What are the main tasks of an operating system?
An OS controls the computer’s resources and provides base upon which applications can be written.
What is the difference between the extended machine and the resource manager?
- extended machine: easy to use hides technical details
- resource manager: provides allocation of processors, memory etc.
User Space
use functionality provided by the OS (normal processors) not the same rights to access memory/hardware as the OS
Kernel Space
unlimited access to all resources; kernel executes its services interaction with user space via system calls
Define Cooperative Scheduling.
different processes in parallel; processes must cooperate with scheduler processor cannot be taken from a process. E.g.: MacOS pre9; Windows 95/98/ME
What is Preemptive Scheduling?
In preemptive scheduling the processor can be forcibly taken from any running process in user and even kernel space. E.g.: LINUX; MacOS; Windows NT/XP/Vista/7
Which type of scheduling do RTS mostly use today?
RTS use mostly preemptive scheduling.
Name three requirements of Real Time Operating Systems (RTOS).
- stable around-the-clock operation;
- exact and predefined response times;
- parallel processes;
- multi-core and multi-CPU support;
- fast process-switching (lightweight process, real time interrupt handling
- support for I/O operations (dynamic binding to kernel)
- system API (e.g. POSIX)
Name three different types of latency.
- interrupt latency: time needed between interruption and execution
- scheduling latency: time between execution of last instruction of ISR and execution of process which state was changed due to the interruption
- context switch latency: time between execution of last instruction and the next process
What is the difference between monolithic kernel and microkernel?
- Monolithic (Linux; Windows): services (driver; file system; network stack) of the OS run in kernel space
- Microkernel (QNX; Symbian; OS X; PikeOS): basic functionality (Basic IPC; Virtual Memory; Scheduling) in kernel space other services in user space
QNX architecture
In QNX only a minimal set of services contained in the kernel space (only communication; threading and synchronization). OS services and device drivers run in user space.
Which company did develop VxWorks?
WindRiver / Intel.
Name an advantage and disadvantage of Linux.
- insufficient timer resolution, virtual memory (non-deterministic) and non-preemptive kernel
- easy development, portability and good hardware support —> RTLinux (add Hardware Abstraction Layer)
AUTOSAR
AUTOSAR is a successor of OSEK/VDX and aims to become an industry standard. It was developed by BMW; Bosch; Continental; DaimlerChrysler; VW; Siemens and consists out of a modular layered architecture with standardized interfaces.
TinyOS
- components connected via interfaces
- optimized for sensor networks
- no separate OS
- kernel or memory management -> single shared stack static memory allocation
- concurrency model: processes only interrupted by events not processes; FIFO
