Use setitimer() instead of alarm().

This lets us check timers every tenth second instead of every second,
so we can switch out of the more expensive select() mode even with
the default reporting interval of a second.

src/iperf_client_api.c

@@ -296,15 +296,6 @@ iperf_client_end(struct iperf_test *test)
 }
 
 
-static int sigalrm_triggered;
-
-static void
-sigalrm_handler(int sig)
-{
-    sigalrm_triggered = 1;
-}
-
-
 static jmp_buf sigend_jmp_buf;
 
 static void
@@ -314,17 +305,26 @@ sigend_handler(int sig)
 }
 
 
+typedef enum { cm_select, cm_itimer } cm_t;
+
+static int sigalrm_triggered;
+
+static void
+sigalrm_handler(int sig)
+{
+    sigalrm_triggered = 1;
+}
+
 int
 iperf_run_client(struct iperf_test * test)
 {
-    int concurrency_model;
+    cm_t concurrency_model;
     int startup;
-#define CM_SELECT 1
-#define CM_SIGALRM 2
     int result = 0;
     fd_set read_set, write_set;
     struct timeval now;
     struct timeval* timeout = NULL;
+    struct itimerval itv;
 
     /* Termination signals. */
     iperf_catch_sigend(sigend_handler);
@@ -357,10 +357,10 @@ iperf_run_client(struct iperf_test * test)
     cpu_util(NULL);
 
     startup = 1;
-    concurrency_model = CM_SELECT;	/* always start in select mode */
+    concurrency_model = cm_select;	/* always start in select mode */
     while (test->state != IPERF_DONE) {
 
-	if (concurrency_model == CM_SELECT) {
+	if (concurrency_model == cm_select) {
 	    memcpy(&read_set, &test->read_set, sizeof(fd_set));
 	    memcpy(&write_set, &test->write_set, sizeof(fd_set));
 	    (void) gettimeofday(&now, NULL);
@@ -390,18 +390,21 @@ iperf_run_client(struct iperf_test * test)
 		** where it either won't work or is ill-advised.
 		*/
 		if (test->may_use_sigalrm && test->settings->rate == 0 &&
-		    (test->stats_interval == 0 || test->stats_interval > 1) &&
+		    (test->stats_interval == 0 || test->stats_interval > 0.2) &&
-		    test->stats_interval == (int) test->stats_interval &&
+		    (test->reporter_interval == 0 || test->reporter_interval > 0.2) &&
-		    (test->reporter_interval == 0 || test->reporter_interval > 1) &&
+		    (test->omit == 0 || test->omit > 0.2) &&
-		    test->reporter_interval == (int) test->reporter_interval &&
-		    (test->omit == 0 || test->omit > 1) &&
 		    ! test->reverse) {
-		    concurrency_model = CM_SIGALRM;
+		    concurrency_model = cm_itimer;
 		    test->multisend = 1;
 		    signal(SIGALRM, sigalrm_handler);
 		    sigalrm_triggered = 0;
-		    alarm(1);
+		    itv.it_interval.tv_sec = 0;
+		    itv.it_interval.tv_usec = 100000;
+		    itv.it_value.tv_sec = 0;
+		    itv.it_value.tv_usec = 100000;
+		    (void) setitimer(ITIMER_REAL, &itv, NULL);
 		}
+
 	    }
 
 	    if (test->reverse) {
@@ -410,21 +413,19 @@ iperf_run_client(struct iperf_test * test)
 		    return -1;
 	    } else {
 		// Regular mode. Client sends.
-		if (iperf_send(test, concurrency_model == CM_SIGALRM ? NULL : &write_set) < 0)
+		if (iperf_send(test, concurrency_model == cm_itimer ? NULL : &write_set) < 0)
 		    return -1;
 	    }
 
-	    if ((concurrency_model == CM_SELECT &&
+	    if ((concurrency_model == cm_select &&
 	         (result == 0 ||
 		  (timeout != NULL && timeout->tv_sec == 0 && timeout->tv_usec == 0))) ||
-	        (concurrency_model == CM_SIGALRM && sigalrm_triggered)) {
+	        (concurrency_model == cm_itimer && sigalrm_triggered)) {
 		/* Run the timers. */
 		(void) gettimeofday(&now, NULL);
 		tmr_run(&now);
-	        if (concurrency_model == CM_SIGALRM) {
+	        if (concurrency_model == cm_itimer)
 		    sigalrm_triggered = 0;
-		    alarm(1);
-		}
 	    }
 
 	    /* Is the test done yet? */
@@ -442,8 +443,15 @@ iperf_run_client(struct iperf_test * test)
 	    test->stats_callback(test);
 	    if (iperf_set_send_state(test, TEST_END) != 0)
 		return -1;
-	    /* And if we were doing SIGALRM, go back to select for the end. */
+	    /* If we were doing setitimer(), go back to select() for the end. */
-	    concurrency_model = CM_SELECT;
+	    if (concurrency_model == cm_itimer) {
+		itv.it_interval.tv_sec = 0;
+		itv.it_interval.tv_usec = 0;
+		itv.it_value.tv_sec = 0;
+		itv.it_value.tv_usec = 0;
+		(void) setitimer(ITIMER_REAL, &itv, NULL);
+		concurrency_model = cm_select;
+	    }
 	}
     }