mTags: augmenting microkernel messages with lightweight metadata.

In this work we propose mTags, an efficient mechanism that augments microkernel interprocess messages with lightweight metadata to enable the development of new, system-wide functionality without requiring modification of the application source code. As such it is well suited for systems with a large legacy code base or third-party applications like phone and tablet applications. We explored mTags in a variety of different contexts in local and distributed system scenarios. For example, we detail use cases in areas including messaging-induced deadlocks and mode propagation. To demonstrate that mTags is technically feasible and practical, we implemented it in a commercial microkernel and executed multiple sets of standard benchmarks on two different computing architectures. The results clearly demonstrate that mTags has only negligible overhead and strong potential for many applications.