[vbox-dev] Releasing memory to the host

Alexander Rudnev alexander.rudnev at oracle.com
Fri Nov 20 14:47:58 GMT 2020

Hi Vivek,

VirtualBox allocates physical (non-swappable) memory with the amount set 
in VM settings. This memory can't be returned back to the host nor fully 
nor partially. Why don't you want to specify 1Gb of RAM in VM settings 
having your VM requires less? That seems as a solution to me.

On 20/11/2020 14:10, Vivek Thakkar wrote:
> Hi,
> We are running a 32 bit linux guest on a 64 bit windows host using 
> VBox.  Although the guest is configured with 4 GB RAM, it usually 
> consumes around 700-800 MB in steady state. However, during bootup the 
> guest may use around 1.5 GB RAM. Even otherwise, we expect that there 
> would be some peak memory usage that may happen in the guest but in a 
> steady state very less memory would be used.
> Currently, the VBox doesn't seem to free up the memory (allocated for 
> the guest context) to the host even if the peak load has passed as there 
> is no guest to host interface that would tell the hypervisor to free up 
> the memory. If we are okay with paravirtualization of the guest, would 
> it be possible to modify VBox to release this memory to the host? How 
> can we do it - any pointers on this would be really helpful.
> Our main objective is to release the memory pressure on the host, so 
> that it doesn't impact the system performance (other apps on the host 
> can use the extra memory for its allocations without paging).
> Regards,
> Vivek
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Alexander Rudnev | VirtualBox | work  +7 (812) 334 60 01 | cell +7 (921) 
951 82 04
Oracle Development SPB
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