Poll more frequently when a client is not ready to be written to instead of waiting for it

src/connector.c

@@ -326,13 +326,13 @@ void *sender(void *arg)
 {
 	conn_instance_t *ci = (conn_instance_t *)arg;
 	ckpool_t *ckp = ci->pi->ckp;
+	bool polling = false;
 
 	rename_proc("csender");
 
 	while (42) {
 		sender_send_t *sender_send;
 		client_instance_t *client;
-		bool only_send = false;
 		int ret, fd, ofs = 0;
 
 		mutex_lock(&sender_lock);
@@ -340,14 +340,17 @@ void *sender(void *arg)
 			ts_t timeout_ts;
 
 			ts_realtime(&timeout_ts);
-			timeout_ts.tv_sec += 1;
+			if (!polling)
+				timeout_ts.tv_sec += 1;
+			else {
+				ts_t wait_ts = {0, 1000000};
+				timeraddspec(&timeout_ts, &wait_ts);
+			}
 			pthread_cond_timedwait(&sender_cond, &sender_lock, &timeout_ts);
 		}
 		sender_send = sender_sends;
 		if (likely(sender_send))
 			DL_DELETE(sender_sends, sender_send);
-		if (!sender_send)
-			only_send = true;
 		mutex_unlock(&sender_lock);
 
 		if (!sender_send)
@@ -365,22 +368,23 @@ void *sender(void *arg)
 			free(sender_send);
 			continue;
 		}
-		/* If there are other sends pending and this socket is not
-		 * ready to receive data from us, put the send back on the
-		 * list. */
-		if (!only_send) {
-			ret = wait_write_select(fd, 0);
-			if (ret < 1) {
-				LOGDEBUG("Client %d not ready for writes", client->id);
-
-				/* Append it to the tail of the list */
-				mutex_lock(&sender_lock);
-				DL_APPEND(sender_sends, sender_send);
-				mutex_unlock(&sender_lock);
-
-				continue;
-			}
+		/* If this socket is not ready to receive data from us, put the
+		 * send back on the tail of the list and decrease the timeout
+		 * to poll to either look for a client that is ready or poll
+		 * select on this one */
+		ret = wait_write_select(fd, 0);
+		if (ret < 1) {
+			LOGDEBUG("Client %d not ready for writes", client->id);
+
+			/* Append it to the tail of the list */
+			mutex_lock(&sender_lock);
+			DL_APPEND(sender_sends, sender_send);
+			mutex_unlock(&sender_lock);
+
+			polling = true;
+			continue;
 		}
+		polling = false;
 		while (sender_send->len) {
 			ret = send(fd, sender_send->buf + ofs, sender_send->len , 0);
 			if (unlikely(ret < 0)) {