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View Full Version : Realtime systems and OS dependency


Hero
September 16th, 2006, 00:31
Hi all
I have a question about realtime system development.
As a lot of you know,in realtime systems reliablity of answering time is too important.You shoulb be sure that you can answer the request in a verrry short period of time when they happen.
This will make a high dependency between the application itself,and its operating OS,because of their algorithms in time scheduling for processes. Because we should be sure that our process will obtain CPU in proper time for answering request.
I heared that in some OSs like "Realtime linux":
www.realtimelinuxfoundation.org
you can force OS to gain CPU to a specific process in a promised time.
Now here is my question:
You can set a process priority to realtime and even bind it to seprated cores and processors in Windows that windows say that it will get more cpu to your process,but is it possible that we can be sure that our process will gain processor in a specific time?Is there anyway to do this?

sincerely yours

LLXX
September 16th, 2006, 02:13
This is probably impossible, as Windows was never intended as a realtime OS.

Maximus
September 16th, 2006, 03:24
Well...
Technically you could
A) write a driver that reprogram the APIC.
B) force the Windows Scheduler to schedule your task by directly altering the scheduler.

It was a common technique at old MS-DOS times, just remember to send the EOI at end of interrupt before IRET... but notice that on P4 families the APIC is not an easy toy anymore.
Do not rely on windows insterrupt machine, and always remember that some driver might hook your interrupt, so you must be sure of what you are running -or might run- at r0.

Good luck -and don't bet your life on Windows please. You would be a killer.

Hero
September 16th, 2006, 13:37
Hi
Is there anybody who seen anything for reprogramming APIC?I don't think that somebody can do it easily even for advanced programmer...
In addition what is the best OS for developing realtime systems?I mean best one that has suitable tools for developing applications too.

sincerely yours

Opcode
September 17th, 2006, 10:19
Hi Hero,

Take a look in this interesting article:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnxpembed/html/hardrealtime.asp

Regards,
Opc0de

Hero
September 17th, 2006, 12:34
Quote:
[Originally Posted by Opcode]Take a look in this interesting article:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnxpembed/html/hardrealtime.asp

Thanks very much.
The performance comparison is really intersting....

Regards