This just shows off the improvements done by the last few
patches, and gives us a baseline for noticing regressions in
the future. Here are the results with linux.git as the perf
"large repo":

Test                origin                HEAD
0003.1: log --raw   43.41(40.36+2.69)     33.86(30.96+2.41) -22.0%
0003.2: log -S      313.61(309.74+3.78)   298.75(295.58+3.00) -4.7%

(for a large repo, the "log -S" improvements are greater if
you bump the delta base cache limit, but I think it makes
sense to test the "stock" behavior, since that is what most
people will see).

Signed-off-by: Jeff King <>
I also got good times for "log -S" when measuring git.git (but _not_
when measuring "log --raw", because of its size). So I guess perhaps the
script could measure both. I'm not sure if the perf framework is ready
for using both test_default_repo and test_large_repo, though.

 t/perf/ | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100755 t/perf/

diff --git a/t/perf/ b/t/perf/
new file mode 100755
index 0000000..62369ea
--- /dev/null
+++ b/t/perf/
@@ -0,0 +1,31 @@
+test_description='Test operations that emphasize the delta base cache.
+We look at both "log --raw", which should put only trees into the delta cache,
+and "log -Sfoo --raw", which should look at both trees and blobs.
+Any effects will be emphasized if the test repository is fully packed (loose
+objects obviously do not use the delta base cache at all). It is also
+emphasized if the pack has long delta chains (e.g., as produced by "gc
+--aggressive"), though cache is still quite noticeable even with the default
+depth of 50.
+The setting of core.deltaBaseCacheLimit in the source repository is also
+relevant (depending on the size of your test repo), so be sure it is consistent
+between runs.
+. ./
+# puts mostly trees into the delta base cache
+test_perf 'log --raw' '
+       git log --raw >/dev/null
+test_perf 'log -S' '
+       git log --raw -Sfoo >/dev/null
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