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Super Contributor.
Super Contributor.
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Is counter java.lang/Memory/HeapMemoryUsage/max (JMX Monitor) truly the maximum?

Hello,

 

I have a question regarding java performance counters. Attached is a picture of a performance measurement that was created over a long running load test. What strikes me here is the "Max" line resembling java.lang/Memory/HeapMemoryUsage/max (JMX Monitor). Since the JVM under test is tuned to 1024m for -Xmx, I expected the max line to reflect this. Instead I see the line starting at 954,466,304 bytes and later on it is raised to 1050,476,544 bytes, which according to me this is still not the equivalent of 1024m (that would be 1073,741,824 according to my calculations)

 

Apparently the max in this graph isn't really the max since it is raised while the test is running.

 

Question: What is it then?

 

I am trying to get a grasp of this as I am no JVM memory management Guru (but trying to become one 😉

 

All in all it still looks to me like this JVM is in trouble.

 

I appreciate any help in understanding this.

 

Regards,

Peet

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Micro Focus Expert
Micro Focus Expert

Re: Is counter java.lang/Memory/HeapMemoryUsage/max (JMX Monitor) truly the maximum?

It didn't get to the maximum point because it didn't need to get to that point.

You can reduce the -Xmx and try to run again to verify.
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Super Contributor.
Super Contributor.

Re: Is counter java.lang/Memory/HeapMemoryUsage/max (JMX Monitor) truly the maximum?

Hi Bach,

 

That part I do understand also running the test a little bit longer will probably do teh trick. But what puzzles me is why the max line isn't at 1024m to begin with. Instead it starts lower and when used memory approaches it, it is suddenly raised to a level that still isn't the configured -Xmx level.

 

I wonder how this works?

 

Regards,

Peet

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Micro Focus Expert
Micro Focus Expert

Re: Is counter java.lang/Memory/HeapMemoryUsage/max (JMX Monitor) truly the maximum?

-Xmx is maximum, please use -Xms to meet your requirement.

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