From 67bb65de5ddf008cb39206354ae4b7af66c05b6c Mon Sep 17 00:00:00 2001 From: Jeff King Date: Thu, 17 Sep 2020 12:47:43 -0400 Subject: packfile: actually set approximate_object_count_valid The approximate_object_count() function tries to compute the count only once per process. But ever since it was introduced in 8e3f52d778 (find_unique_abbrev: move logic out of get_short_sha1(), 2016-10-03), we failed to actually set the "valid" flag, meaning we'd compute it fresh on every call. This turns out not to be _too_ bad, because we're only iterating through the packed_git list, and not making any system calls. But since it may get called for every abbreviated hash we output, even this can add up if you have many packs. Here are before-and-after timings for a new perf test which just asks rev-list to abbreviate each commit hash (the test repo is linux.git, with commit-graphs): Test origin HEAD ---------------------------------------------------------------------------- 5303.3: rev-list (1) 28.91(28.46+0.44) 29.03(28.65+0.38) +0.4% 5303.4: abbrev-commit (1) 1.18(1.06+0.11) 1.17(1.02+0.14) -0.8% 5303.7: rev-list (50) 28.95(28.56+0.38) 29.50(29.17+0.32) +1.9% 5303.8: abbrev-commit (50) 3.67(3.56+0.10) 3.57(3.42+0.15) -2.7% 5303.11: rev-list (1000) 30.34(29.89+0.43) 30.82(30.35+0.46) +1.6% 5303.12: abbrev-commit (1000) 86.82(86.52+0.29) 77.82(77.59+0.22) -10.4% 5303.15: load 10,000 packs 0.08(0.02+0.05) 0.08(0.02+0.06) +0.0% It doesn't help at all when we have 1 pack (5303.4), but we get a 10% speedup when there are 1000 packs (5303.12). That's a modest speedup for a case that's already slow and we'd hope to avoid in general (note how slow it is even after, because we have to look in each of those packs for abbreviations). But it's a one-line change that clearly matches the original intent, so it seems worth doing. The included perf test may also be useful for keeping an eye on any regressions in the overall abbreviation code. Reported-by: Rasmus Villemoes Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- t/perf/p5303-many-packs.sh | 4 ++++ 1 file changed, 4 insertions(+) (limited to 't/perf') diff --git a/t/perf/p5303-many-packs.sh b/t/perf/p5303-many-packs.sh index 7ee791669a..f4c2ab0584 100755 --- a/t/perf/p5303-many-packs.sh +++ b/t/perf/p5303-many-packs.sh @@ -73,6 +73,10 @@ do git rev-list --objects --all >/dev/null ' + test_perf "abbrev-commit ($nr_packs)" ' + git rev-list --abbrev-commit HEAD >/dev/null + ' + # This simulates the interesting part of the repack, which is the # actual pack generation, without smudging the on-disk setup # between trials. -- cgit v1.2.3