fsync benchmark

fsync-bench.go

package main

import (
	"flag"
	"io"
	"os"
)

const blockSize = 70 << 10

func write(dstFD *os.File, sync bool, limitBytes uint64) {
	srcFD, err := os.Open("/dev/zero")
	if err != nil {
		panic(err)
	}
	defer srcFD.Close()
	var count uint64
	for {
		_, err := io.CopyN(dstFD, srcFD, blockSize)
		if err != nil {
			panic(err)
		}
		if sync {
			err := dstFD.Sync()
			if err != nil {
				panic(err)
			}
		}

		count += blockSize
		if count > limitBytes {
			break
		}
	}

	dstFD.Sync()
}

var output string
var limit uint64
var sync bool

func init() {
	flag.StringVar(&output, "output", "", "output file")
	flag.Uint64Var(&limit, "limit-bytes", 0, "write this number of bytes")
	flag.BoolVar(&sync, "sync", true, "sync to disk after each block")
}

func main() {
	flag.Parse()

	fd, err := os.Create(output)
	if err != nil {
		panic(err)
	}
	defer fd.Close()

	write(fd, sync, limit)
}