Re: Memory under KVM?

[Thomas Fjellstrom <tfjellstrom@shaw.ca>]

On Tue December 15 2009, Avi Kivity wrote:
> On 12/13/2009 07:16 PM, Thomas Fjellstrom wrote:
> >> Linux usually keeps very little RAM free (it's kept as cache).  So
> >> there has to be some action on the part of the host to get the guest
> >> to free things.  For Windows guests you can use ksm to reclaim free
> >> memory (since Windows will zero it).
> >
> > I'm waiting for 2.6.32 to hit Debian Sid before I start playing with
> > ksm (I don't think its in 2.6.31).
> >
> > The problem is it should be automatic. The balloon driver itself or
> > some other mechanism should be capable of noticing when it can free up
> > a bunch of guest memory. I can't be bothered to manually sit around and
> > monitor memory usage on my host so I can then go into virt-manager to
> > reduce memory to each guest.
> 
> That should be pretty easy though it will have an effect on guest
> performance.
> 

As long as its only done after an appropriately long idle period (ie: theres 
been X MB's free for a long time, give it back), I can't see it harming 
performance too much. At least not more than setting ram too low when 
manually (de)ballooning memory.

-- 
Thomas Fjellstrom
tfjellstrom@shaw.ca