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Recently in an interview I was asked the question, to find Vusers using throughput and response time. Question. Find Vusers for throughput of 1260 bits per second and response time of 2 Milli seconds. The duration of the test we have run to achieve these results is 1 hour.

When I asked he said No thinktime or pacing, so it's zero. So, As per Littles law, i calculated it as response time * throughput 1260*(0.002)=2.52 or 3..He said it's wrong..

Is there anything iam missing here? If yes then please let me know.. As per the response time as 2 Milli seconds which is rare I think 3 user should be ok..But if iam wrong then what is the correct calculation..

Vikram
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1 Answers1

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You do not want to work for this person.

In collapsing the time between requests to zero your interviewer has collapsed the client-server model, which is predicated upon a delay between requests from any singular client where requests from other clients are to be addressed.

James Pulley
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  • But, what is the right way? Is my approach correct or is there any other approach? – Vikram Jan 22 '18 at 12:38
  • Littles law minimizes the number of users to hit a defined throughput number. As such an algorithm which minimizes users, the burdened costs associated with session become underrepresented in your test versus production. It is not the path I would take and would ask additional questions about the direct observed nature of the load in production. – James Pulley Jan 22 '18 at 13:49
  • Littles law does not minimize the number of users. It gives the approximate count of the Vusers. Anyways you still did not mention what is the right method. But I have already got this confirmed that the data provided by him was wrong and nothing wrong with the approach. Littles law does not give the accurate results as per production it's our job to run some tests with and around the approximate value found. There are other ways for the approach as well.Thank you for the reply.. Appreciate it.. – Vikram Jan 22 '18 at 15:34