report: add average CPU consumption

node-report currently produces absolute CPU consumption
from the time since the process started. By making use of
the load time and the current time, convert this into an
average consumption rate which is easily consumable.

PR-URL: #79
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Howard Hellyer <hhellyer@uk.ibm.com>

src/node_report.cc

@@ -106,6 +106,7 @@ static char report_directory[NR_MAXPATH + 1] = ""; // defaults to current workin
 std::string version_string = UNKNOWN_NODEVERSION_STRING;
 std::string commandline_string = "";
 static TIME_TYPE loadtime_tm_struct; // module load time
+static time_t load_time; // module load time absolute
 
 /*******************************************************************************
  * Functions to process node-report configuration options:
@@ -301,6 +302,7 @@ void SetLoadTime() {
   gettimeofday(&time_val, nullptr);
   localtime_r(&time_val.tv_sec, &loadtime_tm_struct);
 #endif
+load_time = mktime(&loadtime_tm_struct);
 }
 
 /*******************************************************************************
@@ -1025,6 +1027,13 @@ static void PrintGCStatistics(std::ostream& out, Isolate* isolate) {
  ******************************************************************************/
 static void PrintResourceUsage(std::ostream& out) {
   char buf[64];
+  double cpu_abs;
+  double cpu_percentage;
+  time_t current_time; // current time absolute
+  time(&current_time);
+  auto uptime = difftime(current_time, load_time);
+  if (uptime == 0)
+    uptime = 1; // avoid division by zero.
   out << "\n================================================================================";
   out << "\n==== Resource Usage ============================================================\n";
 
@@ -1043,6 +1052,9 @@ static void PrintResourceUsage(std::ostream& out) {
     snprintf( buf, sizeof(buf), "%ld.%06ld", stats.ru_stime.tv_sec, stats.ru_stime.tv_usec);
     out << "\n  Kernel mode CPU: " << buf << " secs";
 #endif
+    cpu_abs = stats.ru_utime.tv_sec + 0.000001 * stats.ru_utime.tv_usec + stats.ru_stime.tv_sec + 0.000001 *  stats.ru_stime.tv_usec;
+    cpu_percentage = (cpu_abs / uptime) * 100.0;
+    out << "\n  Average CPU Consumption : "<< cpu_percentage << "%";
     out << "\n  Maximum resident set size: ";
     WriteInteger(out, stats.ru_maxrss * 1024);
     out << " bytes\n  Page faults: " << stats.ru_majflt << " (I/O required) "
@@ -1064,6 +1076,9 @@ static void PrintResourceUsage(std::ostream& out) {
     snprintf( buf, sizeof(buf), "%ld.%06ld", stats.ru_stime.tv_sec, stats.ru_stime.tv_usec);
     out << "\n  Kernel mode CPU: " << buf << " secs";
 #endif
+    cpu_abs = stats.ru_utime.tv_sec + 0.000001 * stats.ru_utime.tv_usec + stats.ru_stime.tv_sec + 0.000001 *  stats.ru_stime.tv_usec;
+    cpu_percentage = (cpu_abs / uptime) * 100.0;
+    out << "\n  Average CPU Consumption : " << cpu_percentage << "%";
     out << "\n  Filesystem activity: " << stats.ru_inblock << " reads "
         << stats.ru_oublock << " writes";
   }