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From: Derrick Stolee <stolee@gmail.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: "Git List" <git@vger.kernel.org>,
	"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Jeff King" <peff@peff.net>, "Stefan Beller" <sbeller@google.com>
Subject: Re: [RFC PATCH] We should add a "git gc --auto" after "git clone" due to commit graph
Date: Fri, 5 Oct 2018 08:05:55 -0400
Message-ID: <dcb8f115-ce3c-64fa-50cc-dd03569c0164@gmail.com> (raw)
In-Reply-To: <87in2hgzin.fsf@evledraar.gmail.com>

On 10/4/2018 5:42 PM, Ævar Arnfjörð Bjarmason wrote:
> I don't have time to polish this up for submission now, but here's a WIP
> patch that implements this, highlights:
>
>   * There's a gc.clone.autoDetach=false default setting which overrides
>     gc.autoDetach if 'git gc --auto' is run via git-clone (we just pass a
>     --cloning option to indicate this).

I'll repeat that it could make sense to do the same thing on clone _and_ 
fetch. Perhaps a "--post-fetch" flag would be good here to communicate 
that we just downloaded a pack from a remote.

>   * A clone of say git.git with gc.writeCommitGraph=true looks like:
>
>     [...]
>     Receiving objects: 100% (255262/255262), 100.49 MiB | 17.78 MiB/s, done.
>     Resolving deltas: 100% (188947/188947), done.
>     Computing commit graph generation numbers: 100% (55210/55210), done.

This looks like good UX. Thanks for the progress here!

>   * The 'git gc --auto' command also knows to (only) run the commit-graph
>     (and space is left for future optimization steps) if general GC isn't
>     needed, but we need "optimization":
>
>     $ rm .git/objects/info/commit-graph; ~/g/git/git --exec-path=$PWD -c gc.writeCommitGraph=true -c gc.autoDetach=false gc --auto;
>     Annotating commits in commit graph: 341229, done.
>     Computing commit graph generation numbers: 100% (165969/165969), done.
>     $

Will this also trigger a full commit-graph rewrite on every 'git commit' 
command? Or is there some way we can compute the staleness of the 
commit-graph in order to only update if we get too far ahead? 
Previously, this was solved by relying on the auto-GC threshold.

>   * The patch to gc.c looks less scary with -w, most of it is indenting
>     the existing pack-refs etc. with a "!auto_gc || should_gc" condition.
>
>   * I added a commit_graph_exists() exists function and only care if I
>     get ENOENT for the purposes of this gc mode. This would need to be
>     tweaked for the incremental mode Derrick talks about, but if we just
>     set "should_optimize" that'll also work as far as gc --auto is
>     concerned (e.g. on fetch, am etc.)

The incremental mode would operate the same as split-index, which means 
we will still look for .git/objects/info/commit-graph. That file may 
point us to more files.

> +int commit_graph_exists(const char *graph_file)
> +{
> +	struct stat st;
> +	if (stat(graph_file, &st)) {
> +		if (errno == ENOENT)
> +			return 0;
> +		else
> +			return -1;
> +	}
> +	return 1;
> +}
> +

This method serves a very similar purpose to 
generation_numbers_enabled(), except your method only cares about the 
file existing. It ignores information like `core.commitGraph`, which 
should keep us from doing anything with the commit-graph file if false.

Nothing about your method is specific to the commit-graph file, since 
you provide a filename as a parameter. It could easily be "int 
file_exists(const char *filename)".

