Manual:$wgProfileToDatabase

Details
Log sums from profiling into "profiling" table in db.

In MediaWiki 1.22 and older, in order to use this, you have to create the 'profiling' table in your database. See maintenance/archives/patch-profiling.sql. In newer versions, $wgProfileToDatabase was removed. Set $wgProfiler to ProfilerSimpleDB in StartProfiler.php instead of using $wgProfileToDatabase.