Skip to main content

Replacement of Page in O/S

 The number of frames allocated to a process can also dynamically change depending on whether you have used global replacement or local replacement for replacing page in case of page fault.

1. Local replacement :- 
   when a process needs a page which is not in the memory, it can bring in the new page and allocate it a frame from its own set of allocated frames only.

Advantage :- 
  The pages in the memory for a particular process and the page fault ratio nis affacted by the paging behaviour of only that process.

Disadvantage :-
   In local replacement the number of frames allocated to a process does not change so a low priority process may hender a high priority process by not making available to the high priority process its frames.

2. Global replacement :-
     When a process needs a page which is not in the memory, it can bring in the new frame and allocate it a frame from the set of all frames, even if that frame is currently allocated to some other processes. i.e one process can take a frame from other.

Advantage :-
   Does not hinder the performance of process and hence results in greater system throughput.

Disadvantage :-
  The page fault ratio of a process can not be sololy controlled by the process itself. The page in the memory for a process depends on the paging behaviour of other processes as well.


Share, Follow and please comment if you find anything incorrect or to share more information about the topic discussed above.

Labels:

Comments

Post a Comment

Please comment.

Popular posts from this blog

Process Scheduling And Types of Process Schedular :-

        ⇰ PROCESS SCHEDULING Process Scheduling  is a task  of Operating System that schedules processes of different states like new, ready, waiting, terminated  and running.This scheduling helps in allocation of CPU time for each process, and Operating System allocates the CPU time for each procss. And the process scheduling plays important role to keep the CPU busy all the time.  ⏩   Followings are some objectives of Process Scheduling :-  i > To increase the amount of users within acceptable response times.  ii > To maintain the balance between response and utilization of system. iii > To decrease the enforce priorities and  give reference to the processes holding the key resources.      ⇰  PROCESS SCHEDULAR A scheduler carries out the pro cess scheduling work. Schedulers are often implemented so they keep all computer resources busy and  allows multiple users to shar...
8 comments
Read more

Semaphores In Process Synchronization

   ⇰  Semaphores :-   Semaphore is actually a method or tool to prevent race condition. Race condition can cause loss of data or even deadlock situation. For prevention from these conditions, the semaphore is one of the method.  Semaphore was proposed by Dijkstra in 1965. Simaphore    is a very significant technique to manage concurrent processes.  Semaphore is useful tool in the prevention of race condition. But the use of semaphore never means a guarantee that a program is free from these problems.     Semaphore is an integer variable which is used in mutual exclusive manner by various concurrent cooperative processes in order to acheive synchronization. Hence semaphore is one of the way to achieve synchronization.  Semaphore is basically  a variable which is non-negative and shared between threads. This variable is used to solve the critical section problem and to achieve process synchronization in the multiprocess...
Post a Comment
Read more

DeadLock In Operating System

      ⇰  DEADLOCK :- As we know in a multiprogramming environment several processes may compete for a finite number of resources. If a process requests resources and if the resources are not available at that time, the process enters a state called  waiting state. Sometimes, a waiting process is never again able to change state or never out from waiting state, because the resources it has requested are held by or taken by other waiting processes before this process.This situation is called a Deadlock.     ⇰  DEADLOCK CHARACTERIZATION:- In a deadlock processes never finish executing and system resources are tied up  and also  preventing other jobs from starting. Here are some features that characterize deadlocks. A deadlock situation can arrive if the following four conditions hold simultaneously in any operating system :- 1. Mutual exclusion :- A process must hold at least one resource in a nonsharable mode so tha...
3 comments
Read more