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In a threaded program, which resources are shared by the entire process and which are associated with each thread?

The process address space, structures used for interprocess communication, files, and I/O resources are associated with theentire process. Each thread gets its own execution state, context (registers), stack, and local variables.

Consider the following code:

  1. for (i = 0; i<10; i++)
  2. for (j = 0; j<10; j++)
  3. a[i] = a[i]* j
    • Give one example of the spatial locality in the code.

Spatial locality occurs when the array a is accessed sequentially.

  • Give one example of the temporal locality in the code.

Temporal locality occurs when i is used repeatedly with the same value in the second loop.

Consider a memory system with the following parameters:

  • Tc = 100 ns
  • Tm = 1200 ns
  • Cc = 0.01 cents/bit
  • Cm = 0.001 cents/bit
  1. What is the cost of 1 MByte of main memory?

Cost = Cm x 8 x 220 = $83.89

  1. What is the cost of 1 Mbyte of main memory using cache memory technology?

Cost = Cc x 8 x 220 = $838.86

  1. If the effective access time is 10% greater than the cache access time, what is the hit ratio H?

1.1 x Tc = Tc + (1 - H)Tm110 = 100 + (1 - H) x 12001200 x H = 1190H = 1190/1200 = 99.2%

A computer has a cache, main memory, and a disk used for virtual memory. if a referenced word is in the cache, 20 ns are required to access it.If it is in main memory but not in the cache, 60 ns are needed to load it into the cache (this includes the time to originally check the cache), and then theReference is started again. if the word is not in main memory, 12 ms are required to fetch the word from disk, followed by 60 ns to copy it to the cache,And then the reference is started again. the cache hit ratio is 0.9 and the main memory hit ratio is 0.6. what is the average time in ns required to access aReferenced word on this system?

There are three cases to consider:

Location of Word Probability Total Time for Access (ns)
In cache 0.9 20
Not in cache, but in main memory (0.1)(0.6) = 0.06 60 + 20 = 80
Not in cache or main memory (0.1)(0.4) = 0.04 12ms + 60 + 20 = 12,000,080

So the average access time would be:

Avg = (0.9)(20) + (0.06)(80) + (0.04)(12000080) = 480,026 ns

Suppose that we have a multi-programmed computer in which each job has identical characteristics. in one computation period, t, for a job, half theTime is spent in i/o and the other half in processor activity. each job runs for a total of n periods. assume that simple round-robin scheduling is used, andThat i/o operations can overlap with processor operation. define the following quantities:

  • Turnaround time = actual time to complete a job.
  • Throughput = average number of jobs completed per time period T
  • Processor utilization = percentage of time that the processor is active (waiting)

Compute these quantities for one, two, and four simultaneous jobs, assuming that the period T is distributed in each of thefollowing ways:

  1. I/O first half, processor second half

When there is one job, it can do I/O or run on the processor whenever it wants. So the quantities are:

  • Turnaround Time = N*T
  • Throughput = 1/N
  • Processor Utilization = 50%

When there are two jobs, one starts right away and does I/O. When it switches to run on the CPU, the second can start its I/O. Thisdelays the second job for 1/2*N, but otherwise they alternate between I/O and CPU. Assume the jobs are long, so the extra 1/2 a cycle is insignificant.Then:

  • Turnaround Time = N*T
  • Throughput = 2/N
  • Processor Utilization = 100%

When there are 4 jobs, the CPU is round-robin among the four, as is the I/O. This means the jobs are interleaved as:

Job1: I/O CPU I/O CPU

Job2: I/O CPU I/O CPU

Job3: I/O CPU I/O CPU

Job4: I/O CPU I/O CPU

A job can execute for one cycle T, then it must wait for T before doing another cycle. Again assume the jobs are long so that anyinitial wait is insignificant. Then:

  • Turnaround Time = (2N-1)*T
  • Throughput = 2/N
  • Processor Utilization = 100%
  • I/O first and fourth quarters, processor second and third quarter

The answers for this part are the same as the first. This is easy to see for the case of 1 job and 2 jobs. When there are 4 jobs, theCPU is round-robin among the four, as is the I/O. This means the jobs are interleaved as:

Job1: I CP O I CP O

Job2: I CP O I CP O

Job3: I CP O I CP O

Job4: I CP O I CP O

An i/o-bound program is one that, if run alone, would spend more time waiting for i/o than using the processor. a processor-bound program is theOpposite. suppose a short-term scheduling algorithm favors those programs that have used little processor time in the recent past.

  • Explain why this algorithm favors I/O-bound programs.

The algorithm favors I/O bound processes because these will be much less likely to have used the processor recently. As soon asthey are done with an I/O burst, they will get to execute on the processor.

  • Explain why this algorithm does not permanently deny processor time to processor-bound programs.

This algorithm does not permanently deny processor time to processor-bound programs, because once they have been prevented fromusing the processor for some time they will be favored by the scheduling algorithm.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
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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