Modify the calculation methods in driver and add comments in post_pocessing function

test/cpp/qps/driver.cc

@@ -134,36 +134,38 @@ static bool IsSuccess(const Status& s) {
 
 // Postprocess ScenarioResult and populate result summary.
 static void postprocess_scenario_result(ScenarioResult* result) {
+  // Get latencies from ScenarioResult latencies histogram and populate to
+  // result summary.
   Histogram histogram;
   histogram.MergeProto(result->latencies());
-
-  auto time_estimate = average(result->client_stats(), WallTime);
-  auto qps = histogram.Count() / time_estimate;
-  auto qps_per_server_core = qps / sum(result->server_cores(), Cores);
-
-  result->mutable_summary()->set_qps(qps);
-  result->mutable_summary()->set_qps_per_server_core(qps_per_server_core);
   result->mutable_summary()->set_latency_50(histogram.Percentile(50));
   result->mutable_summary()->set_latency_90(histogram.Percentile(90));
   result->mutable_summary()->set_latency_95(histogram.Percentile(95));
   result->mutable_summary()->set_latency_99(histogram.Percentile(99));
   result->mutable_summary()->set_latency_999(histogram.Percentile(99.9));
 
-  auto server_system_time = 100.0 *
+  // Calculate qps and cpu load for each client and then aggregate results for all clients 
-                            sum(result->server_stats(), ServerSystemTime) /
+  double qps = 0;
-                            sum(result->server_stats(), ServerWallTime);
+  double client_system_cpu_load = 0, client_user_cpu_load = 0;
-  auto server_user_time = 100.0 * sum(result->server_stats(), ServerUserTime) /
+  double server_system_cpu_load = 0, server_user_cpu_load = 0;
-                          sum(result->server_stats(), ServerWallTime);
+  for (size_t i = 0; i < result->client_stats_size(); i++){
-
+    auto client_stat = result->client_stats(i);
-  auto client_system_time = 100.0 * sum(result->client_stats(), SystemTime) /
+    qps += client_stat.latencies().count() / client_stat.time_system();
-                            sum(result->client_stats(), WallTime);
+    client_system_cpu_load += client_stat.time_system() / client_stat.time_elapsed();
-  auto client_user_time = 100.0 * sum(result->client_stats(), UserTime) /
+    client_user_cpu_load += client_stat.time_user() / client_stat.time_elapsed();
-                          sum(result->client_stats(), WallTime);
+  }
-
+  // Calculate cpu load for each server and then aggregate results for all servers
-  result->mutable_summary()->set_server_system_time(server_system_time);
+  for (size_t i = 0; i < result->server_stats_size(); i++){
-  result->mutable_summary()->set_server_user_time(server_user_time);
+    auto server_stat = result->server_stats(i);
-  result->mutable_summary()->set_client_system_time(client_system_time);
+    server_system_cpu_load += server_stat.time_system() / server_stat.time_elapsed();
-  result->mutable_summary()->set_client_user_time(client_user_time);
+    server_user_cpu_load += server_stat.time_user() / server_stat.time_elapsed();
+  }
+  result->mutable_summary()->set_qps(qps);
+  // Populate the percentage of cpu load to result summary.
+  result->mutable_summary()->set_server_system_time(100 * server_system_cpu_load);
+  result->mutable_summary()->set_server_user_time(100 * server_user_cpu_load);
+  result->mutable_summary()->set_client_system_time(100* client_system_cpu_load);
+  result->mutable_summary()->set_client_user_time(100 * client_user_cpu_load);
 
   // For Non-linux platform, get_cpu_usage() is not implemented. Thus,
   // ServerTotalCpuTime and ServerIdleCpuTime are both 0.
@@ -176,6 +178,9 @@ static void postprocess_scenario_result(ScenarioResult* result) {
     result->mutable_summary()->set_server_cpu_usage(server_cpu_usage);
   }
 
+  // Calculate and populate successful request per second and failed requests
+  // per seconds to result summary.
+  auto time_estimate = average(result->client_stats(), WallTime);
   if (result->request_results_size() > 0) {
     int64_t successes = 0;
     int64_t failures = 0;
@@ -193,6 +198,9 @@ static void postprocess_scenario_result(ScenarioResult* result) {
                                                               time_estimate);
   }
 
+  // Fill in data for other metrics required in result summary
+  auto qps_per_server_core = qps / sum(result->server_cores(), Cores);
+  result->mutable_summary()->set_qps_per_server_core(qps_per_server_core);
   result->mutable_summary()->set_client_polls_per_request(
       sum(result->client_stats(), CliPollCount) / histogram.Count());
   result->mutable_summary()->set_server_polls_per_request(