From: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
To: Elijah Newren <newren@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
Derrick Stolee <dstolee@microsoft.com>,
"brian m. carlson" <sandals@crustytoothpaste.net>,
Stefan Beller <stefanbeller@gmail.com>,
Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: [RFC PATCH 2/3] grep: honor sparse checkout patterns
Date: Thu, 23 Apr 2020 03:09:30 -0300 [thread overview]
Message-ID: <CAHd-oW7xaLcBskLM6bgqgnLukXnwW+bWvGM24Ao_9UxKwdXi3A@mail.gmail.com> (raw)
In-Reply-To: <CABPp-BGUf-4exGW23xka1twf2D=nFOz1CkD_f-rDX_AGdVEeDA@mail.gmail.com>
On Tue, Apr 21, 2020 at 12:08 AM Elijah Newren <newren@gmail.com> wrote:
>
> On Mon, Apr 20, 2020 at 7:11 PM Matheus Tavares Bernardino
> <matheus.bernardino@usp.br> wrote:
> >
> > I've been working on the file skipping mechanism using the sparsity
> > patterns directly. But I'm uncertain about some implementation
> > details. So I wanted to share my current plan with you, to get some
> > feedback before going deeper.
> >
> > The first idea was to load the sparsity patterns a priori and pass
> > them to grep_tree(), which recursively greps the entries of a given
> > tree object. If --recurse-submodules is given, however, we would also
> > need to load each surepo's sparse-checkout file on the fly (as the
> > subrepos are lazily initialized in grep_tree()'s call chain). That's
> > not a problem on its own. But in the most naive implementation, this
> > means unnecessarily re-loading the sparse-checkout files of the
> > submodules for each tree given to git-grep (as grep_tree() is called
> > separately for each one of them).
>
> Wouldn't loading the sparse-checkout files be fast compared to
> grepping a submodule for matching strings? And not just fast, but
> essentially in the noise and hard to even measure? I have a hard time
> fathoming parsing the sparse-checkout file for a submodule somehow
> appreciably affecting the cost of grepping through that submodule. If
> the submodule has a huge number of sparse-checkout patterns, that'll
> be because it has a ginormous number of files and grepping through
> them all would be way, way longer. If the submodule only has a few
> files, then the sparse-checkout file is only going to be a few lines
> at most.
Yeah, makes sense.
> Also, from another angle: I think the original intent of submodules
> was an alternate form of sparse-checkout/partial-clone, letting people
> deal with just their piece of the repo. As such, do we really even
> expect people to use sparse-checkouts and submodules together, let
> alone use them very heavily together? Sure, someone will use them,
> but I have a hard time imagining the scale of use of both features
> heavily enough for this to matter, especially since it also requires
> specifying multiple trees to grep (which is slightly unusual) in
> addition to the combination of these other features before your
> optimization here could kick in and be worthwhile.
>
> I'd be very tempted to just implement the most naive implementation
> and maybe leave a TODO note in the code for some future person to come
> along and optimize if it really matters, but I'd like to see numbers
> before we spend the development and maintenance effort on it because
> I'm having a hard time imagining any scale where it could matter.
You're right. I guess I got a little too excited about the
optimizations possibilities and neglected the fact that they might not
even be needed here.
Just to take a look at some numbers, I prototyped the naive
implementation and downloaded a testing repository[1] containing 8
submodules (or 14 counting the nested ones). For each of the
non-nested submodules, I added its .gitignore rules to the
sparse-checkout file (of course this doesn't make any sense for a
real-world usage, but I just wanted to populate the file with a large
quantity of valid rules, to test the parsing time). I also added the
rule '/*'. Then I ran:
git-grep --threads=1 --recurse-submodules -E "config_[a-z]+\(" $(cat /tmp/trees)
Where /tmp/trees contained about 120 trees in the said repository
(again, a probably unreal case, for testing purposes only). Then,
measuring the time spent only inside the function I created to load a
sparse-checkout file for a given 'struct repository', I got to the
following numbers:
Number of calls: 1531 (makes sense: ~120 trees and 14 submodules)
Percentage over the total time: 0.015%
Number of matches: 300897
And using 8 threads, I got the same numbers except for the percentage,
which was a little higher: 0.05%.
So, indeed, the overhead of re-loading the files is too insignificant.
And my cache idea was a premature and unnecessary optimization.
> > So my next idea was to implement a cache, mapping 'struct repository's
> > to 'struct pattern_list'. Well, not 'struct repository' itself, but
> > repo->gitdir. This way we could load each file once, store the pattern
> > list, and quickly retrieve the one that affect the repository
> > currently being grepped, whether it is a submodule or not. But, is
> > gitidir unique per repository? If not, could we use
> > repo_git_path(repo, "info/sparse-checkout") as the key?
