On Tue, Aug 27, 2019 at 02:59:30PM -0400, Jeff King wrote:
> On Tue, Aug 27, 2019 at 12:04:27PM +0200, Uwe Kleine-König wrote:
>
> > $ 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.
>
> That's not that many refs. Are they mostly unpacked? Loose refs are
> awful on a cold cache, since it's one inode per ref (or worse, since it
> has walk the directories, too).
>
> Try:
>
> find .git/refs -type f | wc -l
u...@dude.ptx:/ptx/src/git/linux.git$ find refs -type f | wc -l
2874
(Note this is a bare repository. So I used refs instead of .git/refs.)
> to see the loose ones. If there are a lot, try:
>
> git pack-refs --prune --all
>
> (or just "git gc", which does this).
This is a daily updated mirror that is also incrementally backed up. I
repack from time to time, but hesitate to do this regularily as each
time I repack the next backup run is "expensive" and I get many small
packs. I did this now anyhow.
After that I have:
$ find objects/[0-9a-f][0-9a-f] -type f | wc -l
166
$ find objects/pack | wc -l
98
> Modern versions of Git should delete any leftover empty directories
> after pruning the loose variants, but I think won't go out of their way
> to remove ones they didn't delete from. And those are still expensive to
> walk on a cold cache. If it's still slow, try:
>
> find .git/refs/* -type d | xargs rmdir -v
There were a few:
$ find refs/ -depth -type d -empty -print -delete | wc -l
147
(Oops, after the repacking above this also removed ./refs which I had to
restore to make git recognize this as a repository.)
With these two things done it is a bit faster:
$ 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 0m11.022s
user 0m0.321s
sys 0m0.248s
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
