Delving deeper into plugins memoru usage

Disclaimer: This is perhaps not a Pro Site issue but I choose this plugin because it is the one where warnings are most often present. On occasions, our WordPress install throws PHP errors and warnings saying that functions in Pro Sites could not be loaded (a few times I have seen this on WPMUDev updater and Ultimate Facebook as well) because there is not enough memory available.

This might be useful to know

define(‘WP_MEMORY_LIMIT’, ‘128MB’:wink:;

MySQL 5.5.8

PHP Version 5.3.5

Maximum concurrent threads 50

memory_limit 128 MB

max_execution_time 180 sek

max_input_time 600 sek

upload_max_filesize 120 MB

post_max_size 120 MB

Running on Amazon Web Services

But what I am especially looking for is a way to dig deeper into memory usage so I can find out what is really causing these spikes. Anybody knows what I can do?