From: Kristofer Karlsson <krka@spotify.com>
Date: Sat, 11 Jul 2026 13:27:40 +0000 (+0000)
Subject: commit-reach: add trace2 instrumentation to paint_down_to_common()
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=47183400bf054d29c33266e0dd18d4d8b31a5a17;p=thirdparty%2Fgit.git

commit-reach: add trace2 instrumentation to paint_down_to_common()

Add a step counter and trace2_data_intmax() call so that the number
of commits visited during the paint walk is observable via
GIT_TRACE2_EVENT. This provides a way to measure the impact of
future optimizations without relying on wall-clock benchmarks alone.

Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

diff --git a/commit-reach.c b/commit-reach.c
index bbf8c3eff0..34e588f7c0 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -11,6 +11,7 @@
 #include "tag.h"
 #include "commit-reach.h"
 #include "ewah/ewok.h"
+#include "trace2.h"
 
 /* Remember to update object flag allocation in object.h */
 #define PARENT1		(1u<<16)
@@ -113,6 +114,7 @@ static int paint_down_to_common(struct repository *r,
 	};
 	int i;
 	int gen_ordered = 1;
+	int steps = 0;
 	timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
 	struct commit_list **tail = result;
 
@@ -138,6 +140,7 @@ static int paint_down_to_common(struct repository *r,
 		struct commit_list *parents;
 		int flags;
 		timestamp_t generation = commit_graph_generation(commit);
+		steps++;
 
 		if (min_generation && generation > last_gen)
 			BUG("bad generation skip %"PRItime" > %"PRItime" at %s",
@@ -194,6 +197,8 @@ static int paint_down_to_common(struct repository *r,
 	}
 
 	clear_nonstale_queue(&queue);
+	trace2_data_intmax("paint_down_to_common", r,
+			   "steps", steps);
 	commit_list_sort_by_date(result);
 	return 0;
 }
diff --git a/t/t6600-test-reach.sh b/t/t6600-test-reach.sh
index 27db83eb5a..574777d809 100755
--- a/t/t6600-test-reach.sh
+++ b/t/t6600-test-reach.sh
@@ -153,24 +153,34 @@ test_expect_success 'setup' '
 '
 
 run_all_modes () {
-	test_when_finished rm -rf .git/objects/info/commit-graph &&
-	"$@" <input >actual &&
-	test_cmp expect actual &&
-	cp commit-graph-full .git/objects/info/commit-graph &&
-	"$@" <input >actual &&
-	test_cmp expect actual &&
-	cp commit-graph-half .git/objects/info/commit-graph &&
-	"$@" <input >actual &&
-	test_cmp expect actual &&
-	cp commit-graph-no-gdat .git/objects/info/commit-graph &&
-	"$@" <input >actual &&
-	test_cmp expect actual
+	graph=.git/objects/info/commit-graph &&
+	test_when_finished rm -rf "$graph" "${graph}s" &&
+	rm -f trace-mode-*.txt &&
+
+	for mode in none full half no-gdat
+	do
+		rm -rf "$graph" "${graph}s" &&
+		cp "commit-graph-${mode}" "$graph" 2>/dev/null ||
+		true &&
+		GIT_TRACE2_EVENT="$(pwd)/trace-mode-${mode}.txt" \
+			"$@" <input >actual &&
+		test_cmp expect actual || return 1
+	done
 }
 
 test_all_modes () {
 	run_all_modes test-tool reach "$@"
 }
 
+test_paint_down_steps () {
+	for mode in none full half no-gdat
+	do
+		test_trace2_data_singular paint_down_to_common steps "$1" \
+			"mode=$mode" <"trace-mode-${mode}.txt" || return 1
+		shift
+	done
+}
+
 test_expect_success 'ref_newer:miss' '
 	cat >input <<-\EOF &&
 	A:commit-5-7
@@ -244,7 +254,8 @@ test_expect_success 'in_merge_bases_many:self' '
 	X:commit-6-8
 	EOF
 	echo "in_merge_bases_many(A,X):1" >expect &&
-	test_all_modes in_merge_bases_many
+	test_all_modes in_merge_bases_many &&
+	test_paint_down_steps 45 2 25 3
 '
 
 test_expect_success 'is_descendant_of:hit' '
@@ -329,6 +340,13 @@ test_expect_success 'get_merge_bases_many:infinity-both-sides' '
 	test_all_modes get_merge_bases_many
 '
 
+test_expect_success 'merge-base --all commit-walk steps' '
+	>input &&
+	git rev-parse commit-9-1 >expect &&
+	run_all_modes git merge-base --all commit-9-9 commit-9-1 &&
+	test_paint_down_steps 81 80 81 81
+'
+
 test_expect_success 'reduce_heads' '
 	cat >input <<-\EOF &&
 	X:commit-1-10