fbpx

Os signaling | Computer Science homework help

 

In this project, we are to simulate a time-sharing system by using signals and timers. The data structure and worker thread have been well implemented with semaphore. You will focus on implementing the scheduling algorithm (Round Robin). Assuming we can not change actual “time slices” in OS we use interval timers to model it.  The scheduler is installed with an interval timer. The timer starts ticking when the scheduler picks a thread to use the CPU which in turn signals the thread when its time slice is finished thus allowing the scheduler to pick another thread and so on. When a thread has completely finished its work it leaves the scheduler to allow a waiting thread to enter. Please note that in this project, only the timer and scheduler send signals. The threads passively handle the signals without signaling back to the scheduler.

The goal of this project is to help you understand (1) how signals and timers work, and (2) how to evaluate the performance of your program. (3) understand how the POSIX:TMR interval timer works. You will first implement the time-sharing system using timers and signals. Then, you will evaluate the overall performance of your program by keeping track of how long each thread is idle, running, etc.

The program takes a number of arguments. Arg1 determines the number of jobs

(threads in our implementation) created; arg2 specifies the queue size of the

scheduler. Arg3 through argN gives the duration (the required time slices to

complete a job) of each job. Hence if we create 2 jobs, we should supply arg3

and arg4 for the required duration. You can assume that the autograder will

always supply the correct number of arguments and hence you do not have to

detect invalid input.

The program will use these four signals:

SIGALRM: sent by the timer to the scheduler, to indicate another time

 quantum has passed.

SIGUSR1: sent by the scheduler to a worker, to tell it to suspend.

SIGUSR2: sent by the scheduler to a suspended worker, to tell it to resume.

SIGTERM: sent by the scheduler to a worker, to tell it to cancel.

All code that does this will be in scheduler.c.  

Part I:Modify the scheduler code

———————————————–

The start code uses the scheduler thread to setup the timer and handle the scheduling for the

system. The scheduler handles the SIGALRM events that come from the timer, and

sends out signals to the worker threads.

The starting code has initialized the scheduler with a POSIX:TMR interval timer in init_sched_queue() function in scheduler.c. CLOCK_REALTIME is used in timer_create().

The timer will be stored in the global variable “timer”, which will be started

in scheduler_run().

sigaction() is used in setup_sig_handlers() to install signal handlers for

SIGALRM, SIGUSR1, and SIGTERM. SIGALRM triggers timer_handler(), SIGUSR1

triggers suspend_thread(), and SIGTERM triggers cancel_thread(). Notice no handler is installed for SIGUSR2; this signal will be handled differently, in worker.c which handles the signals from the scheduler.

start_worker() in worker.c immediately suspends the thread, waiting for a resume signal from the scheduler ((1) block SIGUSR2 and SIGALRM, and (2) unblock SIGUSR1

and SIGTERM). sigwait() is used in suspend_thread() to force the thread to suspend itself based on the SIGUSR1 signal and wait for a resume signal (SIGUSR2).

Step 1. (5 pt)

In the scheduler_run() function, start the timer. Use timer_settime().  The

time quantum (2 second) is given in scheduler.h. The timer should go off

repeatedly at regular intervals defined by the timer quantum.

In Round-Robin, whenever the timer goes off, the scheduler suspends the

currently running thread, and tells the next thread to resume its operations

using signals. These steps are listed in timer_handler(), which is called every

time the timer goes off.  In this implementation, the timer handler makes use of

suspend_worker() and resume_worker() to accomplush these steps.

Step 2. (5 pt)

Complete the suspend_worker() function.  First, update the info->quanta value.

This is the number of quanta that remain for this thread to execute.  It is

initialized to the value passed on the command line, and decreases as the thread

executes.  If there is any more work for this worker to do, send it a signal to

suspend, and update the scheduler queue. Otherwise, cancel the thread.

Step 3. (5 pt)

Complete the cancel_worker() function by sending the appropriate signal to the

thread, telling it to kill itself.

Step 4. (5 pt)

Complete the resume_worker() function by sending the appropriate signal to the

thread, telling it to resume execution.

Part II:Modify the evaluation code

————————————————–

This program keeps track of run time, and wait time. Each thread saves these

two values regarding its own execution in its thread_info_t.  Tracking these

values requires also knowing the last time the thread suspended or resumed.

Therefore, these two values are also kept in thread_info_t.  See scheduler.h.

You will implement the functions that calculate run time and

wait time. When the program is done, it will collect all these values, and print out the total and average wait time and run time. For your convenience, you are given a function

time_difference() to compute the difference between two times in microseconds.

Step 5. (5 pt)

Modify create_workers() to initialize the various time variables.

Step 6. (5 pt)

Implement update_run_time().  This is called by suspend_worker().

Step 7. (5 pt)

Implement update_wait_time().  This is called by resume_worker().

Step 8. (15 pt)

Test your code with 4 worker threads with queue size 2. You can set quanta yourself. Your result should show the statistics at the last lines.

Output:

Here is an example of program output, once the program is complete:

Sample Output

Sample Output Part 2

Tips:

  1. Make file is provided.
  2. You will use these functions (not limited to):

 pthread_kill

 timer_settime

 clock_gettime

Paper Writing Center
Calculate your paper price
Pages (550 words)
Approximate price: -

Why Work with Us

Top Quality and Well-Researched Papers

We always make sure that writers follow all your instructions precisely. You can choose your academic level: high school, college/university or professional, and we will assign a writer who has a respective degree.

Professional and Experienced Academic Writers

We have a team of professional writers with experience in academic and business writing. Many are native speakers and able to perform any task for which you need help.

Free Unlimited Revisions

If you think we missed something, send your order for a free revision. You have 10 days to submit the order for review after you have received the final document. You can do this yourself after logging into your personal account or by contacting our support.

Prompt Delivery and 100% Money-Back-Guarantee

All papers are always delivered on time. In case we need more time to master your paper, we may contact you regarding the deadline extension. In case you cannot provide us with more time, a 100% refund is guaranteed.

Original & Confidential

We use several writing tools checks to ensure that all documents you receive are free from plagiarism. Our editors carefully review all quotations in the text. We also promise maximum confidentiality in all of our services.

24/7 Customer Support

Our support agents are available 24 hours a day 7 days a week and committed to providing you with the best customer experience. Get in touch whenever you need any assistance.

Try it now!

Calculate the price of your order

Total price:
$0.00

How it works?

Follow these simple steps to get your paper done

Place your order

Fill in the order form and provide all details of your assignment.

Proceed with the payment

Choose the payment system that suits you most.

Receive the final file

Once your paper is ready, we will email it to you.

Our Services

No need to work on your paper at night. Sleep tight, we will cover your back. We offer all kinds of writing services.

Essays

Essay Writing Service

No matter what kind of academic paper you need and how urgent you need it, you are welcome to choose your academic level and the type of your paper at an affordable price. We take care of all your paper needs and give a 24/7 customer care support system.

Admissions

Admission Essays & Business Writing Help

An admission essay is an essay or other written statement by a candidate, often a potential student enrolling in a college, university, or graduate school. You can be rest assurred that through our service we will write the best admission essay for you.

Reviews

Editing Support

Our academic writers and editors make the necessary changes to your paper so that it is polished. We also format your document by correctly quoting the sources and creating reference lists in the formats APA, Harvard, MLA, Chicago / Turabian.

Reviews

Revision Support

If you think your paper could be improved, you can request a review. In this case, your paper will be checked by the writer or assigned to an editor. You can use this option as many times as you see fit. This is free because we want you to be completely satisfied with the service offered.