diff options
Diffstat (limited to 'benchtests/bench-skeleton.c')
| -rw-r--r-- | benchtests/bench-skeleton.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/benchtests/bench-skeleton.c b/benchtests/bench-skeleton.c index 7359184..a13ad02 100644 --- a/benchtests/bench-skeleton.c +++ b/benchtests/bench-skeleton.c @@ -22,6 +22,21 @@ #include <time.h> #include <inttypes.h> +volatile unsigned int dontoptimize = 0; +void startup () +{ + /* This loop should cause CPU to switch to maximal freqency. + This makes subsequent measurement more accurate. We need a side effect + to prevent the loop being deleted by compiler. + This should be enough to cause CPU to speed up and it is simpler than + running loop for constant time. This is used when user does not have root + access to set a constant freqency. */ + + int k; + for (k = 0; k < 10000000; k++) + dontoptimize += 23 * dontoptimize + 2; +} + #define TIMESPEC_AFTER(a, b) \ (((a).tv_sec == (b).tv_sec) ? \ ((a).tv_nsec > (b).tv_nsec) : \ @@ -32,6 +47,8 @@ main (int argc, char **argv) unsigned long i, k; struct timespec start, end, runtime; + startup(); + memset (&runtime, 0, sizeof (runtime)); memset (&start, 0, sizeof (start)); memset (&end, 0, sizeof (end)); |