Cost of stating files while walking linux kernel tree 4.7.5

cgowalk.go

package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"runtime/pprof"
)

// #include <dirent.h>
import "C"

type FileInfo struct {
	Name string
	Type uint8
}

func (f FileInfo) IsDirectory() bool {
	return f.Type&C.DT_DIR != 0
}

func (f FileInfo) IsSymbolicLink() bool {
	return f.Type&C.DT_LNK != 0
}

func (f FileInfo) IsRegularFile() bool {
	return f.Type&C.DT_REG != 0
}

type WalkFunc func(path string, info FileInfo)

func Walk(path string, walkFunc WalkFunc) error {
	f, err := os.Open(path)
	if err != nil {
		return err
	}
	dir := C.fdopendir(C.int(f.Fd()))
	for {
		dirent := C.readdir(dir)
		if dirent == nil {
			break
		}
		info := FileInfo{C.GoString((*C.char)(&dirent.d_name[0])), uint8(dirent.d_type)}
		if info.Name == "." || info.Name == ".." {
			continue
		}
		fullPath := path + "/" + info.Name
		walkFunc(fullPath, info)
		if info.IsDirectory() {
			Walk(fullPath, walkFunc)
		}
	}
	f.Close()
	return nil
}

func main() {
	if len(os.Args) != 2 {
		log.Fatal("need one arg")
	}
	f, err := os.Create(os.Args[1] + ".prof")
	if err != nil {
		log.Fatal(err)
	}
	pprof.StartCPUProfile(f)
	defer pprof.StopCPUProfile()
	if os.Args[1] == "cgo" {
		Walk(".", func(name string, info FileInfo) {
			fmt.Println(name)
		})
	} else if os.Args[1] == "pure" {
		filepath.Walk(".", func(name string, info os.FileInfo, err error) error {
			fmt.Println(name)
			return nil
		})
	}
}

profile-cgo.svg

profile-pure.svg