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Memory when stress test with JMeter

Posted on 2011-04-28
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Last Modified: 2012-05-11
Hi Guys,

We're using JMeter to load test our web based Java application, deployed in Linux server, web server : apache tomcat.

We run it for 25 concurrent users. And the memory spike into 2GB.

Then we stop the test on JMeter, but the memory is still on 2Gb, why the memory doesn't decrease although we had stopped the test in JMeter?
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Question by:softbless
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Expert Comment

by:CEHJ
ID: 35483042
>> but the memory is still on 2Gb

For how long, and measured by what means?
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Author Comment

by:softbless
ID: 35487483
Well, actually only 2 minutes after stopping the testinng.

We're using like a task manager in CentOs.

is it a common behavior? how many minutes, the memory will get normal approximately?
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LVL 92

Accepted Solution

by:
objects earned 1000 total points
ID: 35487862
because the memory is still being referenced, and/or the gc has not run or needed to free it up.
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LVL 92

Assisted Solution

by:objects
objects earned 1000 total points
ID: 35487867
And the memopry shown in OS is the memory allocated to the java process. It is not the amount of heap used by the application.
Typically it will increase (to the limit specified by -Xmx) , but not decrease
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Assisted Solution

by:Phil Phillips
Phil Phillips earned 500 total points
ID: 35487896
Like other experts have said, the memory usage isn't really indicative of what the application itself is using.  The java process itself won't free up the OS memory... but you can look into the java heap to see what your application is using.

jstat is a good command line tool to check the JVM memory.

If you want a more comprehensive GUI, you can try jconsole
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LVL 28

Assisted Solution

by:dpearson
dpearson earned 500 total points
ID: 35488310
You need to be clear on the difference between the allocated memory for the process (which won't decline on Linux) and the amount actually in use (which should decline after garbage collection).

The best tool today for looking at all of this, and tons of other cool profiling is visualvm (http://visualvm.java.net/).  Today it's bundled with JDK6 and it's really an amazing tool.  I'm sure it's putting many of the commercial profilers out of business.

Doug
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Author Comment

by:softbless
ID: 35489117
Hi Guys,

Fyi, the program that running Java only 1 application.

Thanks for the input, maybe you are interested to answer how to free the memory for this case, the question is in : http://www.experts-exchange.com/Programming/Languages/Java/Q_26984796.html
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Author Closing Comment

by:softbless
ID: 35810305
thanks
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