Implement a straightforward performance test demonstrating the benefit
of pseudo-merge bitmaps by measuring how long it takes to count
reachable objects in a few different scenarios:
- without bitmaps, to demonstrate a reasonable baseline
- with bitmaps, but without pseudo-merges
- with bitmaps and pseudo-merges
Results from running this test on git.git are as follows:
Test this tree
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5333.2: git rev-list --count --all --objects (no bitmaps) 3.54(3.45+0.08)
5333.3: git rev-list --count --all --objects (no pseudo-merges) 0.43(0.40+0.03)
5333.4: git rev-list --count --all --objects (with pseudo-merges) 0.12(0.11+0.01)
On a private repository which is much larger, and has many spikey parts
of history that aren't merged into the 'master' branch, the results are
as follows:
Test this tree
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5333.1: git rev-list --count --all --objects (no bitmaps) 122.29(121.31+0.97)
5333.2: git rev-list --count --all --objects (no pseudo-merges) 21.88(21.30+0.58)
5333.3: git rev-list --count --all --objects (with pseudo-merges) 5.05(4.77+0.28)
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Taylor Blau