为什么我的 Go 文件浏览程序运行缓慢？

偷偷努力，悄无声息地变强，然后惊艳所有人！哈哈，小伙伴们又来学习啦~今天我将给大家介绍《为什么我的 Go 文件浏览程序运行缓慢？》，这篇文章主要会讲到等等知识点，不知道大家对其都有多少了解，下面我们就一起来看一吧！当然，非常希望大家能多多评论，给出合理的建议，我们一起学习，一起进步！

为什么这个程序这么慢？我认为代码已经相当优化，但在我的根文件系统上使用时，它比 find 命令花费的时间要长得多。

大约需要 4 分钟，而 find 命令大约需要 40 秒。

我尝试删除排序算法，但并没有加快程序速度。

package main

import (
    "fmt"
    "io"
    "io/fs"
    "log"
    "os"
    "sort"
    "sync"

    "github.com/google/fscrypt/filesystem"
    "github.com/sirupsen/logrus"
    "gopkg.in/alecthomas/kingpin.v2"
)

var (
    mountpoint = kingpin.Flag("mount", "The mount to find the largest file usages. Can be a subath of mount").Required().String()
    limit      = kingpin.Flag("limit", "The maximum number of files return to the display").Default("10").Short('l').Int()
)
var device string

type fileDisplay struct {
    Size int64
    Path string
}
type bySize []fileDisplay

func (a bySize) Len() int           { return len(a) }
func (a bySize) Less(i, j int) bool { return a[i].Size < a[j].Size }
func (a bySize) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

var fileChan = make(chan fileDisplay)
var files []fileDisplay

func main() {
    log.SetOutput(io.Discard)
    kingpin.Version("0.0.1")
    kingpin.Parse()
    //Define limit after parsing
    logrus.SetLevel(logrus.FatalLevel)
    if (*mountpoint)[len(*mountpoint)-1:] != "/" {
        *mountpoint = *mountpoint + "/"
    }
    fmt.Println("Finding the top", *limit, "largest files on filesystem", *mountpoint, "\n================================================")
    mount, err := filesystem.FindMount(*mountpoint)
    if err != nil {
        logrus.Fatal(err)
    }
    device = mount.Device

    entries, err := os.ReadDir(*mountpoint)
    if err != nil {
        logrus.Fatal(err)
    }
    var wg sync.WaitGroup
    getFiles(*mountpoint, entries, &wg)
    go func() {
        defer close(fileChan)
        wg.Wait()
    }()
    var last int64
    for file := range fileChan {
        if file.Size > last {
            files = append(files, file)
        } else {
            files = append([]fileDisplay{file}, files...)
        }
    }
    sort.Sort(bySize(files))
    var shortFiles []fileDisplay
    if len(files) > *limit {
        shortFiles = files[len(files)-*limit:]
    } else {
        shortFiles = files
    }

    for _, file := range shortFiles {
        fmt.Println(file.Path, file.DisplaySizeIEC())
    }

}

func getFiles(start string, entries []fs.DirEntry, wg *sync.WaitGroup) {
    for _, entry := range entries {
        wg.Add(1)
        go handleEntry(start, entry, wg)
    }

}

func handleEntry(start string, entry fs.DirEntry, wg *sync.WaitGroup) {
    defer wg.Done()
    var file fileDisplay
    mount, err := filesystem.FindMount(start + entry.Name())
    if err != nil {
        logrus.Fatalln(err, start+entry.Name())
        return
    }
    if mount.Device == device {
        if entry.Type().IsRegular() {
            fileInfo, err := os.Stat(start + entry.Name())
            if err != nil {
                logrus.Fatalln(err, start+entry.Name())
                return
            }
            file.Path = start + entry.Name()
            file.Size = fileInfo.Size()
            fileChan <- file
        } else if entry.IsDir() {
            entries, err := os.ReadDir(start + entry.Name())
            if err != nil {
                logrus.Fatalln(err, start+entry.Name())
                return
            }
            logrus.Info("Searching ", start+entry.Name())
            getFiles(start+entry.Name()+"/", entries, wg)
        }
    }

}

func (f *fileDisplay) DisplaySizeIEC() string {
    const unit = 1024
    b := f.Size
    if b < unit {
        return fmt.Sprintf("%dB", b)
    }
    div, exp := int64(unit), 0
    for n := b / unit; n >= unit; n /= unit {
        div *= unit
        exp++
    }
    return fmt.Sprintf("%.2f%ciB",
        float64(b)/float64(div), "KMGTPE"[exp])
}

