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From: Herbert Poetzl (herbert_at_13thfloor.at)
Date: Fri 16 Jul 2004 - 14:43:24 BST


On Fri, Jul 16, 2004 at 03:03:10PM +0200, Gebhardt Thomas wrote:
> Hi,
>
> I'm trying to understand the output of vserver-stat (from vserver 0.29),
> namely the value of VSZ.
>
> The manual page says: VSZ=Number of pages of virtual memory
> Well, actually VSZ is not a number of pages but something that is
> counted in bytes. I got suspicious when I noticed that one of my
> vservers actually had VSZ=3GB while the total system has only
> 1GB RAM + 1 GB swap space.

which is quite normal ...

> It seems that VmSize is computed by adding the vm size
> of all processes running within a specific vserver:
> list->VmSize_total += process->VmSize
> Shared memory is counted multiple times.

that might happen ...

> Does this make sense at all?

yep, it does, but the labeling and the explanations
are wrong alltogether ...

here are some facts:

 - the VM is called AS at kernel level for good reason,
   because it's not virtual memory but Address Space.
 - ps calls it VMZ for whatever reason.
 - vserver-stat is legacy compatible in the output, and
   jackques decided to label it VMZ but display it in
   MB which is just another variation ...
 - the AS can be large, sometimes larger than the
   RAM + SWAP space even for one process (ask SUN about
   that ;)
 - it doesn't make much sense to account address spaces
   only once, just because they point to the same data
   either in memory or swap ...
 - RSS (Resident Set Size) is something completely
   different, it's the ammount of data resident in the
   system memory (available from RAM) ...

HTH,
Herbert

> Cheers, Thomas
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