Did you try measuring on eg, edwardk's gl package?
On Thu, Nov 20, 2014 at 12:52 PM, Merijn Verstraaten wrote: Hey, I'm not really happy with an explicit extension list passed through flags,
as it seems far to manual. It doesn't strike me as a very significant
problem as my current work-in-progress patch only resorts to scanning the
directory listing if none of the existing extensions are found. It seems unlikely that extremely large directories are in the search path.
I don't think we're expecting anyone to have thousands of files in their
module directories (and even thousands would take 0 time to scan...). We
already try all search paths during probing so the extra overhead from
large number of search paths shouldn't be substantially more than we have
now. As for the weird FS support, I really don't think it's GHC's job to
support people doing ridiculous things like "compiling on a filesystem that
doesn't support directory listings", I mean, come on! To be honest, I consider both directories with huge numbers of files (keep
in mind, we'd only scan the actual module sub-directory AND that we'd need
to run into directories with tens if not hundreds of thousands files to
notice any real slowdown) and weird filesystems that don't support
directory listing cases of "so don't do that, then". Especially since these
are only problems for users using non-standard module extensions. Cheers,
Merijn On 20 Nov 2014, at 2:40, Sven Panne [...] With your extensions it will have to read the directory contents.
In
most situations, that should be fine, but it might cause minor
inconveniences with very large directories, many search paths (-i flags)
and/or very weird file systems (compiling from a FUSE-mounted
HTTP-Server that does not support directory listing? Would work now...) Hmmm, IMHO reading directory contents is not a good idea for a
compiler, for just the reasons you mentioned. A fixed set of extensions (e.g. just "md" and "tex") would avoid this
problem, but goes against the spirit of the proposal. I think we can get the best of both worlds by adding a compiler flag,
e.g. --literate-extensions=md,tex. This way the compiler still has to
probe only a finite set of filenames *and* we are still flexible. ghc-devs mailing list
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