编辑：我尝试删除通道并仅附加到切片。这加快了速度，但并不安全，因为多个例程可能正在访问它。

正确答案

我的最终草案涉及删除通道并使用 sync.rwmutex 来锁定列表，并使用自定义附加函数来附加锁定。这使我能够放弃通道并使用追加，而无需冒多个例程编辑同一切片的风险。

我放弃了通道，因为这导致例程保持打开状态，直到打开通道上的 for 循环可以到达它们的消息。我的通道操作是 blocking。因此例程导致它减慢到 for 循环在通道上迭代的速度。

您可以在此处看到差异：

package main

import (
    "fmt"
    "io"
    "io/fs"
    "log"
    "os"
    "sort"
    "sync"

    "github.com/google/fscrypt/filesystem"
    "github.com/sirupsen/logrus"
    "gopkg.in/alecthomas/kingpin.v2"
)

var (
    mountpoint = kingpin.Flag("mount", "The mount to find the largest file usages. Can be a subath of mount").Required().String()
    limit      = kingpin.Flag("limit", "The maximum number of files return to the display").Default("10").Short('l').Int()
)
var device string

type fileDisplays struct {
    sync.RWMutex
    Files []fileDisplay
}

var files fileDisplays

type fileDisplay struct {
    Size int64
    Path string
}
type bySize []fileDisplay

func (a bySize) Len() int           { return len(a) }
func (a bySize) Less(i, j int) bool { return a[i].Size < a[j].Size }
func (a bySize) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

func main() {
    log.SetOutput(io.Discard)
    kingpin.Version("0.0.1")
    kingpin.Parse()
    //Define limit after parsing
    logrus.SetLevel(logrus.FatalLevel)
    if (*mountpoint)[len(*mountpoint)-1:] != "/" {
        *mountpoint = *mountpoint + "/"
    }
    fmt.Println("Finding the top", *limit, "largest files on filesystem", *mountpoint, "\n================================================")
    mount, err := filesystem.FindMount(*mountpoint)
    if err != nil {
        logrus.Fatal(err)
    }
    device = mount.Device

    entries, err := os.ReadDir(*mountpoint)
    if err != nil {
        logrus.Fatal(err)
    }
    var wg sync.WaitGroup
    getFiles(*mountpoint, entries, &wg)
    wg.Wait()
    sort.Sort(bySize(files.Files))
    var shortFiles []fileDisplay
    if len(files.Files) > *limit {
        shortFiles = files.Files[len(files.Files)-*limit:]
    } else {
        shortFiles = files.Files
    }

    for _, file := range shortFiles {
        fmt.Println(file.Path, file.DisplaySizeIEC())
    }

}

func getFiles(start string, entries []fs.DirEntry, wg *sync.WaitGroup) {
    for _, entry := range entries {
        wg.Add(1)
        go handleEntry(start, entry, wg)
    }

}

func handleEntry(start string, entry fs.DirEntry, wg *sync.WaitGroup) {
    defer wg.Done()
    var file fileDisplay
    mount, err := filesystem.FindMount(start + entry.Name())
    if err != nil {
        logrus.Errorln(err, start+entry.Name())
        return
    }
    if mount.Device == device {
        if entry.Type().IsRegular() {
            fileInfo, err := os.Stat(start + entry.Name())
            if err != nil {
                logrus.Errorln(err, start+entry.Name())
                return
            }
            file.Path = start + entry.Name()
            file.Size = fileInfo.Size()
            files.Append(file)
        } else if entry.IsDir() {
            entries, err := os.ReadDir(start + entry.Name())
            if err != nil {
                logrus.Errorln(err, start+entry.Name())
                return
            }
            logrus.Info("Searching ", start+entry.Name())
            getFiles(start+entry.Name()+"/", entries, wg)
        }
    }

}

func (f *fileDisplay) DisplaySizeIEC() string {
    const unit = 1024
    b := f.Size
    if b < unit {
        return fmt.Sprintf("%dB", b)
    }
    div, exp := int64(unit), 0
    for n := b / unit; n >= unit; n /= unit {
        div *= unit
        exp++
    }
    return fmt.Sprintf("%.2f%ciB",
        float64(b)/float64(div), "KMGTPE"[exp])
}

func (fd *fileDisplays) Append(item fileDisplay) {
    fd.Lock()
    defer fd.Unlock()

    fd.Files = append(fd.Files, item)
}

以上就是《为什么我的 Go 文件浏览程序运行缓慢？》的详细内容，更多关于的资料请关注golang学习网公众号！