Re: [Qemu-devel] QEMU_TMPDIR temp folder for KQEMU for Windows.

[Filip Navara]

Francois Rioux wrote:

> Filip,
>  
> I'm not trying to put the guest in ram.  As you state, let's Windows 
> manage its whole memory, paging and swapping.  I agree it would be as 
> dumb as setting up a ramdisk to put the swapfile. Let's not trying to 
> outsmart the OS.

There's slight misunderstaning there. What I'm saying is that on 
QEMU/Windows there's no "big hidden file containing the RAM of the 
virtual machine", it's simply stored in the host RAM (and the host OS 
can decide to page out parts of it to disk - to pagefile.sys, or 
whatever is setup - but it may not do so if you have enough physical 
memory available).

On other platforms where QEMU runs there's the famous "big hidden file 
containing the RAM of the virtual machine" and it's mapped into memory 
and used as the storage of guest RAM. Whenever the OS decides the 
in-memory contents are synced with the on-disk file. Actually I don't 
understand the benefits of putting it on real ramdisk (...but /dev/shm, 
or actually TMPFS is not *REAL RAMDISK* since it grows and shrink based 
on the contents and the pages can be be swapped out ... so in a way it 
does the same thing as we accomplish on Windows with pure virtual memory 
allocation).

Maybe I haven't explained the details correctly (and I'm not exactly 
sure about them on the *nix side of things), but the point is that no 
such file containing the guest RAM is present on Windows.

- Filip