The "reuseport" option of the "listen" directive. When configured, an individual listen socket on a given address is created for each worker process. This allows to reduce in-kernel lock contention on configurations with high accept rates, resulting in better performance. As of now it works on Linux and DragonFly BSD. Note that on Linux incoming connection requests are currently tied up to a specific listen socket, and if some sockets are closed, connection requests will be reset, see https://lwn.net/Articles/542629/. With nginx, this may happen if the number of worker processes is reduced. There is no such problem on DragonFly BSD. Based on previous work by Sepherosa Ziehau and Yingqi Lu.

--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -725,6 +725,12 @@ ngx_event_process_init(ngx_cycle_t *cycl
     ls = cycle->listening.elts;
     for (i = 0; i < cycle->listening.nelts; i++) {
 
+#if (NGX_HAVE_REUSEPORT)
+        if (ls[i].reuseport && ls[i].worker != ngx_worker) {
+            continue;
+        }
+#endif
+
         c = ngx_get_connection(ls[i].fd, cycle->log);
 
         if (c == NULL) {