Re: [PATCH v2 1/2] dir: consider worktree config in path recursion

From: Elijah Newren <newren@gmail.com>
Date: May 24, 2022, 14:29 UTC
Message-ID: <CABPp-BGXRzYCvyM38dEUvQ125+VtRu++7L9UiRz98u+1=Lov7A@mail.gmail.com>
In-Reply-To: <xmqq7d6sm3e0.fsf@gitster.g>

On Wed, May 11, 2022 at 9:37 AM Junio C Hamano <gitster@pobox.com> wrote:

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>
> Goss Geppert <gg.oss.dev@gmail.com> writes:
>
> > diff --git a/dir.c b/dir.c
> > index f2b0f24210..a1886e61a3 100644
> > --- a/dir.c
> > +++ b/dir.c
> > @@ -1893,9 +1893,31 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
>

[...]

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> > +                     real_gitdir = real_pathdup(the_repository->gitdir, 0);
>
> This function is repeatedly called during the traversal.
>
> How expensive is it to keep calling real_pathdup() on the constant
> the_repository->gitdir just in case it might be the same as our true
> GIT_DIR?

I agree that treat_directory is called many times, but this real_pathdup() call is inside the "if (nested_repo)" block, so this new real_pathdup() invocation should occur very seldom. Or are you worried about cases where users have *very* large numbers of bare repositories nested under the working directory? Even in that case, which seems pathological to me, I'd suspect the is_nonbare_repository_dir() -> read_gitfile_gently()/is_git_directory() codepath (used to determine the value of nested_repo) would be much more expensive than this call to real_pathdup(), so would it be worth trying to optimize this real_pathdup() call away even in that rare case?