size of cache

with my application, it seems that size of cache has great effect:
from 512 Kb of L2 cache to 1Mb boost performance with a factor 3 and
20% again from 1Mb L2 cache to 2Mb L2 cache.
I don't understand why a 512Kb cache L2 is too small to fit the data's
does it exist a tool to trace processor activity and confirm that
processor is waiting for memory ?
does it exist a tool to snapshot postgres activity and understand
where we spend time and potentialy avoid the bottleneck ?

thanks for your tips.

--
Jean-Max Reymond
CKR Solutions Open Source
Nice France
http://www.ckr-solutions.com