Re: vc-dir operation is very slow on large git repositories in Emacs 26.1

[Eli Zaretskii <eliz@gnu.org>]

> From: Alex Harsanyi <alexharsanyi@gmail.com>
> Date: Wed, 20 Jun 2018 18:50:12 +0800
> 
> I have a somewhat large git repository at work (51556 files) and
> Emacs 26.1 is very slow when updating the *vc-dir* buffer: I
> start emacs with the "-Q -no-site-file" and it takes
> approximately 2 minutes to update the vc-dir buffer. Emacs 25.2,
> on the same machine and repository, will complete this operation
> in a few seconds.  This is on a Windows machine and I use the
> prebuilt binaries downloaded from the gnu.org website for both
> versions.
> 
> The operation that takes a long time is the ls-files
> operation, "git --no-pager ls-files -z -c -s --", but running
> that command in a terminal completes in less than a second.

So you are saying that in Emacs 25.2 this slow Git command was not
invoked in your scenario?

> I cloned the Emacs git repository (which has 3683 files) and a
> vc-dir operation in Emacs 26.1 takes 7 seconds on my machine,
> compared to less than 1 second in Emacs 25.2.  I noticed this
> speed difference on my home computer as well.

FWIW, I get about 2 sec for this in the Emacs repository, and I see no
perceptible difference between Emacs 25.2 and Emacs 26.1.

> If not, I would appreciate some suggestions on how to further
> diagnose the cause of this issue, as it seems it is related to my
> computer.

Where did you get the Emacs binaries for the 2 above-mentioned
versions?