If you are in admin and click on a scheduled job with a lot of text in history tab, Episerver will respond very slow. This can occur for instance for the Episerver Find schuduled job which can create huge amount of text in the history tab per job in admin. Limiting the number of chars to 2000 for the message worked wonders for performance though. So suggestion is to either set a fixed limit to x number of chars for description of the scheduled job or some other similar change to avoid this issue. Should be an easy fix.
Workaround is to create an SQL script to remove history items which includes a text that is above 2000 chars.
I filed a bug and will let CMS Core team handle it. Thanks for your feedback!