Operating Systems Questions

Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.

Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.

Time taken for switching from one process to other is pure over head. Because the system does no useful work while switching. So one of the solutions is to go for threading when ever possible.

- Normal completion

- Time limit exceeded

- Memory unavailable

- Bounds violation

- Protection error

- Arithmetic error

- Time overrun

- I/O failure

- Invalid instruction

- Privileged instruction

- Data misuse

- Operator or OS intervention

- Parent termination.

Page swapping or page replacements are called page cannibalizing.

swapping

interactive user request

timing

parent process request

When a thread is created the threads does not require any new resources to execute the thread shares the resources like memory of the process to which they belong to. The benefit of code sharing is that it allows an application to have several different threads of activity all within the same address space. Whereas if a new process creation is very heavyweight because it always requires new address space to be created and even if they share the memory then the inter process communication is expensive when compared to the communication between the threads.

C2 level security provides for:

1.Discretionary Access Control

2.Identification and Authentication

3.Auditing

4.Resource reuse