P1L1 Flashcards
OS provides
abstractions
mechanisms
policies
Operating System is
a special piece of software that abstracts and arbitrates the use of a computer system
What does an operating system do?
hides hardware complexity
resource mgmt
provides isolation and protection
OS Abstractions
Process, thread, file, socket, memory page
OS Mechanisms
create, schedule, open, write, allocate
OS Policies
least recently used (lru), earliest deadline first (edf)
Separation of mechanisms and policies
implement flexible mechanisms to support many policies
Common case principle
Optimize for common case
User/Kernel Protection Boundary
user mode attempting to perform priv access causes trap and switches control
To make a system call
app must
- write args
- save relevant data at well-define location
- make system call
user/kernel transition cost
not cheap 50-100 ns
Basic OS services
process, file, device, memory, and storage mgmt
security
Types of OS
monolithic
modular
microkernel
monolithic OS
everything included
Modular OS
(Linux) Modular interface which supports loading a module indirection can impact performance and maintenance can be an issue The main elements of a modular operating system are a kernel and a set of dynamically loadable applications with their own discrete memory spaces.
