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rtla: Count missed trace events

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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: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Tomas Glozar
2025-01-23 15:23:36 +01:00
committed by Steven Rostedt (Google)
parent b91cfd9f75
commit d6fcd28ffe
2 changed files with 35 additions and 0 deletions
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34
tools/tracing/rtla/src/trace.c
View File

@@ -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:

1
tools/tracing/rtla/src/trace.h
View File

@@ -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);