Re: [Wrapper-user] jvm tuning options

[Leif M. <le...@ta...>]

Shann,

prashant n wrote:
> i am able to run all my java classes and jboss app server through 
> service wrapper. I have a server with 2 GB RAM and 2 cpus. I would 
> like to use the JVM tuning options like -Xss256k, -XX:+UseParallelGC, 
> -XX:ParallelGCThreads=20 and -XX:+AggressiveOpts. How should i specify 
> these in my conf file ?
>
> is this the right way of doing this jvm optimization ?
>
> wrapper.java.additional.5=-Xss256k
> wrapper.java.additional.6=-XX:+UseParallelGC
> wrapper.java.additional.7=-XX:ParallelGCThreads=20
> wrapper.java.additional.8=-XX:+AggressiveOpts
This looks correct assuming the 1-4 properties also are defined.  Have 
you tried this?
> If my init & max meomries are set 1024 MB then how much total memory 
> is cosumed by the system along with the service wrapper ?
It depends on the JVM version, but the java portion of the wrapper is 
very light weight.
and only takes a little over the standalone JVM.
The Wrapper binary process a couple MB.

Why do you want your init memory so high.  From what I have seen that 
will mainly just
slow down the startup of your application.  Once the memory is 
allocated, the JVM will
run faster.  But that will happen after it has allocated it the first 
time anyway.
You do get the benefit of knowing if there is going to be enough memory 
right at
startup though.   Problem is that the JVM will take all of that memory 
even if it doesn't
really need it.
It also has the drawback that the garbage collector will wait longer to 
do Gcs.  That
may seem good at first, but depending on JVM version, each individual Gc 
will be
longer and cause larger hiccups in your app.

Cheers,
Leif