Re: [hacky PATCH 0/2] speeding up trivial for-each-ref invocations

[ZheNing Hu <adlternative@gmail.com>]

Jeff King <peff@peff.net> 于2021年9月8日周三 上午1:28写道：
>
> On Mon, Sep 06, 2021 at 09:30:45PM +0800, ZheNing Hu wrote:
>
> > Jeff King <peff@peff.net> 于2021年9月5日周日 下午8:49写道：
> > >
> > > On Sun, Sep 05, 2021 at 04:19:53PM +0800, ZheNing Hu wrote:
> > >
> > > > > In this version there are 2 patches, tested against 'git for-each-ref
> > > > > --format="%(objectname) %(refname)"' on a fully packed repo with 500k
> > > > > refs:
> > > > >
> > > >
> > > > Regarding this 500k refs, is there any way I can reproduce it?
> > >
> > > Try this in a clone of linux.git (or any other repo):
> > >
> > >   git rev-list HEAD |
> > >   head -500000 |
> > >   perl -lne 'print "create refs/foo/$. $_"' |
> > >   git update-ref --stdin
> > >
> > >   git pack-refs --all --prune
> > >
> >
> > Sorry, It seems that the above command is difficult to complete on my
> > machine (it took more than ten minutes). It may be stuck on git update-ref.
> > So I tried to reproduce it in a repo which containing 76K refs:
>
> Mine didn't take nearly that wrong, but it does depend on filesystem and
> disk performance. It's going to create 500k lock files in refs/foo. :)
>
> You can cheat a bit like this:
>
>   {
>     # grab existing packed refs; don't worry about peel lines or the
>     # header comment, we're producing a lowest-common denominator
>     # version of the file
>     grep '^[0-9a-f]' packed-refs
>
>     # now make our new fake refs
>     git rev-list HEAD |
>     head -500000 |
>     perl -lne 'print "$_ refs/foo/$."'
>   } >packed-refs.tmp
>   mv packed-refs.tmp packed-refs
>
>   # and now ask Git to repack to get everything sorted, etc
>   git pack-refs --all --prune
>
> It sounds like you were able to come up with a smaller version to play
> with anyway, but I enjoy coming up with such hacks. :)
>

Thanks, this method really works. :-)

> -Peff

--
ZheNing Hu