Reattempt sending delayed sends immediately after servicing one send successfully.

src/connector.c

@@ -340,6 +340,7 @@ void *sender(void *arg)
 {
 	conn_instance_t *ci = (conn_instance_t *)arg;
 	ckpool_t *ckp = ci->pi->ckp;
+	bool sent = false;
 
 	rename_proc("csender");
 
@@ -349,8 +350,11 @@ void *sender(void *arg)
 		int ret, fd, ofs = 0;
 
 		mutex_lock(&sender_lock);
-		/* Poll every 100ms if there are no new sends */
-		if (!sender_sends) {
+		/* Poll every 100ms if there are no new sends. Re-examine
+		 * delayed sends immediately after a successful send in case
+		 * endless new sends more frequently end up starving the
+		 * delayed sends. */
+		if (!sender_sends && !sent) {
 			const ts_t polltime = {0, 100000000};
 			ts_t timeout_ts;
 
@@ -363,8 +367,11 @@ void *sender(void *arg)
 			DL_DELETE(sender_sends, sender_send);
 		mutex_unlock(&sender_lock);
 
+		sent = false;
+
 		/* Service delayed sends only if we have timed out on the
-		 * conditional with no new sends appearing. */
+		 * conditional with no new sends appearing or have just
+		 * serviced another message successfully. */
 		if (!sender_send) {
 			if (!delayed_sends)
 				continue;
@@ -404,6 +411,7 @@ void *sender(void *arg)
 			DL_APPEND(delayed_sends, sender_send);
 			continue;
 		}
+		sent = true;
 		while (sender_send->len) {
 			ret = send(fd, sender_send->buf + ofs, sender_send->len , 0);
 			if (unlikely(ret < 0)) {