Warning:

The xenpaging code is new and not fully debugged.
Usage of xenpaging can crash Xen or cause severe data corruption in the
guest memory and its filesystems!

Description:

xenpaging writes memory pages of a given guest to a file and moves the
pages back to the pool of available memory.  Once the guests wants to
access the paged-out memory, the page is read from disk and placed into
memory.  This allows the sum of all running guests to use more memory
than physically available on the host.

Usage:

Once the guest is running, run xenpaging with the guest_id and the
number of pages to page-out:

  chdir /var/lib/xen/xenpaging
  xenpaging <guest_id>  <number_of_pages>

To obtain the guest_id, run 'xm list'.
xenpaging will write the pagefile to the current directory.
Example with 128MB pagefile on guest 1:

  xenpaging 1 32768

Caution: stopping xenpaging manually will cause the guest to stall or
crash because the paged-out memory is not written back into the guest!

After a reboot of a guest, its guest_id changes, the current xenpaging
binary has no target anymore. To automate restarting of xenpaging after
guest reboot, specify the number if pages in the guest configuration
file /etc/xen/vm/<guest_name>:

xenpaging=32768

Redo the guest with 'xm create /etc/xen/vm/<guest_name>' to activate the
changes.


Todo:
- implement stopping of xenpaging
- implement/test live migration


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