Re: [Xen-users] Question about memory management of Xen

[Luca Manganelli <luca_manganelli@xxxxxxxxxxxxxxxx>]

Mark Williamson wrote:
> If you have 32-bit, non-PAE Xen then 4GB host ram is supported.
> For 32-bit PAE Xen it's more - maybe around 16GB, I think?
> For 64-bit Xen it's more again.
>   
So, to have more than 4GB on a 32bit:
domain0 --> kernel xen with PAE enabled
vmX --> these VMs have less than 4GB. Must I install the PAE enabled 
kernel in them, too?
> For PV guests:
> the guest knows how much memory it has been allocated.  If it wants to 
> grow towards its maximum then it requests more memory from Xen and 
> incorporates it into its memory space.  If it wants to shrink, then it 
> unmaps that memory and returns it to Xen.
> From the rest of the OS, this looks like a driver which is just 
> allocating and freeing memory as the domain shrinks and grows.
>   
So, a VM can release free memory to system RAM, is it true? On VMWARE 
it's never released, it only grows.
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