Re: [bug] "git bisect old v3.0" takes 21 mins on Linux repo

From: D. Ben Knoble <ben.knoble@gmail.com>
Date: Jan 14, 2025, 22:21 UTC
Message-ID: <CALnO6CAzN1oeT4tMjJ1Qm4dW0xdVkVKHJ39oJTX8R8E614FH6g@mail.gmail.com>
In-Reply-To: <19461b87a5c.5a2ea74016716.8214238482389812984@zohomail.com>

On Mon, Jan 13, 2025 at 5:11 PM Askar Safin <safinaskar@zohomail.com> wrote:

>
> Hi. This is bug report. "git bisect" is unacceptable slow on Linux repo.

That may be a bit inflammatory ;)

Show 25 quoted lines

>
> Steps to reproduce:
>
> ===
> d-user@comp:/tmp/t$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
> Cloning into 'linux'...
> remote: Enumerating objects: 13079335, done.
> remote: Counting objects: 100% (153/153), done.
> remote: Compressing objects: 100% (108/108), done.
> remote: Total 13079335 (delta 84), reused 70 (delta 45), pack-reused 13079182
> Receiving objects: 100% (13079335/13079335), 5.18 GiB | 13.72 MiB/s, done.
> Resolving deltas: 100% (10454171/10454171), done.
> Updating files: 100% (87234/87234), done.
> d-user@comp:/tmp/t$ cd linux
> d-user@comp:/tmp/t/linux$ git bisect start
> status: waiting for both good and bad commits
> d-user@comp:/tmp/t/linux$ git bisect new v6.13-rc7
> status: waiting for good commit(s), bad commit known
> d-user@comp:/tmp/t/linux$ time -p git bisect old v3.0
> Bisecting: 535608 revisions left to test after this (roughly 19 steps)
> [62606c224d72a98c35d21a849f95cccf95b0a252] Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
> real 1293.32
> user 1291.70
> sys 1.41
> ===

FWIW:

$ time git rev-list --count v3.0...v6.13-rc7 1070175 git rev-list --count v3.0...v6.13-rc7 13,57s user 1,41s system 96% cpu 15,466 total

That's a large number of revisions to bisect. Further,

# --force needed because my filesystem is case-insensitive :eyeroll: $ time git checkout [--force] 62606c224d72a98c35d21a849f95cccf95b0a252 git checkout --force 62606c224d72a98c35d21a849f95cccf95b0a252 7,94s user 18,54s system 96% cpu 27,360 total

Using pathspecs or a smaller commit range should help speed up the start. (On a recent git, the helper is gone, so I'm not sure where the time is spent—but I do notice that `git bisect start v6.13-rc7 v3.0` is slow enough that I've killed it rather than wait.)

-- 
D. Ben Knoble