doc: add af_packet PMD guide

[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 b044b90..f2d8671 100644 (file)
--- a/examples/performance-thread/common/lthread_timer.h
+++ b/examples/performance-thread/common/lthread_timer.h
@@ -1,34 +1,5 @@
-/*-
- *   BSD LICENSE
- *
- *   Copyright(c) 2015 Intel Corporation. All rights reserved.
- *   All rights reserved.
- *
- *   Redistribution and use in source and binary forms, with or without
- *   modification, are permitted provided that the following conditions
- *   are met:
- *
- *     * Redistributions of source code must retain the above copyright
- *       notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in
- *       the documentation and/or other materials provided with the
- *       distribution.
- *     * Neither the name of Intel Corporation nor the names of its
- *       contributors may be used to endorse or promote products derived
- *       from this software without specific prior written permission.
- *
- *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2015 Intel Corporation
  */
 
 
@@ -46,11 +17,22 @@ 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;
 }