[Xen-users] "dynamic memory allocation" for windows guests?

["Peter Gansterer" <peter.gansterer@xxxxxxxxxxxxx>]

Hello,

In our office we would like to do something like "memory overcommitment" or 
rather "dynamic allocation" for a bunch of windows domUs (server 2003 & 2008).

We thought this should be a simple feature, however we did not find any fitting 
solution.
We use Xen 4.2.1 with xl toolstack.

The idea is to use ballooning to dynamically (and automatically) change 
physical memory available to the domUs according to their memory needs.
There was something called "xenballoond" for linux guests before "tmem" was 
integrated, and this seems to be exactly what we're looking for, except that we 
need it for windows domUs.

Is there really no such thing for windows guests, or are we just too stupid to 
find it?
We would be happy about any hints.

If there really is none, then, is there a reason for that?

It seems like a simple thing:
- start a process on each windows guest to monitor memory usage
- if there is spare memory -> tell the hypervisor to lower the mem-target
- if memory is used up, decide upon CPU usage and mem history:
  . idle for some time -> try to free buffers by allocating and freeing blocks
  . loaded -> do nothing or increase mem-target, according to pagefile usage
  . recently increased -> increase mem-target
- If memory is needed quickly, the pagefile will be used temporarily.
- In a trivial implementation, a simple script on dom0 could receive
  the mem-target requests and do the actual "xl mem-set" calls
  (according to some balancing algorithm).

Or is this approach just too naive?

In our scenario (virtual desktops and testservers) there are always idle guests 
wasting memory and not really using it. I suppose there must be a way to 
automatically (if just slowly) shift memory to those in need, and thus reducing 
overall memory requirements.

yours,
- peter.

-- 
Peter Gansterer

PARADIGMA Unternehmensberatung GmbH
MariahilferstraÃe 47/1/3
A-1060 Wien
Tel: 0043-(0)1-585 49 72
http://www.paradigma.net

Firmenbuchnummer: FN 134564 p
Rechtsform: GmbH
Firmenbuchgericht: Handelsgericht Wien

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