Re: Memory under KVM?

[rek2 <rek2@binaryfreedom.info>]

Hi Thanks for the responses, but look:
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin 
/usr/bin/kvm -S -M pc-0.11 -m 1024 -smp 1 -name vm_hsci -uuid 
52ed4c7c-65e4-325e-0f96-87a5be6d854c -monitor 
unix:/var/run/libvirt/qemu/vm_hsci.monitor,server,nowait -boot c -drive 
file=/var/kvm_images/vm_hsci.img,if=virtio,index=0,boot=on -net 
nic,macaddr=00:16:36:5b:c4:e2,vlan=0,name=nic.0 -net 
tap,fd=16,vlan=0,name=tap.0 -serial pty -parallel none -usb -vnc 
127.0.0.1:0 -k en-us -vga cirrus -soundhw es1370

I have -m 1ith 1024 right?
but if I do a top:
1214m 364m 3360 S    0  4.5  46:55.24 kvm

so is clearly above -m
what could be the issue?
Thanks


is using 1214 at this moment sometimes it goes up a lot more..




On 12/13/09 11:41 AM, Thomas Fjellstrom wrote:
> On Sun December 13 2009, Avi Kivity wrote:
>    
>> On 12/12/2009 10:37 PM, Thomas Fjellstrom wrote:
>>      
>>> I have the opposite happen, when a VM is started, RES is usually lower
>>> than -m, which I find slightly odd. But makes sense if qemu/kvm don't
>>> actually allocate memory from the host till its requested the first
>>> time
>>>        
>> That is the case.
>>
>>      
>>> (if only it
>>> would return some of it afterwards, it would be even better).
>>>        
>> Use the balloon driver to return memory to the host.
>>      
> Will it actually just free the memory and leave the total memory size in the
> VM alone? Last I checked it would just decrease the total memory size, which
> isn't that useful. Sometimes it needs more ram, so its given 512M ram, but
> most of the time can live on 100M or so.
>
>    
>>> I just fully shut down and restarted on of my vms, which is set to use
>>> 128-256 MB ram max. RES is like 72MB on start, and VIRT is 454M. RES
>>> generally gets up around 120MB ram when its doing something.
>>>
>>> One thing I do find a little odd is one of my VMs which is allocated
>>> 512MB ram, has a VIRT of 826MB ram. I didn't realize that qemu had so
>>> many lib dependencies.
>>>        
>> It's not just libraries, it's mostly glibc malloc() allocating huge
>> pools per thread, as well as large thread stacks.
>>
>>      
>>> Due to kvm not supporting giving memory back, besides by
>>> swapping large portions of unused guest ram, my host currently has over
>>> 1G used swap. Not particularly happy with that, but it doesn't seem to
>>> effect performance too much (except that it generally likes to swap
>>> host processes first, guest performance is decent, but host, not so
>>> much).
>>>        
>> The Linux vm prefers anonymous memory, so guests do get an advantage.
>>
>>      
> I think the only thing I'd like to have now is automatic memory return, much
> like vmware server has. It doesn't change what the guest VM sees, it just
> flushes the unused ram back to the host.
>
>