issue #415: add IPC latency bench.

tests/bench/latch_roundtrip.py

@@ -0,0 +1,38 @@
+"""
+Measure latency of IPC between two local threads.
+"""
+
+import threading
+import time
+
+import mitogen
+
+import ansible_mitogen.process
+ansible_mitogen.process.setup_gil()
+
+X = 20000
+
+def flip_flop(ready, inp, out):
+    ready.put(None)
+    for x in xrange(X):
+        inp.get()
+        out.put(None)
+
+
+ready = mitogen.core.Latch()
+l1 = mitogen.core.Latch()
+l2 = mitogen.core.Latch()
+
+t1 = threading.Thread(target=flip_flop, args=(ready, l1, l2))
+t2 = threading.Thread(target=flip_flop, args=(ready, l2, l1))
+t1.start()
+t2.start()
+
+ready.get()
+ready.get()
+
+t0 = time.time()
+l1.put(None)
+t1.join()
+t2.join()
+print('++', int(1e6 * ((time.time() - t0) / (1.0+X))), 'usec')