readme.md

See: valyala/fasthttp#931 (comment)

sendfile.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"strconv"
	"sync"
	"sync/atomic"
	"time"
)

var (
	useBigFile bool
	fileSize   int

	client = &http.Client{
		Transport: &http.Transport{
			MaxIdleConnsPerHost: 1024,
		},
	}
)

type writerOnly struct {
	io.Writer
}

func serve(w http.ResponseWriter, r *http.Request) {
	f, err := os.Open(fmt.Sprintf("out%d.file", fileSize))
	if err != nil {
		panic(err)
	}

	w.Header().Add("Content-Length", strconv.Itoa(fileSize))

	if useBigFile {
		// http.ResponseWriter implements io.ReadFrom triggering sendfile to be tried.
		if _, err = io.Copy(w, f); err != nil {
			panic(err)
		}
	} else {
		// writerOnly doesn't implement io.ReadFrom so a normal Read/Write loop is used.
		if _, err = io.Copy(writerOnly{w}, f); err != nil {
			panic(err)
		}
	}

	if err := f.Close(); err != nil {
		panic(err)
	}
}

func bench() float64 {
	seconds := 10
	end := time.Now().Add(time.Second * time.Duration(seconds))

	var requests int64
	var wg sync.WaitGroup

	worker := func() {
		for time.Now().Before(end) {
			resp, err := client.Get("http://localhost:8081/")
			if err != nil {
				panic(err)
			}

			if _, err := io.Copy(ioutil.Discard, resp.Body); err != nil {
				panic(err)
			}

			if err := resp.Body.Close(); err != nil {
				panic(err)
			}

			atomic.AddInt64(&requests, 1)
		}
		wg.Done()
	}

	for i := 0; i < 32; i++ {
		wg.Add(1)
		go worker()
	}

	wg.Wait()

	return float64(requests) / float64(seconds)
}

func add(r []int, from, to, inc int) []int {
	for i := from; i <= to; i += inc {
		r = append(r, i)
	}
	return r
}

func size(b int) string {
	const unit = 1000
	div, exp := int64(unit), 0
	for n := b / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f%cb", float64(b)/float64(div), "kmg"[exp])
}

func main() {
	go func() {
		if err := http.ListenAndServe("127.0.0.1:8081", http.HandlerFunc(serve)); err != nil {
			panic(err)
		}
	}()

	time.Sleep(time.Second) // Give the server some time to start.

	fmt.Printf("%10s: %10s vs %10s      %10s\n", "size", "sendfile", "r/w", "sendfile faster")

	sizes := make([]int, 0)

	sizes = add(sizes, 1_000, 10_000, 1_000)   // 1kb - 10kb, 1kb increments
	sizes = add(sizes, 20_000, 60_000, 10_000) // 20kb - 60kb, 10kb increments
	sizes = add(sizes, 65_994, 65_995, 1)
	sizes = add(sizes, 70_000, 100_000, 10_000)                 // 70kb - 100kb, 10kb increments
	sizes = add(sizes, 200_000, 1_200_000, 100_000)             // 200kb - 1.2mb, 100kb increments
	sizes = add(sizes, 1_500_000, 3_000_000, 500_000)           // 1.5mb - 3mb, 500kb increments
	sizes = add(sizes, 100_000_000, 1_000_000_000, 100_000_000) // 100mb - 1gb, 100mb increments

	for _, fileSize = range sizes {
		if err := ioutil.WriteFile(fmt.Sprintf("out%d.file", fileSize), make([]byte, fileSize), 0666); err != nil {
			panic(err)
		}

		time.Sleep(time.Second)

		useBigFile = false
		smallRate := bench()

		time.Sleep(time.Second)

		useBigFile = true
		bigRate := bench()

		fmt.Printf("%10s: %10.2f vs %10.2f diff %10.2f%%\n", size(fileSize), bigRate, smallRate, 100-smallRate/bigRate*100)

		time.Sleep(time.Second)
	}
}