Fixing Xen Error:(12,‘Cannot allocate memory’)

# xm create lexus

Cann't create lexus......

Error:(12,‘Cannot allocate memory’)   //提示无法分配内存，内存明显不足

#echo 3 > /proc/sys/vm/drop_caches  //释放内存

# xm info |grep memory
total_memory           : 8191
free_memory            : 4315

## xm list  Domain-0     
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0      512     4 r----- 466224.4

# xm mem-set Domain-0 512