Store max latency only and add a refresh option

.gitignore

@@ -2,3 +2,4 @@
 *.d
 simple-server/build/main
 simple-client/build/main
+latency-measure/build/main

latency-measure/src/main.c

@@ -15,7 +15,7 @@
 
 typedef struct thread_stat {
   int nb_cycles;
-  int64_t diff;
+  int64_t max_diff;
 } thread_stat_t;
 
 typedef struct thread_param {
@@ -25,6 +25,10 @@ typedef struct thread_param {
   thread_stat_t stat;
 } thread_param_t;
 
+typedef struct main_param {
+  int refresh_rate;
+} main_param_t;
+
 static inline int64_t diff_ns(struct timespec t1, struct timespec t2) {
   int64_t diff;
 
@@ -34,6 +38,10 @@ static inline int64_t diff_ns(struct timespec t1, struct timespec t2) {
   return diff;
 }
 
+static inline int64_t max(int64_t a, int64_t b) {
+  return a > b ? a : b;
+}
+
 static inline struct timespec add_ns(struct timespec t, int64_t ns) {
   struct timespec ret;
 
@@ -66,6 +74,8 @@ static void *timerthread(void *p) {
   if (err)
     error(EXIT_FAILURE, errno, "Couldn't set priority");
 
+  stat->max_diff = 0;
+
   clock_gettime(CLOCK_ID, &next);
   next = add_ns(next, param->interval);
 
@@ -78,7 +88,7 @@ static void *timerthread(void *p) {
     clock_nanosleep(CLOCK_ID, TIMER_ABSTIME, &next, NULL);
     clock_gettime(CLOCK_ID, &current);
 
-    stat->diff = diff_ns(current, next);
+    stat->max_diff = max(stat->max_diff, diff_ns(current, next));
     
     next = add_ns(current, param->interval);
   }
@@ -86,11 +96,11 @@ static void *timerthread(void *p) {
   return NULL;
 }
 
-static void process_options(int argc, char *argv[], thread_param_t * param) {
+static void process_options(int argc, char *argv[], thread_param_t * param, main_param_t * main_param) {
 
   for(;;) {
 
-    int c = getopt(argc, argv, "l:p:i:");
+    int c = getopt(argc, argv, "l:p:i:r:");
 
     if(c == -1)
       break;
@@ -103,7 +113,10 @@ static void process_options(int argc, char *argv[], thread_param_t * param) {
       param->max_cycles = atoi(optarg);
       break;
     case 'i':
-      param->interval = atoi(optarg);
+      param->interval = (atoi(optarg) * 1000);
+      break;
+    case 'r':
+      main_param->refresh_rate = atoi(optarg);
       break;
     default:
       exit(EXIT_FAILURE);
@@ -118,13 +131,16 @@ int main(int argc, char *argv[]) {
 
   pthread_t thread;
   thread_param_t param;
+  main_param_t main_param;
 
   // Default values
   param.interval = NSECS_PER_SECOND;
   param.max_cycles = 100;
   param.priority = 80;
 
-  process_options(argc, argv, &param);
+  main_param.refresh_rate = 10000;
+
+  process_options(argc, argv, &param, &main_param);
 
   int err =
       pthread_create(&thread, NULL, timerthread, (void *)&param);
@@ -134,9 +150,9 @@ int main(int argc, char *argv[]) {
 
   for (;;) {
 
-    usleep(100000);
+    usleep(main_param.refresh_rate);
 
-    printf("Diff: %" PRIi64 "us (%d)\n", (param.stat.diff / 1000), param.stat.nb_cycles);
+    printf("Maximum latency: %" PRIi64 "us (%d)\n", (param.stat.max_diff / 1000), param.stat.nb_cycles);
 
     if( param.max_cycles == param.stat.nb_cycles )
       break;