You've probably already suspected that all the variants of the MsgRead(), MsgReceive(), MsgSend(), and MsgWrite() functions are closely related. (The only exception is MsgReceivePulse()—we'll look at this one shortly.)

Which ones should you use? Well, that's a bit of a philosophical debate. My own personal preference is to mix and match.

If I'm sending or receiving only one-part messages, why bother with the complexity of setting up IOVs? The tiny amount of CPU overhead in setting them up is basically the same regardless of whether you set it up yourself or let the kernel/library do it. The single-part message approach saves the kernel from having to do address space manipulations and is a little bit faster.

Should you use the IOV functions? Absolutely! Use them any time you find yourself dealing with multipart messages. Never copy the data when you can use a multipart message transfer with only a few lines of code. This keeps the system screaming along by minimizing the number of times data gets copied around the system; passing the pointers is much faster than copying the data into a new buffer.