This patch does 2 jobs:

- Enforce the number of CPUs dom0 will take. See the new variable
"dom0-cpus" in xend-config.sxp (you will want to set this variable to
1 on SMP systems)

- Balloon out dom0 memory when creating domU, if there is not enough
free memory. The lowest level we will balloon out is configured via
the new variable "dom0-min-mem" in xend-config.sxp


I still have a doubt: where to put the code to enforce dom0-cpus. At
the moment I put it into
python/xen/xend/server/SrvDaemon.py, and hopefully that is resonable
enough. Any comment?



Signed-off-by: Nguyen Anh Quynh <aquynh@gmail.com>

tools/examples/xend-config.sxp

@@ -44,3 +44,11 @@
 # Setup script for enbd-backed block devices
 (block-enbd block-enbd)
 
+# Dom0 will balloon out when needed to free memory for domU.
+# dom0-min-mem is the lowest memory level (in MB) dom0 will get down to.
+# If dom0-min-mem=0, dom0 will never balloon out.
+(dom0-min-mem 0)
+
+# In SMP system, dom0 will use only CPUs in range [1,dom0-cpus]
+# If dom0-cpus = 0, dom0 will take all cpus available
+(dom0-cpus 0)