Reduce CPU usage when test baud rate is limited

configure.ac

@@ -342,5 +342,14 @@ AC_SEARCH_LIBS(clock_gettime, [rt posix4])
 # Check for clock_gettime support
 AC_CHECK_FUNCS([clock_gettime])
 
+# Check if we need -lrt for nanosleep
+AC_SEARCH_LIBS(nanosleep, [rt posix4])
+# Check for nanosleep support
+AC_CHECK_FUNCS([nanosleep])
+# Check if we need -lrt for clock_nanosleep
+AC_SEARCH_LIBS(clock_nanosleep, [rt posix4])
+# Check for clock_nanosleep support
+AC_CHECK_FUNCS([clock_nanosleep])
+
 AC_CONFIG_FILES([Makefile src/Makefile src/version.h examples/Makefile iperf3.spec])
 AC_OUTPUT

src/iperf_api.c

@@ -1881,17 +1881,73 @@ iperf_check_throttle(struct iperf_stream *sp, struct iperf_time *nowP)
  struct iperf_time temp_time;
  double seconds;
  uint64_t bits_per_second;
+ int64_t missing_rate;
+ uint64_t bits_sent;
+
+#if defined(HAVE_CLOCK_NANOSLEEP) || defined(HAVE_NANOSLEEP)
+ struct timespec nanosleep_time;
+ int64_t time_to_green_light, delta_bits;
+ int ret;
+#endif /* HAVE_CLOCK_NANOSLEEP || HAVE_NANOSLEEP) */
+#if defined(HAVE_CLOCK_NANOSLEEP)
+ int64_t ns;
+#endif /* HAVE_CLOCK_NANOSLEEP */
 
  if (sp->test->done || sp->test->settings->rate == 0)
  return;
  iperf_time_diff(&sp->result->start_time_fixed, nowP, &temp_time);
  seconds = iperf_time_in_secs(&temp_time);
- bits_per_second = sp->result->bytes_sent * 8 / seconds;
- if (bits_per_second < sp->test->settings->rate) {
+ bits_sent = sp->result->bytes_sent * 8;
+ bits_per_second = bits_sent / seconds;
+ missing_rate = sp->test->settings->rate - bits_per_second;
+
+ if (missing_rate > 0) {
  sp->green_light = 1;
  } else {
  sp->green_light = 0;
  }
+
+#if defined(HAVE_CLOCK_NANOSLEEP) || defined(HAVE_NANOSLEEP)
+ // If estimated time to next send is large enough, sleep instead of just CPU looping until green light is set
+ if (missing_rate < 0) {
+ delta_bits = bits_sent - (seconds * sp->test->settings->rate);
+ // Calclate time until next data send is required
+ time_to_green_light = (SEC_TO_NS * delta_bits / sp->test->settings->rate);
+ // Whether shouuld wait before next send
+ if (time_to_green_light >= 0) {
+#if defined(HAVE_CLOCK_NANOSLEEP)
+ if (clock_gettime(CLOCK_MONOTONIC, &nanosleep_time) == 0) {
+ // Calculate absolute end of sleep time
+ ns = nanosleep_time.tv_nsec + time_to_green_light;
+ if (ns < SEC_TO_NS) {
+ nanosleep_time.tv_nsec = ns;
+ } else {
+ nanosleep_time.tv_sec += ns / SEC_TO_NS;
+ nanosleep_time.tv_nsec = ns % SEC_TO_NS;
+ }
+ // Sleep until average baud rate reaches the target value
+ while((ret = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &nanosleep_time, NULL)) == EINTR);
+ if (ret == 0) {
+ sp->green_light = 1;
+ }
+ }
+
+#else /* HAVE_NANOSLEEP */
+ nanosleep_time.tv_sec = 0;
+ // Sleep until average baud rate reaches the target value or intrupt / error
+ do {
+ // nansleep() time should be less than 1 sec
+ nanosleep_time.tv_nsec = (time_to_green_light >= SEC_TO_NS) ? SEC_TO_NS - 1 : time_to_green_light;
+ time_to_green_light -= nanosleep_time.tv_nsec;
+ ret = nanosleep(&nanosleep_time, NULL);
+ } while (ret == 0 && time_to_green_light > 0);
+ if (ret == 0) {
+ sp->green_light = 1;
+ }
+#endif /* HAVE_CLOCK_NANOSLEEP else HAVE_NANOSLEEP */
+ }
+ }
+#endif /* HAVE_CLOCK_NANOSLEEP || HAVE_NANOSLEEP */
 }
 
