High Memory usage in C++ application rebuild on Itanium

[Sourin]

Hi,
While migrating a C++ application (using Oracle as DB) from HP-UX PA-RISC to HP-UX Itanium processor we see an enormous increase of physical memory requirement. In our migration we only recompiled and rebuild the same applicaiton. just to give an idea below are the RSS/VSS for the same program on PA-RISC (PA-64) and on IA-64

On PA-64
Text RSS/VSS:256kb/652kb Data RSS/VSS:2.4mb/3.2mb Stack RSS/VSS:112kb/112kb
Shmem RSS/VSS: 18mb/ 18mb Other RSS/VSS:111mb/285mb

On Ia-64
Text RSS/VSS:492kb/592kb Data RSS/VSS:199mb/234mb Stack RSS/VSS:104kb/104kb
Shmem RSS/VSS: 12mb/ 19mb Other RSS/VSS: 87mb/544mb

Can someone help me with what went wrong here and what should be checked.

[Dennis Handly]

You will need to use size(1) on every load module to see if this is due to the initial allocation.

Also, how much heap space are you using for the two architectures?
It seems the Data VSS has an awfully big increase.

[Sourin]

doing size of the load modules does not give much insight. It is pretty much the same in PA-RISC. can you give me an elaboate description of what exactly to look for.

[Dennis Handly]

>doing size of the load modules does not give much insight. It is pretty much the same in PA-RISC.

Then the majority of your memory use is dynamic, through the heap or possibly shared memory.

>can you give me an elaborate description of what exactly to look for.

You need to profile the amount of heap usage. gdb has heap checking and profiling reports.