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    Load Generator Sizing/Capacity for Vusers

    Machine 512 MB RAM
    Pentium 700

    Action = accesing a single 50 k web page.

    I tried on machine with 256MB and it couldn't get more than 250 users before failing.


    [Original topic name: Is it possible to run 400 users on one machine]

    [ 04-20-2006, 12:55 PM: Message edited by: JakeBrake ]

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    Re: Load Generator Sizing/Capacity for Vusers

    What failed?
    What OS did you use?
    What recording mode did you use?
    What were the RT settings?
    What version of LoadRunner do you use?


    ------------------

  3. #3
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    Re: Load Generator Sizing/Capacity for Vusers

    Raul,

    My assumption is that you are using Windows NT 4 SP6 /Win2K. The memory footprint of a LoadRunner 7.02 Web VUser on that is 4.6 MB.

    I have a doc from the support site that talks about the memory footprints of different types of VUsers. I could mail it to you if you want.
    Suresh Nageswaran, CQA, CSTE
    Lead Consultant
    Kanbay Inc.
    Pune, India.
    sureshnageswaran@yahoo.com

  4. #4
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    Re: Load Generator Sizing/Capacity for Vusers

    LR version 6.5
    NT 4 Server

    RT settings were

    proxy: direct connection to internet
    ms ie 5.0 http 1.0
    everything else was default RT settings


    launching from Scheduler

    Scheduler settings:
    load/terminate all users at once
    initialize entire group before running

    It seems like 190 out of 200 will sucessfully go through the Initialize, Ready, Running,
    process.

    The other 10 users are listed in RED color in the "Error" column with picture of fallen down runner.

    It says "see output window for more details"
    ( I don't know where this output window is)



    If I am sitting by the monitor, I can click the "Error" column and launch the 10 users.

    Is there any way to make it do this automatically , i.e., all users initialize successfully before running?




    ------------------
    Raul
    softwaretest@hotmail.com

  5. #5
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    Re: Load Generator Sizing/Capacity for Vusers

    <BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>
    It says "see output window for more details"
    ( I don't know where this output window is)<HR></BLOCKQUOTE>


    To view the output window, go to View > Show Output - you can then filter your messages depending on type.

    Hope this helps,
    Steven.

    ------------------


    [This message has been edited by stevenh (edited 02-11-2002).]

  6. #6
    Moderator JakeBrake's Avatar
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    Re: Load Generator Sizing/Capacity for Vusers

    <BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>Originally posted by Raul_2001:

    Machine 512 MB RAM
    Pentium 700

    Action = accesing a single 50 k web page.

    I tried on machine with 256MB and it couldn't get more than 250 users before failing.

    <HR></BLOCKQUOTE>

    Hi Raul. I would be surprised if you could safely get more than 50 users to execute as you expect. Remember, each vuser uses host resources, including timers for think time. The load generator has finite processing capacity.

    The controller allows you to specify max threads per machine. I think this defaults to 50. You can set it to a higher value, but you risk instability and the ability to impart the desired load. Despite memory and cpu speed and depending upon your test objectives - your load generator is susceptible to becoming a bottleneck in its own right. You would need to monitor your load generator's nic to see how well it performs - say at 50 users and then at 200 users, for example. Let us know what you discover.


    ------------------
    JP

    [This message has been edited by jpensyl (edited 02-12-2002).]

  7. #7
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    Re: Load Generator Sizing/Capacity for Vusers

    Raul,

    Consider ramping up very gently to your maximum on the box. Be sure and observe the same system bottleneck statistics on your load machine as you do on your server under test. If you begin to observe that your CPU is spiking on your load box, your instruction queue depth is deepening, your memory pool is full and swapping is occuring at a higher rate, your network retransmits are high .... Well, you get the idea.

    From a transaction perpective, what you will see when your load box is 'coloring' your sample set is that your transaction times are increasing -- however your server under test does not appear to be working any harder. Your server under test may even begin to look healthier for some of the stats because messages from the clients are not being sent as fast. Think of resource utilization peaking and then declining on the server (bell curve), but resource utilization remaining static or increasing on the load box with each added user. Your load box is able to allocate fewer and shorter time slices to each end-user process as it manages the hardware and software interrupts for disk i/o, network, cpu cache, etc...

