multipathd: don't flood system with sd_notify calls

DAEMON_RUNNING is only used by checkerloop to indicate that
path checkers are running. checkerloop switches back and forth
between DAEMON_IDLE and DAEMON_RUNNING in every iteration, i.e.
it performs two status changes per second on an idle system.
The repeated sd_notify() calls cause a lot of traffic on dbus as
systemd forwards these messages on the system bus. This can be
seen with systemd.log_level=debug. Better skip these notifications
that don't provide useful information to the user, who is very
unlikely to catch the daemon in "running" state anyway.

Signed-off-by: Martin Wilck <mwilck@suse.com>

diff --git a/multipathd/main.c b/multipathd/main.c
index 33db6a4..f766d64 100644 (file)
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -161,15 +161,27 @@ sd_notify_status(void)
        case DAEMON_CONFIGURE:
                return "STATUS=configure";
        case DAEMON_IDLE:
-               return "STATUS=idle";
        case DAEMON_RUNNING:
-               return "STATUS=running";
+               return "STATUS=up";
        case DAEMON_SHUTDOWN:
                return "STATUS=shutdown";
        }
        return NULL;
 }
 
+static void do_sd_notify(enum daemon_status old_state)
+{
+       /*
+        * Checkerloop switches back and forth between idle and running state.
+        * No need to tell systemd each time.
+        * These notifications cause a lot of overhead on dbus.
+        */
+       if ((running_state == DAEMON_IDLE || running_state == DAEMON_RUNNING) &&
+           (old_state == DAEMON_IDLE || old_state == DAEMON_RUNNING))
+               return;
+       sd_notify(0, sd_notify_status());
+}
+
 static void config_cleanup(void *arg)
 {
        pthread_mutex_unlock(&config_lock);
@@ -179,10 +191,12 @@ void post_config_state(enum daemon_status state)
 {
        pthread_mutex_lock(&config_lock);
        if (state != running_state) {
+               enum daemon_status old_state = running_state;
+
                running_state = state;
                pthread_cond_broadcast(&config_cond);
 #ifdef USE_SYSTEMD
-               sd_notify(0, sd_notify_status());
+               do_sd_notify(old_state);
 #endif
        }
        pthread_mutex_unlock(&config_lock);
@@ -195,6 +209,8 @@ int set_config_state(enum daemon_status state)
        pthread_cleanup_push(config_cleanup, NULL);
        pthread_mutex_lock(&config_lock);
        if (running_state != state) {
+               enum daemon_status old_state = running_state;
+
                if (running_state != DAEMON_IDLE) {
                        struct timespec ts;
 
@@ -207,7 +223,7 @@ int set_config_state(enum daemon_status state)
                        running_state = state;
                        pthread_cond_broadcast(&config_cond);
 #ifdef USE_SYSTEMD
-                       sd_notify(0, sd_notify_status());
+                       do_sd_notify(old_state);
 #endif
                }
        }