Hi,
Why is Linux kernel considered a (hard) realtime OS? I already
Linux kernel is never considered a real time OS.
A real time OS should be predictable.The general linux kernel is not
predictable because of many reasons.
A few are it uses virtual memory. when there is virtual memory there will be
page swaps which are un predictable.
And the linux scheduler is not a deterministic one.
There is a scheduler project which provides a deternistic behaviour to the
scheduler.This scheduler is called O(1) scheduler.
This gives a constant scheduling latency. This is used in many embedded
linux to make it a real time OS. Ex: motavista
understand the basic reason is that the linux kernel does not
guarantee that a task will be completed on time. But I would
appreciate answers in terms of more of kernel jargons.
What stops us from classifying kernel as hard RTOS? Is it because at
An RTOS is just a facilitator to build Real time systems. A Real time system
developer should analyse a RTOS wether is will be useful for his system.
If some body is holding spin lock and making it non-preemptive its a bad
design. So even a RTOS linux has spin locks. Its the designer who should
take care.
times the kernel is non-preemptive (for e.g. while holding spinlocks)?
Has it got something to do with interrupt latency / scheduling latency
etc?
Is the behaviour of the kernel (when it is preemptive) similar to hard
real time OS ??
Thanks,
Rick
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