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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 06 Jul 2009 23:01:19 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: emacs-devel@gnu.org
> 
> > From: Mathias Dahl <mathias.dahl@gmail.com>
> > Date: Mon, 6 Jul 2009 09:38:07 +0200
> > Cc: emacs-devel@gnu.org
> > 
> > //gbgfs1/archive75 is a share that contains 260 directories and three
> > files. The server is located in our office.
> > 
> > C-x d //gbgfs1/archive75 RET
> > 
> >  Emacs 22.1.1: 1 s
> >  Emacs 23.0.95.1: 95 s
> > 
> > So, that is about 95 times slower...
> 
> Ouch!  I'm quite sure I would have noticed such a terrible slowdown.
> 
> Let me time similar commands tomorrow in my office.

Sorry for a long delay.  I finally found a few minutes to look into
this.

First, I don't see a ~100-fold slowdown, I see only a 10-fold slowdown
(vs Emacs 22.3).  This is with a directory that has ~130
subdirectories.

I have a hypothesis for the reason of this slowdown, but I need a few
more facts from you to make sure the slowdown I see is caused by the
same factors as what you see:

 . Do you see significant difference in speed with cold and hot cache?
   That is, if you run Dired on the above directory, then kill the
   Dired buffer and immediately run Dired again on the same directory,
   what times do you see then in Emacs 23?

 . Does it help to set w32-get-true-file-attributes to nil?  If the
   previous test shows a significant speedup with hot cache, please
   try this with a cold cache, which may mean rebooting the machine
   where you are trying this, or maybe waiting long enough for the
   cache to "cool down" and in addition restarting Emacs (to get rid
   of Emacs's internal caching).

 . If w32-get-true-file-attributes does have a significant effect,
   please tell how many different user names and group names you see
   in the listing presented by "C-x d".

Thanks in advance.

> > Any tests in particular you want me to run?
> 
> Not yet.  But perhaps install StraceNT
> (http://stracent.en.softonic.com/) and see what are the differences
> between Emacs 22 and Emacs 23.  Maybe you will even be able to see the
> system call(s) that take most of this extra time.

Did you have a chance to do this?  If so, can you post the results?