fix aggregator benchmark

```
== warmup ==
1 2.564000169513747e-06
1000 0.0003257179996580817
10000 0.003369195001141634
100000 0.03210452299936151
1000000 0.31846129199948336
10000000 3.215345189999425

== noop ==
1 1.984999471460469e-06
1000 0.00032863300111785065
10000 0.0032671120006853016
100000 0.03219444500064128
1000000 0.32194886400066025
10000000 3.2092841119992954

== sum ==
1 1.1226000424358062e-05
1000 0.000391326000681147
10000 0.0033218999997188803
100000 0.031986795000193524
1000000 0.32090956100000767
10000000 3.2212803769998573

== fake ==
1 4.441999408300035e-06
1000 0.0003171700009261258
10000 0.0033069499986595474
100000 0.03180618599981244
1000000 0.3161616289999074
10000000 3.176653272999829

```

lib/carbon/tests/benchmark_aggregator.py

@@ -3,7 +3,6 @@
 
 from carbon.aggregator.processor import AggregationProcessor, RuleManager
 from carbon.aggregator.buffers import BufferManager
-from carbon.tests.util import print_stats
 from carbon.conf import settings
 from carbon import state
 
@@ -43,21 +42,23 @@ def _bench_aggregator(name):
     buf = None
     for n in [1, 1000, 10000, 100000, 1000000, 10000000]:
         processor = AggregationProcessor()
-        processor.process(METRIC, (now, 1))
+        for x in processor.process(METRIC, (now, 1)):
+            pass
 
         def _process():
             processor.process(METRIC, (now + _process.i, 1))
             if (_process.i % FREQUENCY) == 0 and buf is not None:
-                buf.compute_values()
+                buf.compute_value()
             _process.i += 1
         _process.i = 0
 
         if buf is None:
-            buf = BufferManager.get_buffer(METRIC_AGGR, 1, None)
-
+            buf = BufferManager.buffers.get(METRIC_AGGR)
         t = timeit.timeit(_process, number=n)
-        buf.close()
-        print_stats(n, t)
+
+        if buf:
+            buf.close()
+        print(n, t)
     print("")