Operating System MCQs

Progress requires the decision about the next entrant to involve only processes that currently wish to enter.
The selection cannot be postponed forever when the critical section is available.

Processor partitioning reserves groups of CPUs for selected applications, users, or service classes.
It can provide isolation, predictability, or performance control.

A critical section contains operations whose interleaving could corrupt shared state.
Synchronization ensures that incompatible executions do not overlap.

The entry section contains the synchronization steps used to acquire access to the critical section.
Only after successful entry may the process execute the protected code.

The exit section unlocks or signals that the process has left the critical section.
This allows another waiting process or thread to enter safely.

In symmetric multiprocessing, processors are peers that can schedule work from shared or per-CPU queues.
This improves flexibility but requires coordination over shared scheduling data.

Load balancing moves or assigns tasks so no processor is overloaded while another remains underused.
The policy must also consider migration cost and cache locality.

Push migration actively transfers work away from an overloaded processor.
The balancing mechanism initiates the movement rather than waiting for an idle CPU to request work.

Pull migration lets an underloaded or idle processor obtain work from a busier processor.
The receiving processor initiates the load-balancing action.

Soft affinity is a scheduling preference rather than an unbreakable restriction.
The scheduler may move the task when load balancing or other needs outweigh locality.

Hard affinity defines an explicit CPU set on which the thread is permitted to run.
The scheduler must respect that restriction when making placement decisions.

Non-uniform memory access systems have faster local memory and slower remote memory.
Placing a thread near its data can reduce memory latency and interconnect traffic.