Correct Answer: A binary semaphore is one, which takes only 0 and 1 as values They are used to implement mutual exclusion and synchronize concurrent processes
2. Define latency, transfer and seek time with respect to disk I/O.
Correct Answer: Seek time is the time required to move the disk arm to the required track Rotational delay or latency is the time it takes for the beginning of the required sector to reach the head Sum of seek time (if any) and latency is the access time Time taken to actually transfer a span of data is transfer time
3. What are the typical elements of a process image?
Correct Answer: User data: Modifiable part of user space May include program data, user stack area, and programs that may be modified User program: The instructions to be executed System Stack: Each process has one or more LIFO stacks associated with it Used to store parameters and calling addresses for procedure and system calls Process control Block (PCB): Info needed by the OS to control processes
Correct Answer: Load Sharing: Processes are not assigned to a particular processor A global queue of threads is maintained Each processor, when idle, selects a thread from this queue Note that load balancing refers to a scheme where work is allocated to processors on a more permanent basis Gang Scheduling: A set of related threads is scheduled to run on a set of processors at the same time, on a 1-to-1 basis Closely related threads / processes may be scheduled this way to reduce synchronization blocking, and minimize process switching Group scheduling predated this strategy Dedicated processor assignment: Provides implicit scheduling defined by assignment of threads to processors For the duration of program execution, each program is allocated a set of processors equal in number to the number of threads in the program Processors are chosen from the available pool Dynamic scheduling: The number of thread in a program can be altered during the course of execution
7. What scheme does the Kernel in Unix System V follow while choosing a swap device among the multiple swap devices?
Correct Answer: The repeated execution of a loop of code while waiting for an event to occur is called busy-waiting The CPU is not engaged in any real productive activity during this period, and the process does not progress toward completion
9. Which among the following is not aprocess state in unix?