From: Elijah Newren <newren@gmail.com>
To: Alban Gruin <alban.gruin@gmail.com>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>,
"Git Mailing List" <git@vger.kernel.org>,
"Ævar Arnfjörð" <avarab@gmail.com>,
"Eugeniu Rosca" <erosca@de.adit-jv.com>,
"Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
"Eugeniu Rosca" <roscaeugeniu@gmail.com>,
"Phillip Wood" <phillip.wood@dunelm.org.uk>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v1] rebase -i: stop checking out the tip of the branch to rebase
Date: Tue, 21 Jan 2020 12:07:20 -0800 [thread overview]
Message-ID: <CABPp-BEMZS4b_iYqP8nw0Oegfdx4DQadSwp00mXKPiaV58Pbpw@mail.gmail.com> (raw)
In-Reply-To: <20200121191857.23047-1-alban.gruin@gmail.com>
Hi Alban,
// Adding Phillip and Johannes since they know the sequencer internals
very well.
On Tue, Jan 21, 2020 at 11:21 AM Alban Gruin <alban.gruin@gmail.com> wrote:
>
> One of the first things done by the interactive rebase is to make a todo
> list. This requires knowledge of the commit range to rebase. To get
> the oid of the last commit of the range, the tip of the branch to rebase
> is checked out with prepare_branch_to_be_rebased(), then the oid of the
> HEAD is read. On big repositories, it's a performance penalty: the user
> may have to wait before editing the todo list while git is extracting the
> branch silently (because git-checkout is silenced here). After this,
> the head of the branch is not even modified.
>
> Since we already have the oid of the tip of the branch in
> `opts->orig_head', it's useless to switch to this commit.
>
> This removes the call to prepare_branch_to_be_rebased() in
> do_interactive_rebase(), and adds a `orig_head' parameter to
> get_revision_ranges(). prepare_branch_to_be_rebased() is removed as it
> is no longer used.
>
> This introduces a visible change: as we do not switch on the tip of the
> branch to rebase, no reflog entry is created at the beginning of the
> rebase for it.
Oh, sweet, thanks for digging in. I had also dug in just after the
report, but not quite far enough as I still had failing tests and I
was feeling a bit stretched thin on other projects so I punted hoping
that SZEDER would post something. Looks like the orig_head thing was
probably what I was missing.
I was a little surprised that there wasn't any regression test that
needed to be modified, as it reminded me of a previous conversation
about excessive work in the interactive backend[1], but after looking
it up that was apparently about too many calls to commit rather than
too many calls to checkout.
[1] https://lore.kernel.org/git/nycvar.QRO.7.76.6.1811121614190.39@tvgsbejvaqbjf.bet/
> Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
> Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
> ---
>
> Notes:
> Improvements brought by this patch:
>
> Before:
>
> $ time git rebase -m --onto v4.18 463fa44eec2fef50~ 463fa44eec2fef50
>
> real 0m8,940s
> user 0m6,830s
> sys 0m2,121s
>
> After:
>
> $ time git rebase -m --onto v4.18 463fa44eec2fef50~ 463fa44eec2fef50
>
> real 0m1,834s
> user 0m0,916s
> sys 0m0,206s
Nice...do we want to mention this in the commit message proper too?
>
> Both tests have been performed on a 5400 RPM SATA III hard drive.
