ceph/src/common/Cycles.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2014 UnitedStack <haomai@unitedstack.com>
   7  *
   8  * Author: Haomai Wang <haomaiwang@gmail.com>
   9  *
  10  * This is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License version 2.1, as published by the Free Software
  13  * Foundation.  See file COPYING.
  14  *
  15  */
  16 /* Copyright (c) 2011-2014 Stanford University
  17  *
  18  * Permission to use, copy, modify, and distribute this software for any
  19  * purpose with or without fee is hereby granted, provided that the above
  20  * copyright notice and this permission notice appear in all copies.
  21  *
  22  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR(S) DISCLAIM ALL WARRANTIES
  23  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  24  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL AUTHORS BE LIABLE FOR
  25  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  26  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  27  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  28  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  29  */
  30
  31
  32 #ifndef CEPH_CYCLES_H
  33 #define CEPH_CYCLES_H
  34
  35 /**
  36  * This class provides static methods that read the fine-grain CPU
  37  * cycle counter and translate between cycle-level times and absolute
  38  * times.
  39  */
  40 class Cycles {
  41  public:
  42   static void init();
  43
  44   /**
  45    * Return the current value of the fine-grain CPU cycle counter
  46    * (accessed via the RDTSC instruction).
  47    */
  48   static __inline __attribute__((always_inline)) uint64_t rdtsc() {
  49 #if defined(__i386__)
  50     int64_t ret;
  51     __asm__ volatile ("rdtsc" : "=A" (ret) );
  52     return ret;
  53 #elif defined(__x86_64__) || defined(__amd64__)
  54     uint32_t lo, hi;
  55     __asm__ __volatile__("rdtsc" : "=a" (lo), "=d" (hi));
  56     return (((uint64_t)hi << 32) | lo);
  57 #elif defined(__aarch64__)
  58     //
  59     // arch/arm64/include/asm/arch_timer.h
  60     //
  61     // static inline u64 arch_counter_get_cntvct(void)
  62     // {
  63     //         u64 cval;
  64     //
  65     //         isb();
  66     //         asm volatile("mrs %0, cntvct_el0" : "=r" (cval));
  67     //
  68     //         return cval;
  69     // }
  70     //
  71     // https://github.com/cloudius-systems/osv/blob/master/arch/aarch64/arm-clock.cc
  72     uint64_t cntvct;
  73     asm volatile ("isb; mrs %0, cntvct_el0; isb; " : "=r" (cntvct) :: "memory");
  74     return cntvct;
  75 #elif defined(__powerpc__) || defined (__powerpc64__)
  76     // Based on:
  77     // https://github.com/randombit/botan/blob/net.randombit.botan/src/lib/entropy/hres_timer/hres_timer.cpp
  78     uint32_t lo = 0, hi = 0;
  79     asm volatile("mftbu %0; mftb %1" : "=r" (hi), "=r" (lo));
  80     return (((uint64_t)hi << 32) | lo);
  81 #else
  82 #warning No high-precision counter available for your OS/arch
  83     return 0;
  84 #endif
  85   }
  86
  87   static double per_second();
  88   static double to_seconds(uint64_t cycles, double cycles_per_sec = 0);
  89   static uint64_t from_seconds(double seconds, double cycles_per_sec = 0);
  90   static uint64_t to_microseconds(uint64_t cycles, double cycles_per_sec = 0);
  91   static uint64_t to_nanoseconds(uint64_t cycles, double cycles_per_sec = 0);
  92   static uint64_t from_nanoseconds(uint64_t ns, double cycles_per_sec = 0);
  93   static void sleep(uint64_t us);
  94
  95 private:
  96   Cycles();
  97
  98   /// Conversion factor between cycles and the seconds; computed by
  99   /// Cycles::init.
 100   static double cycles_per_sec;
 101
 102   /**
 103    * Returns the conversion factor between cycles in seconds, using
 104    * a mock value for testing when appropriate.
 105    */
 106   static __inline __attribute__((always_inline)) double get_cycles_per_sec() {
 107     return cycles_per_sec;
 108   }
 109 };
 110
 111 #endif  // CEPH_CYCLES_H