"Garima Singh via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes:
> From: Garima Singh <garima.singh@xxxxxxxxxxxxx>
>
> Add --changed-paths option to git commit-graph write. This option will
> allow users to compute information about the paths that have changed
> between a commit and its first parent, and write it into the commit graph
> file. If the option is passed to the write subcommand we set the
> COMMIT_GRAPH_WRITE_BLOOM_FILTERS flag and pass it down to the
> commit-graph logic.
In the manpage you write that this operation (computing Bloom filters)
can take a while on large repositories. Could you perhaps provide some
numbers: how much longer does it take to write commit-graph file with
and without '--changed-paths' for example for Linux kernel, or some
other large repository? Thanks in advance.
>
> Helped-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
> Signed-off-by: Garima Singh <garima.singh@xxxxxxxxxxxxx>
> ---
> Documentation/git-commit-graph.txt | 5 +++++
> builtin/commit-graph.c | 9 +++++++--
> 2 files changed, 12 insertions(+), 2 deletions(-)
What is missing is some sanity tests: that bloom index and bloom data
chunks are not present without '--changed-paths', and that they are
added with '--changed-paths'.
If possible, maybe also check in a separate test that the size of
bloom_index chunk agrees with the number of commits in the commit graph.
Also, we can now add those tests I have wrote about in my review of
previous patch, that is:
1. If you write commit-graph with --changed-paths, and either add some
commits later or exclude some commits from the commit graph, then:
a.) commit(s) in commit-graph have Bloom filter
b.) commit(s) not in commit-graph do not have Bloom filter
2. If you write commit-graph without --changed-paths as base layer,
and then write next layer with --changed-paths and --split, then:
a.) commit(s) in top layer have Bloom filter(s)
b.) commit(s) in bottom layer don't have Bloom filter(s)
>
> diff --git a/Documentation/git-commit-graph.txt b/Documentation/git-commit-graph.txt
> index bcd85c1976..907d703b30 100644
> --- a/Documentation/git-commit-graph.txt
> +++ b/Documentation/git-commit-graph.txt
> @@ -54,6 +54,11 @@ or `--stdin-packs`.)
> With the `--append` option, include all commits that are present in the
> existing commit-graph file.
> +
> +With the `--changed-paths` option, compute and write information about the
> +paths changed between a commit and it's first parent. This operation can
> +take a while on large repositories. It provides significant performance gains
> +for getting history of a directory or a file with `git log -- <path>`.
> ++
Should we write about limitation that the topmost layer in the split
commit graph needs to be written with '--changed-paths' for Git to use
this information? Or perhaps we should try (in the future) to remove
this limitation??
> 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
> diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
> index e0c6fc4bbf..261dcce091 100644
> --- a/builtin/commit-graph.c
> +++ b/builtin/commit-graph.c
> @@ -9,7 +9,7 @@
>
> 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] [--reachable|--stdin-packs|--stdin-commits] [--changed-paths] [--[no-]progress] <split options>"),
> NULL
> };
>
> @@ -19,7 +19,7 @@ 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] [--reachable|--stdin-packs|--stdin-commits] [--changed-paths] [--[no-]progress] <split options>"),
> NULL
> };
>
All right.
> @@ -32,6 +32,7 @@ static struct opts_commit_graph {
> int split;
> int shallow;
> int progress;
> + int enable_changed_paths;
Bikeshed painting: should this field be called enable_changed_paths or
simply changed_paths?
> } opts;
>
> static int graph_verify(int argc, const char **argv)
> @@ -110,6 +111,8 @@ static int graph_write(int argc, const char **argv)
> N_("start walk at commits listed by stdin")),
> OPT_BOOL(0, "append", &opts.append,
> N_("include all commits already in the commit-graph file")),
> + OPT_BOOL(0, "changed-paths", &opts.enable_changed_paths,
> + N_("enable computation for changed paths")),
> OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
> OPT_BOOL(0, "split", &opts.split,
> N_("allow writing an incremental commit-graph file")),
All right.
> @@ -143,6 +146,8 @@ static int graph_write(int argc, const char **argv)
> flags |= COMMIT_GRAPH_WRITE_SPLIT;
> if (opts.progress)
> flags |= COMMIT_GRAPH_WRITE_PROGRESS;
> + if (opts.enable_changed_paths)
> + flags |= COMMIT_GRAPH_WRITE_BLOOM_FILTERS;
>
> read_replace_refs = 0;
All right. This actually turns on calculation Bloom filters for changed
paths, thanks to
ctx->changed_paths = flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS ? 1 : 0;
that was added by the "[PATCH v2 04/11] commit-graph: compute Bloom
filters for changed paths" patch.
Though... should this enabling be split into two separate patches like
this?
Best,
--
Jakub Narębski