> >
> > I already have a prototype implementation of the last idea (using
> > repo_git_path()). But I wanted to make sure, does this seem like a
> > good path? Or should we avoid the work of having this hashmap here and
> > do something else, as adding a 'struct pattern_list' to 'struct
> > repository', directly?
>
> Honestly, it sounds a bit like premature optimization to me. Sorry if
> that's disappointing since you've apparently already put some effort
> into this, and it sounds like you're on a good track for optimizing
> this if it were necessary, but I'm just having a hard time figuring
> out whether it'd really help and be worth the code complexity.
No problem! I'm glad to have this feedback now, while I'm still
working on v2 :) Now I can focus on what's really relevant. So thanks
again!
[1]: https://github.com/surevine/Metre
next prev parent reply other threads:[~2020-04-23 6:09 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 6:04 [RFC PATCH 0/3] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-03-24 6:11 ` [RFC PATCH 1/3] doc: grep: unify info on configuration variables Matheus Tavares
2020-03-24 7:57 ` Elijah Newren
2020-03-24 21:26 ` Junio C Hamano
2020-03-24 23:38 ` Matheus Tavares
2020-03-24 6:12 ` [RFC PATCH 2/3] grep: honor sparse checkout patterns Matheus Tavares
2020-03-24 7:15 ` Elijah Newren
2020-03-24 15:12 ` Derrick Stolee
2020-03-24 16:16 ` Elijah Newren
2020-03-24 17:02 ` Derrick Stolee
2020-03-24 23:01 ` Matheus Tavares Bernardino
2020-03-24 22:55 ` Matheus Tavares Bernardino
2020-04-21 2:10 ` Matheus Tavares Bernardino
2020-04-21 3:08 ` Elijah Newren
2020-04-22 12:08 ` Derrick Stolee
2020-04-23 6:09 ` Matheus Tavares Bernardino [this message]
2020-03-24 6:13 ` [RFC PATCH 3/3] grep: add option to ignore sparsity patterns Matheus Tavares
2020-03-24 7:54 ` Elijah Newren
2020-03-24 18:30 ` Junio C Hamano
2020-03-24 19:07 ` Elijah Newren
2020-03-25 20:18 ` Junio C Hamano
2020-03-30 3:23 ` Matheus Tavares Bernardino
2020-03-31 19:12 ` Elijah Newren
2020-03-31 20:02 ` Derrick Stolee
2020-04-27 17:15 ` Matheus Tavares Bernardino
2020-04-29 16:46 ` Elijah Newren
2020-04-29 17:21 ` Elijah Newren
2020-03-25 23:15 ` Matheus Tavares Bernardino
2020-03-26 6:02 ` Elijah Newren
2020-03-27 15:51 ` Junio C Hamano
2020-03-27 19:01 ` Elijah Newren
2020-03-30 1:12 ` Matheus Tavares Bernardino
2020-03-31 16:48 ` Elijah Newren
2020-05-10 0:41 ` [RFC PATCH v2 0/4] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-05-10 0:41 ` [RFC PATCH v2 1/4] doc: grep: unify info on configuration variables Matheus Tavares
2020-05-10 0:41 ` [RFC PATCH v2 2/4] config: load the correct config.worktree file Matheus Tavares
2020-05-11 19:10 ` Junio C Hamano
2020-05-12 22:55 ` Matheus Tavares Bernardino
2020-05-12 23:22 ` Junio C Hamano
2020-05-10 0:41 ` [RFC PATCH v2 3/4] grep: honor sparse checkout patterns Matheus Tavares
2020-05-11 19:35 ` Junio C Hamano
2020-05-13 0:05 ` Matheus Tavares Bernardino
2020-05-13 0:17 ` Junio C Hamano
2020-05-21 7:26 ` Elijah Newren
2020-05-21 17:35 ` Matheus Tavares Bernardino
2020-05-21 17:52 ` Elijah Newren
2020-05-22 5:49 ` Matheus Tavares Bernardino
2020-05-22 14:26 ` Elijah Newren
2020-05-22 15:36 ` Elijah Newren
2020-05-22 20:54 ` Matheus Tavares Bernardino
2020-05-22 21:06 ` Elijah Newren
2020-06-10 11:40 ` Derrick Stolee
2020-06-10 16:22 ` Matheus Tavares Bernardino
2020-06-10 17:42 ` Derrick Stolee
2020-06-10 18:14 ` Matheus Tavares Bernardino
2020-06-10 20:12 ` Elijah Newren
2020-06-10 19:58 ` Elijah Newren
2020-05-21 7:36 ` Elijah Newren
2020-05-10 0:41 ` [RFC PATCH v2 4/4] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-05-10 4:23 ` Matheus Tavares Bernardino
2020-05-21 17:18 ` Elijah Newren
2020-05-21 7:09 ` Elijah Newren
2020-05-28 1:12 ` [PATCH v3 0/5] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-05-28 1:12 ` [PATCH v3 1/5] doc: grep: unify info on configuration variables Matheus Tavares
2020-05-28 1:13 ` [PATCH v3 2/5] t/helper/test-config: return exit codes consistently Matheus Tavares
