The LCN is preemptive scheduling
policy and it always schedules the request that has consumed the least amount
of processor time of all requests existing in the system. Thus, the nature of
the job, whether CPU-bound or I/O-bound, does not influence its progress in the
system. All requests now make approximately equal progress in terms of the
processor time consumed by them and short jobs are guaranteed to finish ahead
of long requests. This policy also has the drawback of starving the long job of
CPU attention.
Short Time to Go (STG) or Shortest Remaining Time Next (SRTN) Scheduling
SRTN is the preemptive version of
SJN policy and is useful in time-sharing system. In SRTN, the process with the
smallest estimated run-time to completion is run next, including the new
arrivals. Thus in SRTN, a
running process may be preempted by a new process
with a shorter estimated run time. SRTN favours any job which is nearing
completion, irrespective of the CPU time already consumed by it. In SRTN, long
request have problems receiving service in early stage of their life in the
system.
NEXT: HRN Scheduling
Previous: RR scheduling
Index : Operating System
This blog is nice and very informative. I like this blog.
ReplyDeleteblog Please keep it up.