Speedup on large file after reconfiguring whitespace-mode

Speedup on large file after reconfiguring whitespace-mode

[Russell Adams]

I wanted to let others know about my recent experience tuning Org. I'm
on Emacs 29.3 with Org 9.7-pre from git.

I have a large file, 5MB, 134k lines, 4k example blocks, 1200 inline
images, 6500 timestamps. It grows rapidly as I use it for customer
support at a very active customer. I do try to archive completed tasks
twice a year to try and get it back under 100k lines.

I've had some performance problems with the file as it grows. Recently
I was trying to scroll up by just holding page up, and within seconds
Emacs would timeout and it could take up to 10 seconds being frozen
until it caught up.

I asked about this in the recent Org meetup, and I was given great
information about how the number of faces used in a file can strongly
influence the speed of navigation. I tested in fundamental mode and
still had slowdowns, and in emacs -Q it ran normally at full
speed. Something was up with faces.

I went to bisect my configuration. I don't use many packages, but I
dutifully bisected down all my use-packages calls until I had
none. The problem still persisted with no add-on packages.

I started digging into my configuration, and found that if I disabled
global-whitespace-mode the issue vanished. After some searches, it
appears that whitespace-mode highlights each space/tab/newline with a
face. In a small file that may not matter, but in bulk it was
crippling.

I changed whitespace-mode to use the display table where it
substitutes other characters for spaces instead of using faces, and the
performance problem was solved.

The following setting made all the difference:

(setq whitespace-style '(space-mark tab-mark))

Perhaps I can save someone else some time troubleshooting.

------------------------------------------------------------------
Russell Adams                            RLAdams@AdamsInfoServ.com
                                    https://www.adamsinfoserv.com/

Re: Speedup on large file after reconfiguring whitespace-mode

[Fraga, Eric]

Thank you.  Very helpful to know.

The other culprit, for me, is the presence of long tables.  I've learned
to hide any headline which includes such tables to help with
performance.

-- 
: Eric S Fraga, with org 9.7.8-7f2ce8 in Emacs 31.0.50