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

Subject: Re: [Xen-users] Question about memory management of Xen
From: Luca Manganelli <luca_manganelli@xxxxxxxxxxxxxxxx>
Date: Thu, 23 Aug 2007 11:25:40 +0200
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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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