4 ms·

I don't know QNX, but for IPC you should also take a good look at the L4 microkernel IPCs. It might be what you describe here. The point is that they are fast.

by qznc 10y ago

I don't know QNX, but for IPC you should also take a good look at the L4 microkernel IPCs. It might be what you describe here. The point is that they are fast. Nearly function-call-speed. The should probably a more complex IPC layer on top or beside it. Something like DBus with schemas, names, groups, broadcasts, etc because otherwise people will reinvent it poorly.

dfox 10y ago
The big question with IPC is what problem you are trying to solve. For microkernels you want blazingly fast cross-process function calls, but IPC mecanism that can do only that is mostly useless for Unix userspace. For example all of QNX style IPC, traditional SysV-style unix IPC and pthreads have no API for select()-on-IPC-primitive (VMS and Symbian have that and NT has mechanism for this that mostly works)
wolfgke 10y ago
> The should probably a more complex IPC layer on top or beside it. Something like DBus with schemas, names, groups, broadcasts, etc because otherwise people will reinvent it poorly. People also tend to reinvent stuff poorly that they consider as "bloated" or "unnecessarily complex for their use case". I just say C++ vs. Java (Java was indeed also marketed at the beginning that C++ is unnecessarily complex; besides the famous "write once, runs everywhere"), XML vs. JSON, CORBA vs. SOAP (no, please don't start a flame war which of these is the better one ;-) ).
- ethbro 10y ago
  I'd sum it up in terms of "standards bodies / enterprise would be perfectly happy if everything were ossified in a form that encompassed all possible use cases, regardless of complexity." Whereas reimplementation in a lighter weight protocol is usually the result of "devs don't want to deal with the above when it isn't needed for 80% of common use cases."
Animats 10y ago
QNX IPC is deliberately just a delivery mechanism for a byte string. That's the OS level. You can put JSON, Google protocol buffers, or something else on top of it. In the hard real-time world, it's common to just pass known C structs with the necessary data items around. The OS doesn't care. If you're implementing microservices, it's quite useful. I did a robot vehicle that way. All the Boston Dynamics robots run QNX.

by qznc 10y ago

dfox 10y ago

The big question with IPC is what problem you are trying to solve. For microkernels you want blazingly fast cross-process function calls, but IPC mecanism that can do only that is mostly useless for Unix userspace. For example all of QNX style IPC, traditional SysV-style unix IPC and pthreads have no API for select()-on-IPC-primitive (VMS and Symbian have that and NT has mechanism for this that mostly works)

wolfgke 10y ago

> The should probably a more complex IPC layer on top or beside it. Something like DBus with schemas, names, groups, broadcasts, etc because otherwise people will reinvent it poorly. People also tend to reinvent stuff poorly that they consider as "bloated" or "unnecessarily complex for their use case". I just say C++ vs. Java (Java was indeed also marketed at the beginning that C++ is unnecessarily complex; besides the famous "write once, runs everywhere"), XML vs. JSON, CORBA vs. SOAP (no, please don't start a flame war which of these is the better one ;-) ).

ethbro 10y ago
I'd sum it up in terms of "standards bodies / enterprise would be perfectly happy if everything were ossified in a form that encompassed all possible use cases, regardless of complexity." Whereas reimplementation in a lighter weight protocol is usually the result of "devs don't want to deal with the above when it isn't needed for 80% of common use cases."

Animats 10y ago

QNX IPC is deliberately just a delivery mechanism for a byte string. That's the OS level. You can put JSON, Google protocol buffers, or something else on top of it. In the hard real-time world, it's common to just pass known C structs with the necessary data items around. The OS doesn't care. If you're implementing microservices, it's quite useful. I did a robot vehicle that way. All the Boston Dynamics robots run QNX.