Estimate CPU core usage in performance tests

This is based on comparing CPU time with elapsed time, which means
that the tests can be heavily influenced by other load on the test
machine.

1 files changed, 43 insertions, 10 deletions

diff --git a/tests/decperf.cxx b/tests/decperf.cxx
index a200e5b4..1fd763e5 100644
--- a/tests/decperf.cxx
+++ b/tests/decperf.cxx
@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#include <sys/time.h>
 
 #include <rdr/Exception.h>
 #include <rdr/FileInStream.h>
@@ -125,10 +126,19 @@ void CConn::serverCutText(const char*, rdr::U32)
 {
 }
 
-static double runTest(const char *fn)
+struct stats
+{
+  double decodeTime;
+  double realTime;
+};
+
+static struct stats runTest(const char *fn)
 {
   CConn *cc;
-  double time;
+  struct timeval start, stop;
+  struct stats s;
+
+  gettimeofday(&start, NULL);
 
   try {
     cc = new CConn(fn);
@@ -146,11 +156,15 @@ static double runTest(const char *fn)
     exit(1);
   }
 
-  time = cc->cpuTime;
+  gettimeofday(&stop, NULL);
+
+  s.decodeTime = cc->cpuTime;
+  s.realTime = (double)stop.tv_sec - start.tv_sec;
+  s.realTime += ((double)stop.tv_usec - start.tv_usec)/1000000.0;
 
   delete cc;
 
-  return time;
+  return s;
 }
 
 static void sort(double *array, int count)
@@ -176,7 +190,8 @@ static const int runCount = 9;
 int main(int argc, char **argv)
 {
   int i;
-  double times[runCount], dev[runCount];
+  struct stats runs[runCount];
+  double values[runCount], dev[runCount];
   double median, meddev;
 
   if (argc != 2) {
@@ -189,19 +204,37 @@ int main(int argc, char **argv)
 
   // Multiple runs to get a good average
   for (i = 0;i < runCount;i++)
-    times[i] = runTest(argv[1]);
+    runs[i] = runTest(argv[1]);
+
+  // Calculate median and median deviation for CPU usage
+  for (i = 0;i < runCount;i++)
+    values[i] = runs[i].decodeTime;
 
-  // Calculate median and median deviation
-  sort(times, runCount);
-  median = times[runCount/2];
+  sort(values, runCount);
+  median = values[runCount/2];
 
   for (i = 0;i < runCount;i++)
-    dev[i] = fabs((times[i] - median) / median) * 100;
+    dev[i] = fabs((values[i] - median) / median) * 100;
 
   sort(dev, runCount);
   meddev = dev[runCount/2];
 
   printf("CPU time: %g s (+/- %g %%)\n", median, meddev);
 
+  // And for CPU core usage
+  for (i = 0;i < runCount;i++)
+    values[i] = runs[i].decodeTime / runs[i].realTime;
+
+  sort(values, runCount);
+  median = values[runCount/2];
+
+  for (i = 0;i < runCount;i++)
+    dev[i] = fabs((values[i] - median) / median) * 100;
+
+  sort(dev, runCount);
+  meddev = dev[runCount/2];
+
+  printf("Core usage: %g (+/- %g %%)\n", median, meddev);
+
   return 0;
 }