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From: Herbert Poetzl (herbert_at_13thfloor.at)
Date: Sun 30 May 2004 - 21:22:58 BST


On Mon, May 31, 2004 at 08:12:21AM +1200, Sam Vilain wrote:
> Herbert Poetzl wrote:

Hi Sam!

> >VSZ is the total sum of the virtual memory
> >
> > (address space) of each process
> >RSS is the total sum of the resident set size
> > (in RAM pages) of each process
> >
> >it's basically the same as in ps auxww
> >only summed up for all processes belonging
> >to a context ...

> And as far as I can tell, sometimes memory is counted more than once;
> ie, copy-on-write pages, like shared C library and binary images all
> count multiple times towards the VSZ total.

that is mainly because the userspace tools sum-up
the values given for each process, so there is
absolutely _no_ way to tell how much is shared ...

> Is this a bug, or is there no simple way to tally the *real*
> VM size of a vserver?

well, neither nor, thing is, to label it correctly
you would use address space, and as every process
has it's own address space, there are the following
options:

 - take the maximum of all processes (lower bound)
 - take the sum of all processes (upper bound)
 - do some page accounting (which is done in vs1.9.x)

none of them are really relevant for anything
(except for limiting them to something sane)
because the 'VM' pages can be:

 - mapped files (caches, executables, libraries)
 - shared memory regions
 - anonymous pages (in memory and swapped out)

best,
Herbert

> --
> Sam Vilain, sam /\T vilain |><>T net, PGP key ID: 0x05B52F13
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