Convoy Effect in Scheduling Operating System (OS)

Convoy Effect in OS

Convoy effect is a phenomenon which occurs in First Come First Serve Scheduling Algorithm. Consider a process that is too large that occurs at the very start of the ready queue. Due to this long process other processes in the queue may starve for a very long time.

To understand this consider an example. Where a very long train is passing by and smaller cars and other vehicles may have to wait for a very very long time to pass by.

So, as in First Come First Serve Algorithm (FCFS), Jobs are executed as they come. As FCFS is a non-preemptive algorithm, meaning jobs can’t be preempted (stopped) if they have begun execution, so unless the process does not get finished other process can’t get CPU resources.

This situation can be likened to a convoy passing through the road. So, unless the convoy passes completely, other people can’t use the road.

Example with Image