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Anurag,
On 6/16/2009 10:09 AM, Mehrotra, Anurag wrote:
> My current setup: Windows Server 2003 on X86 (32bit).
> Apache Tomcat 6.0.16
> Using JVM 1.6.0_06
>
> Current setting for the JVM used by tomcat is as follows:
> Initial Memory pool - 768MB
> Max Memory pool - 1536MB
>
> Is there a way to go beyond 2GB for the max memory pool on the above
> platform?
No, this is about the maximum heap size you can reliably get from a
32-bit JVM on Windows. You probably can't even get close to 2 actual GiB
of heap space (above, you have 1536MiB).
> Would Unix allow me to allocate more memory to tomcat (JVM)?
If you can, it's only coincidental. The real solution is to move to a
64-bit JVM (which, of course, requires a 64-bit OS).
On my dev system (Linux 2.6 kernel with 1GB physical RAM, just minutes
ago), I was able to get a maximum heap size of 2687MiB and an initial
heap size of 100MiB. Attempting to repeat the same command (java
- -Xms100M -Xmx2687M [trivialclass]) failed, so the rules must be based
upon exactly what resources are available when the JVM starts.
Attempting to come anywhere close to 2687MiB with the initial heap size
was not possible. I tried looking for the largest heap size where
initial=maximum and I got 1815MiB as the largest I could muster. See
below for the (crude) script to determine this value.
- -chris
My script (note that MemoryInfo just dumps java.lang.Runtime's basic
memory information).
#!/bin/sh
initial_max=4097
max=${initial_max}
return_value=1
while [ "1" == "$return_value" ] ; do
max=`expr ${max} - 1`
if [ "0" == `expr ${max} % 100` ] ; then
echo "(max=${max})"
fi
java -Xms${max}M -Xmx${max}M MemoryInfo > /dev/null 2>&1
return_value=$?
done
echo
echo Stopped with max=${max}
echo Return value was ${return_value}
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