But Moodle can log real performance data to the apache error log with the following options added to config.php:
define('MDL_PERF', true);
define('MDL_PERFDB', true);
define('MDL_PERFTOFOOT', true);
The error logs can then be post-processed with cvs:/contrib/tools/devtools/perf_parse.pl to find poorly performing pages.
My colleague Paul has just updated the parsing script to support Moodle 2.1. Enjoy!
(See my previous post on this for an example of the output).