Go語言中寫文件有多種方式，這里進(jìn)行如下幾種方式的速度對(duì)比：

打開文件，寫入內(nèi)容，關(guān)閉文件。如此重復(fù)多次

打開文件，寫入內(nèi)容，defer 關(guān)閉文件。如此重復(fù)多次

打開文件，重復(fù)多次寫入內(nèi)容，defer 關(guān)閉文件

在VMWare下的Ubuntu 14.04下運(yùn)行的結(jié)果表明：

• 方式1速度最慢，但是慢的很穩(wěn)定
• 方式2比方式1略快，但是重復(fù)次數(shù)多了后會(huì)報(bào)錯(cuò)，應(yīng)該是defer被壓棧太多導(dǎo)致系統(tǒng)撐不了太多打開的文件
• 方式3速度約是前兩者的2倍，因?yàn)闇p少了很多打開關(guān)閉文件的操作

測試代碼如下：

package mainimport ("fmt""os""time" )func benchmarkFileWrite(filename string, n int, index int) (d time.Duration) {v := "ni shuo wo shi bu shi tai wu liao le a?"os.Remove(filename)t0 := time.Now()switch index {case 0: // open file and write, then close, repeat n timesfor i := 0; i < n; i++ {file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)if err != nil {fmt.Println(index, i, "open file failed.", err.Error())break}file.WriteString(v)file.WriteString("\n")file.Close()}case 1: // open file and write, defer close, repeat n timesfor i := 0; i < n; i++ {file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)if err != nil {fmt.Println(index, i, "open file failed.", err.Error())break}defer file.Close()file.WriteString(v)file.WriteString("\n")}case 2: // open file and write n times, then close filefile, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)if err != nil {fmt.Println(index, "open file failed.", err.Error())break}defer file.Close()for i := 0; i < n; i++ {file.WriteString(v)file.WriteString("\n")}}t1 := time.Now()d = t1.Sub(t0)fmt.Printf("time of way(%d)=%v\n", index, d)return d }func main() {const k, n int = 3, 1000d := [k]time.Duration{}for i := 0; i < k; i++ {d[i] = benchmarkFileWrite("benchmarkFile.txt", n, i)}for i := 0; i < k-1; i++ {fmt.Printf("way %d cost time is %6.1f times of way %d\n", i, float32(d[i])/float32(d[k-1]), k-1)} }

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當(dāng)n=1000時(shí)，測試結(jié)果如下

time of way(0)=38.719386mstime of way(1)=31.428677mstime of way(2)=17.930829msway 0 cost time is 2.2 times of way 2way 1 cost time is 1.8 times of way 2

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當(dāng)n=5000時(shí)，測試結(jié)果如下（因?yàn)榉绞?報(bào)錯(cuò)，所以它的時(shí)間是錯(cuò)的）

time of way(0)=170.003521ms1 1021 open file failed. open benchmarkFile.txt: too many open filestime of way(1)=32.388994mstime of way(2)=77.777936msway 0 cost time is 2.2 times of way 2way 1 cost time is 0.4 times of way 2

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轉(zhuǎn)載于:https://www.cnblogs.com/journeyonmyway/p/4320987.html

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