另一种表达相同想法的方式是:

如果加速CPU并没有加速你的程序，它可能是I/O受限的。 如果加速I/O(例如使用更快的磁盘)没有帮助，那么您的程序可能是CPU受限的。

(我使用“可能是”是因为你需要考虑其他资源。内存就是一个例子。)

另一种表达相同想法的方式是:

如果加速CPU并没有加速你的程序，它可能是I/O受限的。 如果加速I/O(例如使用更快的磁盘)没有帮助，那么您的程序可能是CPU受限的。

(我使用“可能是”是因为你需要考虑其他资源。内存就是一个例子。)

看看微软怎么说。

The core of async programming is the Task and Task objects, which model asynchronous operations. They are supported by the async and await keywords. The model is fairly simple in most cases: For I/O-bound code, you await an operation which returns a Task or Task inside of an async method. For CPU-bound code, you await an operation which is started on a background thread with the Task.Run method. The await keyword is where the magic happens. It yields control to the caller of the method that performed await, and it ultimately allows a UI to be responsive or a service to be elastic.

I/ o绑定示例:从web服务下载数据

private readonly HttpClient _httpClient = new HttpClient();

downloadButton.Clicked += async (o, e) =>
{
    // This line will yield control to the UI as the request
    // from the web service is happening.
    //
    // The UI thread is now free to perform other work.
    var stringData = await _httpClient.GetStringAsync(URL);
    DoSomethingWithData(stringData);
};

cpu受限示例:为游戏执行计算

private DamageResult CalculateDamageDone()
{
    // Code omitted:
    //
    // Does an expensive calculation and returns
    // the result of that calculation.
}

calculateButton.Clicked += async (o, e) =>
{
    // This line will yield control to the UI while CalculateDamageDone()
    // performs its work.  The UI thread is free to perform other work.
    var damageResult = await Task.Run(() => CalculateDamageDone());
    DisplayDamage(damageResult);
};

Examples above showed how you can use async and await for I/O-bound and CPU-bound work. It's key that you can identify when a job you need to do is I/O-bound or CPU-bound, because it can greatly affect the performance of your code and could potentially lead to misusing certain constructs. Here are two questions you should ask before you write any code: Will your code be "waiting" for something, such as data from a database? If your answer is "yes", then your work is I/O-bound. Will your code be performing a very expensive computation? If you answered "yes", then your work is CPU-bound. If the work you have is I/O-bound, use async and await without Task.Run. You should not use the Task Parallel Library. The reason for this is outlined in the Async in Depth article. If the work you have is CPU-bound and you care about responsiveness, use async and await but spawn the work off on another thread with Task.Run. If the work is appropriate for concurrency and parallelism, you should also consider using the Task Parallel Library.

当你的程序正在等待I/O(即。磁盘读/写或网络读/写等)，即使程序停止，CPU也可以自由地执行其他任务。程序的速度主要取决于IO发生的速度，如果你想加快速度，就需要加快I/O。

如果你的程序正在运行大量的程序指令而不等待I/O，那么它就被称为CPU限制。加速CPU将使程序运行得更快。

在任何一种情况下，加速程序的关键可能不是加快硬件，而是优化程序以减少所需的IO或CPU数量，或者让它在执行CPU密集型操作的同时执行I/O。

IO绑定进程:花更多的时间做IO比计算，有很多 短CPU突发。 CPU绑定进程:花费更多的时间进行计算，很少有很长时间的CPU爆发

I/O限制是指完成计算所需的时间主要由等待输入/输出操作完成的时间决定的一种情况。

这与受CPU限制的任务相反。当请求数据的速度比消耗数据的速度慢时，或者换句话说，花费在请求数据上的时间比处理数据的时间多时，就会出现这种情况。