Re: how to speed up "git log"?

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Feb 11, 2007, 16:49 UTC
Message-ID: <Pine.LNX.4.63.0702111745170.22628@wbgn013.biozentrum.uni-wuerzburg.de>
In-Reply-To: <200702111252.28393.bruno@clisp.org>

Hi,

On Sun, 11 Feb 2007, Bruno Haible wrote:

Show 8 quoted lines

> Are there some known tricks to speed up the operation of "git log"?
> 
> On a file in a local copy of the coreutils git repository,
> "git log tr.c > output" takes
>   - 33 seconds of CPU time (33 user, 0 system) on a Linux/x86 500MHz system,
>   - 24 seconds of CPU time (12 user, 12 system) on a MacOS X PowerPC 1.1 GHz
>     system.
> The result shows only 147 commits and a total of 40 KB textual output.

Yes, because there were only 147 commits which changed the file. But git looked at all commits to find that.

Basically, we don't do file versions. File versions do not make sense, since they strip away the context. See also

http://news.gmane.org/group/gmane.comp.version-control.git/thread=37838

for a real flamewar revolving around that very subject.

> 1) Why so much user CPU time?

See above.

Plus, you are probably not really interested in _all_ revisions changing that file, are you? Usually the output of git-log -- even with pathname filtering -- starts almost instantaneous, and is piped to your pager. So, your numbers are misleading.

> 2) Why so much system CPU time, but only on MacOS X?

Probably the mmap() problem. Does it go away when you use git 1.5.0-rc4?

Hth, Dscho