Re: Shared Memory for Application/Communication decoupling
- From: ChrisQuayle <nospam@xxxxxxxxxxxx>
- Date: Fri, 08 Dec 2006 16:52:23 GMT
Christian Walter wrote:
Of course each IPC method brings in its own piece of code and using different IPC methods within a single task will introduce a lot of complexity.
Thanks a lot for sharing. Still I can't agree on this point because I
think the interface requirements are quite different. For example look
at other systems where different IPC mechanisms are used when
appropriate (EJB - Enterprise Java Beans with Locale and Remote
Interface to name only one). Maybe this would be a interesting poll for
the ESD magazine - ?Type of IPC mechanisms used today".
Kind regards,
Christian Walter
I don't want to get into arguments about semantics, but in general, shared memory techniques are just a nice way of saying 'global data'. If you have > 1 writer, you have to do all the synchronisation and mutual exclusion at low level, where it's difficult to maintian visibility and keep track of.
A messaging based interface is generally more elegant and arguably more reliable, since for any single message, only one task writes and one task reads the data. This means that you can elevate syncronisation issues to a higher, task based level. Message based ipc reinforces an object view of the design at global level.
On modern micros, the overhead is probably insignificant as well. Shared memory / global data is a thing of the past, from the days when micros were not very powerfull...
Regards,
Chris
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