Operating System-Unix [3i Infotech Placement]: Sample Questions 29 - 30 of 78

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Question 29

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Describe in Detail

Essay▾

What do you mean by u-area (user area) or u-block?

Explanation

UNIX maintains the information about a process in two areas- process table and the u-area. U-area:

  • The user area of a process is located at the upper end of the process address space and accessible only when running in kernel mode.
  • Contains the private data that is manipulated only the kernel.
  • This is the local to the process; each process is allocated a u-area.
  • When a process is created it is the required small temporary memory to start execution.
  • Temporary private area used only by kernel to control and execute process.

Question 30

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Describe in Detail

Essay▾

What is page fault? it՚s types?

Explanation

Define Page Fault
  • Page fault handler is one of critical parts of code in the linux kernel.
  • It has major influence on memory subsystem՚s performance.
  • Each process is assigned to a memory chunk named as pages.
  • A process has a page table containing page table entries that point to the memory assigned to the process. They communicate to the CPU, the memory locations which valid for the process.
  • A page table that does not currently map to RAM, will result in page fault by CPU.

Two types of page fault:

Validity fault

  • Validity fault is the result of non setting of valid bits in main memory at the time of refererring a page.

Protection fault

  • Provides protection mechanism in response to access violation caused by running code.
Two Types of Page Fault

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