X-Git-Url: http://git.droids-corp.org/?a=blobdiff_plain;f=examples%2Fperformance-thread%2Fcommon%2Flthread_timer.h;h=7c03d67369abbff4bd835e27562c2afc010c52a7;hb=1e6d5a960820a377e2453a13c8cd2e6797dc2f76;hp=b044b902b1e1c24be22c1fb6ad0a2dc5e3861637;hpb=9aba2a3f3d8b2376589b636fe5ef5e8a86ecb0ee;p=dpdk.git

diff --git a/examples/performance-thread/common/lthread_timer.h b/examples/performance-thread/common/lthread_timer.h
index b044b902b1..7c03d67369 100644
--- a/examples/performance-thread/common/lthread_timer.h
+++ b/examples/performance-thread/common/lthread_timer.h
@@ -46,11 +46,22 @@ extern "C" {
 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;
 }