2020-05-30 14:29 ` Elijah Newren
2020-06-01 4:36 ` Matheus Tavares Bernardino
2020-05-28 1:13 ` [PATCH v3 3/5] config: correctly read worktree configs in submodules Matheus Tavares
2020-05-30 14:49 ` Elijah Newren
2020-06-01 4:38 ` Matheus Tavares Bernardino
2020-05-28 1:13 ` [PATCH v3 4/5] grep: honor sparse checkout patterns Matheus Tavares
2020-05-30 15:48 ` Elijah Newren
2020-06-01 4:44 ` Matheus Tavares Bernardino
2020-06-03 2:38 ` Elijah Newren
2020-06-10 17:08 ` Matheus Tavares Bernardino
2020-05-28 1:13 ` [PATCH v3 5/5] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-05-30 16:18 ` Elijah Newren
2020-06-01 4:45 ` Matheus Tavares Bernardino
2020-06-03 2:39 ` Elijah Newren
2020-06-10 21:15 ` Matheus Tavares Bernardino
2020-06-11 0:35 ` Elijah Newren
2020-06-12 15:44 ` [PATCH v4 0/6] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-06-12 15:44 ` [PATCH v4 1/6] doc: grep: unify info on configuration variables Matheus Tavares
2020-06-12 15:45 ` [PATCH v4 2/6] t/helper/test-config: return exit codes consistently Matheus Tavares
2020-06-12 15:45 ` [PATCH v4 3/6] t/helper/test-config: facilitate addition of new cli options Matheus Tavares
2020-06-12 15:45 ` [PATCH v4 4/6] config: correctly read worktree configs in submodules Matheus Tavares
2020-06-16 19:13 ` Elijah Newren
2020-06-21 16:05 ` Matheus Tavares Bernardino
2020-09-01 2:41 ` Jonathan Nieder
2020-09-01 21:44 ` Matheus Tavares Bernardino
2020-06-12 15:45 ` [PATCH v4 5/6] grep: honor sparse checkout patterns Matheus Tavares
2020-06-12 15:45 ` [PATCH v4 6/6] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-06-16 22:31 ` [PATCH v4 0/6] grep: honor sparse checkout and add option to ignore it Elijah Newren
2020-09-02 6:17 ` [PATCH v5 0/8] " Matheus Tavares
2020-09-02 6:17 ` [PATCH v5 1/8] doc: grep: unify info on configuration variables Matheus Tavares
2020-09-02 6:17 ` [PATCH v5 2/8] t1308-config-set: avoid false positives when using test-config Matheus Tavares
2020-09-02 6:57 ` Eric Sunshine
2020-09-02 16:16 ` Matheus Tavares Bernardino
2020-09-02 16:38 ` Eric Sunshine
2020-09-02 6:17 ` [PATCH v5 3/8] t/helper/test-config: be consistent with exit codes Matheus Tavares
2020-09-02 6:17 ` [PATCH v5 4/8] t/helper/test-config: check argc before accessing argv Matheus Tavares
2020-09-02 7:18 ` Eric Sunshine
2020-09-02 6:17 ` [PATCH v5 5/8] t/helper/test-config: unify exit labels Matheus Tavares
2020-09-02 7:30 ` Eric Sunshine
2020-09-02 6:17 ` [PATCH v5 6/8] config: correctly read worktree configs in submodules Matheus Tavares
2020-09-02 20:15 ` Jonathan Nieder
2020-09-09 13:04 ` Matheus Tavares Bernardino
2020-09-09 23:32 ` Jonathan Nieder
2020-09-02 6:17 ` [PATCH v5 7/8] grep: honor sparse checkout patterns Matheus Tavares
2020-09-02 6:17 ` [PATCH v5 8/8] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 0/9] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 1/9] doc: grep: unify info on configuration variables Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 2/9] t1308-config-set: avoid false positives when using test-config Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 3/9] t/helper/test-config: be consistent with exit codes Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 4/9] t/helper/test-config: diagnose missing arguments Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 5/9] t/helper/test-config: unify exit labels Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 6/9] config: make do_git_config_sequence receive a 'struct repository' Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 7/9] config: correctly read worktree configs in submodules Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 8/9] grep: honor sparse checkout patterns Matheus Tavares
2020-09-10 17:21 ` [PATCH v6 9/9] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2021-02-09 21:33 ` [PATCH v7] grep: honor sparse-checkout on working tree searches Matheus Tavares
2021-02-09 23:23 ` Junio C Hamano
2021-02-10 6:12 ` Elijah Newren
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