rtla: Add function to report missed events

Add osnoise_report_missed_events to be used to report the number
of missed events either during or after an osnoise or timerlat run.
Also, display the percentage of missed events compared to the total
number of received events.

If an unknown number of missed events was reported during the run, the
entire number of missed events is reported as unknown.

Cc: John Kacur <[email protected]>
Cc: Luis Goncalves <[email protected]>
Cc: Gabriele Monaco <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Tomas Glozar <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: lenticularis39

tools/tracing/rtla/src/osnoise.c

@@ -1095,6 +1095,26 @@ bool osnoise_trace_is_off(struct osnoise_tool *tool, struct osnoise_tool *record
 	return record && !tracefs_trace_is_on(record->trace.inst);
 }
 
+/*
+ * osnoise_report_missed_events - report number of events dropped by trace
+ * buffer
+ */
+void
+osnoise_report_missed_events(struct osnoise_tool *tool)
+{
+	unsigned long long total_events;
+
+	if (tool->trace.missed_events == UINT64_MAX)
+		printf("unknown number of events missed, results might not be accurate\n");
+	else if (tool->trace.missed_events > 0) {
+		total_events = tool->trace.processed_events + tool->trace.missed_events;
+
+		printf("%lld (%.2f%%) events missed, results might not be accurate\n",
+		       tool->trace.missed_events,
+		       (double) tool->trace.missed_events / total_events * 100.0);
+	}
+}
+
 static void osnoise_usage(int err)
 {
 	int i;

tools/tracing/rtla/src/osnoise.h

@@ -104,6 +104,7 @@ struct osnoise_tool {
 void osnoise_destroy_tool(struct osnoise_tool *top);
 struct osnoise_tool *osnoise_init_tool(char *tool_name);
 struct osnoise_tool *osnoise_init_trace_tool(char *tracer);
+void osnoise_report_missed_events(struct osnoise_tool *tool);
 bool osnoise_trace_is_off(struct osnoise_tool *tool, struct osnoise_tool *record);
 
 int osnoise_hist_main(int argc, char *argv[]);