-/*-
- * 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
*/
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;
}