midl /Os
midl /Os filename.idl
The /Os switch specifies the mixed-mode method to marshal stub code passed between client and server.
There are important issues to consider before deciding on the method for marshalling code. These issues concern size and performance. The MIDL 2.0 compiler provides two methods for marshalling code: mixed-mode (/Os) and fully-interpreted (/Oi). The fully-interpreted method marshals data completely offline. This reduces the size of the stub code considerably, but it also results in decreased performance.
If performance is an important concern, the mixed-mode method (/Os) can be the best approach. In this mode, the compiler marshals some parameters inline in the generated stubs. While this results in larger stub size, it also offers increased performance. Because mixed-mode is the default, you do not need to explicitly select the /Os switch to accomplish mixed-mode marshalling.
To further define the level of gradiation in how data is marshalled, this version of RPC provides an optimize attribute. This attribute is used as an ACF interface attribute or operation attribute to select the marshalling mode.
General MIDL Command-line Syntax, /Oi, optimize, /no_format_opt