Create Xen virtual machine prompt error out of memory

Today when the machine tool creates a new Xen virtual machine prompts the following error

' Out of memory ', ' xc_dom_boot_mem_init:can ' t allocate low memory for Domainn '

Not enough memory to allocate memory? My machine tool clearly has 8G more memory unused ah, and before the creation of other virtual machine did not this error.
Google, the original machine will be the memory of the cache is over, so unable to allocate memory to the new virtual machines, limited the use of computer tools can be.

The code is as follows	Copy Code
XM Mem-set 0 512