BTW, this is nice when you have lots of VMs that have a small memory
footprint, and eventually uses more memory. Otherwise it will happen as
Fernando said: eventually the system will begin swapping when the VM tries
to allocate more memory and the guest cannot give =)


On Thu, Jan 16, 2014 at 5:33 PM, Leonardo Carneiro
<chesterma...@gmail.com>wrote:

> 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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