不抛出异常时，try/catch 块是否会影响性能? [英] Do try/catch blocks hurt performance when exceptions are not thrown?

问题描述

在与 Microsoft 员工进行代码审查期间，我们在 try{} 块中发现了一大段代码.她和一位 IT 代表建议这会对代码的性能产生影响.事实上，他们建议大部分代码应该在 try/catch 块之外，并且只应该检查重要的部分.微软员工补充说，即将发布的白皮书警告不正确的 try/catch 块.

During a code review with a Microsoft employee we came across a large section of code inside a try{} block. She and an IT representative suggested this can have effects on performance of the code. In fact, they suggested most of the code should be outside of try/catch blocks, and that only important sections should be checked. The Microsoft employee added and said an upcoming white paper warns against incorrect try/catch blocks.

我环顾四周，发现它可以影响优化，但它似乎只适用于在范围之间共享变量的情况.

I've looked around and found it can affect optimizations, but it seems to only apply when a variable is shared between scopes.

我不是在问代码的可维护性，甚至不是处理正确的异常(毫无疑问，有问题的代码需要重构).我也不是指使用异常进行流量控制，这在大多数情况下显然是错误的.这些都是重要的问题(有些更重要)，但不是这里的重点.

I'm not asking about maintainability of the code, or even handling the right exceptions (the code in question needs re-factoring, no doubt). I'm also not referring to using exceptions for flow control, this is clearly wrong in most cases. Those are important issues (some are more important), but not the focus here.

当不抛出异常时，try/catch块如何影响性能?

How do try/catch blocks affect performance when exceptions are not thrown?

推荐答案

检查一下.

static public void Main(string[] args)
{
    Stopwatch w = new Stopwatch();
    double d = 0;

    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        try
        {
            d = Math.Sin(1);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
    }

    w.Stop();
    Console.WriteLine(w.Elapsed);
    w.Reset();
    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        d = Math.Sin(1);
    }

    w.Stop();
    Console.WriteLine(w.Elapsed);
}

输出:

00:00:00.4269033  // with try/catch
00:00:00.4260383  // without.

以毫秒为单位:

449
416

新代码:

for (int j = 0; j < 10; j++)
{
    Stopwatch w = new Stopwatch();
    double d = 0;
    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        try
        {
            d = Math.Sin(d);
        }

        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }

        finally
        {
            d = Math.Sin(d);
        }
    }

    w.Stop();
    Console.Write("   try/catch/finally: ");
    Console.WriteLine(w.ElapsedMilliseconds);
    w.Reset();
    d = 0;
    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        d = Math.Sin(d);
        d = Math.Sin(d);
    }

    w.Stop();
    Console.Write("No try/catch/finally: ");
    Console.WriteLine(w.ElapsedMilliseconds);
    Console.WriteLine();
}

新结果:

   try/catch/finally: 382
No try/catch/finally: 332

   try/catch/finally: 375
No try/catch/finally: 332

   try/catch/finally: 376
No try/catch/finally: 333

   try/catch/finally: 375
No try/catch/finally: 330

   try/catch/finally: 373
No try/catch/finally: 329

   try/catch/finally: 373
No try/catch/finally: 330

   try/catch/finally: 373
No try/catch/finally: 352

   try/catch/finally: 374
No try/catch/finally: 331

   try/catch/finally: 380
No try/catch/finally: 329

   try/catch/finally: 374
No try/catch/finally: 334

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