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Review question of Synchronization

Explain the three different types of scheduling: long-term, mid- term, and short-term. what does the operating system do and when?

Long-term scheduling is used to admit new processes to the system and is done whenever a user wants to create a new process.

Medium-term scheduling is used to swap processes between secondary storage and main memory and is done periodically to ensure theCPU utilization is high and that the page fault rate is low.

Short-term scheduling is used to allocate the CPU to a process and is done whenever a process has its timeslice expire, or when thecurrent process needs to perform some I/O.

Explain why shortest process next, shortest remaining time, and highest response ratio next all need to estimate the future cpu bursts of eachProcess. explain how this is done.

All of these scheduling algorithms try to order the queue according to the next CPU burst a process is likely to have. Since it isnot possible to look into the future or examine the process and know the length of the next burst, this quantity must be estimated. This is done by using pastCPU bursts to predict future burst. The estimate of the next CPU burst is calculated as a weighted, exponential average. The previous CPU burst is givenweight alpha and the current estimate is given weight (1 - alpha). By varying alpha, more weight can be given to the most recent CPU burst, allowing forfaster reaction to changes in a process but also a highly varying estimate. Giving weight to the previous estimate allows the estimate to change moresmoothly. In effect, the estimation equation gives an exponentially smaller weight to CPU bursts the farther in the past they occurred.

Most round-robin schedulers use a fixed size quantum. give an argument in favor of a small quantum. now give an argument in favor of a largeQuantum. compare and contrast the types of systems and jobs to which the arguments apply. are there any for which both are reasonable?

A small quantum reduces the response time for all processes, which is important for interactive processes. However, a long quantumreduces the overhead of process switching, which increases throughput and CPU utilization. A short quantum is useful for a general-purpose computer. A longquantum is useful for a batch system. You might have a system that uses a short quantum when there are jobs that need a quick response time, then lengthens thequantum when heavy computation needs to be done.

Which type of process is generally favored by a multilevel feedback queuing scheduler -- a processor-bound process or an i/o-bound process? brieflyExplain why.

A I/O bound process is favored by a multilevel feedback queueing scheduler because jobs that use the CPU heavily will be movedto low priority queues. This will leave the I/O bound processes in the higher priority queues.


Consider an environment in which there is a one-to-one mapping between user-level threads and kernel-level threads that allows one or moreThreads within a process to issue blocking system calls while other threads continue to run. explain why this model can make multithreaded programs runFaster than their single-threaded counterparts on a uniprocessor machine.

The issue here is that a program spends much of its time waiting for I/O to complete. In a multithreaded program, one KLT can makethe blocking system call, while the other KLTs can continue to run. On a uniprocessor machine, a process that would otherwise have to block for all thesecalls can continue to run its other threads.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Operating systems. OpenStax CNX. Aug 13, 2009 Download for free at http://cnx.org/content/col10785/1.2
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