We have observed performance issues when saving User Profiles, this has led us to find on lines 

#316 and #320 of user/editadvanced.php the line:

 \core\session\manager::gc(); 

This line is now unnecessary with the addition of the \core\task\session_cleanup_task task that's been appended to the LMS. The additional firing of the event causes a number of performance issues, increasing the post result to ~10m when changing other users profile fields (not same user). 

Removing said fields remove the extra hang-time created when changing the field data.