bug#41646: Startup in Windows is very slow when load-path contains many

[Lin Sun <sunlin7.mail@gmail.com>]

On Fri, Nov 1, 2024 at 8:17 AM Eli Zaretskii <eliz@gnu.org> wrote:
> ...
> How will the '"file1" "file2" ...' part be created?

For the Emacs built in paths, we can create the (<path> [files])
during bootstrap and write to the "subdirs.el", then it will push the
extended (<path>, files...) into `load-path'.


On Fri, Nov 1, 2024 at 1:11 PM Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> > Yes, introducing this new variable will increase the complexity to the
> > end user.
>
> Exactly, and I think we should first try to solve the problem without
> exposing the user to such complexity.
> ...
> >> and then `load` can use `load-prefix-trim-load-path` to iterate on
> >> a much shorter `load-path`.
>
> Note that this above proposal should be transparent to the end user (tho
> it requires extra work on the `package.el` side): e.g. funny changes
> to `load-path` would be handled without fuss.
>
> >> I'm not completely sure if it's a good idea, tho: I'd really prefer
> >> a solution that doesn't require any change to any package management
> >> code, which instead uses a cache (updated/filled automatically) of all
> >> the files found in all the `load-path` directories.
> > If that, we have to track the file/path changes in each entry of
> > load-path, it may not be possible for all the supported OSs.
>
> We can easily detect changes to `load-path` itself, of course, but as
> for changes to the content of the directories in `load-path` that would
> be more difficult&costly, admittedly.  My plan was to do nothing
> about it (i.e. allow the cache to go stale): if we use the cache only to
> tell `load` in which directory to look for the file, it should usually
> be safe because IME it's rare for files to be added/removed from
> directories such that it changes from which directory a given ELisp file
> is loaded.  But of course we could also make efforts to try and keep our
> cache consistent, e.g. via OS-level notification infrastructure or
> by flushing the cache after a N seconds.

Agree the changes are difficult and costly.

The inotify way is hard to work on all OSes, and the cache need very
carefully maintenance policy.