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Joe Colantonio – Selenium-UFT-QTP-SoapUI-ALM-LoadRunner & more

Performance Testing Basics – What is Throughput?

Performance Testing Basics – What is Throughput? post image

What is Throughput:

Basically, “Throughput” is the amount of transactions produced over time during a test. It’s also expressed as the amount of capacity that a website or application can handle. Also before starting a performance test it is common to have a throughput goal that the application needs to be able to handle a specific number of request per hr.

For example:

Let’s Imagine

Let’s imagine that a gas station attendant fills up a car’s gas tank using a gas pump. Let’s also say that it always takes the gas attendant just one minute to fill up any car, no matter how big it is or how low the car’s gas tank is.

Let’s call this gas station “Joe’s Gas,” and envision that it only has three gas pumps. Naturally, if we have three gas pumps and three cars, it follows that Joe’s attendants can only fill up three cars per minute. So, if we were to fill out a performance report for Joe’s gas station, it would show that Joe’s throughput is three cars per minute.

Throughput no wait

This is Joe’s dilemma: no matter how many cars need gas, the maximum number that can be handled during a specific time frame will always be the same –three. This is our maximum throughput; it is a fixed upper bound constraint.

throughput

As more vehicles enter the gas pump line they are required to wait, thus creating a queue.

It is the same concept that applies if we are testing a web application. If a web app receives 50 requests per second, but can only handle 30 transactions per second, the other 20 requests end up waiting in a queue. When presenting performance test results, throughput performance is often expressed as transactions per second, or TPS.

Real performance test throughput results:

I use HP’s LoadRunner (which comes with a throughput monitor) for performance testing. In a typical test scenario, as users begin ramping up and making requests, the throughput created will increase as well.
Once all users are logged in and processing in a steady state, the throughput will even out since the load each user makes stays relatively constant. If we wanted to find an environment’s throughput upper bound we would continue increasing the number of users. Eventually, after a certain amount of users are added, the throughput will start to even out, and may even drop. If the throughput enters this state, however, it is usually due to some kind of bottleneck in the application.

A look at a typical throughput results

Below are the LoadRunner throughput chart results for a 25-user test that I recently ran. Notice that once all 25 concurrent users are logged in and doing work, the throughput stays fairly consistent. This is expected.

Good Throughput Chart

Now notice what throughput looks like on a test that did not perform as well as the last example. All of the users log in and start working; once all users are logged in making request you would expect the throughput to flatline. But in fact, we see it plummet. This is not good.

Bad Throughput Chart

As I mentioned earlier, throughput behavior like the example above usually has to do with a bottleneck. By overlaying the throughput chart with a HP Diagnostics ‘J2EE – Transaction Time Spent in Element’ chart, we can see that bottleneck appears to be in the database layer:

Bad Throughput Chart with HP Diagnostics

In this particular test, requests were being processed by the web server, but in the back end work was being queued up due to a database issue. As additional requests were being sent, the back end queue kept growing, and users’ response times increased.

Recap

To recap: Throughput is a key concept for good performance testers to understand, and is one of the top metrics used to measure how well an application is performing.

Extra
For more detail info on performance testing make sure to grab a copy of Performance Analysis for Java(TM) Websites.

65 comments… add one

  • TM

    Excellent. It helped me to understand with the simple examples and the visual graphs.

    • Joe Colantonio

      TM » Thanks! I really appreciate your feedback. It helps me in planning what types of future post I should focus on. Cheers~Joe

      • Haris

        Hi Joe, thank you for the explanation on throughput. I really like the gas station analogy. I have another basics question though. How would you define SLAs when developing a performance test plan? How much throughput is good, what is acceptable CPU on servers etc. I know there is no one size fits all, but if you can give some examples similar to the gas station analogy, would appreciate it. Thanks.

        • Haris » Thanks Haris! I’ll try to see what I can put together for an SLA post. Thanks for the idea ~Cheers Joe

  • shailesh

    Hi,
    i would like to know…What is pacing?why pacing should be given between iteration or what if pacing is not given…

    Thanks in advance.

