Commit 71d07880 authored Mar 04, 2025 by Changwoo Min Committed by Tejun Heo Mar 04, 2025

sched_ext: Add trace point to track sched_ext core events



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@igalia.com>
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent 038730dc

include/trace/events/sched_ext.h

+19 −0

Original line number	Diff line number	Diff line
		@@ -26,6 +26,25 @@ TRACE_EVENT(sched_ext_dump,
		)
		);

		TRACE_EVENT(sched_ext_event,
		TP_PROTO(const char *name, __s64 delta),
		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 */

kernel/sched/ext.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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)

		/**