Ticket Mechanism (Fair Resource Allocation)

The Ticket Mechanism is a scheduling technique used to fairly allocate resources among competing processes or users. In this system, each process or user is assigned a set number of "tickets," and the more tickets a process has, the higher its chances of being selected for resource access. This system ensures that processes get a fair opportunity to use resources based on their assigned tickets.


How the Ticket Mechanism Works:

Ticket Assignment: Each process is allocated a certain number of tickets. The number of tickets typically reflects the priority or the resource needs of the process—more tickets mean higher chances of selection.


Random Selection: When a resource is available, a random ticket is selected from the pool of tickets. The process that holds the selected ticket is granted access to the resource.


Fairness: Processes with more tickets are more likely to be chosen, but all processes have an equal chance, making the system fair and probabilistic.


Ticket Replenishment: In some implementations, tickets may be replenished periodically or based on the progress or behavior of processes (e.g., after a process finishes execution).


Example:

Consider three processes with different ticket counts:


P1 with 3 tickets

P2 with 5 tickets

P3 with 2 tickets

When the system decides to allocate a resource, it randomly selects a ticket. If the ticket corresponds to P1, then P1 gets the resource. If the ticket corresponds to P2, then P2 gets the resource, and so on. Since P2 has more tickets, it is more likely to be selected.


Advantages of the Ticket Mechanism:

- Fairness – The system fairly distributes resources according to the number of tickets each process holds.

- Prioritization – Processes needing more resources can be assigned more tickets.

- Flexibility – Ticket counts can be dynamically adjusted based on process behavior or system needs.


Disadvantages:

- Overhead – Random ticket selection and managing the tickets can introduce some computational overhead.

- Monopolization Risk – A process with many tickets may monopolize the resource, especially without limits on ticket counts.


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