Make your simulation run faster, Computer Engineering

Assignment Help:

Ameliorating the mechanical delays of seeks and rottion are usually regardeed as major aspects of device drivers for disks. The simplest way for a disk device driver to service disk IO requests is First Come First Served. However, most disk driver software instead uses the "elevator algorithm". If there is no IO request pending, the first request is serviced. If, however, there is at least one request pending, then the disk arm has a direction of movement: inward or outward from the ddisk spindle. Two ordered listsof pending IO requests are maintained: those that can sstill be serviced while the disk arm continues its current direction, and those that must be seerviced after the disk arm changes direction and sweeps back across the disk. IL requests are serviced in order of cylindr number, when there are no further pending IO requestts in the direction the disk arm has been moving, the disk arm reverses direction and starts servicing IO requests that had been behind it. IO requests may arrive while the arm is sweeping, and such requests are sorted into one of the two lists as appropriate.
A) To quantify the benefit of using the elevator algorithm, simulate the disk driver handling IO requests and compute the average and median service time if the requests were handled FCFS and the average and median time if the requests were handled by the elevator algorithm. Comment on the ratio between the FCFS and elevator algorithm results. 

Assume a typical modern disk has about 16000 cylkinders, that the time for the arm to seek the full width of the disk is 5 milliseconds, and that the disk rotates at 7200 rpm. but because of rotational position sensing, after seeking to the appropriate cylinder an IO request only needs to wait for otational delay from the end of where the previous IO request was serviced to the start of where the next IO request is to be serviced. Assume tht the seek time is proportional to the number of
cylinders that must be crossed from the cylinder where the previous IO request was serviced to the cylindeer where the next IO request is to be serviced. (Measurement on any real disk shows this model is incorrect, but close enough for our purpose.)
Assume that the load of IO requests arrive at exponentially distributed distributed time intervals with mean 1 millisecond, that the cylinder distribution is 25% from the swap space (and, for Unix File System, the inode space) that occupies a few cylinders in the middle of the disk but that otherwise the cylinder distribution of IO requests is uniform, and that the length of the dta transfer of an IO request is lognormal, with median 1k bytes and scale parameter 1. Simulate enough IO requests that your averages have less than 1% error.

B) One way to make your simulation run faster, expecially now that almost all personal computers have at least dual cores, would be to wrrite your program as multi-threadd. Regardless of whether you actually have access to a multi-thread environment, indicate where in your program you would have to insert concurrency control (say semaphores) in order to avoid critical races.


Related Discussions:- Make your simulation run faster

Principles of composition, PRINCIPLES OF COMPOSITION The principles of ...

PRINCIPLES OF COMPOSITION The principles of composition are the way that the elements of composition are used to achieve a particular purpose. Some of the main principles of co

What are transmission bridges, What are transmission bridges? A usual ...

What are transmission bridges? A usual transmission bridge is demonstrated in figure. The series capacitance and the shunt inductances of the two relays give a high-pass filte

Explain about combinational circuits, Q. Explain about Combinational Circui...

Q. Explain about Combinational Circuits? Combinational Circuit is one of the models for parallel computers. In interconnection networks, different processors correspond with ea

Knowledge of the environment - artificial intelligence, Knowledge of the E...

Knowledge of the Environment: We must discriminate between knowledge an agent receives through its sensors and knowledge about the world from which the input comes. The world

State in brief about polymorphism, State in brief about Polymorphism C...

State in brief about Polymorphism Class hierarchy is the deciding feature in the case of more than one implementation of properties. An object oriented program to compute the

Explain derived equations and models, Each student will be assigned a binar...

Each student will be assigned a binary system. The experimental references and the conditions are indicated in the table below. The student should make use of software available on

What is a multiplexer tree, What is a Multiplexer Tree? Ans Multip...

What is a Multiplexer Tree? Ans Multiplexer Tree: The largest available MUX IC is 16 to 1. Meeting the larger input requires there must be a provision to expand this. It

What are the input devices, What are the Input devices Various devices ...

What are the Input devices Various devices are available for data input on graphics workstations. Most systems have a keyboard and one or more additional devices specially desi

Problem context and specification, Problem Context and Specification : ...

Problem Context and Specification : However the development of Inductive Logic Programming has been heavily formal in mathematical in nature it means the major people in the f

Explain the t flip flop, Explain the T Flip Flop? The toggle, or T, fli...

Explain the T Flip Flop? The toggle, or T, flip-flop is the bistable device that changes state on command from a common input terminal.   Truth Table

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd