Support for CFS bandwidth limiting.

Also trying to fix NOX cmdline opt, but broken at the moment.

examples/limit.py

@@ -5,19 +5,20 @@ limit.py: example of using link and CPU limits
 """
 
 from mininet.net import Mininet
-from mininet.link import TCIntf, Link
+from mininet.link import TCIntf
 from mininet.node import CPULimitedHost
 from mininet.topolib import TreeTopo
 from mininet.util import custom, quietRun
 from mininet.log import setLogLevel
 from time import sleep
 
-def testLinkLimit( net ):
-    print '*** Testing network bandwidth limit'
-    net.iperf()
+def testLinkLimit( net, bw ):
+    print '*** Testing network %.2f Mbps bandwidth limit' % bw
+    net.iperf( )
 
-def testCpuLimit( net ):
-    print '*** Testing CPU bandwidth limit'
+def testCpuLimit( net, cpu ):
+    pct = cpu * 100
+    print '*** Testing CPU %.0f%% bandwidth limit' % pct
     h1, h2 = net.hosts
     h1.cmd( 'while true; do a=1; done &' )
     h2.cmd( 'while true; do a=1; done &' )
@@ -26,26 +27,24 @@ def testCpuLimit( net ):
     cmd = 'ps -p %s,%s -o pid,%%cpu,args' % ( pid1, pid2 )
     for i in range( 0, 5):
         sleep( 1 ) 
-        print quietRun( cmd )
+        print quietRun( cmd ).strip()
     h1.cmd( 'kill %1')
     h2.cmd( 'kill %1')
 
-def limit():
-    "Example/test of link and CPU bandwidth limits"
-    # 1 Mbps interfaces limited using tc
-    intf1Mbps = custom( TCIntf, bw=1 )
-    # Links consisting of two 10 Mbps interfaces
-    link1Mbps = custom( Link, intf=intf1Mbps, cls2=TCIntf )
-    # Hosts with 30% of system bandwidth
-    host30pct = custom( CPULimitedHost, cpu=.3 )
+def limit( bw=1, cpu=.3 ):
+    """Example/test of link and CPU bandwidth limits
+       bw: interface bandwidth limit in Mbps
+       cpu: cpu limit as fraction of overall CPU time"""
+    intf = custom( TCIntf, bw=1 )
     myTopo = TreeTopo( depth=1, fanout=2 )
-    net = Mininet( topo=myTopo,
-                   link=link1Mbps, 
-                   host=host30pct )
-    net.start()
-    testLinkLimit( net )
-    testCpuLimit( net )
-    net.stop()
+    for sched in 'rt', 'cfs':
+        print '*** Testing with', sched, 'bandwidth limiting'
+        host = custom( CPULimitedHost, sched=sched, cpu=cpu )
+        net = Mininet( topo=myTopo, intf=intf, host=host )
+        net.start()
+        testLinkLimit( net, bw=bw )
+        testCpuLimit( net, cpu=cpu )
+        net.stop()
 
 if __name__ == '__main__':
     setLogLevel( 'info' )