Questions and Answers of Operating Systems Internals And Design Principles

Consider a memory-management system based on paging. The total size of the physical memory is 2 GB, laid out over pages of size 8 KB. The logical address space of each process has been limited to 256
How does the use of virtual memory improve system utilization?
Which considerations determine the size of a page?
What is demand paging?
What are the drawbacks of using either only a precleaning policy or only a demand cleaning policy?
A system has a total of 128 frames. There are 4 processes in the system with the following memory requirements:p1 : 45 p2 : 75 p3 : 33 p4 : 135Using the following allocation methods, compute the
Consider the following sequence of page references:A, B, B, C, A, E, D, B, D, E, A, C, E, B, A, C, A, F, D, F and consider that a working set strategy is used for page replacement. What will the
How is processor scheduling done in the batch portion of an OS?
Suppose the virtual space accessed by memory is 6 GB, the page size is 8 KB, and each page table entry is 6 bytes. Compute the number of virtual pages that is implied. Also, compute the space
How is a page fault trap dealt with?
What is the main function of a dispatcher? Give some examples of events when it is invoked.
What scheduling criteria affect the performance of a system?
Consider that a uniprocessor system has n processes to be scheduled. If only non-preemptive scheduling algorithms are allowed, can you determine the maximum number of possible schedules in terms of n?
Identify the advantages and disadvantages of preemptive scheduling.
If purely priority-based scheduling is used in a system, what are the problems that the system will face?
Briefly define FCFS scheduling.
Briefly define round-robin scheduling.
Briefly define shortest-process-next scheduling.
Briefly define shortest-remaining-time scheduling.
Briefly define highest-response-ratio-next scheduling.
Consider a variation of round robin scheduling, say NRR scheduling. In NRR scheduling, each process can have its own time quantum, q. The value of q starts out at 40ms and decreases by 10ms each time
Which type of process is generally favored by a multilevel feedback queueing scheduler— a processor-bound process, or an I/O-bound process? Briefly explain why.
A variation of preemptive priority scheduling has dynamically changing priorities. A new process is assigned a priority 0. While a process is in the ready queue, its priority changes at the rate of
What grain size of parallelism is appropriate for a multiprogram med uniprocessor?
For which kinds of applications is gang scheduling of threads most useful?
Discuss the concept of dynamic scheduling.
What is priority inversion? What is unbounded priority inversion?
Suppose that an application has three threads T1, T2 and T3 having decreasing priority. Give a scenario that may cause unbounded priority inversion.
What is the difference between a file and a database?
In a hashed file organization, the division method is used to compute the hash address of a record. This method can be stated as follows:Choose a large prime number m which is close to the number of
What are some advantages and disadvantages of sequential file organization?
An alternative algorithm for insertion into a B-tree is the following: As the insertion algorithm travels down the tree, each full node that is encountered is immediately split, even though it may
Both the search and the insertion time for a B-tree are a function of the height of the tree. We would like to develop a measure of the worst-case search or insertion time. Consider a B-tree of
What is a pathname? State the two alternate ways to assign pathnames.
A sequential file is stored in a disk occupying 100 contiguous disk blocks. The disk has an average rotational delay of 2.5ms. The time taken to seek the head of the drive to the required cylinder is
What is the relationship between a pathname and a working directory?
Some operating systems have a tree–structured file system but limit the depth of the tree to some small number of levels. What effect does this limit have on users? How does this simplify file
Consider a hierarchical file system in which free disk space is kept in a free space list.a. Suppose the pointer to free space is lost. Can the system reconstruct the free space list?b. Suggest a
A sequential file has 10 million records. How does efficiency in access improve by using a two-level index? Assume 100 entries in a higher-level index and 10,000 entries in a lower-level index.
What is an embedded OS?
What is the target application for TinyOS?
What software comprises the TinyOS operating system?
What is the default scheduling discipline for TinyOS?
Briefly describe Type 1 and Type 2 virtualization.
Briefly describe container virtualization.
Explain the concept of ballooning.
Give a brief description of Java VM.
User “abram” owns a directory, “myDir,” containing an executable file called “myScript.sh” that he shares with users belonging to the group “myGroup” and others. User of “myGroup”
The UNIX command ls can be used to view the ownerships and permissions of a file. What will be the output of the command ls –l myStore | cut –d' '–f1 if myStore is a file with protection mode
What is the cloud computing reference architecture?
List and briefly define the key components of a cloud operating system.
What is the relationship between a cloud OS and IaaS?
Define the Internet of Things.
List and briefly define the principal components of an IoT-enabled thing.
What requirements should an IoT OS satisfy?
What do you understand by a distributed operating system?
Describe the round-robin scheduling technique.
