}()

	// Run the benchmark for at least the specified amount of time.
	if b.benchTime.n > 0 {
		// We already ran a single iteration in run1.
		// If -benchtime=1x was requested, use that result.
		// See https://golang.org/issue/32051.
		if b.benchTime.n > 1 {
			b.runN(b.benchTime.n)
		}
	} else {
		d := b.benchTime.d
		for n := int64(1); !b.failed && b.duration < d && n < 1e9; {
			last := n

	exe, err := os.Executable()
	if err != nil {
		t.Skipf("can't find test executable: %v", err)
	}

	cmd := testenv.Command(t, exe, "-test.run=^"+test+"$", "-test.bench="+test, "-test.v", "-test.parallel=2", "-test.benchtime=2x")
	cmd = testenv.CleanCmdEnv(cmd)
	cmd.Env = append(cmd.Env, "GO_WANT_HELPER_PROCESS=1")
	out, err := cmd.CombinedOutput()
	t.Logf("%v: %v\n%s", cmd, err, out)

	return out
}