NodeJS通过流复制文件非常慢-NodeJSCopyingFileoverastreamisveryslow

I am copying file with Node on an SSD under VMWare, but the performance is very low. The benchmark I have run to measure actual speed is as follows:

我在VMWare下的SSD上使用Node复制文件，但性能非常低。我测量实际速度的基准如下：

$ hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   12004 MB in  1.99 secOnds= 6025.64 MB/sec
 Timing buffered disk reads: 1370 MB in  3.00 secOnds= 456.29 MB/sec

However, the following Node code that copies file is very slow, evne teh consequent runs do not make it faster:

但是，以下复制文件的节点代码非常慢，因此后续运行不会使其更快：

var fs  = require("fs");
fs.createReadStream("bigfile").pipe(fs.createWriteStream("tempbigfile"));

And the runs as:

运行如下：

$ seq 1 10000000 > bigfile
$ ll bigfile -h
-rw-rw-r-- 1 mustafa mustafa 848M Jun  3 03:30 bigfile
$ time node test.js 

real    0m4.973s
user    0m2.621s
sys     0m7.236s
$ time node test.js 

real    0m5.370s
user    0m2.496s
sys     0m7.190s

What is the issue here and how can I speed it up? I believe I can write it faster in C by just adjusting the buffer size. The thing that confuses me is that when I wrote simple almost pv equivalent program, that pipes stdin to stdout as the below, it is very fast.

这里有什么问题，如何加快速度？我相信只需调整缓冲区大小，我就可以在C中更快地编写它。令我困惑的是，当我编写简单的几乎pv等效程序时，将stdin管道传输到stdout，如下所示，它非常快。

process.stdin.pipe(process.stdout);

And the runs as:

运行如下：

$ dd if=/dev/zero bs=8M count=128 | pv | dd of=/dev/null
128+0 records in 174MB/s] [        <=>                                                                                ]
128+0 records out
1073741824 bytes (1.1 GB) copied, 5.78077 s, 186 MB/s
   1GB 0:00:05 [ 177MB/s] [          <=>                                                                              ]
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 5.78131 s, 186 MB/s
$ dd if=/dev/zero bs=8M count=128 |  dd of=/dev/null
128+0 records in
128+0 records out
1073741824 bytes (1.1 GB) copied, 5.57005 s, 193 MB/s
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 5.5704 s, 193 MB/s
$ dd if=/dev/zero bs=8M count=128 | node test.js | dd of=/dev/null
128+0 records in
128+0 records out
1073741824 bytes (1.1 GB) copied, 4.61734 s, 233 MB/s
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 4.62766 s, 232 MB/s
$ dd if=/dev/zero bs=8M count=128 | node test.js | dd of=/dev/null
128+0 records in
128+0 records out
1073741824 bytes (1.1 GB) copied, 4.22107 s, 254 MB/s
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 4.23231 s, 254 MB/s
$ dd if=/dev/zero bs=8M count=128 | dd of=/dev/null
128+0 records in
128+0 records out
1073741824 bytes (1.1 GB) copied, 5.70124 s, 188 MB/s
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 5.70144 s, 188 MB/s
$ dd if=/dev/zero bs=8M count=128 | node test.js | dd of=/dev/null
128+0 records in
128+0 records out
1073741824 bytes (1.1 GB) copied, 4.51055 s, 238 MB/s
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 4.52087 s, 238 MB/s

1 个解决方案

var fs = require('fs');
var path = require('path');
var from = path.normalize(process.argv[2]);
var to = path.normalize(process.argv[3]);

var readOpts = {highWaterMark: Math.pow(2,16)};
var writeOpts = {highWaterMark: Math.pow(2,16)};

var source = fs.createReadStream(from, readOpts);
var destiny = fs.createWriteStream(to, writeOpts)

source.pipe(destiny);