Re: [PATCH] sched_ext: Add trace point to track sched_ext core events

[Andrea Righi <arighi@nvidia.com>]

Hi Changwoo,

On Wed, Feb 26, 2025 at 11:33:27PM +0900, Changwoo Min wrote:
> Add tracing support, which may be useful for debugging sched_ext schedulers
> that trigger a certain event.
> 
> Signed-off-by: Changwoo Min <changwoo@igalia.com>
> ---
>  include/trace/events/sched_ext.h | 21 +++++++++++++++++++++
>  kernel/sched/ext.c               |  4 ++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/include/trace/events/sched_ext.h b/include/trace/events/sched_ext.h
> index fe19da7315a9..88527b9316de 100644
> --- a/include/trace/events/sched_ext.h
> +++ b/include/trace/events/sched_ext.h
> @@ -26,6 +26,27 @@ TRACE_EVENT(sched_ext_dump,
>  	)
>  );
>  
> +TRACE_EVENT(sched_ext_add_event,
> +	    TP_PROTO(const char *name, int offset, __u64 added),
> +	    TP_ARGS(name, offset, added),
> +
> +	TP_STRUCT__entry(
> +		__string(name, name)
> +		__field(	int,		offset		)
> +		__field(	__u64,		added		)
> +	),
> +
> +	TP_fast_assign(
> +		__assign_str(name);
> +		__entry->offset		= offset;
> +		__entry->added		= added;
> +	),
> +
> +	TP_printk("name %s offset %d added %llu",
> +		  __get_str(name), __entry->offset, __entry->added
> +	)
> +);

Isn't the name enough to determine which event has been triggered? What are
the benefits of reporting also the offset within struct scx_event_stats?

Thanks,
-Andrea

> +
>  #endif /* _TRACE_SCHED_EXT_H */
>  
>  /* This part must be outside protection */
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 986b655911df..825e79863057 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -1554,6 +1554,8 @@ static DEFINE_PER_CPU(struct scx_event_stats, event_stats_cpu);
>   */
>  #define scx_add_event(name, cnt) do {						\
>  	this_cpu_add(event_stats_cpu.name, cnt);				\
> +	trace_sched_ext_add_event(#name,					\
> +				  offsetof(struct scx_event_stats, name), cnt);	\
>  } while(0)
>  
>  /**
> @@ -1565,6 +1567,8 @@ static DEFINE_PER_CPU(struct scx_event_stats, event_stats_cpu);
>   */
>  #define __scx_add_event(name, cnt) do {						\
>  	__this_cpu_add(event_stats_cpu.name, cnt);				\
> +	trace_sched_ext_add_event(#name,					\
> +				  offsetof(struct scx_event_stats, name), cnt);	\
>  } while(0)
>  
>  /**
> -- 
> 2.48.1
>