Imported Upstream version 17.05

[deb_dpdk.git] / examples / performance-thread / common / lthread_timer.h

diff --git a/examples/performance-thread/common/lthread_timer.h b/examples/performance-thread/common/lthread_timer.h
index b5e6fb0..7c03d67 100644 (file)
--- a/examples/performance-thread/common/lthread_timer.h
+++ b/examples/performance-thread/common/lthread_timer.h
@@ -35,6 +35,10 @@
 #ifndef LTHREAD_TIMER_H_
 #define LTHREAD_TIMER_H_
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "lthread_int.h"
 #include "lthread_sched.h"
 
@@ -42,11 +46,22 @@
 static inline uint64_t
 _ns_to_clks(uint64_t ns)
 {
-       unsigned __int128 clkns = rte_get_tsc_hz();
+       /*
+        * clkns needs to be divided by 1E9 to get ns clocks. However,
+        * dividing by this first would lose a lot of accuracy.
+        * Dividing after a multiply by ns, could cause overflow of
+        * uint64_t if ns is about 5 seconds [if we assume a max tsc
+        * rate of 4GHz]. Therefore we first divide by 1E4, then
+        * multiply and finally divide by 1E5. This allows ns to be
+        * values many hours long, without overflow, while still keeping
+        * reasonable accuracy.
+        */
+       uint64_t clkns = rte_get_tsc_hz() / 1e4;
 
        clkns *= ns;
-       clkns /= 1000000000;
-       return (uint64_t) clkns;
+       clkns /= 1e5;
+
+       return clkns;
 }
 
 
@@ -75,5 +90,8 @@ _timer_stop(struct lthread *lt)
        }
 }
 
+#ifdef __cplusplus
+}
+#endif
 
 #endif /* LTHREAD_TIMER_H_ */