[E-Lang] Performance and complete mediation

Ken Kahn kenkahn@toontalk.com
Tue, 14 Aug 2001 13:47:08 -0700


Jonathan S. Shapiro wrote:
>
> However, it's important to acknowledge that the copy overhead is a
> *necessary* cost. There is a certain minimum time to move the bytes, and a
> certain minimal overhead to validate the mappings, and you really wouldn't
> want to give up either of these operations. The question we want to ask,
> then, is given that there is a hard minimum to the cost of
> protection-motivated copies, is this cost acceptable in the context of
some
> given system.
>

I would like to understand better why this coping is necessary. An example
of where copying is optional is in Microsoft's DirectPlay API (designed for
networked games).  Using DPNSEND_NOCOPY you can send a message without
copying. See

http://msdn.microsoft.com/library/en-us/dx8_c/hh/dx8_c/play_iface_0jax.asp

Best,

-ken