.NET:ThreadStatic vs lock {}.为什么ThreadStaticAttribute会降低性能？

Question

我写了一个小的测试程序,并且很惊讶为什么lock {}解决方案比无锁更快但是[ThreadStatic]属性超过静态变量.

[ThreadStatic]片段:

[ThreadStatic]
private static long ms_Acc;
public static void RunTest()
{
    Stopwatch stopwatch = new Stopwatch();
    stopwatch.Start();
    int one = 1;
    for (int i = 0; i < 100 * 1000 * 1000; ++i) {
        ms_Acc += one;
        ms_Acc /= one;
    }
    stopwatch.Stop();
    Console.WriteLine("Time taken: {0}", stopwatch.Elapsed.TotalSeconds);
}

lock {}摘要:

private static long ms_Acc;
private static object ms_Lock = new object();
public static void RunTest()
{
    Stopwatch stopwatch = new Stopwatch();
    stopwatch.Start();
    int one = 1;
    for (int i = 0; i < 100 * 1000 * 1000; ++i) {
        lock (ms_Lock) {
            ms_Acc += one;
            ms_Acc /= one;
        }
    }
    stopwatch.Stop();
    Console.WriteLine("Time taken: {0}", stopwatch.Elapsed.TotalSeconds);
}

在我的机器上,第一个片段需要4.2秒; 秒 - 3.2秒,这快1秒.没有ThreadStatic和锁定 - 1.2秒.

我很好奇为什么[ThreadStatic]这个简单的例子中的属性会增加很多程序执行时间？

更新:我感到非常抱歉,但这些结果是为了DEBUG构建.对于RELEASE一个我有完全不同的数字:(1.2; 2.4; 1.2).对于DEBUG数分别为(4.2; 3.2; 1.2).

因此,对于RELEASE构建,似乎没有[ThreadStatic]性能损失.

Answer 1

对于RELEASE构建,似乎几乎没有[ThreadStatic]性能损失(现代CPU上只有轻微的损失).

这里有拆卸代码ms_Acc += one; 对于RELEASE已启用优化:

不 [ThreadStatic],DEBUG:

00000060  mov         eax,dword ptr [ebp-40h] 
00000063  add         dword ptr ds:[00511718h],eax 

不 [ThreadStatic],RELEASE:

00000051  mov         eax,dword ptr [00040750h]
00000057  add         eax,dword ptr [rsp+20h]
0000005b  mov         dword ptr [00040750h],eax

[ThreadStatic],DEBUG:

00000066  mov         edx,1 
0000006b  mov         ecx,4616E0h 
00000070  call        664F7450 
00000075  mov         edx,1 
0000007a  mov         ecx,4616E0h 
0000007f  mov         dword ptr [ebp-50h],eax 
00000082  call        664F7450 
00000087  mov         edx,dword ptr [eax+18h] 
0000008a  add         edx,dword ptr [ebp-40h] 
0000008d  mov         eax,dword ptr [ebp-50h] 
00000090  mov         dword ptr [eax+18h],edx 

[ThreadStatic],RELEASE:

00000058  mov         edx,1 
0000005d  mov         rcx,7FF001A3F28h 
00000067  call        FFFFFFFFF6F9F740 
0000006c  mov         qword ptr [rsp+30h],rax 
00000071  mov         rbx,qword ptr [rsp+30h] 
00000076  mov         ebx,dword ptr [rbx+20h] 
00000079  add         ebx,dword ptr [rsp+20h] 
0000007d  mov         edx,1 
00000082  mov         rcx,7FF001A3F28h 
0000008c  call        FFFFFFFFF6F9F740 
00000091  mov         qword ptr [rsp+38h],rax 
00000096  mov         rax,qword ptr [rsp+38h] 
0000009b  mov         dword ptr [rax+20h],ebx