Context Switch in Real Time Linux Vs VxWorks (or any other RTOS)

[Gary Thomas]

On Fri, 2004-07-16 at 00:50, Oliver Korpilla wrote:
> Arun Prasad Velu wrote:
> >
> >I am in the process of analyzing the feasibility of migrating an
> >existing VxWorks system (MPC860 target) to Linux (RTOS).
> >
> >I'd like to compare the features of Linux and VxWorks with respect to
> >the Real Time capabilities. I am little concerned about Linux's Context
> >Switching.
> >
> >I'd like to get your opinion on this. Even if I want to move to Linux,
> >I'll have to convince my management. So, any pointers on comparison of
> >Linux Vs VxWorks with respect to Real Time capabilities would be highly
> >appreciated.
>
> I hardly guess context switching will be your main problem, because the
> stock Linux kernel does not support hard realtime!
>
> You either have to use RTAI (free kernel modification that requires
> drivers to be rewritten for realtime), RTLinux (nearly the same,
> non-free, patented) or modified Linux kernels from TimeSys or MontaVista
> (who both add real-time capabilities in a more stock-Linux-compliant way).
>
> Depending on your target, eCos (a free embedded operating system with a
> focus on minimal code) may be the better choice for you, especially if
> your platform is already supported.

Thanks for the plug :-)  [n.b. I am one of the main eCos developers]
FYI, look to http://sources.redhat.com/ecos for details.

>
> Be warned: Not all PowerPC processors are supported in eCos (last time I
> checked 74xx and 7xx were missing).

Ah, but they are simple to add (and have been, but not necessarily
public) as they are effectively PPC60x processors with some differences.

--
Gary Thomas <gary at mlbassoc.com>
MLB Associates


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