gst-stats: sort latency by first activity before displaying

We use to display the latency of each element in random order which is
not very convenient when comparing latency between different runs.
Sort them by "first activity" (the first latency reported for each
element) so it's consistent betwen runs.

This is the same logic when sorting and displaying element stats.

tools/gst-stats.c

@@ -53,6 +53,8 @@ static gboolean have_element_reported_latency = FALSE;
 
 typedef struct
 {
+  /* display name of the element */
+  gchar *name;
   /* the number of latencies counted  */
   guint64 count;
   /* the total of all latencies */
@@ -61,6 +63,7 @@ typedef struct
   guint64 min;
   /* the max of all latencies */
   guint64 max;
+  GstClockTime first_latency_ts;
 } GstLatencyStats;
 
 typedef struct
@@ -121,11 +124,21 @@ typedef struct
 
 /* stats helper */
 
-static void
-latencies_foreach_print_stats (gchar * key, GstLatencyStats * ls, gpointer data)
+static gint
+sort_latency_stats_by_first_ts (gconstpointer a, gconstpointer b)
 {
+  const GstLatencyStats *ls1 = a, *ls2 = b;
+
+  return (GST_CLOCK_DIFF (ls2->first_latency_ts, ls1->first_latency_ts));
+}
+
+static void
+print_latency_stats (gpointer value, gpointer user_data)
+{
+  GstLatencyStats *ls = value;
+
   printf ("\t%s: mean=%" GST_TIME_FORMAT " min=%" GST_TIME_FORMAT " max=%"
-      GST_TIME_FORMAT "\n", key, GST_TIME_ARGS (ls->total / ls->count),
+      GST_TIME_FORMAT "\n", ls->name, GST_TIME_ARGS (ls->total / ls->count),
       GST_TIME_ARGS (ls->min), GST_TIME_ARGS (ls->max));
 }
 
@@ -140,6 +153,9 @@ reported_latencies_foreach_print_stats (GstReportedLatency * rl, gpointer data)
 static void
 free_latency_stats (gpointer data)
 {
+  GstLatencyStats *ls = data;
+
+  g_free (ls->name);
   g_slice_free (GstLatencyStats, data);
 }
 
@@ -475,17 +491,20 @@ do_proc_rusage_stats (GstStructure * s)
 }
 
 static void
-update_latency_table (GHashTable * table, const gchar * key, guint64 time)
+update_latency_table (GHashTable * table, const gchar * key, guint64 time,
+    GstClockTime ts)
 {
   /* Find the values in the hash table */
   GstLatencyStats *ls = g_hash_table_lookup (table, key);
   if (!ls) {
     /* Insert the new key if the value does not exist */
     ls = g_new0 (GstLatencyStats, 1);
+    ls->name = g_strdup (key);
     ls->count = 1;
     ls->total = time;
     ls->min = time;
     ls->max = time;
+    ls->first_latency_ts = ts;
     g_hash_table_insert (table, g_strdup (key), ls);
   } else {
     /* Otherwise update the existing value */
@@ -524,7 +543,7 @@ do_latency_stats (GstStructure * s)
       src, sink_element_id, sink_element, sink);
 
   /* Update the latency in the table */
-  update_latency_table (latencies, key, time);
+  update_latency_table (latencies, key, time, ts);
 
   /* Clean up */
   g_free (key);
@@ -553,7 +572,7 @@ do_element_latency_stats (GstStructure * s)
   key = g_strdup_printf ("%s.%s.%s", element_id, element, src);
 
   /* Update the latency in the table */
-  update_latency_table (element_latencies, key, time);
+  update_latency_table (element_latencies, key, time, ts);
 
   /* Clean up */
   g_free (key);
@@ -960,18 +979,28 @@ print_stats (void)
 
   /* latency stats */
   if (have_latency) {
+    GList *list = NULL;
+
     puts ("Latency Statistics:");
-    g_hash_table_foreach (latencies, (GHFunc) latencies_foreach_print_stats,
-        NULL);
+    list = g_hash_table_get_values (latencies);
+    /* Sort by first activity */
+    list = g_list_sort (list, sort_latency_stats_by_first_ts);
+    g_list_foreach (list, print_latency_stats, NULL);
     puts ("");
+    g_list_free (list);
   }
 
   /* element latency stats */
   if (have_element_latency) {
+    GList *list = NULL;
+
     puts ("Element Latency Statistics:");
-    g_hash_table_foreach (element_latencies,
-        (GHFunc) latencies_foreach_print_stats, NULL);
+    list = g_hash_table_get_values (element_latencies);
+    /* Sort by first activity */
+    list = g_list_sort (list, sort_latency_stats_by_first_ts);
+    g_list_foreach (list, print_latency_stats, NULL);
     puts ("");
+    g_list_free (list);
   }
 
   /* element reported latency stats */