这是一个不好的想法。这可能会启动太多的线程。
一个更好的方法是简单地使用
Parallel.ForEach()
,像这样:
using System;
using System.IO;
using System.Threading.Tasks;
namespace Demo
{
static class Program
{
static void Main()
{
string filename = @"Your test filename goes here";
Parallel.ForEach(File.ReadLines(filename), process);
}
private static void process(string line)
{
Console.WriteLine(line);
}
}
}
这段代码没有使用async/await。但是,如果你想的话,你可以将对
Parallel.ForEach()
的整个调用包装在一个任务中。
或者,如果你想使用
Task Parallel Library(一个Microsoft NuGet包),你可以这样做:
using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;
namespace Demo
{
static class Program
{
static void Main()
{
Task.Run(test).Wait();
}
static async Task test()
{
string filename = @"Your filename goes here";
await processFile(filename);
}
static async Task processFile(string filename)
{
var options = new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 8, BoundedCapacity = 100 };
var action = new ActionBlock<string>(s => process(s), options);
foreach (var line in File.ReadLines(filename))
await action.SendAsync(line);
action.Complete();
await action.Completion;
}
static void process(string line)
{
Thread.Sleep(100);
Console.WriteLine(Thread.CurrentThread.ManagedThreadId + " " + line);
}
}
}
这将为您提供
async
支持。
附录:线程池速率控制的演示。
(这是针对shay__的评论做出的回应。)
如果您启动了许多长时间运行的任务,其中任务运行时间超过一秒左右,您可能会看到线程池速率控制。
如果当前进程的线程池线程数等于或超过调用ThreadPool.GetMinThreads(out workers, out ports);
返回的worker
计数,则会发生这种情况。
如果发生这种情况,在创建新的线程池线程之前,将会延迟一小段时间(在我的系统上为一秒)。通常情况下,这将允许另一个线程池线程变得可用,并且将使用它(这当然是速率控制的主要原因)。
以下代码演示了这个问题:
int workers, ports;
ThreadPool.GetMinThreads(out workers, out ports);
Console.WriteLine("Min workers = " + workers);
var sw = Stopwatch.StartNew();
for (int i = 0; i < 100; ++i)
{
Task.Run(() =>
{
Console.WriteLine($"Thread {Thread.CurrentThread.ManagedThreadId} started at time {sw.Elapsed}");
Thread.Sleep(10000);
});
}
Console.ReadLine();
在我的系统上,这将打印出以下内容:
Min workers = 8
Thread 3 started at time 00:00:00.0098651
Thread 6 started at time 00:00:00.0098651
Thread 8 started at time 00:00:00.0099841
Thread 5 started at time 00:00:00.0099680
Thread 7 started at time 00:00:00.0099918
Thread 4 started at time 00:00:00.0098739
Thread 10 started at time 00:00:00.0100828
Thread 9 started at time 00:00:00.0101833
Thread 11 started at time 00:00:01.0096247
Thread 12 started at time 00:00:02.0098105
Thread 13 started at time 00:00:03.0099824
Thread 14 started at time 00:00:04.0100671
Thread 15 started at time 00:00:05.0098035
Thread 16 started at time 00:00:06.0099449
Thread 17 started at time 00:00:07.0096293
Thread 18 started at time 00:00:08.0106774
Thread 19 started at time 00:00:09.0098193
Thread 20 started at time 00:00:10.0104156
Thread 3 started at time 00:00:10.0109315
Thread 8 started at time 00:00:10.0112171
Thread 7 started at time 00:00:10.0112531
Thread 9 started at time 00:00:10.0117256
Thread 4 started at time 00:00:10.0117920
Thread 10 started at time 00:00:10.0117298
Thread 6 started at time 00:00:10.0109381
Thread 5 started at time 00:00:10.0112276
Thread 21 started at time 00:00:11.0095859
Thread 11 started at time 00:00:11.0101189
Thread 22 started at time 00:00:12.0095421
Thread 12 started at time 00:00:12.0111173
Thread 23 started at time 00:00:13.0095932 ...
请注意前8个线程启动非常快,但是随后新的线程被限制在每秒钟左右一个,直到第一批线程终止并可以被重用。同时要注意,只有当线程花费相对较长的时间才能终止时,才会出现这种效果。