pdns/stat_t.hh

   1 /*
   2  * This file is part of PowerDNS or dnsdist.
   3  * Copyright -- PowerDNS.COM B.V. and its contributors
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of version 2 of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * In addition, for the avoidance of any doubt, permission is granted to
  10  * link this program with OpenSSL and to (re)distribute the binaries
  11  * produced as the result of such linking.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22 #pragma once
  23
  24 #include <atomic>
  25
  26 #ifndef DISABLE_FALSE_SHARING_PADDING
  27 #define CPU_LEVEL1_DCACHE_LINESIZE 64 // Until we know better via configure/getconf
  28
  29 namespace pdns {
  30   template <typename T>
  31   class stat_t_trait {
  32   public:
  33     using base_t = T;
  34     using atomic_t = std::atomic<base_t>;
  35
  36     stat_t_trait() : stat_t_trait(base_t(0)) {
  37     }
  38     stat_t_trait(const base_t value)
  39     {
  40       new(&counter) atomic_t(value);
  41     }
  42     stat_t_trait& operator=(const base_t& value) {
  43       ref().store(value);
  44       return *this;
  45     }
  46     ~stat_t_trait() {
  47       ref().~atomic_t();
  48     }
  49     stat_t_trait(stat_t_trait&&) = delete;
  50     stat_t_trait& operator=(const stat_t_trait&) = delete;
  51     stat_t_trait& operator=(stat_t_trait&&) = delete;
  52     stat_t_trait(const stat_t_trait&) = delete;
  53     base_t operator++(int) {
  54       return ref()++;
  55     }
  56     base_t operator++() {
  57       return ++(ref());
  58     }
  59     base_t operator--(int) {
  60       return ref()--;
  61     }
  62     base_t operator--() {
  63       return --(ref());
  64     }
  65     base_t operator+=(base_t arg) {
  66       return ref() += arg;
  67     }
  68     base_t operator-=(base_t arg) {
  69       return ref() -= arg;
  70     }
  71     base_t load() const {
  72       return ref().load();
  73     }
  74     void store(base_t value) {
  75       ref().store(value);
  76     }
  77     operator base_t() const {
  78       return ref().load();
  79     }
  80
  81   private:
  82     atomic_t& ref()  {
  83       return *reinterpret_cast<atomic_t *>(&counter); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
  84     }
  85     const atomic_t& ref() const {
  86       return *reinterpret_cast<const atomic_t *>(&counter); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
  87     }
  88     typename std::aligned_storage_t<sizeof(atomic_t), CPU_LEVEL1_DCACHE_LINESIZE> counter;
  89   };
  90
  91   using stat_t = stat_t_trait<uint64_t>;
  92   using stat32_t = stat_t_trait<uint32_t>;
  93   using stat16_t = stat_t_trait<uint16_t>;
  94 }
  95 #else
  96 namespace pdns {
  97   using stat_t = std::atomic<uint64_t>;
  98   using stat32_t = std::atomic<uint32_t>;
  99   using stat16_t = std::atomic<uint16_t>;
 100   template <class T>
 101   using stat_t_trait = std::atomic<T>;
 102 }
 103 #endif