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。golang的磁盘写入性能
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。
很可能是因为你的磁盘缓冲区在那一点饱和了吗? – Flimzy
几个月前,我用C语言中的'writev'方法写了一个类似的过程。我发现写入速度几乎等于磁盘I/O速度。这是否可以证明它与磁盘缓冲区无关? –
剖析你的代码,这是关于你最好的希望。如果性能下降超过21G,则应该在配置文件中看到一些内容。最有可能的是等待。 – Marc