diff --git a/t/perf/p5303-many-packs.sh b/t/perf/p5303-many-packs.sh
index d90d714923..35c0cbdf49 100755
--- a/t/perf/p5303-many-packs.sh
+++ b/t/perf/p5303-many-packs.sh
@@ -31,8 +31,15 @@ repack_into_n () {
 	' "$1" >pushes &&
 
 	# create base packfile
-	head -n 1 pushes |
-	git pack-objects --delta-base-offset --revs staging/pack &&
+	base_pack=$(
+		head -n 1 pushes |
+		git pack-objects --delta-base-offset --revs staging/pack
+	) &&
+	test_export base_pack &&
+
+	# create an empty packfile
+	empty_pack=$(git pack-objects staging/pack </dev/null) &&
+	test_export empty_pack &&
 
 	# and then incrementals between each pair of commits
 	last= &&
@@ -49,6 +56,12 @@ repack_into_n () {
 		last=$rev
 	done <pushes &&
 
+	(
+		find staging -type f -name 'pack-*.pack' |
+			xargs -n 1 basename | grep -v "$base_pack" &&
+		printf "^pack-%s.pack\n" $base_pack
+	) >stdin.packs
+
 	# and install the whole thing
 	rm -f .git/objects/pack/* &&
 	mv staging/* .git/objects/pack/
@@ -91,6 +104,23 @@ do
 		  --reflog --indexed-objects --delta-base-offset \
 		  --stdout </dev/null >/dev/null
 	'
+
+	test_perf "repack with kept ($nr_packs)" '
+		git pack-objects --keep-true-parents \
+		  --keep-pack=pack-$empty_pack.pack \
+		  --honor-pack-keep --non-empty --all \
+		  --reflog --indexed-objects --delta-base-offset \
+		  --stdout </dev/null >/dev/null
+	'
+
+	test_perf "repack with --stdin-packs ($nr_packs)" '
+		git pack-objects \
+		  --keep-true-parents \
+		  --stdin-packs \
+		  --non-empty \
+		  --delta-base-offset \
+		  --stdout <stdin.packs >/dev/null
+	'
 done
 
 # Measure pack loading with 10,000 packs.