good virtual memory (VSS) definition needed

[Dan Copeland]

I know the definition of VSS :

This consists of the sum of the virtual set size of all private and shared memory regions used by this process. This metric is not affected by the reference count for those regions which are shared.

But I was hoping for a clearer expalnation of virtual set size.

What is confusing me is that I have many oracle discoverer process that have a VSS 10 times that of their RSS. I'm trying to uderstand what exactly this means before I scream at the application guys for running buggy code.

Any help would be appreciated.

tia,
Frank

[Sridhar Bhaskarla]

Hi Frank,

The difference is that RSS is affected by the reference count of the shared segments while VSS is not.

So if a shared memory segment (X mb) is referenced by 10 procs, the vss of each of the proc is an additive of their private regions + X.

However, the RSS of each proc will be it's private regions + x/10.

So obviously in your case, VSS could be ~10 times than RSS.

-Sri

[Mladen Despic]

The following post contains some relevant information:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x61d4a848deccd61190050090279cd0f9,00.html