VirtualBox suddenly eats gigabytes of memory

Question

EDIT

The original question had lots of speculation but it is all much simpler. See my own answer and this reported bug.

I leave the original question in case someone is having similar issues and helps them find this issue.

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I have been working with a VirtualBox Ubuntu 14.04 VM hosted on Windows 7. The machine works ok but quite often the VirtualBox process suddenly starts to claim huge amounts of memory for no apparent reason. I have not been able to reproduce the error in a consistent manner, but it happens every few hours, or sometimes just after a few minutes. Here are some more details:

• I am using current VirtualBox version (4.3.16) but I have also tried older (4.3.12) and beta (4.3.17). I have the problem with all of them.
• I have tried assigning different amounts of RAM to the VM. I have the problems with all of them. I have tried assigning 512MB, 768MB and 1GB. My host has 4GB in total.
• The guest OS system monitor does not show significant changes in the amount of memory used.
• This can happen when I am working with the machine or when it is idle for hours. I can't find a single cause. Sometimes it happens when I open the Ubuntu Software Center, but I have used it many times without issues. Sometimes it happens when I just boot up the machine and don't do anything with it at all. Sometimes it happens after an hour developing with Eclipse. Sometimes it doesn't happen in the whole day.
• Sometimes the memory claimed by the VirtualBox process roughly doubles, all of the sudden. Usually I start with around 700 MB used, and suddenly it uses about 1.4 GB. Other times it grows slowly but steadly, and after a minute or so the process has more than 2 GB of memory and the system becomes really slow.
• I have tried different VM settings, different amounts of video memory, etc.
• I have created several VM to see if there's something wrong with my main one. It can happen before and after installing Ubuntu updates in all the 3 VMs I tried (different software installed in all of them).

Am I the only one with this problem?

Answer 1

I got it!

There is a huge memory leak in the host system when the Ubuntu main menu (Unity lens) is displayed. It eats approx. 100 MB every second. Strangely enough, this is not seen in the guest system monitor.

The work around is disabling 3d acceleration in Virtual Box. I can live with that but it's obviously a serious memory leak so I guess I will report a bug.

I would still be interested in seeing if other people are having this problem too.

I am using VirtualBox v4.3.18 now.