What Is Starvation In OS? Definition, Causes And Solution

In an operating system, starvation can happen when a process or thread is unable to advance or complete its work because of a shortage of resources. This problem mostly occurs in priority-based scheduling systems, where requests with higher priorities are handled first while requests with lower priorities could take longer to handle.

In densely loaded computer systems, a steady stream of high-priority activities can starve low-priority processes by preventing them from getting the resources they require. The concept of starvation in operating systems, its causes, and potential solutions will all be covered in this article.

What Is Starvation In OS?

Starvation is a resource management problem where a process does not get the resources it needs for a long network bandwidth because the resources are being allocated to other processes. Or, a condition where a process does not get the resources it needs for a long span of time because the resources are being allocated to other processes.

Starvation in operating system occurs generally in a priority-based scheduling system where higher-priority task requests get processed first. Thus a request with the least priority may never be processed.

Since the low-priority process does not interact with anything, it becomes impossible for starvation to cause a deadlock. It is thus, a fail-safe method to get out of a deadlock - making it much more important to understand how it affects the system as a whole.

Starvation In OS: Common Causes

Here are some causes of starvation in operating system:

Insufficient Resources: Starvation can occur if there aren't enough resources (e.g., CPU time, memory, I/O devices) to meet the demands of all processes, causing lower-priority processes to wait indefinitely.
Random Process Selection: If the system uses a random process selection for resource allocation, some processes may be left waiting for a long time due to the non-selection, leading to starvation.
Faulty Resource Allocation: Poor or biased resource allocation strategies (e.g., continuously favoring higher-priority tasks) can prevent certain processes from obtaining the resources they need, resulting in starvation.

Example Of Starvation In OS

In the above example, process P2 is having the highest priority, and process P1 is having the lowest priority. In general, we have a number of processes that are ready for execution. As time passes, if only those processes come in the CPU time that have a higher priority than process P1, then process P1 will keep on waiting for its turn for CPU time allocation. But, it will never get CPU - because all the other processes have a higher priority range than P1. This is called starvation.

What Is Deadlock?

A deadlock occurs when many processes in an operating system are unable to go forward because one process is holding a resource while waiting for a resource that is being held by another process. This creates a circular dependency, where none of the processes can make progress, leading to a system deadlock.

Necessary Conditions For Deadlock:

A deadlock occurs when the following four conditions hold simultaneously:

Mutual Exclusion: Resources are non-shareable and can only be held by one process at a time.
Hold and Wait: A process is holding at least one resource and waiting for additional resources held by other processes.
No Preemption: Resources cannot be forcibly taken from a process; they must be released voluntarily.
Circular Wait: A set of processes are waiting for each other in a circular chain, creating a deadlock.

Difference Between Deadlock And Starvation in OS

Let us discuss deadlock vs. starvation with the help of the comparison table below:

Aspect	Deadlock	Starvation
Definition	A situation where multiple processes are stuck because each is waiting for a resource held by another process, creating a circular wait.	A condition where a process is unable to obtain the required resources to execute because higher-priority tasks are continuously given preference.
Cause	Occurs due to circular dependency, where processes hold resources while waiting for others.	Occurs in priority-based scheduling when low-priority tasks are indefinitely delayed by higher-priority tasks.
Resource Allocation	Processes hold onto resources while waiting for others, causing a deadlock.	Resources are continuously allocated to other processes, depriving the low-priority process.
Conditions Required	Mutual Exclusion, Hold and Wait, No Preemption, and Circular Wait.	Biased scheduling where low-priority processes are postponed indefinitely.
Process Execution	No process can proceed because they are all waiting for each other.	Low-priority processes can never execute or have long delays because higher-priority processes dominate resources.
Prevention/Resolution	Deadlock prevention strategies like resource allocation ordering, avoiding circular waits, or deadlock detection and recovery.	Can be avoided by using aging techniques, where the priority of a process gradually increases over time to prevent starvation.
Outcome	The system becomes stuck, and none of the involved processes can progress.	Low-priority processes may experience significant delays or never execute, but the system itself remains functional.
Impact on System	Leads to system-wide freeze for the involved processes.	Affects the progress of specific low-priority processes, but the overall system may continue functioning.
Relation to Scheduling	Not directly related to scheduling policies but to resource allocation patterns.	Primarily a result of priority-based scheduling algorithm.
Example	Two processes each holding a resource while waiting for the other's resource, creating a deadlock.	A low-priority process waiting indefinitely for CPU time because higher-priority processes keep taking precedence.

Solutions To Starvation In OS

Here are some commonly used techniques and solutions to help solve the starvation in operating systems:

Technique 1: Aging In OS

It is a technique to avoid starvation in a scheduling system. It works by adding an aging factor to the priority of each process request. The aging factor must increase the request priority as time passes and must ensure that a request will eventually be the highest priority request (after it has waited long enough).

