Commit d6fcd28f authored by Tomas Glozar's avatar Tomas Glozar Committed by Steven Rostedt (Google)
Browse files

rtla: Count missed trace events 

Add function collect_missed_events to trace.c to act as a callback for
tracefs_follow_missed_events, summing the number of total missed events
into a new field missing_events of struct trace_instance.

In case record->missed_events is negative, trace->missed_events is set
to UINT64_MAX to signify an unknown number of events was missed.

The callback is activated on initialization of the trace instance.

Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/20250123142339.990300-2-tglozar@redhat.com


Signed-off-by: default avatarTomas Glozar <tglozar@redhat.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent b91cfd9f

tools/tracing/rtla/src/trace.c

+34 −0
Original line number Diff line number Diff line
@@ -126,6 +126,31 @@ collect_registered_events(struct tep_event *event, struct tep_record *record, 
	return 0;

}



/*

 * collect_missed_events - record number of missed events

 *

 * If rtla cannot keep up with events generated by tracer, events are going

 * to fall out of the ring buffer.

 * Collect how many events were missed so it can be reported to the user.

 */

static int

collect_missed_events(struct tep_event *event, struct tep_record *record,

		      int cpu, void *context)

{

	struct trace_instance *trace = context;



	if (trace->missed_events == UINT64_MAX)

		return 0;



	if (record->missed_events > 0)

		trace->missed_events += record->missed_events;

	else

		/* Events missed but no data on how many */

		trace->missed_events = UINT64_MAX;



	return 0;

}



/*

 * trace_instance_destroy - destroy and free a rtla trace instance

 */
@@ -181,6 +206,15 @@ int trace_instance_init(struct trace_instance *trace, char *tool_name) 
	 */

	tracefs_trace_off(trace->inst);



	/*

	 * Collect the number of events missed due to tracefs buffer

	 * overflow.

	 */

	trace->missed_events = 0;

	tracefs_follow_missed_events(trace->inst,

				     collect_missed_events,

				     trace);



	return 0;



out_err:

tools/tracing/rtla/src/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ struct trace_instance { 
	struct tracefs_instance		*inst;

	struct tep_handle		*tep;

	struct trace_seq		*seq;

	unsigned long long		missed_events;

};



int trace_instance_init(struct trace_instance *trace, char *tool_name);