Re: [BUG] "git describe --match" performance

[Josh Poimboeuf <jpoimboe@kernel.org>]

On Thu, Oct 31, 2024 at 07:47:31AM -0400, Jeff King wrote:
> On Tue, Oct 29, 2024 at 09:43:22PM -0700, Josh Poimboeuf wrote:
> 
> > $ time git describe --match=v6.10-rc7 --debug
> > describe HEAD
> > No exact match on refs or tags, searching to describe
> > finished search at d8470b7c13e11c18cf14a7e3180f0b00e715e4f0
> >  annotated       1844 v6.10-rc7
> > traversed 1282750 commits
> > v6.10-rc7-1844-gc61e41121036
> > 
> > real	0m9.243s
> > user	0m8.940s
> > sys	0m0.268s
> > 
> > $ time git describe
> > v6.10-rc7-1844-gc61e41121036
> > 
> > real	0m0.149s
> > user	0m0.111s
> > sys	0m0.036s
> 
> There's more discussion of the actual solution in the nearby thread from
> Rasmus. But I did want to note one thing here: when I initially tried to
> reproduce your problem, my "slow" case was a lot less bad.
> 
> The reason is that I had a commit graph file to speed up traversal. So
> independent of the git-describe fix, you might want to try:
> 
>   git commit-graph write --reachable
> 
> That reduces the slow case for me by a factor of 10. And likewise other
> traversal operations should get faster.
> 
> I think we'll build the commit graph file by default these days when you
> run "git gc". But we don't build it immediately after cloning. Perhaps
> we should change that.

Hm... I actually ran "git gc" and it didn't seem to help at all.

-- 
Josh