Consider a system consisting of four processes and 9 instances of a single resource. The current state of the claim (C) and allocation (A) matrices is:Is the system in a safe state? If so, will it
Consider the following fragment of code on a Linux system.read_lock(&mr_rwlock);write_lock(&mr_rwlock);Where mr_rwlock is a reader–writer lock. What is the effect of this code?
Consider a variation of the dining philosophers problem where the number of philosophers is even. Can you devise a deadlock-free solution to the problem? Assume that all other requirements are like
At an instant, the resource allocation state in a system is as follows:4 processes P1–P44 resource types: R1–R4R1 (5 instances), R2 (3 instances), R3 (3 instances), R4 (3 instance)Snapshot at
Given the following state of a system:The system comprises of five processes and four resources.P1–P5 denotes the set of processes.R1–R4 denotes the set of resources.Total Existing
List some of the methods that may be adopted to recover from deadlocks.
Now consider another correct solution to the preceding problem:a. Explain how this program works and why it is correct.b. Does this solution differ from the preceding one in terms of the number of
Why can’t you disallow mutual exclusion in order to prevent deadlocks?
How can the hold-and-wait condition be prevented?
Consider the following program:a. Determine the proper lower bound and upper bound on the final value of the shared variable tally output by this concurrent program. Assume processes can execute at
In 1978, Dijkstra put forward the conjecture that there was no solution to the mutual exclusion problem avoiding starvation, applicable to an unknown but finite number of processes, using a finite
Consider the following processes P1 and P2 that update the value of the shared variables, x and y, as follows:Assume that the initial values of x and y are 2 and 3 respectively. P1 enters the system
Compare direct and indirect addressing with respect to message passing.
Which characteristics of monitors mark them as high-level synchronization tools?
Processes and threads provide a powerful structuring tool for implementing programs that would be much more complex as simple sequential programs. An earlier construct that is instructive to examine
What is the key difference between a mutex and a binary semaphore?
What is starvation with respect to concurrency control by mutual exclusion?
Consider Dekker’s algorithm written for an arbitrary number of processes by changing the statement executed when leaving the critical section fromEvaluate the algorithm when the number of
With respect to mutual exclusion using interrupt disablinga. Mention the requirements for this exclusion and state which of them are met when interrupts are disabled.b. Identify the problems
Demonstrate that the following software approaches to mutual exclusion do not depend on elementary mutual exclusion at the memory access level:a. The bakery algorithm.b. Peterson’s algorithm.
Demonstrate the correctness of Dekker’s algorithm.a. Show that mutual exclusion is enforced. flag[i] and ( not flag[1 – i] )b. Show that a process requiring access to its critical section
Explain the concept of threads in the case of the Clouds operating system.
List some advantages and disadvantages of using kernel level threads.
What are the advantages of using multithreading instead of multiple processes?
An application has 20% of code that is inherently serial. Theoretically, what will its maximum speedup be if it is run on a multicore system with four processors?
How is a thread different from a process?
Suppose that four interleaved processes are running in a system having start addresses 4050, 3200, 5000 and 6700. The traces of the individual processes are as follows:Find the interleaved traces of
The use of multithreading improves the overall efficiency and performance of the execution of an application or program. However, not all programs are suitable for multithreading. Can you give some
You have executed the following C program:main (){ int pid;pid = fork ();printf (“%d \n”, pid);}What are the possible outputs, assuming the fork succeeded?
What are the specialities of Process 0 and Process 1 in UNIX? Which command will you use to get information about the running processes in the system?
What is the purpose of the system call fork() in the UNIX operating system? Write a C routine to create a child process using the fork() system call. Incorporate an error check in your routine in
What are the elements of a process image?
What is process spawning?
Explain the concept of a process and mark its differences from a program.
What is time slicing?
A computer system boots and starts a user application when an interrupt occurs. In which modes does the operating system work in this scenario?
Suppose we have four jobs in a computer system, in the order JOB1, JOB2, JOB3 and JOB4. JOB1 requires 8 s of CPU time and 8 s of I/O time; JOB2 requires 4 s of CPU time and 14 s of disk time; JOB3
Suppose that a large file is being accessed by a computer memory system comprising of a cache and a main memory. The cache access time is 60 ns. Time to access main memory (including cache access) is
Consider a memory system with cache having the following parameters:Sc = 32 KB Cc = 0.1 cents/bytes TC = 10 nsSm = 256 MB Cm = 0.0001 cents/bytes Tm = 100 nsa. What was the total cost prior to
A DMA module is transferring characters to main memory from an external device transmitting at 10800 bits per second (bps). The processor can fetch instructions at the rate of 1 million instructions
What is the difference between a multiprocessor and a multicore system?
What are the trade-offs that determine the size of the cache memory?
What characteristics are observed while going up the memory hierarchy?

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