在以下代码中，我使用golang中的bufio将消息写入文件。我的磁盘I/O速度约为1000M/s。奇怪的是，当写入文件的大小小于20G时，写入速度大约为800M〜900M每秒，比I/O速度略低一点。但是，当文件大小超过21G时，我发现写入速度大约为每秒200M，远远低于I/O速度。我不知道为什么，有人可以帮助我？谢谢。 package main import "fmt" import ( "os" "time" "flag" "bufio" ) func main() { var pRound = flag.Int64("round", 3500000, "loop round") flag.Parse() var message string for i := 0; i < 1024; i++ { message += "1234567890" } message += "\n" f, err := os.OpenFile("server", os.O_CREATE|os.O_APPEND|os.O_RDWR, 0666) if err != nil { fmt.Println(err) return } w := bufio.NewWriter(f) var i int64 = 0 round := *pRound start := time.Now() for i = 0; i < round; i++ { w.WriteString(message) } w.Flush() f.Close() end := time.Now() nanoseconds := end.Sub(start).Nanoseconds() speed := 1000000000 * round/nanoseconds fmt.Printf("round: %v\n", round) fmt.Printf("Nanoseconds: %v\n", nanoseconds) fmt.Printf("speed: %v\n", speed) } 我想我已经问过一个愚蠢的问题。关于Vorsprung的回应，我在这里展示了我的C代码。我用C语言再次测试它。我用go语言找到了相同的结果。我的测试结果是： ./a.out 10000 seconds: 7 milliseconds: 260910 total: 10485760000 Bytes total: 10000 M total: 9.76562 G speed: 1377.24 M/s ./a.out 20000 seconds: 24 milliseconds: 7249 total: 20971520000 Bytes total: 20000 M total: 19.5312 G speed: 833.082 M/s ./a.out 30000 seconds: 80 milliseconds: 518970 total: 31457280000 Bytes total: 30000 M total: 29.2969 G speed: 372.583 M/s ./a.out 40000 seconds: 134 milliseconds: 615910 total: 41943040000 Bytes total: 40000 M total: 39.0625 G speed: 297.142 M/s 以下是我的C代码： #include <fcntl.h> #include <errno.h> #include <limits.h> #include <sys/uio.h> #include <time.h> #include <sys/time.h> #include <iostream> #include <string.h> #include <stdlib.h> int main(int argc, char* argv[]) { if (argc != 2) { std::cout << "usage: " << argv[0] << " round" << std::endl; return -1; } int round = atoi(argv[1]); int fd = open("file.data", O_CREAT | O_APPEND | O_RDWR, 0666); if (fd == -1) { std::cout << "open file error: " << strerror(errno) << std::endl; return -1; } struct iovec vec[IOV_MAX]; int len = 1024; for (int i = 0; i < IOV_MAX; i++) { vec[i].iov_base = new char[len]; vec[i].iov_len = len; char *buf = NULL; for (int j = 0; j < len - 1; j++) { buf = (char*)vec[i].iov_base; buf[j] = j % 10 + '1'; } buf[len - 1] = '\n'; } timeval tv1; gettimeofday(&tv1, NULL); for (int i = 0; i < round; i++) { writev(fd, vec, IOV_MAX); } close(fd); timeval tv2; gettimeofday(&tv2, NULL); for (int i = 0; i < IOV_MAX; i++) { char* buf = (char*)vec[i].iov_base; delete[] buf; } std::cout << "seconds: " << tv2.tv_sec - tv1.tv_sec << std::endl; std::cout << "milliseconds: " << tv2.tv_usec - tv1.tv_usec << std::endl; int64_t total = int64_t(len) * IOV_MAX * round; float t = (tv2.tv_sec - tv1.tv_sec) * 1000000.0 + (tv2.tv_usec - tv1.tv_usec); float speed = 1000000.0 * total/t/1024/1024; std::cout << "total: " << total << " Bytes" << std::endl; std::cout << "total: " << total/1024.0/1024.0 << " M" << std::endl; std::cout << "total: " << total/1024.0/1024.0/1024.0 << " G" << std::endl; std::cout << "speed: " << speed << " M/s" << std::endl; return 0; } 现在我diskio.go测试结果显示在这里。因为我不知道如何评论简单阅读的结果，所以我在这里展示它。 time ./diskio -size=4 written: 4294967296B 26237051975ns 4.29GB 26.24s 163.70MB/s real 0m26.980s user 0m0.397s sys 0m4.874s time ./diskio -size=8 written: 8589934592B 57803019028ns 8.59GB 57.80s 148.61MB/s real 0m59.192s user 0m0.813s sys 0m9.607s time ./diskio -size=10 written: 10737418240B 68331989999ns 10.74GB 68.33s 157.14MB/s real 1m10.288s user 0m0.946s sys 0m12.024s time ./diskio -size=20 written: 21474836480B 141169506440ns 21.47GB 141.17s 152.12MB/s real 2m25.037s user 0m1.881s sys 0m24.029s time ./diskio -size=30 written: 32212254720B 203807569664ns 32.21GB 203.81s 158.05MB/s real 3m29.345s user 0m2.925s sys 0m33.528s diskio.go来自https://stackoverflow.com/a/47889346/5616809 我觉得我得到了答案，测试结果由磁盘缓冲区的原因造成的。我测试了我的硬盘速度使用hdparm表彰，而我得到这个： hdparm -Tt /dev/sde1 /dev/sde1: Timing cached reads: 18166 MB in 2.00 seconds = 9093.93 MB/sec Timing buffered disk reads: 584 MB in 3.01 seconds = 194.18 MB/sec 所以，也许我的程序书面方式字节缓冲区时，文件大小小于约18166M。之后，该程序正在写入磁盘，所以速度较慢。