Re: [PATCH v3 2/2] sched_ext: Add trace point to track sched_ext core events

[Changwoo Min]

Hi Andrea,

On 25. 3. 4. 15:41, Andrea Righi wrote:
> Hi Changwoo,
>
> On Tue, Mar 04, 2025 at 10:27:40AM +0900, Changwoo Min wrote:
> > Add tracing support to track sched_ext core events
> > (/sched_ext/sched_ext_event). This may be useful for debugging sched_ext
> > schedulers that trigger a particular event.
> >
> > The trace point can be used as other trace points, so it can be used in,
> > for example, `perf trace` and BPF programs, as follows:
> >
> > ======
> > $> sudo perf trace -e sched_ext:sched_ext_event --filter 'name == "SCX_EV_ENQ_SLICE_DFL"'
> > ======
> >
> > ======
> > struct tp_sched_ext_event {
> > 	struct trace_entry ent;
> > 	u32 __data_loc_name;
> > 	s64 delta;
> > };
> >
> > SEC("tracepoint/sched_ext/sched_ext_event")
> > int rtp_add_event(struct tp_sched_ext_event *ctx)
> > {
> > 	char event_name[128];
> > 	unsigned short offset = ctx->__data_loc_name & 0xFFFF;
> >          bpf_probe_read_str((void *)event_name, 128, (char *)ctx + offset);
> >
> > 	bpf_printk("name %s   delta %lld", event_name, ctx->delta);
> > 	return 0;
> > }
> > ======
> >
> > Signed-off-by: Changwoo Min <changwoo@xxxxxxxxxx>
> > ---
> >   include/trace/events/sched_ext.h | 19 +++++++++++++++++++
> >   kernel/sched/ext.c               |  2 ++
> >   2 files changed, 21 insertions(+)
> >
> > diff --git a/include/trace/events/sched_ext.h b/include/trace/events/sched_ext.h
> > index fe19da7315a9..3d04b9819548 100644
> > --- a/include/trace/events/sched_ext.h
> > +++ b/include/trace/events/sched_ext.h
> > @@ -26,6 +26,25 @@ TRACE_EVENT(sched_ext_dump,
> >   	)
> >   );
> >   
> > +TRACE_EVENT(sched_ext_event,
> > +	    TP_PROTO(const char *name, __u64 delta),
>
> It shouldn't be __s64 here as well?

Ah, my bad. Thank you for catching this!

> Thanks,
> -Andrea
>
> > +	    TP_ARGS(name, delta),
> > +
> > +	TP_STRUCT__entry(
> > +		__string(name, name)
> > +		__field(	__s64,		delta		)
> > +	),
> > +
> > +	TP_fast_assign(
> > +		__assign_str(name);
> > +		__entry->delta		= delta;
> > +	),
> > +
> > +	TP_printk("name %s delta %lld",
> > +		  __get_str(name), __entry->delta
> > +	)
> > +);
> > +
> >   #endif /* _TRACE_SCHED_EXT_H */
> >   
> >   /* This part must be outside protection */
> > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> > index 686629a860f3..debcd1cf2de9 100644
> > --- a/kernel/sched/ext.c
> > +++ b/kernel/sched/ext.c
> > @@ -1554,6 +1554,7 @@ 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_event(#name, cnt);					\
> >   } while(0)
> >   
> >   /**
> > @@ -1565,6 +1566,7 @@ 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_event(#name, cnt);					\
> >   } while(0)
> >   
> >   /**
> > --
> > 2.48.1