Re: Performance regression in `git log --follow`

[Miklos Vajna <vmiklos@collabora.com>]

Hi Patrick,

On Tue, Oct 13, 2026 at 03:55:01PM +0200, Patrick Steinhardt <ps@pks.im> wrote:
> I've bisected the regression to 304812ed33 (log: improve --follow
> following renames for non-linear history, 2026-06-22). I don't have time
> right now to debug any further, so I decided to just forward the report
> to the mailing list. I've also Cc'd the original author of the above
> commit.

Thanks for the report.

To some extent, this is expected: previously log --follow had a design
issue, as described at
<https://lore.kernel.org/git/xmqqjysz7r41.fsf@gitster.g/>. Now log
--follow finds more commits has it traverses non-linear history, which
takes more time.

Let's see if we can find some creative solution that keeps the new
design (storing / restoring the path to follow as you traverse
non-linear history) and at the same time improves performance for your
use-case. Quite possibly my patch is/was naive and we can avoid some not
needed work while still correctly following a path across renames.

I see Gabor already commented in the thread and same some ideas, but I
haven't read those yet.

Regards,

Miklos