tests: make cpu_load.py more random.

tests/soak/cpu_load.py

@@ -4,12 +4,26 @@ Put the machine's CPUs under pressure to increase the likelihood of scheduling
 weirdness. Useful for exposing otherwise difficult to hit races in the library.
 """
 
+import ctypes
 import multiprocessing
+import os
+import time
+
+LIBC = ctypes.CDLL('libc.so.6')
+sched_yield = LIBC.sched_yield
+
 
 def burn():
-    while 1: pass
+    while 1:
+        a, b, c = os.urandom(3)
+        n = int(((ord(a) << 16) |
+                 (ord(b) << 8) |
+                 (ord(c) << 0)) / 1.6)
+        print(n)
+        for x in xrange(n): pass
+        sched_yield()
 
-mul = 2
+mul = 1.5
 count = int(mul * multiprocessing.cpu_count())
 print count