Redox's IPC is a fair bit weaker of a design than that of QNX or my seL4-derived kernel. It works sort of like that of QNX in that it has direct copying of messages between address spaces and RPC-like semantics with direct context switch from sender to receiver and back, but it is more limited and implemented in a slower way. Also, there seems to be no consideration for real-time performance at all.
Outside the core IPC model, the namespace model is also more limited than that of QNX; QNX allows multiple servers of a given type mounted anywhere within a namespace, whereas Redox's scheme-based namespace model only allows a single server of a given type per namespace, mounted on a fixed top-level prefix.
I think elaborate IPC designs are too much trouble, and I favor seL4's "context switch with benefits" approach of delegating larger messages to shared memory. It avoids performance and security hiccups with copying or kernel-mediated shared memory, like in EROS. To be fair, I'm less focused on efficiency and more on simplicity/robustness of the kernel, similar to seL4. Could you elaborate on your thoughts in the IPC space?
Outside the core IPC model, the namespace model is also more limited than that of QNX; QNX allows multiple servers of a given type mounted anywhere within a namespace, whereas Redox's scheme-based namespace model only allows a single server of a given type per namespace, mounted on a fixed top-level prefix.