.NET 中的堆栈溢出导致 IIS 的 CPU 使用率达到 100% - 为什么没有 StackOverflowException？

发布于 2024-11-05 23:45:16 字数 419 浏览 0 评论 0原文

我在 Server 2008 R2 + IIS 7.5 上运行的 ASP.NET 应用程序中有一些代码。每当我加载特定页面时，它就会永远挂起并使 IIS 的 CPU 使用率达到 100%。我最终找到了问题所在。

public string Comments
{
    get { return this.Comments; }
}

糟糕 - 应该返回 this.Photo.Comments。所以，我的问题是，为什么 .NET 没有生成 StackOverflowException，而是让 IIS 以 100% CPU 运行的时间远远超过其应有的时间。根据我使用 .NET 编程的经验，执行上述操作时，需要几秒钟或更短的时间才能获得 StackOverflowException。那么它怎么可能还在IIS上运行了近30分钟呢？

原文

I had some code in an ASP.NET application running on Server 2008 R2 + IIS 7.5. Whenever I loaded a particular page, it would hang forever and send IIS to 100% CPU usage. I eventually tracked down the problem.

public string Comments
{
    get { return this.Comments; }
}

Oops - should have been return this.Photo.Comments. So, my question is, why didn't .NET generate a StackOverflowException, but instead let IIS run at 100% CPU for far longer than it should have taken. In my experience programming with .NET, it takes seconds or less to get a StackOverflowException when doing something like the above. So how could it still be running for almost 30 minutes on IIS?

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扎心 2024-11-12 23:45:16

JIT 编译器可能优化了对 YourClass::get_Comments() 的方法调用（这就是 IL 的样子），并使用 jmp 内联代码（或者无论 x86 汇编器是什么）循环构造，因为没有任何值被传递。只是一个想法。

这篇老文章值得一看：

Jit 优化：内联 (II)
“一个真正优秀的典型例子
内联候选者是一个属性
获取器/设置器。这些通常是
非常小的方法，通常只是
进行内存获取或存储，所以它是
通常尺寸和速度优于内联
他们。”

原样：

编写高性能托管应用程序：入门 - 托管代码和CLR JIT

我还使用一个简单的控制台应用程序重现了这一点：

class Program
{
  static void Main(string[] args)
  {
    MyClass mc = new MyClass();
    string s = mc.Comments;
  }
}

public class MyClass
{
  public string  Comments
  {
    get { return this.Comments; }
  }
}

在关闭优化的调试模式下，我抛出了堆栈溢出异常。打开 Jit 优化并编译发布版本后，应用程序将永远运行。这表明可能发生了内联循环。

C#2.0、3.0 和 4.0 似乎也是这种情况。

It's possible the JIT compiler optimised out a method call to YourClass::get_Comments() (which is what the IL would look like) and inlined the code with a jmp (or whatever the x86 assembler would be) loop construct because there weren't any values being passed around. Just a thought.

This old article is worth a look:

Jit Optimizations: Inlining (II)
"A typical example of a really good
candidate for inlining is a property
getter/setter. These are usually
really small methods that usually just
do a memory fetch or store, so it's
usually a size and speed win to inline
them."

As is:

Writing High-Performance Managed Applications : A Primer - Managed Code and the CLR JIT

I also reproduced this with a simple console application:

class Program
{
  static void Main(string[] args)
  {
    MyClass mc = new MyClass();
    string s = mc.Comments;
  }
}

public class MyClass
{
  public string  Comments
  {
    get { return this.Comments; }
  }
}

In debug mode with optimisations turned off I get a stack overflow exception thrown. Upon turning on Jit Optimisations and compiling a release build the app just runs forever. This suggests that inlining to a loop has probably happened.

This also appears to be the case with C#2.0, 3.0 and 4.0.

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