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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: tomcat.conf JAVA_OPTS
Date Wed, 05 Dec 2007 08:38:41 GMT
Caldarale, Charles R wrote:
>> From: Rainer Jung [mailto:rainer.jung@kippdata.de] 
>> Subject: Re: tomcat.conf JAVA_OPTS
>>
>> c. wrote:
>>> I'm wondering what the JAVA_OPTS -Xminf0.1 and
>>> -Xmaxf0.3 are.  Anyone know?
>> MinHeapFreeRatio and MaxHeapFreeRatio (divided by 100).
> 
> I'd recommend not setting these unless you really know what's going on
> inside your heap.  It's usually more beneficial to set -Xms to the same
> value as -Xmx.

Me to :)

>>> Also, is there a way to start tomcat and have it
>>> spit out what JAVA_OPTS it's using?
> 
> Some of the options are processed by the launcher, some by the JVM
> proper, so there's not any really good way to see them all.  You can set
> the environment variable _JAVA_LAUNCHER_DEBUG, and it will provide some
> information about what the launcher is doing and what it's passing on to
> the JVM.
> 
> Lambda Probe will let you look at System properties, some of which are
> derived from the command line arguments.  (You can also find them in
> JConsole, but it's ugly.)  JConsole will also show the arguments the JVM
> sees under java.lang -> Runtime -> Attributes -> Input Arguments on the
> MBeans tab.

I overlooked this part of the question:

/usr/local/jdk1.6.0/bin/java -XX:+PrintVMOptions -Xmx10m 
-XX:+PrintTenuringDistribution -verbose:gc myTest

produces

VM option '+PrintVMOptions'
VM option '+PrintTenuringDistribution'

...


/usr/local/jdk1.6.0/bin/java -XX:+PrintCommandLineFlags -Xmx10m 
-XX:+PrintTenuringDistribution -verbose:gc myTest

produces

-XX:MaxHeapSize=10485760 -XX:+PrintCommandLineFlags -XX:+PrintGC 
-XX:+PrintTenuringDistribution -XX:+TraceClassUnloading


The first option outputs your original XX switches (only those) as you 
have given them, the other one outputs a semi internal view of how those 
flags have been mapped.

Regards,

Rainer

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