Support maxiov per connection type (redis#12234)

Rather than a fixed iovcnt for connWritev, support maxiov per connection type instead.
A minor change to reduce memory for struct connection.

Signed-off-by: zhenwei pi <[email protected]>

src/connection.h

@@ -114,14 +114,15 @@ typedef struct ConnectionType {
 struct connection {
     ConnectionType *type;
     ConnectionState state;
+    int last_errno;
+    int fd;
     short int flags;
     short int refs;
-    int last_errno;
+    unsigned short int iovcnt;
     void *private_data;
     ConnectionCallbackFunc conn_handler;
     ConnectionCallbackFunc write_handler;
     ConnectionCallbackFunc read_handler;
-    int fd;
 };
 
 #define CONFIG_BINDADDR_MAX 16

src/networking.c

@@ -1787,8 +1787,9 @@ client *lookupClientByID(uint64_t id) {
  * and 'nwritten' is an output parameter, it means how many bytes server write
  * to client. */
 static int _writevToClient(client *c, ssize_t *nwritten) {
-    struct iovec iov[IOV_MAX];
     int iovcnt = 0;
+    int iovmax = min(IOV_MAX, c->conn->iovcnt);
+    struct iovec iov[iovmax];
     size_t iov_bytes_len = 0;
     /* If the static reply buffer is not empty, 
      * add it to the iov array for writev() as well. */
@@ -1804,7 +1805,7 @@ static int _writevToClient(client *c, ssize_t *nwritten) {
     listNode *next;
     clientReplyBlock *o;
     listRewind(c->reply, &iter);
-    while ((next = listNext(&iter)) && iovcnt < IOV_MAX && iov_bytes_len < NET_MAX_WRITES_PER_EVENT) {
+    while ((next = listNext(&iter)) && iovcnt < iovmax && iov_bytes_len < NET_MAX_WRITES_PER_EVENT) {
         o = listNodeValue(next);
         if (o->used == 0) { /* empty node, just release it and skip. */
             c->reply_bytes -= o->size;

src/socket.c

@@ -78,6 +78,7 @@ static connection *connCreateSocket(void) {
     connection *conn = zcalloc(sizeof(connection));
     conn->type = &CT_Socket;
     conn->fd = -1;
+    conn->iovcnt = IOV_MAX;
 
     return conn;
 }

src/tls.c

@@ -462,6 +462,7 @@ static connection *createTLSConnection(int client_side) {
     tls_connection *conn = zcalloc(sizeof(tls_connection));
     conn->c.type = &CT_TLS;
     conn->c.fd = -1;
+    conn->c.iovcnt = IOV_MAX;
     conn->ssl = SSL_new(ctx);
     return (connection *) conn;
 }

src/unix.c

@@ -78,6 +78,7 @@ static connection *connCreateUnix(void) {
     connection *conn = zcalloc(sizeof(connection));
     conn->type = &CT_Unix;
     conn->fd = -1;
+    conn->iovcnt = IOV_MAX;
 
     return conn;
 }