1) Install the php extension xdebug
Enable this extension and profiling in xdebug settings
xdebug.profiler_enable = 1
Please note these 2 options (where to put profile files):
2) Deflate the profiling I've found myself on a development machine, then feed it to this utility as QCacheGrind. It will quickly analyze them and give you what methods, how many times have you volunteered, and how much CPU time left for processing. You can sort the results.
3) xdebug In production better off.