On Thu, 03 Feb 2000, C Hanish Menon used an e-pen to say :
>Hi
>
>On Tue, 01 Feb 2000, you wrote:
>> Hi Folks,
>> I am looking out for a program which tests all the parameters of a kernel
>> and checks whether it works in a real time environment.
>> Regards
>> Khader
>>
>
>Well I have to check this a bit more for all possible answers regarding why
>standard linux may not be suitable for Realtime. Also I haven't looked into
>2.3.x kernels regarding these issues so I could be wrong.
>
>The 1st thing that comes to my mind is
> Kernel is single threaded: This _can_(For linux the way its done I am quiet
>sure) lead to linux not satisfying one of the main requirements of Real Time
>systems i.e _Predeterminable Timed Response_ or what ever one wants to call it.
Right on track Hanish !
Linux (Standard) is NOT a Real time kernel. Without going into
theories, lets look at it this way. Suppose you are reading data from the
serial port and suddenly there is a disk interrupt. The linux kernel
dumps whatever you are doing and runs to service the interrups which
might take an unknown amount of time. So deadline meetings are impossible.
This is NOT serviced /patched by 2.3.x and probably mot to be
done so in the foreseaable future. Linux is a time sharing OS with very
good average response characterisitics but very bad worst case response
times :( Balancing both is a tough job(Read : impossible)
To achieve real time efficiency on Linux , you have to
shift to stuuff like RTLinux (www.rtlinux.org/com) or RTAI (www.rtai.org)
or KURT ( oops : no know, search google). However, each has its serious
limitations. The best (and most expensive) solutions is to probably go in
for Customised RTOS like VxWorks etc.
Aside : VxWorks was the culprit which caused the fault aboard
MArs Pathfinder, so... ;)
Aside 2 : Do not even think of Win 9x /NT as RTOS.. they have
even worse-than-Linux(he he isn'yt that usual ?) RT characteristics than
Linux.
Regards
Shourya
_______________________________________________________________
Shourya Sarcar <[EMAIL PROTECTED]> <Tel:91-033-4710477>
Department of Computer Science and Engineering
Jadavpur University Calcutta, India 700 032
All the world's a stage..
And I am acting tonight
C - the difference : http://www.eskimo.com/~scs/C-faq/top.html
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