[PATCH 7/7] t/perf: add basic perf tests for delta base cache

From: Jeff King <peff@peff.net>
Date: Aug 22, 2016, 22:01 UTC
Message-ID: <20160822220109.567ez5kslxggcb7a@sigill.intra.peff.net>
In-Reply-To: <20160822215725.qdikfcaz3smhulau@sigill.intra.peff.net>

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 <peff@peff.net>
---
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/p0003-delta-base-cache.sh | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100755 t/perf/p0003-delta-base-cache.sh

diff --git a/t/perf/p0003-delta-base-cache.sh b/t/perf/p0003-delta-base-cache.sh
new file mode 100755
index 0000000..62369ea
--- /dev/null
+++ b/t/perf/p0003-delta-base-cache.sh
@@ -0,0 +1,31 @@
+#!/bin/sh
+
+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.
+'
+. ./perf-lib.sh
+
+test_perf_large_repo
+
+# 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
+'
+
+test_done

-- 
2.10.0.rc1.118.ge2299eb