泛型C#方法多态性的性能

我注意到,在C语言中,与C++不同,可以结合虚拟方法和泛型方法。例如:

using System.Diagnostics;

class Base {
    public virtual void Concrete() {Debug.WriteLine("base concrete");}
    public virtual void Generic<T>() {Debug.WriteLine("base generic");}
}

class Derived : Base {
    public override void Concrete() {Debug.WriteLine("derived concrete");}
    public override void Generic<T>() {Debug.WriteLine("derived generic");}
}

class App {
    static void Main() {
        Base x = new Derived();
        x.Concrete();
        x.Generic<PerformanceCounter>();
    }
}

考虑到 Generic<T> vtbl 方法可以用来解析方法调用,但事实上并非如此。下面是生成的代码:

        x.Concrete();
mov         ecx,dword ptr [ebp-8] 
mov         eax,dword ptr [ecx] 
call        dword ptr [eax+38h] 
        x.Generic<PerformanceCounter>();
push        989A38h 
mov         ecx,dword ptr [ebp-8] 
mov         edx,989914h 
call        76A874F1 
mov         dword ptr [ebp-4],eax 
mov         ecx,dword ptr [ebp-8] 
call        dword ptr [ebp-4] 

额外的代码似乎是根据泛型参数查找动态vtbl,然后调用它。有人写过这个实现的细节吗?与非通用情况相比,它的性能如何?