[PATCH v3 4/4] p1500: add is-base performance tests

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 14, 2024, 10:31 UTC
Message-ID: <cce9921bbd8825c3a12d32b2c8b62a2c4b06333a.1723631490.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1768.v3.git.1723631490.gitgitgadget@gmail.com>

From: Derrick Stolee <stolee@gmail.com>

The previous two changes introduced a commit walking heuristic for finding the most likely base branch for a given source. This algorithm walks first-parent histories until reaching a collision.

This walk _should_ be very fast. Exceptions include cases where a commit-graph file does not exist, leading to a full walk of all reachable commits to compute generation numbers, or a case where no collision in the first-parent history exists, leading to a walk of all first-parent history to the root commits.

The p1500 test script guarantees a complete commit-graph file during its setup, so we will not test that scenario. Do create a new root commit in an effort to test the scenario of parallel first-parent histories.

Even with the extra root commit, these tests take no longer than 0.02 seconds on my machine for the Git repository. However, the results are slightly more interesting in a copy of the Linux kernel repository:

Test --------------------------------------------------------------- 1500.2: ahead-behind counts: git for-each-ref 0.12 1500.3: ahead-behind counts: git branch 0.12 1500.4: ahead-behind counts: git tag 0.12 1500.5: contains: git for-each-ref --merged 0.04 1500.6: contains: git branch --merged 0.04 1500.7: contains: git tag --merged 0.04 1500.8: is-base check: test-tool reach (refs) 0.03 1500.9: is-base check: test-tool reach (tags) 0.03 1500.10: is-base check: git for-each-ref 0.03 1500.11: is-base check: git for-each-ref (disjoint-base) 0.07

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 t/perf/p1500-graph-walks.sh | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/t/perf/p1500-graph-walks.sh b/t/perf/p1500-graph-walks.sh
index e14e7620cce..5b23ce5db93 100755
--- a/t/perf/p1500-graph-walks.sh
+++ b/t/perf/p1500-graph-walks.sh
@@ -20,6 +20,21 @@ test_expect_success 'setup' '
 		echo tag-$ref ||
 		return 1
 	done >tags &&
+
+	echo "A:HEAD" >test-tool-refs &&
+	for line in $(cat refs)
+	do
+		echo "X:$line" >>test-tool-refs || return 1
+	done &&
+	echo "A:HEAD" >test-tool-tags &&
+	for line in $(cat tags)
+	do
+		echo "X:$line" >>test-tool-tags || return 1
+	done &&
+
+	commit=$(git commit-tree $(git rev-parse HEAD^{tree})) &&
+	git update-ref refs/heads/disjoint-base $commit &&
+
 	git commit-graph write --reachable
 '
 
@@ -47,4 +62,20 @@ test_perf 'contains: git tag --merged' '
 	xargs git tag --merged=HEAD <tags
 '
 
+test_perf 'is-base check: test-tool reach (refs)' '
+	test-tool reach get_branch_base_for_tip <test-tool-refs
+'
+
+test_perf 'is-base check: test-tool reach (tags)' '
+	test-tool reach get_branch_base_for_tip <test-tool-tags
+'
+
+test_perf 'is-base check: git for-each-ref' '
+	git for-each-ref --format="%(is-base:HEAD)" --stdin <refs
+'
+
+test_perf 'is-base check: git for-each-ref (disjoint-base)' '
+	git for-each-ref --format="%(is-base:refs/heads/disjoint-base)" --stdin <refs
+'
+
 test_done

-- 
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