diff --git a/src/haproxy.c b/src/haproxy.c
index 9dfdd22..5da563b 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2275,8 +2275,14 @@
 	if (global.tune.maxpollevents <= 0)
 		global.tune.maxpollevents = MAX_POLL_EVENTS;
 
-	if (global.tune.runqueue_depth <= 0)
-		global.tune.runqueue_depth = RUNQUEUE_DEPTH;
+	if (global.tune.runqueue_depth <= 0) {
+		/* tests on various thread counts from 1 to 64 have shown an
+		 * optimal queue depth following roughly 1/sqrt(threads).
+		 */
+		int s = my_flsl(global.nbthread);
+		s += (global.nbthread / s); // roughly twice the sqrt.
+		global.tune.runqueue_depth = RUNQUEUE_DEPTH * 2 / s;
+	}
 
 	if (global.tune.recv_enough == 0)
 		global.tune.recv_enough = MIN_RECV_AT_ONCE_ENOUGH;