git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Junio C Hamano <gitster@pobox.com>
To: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, szeder.dev@gmail.com, avarab@gmail.com,
	abhishekkumar8222@gmail.com, me@ttaylorr.com,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 0/2] Accelerate "git merge-base --is-ancestor"
Date: Wed, 17 Jun 2020 13:46:56 -0700	[thread overview]
Message-ID: <xmqqzh91s9mn.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <pull.664.git.1592414670.gitgitgadget@gmail.com> (Derrick Stolee via GitGitGadget's message of "Wed, 17 Jun 2020 17:24:27 +0000")

"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:

> It was recently [1] reported (and not-so-recently [2] reported) that "git
> merge-base --is-ancestor" can be pretty slow. In fact, it is regularly
> slower than "git branch --contains" or "git tag --contains", which are
> answering a "harder" query.
>
> [1] https://lore.kernel.org/git/20200607195347.GA8232@szeder.dev/
>
> [2] https://lore.kernel.org/git/87608bawoa.fsf@evledraar.gmail.com/
>
> The root cause is that the in_merge_base() implementation is skipping the
> fast can_all_from_reach() implementation and using paint_down_to_common()
> instead. Note that these are equivalent: a commit A is in the set of
> merge-bases between A and B if and only if B can reach A.

OK, so in short, this codepath was not taking advantage of the
generation numbers and that was the difference?


  parent reply	other threads:[~2020-06-17 20:47 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-17 17:24 [PATCH 0/2] Accelerate "git merge-base --is-ancestor" Derrick Stolee via GitGitGadget
2020-06-17 17:24 ` [PATCH 1/2] commit-reach: create repo_is_descendant_of() Derrick Stolee via GitGitGadget
2020-06-29 13:40   ` Taylor Blau
2020-06-30  1:45     ` Derrick Stolee
2020-06-17 17:24 ` [PATCH 2/2] commit-reach: use fast logic in repo_in_merge_base Derrick Stolee via GitGitGadget
2020-06-17 20:46 ` Junio C Hamano [this message]
2020-06-18  1:37   ` [PATCH 0/2] Accelerate "git merge-base --is-ancestor" Derrick Stolee
2020-06-19  6:10 ` Abhishek Kumar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=xmqqzh91s9mn.fsf@gitster.c.googlers.com \
    --to=gitster@pobox.com \
    --cc=abhishekkumar8222@gmail.com \
    --cc=avarab@gmail.com \
    --cc=dstolee@microsoft.com \
    --cc=git@vger.kernel.org \
    --cc=gitgitgadget@gmail.com \
    --cc=me@ttaylorr.com \
    --cc=szeder.dev@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).