tracing: Define new ftrace event "func_repeats"

The event aims to consolidate the function tracing record in the cases
when a single function is called number of times consecutively.

	while (cond)
		do_func();

This may happen in various scenarios (busy waiting for example).
The new ftrace event can be used to show repeated function events with
a single event and save space on the ring buffer

Link: https://lkml.kernel.org/r/20210415181854.147448-3-y.karadz@gmail.com

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index 4547ac59da61..251c819cf0c5 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -338,3 +338,25 @@ FTRACE_ENTRY(hwlat, hwlat_entry,
 		 __entry->nmi_total_ts,
 		 __entry->nmi_count)
 );
+
+#define FUNC_REPEATS_GET_DELTA_TS(entry)				\
+	(((u64)(entry)->top_delta_ts << 32) | (entry)->bottom_delta_ts)	\
+
+FTRACE_ENTRY(func_repeats, func_repeats_entry,
+
+	TRACE_FUNC_REPEATS,
+
+	F_STRUCT(
+		__field(	unsigned long,	ip		)
+		__field(	unsigned long,	parent_ip	)
+		__field(	u16	,	count		)
+		__field(	u16	,	top_delta_ts	)
+		__field(	u32	,	bottom_delta_ts	)
+	),
+
+	F_printk(" %ps <-%ps\t(repeats:%u  delta: -%llu)",
+		 (void *)__entry->ip,
+		 (void *)__entry->parent_ip,
+		 __entry->count,
+		 FUNC_REPEATS_GET_DELTA_TS(__entry))
+);