[vbox-dev] Virtual box processes memory allocation question from Windows XP SP3 user

Ramshankar ramshankar.venkataraman at oracle.com
Wed Aug 28 09:52:29 PDT 2013

Hi Janusz,

Are you sure you are looking at the right VirtualBox process? At least 
on *nix host systems both the VM selector GUI and the actual VM 
processes are both called "VirtualBox".

Also, are you  sure you are not mixing virtual reservations in the guest 
with actual allocated memory?

In any case, what VirtualBox does, in the default case, is to -not- 
allocate upfront the entire RAM you have configured for the guest. It 
does it in a lazy fashion, as and when the guest touches its memory. 
Windows  guests normally on boot/shortly after scrub its memory in some 
way while with other guests like Linux you can observe the actual 
allocated memory of the guest growing over time depending on the actual 
usage. The guest memory is allocated from kernel space and mapped into 
the userland process.

As for the CPU, we don't do anything special, we do however try to play 
as nice as possible with the host scheduler interrupting guest execution 
when required.

Hope this helps,


On 08/28/13 04:37 PM, Mgr. Janusz Chmiel wrote:
> Dear core developers,
> I have one big question on You.
> I Am wondering, why i can use whole virtual machine with Windows XP 
> SP3 and The process, VirtualBox.exe is allocating only 66 MB after 4 
> hours of running.
> My XP virtual machine is containing standard XP installation and 
> Seamonkey WEB browser, this standalone process is allocating more than 
> 140 MB, so whole XP can allocate approximately 330 MB.
> Does Virtualbox and its dependent modules allocating Windows virtual 
> memory by using special Kernel32.dll API calls?
> Or Virtualbox is using standalone temporary files or files to save data?
> Because i Am wondering, why Yours virtualisation solution can run for 
> so long time without memory leaks and without system slowdown. Even 
> Windows XP, which runs inside virtual computer can run for me for more 
> than 12 hours of intesive work.
> Would You explain me this positive feature for me like A advanced user?
> I know, that whole source code is public available, but this complex 
> C++ language code is too complex for me to understand it, so i would 
> like to hear The explanation from You like a developer.
> So i could imagine, how yours amazing virtualisation tool work.
> I hope, that somebody of us, who is engaged in The deep of C source 
> code of this project would give me The explanation.
> My last plea?
> Why Yours virtualisation tool so soft to CPU, that i can use it for a 
> long time and my CPU fan is working at The lovest speed?
> I love all this features, but i would like to know, why is it working 
> so smoothly?
> Thank You very much for Yours time, patience and for Yours answers.
> Zpráva neobsahuje viry.
> Zkontrolováno AVG - www.avg.cz <http://www.avg.cz>
> Verze: 2013.0.3392 / Virová báze: 3211/6614 - Datum vydání: 27.8.2013
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