-The "cache" I<plugin instance> reports the number of elements in the value list
-cache (the cache you can interact with using L<collectd-unixsock(5)>).
+=over 4
+
+=item C<collectd-write_queue/queue_length>
+
+The number of metrics currently in the write queue. You can limit the queue
+length with the B<WriteQueueLimitLow> and B<WriteQueueLimitHigh> options.
+
+=item C<collectd-write_queue/derive-dropped>
+
+The number of metrics dropped due to a queue length limitation.
+If this value is non-zero, your system can't handle all incoming metrics and
+protects itself against overload by dropping metrics.
+
+=item C<collectd-cache/cache_size>
+
+The number of elements in the metric cache (the cache you can interact with
+using L<collectd-unixsock(5)>).
+
+=back