Re: Willing to debug bug #3542 (23.0.94; File access via UNC path slow again under Windows)

[Eli Zaretskii <eliz@gnu.org>]

> From: "Drew Adams" <drew.adams@oracle.com>
> Cc: "'Eli Zaretskii'" <eliz@gnu.org>, <emacs-devel@gnu.org>
> Date: Thu, 9 Jul 2009 09:11:10 -0700
> 
> Dumb question: Is there a way for Emacs to know whether the format is NTFS or
> FAT(32)?

Yes (and it does).

> If so, then Emacs could use nil for FAT volumes.

Doing that by default is too radical, IMO.  Having this option non-nil
on FAT/FAT32/XFAT has its merits, although less so than on NTFS.  And
the speedup for local drives would be minimal.

> (If not, it seems like nil would be the best default value.)

I prefer to carry out a plan I have for speeding up the emulated
`stat' so that it works faster without sacrificing features.  Those
features are important for important use-cases, such as support for
files and directories that are private to the user (inaccessible by
other Windows users).

Note that the slow-down due to additional functionality is only
acutely visible when we call file-attributes on long lists of files,
like when it is called from directory-files-and-attributes.  A single
call to file-attributes for a single file is very fast even for
networked drives.

I think nil should be the last resort, for those pathological cases
where disk access is dog slow no matter what you do.  Setting the
option to nil by default would punish too many use-cases for now good
reason.