For a single-server queueing system, which of the following is FALSE? L Decreasing the variability of service times improves the performance of the system. II. Decreasing the variability of service times reduces the performance of the system. II. Increasing the variability of arrival times improves the performance of the system.

For a single-server queueing system, which of the following is FALSE? L Decreasing the variability of service times improves the performance of the system. II. Decreasing the variability of service times reduces the performance of the system. II. Increasing the variability of arrival times improves the performance of the system.

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Suppose that a disk drive has 5,000 cylinders, numbered 0 to 4,999. The drive is currently serving a request at cylinder 2,150, and the previous request was at cylinder 1,805. The queue of pending requests, in FIFO order, is: 2,069; 1,212; 2,296; 2,800; 544; 1,618; 356; 1,523; 4,965; 3,681 Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for each of the following disk-scheduling algorithms? a. FCFS b. SCAN c. C-SCAN d. LOOK e. C-LOOK
Suppose that an operating system supports two kinds of sequential processes: high-priority interactive processes, and low-priority non-interactive processes. The behavior of the high-priority processes is to alternate between periods of computation of duration Tc and periods of blocking (waiting for input) of duration Tb. The behavior of the low-priority processes is to compute constantly, with no blocking. The operating system’s scheduling policy is round-robin with a quantum q, where Tc < q. Scheduling decisions are made only when a quantum expires, or when the running process blocks. The scheduler selects a low-priority process to run only if no high-priority processes are ready. Suppose there is one high-priority process and one low-priority process in the system, and that both processes will run for a long time. For what fraction of the time does the low-priority process run?
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20 Suppose there are four processes (P1 - P4) with respective arrival times of 0, 10, 30, and 40, and burst times of 30, 20, 50, and 20 ms. These processes are scheduled from a ready queue on first come first served. The average waiting time is: None of the answers 30 25 20
A dispatcher of RTOS has the following three resources, A, B, and C. A has 7 instances, B has 5 instances, and C has 6 instances. At this time, the allocation, request and available map is shown in table Q1 below. a. Is this system in a safe state? Execute necessary algorithm to show your result. b. Is there a valid sequence that can work for this map? If so show it and state if it is the only one or not. c. Given the allocation table below, if PO requests 1 more resource from A and it is granted, will the system be in a safe state? d. Given the allocation table below, if C has a total of 5 slots that will leave C with only 1 available instance, will the system be in a safe state? If not, suggest a solution to overcome deadlock. Table Ql Allocation Requested Available C PO 1. 2. P1 P2 1. 1. P3 1. 2. 4 A HO 12
9. Learn to compute a shared K session key in the Diffie-Hellman algorithm if easy-to-calculate initial parameters are given.
8. Consider one disk with 400 cylinders, numbered 0 to 399. Assume the current position of head is at cylinder 130. The request queue is given as follows: 150, 40, 350, 100, 280 For each of the disk-scheduling algorithms given below, show (by plotting in the graphs below) the current position of head based on the disk arm movement to satisfy the above requests, and count the total distance (in cylinders) of the disk arm movement. a. First Come First Served (FCFS) 0 40 100 130 150 Total distance (disk arm movement) = b. Shortest Seek Time First (SSTF) 0 40 100 130 150 Total distance (disk arm movement) = c. LOOK - in the direction of increasing track number 0 40 100 130 150 Total distance (disk arm movement) = 280 280 280 350 350 350 399 399 399 d. Based on questions a-c, specify the best algorithm for the given case above. Also explain TWO (2) reasons why the disk scheduling algorithm important in disk management.
Consider the resource allocation graph shown below. Answer the following three sub- questions. D Write a set of processes. The answer is Write a set of resource types. The answer is Is the system in a deadlock? The answer is (Yes or No).
Subject: Operating Systems
Suppose there are four processes (P1 - P4) with respective arrival times of 0, 10, 30, and 40, and burst times of 30, 20, 50, and 20 ms. These processes are scheduled from a ready queue on first come first served. The average waiting time is?
2 Recall the various deadlock detection and prevention algorithms we've discussed in class and consider the following snapshot of a system with five processes (P10, P11, P12, P13, P14) and four resources (R1, R2, R3, R4). R1, R2, R3, and R4 have a total of 11, 13, 7, and 9 resources, respectively. There are no current outstanding queued unsatisfied requests. Table 1: Allocation Table 2: Max R3 R4 PID R.1 R2 R3 R4 PID R1 10 4 11 3 12 1 215 2 1 3 10 13 0 5 0 14 1 3012 4 11 12 012 1 13 1 14 231323 75524 R2 5 5 432300 36373 8 Is the system currently in a safe or unsafe state? If safe, provide the process execution order. If unsafe explain your answer.
8. Consider one disk with 400 cylinders, numbered 0 to 399. Assume the current position of head is at cylinder 130. The request queue is given as follows: 150, 40, 350, 100, 280 For each of the disk-scheduling algorithms given below, show (by plotting in the graphs below) the current position of head based on the disk arm movement to satisfy the above requests, and count the total distance (in cylinders) of the disk arm movement. a. First Come First Served (FCFS) 0 40 100 1.30 150 Total distance (disk am movement) = b. Shortest Seek Time First (SSTF) 40 100 130 150 0 Total distance (disk arm movement) = c. LOOK - in the direction of increasing track number 0 40 100 130 150 Total distance (disk arm movement) = 280 280 280 350 350 350 399 399 399