Re: git slow unless piped to cat
- From
Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
- Date
- Aug 27, 2019, 10:04 UTC
- Message-ID
- <20190827100427.u3a5uvmylm5vddn2@pengutronix.de>
- In-Reply-To
- <20190827094407.GV20404@szeder.dev>
On Tue, Aug 27, 2019 at 11:44:07AM +0200, SZEDER Gábor wrote:
Show 66 quoted lines
> On Tue, Aug 27, 2019 at 11:12:06AM +0200, Philipp Zabel wrote: > > 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. > > That's a good point, 'git show/log' show decorations (refs pointing to > any commits shown) when the output is a terminal: > > $ git show v5.2 > [...] > commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 (HEAD -> master, tag: v5.2) > [...] > $ git show v5.2 |cat > [...] > commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 > [...]
> And indeed, if you have a lot of refs and cold cache, then that might
> account for a couple of seconds difference. So, how does 'git show
> --no-decorate v5.2' perform, and if it performs well, then how many
> refs do you have ('git for-each-ref |wc -l')?$ 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 --no-decorate v5.2 ...
real 0m1.041s user 0m0.000s sys 0m0.021s
$ git for-each-ref |wc -l 10013
So this is indeed the problem.
I'm a bit surprised that the default for --decorate depends on the output being a terminal.
Thanks for your help, I will think about what I want to do. Just using --no-decorate will work, but isn't nice either. Will test if just throwing away all those tags from linux-next will make this already better.
Best regards Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |