从C＃调用非托管.dll的性能

Question

How long is the typical overhead added by calling a .dll written in C++ from a C# application using the following syntax?

[DllImport("abc.dll", EntryPoint = "xcFoo", CallingConvention = CallingConvention.Cdecl)]
public extern static Result Foo(out IntPtr session,
                [MarshalAs(UnmanagedType.FunctionPtr)]ObjectCallback callback, 
                UInt64 turnKey,
                string serverAddress, 
                string userId, 
                string password);

Is there a more efficient way to do it?

Answer 1

Check out this article on how to improve interop performance. What to do and what best to avoid.

http://msdn.microsoft.com/en-us/library/ms998551.aspx

Answer 2

Are you talking about the overhead of invoking the native method? If so, I dont think it is significant at all, as there are a lot of such calls in the .NET framework class libraries.

Now, whether the overhead is significant for your scenario can only be answered by doing performance measurements, and comparing them against what you expect.

Answer 3

The marshalling into the native method will cost three memory allocations from the NT heap, which is not so bad. It's the delegate back that gets worrysome.

Answer 4

我知道这个问题已经过时但我已经设法快速调用本机函数，不仅使用calli CIL指令而且还使用特殊技巧，但是如果你处理包括字符串在内的复杂类型，你需要自己处理pinnig和/或编组参数。 。

Answer 5

A good method to check this sort of thing is throw in a break point where you make calls. Don't know when the library is loaded, so maybe only check the break point on the second call (unless loading cost is your main concern). Then open up the disassembly window in visual studio and see how many lines there are before your dll function is being invoked.