Normalize jitter value for the server histogram

packet-exchange/src/server.c

@@ -40,6 +40,7 @@ typedef struct thread_stat {
 } thread_stat_t;
 
 typedef struct thread_param {
+  int interval;
   int priority;
 
   thread_stat_t stats;
@@ -82,13 +83,14 @@ struct timespec measures_start;
 struct timespec measures_end;
 
 static void help(char *argv[]) {
-  printf("Usage: %s [-aghtv] [-b CLIENT_IP] [-d BUF_LEN] [-f IF] [-p PRIO] [-r USEC]\n\n", argv[0]);
+  printf("Usage: %s [-aghtv] [-b CLIENT_IP] [-d BUF_LEN] [-f IF] [-i USEC] [-p PRIO] [-r USEC]\n\n", argv[0]);
   printf("       -a                    Run the real time thread on CPU1\n");
   printf("       -b CLIENT_IP          Server side RTT\n");
   printf("       -d BUF_LEN            Set the length of tx buffer\n");
   printf("       -f IF                 Set the network interface to be used\n");
   printf("       -g                    Print histograms to sdtout on exit\n");
   printf("       -h                    Show help\n");
+  printf("       -i USEC               Wake up the real time thread every USEC microseconds (Default: 10ms)\n");
   printf("       -p PRIO               Run the real time thread at priority PRIO\n");
   printf("       -r USEC               Refresh the non real time main thread every USEC microseconds\n");
   printf("       -t                    Enable timestamps\n");
@@ -105,6 +107,7 @@ static void *packet_receiving_thread(void *p) {
   thread_stat_t *stats = &param->stats;
   uint64_t diff = 0;
   cpu_set_t mask;
+  int64_t dist_to_interval;
 
   stats->min_interval = UINT64_MAX;
   stats->max_interval = 0;
@@ -142,12 +145,16 @@ static void *packet_receiving_thread(void *p) {
         stats->min_interval = diff < stats->min_interval ? diff : stats->min_interval;
         stats->max_interval = diff > stats->max_interval ? diff : stats->max_interval;
 
-        if( diff > MAX_HIST_VAL * 1000 ) {
-          fprintf(stderr, "jitter higher than MAX_HIST_VAL\n");
-          exit(EXIT_FAILURE);
-        }
-        else {
-          histograms[2][diff / 1000] = diff / 1000;
+        if(enable_histograms) {
+          dist_to_interval = (diff - param->interval) / 1000;
+          dist_to_interval += MAX_HIST_VAL / 2;
+          if( dist_to_interval > ((int)MAX_HIST_VAL) || dist_to_interval < 0 ) {
+            fprintf(stderr, "jitter higher than MAX_HIST_VAL\n");
+            exit(EXIT_FAILURE);
+          }
+          else {
+            histograms[2][dist_to_interval]++;
+          }
         }
       }
 
@@ -172,6 +179,7 @@ int main(int argc, char *argv[]) {
   stats = &param->stats;
 
   // Default configuration values
+  param->interval = 100000 * 1000;
   param->priority = 99;
 
   enable_affinity = 0;
@@ -243,7 +251,7 @@ static void print_histograms() {
   duration_hour = duration / NSEC_PER_SEC / 3600;
   duration_minutes = duration / NSEC_PER_SEC / 60 - duration_hour * 60;
 
-  interval = (param->stats.min_interval + param->stats.max_interval) / 2 / 1000;
+  interval = param->interval / 1000;
 
   printf("{\"measure_sets\": [{"
              "\"measure_type\": \"packet_recv_timestamps\","
@@ -268,21 +276,28 @@ static void print_histograms() {
     printf("%s", (i + 1 < 2 ? "], " : "]"));
   }
 
+  max_hist_val = 0;
+  for (int j = 0; j < MAX_HIST_VAL && histograms[2][j]; j++)
+    max_hist_val = j;
+  min_hist_val = 0;
+  for (int j = MAX_HIST_VAL - 1; j >= 0 && histograms[2][j]; j--)
+    min_hist_val = j;
+
   printf(   "]}, {"
              "\"measure_type\": \"packet_jitter\","
              "\"props_names\": [\"jitter\"],"
              "\"units\": [\"us\"],"
              "\"props_type\": \"histogram\","
+             "\"middle\": \"%d\","
              "\"metadata\": {"
                 "\"i\": \"%dus\", \"duration\": \"%dh%d\""
                 "},"
-             "\"props\": [[", interval, duration_hour, duration_minutes);
+             "\"props\": [[", interval,
+                              MAX_HIST_VAL / 2 - min_hist_val,
+                              duration_hour,
+                              duration_minutes);
 
-  max_hist_val = 0;
-  for (int j = 0; j < MAX_HIST_VAL && histograms[2][j]; j++)
-    max_hist_val = j;
-
-  for (int j = 0; j < max_hist_val; j++)
+  for (int j = min_hist_val; j < max_hist_val; j++)
     printf("%" PRIi64 "%s", histograms[2][j], (j + 1 < max_hist_val ? ", " : ""));
 
   printf(   "]]}]}\n");
@@ -330,6 +345,9 @@ static void process_options(int argc, char *argv[]) {
       help(argv);
       exit(EXIT_SUCCESS);
       break;
+    case 'i':
+      param->interval = atoi(optarg) * 1000;
+      break;
     case 'g':
       enable_histograms = 1;
       break;

packet-exchange/src/utilities.h

@@ -10,8 +10,8 @@
 #define NSEC_PER_SEC UINT64_C(1000000000)
 #define SERVER_PORT "50000"
 #define SERVER_PORT_INT 50000
-#define MAX_HIST_VAL 1000
-#define NB_HISTOGRAMS 2
+#define MAX_HIST_VAL 2000
+#define NB_HISTOGRAMS 3
 
 typedef struct packet_timestamps {
   uint64_t enter_user_space;