>
> builtin/rebase.c | 18 +++++-------------
> sequencer.c | 14 --------------
> sequencer.h | 3 ---
> 3 files changed, 5 insertions(+), 30 deletions(-)
>
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 8081741f8a..6154ad8fa5 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -246,21 +246,17 @@ static int edit_todo_file(unsigned flags)
> }
>
> static int get_revision_ranges(struct commit *upstream, struct commit *onto,
> - const char **head_hash,
> + struct object_id *orig_head, const char **head_hash,
> char **revisions, char **shortrevisions)
> {
> struct commit *base_rev = upstream ? upstream : onto;
> const char *shorthead;
> - struct object_id orig_head;
> -
> - if (get_oid("HEAD", &orig_head))
> - return error(_("no HEAD?"));
>
> - *head_hash = find_unique_abbrev(&orig_head, GIT_MAX_HEXSZ);
> + *head_hash = find_unique_abbrev(orig_head, GIT_MAX_HEXSZ);
> *revisions = xstrfmt("%s...%s", oid_to_hex(&base_rev->object.oid),
> *head_hash);
>
> - shorthead = find_unique_abbrev(&orig_head, DEFAULT_ABBREV);
> + shorthead = find_unique_abbrev(orig_head, DEFAULT_ABBREV);
>
> if (upstream) {
> const char *shortrev;
> @@ -314,12 +310,8 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
> struct replay_opts replay = get_replay_opts(opts);
> struct string_list commands = STRING_LIST_INIT_DUP;
>
> - if (prepare_branch_to_be_rebased(the_repository, &replay,
> - opts->switch_to))
> - return -1;
> -
> - if (get_revision_ranges(opts->upstream, opts->onto, &head_hash,
> - &revisions, &shortrevisions))
> + if (get_revision_ranges(opts->upstream, opts->onto, &opts->orig_head,
> + &head_hash, &revisions, &shortrevisions))
> return -1;
>
> if (init_basic_state(&replay,
> diff --git a/sequencer.c b/sequencer.c
> index b9dbf1adb0..4dc245d7ec 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -3715,20 +3715,6 @@ static int run_git_checkout(struct repository *r, struct replay_opts *opts,
> return ret;
> }
>
> -int prepare_branch_to_be_rebased(struct repository *r, struct replay_opts *opts,
> - const char *commit)
> -{
> - const char *action;
> -
> - if (commit && *commit) {
> - action = reflog_message(opts, "start", "checkout %s", commit);
> - if (run_git_checkout(r, opts, commit, action))
> - return error(_("could not checkout %s"), commit);
> - }
> -
> - return 0;
> -}
> -
> static int checkout_onto(struct repository *r, struct replay_opts *opts,
> const char *onto_name, const struct object_id *onto,
> const char *orig_head)
> diff --git a/sequencer.h b/sequencer.h
> index 9f9ae291e3..74f1e2673e 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -190,9 +190,6 @@ void commit_post_rewrite(struct repository *r,
> const struct commit *current_head,
> const struct object_id *new_head);
>
> -int prepare_branch_to_be_rebased(struct repository *r, struct replay_opts *opts,
> - const char *commit);
> -
> #define SUMMARY_INITIAL_COMMIT (1 << 0)
> #define SUMMARY_SHOW_AUTHOR_DATE (1 << 1)
> void print_commit_summary(struct repository *repo,
> --
> 2.24.1
The code looks reasonable to me, but I'm still not completely familiar
with all the rebase and sequencer code so I'm hoping Phillip or
Johannes can give a thumbs up.
Thanks for digging into this and figuring out the bits that I missed
when I tried.
Elijah
next prev parent reply other threads:[~2020-01-21 20:07 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-08 21:43 Unreliable 'git rebase --onto' Eugeniu Rosca
2020-01-08 22:35 ` SZEDER Gábor
2020-01-09 0:55 ` Elijah Newren
2020-01-09 15:03 ` SZEDER Gábor
2020-01-09 17:53 ` Elijah Newren
2020-01-21 19:18 ` [PATCH v1] rebase -i: stop checking out the tip of the branch to rebase Alban Gruin
2020-01-21 20:07 ` Elijah Newren [this message]
2020-01-22 20:24 ` Junio C Hamano
2020-01-22 20:47 ` Junio C Hamano
2020-01-24 14:45 ` Alban Gruin
2020-01-24 14:45 ` [PATCH v2] " Alban Gruin
2020-01-24 14:55 ` Alban Gruin
2020-01-24 18:12 ` Junio C Hamano
2020-01-24 15:05 ` [PATCH v3] " Alban Gruin
2020-01-24 18:30 ` Junio C Hamano
2020-02-05 14:31 ` Johannes Schindelin
2020-01-24 17:11 ` [PATCH v2] " Andrei Rybak
2020-01-09 11:13 ` Unreliable 'git rebase --onto' Eugeniu Rosca
[not found] ` <CABPp-BHsyMOz+hi7EYoAnAWfzms7FRfwqCoarnu8H+vyDoN6SQ@mail.gmail.com>
2020-01-09 10:53 ` Eugeniu Rosca
2020-01-09 18:05 ` Elijah Newren
2020-01-10 0:06 ` Eugeniu Rosca
2020-01-10 2:35 ` Elijah Newren
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