Select better arguments

tools/run_tests/performance/scenario_config.py

@@ -156,7 +156,7 @@ def _ping_pong_scenario(name, rpc_type,
 
   # Optimization target of 'throughput' does not work well with epoll1 polling
   # engine. Use the default value of 'blend'
-  optimization_target = 'blend'
+  optimization_target = 'throughput'
 
   if unconstrained_client:
     outstanding_calls = outstanding if outstanding is not None else OUTSTANDING_REQUESTS[unconstrained_client]
@@ -175,6 +175,7 @@ def _ping_pong_scenario(name, rpc_type,
     scenario['client_config']['outstanding_rpcs_per_channel'] = 1
     scenario['client_config']['client_channels'] = 1
     scenario['client_config']['async_client_threads'] = 1
+    optimization_target = 'latency'
 
   optimization_channel_arg = {
     'name': 'grpc.optimization_target',