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From: Junio C Hamano <gitster@pobox.com>
To: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, me@ttaylorr.com, jnareb@gmail.com,
	garimasigit@gmail.com, Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 3/3] blame: use changed-path Bloom filters
Date: Sat, 11 Apr 2020 15:03:19 -0700	[thread overview]
Message-ID: <xmqq5ze5he8o.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <431fde6803140398eec0744c866616a0a78f9433.1586566981.git.gitgitgadget@gmail.com> (Derrick Stolee via GitGitGadget's message of "Sat, 11 Apr 2020 01:03:01 +0000")

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

> From: Derrick Stolee <dstolee@microsoft.com>
> Subject: Re: [PATCH 3/3] blame: use changed-path Bloom filters

Ahh, I almost forgot we spell Bloom with capital B, so I should go
back and amend the title of [2/3].

> When computing a blame, there is a section in find_origin() that
> computes a diff between a commit and one of its parents. When this
> is the first parent, we can check the Bloom filters before calling
> diff_tree_oid().
>
> In order to make this work with the blame machinery, we need to
> initialize a struct bloom_key with the initial path. But also, we
> need to add more keys to a list if a rename is detected. We then
> check to see if _any_ of these keys answer "maybe" in the diff.

Yes.  I think after gaining experience with this technique, we may
be able to speed up the "git log --follow" while correcting its
semantics at the same time.  The prospect is unnervingly exciting.

> Generally, this is a performance enhancement and should not
> change the behavior of 'git blame' in any way.

Absolutely.

> The lack of improvement for the MAINTAINERS file and the relatively
> modest improvement for the other examples can be easily explained.
> The blame machinery needs to compute line-level diffs to determine
> which lines were changed by each commit. That makes up a large
> proportion of the computation time, and this change does not
> attempt to improve on that section of the algorithm. The
> MAINTAINERS file is large and changed often, so it takes time to
> determine which lines were updated by which commit. In contrast,
> the code files are much smaller, and it takes longer to comute
> the line-by-line diff for a single patch on the Linux mailing
> lists.

Yup, tree-diff for a deeper path would benefit the most, and your
numbers were indeed impressive.

> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  blame.c         | 139 ++++++++++++++++++++++++++++++++++++++++++++----
>  blame.h         |   6 +++
>  builtin/blame.c |  10 ++++
>  3 files changed, 146 insertions(+), 9 deletions(-)

I am kind-a surprised how little additional code it takes to do
this.  Good job.

  reply	other threads:[~2020-04-11 22:03 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-11  1:02 [PATCH 0/3] Integrate changed-path Bloom filters with 'git blame' Derrick Stolee via GitGitGadget
2020-04-11  1:02 ` [PATCH 1/3] revision: complicated pathspecs disable filters Derrick Stolee via GitGitGadget
2020-04-11 21:40   ` Junio C Hamano
2020-04-13 11:49     ` Derrick Stolee
2020-04-14 18:25       ` Junio C Hamano
2020-04-15 13:27         ` Derrick Stolee
2020-04-15 18:37           ` Derrick Stolee
2020-04-15 19:32             ` Junio C Hamano
2020-04-15 19:39               ` Junio C Hamano
2020-04-15 21:25             ` Junio C Hamano
2020-04-16  0:56               ` Taylor Blau
2020-04-15 22:18             ` Jakub Narębski
2020-04-16  0:52               ` Taylor Blau
2020-04-16 13:26                 ` Derrick Stolee
2020-04-16 16:33                   ` Taylor Blau
2020-04-16 18:02                     ` Junio C Hamano
2020-04-12 22:22   ` Taylor Blau
2020-04-12 22:30     ` Junio C Hamano
2020-04-13  0:07       ` Taylor Blau
2020-04-13 11:54         ` Derrick Stolee
2020-04-11  1:03 ` [PATCH 2/3] commit: write commit-graph with bloom filters Derrick Stolee via GitGitGadget
2020-04-11 21:57   ` Junio C Hamano
2020-04-12 20:51     ` Taylor Blau
2020-04-13 12:08       ` Derrick Stolee
2020-04-13 22:11         ` Junio C Hamano
2020-04-11  1:03 ` [PATCH 3/3] blame: use changed-path Bloom filters Derrick Stolee via GitGitGadget
2020-04-11 22:03   ` Junio C Hamano [this message]
2020-04-12  7:39     ` Eric Sunshine
2020-04-11 21:30 ` [PATCH 0/3] Integrate changed-path Bloom filters with 'git blame' Junio C Hamano
2020-04-13 14:45 ` [PATCH v2 0/4] " Derrick Stolee via GitGitGadget
2020-04-13 14:45   ` [PATCH v2 1/4] revision: complicated pathspecs disable filters Derrick Stolee via GitGitGadget
2020-04-13 16:09     ` Taylor Blau
2020-04-13 22:18       ` Junio C Hamano
2020-04-13 14:45   ` [PATCH v2 2/4] commit: write commit-graph with Bloom filters Derrick Stolee via GitGitGadget
2020-04-13 16:12     ` Taylor Blau
2020-04-13 22:21       ` Junio C Hamano
2020-04-14 15:04         ` Derrick Stolee
2020-04-14 17:26           ` Junio C Hamano
2020-04-14 17:40             ` Derrick Stolee
2020-04-15  0:17               ` Taylor Blau
2020-04-13 14:45   ` [PATCH v2 3/4] commit-graph: write commit-graph in more tests Derrick Stolee via GitGitGadget
2020-04-13 14:45   ` [PATCH v2 4/4] blame: use changed-path Bloom filters Derrick Stolee via GitGitGadget
2020-04-13 16:21   ` [PATCH v2 0/4] Integrate changed-path Bloom filters with 'git blame' Taylor Blau
2020-04-16 20:14   ` [PATCH v3 0/3] " Derrick Stolee via GitGitGadget
2020-04-16 20:14     ` [PATCH v3 1/3] revision: complicated pathspecs disable filters Derrick Stolee via GitGitGadget
2020-06-07 20:33       ` SZEDER Gábor
2020-04-16 20:14     ` [PATCH v3 2/3] tests: write commit-graph with Bloom filters Derrick Stolee via GitGitGadget
2020-04-16 20:14     ` [PATCH v3 3/3] blame: use changed-path " Derrick Stolee via GitGitGadget

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