Before revision: For a single server system, Shortest Remaining Processing Time (SRPT) is a size-based policy that is optimal in the sense that, regardless of the job size distribution, it minimizes the number of jobs in the system at each point in time. However, one reason that size-based policies such as SRPT are rarely deployed in practice is that the exact processing times of jobs are usually not known to the scheduler.
After revision: For a single server system, Shortest Remaining Processing Time (SRPT) is a size-based policy .