Starvation in an operating system is a problem where a process is perpetually denied access to a necessary resource, such as the CPU, memory, or an I/O device.
Understanding Starvation in Operating Systems
Based on the reference, starvation in OS is a problem that occurs when low-priority processes are indefinitely blocked from executing due to high-priority processes. This critical issue typically arises within scheduling systems, where the OS decides which process gets to run next. In environments using priority-based scheduling, certain low-priority processes are repeatedly overlooked in favor of high-priority ones.
Think of it like a busy doctor's office with an urgent care system. Patients with critical conditions (high priority) are seen immediately, potentially causing patients with minor ailments (low priority) who arrived much earlier to wait for an extremely long time, or even indefinitely if more high-priority cases keep arriving.
Why Starvation Happens
Starvation primarily occurs in scheduling algorithms, especially priority scheduling, because:
- Strict Priority: If the scheduler always picks the highest-priority ready process, and high-priority processes keep arriving, lower-priority processes may never get a chance to run.
- Lack of Preemption: If a high-priority process gets the CPU and runs for a very long time without yielding, it can hold up lower-priority processes even if they are ready.
- Resource Deadlock Components: Although distinct from deadlock, starvation can happen with resources if a process waits indefinitely for a resource that is always being allocated to others.
Consequences of Starvation
Ignoring starvation can lead to significant issues:
- Poor Performance: Critical background tasks or user applications might become unresponsive or fail to complete.
- System Instability: Essential low-priority system processes could starve, potentially leading to errors or crashes.
- Unfairness: It violates the principle of fairness in resource allocation, where all processes should eventually get a chance to execute.
Preventing Starvation (Solutions)
Operating systems employ various techniques to mitigate or prevent starvation:
- Aging: This is a common technique where the priority of a process is gradually increased the longer it waits in the ready queue. Eventually, a starving process's priority will become high enough to be scheduled.
- Round-Robin Scheduling: Algorithms like Round-Robin ensure that each process gets a small slice of CPU time in turn. This prevents any single process from dominating the CPU indefinitely, guaranteeing every process gets some execution time.
- Priority Inheritance: In systems with shared resources protected by mutexes, if a low-priority process holds a mutex needed by a high-priority process, the low-priority process's priority is temporarily boosted to that of the high-priority process. This ensures the low-priority process can finish and release the resource quickly, preventing the high-priority process from waiting indefinitely.
- Choosing Appropriate Algorithms: Selecting scheduling algorithms that are inherently less prone to starvation (like combinations of priority and round-robin) is crucial.
By implementing these strategies, operating systems can ensure that while high-priority tasks are handled promptly, low-priority tasks are not left waiting indefinitely, maintaining system fairness and stability.
