nixos/redis: add changelog for #67768

nixos/doc/manual/release-notes/rl-1909.xml

@@ -603,6 +603,9 @@
       The <link linkend="opt-services.redis.enable">redis module</link> was hardcoded to use the <literal>redis</literal> user,
       <filename class="directory">/run/redis</filename> as runtime directory and
       <filename class="directory">/var/lib/redis</filename> as state directory.
+      Note that the NixOS module for Redis now disables kernel support for Transparent Huge Pages (THP),
+      because this features causes major performance problems for Redis,
+      e.g. (https://redis.io/topics/latency).
     </para>
    </listitem>
    <listitem>