High Memory Utilization on Linux compared to Unix

[PallaviP]

Hi,
I have a java application running on RedHat Linux server. This application polls on a queue for every 30 minutes and takes the message and then parses the FlatFile of 125 MB.
On Unix, the memory utilization is 400MB , but on Linux it is increasing with every transaction starting with 400 MB and reaching to 2.5 GB.
I have tried with the java memory options on Linux with Xmx as 512m(based on the memory it is taking on Unix), it was running fine.
But we cannot deploy this application with the java options in the testing environment.
Any pointers on why it is taking so much memory on linux and how to resolve it? Also can you suggest some monitoring tools which captures object level memory.

Thanks,
Pallavi

[Rubberman]

What version (exactly) are you using? Are you sure it is the jvm (java virtual machine) that is sucking up all the memory? What is the output of the command "free"?

[PallaviP]

Hi,
Linux version : RedHat Enterprise Linux Version 5 Release(update) 5 (RH5.5_0)
java version : 1.6.0_22

$ free
total used free shared buffers cached
Mem: 32961884 16708688 16253196 0 242652 11235972
-/+ buffers/cache: 5230064 27731820
Swap: 18481144 64660 18416484

Iam using Jconsole to monitor the memory usage. Attached is the jconsole output
Jconsole.jpg

[Rubberman]

                      total          used            free  shared       buffers      cached
Mem: 32961884 16708688 16253196 0                242652 11235972
-/+ buffers/cache: 5230064 27731820
Swap: 18481144 64660 18416484

Well, this indicates that most of your memory usage is cached (27GB). This may be expected since you are reading a lot of large (125MB) files, which Linux will cache, expecting to re-read them. However, the OS will purge the data if not accessed again after some time, or if the memory becomes necessary for process data. Unix does not use the same memory caching algorithms as Linux. The only thing that I can suggest is that you monitor the overall system performance and memory usage to see if it stabilizes over time.