Determine cause of high memory consumption

Problem/Motivation

For #2289201: [Meta] Make drupal install and run within reasonable php memory limits so we can reset the memory requirements to lower levels

In order to reduce the memory requirements, we need to know what causes the high memory usage.

Proposed resolution

Perform an analysis to determine what exactly causes the heavy memory consumption.

As we find places, open child issues. (make them related to 2289201)

Remaining tasks

• come up with a strategy for performing the analysis.

User interface changes

No.

API changes

No.