-
- ret = fullwrite (server->file, line, strlen (line));
- if (ret >= 0)
- { /* 0 indicates that a blank line was written */
- ret = fullwrite (server->file, "\r\n", 2);
- }
+ char *buf;
+
+ /* Combine the string and the CR-LF into one buffer. Otherwise, two
+ reasonable network stack optimizations, Nagle's algorithm and
+ delayed acks, combine to delay us a fraction of a second on every
+ message we send. (Movemail writes line without \r\n, client
+ kernel sends packet, server kernel delays the ack to see if it
+ can combine it with data, movemail writes \r\n, client kernel
+ waits because it has unacked data already in its outgoing queue,
+ client kernel eventually times out and sends.)
+
+ This can be something like 0.2s per command, which can add up
+ over a few dozen messages, and is a big chunk of the time we
+ spend fetching mail from a server close by. */
+ buf = alloca (strlen (line) + 3);
+ strcpy (buf, line);
+ strcat (buf, "\r\n");
+ ret = fullwrite (server->file, buf, strlen (buf));