    • Joe Colantonio

      shailesh » Hi Shailesh – Good question – I think this quy can explain it better than me:. Hope it helps. Cheers~Joe

    • earnest

      Shailesh,
      Pacing is the time you wait between iterations.

      BTW this is a great article JOE.

      • Joe Colantonio

        Thanks Shailesh! I like your pithy definition for pacing :) Cheers~Joe

  • Paul

    Thanks for the article. It’s really helpful !!

    • Joe Colantonio

      Paul » Thanks Paul – I’m glad it helped you! Cheers~Joe

  • kumar

    Nice article. I do have one question.i was going through the Loadrunner training manual and in that it mentions “If throughput has flattened out while the number of Vusers increase, there is a likely a bandwidth issue.” But i feel your explanation is more correct. can you please shed some views on this?

  • Mathews

    Hi Joe, I woulld like to know that, what are techniques or methods that can be used to evaluate throughput in terms of computing ? [I am a Computer Science Honours student (South Africa), and currently doing something on throughput evaluation ]

    • Joe Colantonio

      Mathews » Hi – First I would use a performance test tool like LoadRunner,SoaSta, Grinder or JMeter to place a load against the test system. I would start with one user and increase the user load by small increments until I found the throughput plateau. I consider a plateau to be the point where either the throughput really falls off or the response time is well over what is acceptable for my requirements.That’s it in a nutshell – this may be to basic for your needs.

  • fazal

    i want to know that what is throughput out and throughput in.
    one think i must tell you, your way of explaining is toooooo good.

    • Joe Colantonio

      fazal » Thanks Fazal.

  • Abhinav

    Thanks Joe for this wonderful post, it helped me a lot.
    However it is clear to me but I just wanted to confirm that throughput(It is also a term in Argeegate Report(Listener) of Apache Jmeter) is same as processing rate of requests, a high throughput means high performance, Right?

    • Joe Colantonio

      Abhinav » Hi Abhinav yes the throughput on the JMeter Aggregate_Report is the same. Not sure I would go as far as to say that high thoughput = high performance. Its one factor in many that needs to be looked at when performance testing an application. Cheers~Joe

  • nikhil

    Hi everyone…

    What is ADHOC testing and when & why this testing is done?

    Thanks,
    Nikhil

    • Joe Colantonio

      nikhil » Hi Nikhil – Ad hoc testing is a commonly used term for software testing performed without planning and documentation. Ad hoc testing is an informal test and usually is a test that is only run once

  • Abhishek

    Excellent Stuff. Finally I am able to understand throughput now.

    • Abhishek » Thanks Abhishek! Let me know if there are other performance concepts you want me to blog about. Cheers~Joe

  • Murali

    Excellent article Joe it made things easy for me
    how many users should i use if my Target is 0.7 TPS

    and is it different if i call a webservice via soapUI

    • Murali » Thanks Murali – its hard to tell without knowing how much wait time you have between transaction and the amount of time your response is for 1 user. You should try to get a handle on how many users the business expects and then try to create a realistic scenario emulating that to check your TPS. Good Luck~Joe

  • Dzmitry Kashlach

    Thank you, Joe! I like comparison with gas station)))).
    BTW, what do you advise to start from when analyzing results?
    Do you use the same approach as in the article from below?
    http://blazemeter.com/blog/how-analyze-results-large-scale-load-test

  • good article. it is very helpful
    thanqs joe.

  • Sajid

    HI Joe,
    Thanks a lot for providing this nice information. Its the best article I have ever went through with very simple and elaborative examples. Its really helpful. Can you please publish few more similar articles on most important LoadRunner monitors like Hits per Seconds, Average Transaction Response Time etc.?

    • Sajid » Thanks Sajid! I’ll try to write some more post similar to this. I usually only write about what I’m currently working on but I will try to focus more on LR again. Cheers~Joe

  • Shiv Raj Sharma

    Hi Joe,

    Very Nice article with lot of information. Please Provide more information on performance testing with LR.

  • Anoop

    JOE>> This is a very good portal for performance testing. Well Done!!!!!!!!

