keeping the bounds users set for their trade-off.
+Age Tracking
+~~~~~~~~~~~~
+
+By analyzing the monitoring results, users can also find how long the current
+access pattern of a region has maintained. That could be used for good
+understanding of the access pattern. For example, page placement algorithm
+utilizing both the frequency and the recency could be implemented using that.
+To make such access pattern maintained period analysis easier, DAMON maintains
+yet another counter called ``age`` in each region. For each ``aggregation
+interval``, DAMON checks if the region's size and access frequency
+(``nr_accesses``) has significantly changed. If so, the counter is reset to
+zero. Otherwise, the counter is increased.
+
+
Dynamic Target Space Updates Handling
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~