Database System Concepts
Database System Concepts
7th Edition
ISBN: 9780078022159
Author: Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher: McGraw-Hill Education
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a)
Request Sequence: Allocate(D), Allocate(B), Allocate(F), Deallocate(D), Deallocate(F),
Allocate(G), Allocate(I)
First-fit
The best algorithm for this sequence of requests is:
The amount of internal fragmentation (in KB) for this algorithm is
Best-fit
First-fit
b)
Request Sequence: Allocate(C), Allocate(E), Allocate(D), Allocate(A), Deallocate(C),
Deallocate(D), Allocate(H), Allocate(F), Allocate(J)
Best-fit
The best algorithm for this sequence of requests is:
The amount of internal fragmentation (in KB) for this algorithm is
First-fit
Worst-fit
c)
Request Sequence: Allocate(I), Allocate(H), Allocate(G), Allocate(F), Allocate(D), Deallocate(I),
Deallocate(G), Deallocate(D), Allocate(K), Allocate(E), Allocate(G), Allocate(A)
Best-fit
Worst-fit
The best algorithm for this sequence of requests is:
The amount of internal fragmentation (in KB) for this algorithm is
Worst-fit
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Transcribed Image Text:a) Request Sequence: Allocate(D), Allocate(B), Allocate(F), Deallocate(D), Deallocate(F), Allocate(G), Allocate(I) First-fit The best algorithm for this sequence of requests is: The amount of internal fragmentation (in KB) for this algorithm is Best-fit First-fit b) Request Sequence: Allocate(C), Allocate(E), Allocate(D), Allocate(A), Deallocate(C), Deallocate(D), Allocate(H), Allocate(F), Allocate(J) Best-fit The best algorithm for this sequence of requests is: The amount of internal fragmentation (in KB) for this algorithm is First-fit Worst-fit c) Request Sequence: Allocate(I), Allocate(H), Allocate(G), Allocate(F), Allocate(D), Deallocate(I), Deallocate(G), Deallocate(D), Allocate(K), Allocate(E), Allocate(G), Allocate(A) Best-fit Worst-fit The best algorithm for this sequence of requests is: The amount of internal fragmentation (in KB) for this algorithm is Worst-fit
Process
ABCDEFGHI JK
Size (in KB) 4.27.2 2.5 4.5 3 2.7 1.5|2|3.62.2|1
Allocate(P) represents an allocation request by process P for the size shown in the above table
Deallocate(P) is used to indicate deallocating the memory allocated to process P
To represent memory, in square brackets, we use P to indicate a memory segment allocated to P and
we use an integer to indicate a contiguous free part of memory. For example, after the following
sequence of requests: Allocate(B), Allocate(G), Allocate(H), Deallocate(G) memory will look like
this:
B
8KB
We represent this memory by [B,2,H,4].
free H
2KB 2KB
For each of the following sequence of requests, apply the First-fit, Best-fit, and Worst-fit allocation
schemes. Assume that for each algorithm, you always start at the beginning of the list and if there are
multiple possible equal-size holes that can be selected by an algorithm, the first one is selected. Show
the following:
i. If all the requests can be satisfied, indicate the memory representation at the end of the sequence.
If a request cannot be satisfied by an algorithm, indicate which request is this and the memory
representation at this point. For example, consider adding the request Allocate(X) to the
previous example. The following are answer examples
If X is requesting 6 KB the answer will be:
[B,2,H,4] and Allocate(X) cannot be satisfied
If X is requesting 3 KB, the answer will be
[B,2,H,X,1]
free
4KB
ii. Which method is the best for this particular sequence, and the amount (in KB) of internal
fragmentation at the end of the sequence for this best method.
expand button
Transcribed Image Text:Process ABCDEFGHI JK Size (in KB) 4.27.2 2.5 4.5 3 2.7 1.5|2|3.62.2|1 Allocate(P) represents an allocation request by process P for the size shown in the above table Deallocate(P) is used to indicate deallocating the memory allocated to process P To represent memory, in square brackets, we use P to indicate a memory segment allocated to P and we use an integer to indicate a contiguous free part of memory. For example, after the following sequence of requests: Allocate(B), Allocate(G), Allocate(H), Deallocate(G) memory will look like this: B 8KB We represent this memory by [B,2,H,4]. free H 2KB 2KB For each of the following sequence of requests, apply the First-fit, Best-fit, and Worst-fit allocation schemes. Assume that for each algorithm, you always start at the beginning of the list and if there are multiple possible equal-size holes that can be selected by an algorithm, the first one is selected. Show the following: i. If all the requests can be satisfied, indicate the memory representation at the end of the sequence. If a request cannot be satisfied by an algorithm, indicate which request is this and the memory representation at this point. For example, consider adding the request Allocate(X) to the previous example. The following are answer examples If X is requesting 6 KB the answer will be: [B,2,H,4] and Allocate(X) cannot be satisfied If X is requesting 3 KB, the answer will be [B,2,H,X,1] free 4KB ii. Which method is the best for this particular sequence, and the amount (in KB) of internal fragmentation at the end of the sequence for this best method.
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