我正在运行一个程序,以测试在具有大量文件的文件夹中查找和迭代所有文件的速度。该过程中最慢的部分是创建100万多个文件。目前我使用的是相当幼稚的方法来创建这些文件:
Console.Write("Creating {0:N0} file(s) of size {1:N0} bytes... ",
options.FileCount, options.FileSize);
var createTimer = Stopwatch.StartNew();
var fileNames = new List<string>();
for (long i = 0; i < options.FileCount; i++)
{
var filename = Path.Combine(options.Directory.FullName,
CreateFilename(i, options.FileCount));
using (var file = new FileStream(filename, FileMode.CreateNew,
FileAccess.Write, FileShare.None, 4096,
FileOptions.WriteThrough))
{
// I have an option to write some data to files, but it's not being used.
// That's why there's a using here.
}
fileNames.Add(filename);
}
createTimer.Stop();
Console.WriteLine("Done.");
// Other code appears here.....
Console.WriteLine("Time to CreateFiles: {0:N3}sec ({1:N2} files/sec, 1 in {2:N4}ms)"
, createTimer.Elapsed.TotalSeconds
, (double)total / createTimer.Elapsed.TotalSeconds
, createTimer.Elapsed.TotalMilliseconds / (double)options.FileCount);
输出:
Creating 1,000,000 file(s) of size 0 bytes... Done.
Time to CreateFiles: 9,182.283sec (1,089.05 files/sec, 1 in 9.1823ms)
有什么比这更好的方法吗?我希望测试超过100万个数量级,但创建文件需要一整天的时间!我还没有尝试任何形式的并行处理,尝试优化任何文件系统选项或更改文件创建顺序。为了完整起见,这里是“CreateFilename()”的内容:
public static string CreateFilename(long i, long totalFiles)
{
if (totalFiles < 0)
throw new ArgumentOutOfRangeException("totalFiles",
totalFiles, "totalFiles must be positive");
// This tries to keep filenames to the 8.3 format as much as possible.
if (totalFiles < 99999999)
// No extension.
return String.Format("{0:00000000}", i);
else if (totalFiles >= 100000000 && totalFiles < 9999999999)
{
// Extend numbers into extension.
long rem = 0;
long div = Math.DivRem(i, 1000, out rem);
return String.Format("{0:00000000}", div) + "." +
String.Format("{0:000}", rem);
}
else
// Doesn't fit in 8.3, so just tostring the long.
return i.ToString();
}
更新
按照StriplingWarrior的建议尝试使用Parallel.For()
进行并行化。结果:约30个线程在我的磁盘上疯狂运转,导致网络速度变慢!
var fileNames = new ConcurrentBag<string>();
var opts = new ParallelOptions();
opts.MaxDegreeOfParallelism = 1; // 1 thread turns out to be fastest.
Parallel.For(0L, options.FileCount, opts,
() => new { Files = new List<string>() },
(i, parState, state) =>
{
var filename = Path.Combine(options.Directory.FullName,
CreateFilename(i, options.FileCount));
using (var file = new FileStream(filename, FileMode.CreateNew
, FileAccess.Write, FileShare.None
, 4096, FileOptions.WriteThrough))
{
}
fileNames.Add(filename);
return state;
},
state =>
{
foreach (var f in state.Files)
{
fileNames.Add(f);
}
});
createTimer.Stop();
Console.WriteLine("Done.");
发现在
FileStream
中更改FileOptions
可以提高性能约50%。看来我关闭了任何写缓存。new FileStream(filename, FileMode.CreateNew,
FileAccess.Write, FileShare.None,
4096, FileOptions.None)
结果:
Creating 10,000 file(s) of size 0 bytes... Done.
Time to CreateFiles: 12.390sec (8,071.05 files/sec, 1 in 1.2390ms)
欢迎提出其他想法。