 /* Verify that average traffic is not greater than the specified limit */
@@ -1982,7 +2038,11 @@ iperf_send_mt(struct iperf_stream *sp)
  if (!streams_active)
  break;
  }
+#if defined(HAVE_CLOCK_NANOSLEEP) || defined(HAVE_NANOSLEEP)
+ if (!sp->green_light) { /* Should check if green ligh can be set, as pacing timer is not supported in this case */
+#else /* !HAVE_CLOCK_NANOSLEEP && !HAVE_NANOSLEEP */
  if (!no_throttle_check) { /* Throttle check if was not checked for each send */
+#endif /* HAVE_CLOCK_NANOSLEEP, HAVE_NANOSLEEP */
  iperf_time_now(&now);
  if (sp->sender)
  iperf_check_throttle(sp, &now);
@@ -2032,6 +2092,7 @@ iperf_init_test(struct iperf_test *test)
  return 0;
 }
 
+#if !defined(HAVE_CLOCK_NANOSLEEP) && !defined(HAVE_NANOSLEEP)
 static void
 send_timer_proc(TimerClientData client_data, struct iperf_time *nowP)
 {
@@ -2043,20 +2104,25 @@ send_timer_proc(TimerClientData client_data, struct iperf_time *nowP)
  */
  iperf_check_throttle(sp, nowP);
 }
+#endif /* !HAVE_CLOCK_NANOSLEEP && !HAVE_NANOSLEEP) */
 
 int
 iperf_create_send_timers(struct iperf_test * test)
 {
- struct iperf_time now;
  struct iperf_stream *sp;
+#if !defined(HAVE_CLOCK_NANOSLEEP) && !defined(HAVE_NANOSLEEP)
  TimerClientData cd;
+ struct iperf_time now;
 
  if (iperf_time_now(&now) < 0) {
  i_errno = IEINITTEST;
  return -1;
  }
+#endif /* !HAVE_CLOCK_NANOSLEEP && !HAVE_NANOSLEEP) */
+
  SLIST_FOREACH(sp, &test->streams, streams) {
  sp->green_light = 1;
+#if !defined(HAVE_CLOCK_NANOSLEEP) && !defined(HAVE_NANOSLEEP)
  if (test->settings->rate != 0 && sp->sender) {
  cd.p = sp;
  sp->send_timer = tmr_create(NULL, send_timer_proc, cd, test->settings->pacing_timer, 1);
@@ -2065,6 +2131,7 @@ iperf_create_send_timers(struct iperf_test * test)
  return -1;
  }
  }
+#endif /* !HAVE_CLOCK_NANOSLEEP && !HAVE_NANOSLEEP) */
  }
  return 0;
 }

src/iperf_locale.c

@@ -163,7 +163,12 @@ const char usage_longstr[] = "Usage: iperf3 [-s|-c host] [options]\n"
  " -b, --bitrate #[KMG][/#] target bitrate in bits/sec (0 for unlimited)\n"
  " (default %d Mbit/sec for UDP, unlimited for TCP)\n"
  " (optional slash and packet count for burst mode)\n"
+#if !defined(HAVE_CLOCK_NANOSLEEP) && !defined(HAVE_NANOSLEEP)
  " --pacing-timer #[KMG] set the timing for pacing, in microseconds (default %d)\n"
+#else
+ " --pacing-timer #[KMG] set the Server timing for pacing, in microseconds (default %d)\n"
+ " (used by the server only if this option is in its help message)\n"
+#endif /* !HAVE_CLOCK_NANOSLEEP && !HAVE_NANOSLEEP */
 #if defined(HAVE_SO_MAX_PACING_RATE)
  " --fq-rate #[KMG] enable fair-queuing based socket pacing in\n"
  " bits/sec (Linux only)\n"