Basic CS-Operating System [3i Infotech Placement]: Sample Questions 74 - 75 of 89

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Question 74

Operating System
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Short Answer▾

What is meant by arm-stickiness?

Explanation

  • Arm stickiness is a phenomenon in I/O scheduling where the scheduling algorithm continues to service disk requests at or near the current sector preventing any seeking.
  • This is done out of order, to satisfy the nearby requests first.
  • However, this may cause arm-stickiness- the name derives from the arm controlling the seek head of the disk being struck to a particular part.
    • Processes having high access rate to one track of disk monopolize the device by continues access to the track.
    • Happens with most common device scheduling algorithm.
  • High-density multisurface disks are affected more.

Question 75

Operating System
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Short Answer▾

What is a binary semaphore? What is its use?

Explanation

State Diagram of Binary Semaphore
  • Binary semaphores are binary- can take only two values.
  • “1” might represent a process is in the critical section and other should wait, the other indicating the critical section is free.
  • Sometime easier to implement than counting semaphore.
  • Binary semaphore are used as mutex locks, to implement mutual exclusion and synchronize concurrent processes.

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