From: Mike Hommey <mh@glandium.org>
Date: Fri, 07 Nov 2008 21:28:36 GMT
Subject: Re: absurdly slow git-diff
Message-ID: <20081107212836.GA22717@glandium.org>
In-Reply-To: <20081107200126.GA20284@toroid.org>

On Sat, Nov 08, 2008 at 01:31:27AM +0530, Abhijit Menon-Sen wrote:
> I have a 240k-line file, and I change one character on every sixth line.
> The resulting diff gives git serious indigestion:
> 
> $ git --version
> git version 1.6.0.3.640.g6331a
> $ mkdir a; cd a; git init
> Initialized empty Git repository in /home/ams/a/.git/
> $ cp ../1 .; git add 1; git commit -q -m 1
> $ cp ../2 1; git add 1; git commit -q -m 2 

You don't need to go that far. You can stop at cp ../2 1 and run git
diff from there.

All the time is spent in the two loops in
xdiff/xprepare.c:xdl_cleanup_records, on line 400 and 412.

I'll leave the rest of the investigation to people actually knowing this
code ;)

Mike