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From: Derrick Stolee <stolee@gmail.com>
To: Taylor Blau <me@ttaylorr.com>, git@vger.kernel.org
Cc: peff@peff.net, dstolee@microsoft.com, gitster@pobox.com
Subject: Re: [PATCH 1/3] builtin/commit-graph.c: support '--split[=<strategy>]'
Date: Fri, 31 Jan 2020 09:19:19 -0500	[thread overview]
Message-ID: <8a648a69-60bd-2b19-facb-1d7821661883@gmail.com> (raw)
In-Reply-To: <4f5bc19903f8a1f5b153b5665de378e743e12744.1580430057.git.me@ttaylorr.com>

On 1/30/2020 7:28 PM, Taylor Blau wrote:
> With '--split', the commit-graph machinery writes new commits in another
> incremental commit-graph which is part of the existing chain, and
> optionally decides to condense the chain into a single commit-graph.
> This is done to ensure that the aysmptotic behavior of looking up a
> commit in an incremental chain is dominated by the number of
> incrementals in that chain. It can be controlled by the '--max-commits'
> and '--size-multiple' options.
> 
> On occasion, callers may want to ensure that 'git commit-graph write
> --split' always writes an incremental, and never spends effort
> condensing the incremental chain [1]. Previously, this was possible by
> passing '--size-multiple=0', but this no longer the case following
> 63020f175f (commit-graph: prefer default size_mult when given zero,
> 2020-01-02).
> 
> Reintroduce a less-magical variant of the above with a new pair of
> arguments to '--split': '--split=no-merge' and '--split=merge-all'. When
> '--split=no-merge' is given, the commit-graph machinery will never
> condense an existing chain and will always write a new incremental.
> Conversely, if '--split=merge-all' is given, any invocation including it
> will always condense a chain if one exists.  If '--split' is given with
> no arguments, it behaves as before and defers to '--size-multiple', and
> so on.
> 
> [1]: This might occur when, for example, a server administrator running
> some program after each push may want to ensure that each job runs
> proportional in time to the size of the push, and does not "jump" when
> the commit-graph machinery decides to trigger a merge.
> 
> Signed-off-by: Taylor Blau <me@ttaylorr.com>
> ---
>  Documentation/git-commit-graph.txt | 18 +++++++++++-----
>  builtin/commit-graph.c             | 33 ++++++++++++++++++++++++++----
>  commit-graph.c                     | 19 +++++++++--------
>  commit-graph.h                     |  7 +++++++
>  t/t5324-split-commit-graph.sh      | 25 ++++++++++++++++++++++
>  5 files changed, 85 insertions(+), 17 deletions(-)
> 
> diff --git a/Documentation/git-commit-graph.txt b/Documentation/git-commit-graph.txt
> index 28d1fee505..8d61ba9f56 100644
> --- a/Documentation/git-commit-graph.txt
> +++ b/Documentation/git-commit-graph.txt
> @@ -57,11 +57,19 @@ or `--stdin-packs`.)
>  With the `--append` option, include all commits that are present in the
>  existing commit-graph file.
>  +
> -With the `--split` option, write the commit-graph as a chain of multiple
> -commit-graph files stored in `<dir>/info/commit-graphs`. The new commits
> -not already in the commit-graph are added in a new "tip" file. This file
> -is merged with the existing file if the following merge conditions are
> -met:
> +With the `--split[=<strategy>]` option, write the commit-graph as a
> +chain of multiple commit-graph files stored in
> +`<dir>/info/commit-graphs`. Commit-graph layers are merged based on the
> +strategy and other splitting options. The new commits not already in the
> +commit-graph are added in a new "tip" file. This file is merged with the
> +existing file if the following merge conditions are met:
> +* If `--split=merge-always` is specified, then a merge is always
> +conducted, and the remaining options are ignored. Conversely, if
> +`--split=no-merge` is specified, a merge is never performed, and the
> +remaining options are ignored. A bare `--split` defers to the remaining
> +options. (Note that merging a chain of commit graphs replaces the
> +existing chain with a length-1 chain where the first and only
> +incremental holds the entire graph).
>  +
>  * If `--size-multiple=<X>` is not specified, let `X` equal 2. If the new
>  tip file would have `N` commits and the previous tip has `M` commits and
> diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
> index de321c71ad..f03b46d627 100644
> --- a/builtin/commit-graph.c
> +++ b/builtin/commit-graph.c
> @@ -9,7 +9,9 @@
>  
>  static char const * const builtin_commit_graph_usage[] = {
>  	N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
> -	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits] [--[no-]progress] <split options>"),
> +	N_("git commit-graph write [--object-dir <objdir>] [--append] "
> +	   "[--split[=<strategy>]] [--reachable|--stdin-packs|--stdin-commits] "
> +	   "[--[no-]progress] <split options>"),
>  	NULL
>  };
>  
> @@ -19,7 +21,9 @@ static const char * const builtin_commit_graph_verify_usage[] = {
>  };
>  
>  static const char * const builtin_commit_graph_write_usage[] = {
> -	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits] [--[no-]progress] <split options>"),
> +	N_("git commit-graph write [--object-dir <objdir>] [--append] "
> +	   "[--split[=<strategy>]] [--reachable|--stdin-packs|--stdin-commits] "
> +	   "[--[no-]progress] <split options>"),
>  	NULL
>  };
>  
> @@ -101,6 +105,25 @@ static int graph_verify(int argc, const char **argv)
>  extern int read_replace_refs;
>  static struct split_commit_graph_opts split_opts;
>  
> +static int write_option_parse_split(const struct option *opt, const char *arg,
> +				    int unset)
> +{
> +	enum commit_graph_split_flags *flags = opt->value;
> +
> +	opts.split = 1;
> +	if (!arg)
> +		return 0;

