Operating System [3i Infotech Placement]: Sample Questions 54 - 55 of 81

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Question 54

Operating System
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Describe in Detail

Essay▾

Difference between the fork () and vfork () system call?

Explanation

Difference between the Fork () and Vfork ()
fork ()vfork ()
Separate address space of child process and parent.Same address space of child process and parent process.
Parent and child process execute simultaneously.Parent process remains suspended till child process completes its execution.
If the child process alters any page in the address space, it is invisible to the parent process as the address space are separateIf child process alters any page in the address space, it is visible to the parent process as they share the same address space.
fork () uses copy-on-write as an alternative where the parent and child share same pages until any one of them modifies the shared page.vfork () does not use copy-on-write.

Question 55

Operating System
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Describe in Detail

Essay▾

What is the working set of a process?

Explanation

Understanding of the Working Set Policy
  • Working set is the approximation of the set of pages that the process will access in the future and more specifically is indication of pages to be kept in main memory to allow smooth execution of process without page faults.
  • The window of the working set of a process is the total number of pages the process has referred recently.
  • The working set information W at time t is the collection of information referred by the process during the process time interval () .
  • The units of information in question are considered memory pages.
  • It determines if there is enough RAM in the system.
  • If working set is smaller than RAM data the program frequently accesses is always in memory.

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