CMSC 421 - Homework 2 Solution
Spring 2006

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Q1. 

11 faults for LRU. The final set of pages in memory: {4, 2, 3, 0}

11 faults for FIFO. The final set of pages in memory: {0, 2, 3, 4}

11.4

This scheme will reduce internal fragmentation since the allocated
blocks can be tailored to be closer to required file sizes. The
additional requirement is the maintenance of additional free space
information in terms of larger blocks and their constituent
sub-blocks. 

12.2

a. The FCFS schedule is 143, 86, 1470, 913, 1774, 948, 1509, 1022,
1750, 130. 

b. The SSTF schedule is 143, 130, 86, 913, 948, 1022, 1470, 1509,
1750, 1774. 

c. The SCAN schedule is 143, 913, 948, 1022, 1470, 1509, 1750, 1774,
4999, 130, 86. 

d. The LOOK schedule is 143, 913, 948, 1022, 1470, 1509, 1750, 1774,
130, 86. 

e. The C-SCAN schedule is 143, 913, 948, 1022, 1470, 1509, 1750, 1774,
4999, 0, 86, 130. 

f. The C-LOOK schedule is 143, 913, 948, 1022, 1470, 1509, 1750, 1774,
86, 130.

14.5

Strength: Access priveleges are stored along with the object; thus,
it is easier to revoke or expand priveleges associated with that
object.

Weakness: Requires overhead in checking whether the requesting domain
has access rights for this object. Depending upon the number of
domains allowed, this can be time consuming.

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