Comparison of IOS and General Purpose OS like Linux

IOS Features
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The whole Operating System runs as a single process and kernel mode.
Monolithic
No Virtual Memory
Everything Runs in RAM
Cooperative Multitasking
Process relinquishes CPU on its own by calling --

Scheduler - Multilevel Priority queues
Four priority queues - CRITICAL, HIGH, NORMAL, LOW
Static priorities - decided at the time of creation of the process.
Can be changed thru cli/function call.
CPU HOG Message --- Trace from timer interrupt.....
Quantum 2 ms
Watchdog 2 minutes

I wrote function to print Stack trace from a interrupt handler---------.
---> Made some changes in timers - AVL tree and Timer wheel
---> Timers --- Timer wheeels


What are the advantages/disadvantages of cooperative multitasking
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Process does not have to worry about critical sections.
All processes have to be responsible. One process caught in loop will hog the CPU.






Is Cisco IOS an RTOS? Not really. Its is not hard real time system. It has
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No virtual memory
Priority based scheduling