Re: [gentoo-embedded] real time linux

[David]

>How do I no if need a real time OS?

Ask yourself the following questions:
Do you have hard real-time constraints?  i.e.
    Do you have a task that needs to run exactly every nth millisecond 
(or microseconds)? 
    Do you have tasks that must run in under n milliseconds, every time?
    Do you need to be able to determine and rely on the maximum time a 
task may take?

If you answered yes to any of these questions you need a real-time system. 

I used milliseconds in the questions above, although technically 
speaking, any time deadline (seconds, minutes, hours, days...) could be 
considered a real-time constraint.  However if your deadlines are that 
long you probably  don't need real-time capabilities.

And Heath, you are correct, stock Linux (even embedded) is not an RTOS.  
There are real-time linuxes (?) out there that purport to support hard, 
real-time constraints (eg timesys) similar to Lynx, vxWorks or 
Integrity.  I have worked with people who were using timesys's linux, 
and they were largely happy with the performance (latency).  I believe 
you can get the timesys libraries for free, but the toolchains (cross 
compiler, linker...) will cost you.  There are free distros claiming 
real-time, but I cannot comment on their performance.

David


Francisco Ares wrote:

>Anything in portage?  Could not find it yet.
>
>And I have some doubts, if anyone could point me to some links,
>specially benchmarks, I would really appreciate:
>
>How do I no if need a real time OS?
>Should I rely only on the preemptibility of the 2.6 kernels?
>Which real time Linux flavor is best for which types of applications?
>
>
>Thanks a lot
>Francisco
>
>
>
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