64bit vs. 32bit to get more ram for Virtual Box?

[aharown07]

I'm toying w/the idea of going to 64bit because my machine has 4gb of RAM.... but really only for one reason: I run XP in a Virtual Box and use one app there that wants alot of RAM. I already know from doing some experimenting, that on my 64bit install (which is Ubuntu 9.10), Virtual Box will allow me to grab 2GB for the virtual machine. In 32bit, I can only get 1200 or so (maybe 1500?).

Question is, do I really gain anything for my windows app if I go 64bit? Does it "really" get 2GB in that situation rather than 1 1/2 or so? ...and will my Linux apps have more "left over" to work with also when I've got both going at once?

[SiKing]

This is just my personal opinion, not shared by many. From past experience, the software world is just not ready for 64bit OS, still. First, sooner or later you will find drivers that are not available. Second, there are apps that have not been ported. Lastly, there are benchmarks available specifically for Linux, that say that in a significant number of tests 64bit Linux performed same or worse than an equivalent 32bit setup.
Again, just my two bits!

[aharown07]

Probably could have some some money on that RAM... but even 32bit can use, what, 3gb minus what I have for video ram? (I have discrete video w/512mb I believe)

[SiKing]

32bit can use, what, 3gb

I do not know the exact technical details of how this is done, however ... This is a common misconception, and is true only for base 32-bit Windows install. There is apparently a hack someplace to allow you to address more - I would not know where, as I do not care enough about Windows. On 32-bit Linux, there is page swapping which allows you to address more than the 4GB.

[Karti]

Hi,

Just to give my 2 pennies worth

If you add pae to your 32 bit installation:

http://www.webupd8.org/2009/10/use-more ... buntu.html

You should have the facility to use more ram in your VMs

I installed 32 bit first on my test machine but could not be bothered re-doing it for 64. I had more memory than the system would use, so having had a similar problem when I was going through a Fedora phase I found the PAE method.

Seems to work fine and reduces the the issues I have with windows applications in VBox.

Hope that helps (also think its about 150/200 MB download/install)

K

[Fred]

SiKing wrote:

On 32-bit Linux, there is page swapping which allows you to address more than the 4GB.

It 's called PAE kernel patches for 32 bit. According to recent reports, there is no longer much, if any, speed penalty when used with later kernels. I believe Ubuntu now has available a pre-compiled kernel that contains them.

Fred

[aharown07]

Thanks for the PAE info... maybe I'll do that. Is it difficult to patch? I'll google it.


What I've found so far is this procedure...
$ sudo apt-get update
$ sudo sudo apt-get install linux-headers-server linux-image-server linux-server

Is that really the best way to do it? Want to avoid breaking anything important.

[aharown07]

Nevermind. Looks like the way to do it now is...

sudo apt-get install linux-generic-pae

There were some errors during the install, but it seems to have worked anyway. However, I only see 3.8 GB of RAM. Is that normal?

[aharown07]

Well, those errors apparently mattered because vbox will not run now. Said ...

Kernel driver not installed (rc=-1908)

The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Please reinstall the kernel module by executing

'/etc/init.d/vboxdrv setup'

as root. Users of Ubuntu, Fedora or Mandriva should install the DKMS package first. This package keeps track of Linux kernel changes and recompiles the vboxdrv kernel module if necessary.

When I attempted that I got this in the log...

Error! Your kernel source for kernel 2.6.31-19-generic-pae cannot be found at
/lib/modules/2.6.31-19-generic-pae/build or /lib/modules/2.6.31-19-generic-pae/source.
You can use the --kernelsourcedir option to tell DKMS where it's located.
Failed to install using DKMS, attempting to install without
Makefile:152: *** Error: unable to find the sources of your current Linux kernel. Specify KERN_DIR=<directory> and run Make again. Stop.