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From David Smith <>
Subject Re: Question on JVM memory in tomcat
Date Sat, 13 Dec 2008 15:31:23 GMT
Caught one of my own flaws in that one right after I sent it.

Total memory - free memory is what's actually being used. Total is
what's been reserved before. If free memory goes to zero, the jvm adds
memory to the total up to max memory. If you're worried about memory
consumption, just watch total as it compares to max. In your case you
aren't even using 10% the max.


David Smith wrote:
> My limited understanding, but free memory is memory the JVM has used
> before and freed up. In your case, total memory probably went up to
> 149.31 MB at one point, then memory was freed creating that 38.13 MB
> free memory. If the sum of Free and Total add up to max, I would worry
> since that implies at some point, the total memory actually hit max. If
> this machine has other things going on, you might want to consider
> watching it for a while and then trimming back the max memory.
> There are some people on this list with a phenomenal understanding of
> the JVM and all it's internals. I'm sure they'll correct me if I got it
> wrong in any way. :-)
> --David
> wrote:
>> Hi, 
>> I am using the tomcat manager to monitor the health of the tomcat server. I found
that the session of JVM, it shown the following information: 
>> JVM
>> Free memory: 38.13 MB Total memory: 111.18 MB Max memory: 1365.37 MB
>> Is my tomcat in good condition or not?
>> It seems that the free memory is only 38.13MB?
>> I have added the following lines in my
>> export JAVA_HOME=/opt/jdk
>> export JAVA_OPTS=-Xmx1536m
>> export CATALINA_HOME=/opt/tomcat
>> How to know whether my tomcat can use the memory or not? 
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David Smith
College of Agriculture and Life Sciences
Cornell University
B32 Morrison Hall
Ithaca, NY 14853
Phone: (607) 255-4521

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