ceph/src/rocksdb/third-party/folly/folly/chrono/Hardware.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5
   6 #pragma once
   7
   8 #include <folly/Portability.h>
   9
  10 #include <chrono>
  11 #include <cstdint>
  12
  13 #if _MSC_VER && (defined(_M_IX86) || defined(_M_X64))
  14 extern "C" std::uint64_t __rdtsc();
  15 #pragma intrinsic(__rdtsc)
  16 #endif
  17
  18 namespace folly {
  19
  20 inline std::uint64_t hardware_timestamp() {
  21 #if _MSC_VER && (defined(_M_IX86) || defined(_M_X64))
  22   return __rdtsc();
  23 #elif __GNUC__ && (__i386__ || FOLLY_X64)
  24   return __builtin_ia32_rdtsc();
  25 #else
  26   // use steady_clock::now() as an approximation for the timestamp counter on
  27   // non-x86 systems
  28   return std::chrono::steady_clock::now().time_since_epoch().count();
  29 #endif
  30 }
  31
  32 } // namespace folly
  33