[libvirt] Memory

[Jaromír Červenka]

Hi ozaki-r,

thank you for answer.

So, there is no posibility that guest can request for more memory (max up to
maxMemory) and libvirt/hypervisor/whatever will automatically increase it? I
have to do it manually?

Jaromir.


Dne 17. července 2010 13:49 Ryota Ozaki <ozaki.ryota at gmail.com> napsal(a):

> Hi Jaromír
> 2010/7/17 Jaromír Červenka <cervajz at cervajz.com>:
> > Hello,
> > Could anybody explain me a little bit what is the difference between
> > <currentMemory> and <maxMemory>. I use qemu-kvm hypervisor. When I have
> > 1024MB maxMemory and 512MB of currentMemory, I can see just 512MB in
> guest
> > os (free -m). Is it ok? Does it have something to do with ballooning
> > technique? What happened if guest will needs more memory than 512MB?
>
> In qemu-kvm case, currentMemory means actual amount of memory (or initial
> amount
> of memory) which you allow the guest to use and maxMemory means the maximum
> amount of memory which you (or admin) can increase up to, through libvirt.
>
> With your setting, libvirt launches the VM with 1024MB memory and then
> reduces
> the amount of memory down to 512MB through balloon driver. So 512MB which
> you're seeing in the guest is correct and expected. Because the rest
> of the memory
> has been reclaimed by the hypervisor, the guest cannot gain more memory
> than
> 512MB. The answer for the question--what happened?--is that the guest OS
> will
> behave as same as when it has just 512MB memory and gets memory pressure,
> i.e., reclaim memory, do swapping, or something.
>
> If you want to allow the guest to gain more memory, at first you need
> to increase
> the amount of guest memory through the balloon driver (you know you can
> change
> the amount up to maxMemory at maximum). You can use virsh setmem for that.
>
>   ozaki-r
>
> > Thank you for answers :)
> > Kind regards,
> >
> > Jaromír Červenka
> > Official openSUSE community member
> > Web: http://www.cervajz.com/
> > Jabber: cervajz at cervajz.com
> > MSN: jara.cervenka at seznam.cz
> > Tel.: +420 607 592 687
> > Alt. e-mails:
> > jaromir.cervenka at opensuse.org,
> > jaromir.cervenka at speel.cz
> >
> > --
> > libvir-list mailing list
> > libvir-list at redhat.com
> > https://www.redhat.com/mailman/listinfo/libvir-list
> >
>
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