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| author |  Jeff King <peff@peff.net> | 2019-07-01 09:18:15 -0400 |
|---|---|---|
| committer |  Junio C Hamano <gitster@pobox.com> | 2019-07-01 10:11:09 -0700 |
| commit | 39b44ba771a315602fd1fdca2e12dfc31ef9c613 (patch) | |
| tree | 7ed94c7254550b396a8e4895aa1d2e8c1499d263 /t/perf | |
| parent | object-store.h: move for_each_alternate_ref() from transport.h (diff) | |
| download | tgif-39b44ba771a315602fd1fdca2e12dfc31ef9c613.tar.xz | |
check_everything_connected: assume alternate ref tips are valid
When we receive a remote ref update to sha1 "X", we want to check that
we have all of the objects needed by "X". We can assume that our
repository is not currently corrupted, and therefore if we have a ref
pointing at "Y", we have all of its objects. So we can stop our
traversal from "X" as soon as we hit "Y".
If we make the same non-corruption assumption about any repositories we
use to store alternates, then we can also use their ref tips to shorten
the traversal.
This is especially useful when cloning with "--reference", as we
otherwise do not have any local refs to check against, and have to
traverse the whole history, even though the other side may have sent us
few or no objects. Here are results for the included perf test (which
shows off more or less the maximal savings, getting one new commit and
sharing the whole history):
Test HEAD^ HEAD
--------------------------------------------------------------------
[on git.git]
5600.3: clone --reference 2.94(2.86+0.08) 0.09(0.08+0.01) -96.9%
[on linux.git]
5600.3: clone --reference 45.74(45.34+0.41) 0.36(0.30+0.08) -99.2%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 't/perf')
| -rwxr-xr-x | t/perf/p5600-clone-reference.sh | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/t/perf/p5600-clone-reference.sh b/t/perf/p5600-clone-reference.sh new file mode 100755 index 0000000000..68fed66347 --- /dev/null +++ b/t/perf/p5600-clone-reference.sh @@ -0,0 +1,27 @@ +#!/bin/sh + +test_description='speed of clone --reference' +. ./perf-lib.sh + +test_perf_default_repo + +test_expect_success 'create shareable repository' ' + git clone --bare . shared.git +' + +test_expect_success 'advance base repository' ' + # Do not use test_commit here; its test_tick will + # use some ancient hard-coded date. The resulting clock + # skew will cause pack-objects to traverse in a very + # sub-optimal order, skewing the results. + echo content >new-file-that-does-not-exist && + git add new-file-that-does-not-exist && + git commit -m "new commit" +' + +test_perf 'clone --reference' ' + rm -rf dst.git && + git clone --no-local --bare --reference shared.git . dst.git +' + +test_done |