincent.guittot@...aro.org, dietmar.eggemann@....com, 
	bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	ke.wang@...soc.com, yuming.han@...soc.com
Subject: Re: [RFC PATCH V3] sched: psi: Add psi events trace point

A very gentle ping on this patch.
Best regards,
Thanks!

On Thu, Sep 11, 2025 at 11:30 AM Xuewen Yan <xuewen.yan@...soc.com> wrote:
>
> Add trace point to psi triggers. This is useful to
> observe the psi events in the kernel space.
>
> One use of this is to monitor memory pressure.
> When the pressure is too high, we can kill the process
> in the kernel space to prevent OOM.
>
> Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
> ---
> V3:
> -export it in the tracefs;
> ---
> v2:
> -fix compilation error;
> -export the tp;
> -add more commit message;
> ---
>  include/trace/events/sched.h | 27 +++++++++++++++++++++++++++
>  kernel/sched/psi.c           |  4 ++++
>  2 files changed, 31 insertions(+)
>
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index 7b2645b50e78..db8b8f25466e 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -826,6 +826,33 @@ TRACE_EVENT(sched_wake_idle_without_ipi,
>         TP_printk("cpu=%d", __entry->cpu)
>  );
>
> +#ifdef CONFIG_PSI
> +TRACE_EVENT(psi_event,
> +
> +       TP_PROTO(int aggregator, int state, u64 threshold, u64 win_size),
> +
> +       TP_ARGS(aggregator, state, threshold, win_size),
> +
> +       TP_STRUCT__entry(
> +               __field(int,    aggregator)
> +               __field(int,    state)
> +               __field(u64,    threshold)
> +               __field(u64,    win_size)
> +       ),
> +
> +       TP_fast_assign(
> +               __entry->aggregator     = aggregator;
> +               __entry->state          = state;
> +               __entry->threshold      = threshold;
> +               __entry->win_size       = win_size;
> +       ),
> +
> +       TP_printk("aggregator=%d state=%d threshold=%llu window_size=%llu",
> +               __entry->aggregator, __entry->state, __entry->threshold,
> +               __entry->win_size)
> +);
> +#endif /* CONFIG_PSI */
> +
>  /*
>   * Following tracepoints are not exported in tracefs and provide hooking
>   * mechanisms only for testing and debugging purposes.
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 59fdb7ebbf22..5b7954b653ed 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -141,6 +141,8 @@
>  #include <linux/psi.h>
>  #include "sched.h"
>
> +EXPORT_TRACEPOINT_SYMBOL_GPL(psi_event);
> +
>  static int psi_bug __read_mostly;
>
>  DEFINE_STATIC_KEY_FALSE(psi_disabled);
> @@ -509,6 +511,8 @@ static void update_triggers(struct psi_group *group, u64 now,
>                 if (now < t->last_event_time + t->win.size)
>                         continue;
>
> +               trace_psi_event(aggregator, t->state, t->threshold, t->win.size);
> +
>                 /* Generate an event */
>                 if (cmpxchg(&t->event, 0, 1) == 0) {
>                         if (t->of)
> --
> 2.25.1
>