Move CPU limit into net, to be reused in future unit tests

examples/limit.py

@@ -8,33 +8,17 @@
 from mininet.link import TCIntf
 from mininet.node import CPULimitedHost
 from mininet.topolib import TreeTopo
-from mininet.util import custom, quietRun
+from mininet.util import custom
 from mininet.log import setLogLevel
-from time import sleep
+
 
 def testLinkLimit( net, bw ):
     "Run bandwidth limit test"
     print '*** Testing network %.2f Mbps bandwidth limit' % bw
     net.iperf( )
 
-def testCpuLimit( net, cpu ):
-    "run CPU limit test"
-    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 &' )
-    pid1 = h1.cmd( 'echo $!' ).strip()
-    pid2 = h2.cmd( 'echo $!' ).strip()
-    cmd = 'ps -p %s,%s -o pid,%%cpu,args' % ( pid1, pid2 )
-    # It's a shame that this is what pylint prefers
-    for _ in range( 5 ):
-        sleep( 1 )
-        print quietRun( cmd ).strip()
-    h1.cmd( 'kill %1')
-    h2.cmd( 'kill %1')
 
-def limit( bw=10, cpu=.4 ):
+def limit( bw=10, cpu=.1 ):
     """Example/test of link and CPU bandwidth limits
        bw: interface bandwidth limit in Mbps
        cpu: cpu limit as fraction of overall CPU time"""
@@ -46,7 +30,7 @@ def limit( bw=10, cpu=.4 ):
         net = Mininet( topo=myTopo, intf=intf, host=host )
         net.start()
         testLinkLimit( net, bw=bw )
-        testCpuLimit( net, cpu=cpu )
+        net.runCpuLimitTest( cpu=cpu )
         net.stop()
 
 def verySimpleLimit( bw=150 ):

mininet/net.py

@@ -530,6 +530,42 @@ def iperf( self, hosts=None, l4Type='TCP', udpBw='10M' ):
         output( '*** Results: %s\n' % result )
         return result
 
+    def runCpuLimitTest( self, cpu, duration=5 ):
+        """run CPU limit test with 'while true' processes.
+        cpu: desired CPU fraction of each host
+        duration: test duration in seconds
+        returns a single list of measured CPU fractions as floats.
+        """
+        pct = cpu * 100
+        info('*** Testing CPU %.0f%% bandwidth limit\n' % pct)
+        hosts = self.hosts
+        for h in hosts:
+            h.cmd( 'while true; do a=1; done &' )
+        pids = [h.cmd( 'echo $!' ).strip() for h in hosts]
+        pids_str = ",".join(["%s" % pid for pid in pids])
+        cmd = 'ps -p %s -o pid,%%cpu,args' % pids_str
+        # It's a shame that this is what pylint prefers
+        outputs = []
+        for _ in range( duration ):
+            sleep( 1 )
+            outputs.append( quietRun( cmd ).strip() )
+        for h in hosts:
+            h.cmd( 'kill %1' )
+        cpu_fractions = []
+        for test_output in outputs:
+            # Split by line.  Ignore first line, which looks like this:
+            # PID %CPU COMMAND\n
+            for line in test_output.split('\n')[1:]:
+                r = r'\d+ (\d+\.\d+)'
+                m = re.search( r, line )
+                if m is None:
+                    error( '*** Error: could not extract CPU fraction: %s\n' %
+                           line )
+                    return None
+                cpu_fractions.append( float( m.group( 1 ) ) )
+        output( '*** Results: %s\n' % cpu_fractions )
+        return cpu_fractions
+
     # BL: I think this can be rewritten now that we have
     # a real link class.
     def configLinkStatus( self, src, dst, status ):