Question

I currently work in a Weblogic Java EE project, where from time to time the application executes a Perl script to do some batch jobs. In the application the script is getting invoked as

Process p = Runtime.getRuntime().exec(cmdString);

Though it is a dangerous way to run, but it was working properly until we had a requirement to execute the script synchronously under a for loop. After a couple of run we are getting
java.io.IOException: Not enough space as probably OS is running out of virtual memory while exec-ing under a for loop. As a result we are not able to run the script at all in the server.

I am desperately looking for a safer and better way to run the Perl script, where we don’t need to fork the parent process, or at-least not to eat-up all swap space!

The spec is as follows:

Appserver - Weblogic 9.52  
JDK - 1.5   
OS - SunOS 5.10 
Sun-Fire-T200

Answer 1

If you want to keep your code unchanged and have enough disk free space, you can just add a sufficiently large swap area to your OS.

Assuming you need 10 GB, here is how you do it with UFS:

mkfile 10g /export/home/10g-swap
swap -a /export/home/10g-swap
echo "/export/home/10g-swap - - swap - no -" >> /etc/vfstab

If you use ZFS, that would be:

zfs create -V 10gb rpool/swap1
swap -a /dev/zvol/dsk/rpool/swap1

Don’t worry about that large a swap, this won’t have any performance impact as the swap will only be used for virtual memory reservation, not pagination.

Otherwise, as already suggested in previous replies, one way to avoid the virtual memory issue you experience would be to use a helper program, i.e. a small service that your contact through a network socket (or a higher level protocol like ssh) and that executes the perl script “remotely”.

Note that the issue has nothing to do with a 32-bit or 64-bit JVM, it is just Solaris doesn’t overcommit memory and this is by design.