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From sebb <seb...@gmail.com>
Subject Re: Constant throughput timer not giving expected results
Date Fri, 09 Sep 2011 11:57:09 GMT
On 9 September 2011 04:31, E S <electric.or.sharp@gmail.com> wrote:
> I'm having some trouble getting the Constant Throughput Timer to work the
> way I want in certain cases.
>
> I have a single thread group of 100 threads, all of which are requesting the
> same resource over and over for 1 minute.
>
> I attached a Constant Throughput Timer on the thread group and ran a series
> tests with the throughput throttled at higher and higher levels such as
> 6000, 8000, 10000, etc. Here is a table showing the throughput timer
> settings and the actual number of requests that the server under test
> responded to:
>
> thruput-setting..........actual-requests-served
> 36,000.....................36,000
> 48,000.....................48,000
> 60,000.....................60,000
> 72,000.....................60,000
> 84,000.....................60,000
>
> So it looks like the server under test simply can't respond to more than
> 60,000 requests per minute right? However, when I disable the throughput
> timer I get way higher throughput, something like 350,000 requests per
> minute. What's going on here? Why is the throughput timer giving me these
> results? Is it possible that JMeter is spending so much time trying to keep
> the throughput at the right level that it doesn't have enough cycles left to
> dedicate to actual requests? I tried distributing the load across multiple
> load generators but it didn't seem to help.
>
> The results above have the throughput timer configured using Calculate
> Throughput based on = "all active threads in current thread group". I tried
> changing this to "all active threads in current thread group (shared)" and I
> get the maximum results of 350,000 as if the throughput timer was not even
> there. I must admit I don't understand the difference between the two
> settings, but neither result sounds right.
>
> Any ideas about this?

Create a test plan using the Java Sampler with timer settings that
correspond to your server.

Run a test with CTT disabled and check you get the desired throughput
(use Summary Listener).

You can then experiment with the CTT without needing to take server
and network behaviour into account.

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