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rev-list: allow commit-only bitmap traversals

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Ever since we added reachability bitmap support, we've been able to use
it with rev-list to get the full list of objects, like:

  git rev-list --objects --use-bitmap-index --all

But you can't do so without --objects, since we weren't ready to just
show the commits. However, the internals of the bitmap code are mostly
ready for this: they avoid opening up trees when walking to fill in the
bitmaps. We just need to actually pass in the rev_info to
traverse_bitmap_commit_list() so it knows which types to bother
triggering our callback for.

For completeness, the perf test now covers both the existing --objects
case, as well as the new commits-only behavior (the objects one got way
faster when we introduced bitmaps, but obviously isn't improved now).

Here are numbers for linux.git:

  Test                         HEAD^               HEAD
  ------------------------------------------------------------------------
  5310.7: rev-list (commits)   8.29(8.10+0.19)       1.76(1.72+0.04) -78.8%
  5310.8: rev-list (objects)   8.06(7.94+0.12)       8.14(7.94+0.13) +1.0%

That run was cheating a little, as I didn't have any commit-graph in the
repository, and we'd built it by default these days when running git-gc.
Here are numbers with a commit-graph:

  Test                         HEAD^               HEAD
  ------------------------------------------------------------------------
  5310.7: rev-list (commits)   0.70(0.58+0.12)     0.51(0.46+0.04) -27.1%
  5310.8: rev-list (objects)   6.20(6.09+0.10)     6.27(6.16+0.11) +1.1%

Still an improvement, but a lot less impressive.

We could have the perf script remove any commit-graph to show the
out-sized effect, but it probably makes sense to leave it in what would
be a more typical setup.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2020-02-14 13:22:27 -05:00
committed by Junio C Hamano
parent ea047a8eb4
commit 4eb707ebd6
7 changed files with 33 additions and 14 deletions
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9
builtin/rev-list.c
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@ -434,18 +434,11 @@ static int try_bitmap_traversal(struct rev_info *revs)
if (revs->max_count >= 0)
return -1;
/*
* Our bitmap result will return all objects, and we're not
* yet prepared to show only particular types.
*/
if (!revs->tag_objects || !revs->tree_objects || !revs->blob_objects)
return -1;
bitmap_git = prepare_bitmap_walk(revs);
if (!bitmap_git)
return -1;
traverse_bitmap_commit_list(bitmap_git, &show_object_fast);
traverse_bitmap_commit_list(bitmap_git, revs, &show_object_fast);
free_bitmap_index(bitmap_git);
return 0;
}