Skip to main content

Preemptive and non preemptive in operating system-computer world

 Preemptive and non preemptive 

Preemptive 

In preemptive Scheduling algorithm, the the running process is interested by the higher priority process. When a currently running  process finish execution, the priority of the ready state process is checked against that of the running process. If the priority of the ready process is higher, it is allocated to the CPU.

  1. A Scheduling discipline is primitive, if the CPU is taken away from the process after being allocated. 
  2. Cost of the preemptive scheduling is higher then non preemptive scheduling.
  3. Higher priority jobs are processed before the lower priority jobs. 

Non preemptive

In non preemptive Scheduling, the CPU has been allocated to a process, the process keeps the CPU until it release the CPU either by switching to the waiting state. This scheduling method is used by Microsoft Windows 3.x, window 95 introduced preemptive scheduling.

  1. A scheduling discipline is non preemptive, if the process has been given the CPU, the CPU cannot taken away from that process.
  2. It is not costly as compared to preemptive scheduling.
  3. Short jobs are made to wait by longer jobs. 

CPU scheduling decisions may take place under the following circumstances 

  1. When a process switches from the running state to the waiting state. 
  2. When a process switch from the running state to the ready state. 
  3. When a process which from the waiting state to the ready estate. 
  4. When a process terminates.  
  5. When scheduling takes place only under circumstance 1 and 4, we can say that the scheduling scheme is non preemptive or Co-operative, otherwise it is preemptive. 

Comments

Post a Comment

Popular posts from this blog

Single partition allocation, Multiple-partition allocation and Fixed Equal-size partitions in operating system-computer world

  Single partition allocation, Multiple-partition allocation and Fixed Equal-size partitions in operating system Single partition allocation In this scheme operating system is residing in law memory and user process are executing in higher memory. Advantages It is simple  It is easy to understand and use Disadvantages User job is limited to the size of available memory. It leads to poor Utilization of processor and memory. Multiple-partition allocation  It is the simplest method for allocating  memory is divided memory into several fixed size partitions. Fixed Equal-size partitions It divides the main memory Into equal number of fixed sized partitions, operating system occupies some fixed portion and remaining portion of main memory is available for user processes. Advantages It supports multi programming. A process whose size is less then or equal to the partitions size can be loaded into any available partition. Disadvantages If a program is big to fit in...
Post a Comment
Read more

Deadlock in operating system-computer world

  Deadlock in operating system-computer world Deadlock :  In a multi-programming environment, many process may complete for a minute number of resources. A process make a request for a resource and if the resource is not available at that time, the process enter In a waiting state. A waiting state process is never again-able to change state because the resource it has requested is held by other waiting process. This situation is called deadlock. So we can say that a process is said to be deadlock when it is waiting for an event or resources which will never occurs.   so we can say that in this situation none of the process gets executed  since the resource it needs, is held by some other process which is also waits for some other resource to be released.  Let's assume that there are three process P1, P2, p3 and three different resources R1, R2 and R3. R1 is assigned to p1, R2 is assigned to P2 and R3 is assigned to P3.   After somet...
9 comments
Read more

What is computer and its characteristics-computer world

  What is computer and its characteristics  Computer  :  Computer is an electronic data processing device, which accept and store data input, process the data and generates the output in a required format. computer is made up of integrated  parts (input, control, ALU, storage and output unit) All the part work together to process data so, we can say that a computer is a programmable electronic device accept row data as input and process it with  set of instruction to produce the result as output. Meaning of computer The word "computer" comes from the word "compute" which means to "calculate". The word computer is derived from the Latin word compute which means to calculate. Characteristics of computer Automatic : It is a automatic machine work by itself without human instruction. Speed :  A computer is a very fast devices. It can perform in a few second, the amount of work that a human being can do in an entire year.  Accuracy : In addition t...
1 comment
Read more