TYPO3 Core

The workspace view in the backend has a feature to calculate the percentage of differences between live and workspace version.
This implementation iterates over each record and each field by using the PHP method similar_text().
The complexity of similar_text() is measured with O(n^3) which quickly can turn into a nice waiting period if string length is more than approx 4000 characters.

• use a different approach if string length is more than 2048 or 4096 characters
• remove MD5 sums on files which also can turn out in a nice waiting period
• do not resolve fields that hold m:n relations to reduce tree complexity and database queries

Maybe disable this feature in newer versions at all or us a simple MD5 based comparison of the field contents which reads then "n% of the all fields have been modified".