envbench.go

package main

import (
	"fmt"
	"os"
	"os/exec"
	"sort"
	"strings"
	"time"
)

const (
	iterations = 500
	trials     = 5
)

func bench(label string, size int, shell bool) {
	var env []string
	env = append(env, os.Environ()...)
	if size > 0 {
		env = append(env, "FZF_CURRENT_ITEM="+strings.Repeat("x", size))
	}

	// Warmup
	for i := 0; i < 20; i++ {
		c := makeCmd(shell)
		c.Env = env
		_ = c.Run()
	}

	medians := make([]float64, 0, trials)
	for t := 0; t < trials; t++ {
		start := time.Now()
		for i := 0; i < iterations; i++ {
			c := makeCmd(shell)
			c.Env = env
			if err := c.Run(); err != nil {
				fmt.Fprintln(os.Stderr, "err:", err)
				return
			}
		}
		elapsed := time.Since(start)
		perCall := float64(elapsed.Microseconds()) / float64(iterations) / 1000.0 // ms
		medians = append(medians, perCall)
	}
	sort.Float64s(medians)
	median := medians[len(medians)/2]
	min := medians[0]
	max := medians[len(medians)-1]

	mode := "direct"
	if shell {
		mode = "sh -c"
	}
	fmt.Printf("%-10s  %-8s  env=%7d B  per-call median=%6.3f ms  min=%6.3f  max=%6.3f\n",
		label, mode, size, median, min, max)
}

func makeCmd(shell bool) *exec.Cmd {
	if shell {
		return exec.Command("sh", "-c", "true")
	}
	return exec.Command("/usr/bin/true")
}

func main() {
	fmt.Printf("iterations per trial: %d, trials: %d\n\n", iterations, trials)

	sizes := []struct {
		label string
		size  int
	}{
		{"baseline", 0},
		{"100B", 100},
		{"1KB", 1024},
		{"10KB", 10 * 1024},
		{"100KB", 100 * 1024},
		{"500KB", 500 * 1024},
	}

	fmt.Println("=== direct exec (/usr/bin/true) ===")
	for _, s := range sizes {
		bench(s.label, s.size, false)
	}

	fmt.Println("\n=== via shell (sh -c true) ===")
	for _, s := range sizes {
		bench(s.label, s.size, true)
	}
}