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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