Re: [Qemu-devel] RAM overcomittment

[The MoonSeeker]

Le 27 sept. 06 à 23:41, Paul Brook a écrit :

qemu is just like any other application. It is only limited by how much 

virtual memory your OS can provide. ie. if you have sufficient swap you can 

have as many qemu instances using as much memory as you want.

qemu is currently limits each guest to 2Gb ram. This is independent of how 

much physical memory the host has.

Note that modern OS (everything except DOS) generally use all available ram.  

Telling qemu to use more memory than you have physical ram is liable to cause 

heavy swapping.

Ok but some virtual solution like openVZ allow you run more VM than the memory installed. By example, with openVZ I can create 10 Virtual Machine who have a limite fixe to 200 MB but have guaranteed RAM of 20MB. With qemu I need to have 10 X 200MB for VM's + 128 MB host of RAM installed on the work station...

I think we can Save ressource because in the most case, the VM's will never use the 200MB. I think it will be a nice if qemu implemented a tool that let use exceed this limitation.

I can show you an application domain :

For my diploma project, I have to create a network simulator but with these limitation I can't use qemu. Because if would like to simulate 20 workstions I need 20 X 128 MB = 2560 MB of RAM... + host RAM!!! But in the simulation, the VM's never will use all of ressource..

What do you?

Thank you