Midterm - Quiz 4

The major problem with priority scheduling algorithms is indefinite blocking, where a process that is ready to run but waiting for the CPU can be considered blocked. This can result in low-priority processes waiting indefinitely, which is known as starvation. In other words, starvation occurs when a process is unable to proceed or complete its execution due to being constantly overshadowed by higher-priority processes.

Throughput is a measure of work that indicates the number of processes completed per unit of time. In this context, if the CPU is busy executing processes, it means work is being done, and the number of processes completed can be used to measure the throughput. Therefore, the correct answer is throughput.

The statement is true because a multilevel queue scheduling algorithm indeed partitions the ready queue into separate queues. Each process is permanently assigned to one queue based on some property such as memory size, process priority, or process type. Each queue also has its own scheduling algorithm to determine the order in which processes are executed.

On operating systems that support threads, it is the kernel level that schedules threads, not processes. The kernel level is responsible for managing and allocating system resources, including CPU time, to different threads. Threads are lighter weight than processes and can be scheduled more efficiently, allowing for better multitasking and responsiveness in the operating system. By scheduling threads at the kernel level, the operating system can optimize resource allocation and improve overall system performance.

The correct answer is "PUSH MIGRATION". This approach to load balancing involves a specific task periodically checking the loads on each processor. If an imbalance is detected, the task evenly distributes the load by moving processes from overloaded processors to idle or less-busy processors. This process is known as "PUSH MIGRATION".

The dispatcher is responsible for giving control of the CPU to the process selected by the short-term scheduler. It is a module that handles the context switching and transfers control from the operating system to the selected process. The dispatcher ensures that the selected process is loaded into the CPU and begins execution, allowing it to utilize the CPU's resources.

Soft affinity refers to the operating system's policy of attempting to keep a process running on the same processor, but without guaranteeing that it will do so. In this case, the operating system will make an effort to keep a process on a single processor, but it is still possible for the process to migrate between processors. This can be advantageous in certain scenarios where a process may benefit from running on a specific processor, but does not necessarily require strict affinity to that processor.

Multicore processors may complicate scheduling issues because when a processor accesses memory, it often has to wait for the data to become available. This waiting time can be significant and is known as a memory stall. This can happen due to reasons like cache misses, where the data being accessed is not present in the cache memory. In such cases, the processor has to wait for the data to be fetched from the main memory, causing a delay in the execution of instructions.

Interrupt latency refers to the period of time from the arrival of an interrupt at the CPU to the start of the routine that services the interrupt. When an interrupt occurs, the operating system needs to finish executing the current instruction and identify the type of interrupt. It then saves the state of the current process before handling the interrupt using the specific interrupt service routine (ISR). This latency is the time it takes for the CPU to respond to an interrupt and start processing it.

Proportional share schedulers allocate a certain number of shares among all applications. Each application is then assigned a specific number of shares, denoted by "n", which ensures that it will receive a fraction of the total processor time equal to n/t. This allows for a fair distribution of resources among applications based on their assigned shares.

The correct answer is the SHORT TERM SCHEDULER. The short term scheduler is responsible for selecting one of the processes in the ready queue to be executed when the CPU is idle. This scheduler determines which process will run next and allocates CPU time to it. It makes decisions quickly and frequently, ensuring efficient utilization of the CPU and maintaining a balance between all the processes in the system.

The round-robin (RR) scheduling algorithm is designed for time-sharing systems, where multiple processes are executed in a cyclical manner. Each process is given a small unit of time called a time quantum or time slice. This time slice determines how long a process can run before it is preempted and another process is given a chance to execute. The use of time slices allows for fair allocation of CPU time among processes and prevents any single process from monopolizing the CPU for too long.

The multilevel feedback queue scheduling algorithm allows a process to move between queues based on the characteristics of their CPU bursts. This means that processes with similar CPU burst characteristics are grouped together in the same queue. By doing this, the algorithm aims to improve the overall efficiency of the scheduling process by ensuring that processes with similar behavior are treated in a similar manner.

The given explanation describes the First Come First Served (FCFS) scheduling algorithm. In FCFS, the processes are executed in the order they arrive in the ready queue. When a process enters the ready queue, its Process Control Block (PCB) is linked to the tail of the queue. When the CPU becomes available, the process at the head of the queue is allocated the CPU, and the running process is removed from the queue. This ensures that the processes are executed in the order they arrive, following the principle of "first come, first served."

Processor affinity refers to the ability of an operating system to bind a process to a specific processor or set of processors. It allows the operating system to schedule the process on the specified processor(s) consistently. However, processor affinity does not mean that a processor has an affinity for the process it is currently executing. The decision of which processor executes a process is typically determined by the operating system's scheduling algorithm. Therefore, the statement that a processor has affinity for the process it is currently executing is false.