It can also be understood as a condition that is used to reduce starvation of low-priority tasks. It is a process that gradually increases the priority of critical tasks depending on the waiting process time. It ensures that jobs in the lower priority level queues will eventually complete their execution.
Aging is used to ensure that jobs with lower priority will eventually complete their execution. This method can be used to reduce the starvation of low-priority tasks.
There are many ways to implement aging, but all have the same principle that the priority of a process should increase as it waits in the ready priority queue. The increase in priority may or may not be equal to the waiting time of the process.

For Example: The priority of a process increases as it waits in the ready queue. For example, if a process starts with a priority of 85, after a specified time (e.g., every 10ms), its priority might be increased (e.g., reduced by 1 each time). As a result, the process's priority will eventually become high enough to be selected for execution.

Technique 2: Priority Scheduling

This scheduling method involves assigning priorities to processes and scheduling them based on these priorities. However, the specifics of how priorities are assigned can vary:

Internal Priorities: Assigned based on factors like memory requirements, execution time limits, or I/O and CPU burst ratios.
External Priorities: Set based on external criteria such as the importance of the process or resource usage costs.

Types of Priority Scheduling:

Preemptive Priority Scheduling: If the new process that arrived at the ready priority queue has a higher priority than the currently running process, the CPU is preempted. This means the processing of the current process is stopped and the incoming new process with higher priority gets the CPU for its execution.
Non-Preemptive Priority Scheduling: In the case of non-preemptive priority scheduling algorithm, if a new process arrives with a higher priority than the current running process, the incoming process is put at the head of the ready queue. This means after the execution of the current process, it will be processed.

Conclusion

Starvation in operating systems is a critical issue that arises when processes are unable to acquire the necessary resources due to the dominance of higher-priority tasks. While it is mostly associated with priority-based scheduling, it can severely impact system performance, causing delays and unresponsiveness for lower-priority processes.

Techniques like aging and fair resource allocation policies are essential to prevent starvation, ensuring that all processes receive the attention they need in a balanced and efficient manner. Addressing starvation not only improves system fairness but also enhances the overall user experience by ensuring that no task is left waiting indefinitely.

Frequently Asked Questions

Q. Name the different types of operating systems.

The different types of operating systems are:

Batch Operating System
Time-Sharing or Multitasking Operating System
Distributed Operating System
Network Operating System
Real-Time Operating System
Mobile Operating System

Q. What is meant by CPU scheduler?

A CPU scheduler is an element of an operating system that controls how programs or threads are executed on a CPU allocation. Its primary responsibility is to decide how operations should be carried out, taking into account a variety of parameters like CPU use, throughput, turnaround time, waiting time, and reaction time.

Q. What is starvation in OS?

When a process in an operating system is starved of the resources it requires for an extended period of time because those resources are being assigned to other processes, it is referred to as starvation. This issue primarily arises in a priority-based scheduling system where requests with high priority processes are executed first, and those with low priority take longer to process. Starvation can lead to several problems, such as reduced system responsiveness, violation of response time guarantees, and even system failure.

Q. Describe the concept of priority aging.

Operating systems employ aging as a scheduling technique to prevent starvation, a resource management issue when a process goes for a lengthy period of time without the resources it requires because those resource for execution are being given to other processes. In priority aging, as a process waits in the system, its priority steadily rises, guaranteeing fair resource distribution for all processes. The idea of priority aging is founded on the idea that a process' priority should rise while it waits in the ready queue.

Q. Define deadlock.

When two or more processes become stuck in an operating system and none of them can move forward because one process is holding a resource and waiting process for another resource that is being held by another process, the starvation situation is known as a deadlock. Deadlock can happen in distributed systems, parallel computing, and multiprocessing systems because these systems frequently employ software or hardware locks to arbitrate shared resources and implement process synchronization.

Q. What role does resource allocation policy play?

Resource allocation policies greatly influence the management of starvation in operating systems. A fair and efficient resource allocation method may prevent starvation by ensuring that all processes and threads have access to the resources they need. To prevent resource starvation, the strategy should take into consideration variables like importance, aging, and even resource allocation.

Q. What is disc starvation?

When a process or program is unable to access or use the disc resources it needs, it is referred to as disk space starvation in an operating system. This might be the result of a number of factors, such as improper resource management, excessive disc usage by other programs, ineffective disc scheduling algorithms, or disc failures.

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Shreeya Thakur

Sr. Associate Content Writer at Unstop

I am a biotechnologist-turned-content writer and try to add an element of science in my writings wherever possible. Apart from writing, I like to cook, read and travel.

What Is Starvation In OS? Definition, Causes And Solution