Re: Why is git submodule slow under windows

From: Fredrik Gustafsson <iveqy@iveqy.com>
Date: Jul 18, 2014, 13:02 UTC
Message-ID: <20140718130241.GD14720@paksenarrion.iveqy.com>
In-Reply-To: <53C90E44.6030702@virtuell-zuhause.de>

On Fri, Jul 18, 2014 at 02:08:36PM +0200, Thomas Braun wrote:

Show 22 quoted lines

> Am 18.07.2014 12:14, schrieb Armbruster Joachim (BEG/EMS1):
> > Hello,
> > 
> > We split a monolithic repository into ~50 submodules. The stored data
> > has the same size. In the 1:1 comparison to the monolithic
> > repository, the submodule handling is very slow. Under Linux
> > everything remains fast, but windows is slow.
> > 
> > So, why is git getting slow when it has to deal with a lot of
> > submodules? I read something about the lack of the underlying cygwin
> > to handle NTFS in a efficient way. Is this the root cause, or are
> > there other causes also?
> > 
> 
> Hi,
> 
> I assume you are using the latetst git from https://msysgit.github.io on
> windows.
> 
> I would guess that submodules on windows are slow because
> git-submodules.sh is a shell script, and bash on windows is not really
> that fast.

My guess is that because the shell script uses fork() heavily and fork() is an expensive operation on Windows, that alone causes the slowddown.

I did a quick test a while back when I rewrote part of git-submodule.sh in lua and runned it on my repo with ~45 submodules. The speedup was significant and should be even bigger on windows.

-- 
Med vänlig hälsning
Fredrik Gustafsson

tel: 0733-608274
e-post: iveqy@iveqy.com