xdebug to the rescue! 

[php.ini]
zend_extension=/usr/local/lib/php/extensions/xdebug.so
xdebug.profiler_enable=1
xdebug.profiler_aggregate = On
xdebug.profiler_output_dir=/tmp
...

% kcachegrind drupal_xdebug1.out

Turn on Normal Drupal Cacheing
500 fetches, 5 max parallel, 3.226e+06 bytes, in 7.7064 seconds
6452 mean bytes/connection
64.8812 fetches/sec, 418613 bytes/sec
msecs/connect: 2.53989 mean, 24.502 max, 1.914 min
msecs/first-response: 70.8044 mean, 283.488 max, 46.382 min
HTTP response codes:
  code 200 -- 500
Turn on Agressive Drupal Cacheing
1000 fetches, 5 max parallel, 6.452e+06 bytes, in 12.2807 seconds
6452 mean bytes/connection
81.4287 fetches/sec, 525378 bytes/sec
msecs/connect: 4.79381 mean, 86.273 max, 1.9 min
msecs/first-response: 50.7257 mean, 129.51 max, 15.991 min
HTTP response codes:
  code 200 -- 1000