DOC: Added reference to upstream documentation.

src/doc/development/benchmarking.md

@@ -34,8 +34,8 @@ benchmarks) delivered by the server.
 ### Benchmarking SQL commands ###
 
 MariaDB and MySQL have a feature to enable the logging of SQL queries' times.  This logging must be
-turned on on the SQL server.  For the Docker environment LinkAhead, this can be done with `linkahead
-mysqllog {on,off,store}`.
+turned on on the SQL server as described in the [upstream documentation](https://mariadb.com/kb/en/general-query-log/).  For the Docker
+environment LinkAhead, this can conveniently be done with `linkahead mysqllog {on,off,store}`.
 
 ### External JVM profilers ###