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From sebb <>
Subject Re: Odd problem with performance of JMeter
Date Wed, 22 Jun 2011 20:51:48 GMT
On 22 June 2011 21:02, Deepak Shetty <> wrote:
> you can load the resultant jtl file in any of the standard listeners to see
> the same output that you see

You can also use:

which is designed for non-GUI runs.

Then anaylse the results in more detail off-line.

> You can specify in whatever you need to be saved in the
> jtl file
> The constant throughput timer does not behave intutively - i believe the
> constant throughput shaping timer is better from jmeter-plugins
> regards
> deepak
> On Wed, Jun 22, 2011 at 12:58 PM, John Lussmyer <>wrote:
>> I hadn't noticed the Constant Throughput Timer, that does even things out a
>> bit.
>> This isn't formal perf testing, just making sure that our latest changes
>> haven't completely hosed up performance.
>> What I really need after running this for X amount of time is what is
>> displayed by an Aggregate Report - which is a listener - which it's
>> suggested I not use.  Makes it more difficult to get the values!
>> Also, when I run from the command line with the -l switch, the (one and
>> only) Response Assertion is spewing XML to the file, and I haven't found a
>> way to turn that off.
>> I can get the Aggregate report to output CSV, but that data doesn't seem to
>> be what is displayed by the report.  I'd LIKE to see the values displayed in
>> the output file.
>> Using the Constant Throughput timer, I haven't been able to drive the App
>> server CPU usage up much at all.
>> Using the old Constant Delay timer I was able to do so.
>> Constant Throughput has been a bit odd, both the JMeter machine and App
>> server machines run at nearly the same CPU usage, and track each other.
>>  There will be short (minute or two) bursts where they both go up to about
>> 17% usage, but then they both drop back down to around 9% for a while.  In
>> these cases, the response times do seem to vary somewhat, but since I
>> haven't been able to log them properly yet, I can't be sure of the
>> correlation between response times and cpu usage.
>> (and yes, I know CPU is only one of the factors.  In this case, it's the
>> one we know will be a problem.)
>> -----Original Message-----
>> From: Oliver Lloyd []
>> Sent: Wednesday, June 22, 2011 11:58 AM
>> To:
>> Subject: Re: Odd problem with performance of JMeter
>> Hi John,  When running tests like this you need to think in terms of
>> throughput rather than total transactions achieved. So you mention you are
>> aiming to get 800,000 requests but actually you want to define a throughput
>> rate and have this as your target. Then, the volume of requests is simply a
>> matter of time, the longer you run the test the greater the volume.
>> So, you should setup your test plan to achieve a rate of requests per
>> second. You can do this using the Constant Throughput Timer. Try spreading
>> the requests over more threads, this will increase concurrency. The actual
>> concurrency is also something you may want to think about - what is the
>> expected concurrency that your need to prove is possible?
>> Keep in mind when you are doing this that the response time for each
>> request
>> will be a factor in how many requests each thread can deliver, if it takes
>> 1
>> second to process each request then the maximum throughput per thread is 60
>> per second. It's basic math.
>> Now, once this is place you can begin to run some tests. Try starting at a
>> lower value and evaluating your system at this steady rate - do you see the
>> same drop off? The key here is to hold the request rate at the desired
>> level
>> and not let the test run as fast as it can. If you let things run wild
>> without any control it makes debugging issues much harder.
>> If, you are able to maintain a steady rate without degradation at, say, 50
>> requests per second, then you could try a higher rate, or you could even
>> try
>> a gradual ramp up. Keep this slow, there's no point hammering your system
>> hard right from the start as this will produce unrealistic data.
>> When running tests you should keep an eye not just on CPU usage but also
>> lots of other things. Memory usage on the JMeter box is something that
>> cause
>> issues but there are also a wide range of metrics from your system that can
>> also cause the behvior you mention.
>> Make sure you use an Assertion to verify that the response you are getting
>> back is in fact what you expect it to be. You might find that you are
>> getting errors but JMeter is displaying success because it sees a 200
>> response - this is a very common error.
>> Finally, as Deepak mentions, using listeners are high request rates can
>> create a bottleneck in the test rig and typically it is better to run the
>> actual load tests from the command line but you first need to prove that
>> this is your issue and you can do this by running a few simple experimental
>> tests at differing rates. If you can show an issue on the test rig then the
>> best option might be to distribute the load but before doing this you need
>> to establish that a steady rate - over time - is possible from one machine.
>> If this is not possible even at lower rates then you've very likely got a
>> application issue (although it is odd that you mention the response times
>> remain constant.)
>> Think of it like a scientific experiment, put a white coat on and use the
>> word 'logical' a lot.
>> --
>> View this message in context:
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