This allows `--split` to continue working as-is. But should we also
set "*flags = COMMIT_GRAPH_SPLIT_UNSPECIFIED" here? This allows one
to run "git commit-graph write --split=no-merge --split" (which could
happen if "--split=no-merge" is inside an alias).

> +test_expect_success '--split=merge-all always merges incrementals' '
> +	test_when_finished rm -rf a b c &&
> +	rm -rf $graphdir $infodir/commit-graph &&
> +	git reset --hard commits/10 &&
> +	git rev-list -3 HEAD~4 >a &&
> +	git rev-list -2 HEAD~2 >b &&
> +	git rev-list -2 HEAD >c &&
> +	git commit-graph write --split=no-merge --stdin-commits <a &&
> +	git commit-graph write --split=no-merge --stdin-commits <b &&
> +	test_line_count = 2 $graphdir/commit-graph-chain &&
> +	git commit-graph write --split=merge-all --stdin-commits <c &&
> +	test_line_count = 1 $graphdir/commit-graph-chain
> +'
> +
> +test_expect_success '--split=no-merge always writes an incremental' '
> +	test_when_finished rm -rf a b &&
> +	rm -rf $graphdir &&
> +	git reset --hard commits/2 &&
> +	git rev-list HEAD~1 >a &&
> +	git rev-list HEAD >b &&
> +	git commit-graph write --split --stdin-commits <a &&
> +	git commit-graph write --split=no-merge --stdin-commits <b &&
> +	test_line_count = 2 $graphdir/commit-graph-chain
> +'
> +
>  test_done

Good tests!