  • Vinod

    Appreicative – very informative :-)

    I am using 9.1 loadrunner, how do we get – HP Diagnostics ‘J2EE – Transaction Time Spent in Element’ graph which show database/appserver in our case.

  • Shinto Abraham M.A

    Thanks a lot ….Joe’s gas gave a good understanding of throughput.

  • Syed

    Amazing! you are doing great job for learner

  • Srikanth

    Thanks joe for the information pertaining to Throughput.
    I have one query After the test is done we can get the total throughput value in bytes and my question is whether we can get the throughput value for a single request.(Example for a single login request how can we measure the throughput value.)
    Thanks In Advance.

  • Mukundan

    Great Article Joe.

  • Ravi Ranjan

    Hi Joe,
    Appreciate the way you explained Throughput.
    I have one question:
    What is the difference between Think Time and Pacing, if we give think time before “return 0″ in script then it will also work like pacing, then wats the difference?

  • Sharath

    Excellent Joe, you have simplified the concept with better understanding

  • celine

    thanks joe, it is reallu useful for understanding what throughput is.

  • celine

    thanks, really useful

  • tester

    Hey
    i wanted to know that if increase the threads in each run and also the ramp up time
    i.e 1st run threads :5 ramp up time is 10 sec
    2nd run threads :10 ramp up time :20 sec
    the throughput and bandwidth will also increase?

  • Shraddha

    Very Informative article!!! Thanks Joe!

    I have a query,we are using LR11. Could u please tell me how to calculate pacing time and what is its significance? should we include Think time as well in pacing time or not?

    Thanks!

  • Anukrrosh

    Hi Joe,
    Its a excellent post, and helped me a lot .. could you please explain the relation between hits/sec, response time and throughput……as I am seeing a lot of people saying different views about this ..

  • bigb

    Very nice example…..good way to present the basic concepts….

  • Preetha

    Thank you Soo much.Really useful information

  • Ramamurthy Pujari

    HI Joe,

    I read the article, you explained very well about throughput. Than you so much. But i did not understand what is the database issue. which database counter you measured for throughput. If you don’t mind can you elaborate in detail the ” back end work was being queued up due to a database issue”.

    Regards,
    Ramamurthy P

    • Hi Ramamurthy – if I remember correctly this issue was that the web server was sending request to the DB but the DB was too busy trying to fulfill previous request. Because of this all the request where building up in a queue. The web servers Processor Queue Length kept increasing which was a clue to me that something was happening on the DB side. I had a db administrator monitor the DB as the test ran to pinpoint what was happening.

      • senthil

        Hi, I need full process of Performance testing and how to do that for single user and 5 user. Thanks

  • anitha

    HI Joe,

    Nice blog…
    I have a question… If the hits per sec is high and the throughput is low,what does it mean?

    • Ramamurthy

      Joe-Thank you so much for reply.
      Anitha- Below are the points two cause the low throughtput

      1. Network bandwidth- constraint. beacuse htis/sec increases as vusers increase also throughtput also increase. but throughput decreases means shortage in the network bandwith or more utilization or crossing the limit of bandwidth.

      2. Less number configeration of thread pools.
      3. CPU utlization reached more than 90%.

      Please correct if i am worng for above points regarding the throughtput decrease eventhough Hits/sec increases.

      Regards,
      Ramamurthy P

  • Anandh

    i have one doubt in load runner?
    if we increase the through put, should the response time take more time?

    • Depends – in general I would say eventually yes as your throughput goes up response time usually goes up as well once the server’s resources start to get heavily utilized.

  • Gaurav siwach

    Hi Joe

    whenever you do a performance for a website

    which of the following types of testing u normally perform in every iteration

    Load
    Stress
    Scalablity
    Volume
    Endurance

    BTW awesome website man..

    • Hi Gaurav – great question but its hard to answer other then it depends. I think at a minimum you want to do some kind of Load test to make sure that performance has not changed from the previous release. Also you want to do performance testing as early as possible.

  • Shafee

    Very good article…thanks joe. I am very big fan of all ur posts

  • Manju

    Nice post

  • vijaya

    Joe …Thankyou verymuch for this excellent article.

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