Only poll in the connector sender loop if the top of the list is a delayed writer

src/connector.c

@@ -71,6 +71,8 @@ struct sender_send {
 	client_instance_t *client;
 	char *buf;
 	int len;
+	bool polling;
+	ts_t polltime;
 };
 
 typedef struct sender_send sender_send_t;
@@ -326,7 +328,6 @@ void *sender(void *arg)
 {
 	conn_instance_t *ci = (conn_instance_t *)arg;
 	ckpool_t *ckp = ci->pi->ckp;
-	bool polling = false;
 
 	rename_proc("csender");
 
@@ -334,17 +335,24 @@ void *sender(void *arg)
 		sender_send_t *sender_send;
 		client_instance_t *client;
 		int ret, fd, ofs = 0;
+		bool polling = false;
 
 		mutex_lock(&sender_lock);
+		if (sender_sends && sender_sends->polling)
+			polling = true;
 		if (!sender_sends || polling) {
 			ts_t timeout_ts;
 
+			if (!polling) {
+				/* Wait 1 second in pure event driven mode */
 				ts_realtime(&timeout_ts);
-			if (!polling)
 				timeout_ts.tv_sec += 1;
-			else {
-				ts_t wait_ts = {0, 100000000};
-				timeraddspec(&timeout_ts, &wait_ts);
+			} else {
+				/* Poll every 100ms if the head of the list is
+				 * a delayed writer. */
+				timeout_ts.tv_sec = 0;
+				timeout_ts.tv_nsec = 100000000;
+				timeraddspec(&timeout_ts, &sender_sends->polltime);
 			}
 			pthread_cond_timedwait(&sender_cond, &sender_lock, &timeout_ts);
 		}
@@ -387,10 +395,10 @@ void *sender(void *arg)
 			DL_APPEND(sender_sends, sender_send);
 			mutex_unlock(&sender_lock);
 
-			polling = true;
+			sender_send->polling = true;
+			ts_realtime(&sender_send->polltime);
 			continue;
 		}
-		polling = false;
 		while (sender_send->len) {
 			ret = send(fd, sender_send->buf + ofs, sender_send->len , 0);
 			if (unlikely(ret < 0)) {