Try to send data using writev() to reduce copying and system calls.

src/core/ioqueue.c

@@ -160,10 +160,46 @@ static void ioq_send_remove(struct ioq_send* q, struct adc_message* msg)
 
 int ioq_send_send(struct ioq_send* q, struct net_connection* con)
 {
-	int ret;
-	struct adc_message* msg = list_get_first(q->queue);
-	if (!msg) return 0;
-	uhub_assert(msg->cache && *msg->cache);
+  int ret;
+  struct adc_message* msg = list_get_first(q->queue);
+  if (!msg) return 0;
+  uhub_assert(msg->cache && *msg->cache);
+
+#ifdef HAVE_FUNC_WRITEV
+#define MAX_IOVEC 32
+  struct iovec vec[MAX_IOVEC];
+  size_t n = 0;
+  vec[0].iov_base = msg->cache + q->offset;
+  vec[0].iov_len = msg->length - q->offset;
+
+  for (struct adc_message* tmp = (struct adc_message*) list_get_next(q->queue), n = 1; tmp && n < MAX_IOVEC; tmp = (struct adc_message*) list_get_next(q->queue), n++)
+  {
+    vec[n].iov_base = msg->cache;
+    vec[n].iov_len = msg->length;
+  }
+
+  ret = net_con_writev(con, &iovec, n);
+
+  if (ret > 0)
+  {
+    while (ret > 0)
+    {
+      if (ret >= (msg->length - q->offset))
+      {
+        ret -= (msg->length - q->offset);
+        q->offset = 0;
+        ioq_send_remove(q, msg);
+      }
+      else
+      {
+        q->offset += ret;
+        return 0;
+      }
+    }
+    return 1;
+  }
+  return ret;
+#else
 	ret = net_con_send(con, msg->cache + q->offset, msg->length - q->offset);
 
 	if (ret > 0)
@@ -176,8 +212,10 @@ int ioq_send_send(struct ioq_send* q, struct net_connection* con)
 		return 1;
 	}
 	return ret;
+#endif
 }
 
+
 int ioq_send_is_empty(struct ioq_send* q)
 {
 	return (q->size - q->offset) == 0;

src/network/connection.c

@@ -57,6 +57,48 @@ ssize_t net_con_send(struct net_connection* con, const void* buf, size_t len)
 	return ret;
 }
 
+#ifdef HAVE_FUNC_WRITEV
+ssize_t net_con_writev(struct net_connection* con, const struct iovec* iov, size_t iocnt)
+{
+  int ret;
+#ifdef SSL_SUPPORT
+  if (!con->ssl)
+  {
+#endif
+    ret = writev(con->sd, iovec, (int) iocnt);
+    if (ret == -1)
+    {
+      if (is_blocked_or_interrupted())
+        return 0;
+      return -1;
+    }
+#ifdef SSL_SUPPORT
+  }
+  else
+  {
+    ssize_t total = 0;
+    ret = 0;
+    while (iocnt--)
+    {
+      ret = net_ssl_send(con, buf, len);
+      if (ret >= 0)
+        total += ret;
+      else
+      {
+        break;
+      }
+    }
+
+    if (total == 0 && !is_blocked_or_interrupted())
+        return -1;
+
+    return total;
+  }
+#endif /* SSL_SUPPORT */
+  return ret;
+}
+#endif
+
 ssize_t net_con_recv(struct net_connection* con, void* buf, size_t len)
 {
 	int ret;

src/network/connection.h

@@ -92,6 +92,11 @@ extern void net_con_close(struct net_connection* con);
  */
 extern ssize_t net_con_send(struct net_connection* con, const void* buf, size_t len);
 
+
+#ifdef HAVE_FUNC_WRITEV
+extern ssize_t net_con_writev(struct net_connection* con, const struct iovec* iov, size_t iocnt);
+#endif
+
 /**
  * Receive data
  *