Re: automatic memory ballooning?

[Avi Kivity <avi@redhat.com>]

On 08/17/2009 03:32 PM, Thomas Fjellstrom wrote:
> On Mon August 17 2009, Avi Kivity wrote:
>    
>> On 08/17/2009 01:49 PM, Thomas Fjellstrom wrote:
>>      
>>> One thing I found odd about kvm's ballooning is that it actually seems to
>>> change how much ram the guest has. I really didn't expect "free -m" to
>>> report that the guest only had 64M ram after I manually ballooned the
>>> ram. I was however expecting it just to free ram it wasn't using in the
>>> host. To me, it just doesn't seem to be the same thing. now it'll start
>>> swapping at 64M ram instead of just reallocating the ram it used to have.
>>>        
>> You expectations aren't realistic.  kvm never allocates the ram the
>> guest doesn't use in the first place.
>>      
> Really? So htop is lying to me then?

Of course not.

> I gave 1G ram to a kvm linux guest using
> virtio (disk, net, ballooning), and RES clearly said 1G, and VIRT actually
> said somewhere around 1.3 to 1.6G. It stayed that way for over a day, and the
> guest did nothing the entire time.
>    

VIRT size is pointless, it includes tons of shared libraries which don't 
really affect memory usage.  Try cat /proc/$pid/maps (or pmap $pid) on a 
qemu instance and see.

-- 
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