Memory limit
Before, with twig, it was using a huge commit about 600MB (PHP).
Now, it works with 64MB (PHP) and huge diffs (like 9000 lines), it loads a chunk of 256 lines at max, then the rest is with setTimeout with line by line, so there is no blocking in the GUI at all. Maybe slower, but never blocking.
If you toggle the diff button (show/hide), it will pause rendering and it will only continue the long diff if it shows.