diff --git a/include/haproxy/stream.h b/include/haproxy/stream.h
index d4d202b2f..8daf2adcc 100644
--- a/include/haproxy/stream.h
+++ b/include/haproxy/stream.h
@@ -286,6 +286,12 @@ static inline void stream_inc_http_fail_ctr(struct stream *s)
 
 static inline void stream_add_srv_conn(struct stream *sess, struct server *srv)
 {
+	/* note: this inserts in reverse order but we do not care, it's only
+	 * used for massive kills (i.e. almost never). MT_LIST_ADD() is a bit
+	 * faster than MT_LIST_ADDQ under contention due to a faster recovery
+	 * from a conflict with an adjacent MT_LIST_DEL, and using it improves
+	 * the performance by about 3% on 32-cores.
+	 */
 	MT_LIST_ADD(&srv->actconns, &sess->by_srv);
 	HA_ATOMIC_STORE(&sess->srv_conn, srv);
 }