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/python/xen/xend/XendRoot.py

@@ -76,6 +76,10 @@ class XendRoot:
     """Default port xend serves consoles at. """
     console_port_base_default = '9600'
 
+    dom0_min_mem_default = '0'
+
+    dom0_cpus_default = '0'
+
     components = {}
 
     def __init__(self):
@@ -329,6 +333,12 @@ class XendRoot:
     def get_vif_antispoof(self):
         return self.get_config_bool('vif-antispoof', 'yes')
 
+    def get_dom0_min_mem(self):
+        return self.get_config_int('dom0-min-mem', self.dom0_min_mem_default)
+
+    def get_dom0_cpus(self):
+        return self.get_config_int('dom0-cpus', self.dom0_cpus_default)
+
 def instance():
     """Get an instance of XendRoot.
     Use this instead of the constructor.

tools/python/xen/xend/server/SrvDaemon.py

@@ -5,7 +5,6 @@
 ###########################################################
 
 import os
-import os.path
 import signal
 import sys
 import threading
@@ -16,6 +15,7 @@ import re
 import StringIO
 import traceback
 import time
+import glob
 
 from xen.lowlevel import xu
 
@@ -25,6 +25,7 @@ from xen.xend import EventServer; eserver = EventServer.instance()
 from xen.xend.XendError import XendError
 from xen.xend.server import SrvServer
 from xen.xend.XendLogging import log
+from xen.xend import XendRoot; xroot = XendRoot.instance()
 
 import channel
 import controller
@@ -327,6 +328,7 @@ class Daemon:
         return self.cleanup(kill=True)
 
     def run(self):
+        _enforce_dom0_cpus()
         try:
             log.info("Xend Daemon started")
             self.createFactories()
@@ -363,6 +365,32 @@ class Daemon:
         #sys.exit(rc)
         os._exit(rc)
 
+def _enforce_dom0_cpus():
+    dn = xroot.get_dom0_cpus()
+
+    for d in glob.glob("/sys/devices/system/cpu/cpu*"):
+        cpu = int(os.path.basename(d)[3:])
+        if (dn == 0) or (cpu < dn):
+            v = "1"
+        else:
+            v = "0"
+        try:
+            f = open("%s/online" %d, "r+")
+            c = f.read(1)
+            if (c != v):
+                if v == "0":
+                    log.info("dom0 is trying to give back cpu %d", cpu)
+                else:
+                    log.info("dom0 is trying to take cpu %d", cpu)
+                f.seek(0)
+                f.write(v)
+                f.close()
+                log.info("dom0 successfully enforced cpu %d", cpu)
+            else:
+                f.close()
+        except:
+            pass
+
 def instance():
     global inst
     try: