added explanation for the magic 511 backlog number

[redis.git] / src / anet.c

diff --git a/src/anet.c b/src/anet.c
index ba4e6cce89bbc7a552e8510a03a2cb67c53af1f6..434d945c7d850edd8b8a8934d254bbc88e5d62d0 100644 (file)
--- a/src/anet.c
+++ b/src/anet.c
@@ -262,7 +262,11 @@ static int anetListen(char *err, int s, struct sockaddr *sa, socklen_t len) {
         close(s);
         return ANET_ERR;
     }
-    if (listen(s, 511) == -1) { /* the magic 511 constant is from nginx */
+
+    /* Use a backlog of 512 entries. We pass 511 to the listen() call because
+     * the kernel does: backlogsize = roundup_pow_of_two(backlogsize + 1);
+     * which will thus give us a backlog of 512 entries */
+    if (listen(s, 511) == -1) {
         anetSetError(err, "listen: %s", strerror(errno));
         close(s);
         return ANET_ERR;