linux-kernel - Re: [PATCH v2 1/1] tracing/sched: add 'next_policy' to trace_sched

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Message-ID: <20250912103050.5bf82967@gandalf.local.home>
Date: Fri, 12 Sep 2025 10:30:50 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Xiang Gao <gxxa03070307@...il.com>
Cc: mhiramat@...nel.org, mingo@...hat.com, peterz@...radead.org,
 juri.lelli@...hat.com, vincent.guittot@...aro.org,
 mathieu.desnoyers@...icios.com, andrii@...nel.org, mingo@...nel.org,
 oleg@...hat.com, akpm@...ux-foundation.org, gmonaco@...hat.com,
 ricardo.neri-calderon@...ux.intel.com, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, gaoxiang17 <gaoxiang17@...omi.com>
Subject: Re: [PATCH v2 1/1] tracing/sched: add 'next_policy' to
 trace_sched_switch

On Tue, 26 Aug 2025 20:48:54 +0800
Xiang Gao <gxxa03070307@...il.com> wrote:

> From: gaoxiang17 <gaoxiang17@...omi.com>
> 
> Sometimes, when analyzing some real-time process issues, it is necessary to know the sched policy.
> 
> Show up in the trace as:
> 
> 	 72.267374: sched_switch: prev_comm=grep prev_pid=67 prev_prio=19 prev_state=S ==> next_comm=cat next_pid=66 next_prio=120 next_policy=normal
> 	 72.267594: sched_switch: prev_comm=cat prev_pid=66 prev_prio=120 prev_state=R+ ==> next_comm=grep next_pid=67 next_prio=19 next_policy=RR
> 	562.192567: sched_switch: prev_comm=grep prev_pid=85 prev_prio=19 prev_state=S ==> next_comm=cat next_pid=84 next_prio=120 next_policy=normal
> 	562.192944: sched_switch: prev_comm=cat prev_pid=84 prev_prio=120 prev_state=R+ ==> next_comm=grep next_pid=85 next_prio=19 next_policy=FIFO
> 

Peter,

Are you OK with extending the sched switch tracepoint?

-- Steve

> Signed-off-by: gaoxiang17 <gaoxiang17@...omi.com>
> ---
>  include/trace/events/sched.h | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index 7b2645b50e78..00336211aca6 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -234,6 +234,7 @@ TRACE_EVENT(sched_switch,
>  		__array(	char,	next_comm,	TASK_COMM_LEN	)
>  		__field(	pid_t,	next_pid			)
>  		__field(	int,	next_prio			)
> +		__field(	unsigned int,	next_policy	)
>  	),
>  
>  	TP_fast_assign(
> @@ -244,10 +245,11 @@ TRACE_EVENT(sched_switch,
>  		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
>  		__entry->next_pid	= next->pid;
>  		__entry->next_prio	= next->prio;
> +		__entry->next_policy	= next->policy;
>  		/* XXX SCHED_DEADLINE */
>  	),
>  
> -	TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==> next_comm=%s next_pid=%d next_prio=%d",
> +	TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==> next_comm=%s next_pid=%d next_prio=%d next_policy=%s",
>  		__entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
>  
>  		(__entry->prev_state & (TASK_REPORT_MAX - 1)) ?
> @@ -263,7 +265,16 @@ TRACE_EVENT(sched_switch,
>  		  "R",
>  
>  		__entry->prev_state & TASK_REPORT_MAX ? "+" : "",
> -		__entry->next_comm, __entry->next_pid, __entry->next_prio)
> +		__entry->next_comm, __entry->next_pid, __entry->next_prio,
> +		__print_symbolic(__entry->next_policy,
> +				{ SCHED_NORMAL,         "normal" },
> +				{ SCHED_FIFO,           "FIFO" },
> +				{ SCHED_RR,             "RR" },
> +				{ SCHED_BATCH,          "batch" },
> +				{ SCHED_IDLE,           "idle" },
> +				{ SCHED_DEADLINE,       "deadline" },
> +				{ SCHED_EXT,            "sched_ext"})
> +	)
>  );
>  
>  /*