Lesson 2a Flashcards
protection
protect hardware from user and users from each other
performance
perform task quickly then get out of the way
flexibility
extensible. not one size fits all
scalability
performance increases if hardware resources increase
agility
adapting to change in application needs and/or other resource availability
responsiveness
reacting to external events
Monolithic structure
apps are in user space and each app is in its own address space. The OS, services and device drivers are all in one protected address space above the hardware
DOS like
Good Performance, Bad Protection. No protection between the application and the OS
Benefit of monolithic
Reduces performance loss by consolidation
Disadvantage of monolithic
No customization. For example a gamer might want input from a controller to be higher priority. Whereas someone computing primes would want the CPU to be highest priority.
What happens during page fault
find page frame, move from virtual to physical page frame, update the page table, resume process
Micro kernel based os
Each app in its own address space, each service in own address space, services at user level. kernel is a simple abstraction in the protected address space above the hardware. services talk to the kernel and other services using IPC.
Benefit of Microkernel
Customization. Can easily have apps access different file systems for example.
Initial perceived downside to Microkernel
More border crossing (kernel traps) then a Monolithic kernel.
Border Crossing
Change in locality (address space). User space system space.
