4 files changed, 104 insertions, 6 deletions
diff --git a/t/perf/README b/t/perf/README
index 8848c1461..49ea4349b 100644
--- a/t/perf/README
+++ b/t/perf/README
@@ -115,8 +115,16 @@ After that you will want to use some of the following:
 
 At least one of the first two is required!
 
-You can use test_expect_success as usual.  For actual performance
-tests, use
+You can use test_expect_success as usual. In both test_expect_success
+and in test_perf, running "git" points to the version that is being
+perf-tested. The $MODERN_GIT variable points to the git wrapper for the
+currently checked-out version (i.e., the one that matches the t/perf
+scripts you are running).  This is useful if your setup uses commands
+that only work with newer versions of git than what you might want to
+test (but obviously your new commands must still create a state that can
+be used by the older version of git you are testing).
+
+For actual performance tests, use
 
 	test_perf 'descriptive string' '
 		command1 &&
diff --git a/t/perf/p4211-line-log.sh b/t/perf/p4211-line-log.sh
index 3d074b0e4..b7ff68d4f 100755
--- a/t/perf/p4211-line-log.sh
+++ b/t/perf/p4211-line-log.sh
@@ -23,11 +23,11 @@ test_perf 'git log --follow (baseline for -M)' '
 	git log --oneline --follow -- "$file" >/dev/null
 '
 
-test_perf 'git log -L' '
-	git log -L 1:"$file" >/dev/null
+test_perf 'git log -L (renames off)' '
+	git log --no-renames -L 1:"$file" >/dev/null
 '
 
-test_perf 'git log -M -L' '
+test_perf 'git log -L (renames on)' '
 	git log -M -L 1:"$file" >/dev/null
 '
 
diff --git a/t/perf/p5303-many-packs.sh b/t/perf/p5303-many-packs.sh
new file mode 100755
index 000000000..377985194
--- /dev/null
+++ b/t/perf/p5303-many-packs.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+
+test_description='performance with large numbers of packs'
+. ./perf-lib.sh
+
+test_perf_large_repo
+
+# A real many-pack situation would probably come from having a lot of pushes
+# over time. We don't know how big each push would be, but we can fake it by
+# just walking the first-parent chain and having every 5 commits be their own
+# "push". This isn't _entirely_ accurate, as real pushes would have some
+# duplicate objects due to thin-pack fixing, but it's a reasonable
+# approximation.
+#
+# And then all of the rest of the objects can go in a single packfile that
+# represents the state before any of those pushes (actually, we'll generate
+# that first because in such a setup it would be the oldest pack, and we sort
+# the packs by reverse mtime inside git).
+repack_into_n () {
+	rm -rf staging &&
+	mkdir staging &&
+
+	git rev-list --first-parent HEAD |
+	sed -n '1~5p' |
+	head -n "$1" |
+	perl -e 'print reverse <>' \
+	>pushes
+
+	# create base packfile
+	head -n 1 pushes |
+	git pack-objects --delta-base-offset --revs staging/pack
+
+	# and then incrementals between each pair of commits
+	last= &&
+	while read rev
+	do
+		if test -n "$last"; then
+			{
+				echo "$rev" &&
+				echo "^$last"
+			} |
+			git pack-objects --delta-base-offset --revs \
+				staging/pack || return 1
+		fi
+		last=$rev
+	done <pushes &&
+
+	# and install the whole thing
+	rm -f .git/objects/pack/* &&
+	mv staging/* .git/objects/pack/
+}
+
+# Pretend we just have a single branch and no reflogs, and that everything is
+# in objects/pack; that makes our fake pack-building via repack_into_n()
+# much simpler.
+test_expect_success 'simplify reachability' '
+	tip=$(git rev-parse --verify HEAD) &&
+	git for-each-ref --format="option no-deref%0adelete %(refname)" |
+	git update-ref --stdin &&
+	rm -rf .git/logs &&
+	git update-ref refs/heads/master $tip &&
+	git symbolic-ref HEAD refs/heads/master &&
+	git repack -ad
+'
+
+for nr_packs in 1 50 1000
+do
+	test_expect_success "create $nr_packs-pack scenario" '
+		repack_into_n $nr_packs
+	'
+
+	test_perf "rev-list ($nr_packs)" '
+		git rev-list --objects --all >/dev/null
+	'
+
+	# This simulates the interesting part of the repack, which is the
+	# actual pack generation, without smudging the on-disk setup
+	# between trials.
+	test_perf "repack ($nr_packs)" '
+		git pack-objects --keep-true-parents \
+		  --honor-pack-keep --non-empty --all \
+		  --reflog --indexed-objects --delta-base-offset \
+		  --stdout </dev/null >/dev/null
+	'
+done
+
+test_done
diff --git a/t/perf/perf-lib.sh b/t/perf/perf-lib.sh
index 773f955d4..46f08ee08 100644
--- a/t/perf/perf-lib.sh
+++ b/t/perf/perf-lib.sh
@@ -52,6 +52,9 @@ TEST_NO_MALLOC_CHECK=t
 # need to export them for test_perf subshells
 export TEST_DIRECTORY TRASH_DIRECTORY GIT_BUILD_DIR GIT_TEST_CMP
 
+MODERN_GIT=$GIT_BUILD_DIR/bin-wrappers/git
+export MODERN_GIT
+
 perf_results_dir=$TEST_OUTPUT_DIRECTORY/test-results
 mkdir -p "$perf_results_dir"
 rm -f "$perf_results_dir"/$(basename "$0" .sh).subtests
@@ -81,7 +84,7 @@ test_perf_create_repo_from () {
 	repo="$1"
 	source="$2"
 	source_git="$(git -C "$source" rev-parse --git-dir)"
-	objects_dir="$(git -C "$source" rev-parse --git-path objects)"
+	objects_dir="$("$MODERN_GIT" -C "$source" rev-parse --git-path objects)"
 	mkdir -p "$repo/.git"
 	(
 		cd "$source" &&