Thanks,

-Stolee



  reply index

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-03 13:23 Ævar Arnfjörð Bjarmason
2018-10-03 13:36 ` SZEDER Gábor
2018-10-03 13:42   ` Derrick Stolee
2018-10-03 14:18     ` Ævar Arnfjörð Bjarmason
2018-10-03 14:01   ` Ævar Arnfjörð Bjarmason
2018-10-03 14:17     ` SZEDER Gábor
2018-10-03 14:22       ` Ævar Arnfjörð Bjarmason
2018-10-03 14:53         ` SZEDER Gábor
2018-10-03 15:19           ` Ævar Arnfjörð Bjarmason
2018-10-03 16:59             ` SZEDER Gábor
2018-10-05  6:09               ` Junio C Hamano
2018-10-10 22:07                 ` SZEDER Gábor
2018-10-10 23:01                   ` Ævar Arnfjörð Bjarmason
2018-10-03 19:08           ` Stefan Beller
2018-10-03 19:21             ` Jeff King
2018-10-03 20:35               ` Ævar Arnfjörð Bjarmason
2018-10-03 17:47         ` Stefan Beller
2018-10-03 18:47           ` Ævar Arnfjörð Bjarmason
2018-10-03 18:51             ` Jeff King
2018-10-03 18:59               ` Derrick Stolee
2018-10-03 19:18                 ` Jeff King
2018-10-08 16:41                   ` SZEDER Gábor
2018-10-08 16:57                     ` Derrick Stolee
2018-10-08 18:10                       ` SZEDER Gábor
2018-10-08 18:29                         ` Derrick Stolee
2018-10-09  3:08                           ` Jeff King
2018-10-09 13:48                             ` Bloom Filters (was Re: We should add a "git gc --auto" after "git clone" due to commit graph) Derrick Stolee
2018-10-09 18:45                               ` Ævar Arnfjörð Bjarmason
2018-10-09 18:46                               ` Jeff King
2018-10-09 19:03                                 ` Derrick Stolee
2018-10-09 21:14                                   ` Jeff King
2018-10-09 23:12                                     ` Bloom Filters Jeff King
2018-10-09 23:13                                       ` [PoC -- do not apply 1/3] initial tree-bitmap proof of concept Jeff King
2018-10-09 23:14                                       ` [PoC -- do not apply 2/3] test-tree-bitmap: add "dump" mode Jeff King
2018-10-10  0:48                                         ` Junio C Hamano
2018-10-11  3:13                                           ` Jeff King
2018-10-09 23:14                                       ` [PoC -- do not apply 3/3] test-tree-bitmap: replace ewah with custom rle encoding Jeff King
2018-10-10  0:58                                         ` Junio C Hamano
2018-10-11  3:20                                           ` Jeff King
2018-10-11 12:33                                       ` Bloom Filters Derrick Stolee
2018-10-11 13:43                                         ` Jeff King
2018-10-09 21:30                             ` We should add a "git gc --auto" after "git clone" due to commit graph SZEDER Gábor
2018-10-09 19:34                       ` [PATCH 0/4] Bloom filter experiment SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 1/4] Add a (very) barebones Bloom filter implementation SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 2/4] commit-graph: write a Bloom filter containing changed paths for each commit SZEDER Gábor
2018-10-09 21:06                           ` Jeff King
2018-10-09 21:37                             ` SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 3/4] revision.c: use the Bloom filter to speed up path-limited revision walks SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 4/4] revision.c: add GIT_TRACE_BLOOM_FILTER for a bit of statistics SZEDER Gábor
2018-10-09 19:47                         ` [PATCH 0/4] Bloom filter experiment Derrick Stolee
2018-10-11  1:21                         ` [PATCH 0/2] Per-commit filter proof of concept Jonathan Tan
2018-10-11  1:21                           ` [PATCH 1/2] One filter per commit Jonathan Tan
2018-10-11  1:21                           ` [PATCH 2/2] Only make bloom filter for first parent Jonathan Tan
2018-10-11  7:37                           ` [PATCH 0/2] Per-commit filter proof of concept Ævar Arnfjörð Bjarmason
2018-10-15 14:39                         ` [PATCH 0/4] Bloom filter experiment Derrick Stolee
2018-10-16  4:45                           ` Junio C Hamano
2018-10-16 11:13                             ` Derrick Stolee
2018-10-16 12:57                               ` Ævar Arnfjörð Bjarmason
2018-10-16 13:03                                 ` Derrick Stolee
2018-10-18  2:00                                 ` Junio C Hamano
2018-10-16 23:41                           ` Jonathan Tan
2018-10-08 23:02                     ` We should add a "git gc --auto" after "git clone" due to commit graph Junio C Hamano
2018-10-03 14:32     ` Duy Nguyen
2018-10-03 16:45 ` Duy Nguyen
2018-10-04 21:42 ` [RFC PATCH] " Ævar Arnfjörð Bjarmason
2018-10-05 12:05   ` Derrick Stolee [this message]
2018-10-05 13:05     ` Ævar Arnfjörð Bjarmason
2018-10-05 13:45       ` Derrick Stolee
2018-10-05 14:04         ` Ævar Arnfjörð Bjarmason
2018-10-05 19:21         ` Jeff King
2018-10-05 19:41           ` Derrick Stolee
2018-10-05 19:47             ` Jeff King
2018-10-05 20:00               ` Derrick Stolee
2018-10-05 20:02                 ` Jeff King
2018-10-05 20:01               ` Ævar Arnfjörð Bjarmason
2018-10-05 20:09                 ` Jeff King
2018-10-11 12:49 [PATCH 1/2] One filter per commit Derrick Stolee
2018-10-11 19:11 ` [PATCH] Per-commit and per-parent filters for 2 parents Jonathan Tan

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