Document dynamic-hz in the example redis.conf.

redis.conf

@@ -1205,6 +1205,22 @@ client-output-buffer-limit pubsub 32mb 8mb 60
 # 100 only in environments where very low latency is required.
 hz 10
 
+# Normally it is useful to have an HZ value which is proportional to the
+# number of clients connected. This is useful in order, for instance, to
+# avoid too many clients are processed for each background task invocation
+# in order to avoid latency spikes.
+#
+# Since the default HZ value by default is conservatively set to 10, Redis
+# offers, and enables by default, the ability to use an adaptive HZ value
+# which will temporary raise when there are many connected clients.
+#
+# When dynamic HZ is enabled, the actual configured HZ will be used as
+# as a baseline, but multiples of the configured HZ value will be actually
+# used as needed once more clients are connected. In this way an idle
+# instance will use very little CPU time while a busy instance will be
+# more responsive.
+dynamic-hz yes
+
 # When a child rewrites the AOF file, if the following option is enabled
 # the file will be fsync-ed every 32 MB of data generated. This is useful
 # in order to commit the file to the disk more incrementally and avoid