[PATCH] rtla/osnoise: Better report when histogram is empty

[Luis Claudio R. Goncalves]

When osnoise hist does not observe any samples above the threshold,
no entries are recorded and the final report shows empty entries
for the usual statistics (count, min, max, avg):

    [~]# osnoise hist -d 5s -T 500
    # RTLA osnoise histogram
    # Time unit is microseconds (us)
    # Duration:   0 00:00:05
    Index
    over: 
    count:
    min:  
    avg:  
    max:  

That could lead users to confusing interpretations of the results.

A simple solution is to report 0 for count and the statistics, making it
clear that no noise (above the defined threshold) was observed:

    [~]# osnoise hist -d 5s -T 500
    # RTLA osnoise histogram
    # Time unit is microseconds (us)
    # Duration:   0 00:00:05
    Index
    over: 0
    count: 0
    min: 0
    avg: 0
    max: 0


Signed-off-by: Luis Claudio R. Goncalves <lgonc...@redhat.com>
---
 tools/tracing/rtla/src/osnoise_hist.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/tracing/rtla/src/osnoise_hist.c 
b/tools/tracing/rtla/src/osnoise_hist.c
index 7be17d09f7e85..214e2c93fde01 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -374,6 +374,7 @@ osnoise_print_stats(struct osnoise_hist_params *params, 
struct osnoise_tool *too
 {
        struct osnoise_hist_data *data = tool->data;
        struct trace_instance *trace = &tool->trace;
+       int has_samples = 0;
        int bucket, cpu;
        int total;
 
@@ -402,11 +403,25 @@ osnoise_print_stats(struct osnoise_hist_params *params, 
struct osnoise_tool *too
                        continue;
                }
 
+               /* There are samples above the threshold */
+               has_samples = 1;
                trace_seq_printf(trace->seq, "\n");
                trace_seq_do_printf(trace->seq);
                trace_seq_reset(trace->seq);
        }
 
+       /*
+        * If no samples were recorded, skip calculations, print zeroed 
statistics
+        * and return.
+        */
+       if (!has_samples) {
+               trace_seq_reset(trace->seq);
+               trace_seq_printf(trace->seq, "over: 0\ncount: 0\nmin: 0\navg: 
0\nmax: 0\n");
+               trace_seq_do_printf(trace->seq);
+               trace_seq_reset(trace->seq);
+               return;
+       }
+
        if (!params->no_index)
                trace_seq_printf(trace->seq, "over: ");