    It should go without saying, but also be sure and not run the controller on the same box as is producing the load and be sure and select 'blank' as the screen saver. Video interrupts are expensive and would have to be serviced in the case of a screen saver or running the controller on the PC. The controller itself would be considered an expensive process when run alongside a bunch of virtual users.

    ------------------
    James Pulley
    nospam.jpulley@nospam.itestsolutions.com
    iTest Solutions, Inc
    704-243-2854 (voice)
    James Pulley

    Replace ineffective offshore contracts, LoadRunnerByTheHour. Starting @ $19.95/hr USD.

    Put us to the test, skilled expertise is less expensive than you might imagine.

    Twitter: @LoadRunnerBTH @PerfBytes

  8. #8
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    Re: Load Generator Sizing/Capacity for Vusers

    to Punekar:

    Your data about 4+ mB per vuser is wrong. I'd estimate it (roughly, of course) as 400k .. 1mB per vuser depending on the recording type and amount and type of data downloaded.

    to Raul:

    1) Why don't you get the latest version of LR? However, for LR 6.5 install the scalability update (can be downloaded from the support site).

    2) The performance of the load generator depends on the following MAIN factors:

    a) Type of the vuser recorded
    b) Think Times used: the bigger the TT, - more vuses you can run
    c) HTTP version you choose
    d) If you select to download images or not in RT settings
    e) and many other minor issues like SSL and/or certificates + other stuff...

    The best way to estimate, - the empirical way. It shouldn't take longer than 30 min to estimate it by yourself. Just ramp it up slowly and see the delta per 5/10/20 vusers.

    Please, mind that the OS and its settings can affect the scalability of the load generator as well.

    Yes, you can initialise vusers in the scheduler before the ramp up. However, for scenario of 200 vusers only it might be better to control it manually.

    Regards,
    --Ilia

    ------------------

  9. #9
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    Re: Load Generator Sizing/Capacity for Vusers

    ilia

    I just ran a scenario to crosscheck. Running as each user as a process, I monitored the memory usage by mmdrv.exe. Came to about 3890 KB. My script is a really simple one with just 5 steps - login, lookup user, logout.

    Of course, I suppose running it as a thread would be that much better in terms of memory consumption.

    The figures I obtained for the VUser footprints are from MI support.
    Suresh Nageswaran, CQA, CSTE
    Lead Consultant
    Kanbay Inc.
    Pune, India.
    sureshnageswaran@yahoo.com

  10. #10
    Moderator JakeBrake's Avatar
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    Re: Load Generator Sizing/Capacity for Vusers

    <BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>Originally posted by ilia:

    ... For Ilia and Raul...
    2) The performance of the load generator depends on the following MAIN factors:

    a) Type of the vuser recorded
    I agree.

    b) Think Times used: the bigger the TT, - more vuses you can run
    Think times use system resources. Timers are expensive. The more vusers consuming timers, the greater the impact on cpu cache.

    c) HTTP version you choose

    Adding detail here... Using web_concurrent would impact the quantity of vusers.

    d) If you select to download images or not in RT settings
    e) and many other minor issues like SSL and/or certificates + other stuff...

    The best way to estimate, - the empirical way. It shouldn't take longer than 30 min to estimate it by yourself. Just ramp it up slowly and see the delta per 5/10/20 vusers.

    Please, mind that the OS and its settings can affect the scalability of the load generator as well.

    Other - NIC, processes/services (not of the default OS set) that have been configured to run.

    Yes, you can initialise vusers in the scheduler before the ramp up. However, for scenario of 200 vusers only it might be better to control it manually.

    Regards,
    --Ilia

    <HR></BLOCKQUOTE>

    It would be interesting to hear about any successes with large numbers ( greater than 50-100) of vusers on a single load generator. I would be curious to know if the O/S, and NIC kept up. I would also wonder how timers were impacted and if lr_rendezvous was as robust with large numbers of vusers versus 20 to 30. Anyone...?



    ------------------
    JP

 

 
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