Re: org-persist-write slow when pp-use-max-width is t

[Ihor Radchenko]

Michael Eliachevitch <m.eliachevitch@posteo.de> writes:

> I was wondering why kill-emacs emacs takes over a minute and after some 
> profiling I found out that the call to org-persist-write-all takes long when 
> pp-use-max-width is set to t and pp-max-width is also set (in my case to t, 
> the window-width), which enables line folding in pp. The pp-call happens in 
> org-persist--write-elisp-file when it is called by org-persist-write:index 
> with the pp-parameter set to t. Maybe it's clearer with the following excerpt 
> of my CPU-profile:
>
>        38009  96%      - org-persist-write-all
>        38009  96%       - org-persist-write
>        37703  95%        - mapcar
>        37703  95%         - #<compiled 0x42bf9b75c0e2209>
>        37703  95%          - org-persist-write:index
>        37703  95%           - org-persist--write-elisp-file
>        37703  95%            - pp
>        37703  95%             - pp-to-string
>        37703  95%              - pp-emacs-lisp-code
>        37687  95%               + pp--insert-lisp
>
> Setting pp-use-max-width to nil made the function call almost instantanteous.
>
> I had enabled pp-use-max-width in the past when pretty-printing the results 
> of interactive elisp sessions (like pp-eval-last-sexp). I didn't think this 
> would affect how other packages would save their data and I didn't expect 
> this would result in such a performance hit. Possibly this is not an issue 
> with org-mode or pp but just my own mistake of not being aware that pp is 
> used as a library by other packages and thus customizing its behaviour has 
> global effects.
>
> Not sure if the org mailing list is the best place to report this 
> observation. What org could do is to use a let-binding to temporarily set 
> pp-use-max-width to nil to disable line folding. Or do you think that some 
> users might care that their cache files are formatted prettily according to 
> their customization options?
>
> If you think this is not an issue with org-mode, maybe I/we could forward 
> this to the pp-maintainers, as it's in emacs core possibly to emacs-devel? I 
> think at least a warning in the variable documentation about performance hits 
> might have been helpful.

Thanks for reporting!
pp-max-width has been introduced in Emacs 29.
The fact that pp becomes too slow is likely something to be fixed before
the next Emacs release.

While we can work around this issue on Org side, I'd prefer to ask Emacs
developers first and see if they can come up with a fix.

I suggest you to file a bug report to Emacs.
You may provide the contents of your org-persist-index-file inside
org-persist-directory. AFAIU, it is what is taking a lot of time to
print.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>