Re: Why is Linux not RTOS?

[Mark Hounschell <markh@compro.net>]

sandeep lahane wrote:
> On 4/5/07, Raseel Bhagat <raseelbhagat@gmail.com> wrote:
>> Hi Sandeep,
>>
>> On 4/5/07, sandeep lahane <sandeep.lahane@gmail.com> wrote:
>>
>> >They have a paravirtualization based approach using which
>> > guest OSes like RTOS or other rich OSes can be run simultaneously on
>> > an embedded platform. These guest OSes can communicate using inter OS
>> > communication mechanisms. They are partitioning resources which can be
>> > partitioned like system RAM and resources like CPU, MMU and interrupt
>> > controller are virtualized since they can't be partitioned. So
>> > basically, what they are doing is almost totally irrelevant with this
>> > question, since they are not trying to make Linux a RTOS, rather they
>> > are making Linux and other guest OSes co-exist with RTOSes
>> > simultaneously. Please CMIIW.
>> >
>>
>> I completely concur with you. And it makes lot of sense too.
>> For example RTLinux (Real time Linux) from FSMLabs is another such
>> approach.
>> They have a micro-kernel , which is basically a core real tie\me
>> kernel, which sits on top of the vanilla linux kernel. This way, all
>> the real time tasks are handled by the Microkernel during whcih time
>> Linux kernel runs as an idle process. Only when no RT tasks are
>> present, the vanilla Linux kernel executes all the non-RT tasks.
>> This way, RT behaviour is accomplished without having to modify the
>> core Linux kernel.
>>
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>>
> 
> Yes, may be the poster is looking for RTLinux kind of thing.

The vanilla Linux kernel can and is already being used in RT environments.
A dual processor box when configured properly can provide a very
deterministic env for a properly written RT application. The trick is to
realize that the 'box' must be dedicated to that application and that application
alone.

With Ingos work in progress at http://people.redhat.com/mingo/realtime-preempt/
that is becoming of less importance however.

Mark
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