Thanks,
-Stolee


  reply	other threads:[~2020-01-31 14:19 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-31  0:28 [PATCH 0/3] builtin/commit-graph.c: new split/merge options Taylor Blau
2020-01-31  0:28 ` [PATCH 1/3] builtin/commit-graph.c: support '--split[=<strategy>]' Taylor Blau
2020-01-31 14:19   ` Derrick Stolee [this message]
2020-02-04  3:47     ` Taylor Blau
2020-01-31 19:27   ` Martin Ågren
2020-02-04  4:06     ` Taylor Blau
2020-02-06 19:15       ` Martin Ågren
2020-02-09 23:27         ` Taylor Blau
2020-01-31 23:34   ` SZEDER Gábor
2020-02-01 21:25     ` Johannes Schindelin
2020-02-03 10:47       ` SZEDER Gábor
2020-02-03 11:11         ` Jeff King
2020-02-04  3:58           ` Taylor Blau
2020-02-04 14:14             ` Jeff King
2020-02-04  3:59       ` Taylor Blau
2020-02-04  3:59     ` Taylor Blau
2020-01-31  0:28 ` [PATCH 2/3] builtin/commit-graph.c: introduce '--input=<source>' Taylor Blau
2020-01-31 14:40   ` Derrick Stolee
2020-02-04  4:21     ` Taylor Blau
2020-01-31 19:34   ` Martin Ågren
2020-02-04  4:51     ` Taylor Blau
2020-02-13 11:33       ` SZEDER Gábor
2020-02-13 11:48         ` SZEDER Gábor
2020-02-13 17:56           ` Taylor Blau
2020-01-31  0:28 ` [PATCH 3/3] builtin/commit-graph.c: support '--input=none' Taylor Blau
2020-01-31 14:40   ` Derrick Stolee
2020-01-31 19:45   ` Martin Ågren
2020-02-04  5:01     ` Taylor Blau
2020-01-31  0:32 ` [PATCH 0/3] builtin/commit-graph.c: new split/merge options Taylor Blau
2020-01-31 13:26   ` Derrick Stolee
2020-01-31 14:41 ` Derrick Stolee
2020-02-04 23:44 ` Junio C Hamano
2020-02-05  0:30   ` Taylor Blau
2020-02-05  0:28 ` [PATCH v2 " Taylor Blau
2020-02-05  0:28   ` [PATCH v2 1/3] builtin/commit-graph.c: support '--split[=<strategy>]' Taylor Blau
2020-02-06 19:41     ` Martin Ågren
2020-02-07 15:48       ` Derrick Stolee
2020-02-09 23:32         ` Taylor Blau
2020-02-12  6:03         ` Martin Ågren
2020-02-12 20:50           ` Taylor Blau
2020-02-09 23:30       ` Taylor Blau
2020-02-05  0:28   ` [PATCH v2 2/3] builtin/commit-graph.c: introduce '--input=<source>' Taylor Blau
2020-02-05  0:28   ` [PATCH v2 3/3] builtin/commit-graph.c: support '--input=none' Taylor Blau
2020-02-06 19:50     ` Martin Ågren
2020-02-09 23:32       ` Taylor Blau
2020-02-05 20:07   ` [PATCH v2 0/3] builtin/commit-graph.c: new split/merge options Junio C Hamano
2020-02-12  5:47 ` [PATCH v3 " Taylor Blau
2020-02-12  5:47   ` [PATCH v3 1/3] builtin/commit-graph.c: support '--split[=<strategy>]' Taylor Blau
2020-02-12  5:47   ` [PATCH v3 2/3] builtin/commit-graph.c: introduce '--input=<source>' Taylor Blau
2020-02-12  5:47   ` [PATCH v3 3/3] builtin/commit-graph.c: support '--input=none' Taylor Blau
2020-02-13 11:39     ` SZEDER Gábor
2020-02-13 12:31     ` SZEDER Gábor
2020-02-13 16:08       ` Junio C Hamano
2020-02-13 17:58         ` Taylor Blau
2020-02-13 17:56       ` Taylor Blau
2020-02-12 18:19   ` [PATCH v3 0/3] builtin/commit-graph.c: new split/merge options Junio C Hamano
2020-02-13 17:41     ` Taylor Blau
2020-02-17 18:24   ` Martin Ågren

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