On Mon, Jun 28 2021, Patrick Steinhardt wrote:

From the runtime I think this just needs test_perf_default_repo, no?
I.e. we should only have *_large_* for cases where git.git is too small
to produce meaningful results.

Part of th problem is that git.git has become larger over time...

+test_expect_success 'setup' '
+	# Create a main branch such that we do not have to rely on any specific
+	# branch to exist in the perf repository.
+	git switch --force-create main &&
+
+	# Set up a pre-receive hook such that no refs will ever be changed.
+	# This easily allows multiple perf runs, but still exercises
+	# server-side reference negotiation and checking for consistency.
+	mkdir hooks &&
+	write_script hooks/pre-receive <<-EOF &&
+		#!/bin/sh

You don't need the #!/bin/sh here, and it won't be used. write_script()
adds it (or the wanted shell path).

+		echo "failed in pre-receive hook"
+		exit 1
+	EOF
+	cat >config <<-EOF &&
+		[core]
+			hooksPath=$(pwd)/hooks
+	EOF

Easier understood IMO as:

    git config -f config core.hooksPath ...

+	GIT_CONFIG_GLOBAL="$(pwd)/config" &&
+	export GIT_CONFIG_GLOBAL &&
+
+	git switch --create updated &&
+	test_commit --no-tag updated
+'
+
+setup_empty() {
+	git init --bare "$2"
+}

I searched ahead for setup_empty, looked unused, but...

+setup_clone() {
+	git clone --bare --no-local --branch main "$1" "$2"
+}
+
+setup_clone_bitmap() {
+	git clone --bare --no-local --branch main "$1" "$2" &&
+	git -C "$2" repack -Adb
+}
+
+# Create a reference for each commit in the target repository with extra-refs.
+# While this may be an atypical setup, biggish repositories easily end up with
+# hundreds of thousands of refs, and this is a good enough approximation.
+setup_extrarefs() {
+	git clone --bare --no-local --branch main "$1" "$2" &&
+	git -C "$2" log --all --format="tformat:create refs/commit/%h %H" |
+		git -C "$2" update-ref --stdin
+}
+
+# Create a reference for each commit in the target repository with extra-refs.
+# While this may be an atypical setup, biggish repositories easily end up with
+# hundreds of thousands of refs, and this is a good enough approximation.
+setup_extrarefs_bitmap() {
+	git clone --bare --no-local --branch main "$1" "$2" &&
+	git -C "$2" log --all --format="tformat:create refs/commit/%h %H" |
+		git -C "$2" update-ref --stdin &&
+	git -C "$2" repack -Adb
+}
+
+for repo in empty clone clone_bitmap extrarefs extrarefs_bitmap
+do
+	test_expect_success "$repo setup" '

+		rm -rf target.git &&
+		setup_$repo "$(pwd)" target.git

...here we use it via interpolation.

I'd find this whole pattern much easier to understand if the setups were
just a bunch of test_expect_success that created a repo_empty.git,
repo_extrarefs.git etc. Then this loop would be:

    for repo in repo*.git ...

I'd think that would also give you more meaningful perf data, as now the
OS will churn between the clone & the subsequent push tests, better to
do all the setup, then all the different perf tests.

Perhaps there's also a way to re-use this setup across different runs, I
don't know/can't remember if t/perf has a less transient thing than the
normal trash directory to use for that.