From: Philipp Zabel <p.zabel@pengutronix.de>
Date: Tue, 27 Aug 2019 09:12:06 GMT
Subject: Re: git slow unless piped to cat
Message-ID: <1566897126.4102.5.camel@pengutronix.de>
In-Reply-To: <20190827085637.g6cpnuofpteyfqfz@pengutronix.de>

On Tue, 2019-08-27 at 10:56 +0200, Uwe Kleine-König wrote:
> On Tue, Aug 27, 2019 at 10:41:11AM +0200, SZEDER Gábor wrote:
> > On Tue, Aug 27, 2019 at 10:15:59AM +0200, Uwe Kleine-König wrote:
> > > I have a problem here with git being slow in some situations.
> > > Using git 2.23.0 (from Debian) the effect is:
> > > 
> > > ukl@dude.ptx:/ptx/src/git/linux.git$ sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"; time git show v5.2
> > > tag v5.2
> > > ...
> > > 
> > > real	0m12.727s
> > > user	0m0.300s
> > > sys	0m0.371s
> > > 
> > > But to get the actual data isn't the problem:
> > > 
> > > ukl@dude.ptx:/ptx/src/git/linux.git$ sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"; time git show v5.2 | cat
> > > tag v5.2
> > > ...
> > > 
> > > real	0m0.764s
> > > user	0m0.014s
> > > sys	0m0.020s
> > > 
> > 
> > How does 'git --no-pager show v5.2' perform?  If it's as fast as the
> > case piping the output to cat, then look into what pager and pager
> > options you use.
> 
> 	ukl@dude.ptx:/ptx/src/git/linux.git$ sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"; time git --no-pager show v5.2
> 	tag v5.2
> 	...
> 
> 	real	0m13.225s
> 	user	0m0.355s
> 	sys	0m0.336s
> 
> So this doesn't seem to be the problem. Also the local configuration
> can be ruled out:
> 
> 	ukl@dude.ptx:/ptx/src/git/linux.git$ sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"; time env GIT_CONFIG_NOSYSTEM=1 HOME=/nonexistant XDG_CONFIG_HOME=/nonexistant git --no-pager show --no-color v5.2
> 	tag v5.2
> 	...
> 
> 	real	0m13.587s
> 	user	0m0.335s
> 	sys	0m0.336s
> 
> Thanks
> Uwe

Have you checked strace output? I see a directory walk through .git/refs
and .git/packed-refs if the output is not redirected.

regards
Philipp