`Git` Performance issue in dulwich

Bug Report

Sometimes dvc exp show will take more than 10s to get a response, use Cprofile we notice that the time was costed in _load_file_contents in dulwich ,

related cprofile my.prof.zip

Description

Reproduce

Expected

Environment information

Output of dvc doctor:

$ dvc doctor

Additional Information (if any):

[pmrowla]

@dberenbaum we discussed it and this probably only requires filling out the libgit/pygit fetch/push implementations in scmrepo (currently we just only have dulwich implementation done, since there was never an explicit need for anything else until now).

libgit/pygit should at least be faster than dulwich, and this will be simpler than trying to dig into actual optimizations in dulwich upstream.

once that’s done we can revisit this later (and consider doing upstream optimizations) if there’s still a significant performance gap between using libgit/pygit and CLI git (but I don’t expect there will be a significant difference)

[karajan1001]

Takes about 1.16s.

 time git push ../vscode/ HEAD:refs/head/HEAD                                                                                                    -1-[ins][8:43:55]
Enumerating objects: 34763, done.
Counting objects: 100% (34763/34763), done.
Delta compression using up to 10 threads
Compressing objects: 100% (8562/8562), done.
Writing objects: 100% (34763/34763), 44.23 MiB | 74.38 MiB/s, done.
Total 34763 (delta 25344), reused 34733 (delta 25318), pack-reused 0
remote: Resolving deltas: 100% (25344/25344), done.
To ../vscode/
 * [new reference]       HEAD -> refs/head/HEAD
git push -f ../vscode/ HEAD:refs/head/HEAD  1.16s user 0.37s system 133% cpu 1.151 total