Question regarding DLL and dllimport

[elfeck]

Hello,

I've got a abstract, implicitly linked dll interface like this:

#ifndef CPH_DISPLAY_H_
#define CPH_DISPLAY_H_

#ifdef DISPLAY_EXPORTS
#define CPH_DISPLAY_DLL _declspec(dllexport)
#else
#define CPH_DISPLAY_DLL _declspec(dllimport)
#endif


namespace cph {

struct Display {

	virtual CPH_DISPLAY_DLL void setWidth(int width) = 0;
	virtual CPH_DISPLAY_DLL void setHeight(int height) = 0;
	virtual CPH_DISPLAY_DLL void setPosition(int x, int y) = 0;
	virtual CPH_DISPLAY_DLL void setFullscreen(bool fullscreen) = 0;
	virtual CPH_DISPLAY_DLL void setTitle(const char* title) = 0;
	virtual CPH_DISPLAY_DLL void setIcon(const char* iconPath) = 0;
	virtual CPH_DISPLAY_DLL void setDebug(bool debug) = 0;

	virtual CPH_DISPLAY_DLL int getWidth() = 0;
	virtual CPH_DISPLAY_DLL int getHeight() = 0;
	virtual CPH_DISPLAY_DLL int getPositionX() = 0;
	virtual CPH_DISPLAY_DLL int getPositionY() = 0;
	virtual CPH_DISPLAY_DLL bool isFullscreen() = 0;
	virtual CPH_DISPLAY_DLL const char* getTitle() = 0;
	virtual CPH_DISPLAY_DLL bool isDebug() = 0;

};

extern "C" {	
	CPH_DISPLAY_DLL Display* createDisplay();
	CPH_DISPLAY_DLL void deleteDisplay(Display* display);
};

}

#endif 

I found out that I can remove the CPH_DISPLAY_DLL infront of all the member functions an still have them exported by the dll.
So I've been thinking about doing this, but I'm concerned that removing the dllimport when importing the functions might affect performance. Is this the case? Should the be CPH_DISPLAY_DLL declared at every member function?

Thanks!