To calculate ThinkTime using Little's Law-

[Yathish Kumar]

All,

 

I have following information,

1). Transaction Response Time

2). No. of users

 

By using the above information,

a). how can we derive ThinkTime and

b). how we can validate the defined Response time is acceptable.

 

EX -

 

I tried with Little’s law [ NofUsers=Arrival Rate * (RT + TT) ] but didn’t successful in calculating the think time.  Let me know if my approach is wrong. 

 

 

Kindly help me on this.

 

Many Thanks,

Yathish

[Sagar Aggarwal]

Your approach looks faulty here to me.

Why do you need to calculate TT. It's upto you to decide what do you want to keep in the script. Normally we calculate pacing. Anyways, you need Vusers and TPS to calculate pacing.

RT, that you mention looks like a SLA to me. How did you get this RT information??

Regards,
Sagar Aggarwal
+917875624650

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[Mital Majmundar]

Just use the basic formula.
3600/(no of transactions per vuser)

You need to get the transactions to be achieved and then divide that for all vuser.

Also instead of gpong for think time calculation, just do the above and select the third option from run time setting and make think time a fixed global value after every transaction.

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[Yathish Kumar]

Thanks for all your responses.

My question itself was wrong and with invalid # of input data’s.

 

I was trying to Modelling the system performance using Fundamental laws – Littles Law.

I was Developing the Analytical Models/capacity model  for the application wrt using Workload Models, Universal scalability law, Response time theory, Queuing theory etc..

Achieved around 50% using the below formulas,

 

•Uavg – Average System Utilization

•X – System Throughput

•St – Service Time

•M – Number of Servers

 

Let’s take a look at all of the equations -

•Uavg = [ X * St ] / M

•Rt = St / [ 1 –  Uavg * M]

•Rt = Qt +

•Qt = Rt – St

•Q = X * Qt

 

Once again thanks !!

 

Regards,

Yathish

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[Ruslan Kholyavkin]

Hi Yathish

It very good that you try to modeling  workload based on multiple laws ,but in order for you to do it -  you are missing big part of the puzzle.

Inside one email respond it is  hard  give you answer to your question. I will encourage you to read a book " Solving Enterprise Application Performance Puzzle - Queuing Model to the Rescue"  it will give you much more details in order to accomplish what you try to accomplish. Basically you need to understand first your hardware and network topology . Run single user test figure out your best transaction time - assuming that  external device like database is not becoming  bottleneck itself . same  thing for internal for example does your application are multiple threaded or single threaded and so on ... I think I  can go on and on about precondition you should have before you can  apply laws .For you will be much better to read the book in mention and come up with our own way of doing it

Thanks,

Ruslan

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[Yathish Kumar]

Thanks Ruslan for your reply. Sure will read that book n it will be more helpful.

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