Docs/admin-guide/mm/damon/usage: explain the format of damon_aggregate tracepoint

The example of the section for damon_aggregated tracepoint is not
explaining how the output looks like, and how it can be interpreted.
Add it.

Link: https://lkml.kernel.org/r/20230907022929.91361-6-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/admin-guide/mm/damon/usage.rst

@@ -513,6 +513,20 @@ results using tracepoint supporting tools like ``perf``.  For example::
     # kill 9 $(pidof perf)
     # echo off > monitor_on
     # perf script
+    kdamond.0 46568 [027] 79357.842179: damon:damon_aggregated: target_id=0 nr_regions=11 122509119488-135708762112: 0 864
+    [...]
+
+Each line of the perf script output represents each monitoring region.  The
+first five fields are as usual other tracepoint outputs.  The sixth field
+(``target_id=X``) shows the ide of the monitoring target of the region.  The
+seventh field (``nr_regions=X``) shows the total number of monitoring regions
+for the target.  The eighth field (``X-Y:``) shows the start (``X``) and end
+(``Y``) addresses of the region in bytes.  The ninth field (``X``) shows the
+``nr_accesses`` of the region (refer to
+:ref:`design <damon_design_region_based_sampling>` for more details of the
+counter).  Finally the tenth field (``X``) shows the ``age`` of the region
+(refer to :ref:`design <damon_design_age_tracking>` for more details of the
+counter).
 
 .. _debugfs_interface:
 

Documentation/mm/damon/design.rst

@@ -154,6 +154,8 @@ The monitoring overhead of this mechanism will arbitrarily increase as the
 size of the target workload grows.
 
 
+.. _damon_design_region_based_sampling:
+
 Region Based Sampling
 ~~~~~~~~~~~~~~~~~~~~~
 
@@ -191,6 +193,8 @@ In this way, DAMON provides its best-effort quality and minimal overhead while
 keeping the bounds users set for their trade-off.
 
 
+.. _damon_design_age_tracking:
+
 Age Tracking
 ~~~~~~~~~~~~