Virtualbox has a feature called Memory Ballooning, accessible via cli tool,
the vboxmanage.
AFAIK, this feature allows the guest to only allocate the memory that it's
actually using, and allocate more as needed, up to the total amount of
memory defined in the guest configuration. It's pretty much what vbox does
with dynamic disks (starts small, and grow as needed).
https://www.virtualbox.org/manual/ch04.html#guestadd-balloon
I'm not 100% sure about this. Anyone confirms?
On Thu, Jan 16, 2014 at 2:23 PM, Ritesh Raj Sarraf <r...@researchut.com>wrote:
> On Thursday 16 January 2014 12:38 PM, Fernando Cassia wrote:
> > On Wed, Jan 15, 2014 at 3:56 PM, Ritesh Raj Sarraf <r...@researchut.com>
> wrote:
> >> >
> >> > This would effectively allow saving some RAM, which as in today's
> config
> >> > in VBox, might be blocked and idly wasted.
> > It is not wasted. It is reserved. If it's not reserved then another
> > app on the host OS could take it. And then what will happen when the
> > guest OS *thinks* it has some memory available but in fact does not?
> > Then the host OS would begin swapping to disk. Then performance will
> > suck, processes will hang on the guest OS, also slowing the host OS to
> > a crawl with all that memory swapping going on.
> >
> > If you are memory constrained, you shouldn't be doing virtualization
> > to begin with.
> >
> > Just my $0.02, on a personal level, speaking just as a end user.
>
> Given that most modern OSs do mem hotplug, I was wondering if the
> upper/lower limit approach would make any sense. This gives an edge to
> run more VMs, parallel. Ofcourse, you'll need a VBox monitor to detect
> lower limit consumption of RAM in Guest VMs, and see on the Host, if it
> can reserve any additional.
>
> But yes, once if the Linux Host goes into paging to disk, it'd go all ugly.
>
> --
> Given the large number of mailing lists I follow, I request you to CC me
> in replies for quicker response
>
>
>
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