FIT1047 Lecture Notes - Lecture 6: Virtualization, Process State, Virtual Memory
4 Aug 2018
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A level of abstraction between hardware and software. Virtualisation: looks like each process has exclusive access to hardware system calls give access to os (file system, network, memory) cooperative vs. preemptive multitasking. They have hundreds of processes running at any point in time. Protect users from buggy code or malicious. Provide virtual form of each physical resource for each process. Code as if your program has the entire cpu to itself, and a large, contiguous memory just for itself. The part of the os that implements this is called a kernel. Only a limited subset of instruction can be used. Cpu jumps to special code and return to running program. Context switch makes sure program can continue as if no interrupt happened. Os regains control when user mode process makes a system call. Os then checks whether to switch from process a to b. Order processes by their length, shortest ones first. We don"t know how long processes will take.
